Review Article Apoptosis and Molecular Targeting Therapy in …downloads.hindawi.com/journals/bmri/2014/150845.pdf · 2019-07-31 · Review Article Apoptosis and Molecular Targeting

Review ArticleApoptosis and Molecular Targeting Therapy in Cancer

Mohamed Hassan12 Hidemichi Watari2 Ali AbuAlmaaty1

Yusuke Ohba3 and Noriaki Sakuragi2

1 Biotechnology Program Department of Zoology Port Said University Faculty of Science Port Said 42521 Egypt2 Department of Obstetrics and Gynecology Graduate School of Medicine Hokkaido University Sapporo 060-8638 Japan3Department of Cell Physiology Graduate School of Medicine Hokkaido University Sapporo 060-8638 Japan

Correspondence should be addressed to Mohamed Hassan mohamedkamel24yahoocom

Received 4 February 2014 Accepted 11 May 2014 Published 12 June 2014

Academic Editor Elena Orlova

Copyright copy 2014 Mohamed Hassan et al This is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properlycited

Apoptosis is the programmed cell death which maintains the healthy survivaldeath balance in metazoan cells Defect in apoptosiscan cause cancer or autoimmunity while enhanced apoptosismay cause degenerative diseasesThe apoptotic signals contribute intosafeguarding the genomic integrity while defective apoptosis may promote carcinogenesis The apoptotic signals are complicatedand they are regulated at several levels The signals of carcinogenesis modulate the central control points of the apoptoticpathways including inhibitor of apoptosis (IAP) proteins and FLICE-inhibitory protein (c-FLIP) The tumor cells may use someof several molecular mechanisms to suppress apoptosis and acquire resistance to apoptotic agents for example by the expressionof antiapoptotic proteins such as Bcl-2 or by the downregulation or mutation of proapoptotic proteins such as BAX In this reviewwe provide the main regulatory molecules that govern the main basic mechanisms extrinsic and intrinsic of apoptosis in normalcells We discuss how carcinogenesis could be developed via defective apoptotic pathways or their convergence We listed somemolecules which could be targeted to stimulate apoptosis in different cancers Together we briefly discuss the development ofsome promising cancer treatment strategies which target apoptotic inhibitors including Bcl-2 family proteins IAPs and c-FLIP forapoptosis induction

1 Introduction

Apoptosis is a very tightly programmed cell death with dis-tinct biochemical and genetic pathways that play a critical rolein the development and homeostasis in normal tissues [1]It contributes to elimination of unnecessary and unwantedcells to maintain the healthy balance between cell survivaland cell death in metazoan [2 3] It is critical to animalsespecially long-lived mammals that must integrate multiplephysiological as well as pathological death signals Evidenceindicates that insufficient apoptosis can manifest as cancer orautoimmunity while accelerated cell death is evident in acuteand chronic degenerative diseases immunodeficiency andinfertility Under many stressful conditions like precancerouslesions activation of the DNA damage checkpoint pathwaycan serve to remove potentially harmful DNA-damaged cellsvia apoptosis induction to block carcinogenesis [4 5] Thus

the apoptotic signals help to safeguard the genomic integrity[3 6 7] while dysregulation of the apoptotic pathways maynot only promote tumorigenesis but also render the cancercell resistant to treatment Thus the evasion of apoptosis isa prominent hallmark of cancer [8] Cancer cells are in factharboring alterations that result in impaired apoptotic signal-ing which facilitates tumor development and metastasis [6ndash8]

Here we provide an overview of mechanisms by whichthe main regulatory molecules govern apoptosis in normalcells and describe models of apoptotic dysregulation basedon alterations in their function that facilitate the evasionof apoptosis in cancer cells We will also briefly discuss thedevelopment of some promising cancer treatment strategiesbased on targeting the apoptotic inhibitor to stimulate theapoptotic signals We will shed some light on this veryactive field of endeavor that witnessed many breakthroughs

Hindawi Publishing CorporationBioMed Research InternationalVolume 2014 Article ID 150845 23 pageshttpdxdoiorg1011552014150845

2 BioMed Research International

over the last few years Notably insights from proposedtargetmolecules have included different portions of the deathpathway depending on the type of cancer Applications ofmany of such targeted therapy in different cell types andsignals studied in them have emphasized selected controlpoints for each targeted therapy

2 Apoptosis Defect and Cancer

Defects in programmed cell death (apoptosis) mechanismsplay important roles in tumor pathogenesis allowing neo-plastic cells to survive over intended lifespans subverting theneed for exogenous survival factors and providing protectionfromoxidative stress and hypoxia as the tumormass expandsThat gives time for accumulation of genetic alterations thatderegulate cell proliferation interfere with differentiationpromote angiogenesis and increase invasiveness duringtumor progression [9] Apoptosis defects are now consideredan important complement of protooncogene activation asmany deregulated oncoproteins that drive cell division alsotrigger apoptosis (eg Myc E1a and Cyclin-D1) [10] Onthe other hand the noncancerous cells have a DNA repairmachinery Defects in DNA repair andor chromosome seg-regation normally trigger cell suicide as a defensemechanismfor eradicating genetically unstable cells and thus such suicidemechanismrsquos defects permit survival of genetically unstablecells providing opportunities for selection of progressivelyaggressive clones and may promote tumorigenesis [11]

There are varieties of molecular mechanisms that tumorcells use to suppress apoptosis Tumor cells can acquireresistance to apoptosis by the expression of antiapoptoticproteins such as Bcl-2 or by the downregulation or mutationof proapoptotic proteins such as BAX Since the expressionof both Bcl-2 and BAX is regulated by the p53 tumorsuppressor gene [12] some forms of human B-cell lymphomahave Bcl-2 overexpression That example represents the firstand strongest lines of evidence that failure of cell deathcontributes to cancer [13]

Apoptosis defects may allow epithelial cells to survivein a suspended state without attachment to extracellularmatrix which facilitate metastasis [14] They also promoteresistance to the immune system including many weaponsof cytolytic T cells (CTLs) and natural killer (NK) cells usedfor attacking tumors that depend on integrity of the apoptosismachinery [15] Cancer-associated defects in apoptosis playa role in treatment resistance with conventional therapieslike chemotherapy and radiotherapy increasing the thresholdfor cell death and thereby requiring higher doses for tumorkilling agents [16] Thus dysregulated or defective apoptosisregulation is a fundamental aspect of the tumor biologySuccessful eradication of cancer cells by nonsurgical means isultimately approached via induction of apoptosis Thereforeall the cancer drug designers try either to activate theinactivated apoptotic mechanism or rectify a defective oneHence all cytotoxic anticancer therapies currently in clinicaluse when they work induce apoptosis of malignant cellsHence deeper understanding of the molecular mechanismsof apoptosis and its defective status opens the gate for a newclass of targeted therapeutics

21 Induction of Apoptosis Apoptosis is caused by pro-teases known as ldquocaspasesrdquo which specifically target cysteineaspartyl [17 18] Upon receiving specific signals instructingthe cells to undergo apoptosis a number of distinctive changesoccur in the cell A family of proteins known as caspasesis typically activated in the early stages of apoptosis Theseproteins cleave key cellular components that are requiredfor normal cellular function including structural proteins inthe cytoskeleton and nuclear proteins such as DNA repairenzymes The caspases can also activate other degradativeenzymes such as DNases which begin to cleave the DNA inthe nucleus

During the apoptotic process apoptotic cells displaydistinctive morphology Typically the cell begins to shrinkfollowing the cleavage of lamins and actin filaments in thecytoskeleton The apoptotic breakdown of chromatin in thenucleus often leads to nuclear condensation andor a ldquohorse-shoerdquo like appearance Cells continue to shrink packagingthemselves into a form that allows for their removal bymacrophages These phagocytic cells are responsible forclearing the apoptotic cells from tissues in a clean and tidyfashion that avoids many of the problems associated withnecrotic cell death In order to promote their phagocytosisby macrophages apoptotic cells often undergo plasma mem-brane changes that trigger the macrophage response One ofsuch changes is the translocation of phosphatidylserine fromthe inside of the cell to the outer surface The end stagesof apoptosis are often characterised by the appearance ofmembrane blebs or blisters process and small vesicles calledapoptotic bodies

The real workers in apoptosis mechanism are caspasesCaspases family is composed of intracellular cysteine pro-teases (119899 = 11 in humans) which collaborate in proteolyticcascades These caspases activate themselves and each otherWithin these proteolytic cascades caspases can be posi-tioned as either upstream ldquoinitiatorsrdquo or downstream ldquoeffec-torsrdquo of apoptosis Several pathways for activating caspasesexist

First there are thirty members of the tumor necrosisfactor- (TNF-) family receptors eight contain a so-calleddeath domain (DD) in their cytosolic tail [19] Severalof these DD-containing TNF-family receptors use caspaseactivation as a signaling mechanism including TNFR1CD120a FasAPO1CD95 DR3Apo2Weasle DR4TrailR1DR5TrailR2 and DR6 Ligation of these receptors at thecell surface results in the recruitment of several intracellu-lar proteins including certain procaspases to the cytoso-lic domains of these receptors forming a ldquodeath-inducingsignaling complexrdquo (DISC) that triggers caspase activationconstituting the so-called ldquoextrinsicrdquo pathway for apoptosis[20] The caspase-8 and in some cases caspase-10 are thespecific caspases summoned to the DISC These caspasescontain so-called death effector domains (DEDs) in their N-terminal prodomains that bind to a corresponding DED inthe adaptor protein FADD thus linking them to the TNF-family death receptor complexes

Second is the intrinsic pathway in which mitochondriainduces apoptosis by releasing cytochrome-c (cyt-c) into thecytosol The released cytochrome c assembles a multiprotein

BioMed Research International 3

caspase-activating complex referred to as the ldquoapoptosomerdquo[21] The central component of the apoptosome is Apaf1 acaspase-activating protein that oligomerizes upon bindingcyt-c and then binds procaspase-9 via interaction with itscaspase recruitment domain (CARD) The intrinsic pathwayis activated by myriad stimuli including growth factordeprivation oxidants Ca2+ overload oncogene activationDNA-damaging agents and microtubule targeting drugsIn addition to cyt-c mitochondria also releases endonucle-ase G AIF (a death modulating flavor protein) and IAPantagonists SMAC (DIABLO) and OMI (HtrA2) Some ofthese molecules may promote caspase-independent (non-apoptotic) cell death [22 23]

A third pathway for apoptosis induction is specific toCTL and NK cells which spray apoptosis-inducing proteasegranzyme B (GraB) onto target cells GraB then piggybacksinto cells via mannose-6-phosphate receptors (IGFR2) andenters effective cellular compartments via perforin channels[24] GraB is a serine protease but similar to the caspases itcleaves substrates at Asp residues including several caspasesand some caspase substrates The fourth pathway is a caspaseactivation pathway This pathway is proposed to be linked toendoplasmic reticulum (ER)Golgi stress [17] howevermanymechanistic details are lacking Finally a nuclear pathway forapoptosis regulation was proposedThat pathway depends ondiscrete nuclear organelles called Pml oncogenic domains(PODs) or nuclear bodies (NBs) Ablation of the pml genein mice results in general resistance to apoptosis throughunknown mechanisms Several proteins that can promoteapoptosis have been localized to PODs including Daax Zipkinase and Par4 and defects in assembly of these nuclearstructures are documented in cancers [25] How PODs arelinked to caspase activation pathways is unknown Severalendogenous antagonists of the caspase-activation pathwayshave been discovered and examples of dysregulation of theirexpression or function in cancers have been obtained Theseapoptosis mediators help cells to decide successful apoptosisor unsuccessful one They sometimes act as targets for drugdiscovery with the idea that abrogating their cytoprotectivefunctions may restore apoptosis sensitivity to tumor cells

22 Resistance to Apoptosis in Cancer Cancer is an exam-ple where the normal mechanisms of cell cycle regulationare dysfunctional with either an over-proliferation of cellsandor decreased removal of cells [26] In fact suppressionof apoptosis during carcinogenesis is thought to play a centralrole in the development andprogression of some cancers [27]There is a variety of molecular mechanisms that tumor cellsuse to suppress apoptosis

23 Carcinogenesis via Intrinsic Signaling Defects Mitochon-dria-dependent apoptosis is one of the most importantpathways for apoptosis induction That is why disturbingthis pathway is an effective way to inhibit apoptosis Bcl-2family proteins (119899 = 24 in humans) are central regulatorsof the intrinsic pathway which either suppress or promotechanges in mitochondrial membrane permeability requiredfor release of cyt-c and other apoptogenic proteins [21 24]Antiapoptotic proteins (eg Bcl-2 Bcl-xL Bcl-W Mcl-1

and Bfl-1A1) which display sequence homology in all BH1-BH4 domains promote cell survival whereas proapoptoticproteins mediate receptor- mitochondria- or endoplasmicreticulum (ER) stress-dependent apoptosis The latter groupis subdivided into multidomain or BH3-only proteins Theformer consists of Bax and Bak which are essential for apop-tosis [28]The BH3-only proteins are further divided into twosubclasses ldquoactivatorsrdquo (eg Bim and tBid) which directlyactivate BaxBak to induce mitochondrial outer membranepermeabilization (MOMP) and ldquosensitizersderepressorsrdquo(eg Bad Bik Bmf Hrk Noxa and Puma) which do notactivate BaxBak directly but instead neutralize antiapoptoticproteins [29 30] The central role that BaxBak play inapoptosis is supported by evidence that BH3-only proteinsfail to trigger apoptosis in BaxBak-deficient cells [31 32]Antiapoptotic proteins block death signaling by antagonizingthe actions of BaxBak through partially knownmechanismsAs recently summarized antiapoptotic proteins preventBaxBak activation by sequesteringinhibiting ldquoactivatorrdquoBH3-only proteins andor directly inhibiting BaxBak activa-tion [33] ldquoSensitizerrdquo BH3-only proteins displace ldquoactivatorrdquoBH3-only proteins from antiapoptotic proteins leading toBaxBak activation Alternatively BH3-only proteins maydirectly neutralizeinhibit antiapoptotic proteins releasingtheir inhibition of BaxBak

Overexpression of antiapoptotic Bcl-2 or Bcl-xL probablyoccurs in more than half of all cancers [34] rendering tumorcells resistant to myriad apoptotic stimuli including mostcytotoxic anticancer drugs For example forced expressionof Bcl-2 protein from plasmid vectors in contrast abrogatessensitivity to the apoptosis promoting effects of antiestro-gens in breast cancer lines while antisense Bcl-2 preventsestrogen-mediated apoptosis suppression thus establishinga direct functional connection between ER and Bcl-2 andsuppression of apoptosis [35]

24 Carcinogenesis via Extrinsic Pathway Signaling DefectThe extrinsic pathway is activated in vivo by TNF familyligands that engage DD-containing receptors resulting inactivation of DED-containing caspases The ldquodeath ligandsrdquoare expressed on CTLs NK cells and other types of immune-relevant cells (activated monocytesmacrophages and den-dritic cells) and are used as weapons for eradication of trans-formed cells [19] Mice-based studies on genetic alterationsin genes encoding death ligands or their receptors as well asuse of neutralizing antibodies and Fc-fusion proteins haveprovided evidence of important roles in tumor suppression bycellular immune mechanisms Fas ligand (FasL) is importantfor CTL-mediated killing of some tumor targets and TRAIL(Apo2 ligand) is critical for NK-mediated tumor suppressionSome tumor cells resist the response of the death receptorpathway to FasL produced by T cells to evade immunedestructionMany tumor cell lines display intrinsic resistanceto TRAIL even though they express the necessary cell surfacereceptors confirming that during evolution of tumors in vivoselection occurs formalignant clones capable of withstandingimmune attack This could occur in a variety of waysincluding downregulation of the Fas receptor expression of


nonfunctioning Fas receptor and secretion of high levels of asoluble form of the Fas receptor That will directly sequesterthe Fas ligand or expression of Fas ligand on the surface oftumor cells (reviewed [36]) Some tumor cells are capable of aFas ligand-mediated ldquocounter attackrdquo that results in apoptoticdepletion of activated tumor infiltrating lymphocytes [37]Thus successful biological therapy depends on restoringcompetency of the extrinsic pathway

Another molecule is the c-FLIP cellular FADD-likeinterleukin-1beta-converting enzyme inhibitory proteinslong c-FLIP(L) which regulates caspase-8 activation Despitethe identified dual functionality of c-FLIPL as a pro- orantiapoptotic factor in normal tissues c-FLIPL has generallybeen shown to act as a key negative regulator of apoptosis inhuman cancer cells [38 39] Increased expression of c-FLIPhas been detected in many human malignancies includingmelanoma hepatocellular carcinoma [40] nonsmall celllung carcinoma [40] and endometrial [41] colon [42]and prostate cancer [43ndash45] While its overexpressionhas been associated with cancer progression andor poorprognosis in BL HCC and ovarian endometrial colonand prostate cancer [38 39 42 46] elevated expressionof c-FLIP blocks caspase-8 and renders cells resistant tocell receptor-mediated apoptosis [38] Overexpression ofc-FLIPL has been reported to bind proteins involved in thesesignaling pathways including TRAF1 TRAF2 RIP andRAF1 and thereby promotes the activation of NF-120581120573 andERK as downstream molecules [39]

In TRAIL-resistant nonsmall cell lung cancer (NSCLC)cells c-FLIP and RIP have been shown to be essential forTRAIL-induced formation of the DISC in nonraft domainsof the plasma membrane and consequent activation of NF-120581120573 and ERK cell survival signals In contrast knockdownof c-FLIP has been found to redistribute the DISC to lipidrafts and switch DISC signaling to TRAIL-induced apoptosis[47] NF-120581120573 constitutive activation has been linked to thepathogenesis of many human cancers [48] and inhibition ofNF-120581120573-induced transcription of c-FLIP has been shown tosensitize cells to death receptor-mediated apoptosis [49 50]NF-120581120573-mediated upregulation of c-FLIP is implicated as animportant factor in the evasion of cell death by cancer cells

25 Carcinogenesis via Convergence Pathway Inhibition Theintrinsic and extrinsic pathways for caspase activation con-verge on downstream effector caspases Mechanisms forsuppressing apoptosis at this distal step have been revealedand their relevance to cancer is becoming progressivelyclear In this regard the apoptosis-inhibiting proteins (IAPs)represent a family of evolutionarily conserved apoptosissuppressors (119899 = 8 in humans) many of which functionas endogenous inhibitors of caspases All members of thisfamily by definition contain at least one copy of a so-calledBIR (baculovirus iap repeat) domain a zinc binding foldwhich is important for their antiapoptotic activity present in1ndash3 copies Caspases-3 and -7 as well as caspase-9 (intrinsicpathway) are directly affected by the human IAP familymembers XIAP cIAP1 and cIAP2 For XIAP the secondBIR domain and the linker region between BIR1 and BIR2

are required for binding and suppressing caspases-3 and -7while the third BIR domain binds caspase-9 Thus differentdomains in the multi-BIR containing IAPs are responsiblefor suppression of different caspases IAP family memberLivin (ML-IAP) contains a single BIR and inhibits caspase-9 but not caspase-3 and -7 Survivin also contains a single BIRwhich associates with caspase-9

IAPs are overexpressed in many cancers while moredetailed information is needed about the exact deregulationof the 8 members of this gene family in specific types ofcancer Those IAPs elevations found in cancers are impor-tant for maintaining tumor cell survival and resistance tochemotherapy as confirmed by antisense-mediated reduc-tions experiments Targeting IAP-family members XIAPcIAP1 Survivin or Apollon can induce apoptosis in tumorcell lines in culture or sensitize cells to cytotoxic anticancerdrugs

Endogenous antagonists of IAPs keep these apoptosissuppressors in check promoting apoptosis Two of thesenaturally occurring IAP-antagonists SMAC (Diablo) andHtrA2 (Omi) are sequestered inside mitochondria becom-ing released into the cytosol during apoptosis [51] SMAC andHtrA2 have N-terminal leader sequences that are truncatedby proteolysis upon import into mitochondria exposing anovel tetrapeptide motif that binds the BIR domains of IAPsThese IAP antagonists compete with caspases for binding toIAPs thus freeing caspases from the grip of the IAPs andpromote apoptosis Thus some modern synthetic peptides-based therapeutics that mimic SMAC and HtrA2 triggerapoptosis or sensitize tumor cell lines to apoptosis inducedby cytotoxic anticancer drugs or TRAIL in vitro and even insome tumor xenograft models [52]

26 How the Cancer Cells Overcome the Therapeutic Agents-Induced Apoptosis The success of each therapeutic strategydepends mainly on the ability of the therapeutic tool toinduce apoptosis either by targeting the overexpressed anti-apoptotic proteins or by stimulating the expression of theproapoptotic molecules However many of the therapeuticagents are still challenged bymaneuvering(s) from the cancercells to survive treatments Alterations in the expression levelsor mutation of a chemotherapeutic drugrsquos target(s) may havean impact on apoptosis by such drug Here we list some ofthe mechanisms by which cancer cell can overcome three ofthe standard therapeutic agents

261 5-Fluorouracil (5-FU) The fluoropyrimidine 5-fluor-ouracil (5-FU) is widely used in cancer treatment includ-ing colorectal and breast cancer treatments [53 54] butresistance to that drug remains a major clinical obstacle 5-is part of its antitumor activity and FU targets the tumorsuppressor p53 and subsequently triggers the cell cycle 5-FU-induced apoptosis is p53-dependent however apoptosiscan also occur in p53 mutant cell lines by a mechanismstill unknown [55ndash57] 5-FU is an analogue of uracil with afluorine atom at theC5 position of the pyrimidine ring Insidecells 5-FU is converted into different active metabolitesincluding fluorodeoxyuridine monophosphate (FdUMP)


fluorodeoxyuridine triphosphate (FdUTP) and fluorouri-dine triphosphate (FUTP) These metabolites have beenimplicated in both global RNA metabolism due to the incor-poration of the ribonucleotide FUMP into RNA and DNAmetabolism due to thymidylate synthase (TS) inhibition ordirect incorporation of FdUMP into DNA leading to a widerange of biological effects which trigger apoptotic cell deathThe inhibition of TS is believed to be the primary anticanceractivity of 5-FU [58 59] however 5-FU has been shown toacutely induce TS expression in both cell lines and tumors[60] This induction of TS seems to be due to inhibitionof a negative feedback mechanism in which ligand-free TSbinds to its own mRNA and inhibits its own translation[61] When stably bound by FdUMP TS can no longerbind its own mRNA and suppress translation resulting inincreased protein expression This constitutes a potentiallyimportant apoptosis resistancemechanism as acute increasesin TS would facilitate recovery of enzyme activity Thus TSexpression acted as a key determinant of 5-FU sensitivity[62] while in vitro studies have validated the associationbetween TS expression and apoptosis 5-FU [63 64] whilethe improved response rates of 5-FU-based chemotherapywere observed in patients with low tumour TS expression[65 66] Recently genotyping studies have found that patientshomozygous for a particular polymorphism in the TS pro-moter (TSER3TSER3) that increases TS expression are lesslikely to respond to 5-FU-based chemotherapy than patientswho are heterozygous (TSER2TSER3) or homozygous forthe alternative polymorphism (TSER2TSER2) [67] Col-lectively many evidences indicate that high TS expressioncorrelates with increased 5-FU resistance

262 Antimicrotubule Agents (AMA) Microtubules arehighly dynamic cytoskeletal fibres composed of tubulin sub-units (most commonly 120572- and 120573-tubulin) that have crucialroles in maintaining cell shape in cell signalling in cell divi-sion and mitosis and in the transport of vesicles and mito-chondria and other cellular components throughout the cell[68] The rapid polymerizationdepolymerization dynamicsof microtubules are critical for proper spindle function andaccurate chromosome segregation during mitosis

Taxanes such as paclitaxel and docetaxel and vincaalkaloids such as vinblastine and vincristine suppressmicro-tubule polymerization dynamics which results in the slowingor blocking of mitosis at the metaphase-anaphase boundary[69] These compounds can block or slow mitosis and sub-sequently cells eventually die by apoptosis [70] Microtubulepolymer levels and dynamics are regulated by many factorsincluding expression of different tubulin isotypes [71] Cellscan resist paclitaxel and vinca alkaloids by changing themicrotubules dynamics and levels of tubulin isotypes [72ndash74]Sometimes a reduction in total intracellular tubulin levelscould be observed in paclitaxel-resistant cells Thereforethe development of resistance to antimicrotubule agentsmay involve changes in the microtubule polymer mass andexpression of different tubulin isotypes Furthermore specific120573-tubulin mutations that alter sensitivity to paclitaxel havebeen reported in vitro [75ndash77]The clinical relevance of these

mechanisms of resistance to antimicrotubule agents remainsto be determined

263 Cisplatin The therapeutic activity of cisplatin and car-boplatin is mediated by an active species formed by aqueoushydrolysis as the drug enters the cell This active speciesinteracts with DNA RNA and protein but the cytotoxiceffect seems to be primarily mediated via the formation ofDNA interstrand and intrastrand crosslinksThese platinum-DNA adducts are recognized by a number of proteinsincluding those involved in nucleotide excision repair (NER)mismatch repair (MMR) and high-mobility group proteins(such as HMG1 and HMG2) [78] Platinum-induced DNAdamage is normally repaired by the NER pathway whereasthe MMR pathway seems to trigger apoptosis [79 80] Themechanism bywhich damage recognition results in apoptosisis unclear however in vitro data support a role for cisplatin-mediated activation of the c-ABL and JNKSAPK pathway inapoptotic signalling inMMR-proficient cells [81] In additionthe induction of p53 possibly by the ATM-CHK2 pathwaysfollowing DNA strand breaks leads to apoptosis via theintrinsic pathway and also contributes to the cytotoxicity ofcisplatin [82]

Bcl-2 members are localized in the mitochondria andhave either proapoptotic (Bax Bak Bid and Bim) or anti-apoptotic (Bcl-2 Bcl-xL and Bcl-W) functions [8 83 84]These members are involved in the downstream action bycisplatin These proteins form either homodimers (such asBcl-2Bcl-2) or heterodimers (eg Bcl-2Bax) dependingon the levels present of each component Excess level ofhomodimers can either inhibit (eg Bcl-2Bcl-2) or induce(eg BaxBax) apoptosis Although it is not confirmedwhether cisplatin can directly modulate levels of the anti-apoptotic protein or not there is evidence that cisplatinsignificantly transactivates the bax gene by wild-type p53Thus an increase in the Bax to Bcl-2 ratio by cisplatin-induced p53 has been reported to activate the apoptoticprocess [85] However extrapolating experimental resultsto the clinic results needs much caution for instance thedemonstration that experimental overexpression of bcl-2 intumors leads to the expected cisplatin resistance [86ndash88]That was opposite to a clinical study which reported thatcisplatin surprisingly improved survival of ovarian cancerpatients with increased bcl-2 gene expression [87] Now it isunderstood that proapoptotic homodimers affect cisplatin-induced apoptosis by first stimulating the mitochondria torelease cytochrome c which in turn activates a series ofproteases that includes caspase-1 -3 and -9 [84 89ndash91] whichare the final effectors of drug mediated apoptosis

3 Molecular TargetingTherapies and Apoptosis

Expression of inhibitors of apoptosis as well as inactivationof apoptosis promoters is observed in human cancers [92]Moreover functional defects in apoptotic signal transductionmay translate into drug resistance of cancer [86 93] Overthe past decade significant advances have been made in


discovery and validation of several types of novel cancertherapeutics Such novel therapeutics tries to prime theapoptotic machinery to act as promising apoptosis-inducingagents bearing high hopes for the management of cancersresistant to conventional treatments [94] This therapeuticscan be used either alone or in combination with some of theconventional therapies Several review articles have shed lightto the great potential of apoptosis-targeted therapies [95 96]Some of which focus on Bcl-2 family proteins [97ndash99] IAPs[100] or c-FLIP [101] and the approaches that have beenused to modify their activity to reactivate apoptosis and thuseradicate cancer cells

As below we refer readers to these reviews for specificdetails regarding the benefits of some novel therapeuticagents directed against some antiapoptotic targets whichhave been shown to demonstrate enhanced apoptotic killingand sensitize resistant cancer cells to antineoplastic agentsNevertheless we show below a few of the most promisingtherapeutic strategies which target the induction of apoptosis

31 Targeting Antiapoptotic Bcl-2 Family Members The com-plex interplay between proapoptotic and antiapoptotic mem-bers of the Bcl-2 family plays a crucial role in cellularfate determination Attempts to overcome the cytoprotectiveeffects of Bcl-2 and Bcl-xL in cancer include three strategies(1) shutting off gene transcription (2) inducing mRNAdegradation with antisense oligonucleotides and (3) directlyattacking the proteins with small-molecule drugs Hereinwe will provide some of the most promising strategies formodulating the activity of apoptosis genes and their proteinsfor cancer therapy

Some members of the steroidretinoid superfamily ofligand-activated transcription factors (SRTFs) representpotentially ldquodrugablerdquo modulators of Bcl-2 and Bcl-xL genetranscription although they are not components of the ldquocorerdquoapoptosis machinery For example expression of Bcl-2 isestrogen-dependent in the mammary gland Consequentlyantiestrogens such as tamoxifen inhibit endogenous Bcl-2expression in breast cancer cell lines promoting sensitivity tocytotoxic anticancer drugs such as doxorubicin In additionto antiestrogens in estrogen receptor- (ER-) positive breastcancers expression of Bcl-2 or Bcl-xL can be downregulatedin specific types of cancer and leukemia cells by smallmolecule drugs that modulate the activity of retinoic acidreceptors (RAR) retinoid X receptors (RXR) PPAR vitaminD receptors (VDR) and certain other members of the SRTFsuperfamily RAR and RXR ligands are already approved fortreatment of some types of leukemia and lymphoma and arein advanced clinical testing for solid tumors PPAR mod-ulators have demonstrated antitumor activity in xenograftmodels of breast and prostate cancer [10] sometimes dis-playing synergy with retinoids probably due in part tothe fact that PPAR binds DNA as a heterodimer with RXRMoreover troglitazone a potent PPAR agonist can lowerserum PSA in men with advanced prostate cancer howeverits proapoptotic features are not confirmed in vivo yet

Compounds that inhibit histone deactylases (HDACs)called HDAC inhibitors act as transcriptional repressors by

interacting with retinoid receptors and other transcriptionfactors These inhibitors can modulate expression of Bcl-2or Bcl-xL in some tumor lines [51] These observations por-tend opportunities for exploiting endogenous transcriptionalpathways for suppressing expression of antiapoptotic Bcl-2-family genes in cancer together with the idea of employingthem as chemo- or radiosensitizers rather than relying ontheir antitumor activity as single agents The genetic char-acteristics of cancer cells that dictate response or resistanceto SRTF-ligands as well as the complex pharmacologicalinterplay between this class of agents and conventionalcytotoxic drugs need to be investigated more

Because Bcl-2 antisense enhances sensitivity to cytotoxicanticancer drugs in vitro and in xenograft models mostclinical trials combine the antisense agent with conventionalchemotherapy More precisely antisense oligonucleotidestargeting the Bcl-2 mRNA have been introduced to Phase IIIclinical trials for melanoma myeloma CLL and AML andPhase II activity underway for a variety of solid tumors [102]Moreover Phase II data suggest a benefit from adding Bcl-2antisense to conventional therapy but definitive proof awaitsthe Phase III results

Beside the antisense oligodeoxynucleutides (eg G3139[103]) various drugs molecules that target Bcl-2 and Mcl-1 have been tested for their abilities to induce apoptosisin cancer cells [104] Understanding how cells keep theseantiapoptotic proteins controlled is the base on which thetherapeutic potency for targeting the Bcl-2 and Bcl-xL pro-teins by these molecules is established In this regard a largefamily of endogenous antagonists of Bcl-2 and Bcl-xL hasbeen revealed (so-called ldquoBH3-only proteinsrdquo) possessing aconserved BH3 domain that binds a hydrophobic creviceon the surface of Bcl-2 and Bcl-xL [100] Synthetic BH3peptides generated as small-molecule drugs that occupythe BH3 binding site on Bcl-2 or Bcl-xL abrogating theircytoprotective functions have been validated [105] Manyresearch groups have presented preclinical data regardingBH3-mimicking compounds The optimal structure-activityrelation (SAR) profile of these compounds had been deter-mined These molecules showed broad-spectrum activityagainst the various antiapoptotic members of the Bcl-2-family (Bcl-2 Bcl-xLMcl-1 Bcl-W Bfl-1 and Bcl-B) in termsof balancing antitumor efficacy Of these molecules whichtarget Bcl-2 are the small molecule Bcl-2 inhibitors (egHA14-1 [103]) and BH3 peptidomimetics [106] The mostprominent molecules among them are the Bcl-2 antagonistsABT-737 and ABT-263 [107 108] That novel Bcl-2Bcl-xLBcl-W inhibitor (ABT-737) has been developed It showedenhanced activity of chemotherapeutic agents or ionizingradiation in the preclinical studies That compound displaysimpressive antitumor activity in human tumors includingfollicular lymphoma chronic lymphocytic leukemia andsmall cell lung cancer (SCLC) in vitro and in vivo [107] andin nonsmall lung cancer (NSCLC) [109]

ABT specifically bind to Bcl-2 Bcl-xL and Bcl-Wflippingthem from Bak and Bax ABT-737 mimics the BH3-onlyprotein Bad by docking to the hydrophobic groove ofantiapoptotic proteins thereby disabling their capacity toantagonize the actions of proapoptotic proteins Therefore


ABT-737 is highly potent (ie at nanomolar concentrations)in killing tumor cells which are dependent upon Bcl-2 forsurvival [110] Although ABT targets almost all the proapop-totic family members of Bcl-2 except Mcl-1 it has beenfound that its combination with deoxyglucose has efficientlyeliminated cancer cells in vitro and in vivo [111] ABT-737was modified at three sites to create improved ABT-263 fororal bioavailability without the loss of affinity to the Bcl-2family of proteins [108] As a single agent however ABT-263737 (ABT) induces apoptosis only in limited tumor typessuch as lymphomas and some small cell lung carcinomas[107 108 112]

Other strategies for countering Bcl-2 andBcl-xL in cancerinclude over-expression of opposing proapoptotic familymembers such as Baxwith p53 adenovirus (in Phase III trials)or with Mda7 (IL-24) adenovirus gene therapy (completedPhase I trials) as well as Bax adenovirus gene therapy forregional cancer control Alternatively it might be possible toactivate the Bax and Bak proteins using drugs that mimicagonistic BH3 peptides [105]

One further strategy to counteract Bcl-2 family membersis the monoclonal antibodies which target the tetra-spanmembrane protein CD20 (Rituximab) but can also down-regulate expression of Bcl-2 family members Mcl-1 (intrin-sic pathway) and XIAP (convergence pathway) in certainleukemias providing yet another example of unexpectedlinks to apoptosis pathways through receptor-mediated sig-naling [113]

32 Targeting Cell Cycle Control System for Apoptosis Induc-tion The relationship between cell cycle arrest and apoptosisis complex Signaling pathways following apoptosis-inducingstimuli either arrest the cell cycle following damage signals toallow time for repair or switch to initiation of apoptosis afterapoptogenic agents These agents such as ionizing radiationor some chemotherapy induce apoptosis in many cell types[114] Apoptosis is frequently associated with proliferatingcells This implies the existence of molecules in late G1and S phase whose activities facilitate execution of theapoptotic process Once the cells are committed to cell deathapoptogenic factors including cytochrome c are releasedfrom mitochondria to initiate a caspase cascade [115]

An important cell cycle regulator plays a central role inthe regulation of cell cycle arrest and cell death is the tumorsuppressor p53 [116] It has recently been discovered that thep53 activates apoptosis through parallel pathways that maydepend on transcription events or not [117] Under manytypes of stress p53 induces cell cycle arrest and apoptosis tomaintain genomic integrity and prevent damagedDNAbeingpassed on to daughter cells Tumor cells have inactivated p53About 50 of this inactivation is achieved throughmutationsin its sequence and the rest by disabling key componentsthat lie upstream or downstream of p53 in a commonsignaling pathway [118] In p53 wild-type tumors p53 maybe compromised by inactivation of positive regulators of p53activity (such as p14ARF [119]) or over-activation of negativeregulators of p53 activity (such as Akt [120])

Bax is one of the best known downstream p53 tran-scriptional targets that directly affect apoptosis A further

transcription-independent role of p53 in apoptosis has beenattributed to its ability to block the antiapoptotic functionof Bcl-2 and Bcl-xL on the mitochondria [121 122] p53promotes directly or indirectly the apoptotic activities ofproapoptotic members of the Bcl-2 family Bax and Bak[121 123] Moreover after targeting DNA by some damagingagents p53 contribute as a transcription factor p53 transcrip-tionally upregulates genes such as those encoding p21WAF-1CIP-1 and GADD45 which induce cell cycle arrest inresponse to DNAdamage [124 125] However p53 can triggerelimination of the damaged cells by promoting apoptosisthrough the upregulation of proapoptotic genes such as BaxNOXA TRAIL-R2 (DR5) and Fas (CD95Apo-1) [12 55 126127] However the cell can choose between p53-dependentcell cycle arrest or apoptosis How cells choose betweenthis p53-mediated cell cycle arrest and apoptosis has threepossible models (I) One model suggests that more profoundDNA damage induces higher and prolonged activation ofp53 which increases the chances of apoptosis over arrest[128] (II) Another model suggests that different cell typesmight keep different p53-regulated genes in regions of activechromatin which determines the cassette of genes thatare transcriptionally upregulated [129] (III) A third modelproposes that the availability of transcriptional cofactorsdetermines the ability of p53 to activate different subsets ofgenes [130 131]

DNA damage-inducing apoptotic factors induce theactivation of upstream kinases such as ATM (ataxia-telangiectasia mutated) ATR (ATM and Rad-3 related)and DNA-PK (DNA-dependent protein kinase) which candirectly or indirectly activate p53 Phosphorylation of p53 byupstream kinases inhibits its negative regulation by MDM-2 which targets p53 for ubiquitin-mediated degradation[132] In fact lack of functional p53 contributes to apoptosisresistance due to the inability to undergo p53-mediatedapoptosis sometimes due to p53 mutations In vitro studieshave reported that loss of p53 function reduces apoptosisby 5-FU [57] Other clinical studies have found that p53overexpression (a surrogate marker for p53 mutation) corre-lates with resistance to apoptosis by 5-FU [133 134] Otherstudies have found no such correlation [135] Such conflictingfindings may be due at least in part to the fact that p53overexpression does not actually reflect p53 mutation in asmany as 30ndash40 of cases [136] A recent study has suggestedthat certain p53 mutants may increase dUTPase expressioninhibiting apoptosis by 5-FU [137]

Anumber of in vitro studies have demonstrated decreasedcisplatin-induced apoptosis in p53 mutant tumor cells [138ndash140] Some studies have reported that disruption of p53 func-tion actually enhances apoptosis by cisplatin [141 142] Thisenhanced apoptosis was attributed to defects in p53-mediatedcell cycle arrest which reduced time for DNA repair Sometumors withmutant p53 have a worse clinical outcome whichmeans failure to induce apoptosis by therapeutic drugs [143]In vitro data from other laboratories and others suggest thatdevelopment of resistance to apoptosis by taxan is feasiblein p53 null cells [144] The clinical relevance of p53 statusfor taxan-induced is yet to be determined In vitro studieshave found that p53 status does not affect paclitaxel-induced


apoptosis [145ndash147] On the other hand doxorubicin wasmore active against p53 wild-type tumor xenografts thanp53 mutant and null cells [148] Furthermore apoptosisinduction by doxorubicin in acute lymphoblastic leukaemiacell lines was found to be dependent on the presence ofwild-type p53 [149] In the clinical setting p53 mutationshave been correlated with lack of response to doxorubicinin patients with locally advanced breast cancer [150] Thesedata indicate that doxorubicin ismore active against p53wild-type tumors Fichtner et al found no correlation betweenp53 status and sensitivity to the apoptogenic carboplatinin xenotransplanted colorectal tumors [151] Similarly Jacobet al found that p53 status did not correlate with CPT-11-induced apoptosis in a panel of colorectal cancer celllines [152 153] Some studies have found that carboplatininduces apoptosis to a similar extent in isogenic p53 wild-type and null cancer cells [118] In general all the abovementioned studies suggest that p53 mutant tumors may beequally responsive to apoptosis inducers or possibly moresensitive than p53 wild-type tumors That led to applicationof combinatorial drug therapy of paclitaxel and cisplatin formaximum apoptosis induction in p53mutant ovarian tumorsthan p53 wild-type tumors as introduced [154]

321 Cyclines Another important family critically control-ling cell cycle is cyclines [155 156] Here we will focus onan important member of this family cyclin E which hasdirect relation with apoptosis signals Cyclin E has beenshown to have a Cdk2-independent function in regulatingapoptosis of hematopoietic cells [157 158] The larger N-terminal truncation of cyclin E that generates p18-cyclinE prevents its binding to either Cdk2 or CKIs p21Waf1or p27Kip1 Therefore unlike the other isoforms of cyclinE p18-cyclin E cannot bind Cdk2 and therefore interfereswith Cdk2-dependent (bound to cyclin E1 E2 or A) kinaseactivity Cleavage of cyclin E results in loss of its Cdk2associated kinase activity and consequently its function inthe cell cycle [157] Recently it has been reported that p18-cyclin E mediates p53 function-independent apoptosis byregulating the relationship between Bax and Ku70 [159]Thatstudyrsquos findings established a role for Ku70 in regulating Bax-mediated apoptosis in hematopoietic cells that generate p18-cyclin E By interacting with Ku70 p18-cyclin E releases BaxfromKu70 thus allowing Bax to be activated during gentoxicstress and thereby leading to apoptosis [159] Thereforep18-cyclin E Bax and Ku70 emerge as key regulators ofthe apoptotic pathway at least in hematopoietic cells Thesensitivity of these cells to genotoxic stress can be explainedby their ability to generate p18-cyclin E

The cleavage of cyclin E can be prevented by Bcl-2overexpression indicating that Bcl-2 functions upstream ofthe mitochondrial apoptotic cascade [115 158] How Bax isreleased from its complex with Ku70 is still unknown Onemechanism may consist of a structural change in conforma-tion of the Bax binding-domain of Ku70 upon binding of p18-cyclin E at the amino terminus Another possibility might bethe recruitment of histone acetyl transferases which wouldacetylate several lysine residues at the carboxy terminus ofKu70 [160] However it is quite possible that other pathways

and various feedback loops exist to activate Bax and therebyto amplify the apoptotic cascade in hematopoietic and othercell types

It is now clear that through its dual role cyclin E providesa physiological balance between cell proliferation and deathof hematopoietic cells [161] Cyclin E has an initial limitedactivation of caspase-3 perhaps through a small amountof primedactivated mitochondrial Bax Then cyclin E isproteolytically cleaved by caspase-3 to generate p18-cyclin Ewhich interacts with Ku70 resulting in release of Bax from theKu70-Bax complex This contributes to a robust activation ofBax leading to its mitochondrial targeting and amplificationof the intrinsic pathway of apoptosis This is consistent withthe idea that limited caspase activation is not sufficient torelease enough cytochrome c leading to significant apoptosisat least in hematopoietic cells Rather an amplification loopis required to trigger massive cytochrome c release frommitochondria resulting in abundant caspase-3 activation andcell death [115] Caspase-3 and caspase-7 may participate ina feedback amplification loop to promote the mitochondrialapoptotic pathway [162]

322 Ku70 from Cyclin E to Bax As we previously men-tioned the key regulatory step in the intrinsic cell deathpathway is the activation of the proapoptotic molecule Bax[163] Although the mechanism of Bax activation remainsunclear a recent study indicates that Bax is kept inactivein some cells to counteract apoptosis by interacting withcytosolic Ku70 [163 164] Overexpression of Ku70 preventsBax-mediated apoptosis whereas targeting Ku70 causes cellsto become more sensitive to a variety of apoptotic stim-uli Importantly we showed that some of these apoptoticstimuli which are not directly targeting DNA break like themicrotubule stabilizing agents Taxane and hyperthermiastimulated caspase-dependent apoptosis after Ku70 inhibi-tion (unpublished data) These results demonstrated thatKu70 is a physiological inhibitor of Bax-induced apoptosisa finding that expands on Ku70rsquos previously known rolein DNA repair [163] particularly through nonhomologousend joining (NHEJ) Moreover cells from Ku70 knockoutmice are hypersensitive to agents that induce apoptosis inthe absence of DNA damage such as staurosporine [159]This suggests that Ku70 plays a role in suppressing apoptosisindependently of its role in DNA repair [165] Based onthese findings nuclear Ku70 is therefore considered to bemainly responsible for repair of DNA damage whereasthe cytosolic pool of Ku70 may be primarily a regulatorof Bax activation [162 164] Therefore Ku70 plays a dualrole in NHEJ and regulation of Bax which in turn maydetermine the balance between cell survival and programmedcell death in hematopoietic cells Ku70 may not be uniquein assuring Bax sequestration in the cytosol Other Baxinteractive proteins such as the peptide humanin [166] theapoptosis repressor with caspase recruitment domain (ARC)[167] or crystalline [168]may also function in various cellularsystems to sequester Bax On the other hand after apoptoticstimulation other Bax-interacting proteins such as p53 [169]and Bif- [170] and apoptosis-associated speck-like protein


(ASC) [171] and MOAP-1 [172] promote Bax conformationalchange and mitochondrial translocation

323 Nonapoptotic Function of Caspases Although caspasesare classically known for their role in apoptosis theirinvolvement in biological processes apart from cell death hasrecently received increased attention For example they playan important role in the inflammatory signaling pathways[173 174] The nonapoptotic functions of these proteasessuggest that they may become activated independently of theapoptotic cascade thus leading to the cleavage of specificsubstrates such as kinases cytokines transcription factorsand polymerases

Functional analysis of conditional caspase-deficient miceor derived cells confirmed the crucial roles of caspases in cellproliferation differentiation and inflammation It has beenreported recently that caspase-3 is a negative regulator of B-cell cycling This study shows that while the apoptotic path-way is largely unaffected in caspase-3 knockout mice splenicB-cell proliferation is enhanced in vivo and in response tomitogenic stimulation in vitro hyperproliferation is seenGenetic and biochemical data demonstrate that caspase-3is essential for the regulation of B-cell homeostasis [175]In contrast to caspase-3 caspase-8 is a positive regulator ofcell cycling as B-cell proliferation since caspase-8 deficientmice fail to proliferate [176 177] Recently it has beensuggested that caspase-3 and caspase-7 together play a role indevelopment since double knockout mice exhibit defects inheart development leading to death immediately after birthIn contrast knockout of either caspase individually on thesame genetic background resulted in viable animals

33 Targeting DNA Repair System for Apoptosis InductionDNA repair can determine fate of a cell with or withouttreatment stress which either resists over to survive orrespond to toxic agents When the repair mechanisms areunsuccessful it may cause cellular senescence (permanentcell cycle arrest) oncogenesis or apoptosis which plays anessential role in survival of the organisms by preventing themultiplication of mutated chromosomes as well as elimina-tion of indisposed cells normal embryonic development andmaintenance of cell homeostasis [178] In cancer treatmentsapoptosis-inducing chemotherapeutic drugs induce DNAdamage either directly (eg platinum drugs) or indirectly(eg 5-FU and topoisomerase poisons) The response toDNA damage is either repair or cell death Only whenrepair is incomplete for example when the DNA damageis too extensive cells will undergo apoptosis Herein wedescribe some major mechanisms through which cells canovercome apoptosis by damaging agents and we introducesome example molecules which had successfully targeted insome types of cancer to stimulate or enhance apoptosis bytherapeutic agents

Nucleotide excision repair (NER) is themajor pathway forDNA repair after DNA stress However for example cisplatininduces platinum-DNA adduct which could be removedby NER as challenge mechanism by cancer cell to repairof platinum-induced DNA damage [178] Defects in NER

result in hypersensitivity to cisplatin and that restorationof NER activity reduces sensitivity to more normal levels[179] NER is a complex process involving at least 17 differentproteins however upregulation of only a few rate limitingcomponents of theNER system is necessary to increase a cellrsquoscapacity for NER [180] One of these important rate-limitingfactors is the excision repair cross-complementing 1 protein(ERCC1) which plays a crucial role in response to apoptosisinducer cisplatin Increased expression of ERCC1 associatedwith cisplatin resistance [181ndash183] Clinically high levels ofERCC1 are correlated with poor response to platinum-basedchemotherapy in ovarian gastric and nonsmall cell lungcancers (NSCLC) [184ndash186] In addition highmRNA expres-sion of ERCC1 and thymidin synthase (TS) has been actingas predictors for poor response to combined oxaliplatin5-FU treatment of advanced colorectal cancer [187] TargetingERCC1 expression using an antisense expression constructmade ovarian cancer more sensitive to cisplatin than controlsin cell line and xenograft models [188] Another centralcomponent of the NERmachinery xeroderma pigmentosumgroup A (XPA) has been found to be overexpressed inapoptosis resistant cancer cells under apoptosis inducercisplatin treatment [184] Collectively these studies suggestan important role for NER in mediating resistance to DNAdamage and subsequent apoptosis by platinum

Another DNA damaging agent is 5-FU 5-FU treatmentinduces TS inhibition which subsequently causes nucleotideimbalances that severely disrupt DNA synthesis and repair[189] TS inhibition results in the accumulation of deoxyuri-dine triphosphate (dUTP) as the essential conversion processof deoxyuridine monophosphate (dUMP) to deoxythymi-dine monophosphate (dTMP) is blocked [190] Both dUTPand another 5-FU metabolite fluorodeoxyuridine triphos-phate (FdUTP) can be misincorporated into DNA Repair ofuracil and 5-FU-containing DNA could be achieved by thebase excision repair enzyme uracil-DNA-glycosylase (UDG)[191] However this repairmechanism is futile in the presenceof high (F)dUTPdTTP ratios causing false nucleotide incor-poration These futile cycles of misincorporation excisionand repair eventually lead to DNA strand breaks Howeversome cells show resistance to this mechanism by increaseddUTPase The increased dUTPase expression has been asso-ciated with resistance to TS inhibitors like 5-FU [192ndash194]

Anothermechanism is theDNAmismatch repair (MMR)which is an important mechanism that controls the decisionfrom survival to apoptosis The main function of the MMRsystem is to scan newly synthesized DNA and remove singlenucleotide mismatches that arise during replication MMRdeficiency is implicated in the development of apoptosis-resistance against wide range of DNA-damaging agentsincluding platinum drugs [195] It is possible that MMRrecognition of DNA damage may trigger an apoptotic path-way or that futile cycles of DNA damagerepair mediatedby the mismatch repair machinery generate lethal DNAstrand breaks [196] MMR has a role beyond that of repairin response to DNA damage Inherited defects in the DNAMMR genes especially hMLH1 and hMSH2 are commonin certain familial forms of cancer such as hereditary non-polyposis colon cancer (HNPCC) Such defects were also


observed in a variety of sporadic tumors including colorectalbreast and ovarian cancers [197ndash200] DNAMMRdeficiencygives rise to the microsatellite instability (MSI) phenotypewhich is detected as variations in lengths of DNA repeatsequences present in the genome [201] Cisplatin-inducedapoptosis and acquisition of the drug resistancewere found tobe associated with hypermethylation of the hMLH1 promoter[202] One clinical study found that ovarian tumors that wereinitially microsatellite stable before cisplatin-based stressexhibitedMSI in the residual tumors after chemotherapy andthat was proposed to be due to loss of hMLH1 expression[203] Hence preclinical studies strongly implicate loss ofMMR in particular loss of hMLH1 in overcoming apoptosisby cisplatin Reversal of hMLH1 promoter methylation byDNA methyl transferase inhibitor 2-deoxy-5-azacytidine(DAC) has been shown to resensitize cells to a range ofapoptotic agents including platinum drugs [202] ThusDAC has now entered clinical trials in combination withcarboplatin in some cancers Finally a clinical study foundthat MMR deficiency was a predictive factor for apoptosisinduction by carboplatin in advanced colorectal cancer [204]however MMR deficiency had no effect on sensitivity to thenon-DNA-targeted apoptosis-inducing agents paclitaxel anddocetaxel

In addition to the above mentioned repair mechanismsand other several repair machineries such as mutagenicrepair which may become effective for the recovery ofgenome against constant attack of numerous genotoxinsUV-radiation ionizing radiation and various chemicals areresponsible for most of the mutagenesis due to a processof translesion that inserts an incorrect nucleotide oppositeto the lesion and then continues elongation [205] Targetingany of such mechanisms could enhance apoptosis instead ofthe repair and eradicate the defectively repaired cells underapoptotic inducers

331 DNA Double Strand Break Repair and ApoptosisDouble-strand breaks (DSBs) repair mechanism is one ofthe widespreadmechanisms which efficiently repairs double-strand breaks and single-strand gaps in damaged DNAby a series of complex biochemical reactions as a resultof ionizing radiation UVR ROS and chemotherapeuticgenotoxic chemicals [205]The lethal effects of double strandbreaks (DSBs) can be conquered by the existence of twoindependent pathways such as homologous recombination(HR) and nonhomologous end joining (NHEJ) Multipleproteins are required for DSB repair by recombination whichare conserved among all eukaryotes Deficiencies in suchrepair mechanism can develop cancer

332 BRCA1 BRCA1 is a tumor suppressor gene that regu-lates cellular responses to DNA stress by apoptotic inducersGermline mutations of the BRCA1 gene account for about10 of breast and ovarian cancer cases and lower than nor-mal BRCA1 expression may be an important factor that con-tributes into sporadic cancers [206 207] Recently BRCA1has been found to reside in a large DNA repair complex thatincludes various mismatch repair proteins including hMLH1

and hMSH2 thus it plays a role in DNA repair [208] BRCA1also plays a role in the activation of cell cycle checkpoints inresponse to different cellular stresses including DNA damageand disruption of microtubule dynamics [209 210] NowBRCA1 has been implicated in the regulation of apoptosis[211] It appears that similar to p53 BRCA1 may function asa sensor of cell stress by relaying signals to either the cell-cycle checkpointmachinery or cell deathmachinery A recentstudy by Quinn et al found that BRCA1 acts as a differentialmodulator of chemotherapy-induced apoptosis in breast can-cer cells [212] They found that BRCA1 enhanced sensitivityto apoptosis induced by antimicrotubule agents such aspaclitaxel and vinorelbine but inhibited apoptosis inducedby DNA-damaging agents such as cisplatin and etoposideMoreover inhibitors of poly (adenosine diphosphate- (ADP-)ribose) polymerase (PARP) show the synthetically lethaleffect in BRCA1-defective tumors because BRCA1 encodesprotein that is required for efficient homologous recombina-tion (HR) [213]

333 Ku Protein from Gatekeeping to Caretaking Doublestrand break (DSB) repair includes homologous recombina-tion (HR) and nonhomologous end joining (NHEJ) DSBrepair through HR process is an error free pathway since itrequires an extensive region of sequence homology betweenthe damaged and template strands whereas NHEJ is anerror prone alternate pathway for the repair of DSBs whichessentially joins broken chromosomal ends independent ofsequence homology The NHEJ process is initiated by thebinding of specific protein to the broken ends which mayact as end bridging factor [214] The catalytic subunit ofDNA protein kinase (DNA-PKcs) is required in mammalianNHEJ to bridge the DNA ends through their protein-proteininteractions [215]

Cancer susceptibility genes have been categorized intotwo classes namely caretakers and gatekeepers Caretakersare involved in DNA repair and whose inactivation can leadto genomic instability while gatekeepers control cell deathand proliferation Loss of functions in both caretaker andgatekeeper genes results in an increase in cancer suscep-tibility Ku86 and p53 are examples of such caretaker andgatekeeper respectfully Their functions are closely linked[216] Ku is a caretaker gene that maintains the integrity ofthe genome by a mechanism that suppresses chromosomalrearrangements Ku complex (a heterodimer of Ku70Ku80[asymp86]) is a major end binding factor in mammalian cellspossessing end bridging activity [217 218] Ku exists as aheterodimeric DNA binding complex in eukaryotes con-sisting of two protein subunits of about 70- and 80-kDaknown as Ku70 and Ku80 (in S cerevisiae) or Ku86 (in highereukaryotes) This complex was originally identified twodecades ago as amajor target of autoantibodies from Japanesepatients with scleroderma-polymyositis overlap syndrome[219] Functional Ku proteins are critical for the maintenanceof genomic stability DNA repair and hence cellular andorganismal viability [220] Li and colleagues reported theputative tumor suppressor function of Ku70 On the otherhand Ku was identified as a nuclear protein involved in bothhomologous recombination (HR) or nonhomologous end


joining (NHEJ) Moreover Ku proteins have been implicatedin numerous other cellular processes including telomeremaintenance antigen receptor gene arrangements (eg vari-able (diversity) joining V(D)J recombination) regulationof specific gene transcription and apoptosis regulation ofheat shock-induced responses and a newly identified role inregulation of the G2 and M phases of the cell cycle [221]Moreover an association of the DNA-PK-Ku70-Ku86v witha number of cell cycle regulatory proteins such as p53 CDK4and E2F-4 had been reported suggesting a pivotal role of Kuin cell cycle regulation and malignant transformation [222]

Recently Ku70 has been shown to bind to the proapop-totic protein BAX and inhibit BAX-mediated apoptosis invitro by preventing its relocalization to the mitochondria[223] This antiapoptotic function is mediated by a domainin the carboxy-terminal of Ku70 and does not require thecooperative effects of Ku80 Although the exact function ofKu in these processes is presently still not clear what iscertain is that this protein is of fundamental importance incell viability especially under treatment stress [223] Hencethe idea of targeting Ku70 had emerged to enhance apoptosisby different therapies That was because tumor cells dependon DNA repair mechanisms to a greater extent than nor-mal cells hence many cancer therapies target such DNArepair machinery [224] As DNA-PK plays a crucial role inthe DSBR the kinase activity of the DNA-PK complex isregulated through the DNA end-binding (DEB) activity ofits regulatory subunit Ku Therefore the regulation of Kuexpression and function also plays a vital role in cancer cellsresistance to anticancer therapy Thus targeting Ku proteinled to changes in susceptibility to anticancer drug-inducedapoptosis [225 226] Most exciting are the new clinicalstudies that target Ku as their primary strategy Reports haveshown that the status of Ku or NHEJ in tumors can enhanceapoptosis by radiotherapy or chemotherapy suggesting thatKu may be a potential target to overcome resistance duringcancer treatment Recently novel therapies such as the engi-neering of selective small molecule DNA-PK inhibitors thatenhance radiation-induced tumor control in amouse-humanxenograft model of cancer have been developed and haveshown promising results [224] Other examples include theuse of adenovirus-mediated heat activated antisense Ku70expression that radiosensitizes human tumors [227] and theuse of a Ku antibody to blockMMcell adhesion and abrogatesthe protective effect of membrane Ku [228]

Further understanding of the possible link of the mainfunctions of Ku in different cell systems may also help inanswering the intriguing question of how autoantibodiesagainst Ku are generated in various autoimmune diseasesThis provides an exciting insight into the future of anticancerdevelopment It has shown that Ku70 siRNA sensitizedmammalian cells to radiation and topoisomerase II inhibitoretoposide [229] Recently small molecule HDAC inhibitorswhich targets Ku70 acetylation enhanced DNA damage byDNA-damaging agents in prostate cancer and they enhancedradiation effect in melanoma cells [230 231] Moreover Sub-ramanian used HDAC inhibitors which target ku70 acetyla-tion to induce apoptosis in neuroblastoma cells [163] Thesemolecules increase the acetylation of Ku70 in the cytoplasm

resulting in the release of Bax from Ku70 Subsequently acti-vated Bax translocates to themitochondria In our laboratorywe identifiedKu70 particularly as a requiredmolecule for thecytostatic arrest under hyperthermia treatment in nonsmalllung cancer cells In that study small interference RNAagainst Ku70 could inhibit the cytostatic arrest and switchcells to cytotoxic arrest and caspase-dependent apoptosismediated by Bax activation [232]

34 Targeting Death Receptors (DR) Many tumors refract tothe classic apoptosis-inducing cancer therapies which pro-voke intrinsic pathway-based apoptosis due to developmentof defects in that pathway under treatment stress [233] Toenhance cancer cell apoptosis and thus overcome treatmentfailure many therapeutic strategies targeting other moleculesimplicated in apoptosis resistance have been developed [9596] Hence alternative therapies which provoke the extrin-sic pathway-based apoptosis were developed For exampleattempts to apply TNF as a cancer treatment were stymiedby the proinflammatory effects of this cytokine because itinduces both caspase activation pathways and NFKappaBFortunately the TNF family cytokines FasL and TRAILtrigger caspase activation without concomitant induction ofNFKappaB giving chances for successful cancer therapy viaapoptosis where TNF failed due to toxicity The antibodiesthat trigger the receptor Fas (CD95) unfortunately showedhigh toxicity to liver [224] while TRAIL and agonistic anti-bodies that bind TRAIL receptors appear to be well toleratedin vivo As a fact Phase I trial in humans was recently com-pleted using an agonistic antibody directed against TRAIL-receptor-1 (TRAIL-R1 DR4) In mouse xenograft modelsbearing human tumor cells lines TRAIL and its agonis-tic antibodies directed against TRAIL receptors have beendemonstrated to possess potent antitumor activity [234]supporting the idea of using these biological agents as a novelapproach to cancer treatment and therebymimicking some ofthe effector mechanisms normally employed by the immunesystem in its defense against transformed cells and potentiallybypass the defective intrinsic (mitochondrial) pathway toapoptosis

Synthetic triterpenoids such as CDDO and CDDOmsensitize solid tumor cell lines to TRAIL and induce apop-tosis as single agents in leukemia cells through a caspase-8-dependent mechanism that remains operative even inchemorefractory cells [235ndash237] Moreover in leukemiathe protein kinase C (PKC) modulator byrostatin inducesmyeloid leukemia cell lines to produce TNF resultingin autocrine engagement of TNF-receptors and apoptosisinduction through a mechanism that is suppressible byTNFR-Fc fusion protein and caspase-8 dominant-negative[238] Similarly all-trans-retinoic acid (ATRA) inducesTRAIL production and triggers autocrine induction of apop-tosis in acute promyelomonocytic leukemia (APML) cellsthat harbor the RAR-PML fusion protein resulting fromt(15 17) chromosomal translocations [239]

TRAIL a candidate for targeted therapy which can pref-erentially kill cancer cells is frequently hampered by variousmechanisms of cancer cell resistance to apoptosis [240 241]As a cytokine TRAIL induces apoptosis by binding one of


its cognate death receptors and plays an important role inimmune surveillance against tumors [49 240 241] Neverthe-less in many types of cancer cells effective antitumor activityof TRAIL requires the suppression of aberrantly expressednegative regulators of apoptosis [240 241] In general asmultiple cell signaling mechanisms may control apoptosiscancer cells can employ a number of different strategies tosuppress a protective apoptotic response [6ndash8] From otherside survival signaling pathways are linked to the apoptoticmachinery These pathways can modulate components of theapoptoticmachinery itself or key regulatorymolecules withinthe core apoptotic pathways [242 243] Notably variousupstream signaling pathways often impinge on the same fewcentral apoptosis control points which involve some crucialmembers of the Bcl-2 family inhibitor of apoptosis (IAP)proteins and FLICE-inhibitory protein (c-FLIP) [6 7 38 40]

35 NF-120581B as a Target for Apoptosis Induction NF-120581B is atranscription factor that was discovered in the nucleus of Bcells and binds to the enhancer of the kappa light chain ofimmunoglobulin It is expressedwidely in the cytoplasmof alltypes of cells NF-120581B is an important molecular link betweenchronic inflammation cell cycle cancer development andcell death [6 244ndash247] The transactive NF-120581B suppressesapoptosis by inducing the expression of some apoptosis-inhibitory genes including IAPs cFLIP TNF receptor asso-ciated factor 1 (TRAF1) and TRAF2 [248] Two typicalprosurvival NF-120581B targets are Bcl-xL and XIAP which canblock apoptosis at multiple steps [249 250] ImportantlyChuang et al demonstrated that a wide range of cytotoxicdrugs (5-FU doxorubicin paclitaxel and cisplatin) activatedNF-120581B in a panel of cancer cell lines [251] This suggests thatNF-120581B activation is a general feature of cancer cell responseto chemotherapy For instance increased NF-120581B activityin patients with oesophageal cancer has been correlatedwith reduced response to neoadjuvant chemotherapy andradiotherapy [252] Now it is believed that NF-120581B appearsto be a critical determinant of drug resistance its activationreduces apoptosis by chemotherapy [247] A number of invitro studies demonstrated that inhibition ofNF-120581B sensitizescancer cells to chemotherapy-induced apoptosis [253ndash255]Furthermore NF-120581B is believed to be a major target forproteasome inhibitors as proteasome inhibition preventsdegradation of I120581B blocking NF-120581B nuclear translocation[255 256] Clinical trials with proteasome inhibitors such asbortezomib are underway to inhibit NF-120581B signalling andenhance drug-induced apoptosis in cancers

36 Targeting Multiple Pathways Regulators Like antiapop-totic Bcl-2 proteins overexpression IAPs overexpressionis associated with poor prognosis and chemoresistance inmany cancers [257ndash259] It acted as a therapeutic targetfor apoptosis-inducing strategies [260] Antisense oligonu-cleotides against XIAP and survivin have been developed[249] In addition small-molecule inhibitors that bind to theBIR2 or BIR3 domain of XIAP cIAP1 and cIAP2 enhanceapoptosis [249] Most of small-molecule IAP antagonists areSMACmimetics several of which are in advanced preclinical

or early clinical development Bivalent SMAC mimeticswhich bind to both the BIR2 and BIR3 domains within asingle molecule of XIAP as well as the BIR3 domains of twocIAPmolecules induce their dimerization and subsequentlytrigger their proteasome mediated degradation are moresignificant potent than their monovalent counterparts [257258] Despite evidence indicating that SMACmimetics showgreat promise for cancer therapy [257] they can induceloss of cIAP1 and cIAP2 resulting in NIK stabilization andconsequent NF-kB activation [48 257]

Targeting c-FLIP appears to be a highly promising thera-peutic strategy to reduce the apoptotic threshold because itsoverexpression can protect cancer cells from both TRAIL andchemotherapy-induced apoptosis while small interferingRNA- (siRNA-)mediated downregulation of c-FLIP is able tosensitize cancer cells to FASL TRAIL and chemotherapeuticagents [39 101] Targeting FLIP by siRNAs in a varietyof cancer cell types showed their potential as therapeuticagents to induce apoptosis [101] Nevertheless thewidespreaduse of such strategy in clinical settings depends on thesafety delivery of siRNA [261] Thus many research effortshave been devoted to improve RNA interference (RNAi)therapeutics which lead to important advances in the field[262 263] In May 2008 the first Phase I clinical trial forthe treatment of solid tumors involving systemic deliveryof siRNA via targeted nanoparticles was initiated (Clini-calTrialsgov identifier NCT00689065) [262] Importantlydata from this trial demonstrated for the first time thatsystemically delivered siRNA can reduce protein levels of aspecific gene through an RNAi mechanism in humans [264]This finding opens the gate for future application of siRNAas a gene-specific tool for cancer treatment clinically Theseapplications facilitate targeting the antiapoptotic genesrsquo prod-ucts to kill cancer cell either alone or in combination withclassic therapies Recently c-FLIP and other antiapoptoticproteins are promising targets for the development of RNAitherapeutics [101] Aswell as RNAi-mediated downregulationof c-FLIP RNAi-based reduction of Bcl-2 Bcl-xL XIAP andsurvivin has also been shown to sensitize cancers cells to arange of cancer therapies including chemotherapeutic drugsand TRAIL [265]

37 Targeting Heat Shock Chaperons

371 HSP90 Heat shock proteins 90 (Hsp90s) are abun-dantly and ubiquitously expressed proteins required for theenergy-driven stabilisation conformation and function ofa large number of cellular proteins named clinets [266267] Several key Hsp90 proteins are involved in the pro-cesses characteristic to the malignant phenotype such asinvasion angiogenesis metastasis and treatment resistance[268ndash270] They also contribute to leading mechanism ofmitogen-activated protein kinases (MAPK) and nuclear fac-tor kappa B (NF-120581B) induction [271ndash273] Moreover Hsp90stabilises Raf-1 Akt and ErbB2 proteins [274ndash276] whichare known to be associated with protection against radiation-induced cell death [277ndash279] Molecular studies suggestedthat inhibiting HSP90 by targeted therapy could providea promising strategy to enhance apoptosis by conventional


therapies [280ndash286] The inhibitor of Hsp90 geldanamycinand its derivatives successfully enhance the radiosensitivityof tumor cell lines derived from different origins includingglioma prostate pancreas and cervix [276 280ndash284 287]However geldanamycins have several limitations includ-ing poor solubility formulation difficulties hepatotoxicityand extensive metabolism by polymorphic enzymes alongwith drug efflux by P-glycoprotein therefore efforts todesign small synthetic inhibitors of Hsp90 with improvedbioavailability and lower toxicity are devoted [288ndash291] Nowpyrazole resorcinol compounds act as stronger inhibitorsof Hsp90 than geldanamycin derivatives Currently theisoxazole resorcinol NVP-AUY922 shows the highest affin-ity for the NH2-terminal nucleotide-binding site of Hsp90[290 291] whereas NVP-BEP800 represents a novel fullysynthetic orally available 2-aminothieno [23-d] pyrimidineclass Hsp90 inhibitor [292] Both compounds have goodpharmaceutical and pharmacological properties They alsoexhibit strong antiproliferative activity against various tumorcell lines and primary tumors in vitro and in vivo at well-tolerated doses [292] The novel inhibitors of Hsp90 cansensitize various tumor cells to apoptosis by destabilisationand depletion of several Hsp90 client proteins thus causingthe depletion of S phase and G2M arrest by heat shockincreased DNA damage and repair protraction and finallyapoptosis [293]

372 Clusterin Clusterin (CLU) is a cytoprotective heatchaperone protein involved in numerous physiological pro-cesses important for carcinogenesis and tumor growthincluding apoptotic cell death cell cycle regulation DNArepair cell adhesion and theromprotection [294] It is nowaccepted that the primary function of the 67ndash80 kDa cyto-plasmic CLU (sCLU) protein form is cytoprotective as a stressresponse gene sCLU expression is consistently reported tobe increasedwithmany apoptosis-inducers chemotherapy orradiotherapy treatment as an adaptive cell survival moleculein vivo and in vitro to block apoptosis [295] That wasalso shown in human tumor tissues from prostate [296297] kidney [298] breast [299] ovarian [300] colon [301]lung [302] pancreas [303] cervix [304] glioma [305] andanaplastic large cell lymphoma [306]

It has recently been shown that sCLU knockdown inhuman cancer cells using siRNA-mediated CLU gene silenc-ing induces significant reduction of cellular growth andhigher rates of spontaneous apoptosis [294] Thus we con-sider the fact that clusterin as a chaperon molecule has beenfound to bind with the active form of Bax under apoptoticstimuli inhibiting its dimerization in the mitochondria andblock apoptosis Consequently it has been hypothesizedthat sCLU gene silencing using siRNA or other techniquesmay ultimately develop into attractive antitumor apoptoticinduction [294] Thus many researchers targeted sCLUexpression silencing using antisense oligonucleotides (ASO)or RNAi as promising tools for cancer therapy [307ndash309]However that was more effective when given in combinationwith convention therapies to synergize the effect of suchcombination therapy [310ndash312] The ASO was challenged bythe rapid intracellular degeneration of oligonucleotides in

in vivo experiments That opened the gate for inventing thefirst generation ASO in which the phosphoryl oxygen ofDNA was replaced with a sulphate to create a phosphothiatebackbone ASOs intended for cancer therapy Recently moremodifications were made to the ribose the 20-positionto improve the pharmacokinetic characteristics of second-generation phosphothioate ASOs for example OGX-011[313]

In advanced breast cancer targeting CLU by OGX-011enhanced the apoptotic effect by Trastuzumab an HER-2-targeted monoclonal antibody used in the clinical man-agement of advanced breast cancer patients Importantlyonly the combination of OGX-011 and Tratuzumab leads toactivation of apoptosis that was not observed with eitheragent alone Phase I and phase II studies have suggested acombined therapy usingASOs against both of CLU andBcl-2along with Trastuzumab for advanced breast cancer patients[314 315] Targeting CLU by ASO enhanced apoptosis bypaclitaxel or radiation in PC-3 prostate cancer cells [314]

Phases I and II trials in prostate cancer have shownthat OGX-011 significantly enhanced the apoptotic responseand efficacy of chemotherapy radiation and androgen with-drawal by inhibiting the expression of CLU In other prostatecancer phase I trials OGX-011 was given prior to radicalprostoctomy while some ldquowell toleratedrdquo phase II trials wereestablished based on the biologic effectiveness of OGX-011[315]

In our laboratory we reported for the first time the asso-ciation between upregulation of the sCLU and persistenceagainst apoptosis by paclitaxel in ovarian cancer cells andhuman tumors Importantly when we targeted CLU eitherby OGX-011 or RNAi we successfully enhanced caspase-dependent apoptosis and the cells restored their sensitivityto paclitaxel [144] Similarly CLU ASO enhanced cisplatin-induced apoptosis human bladder cancer cells and humanlung adenocarcinoma both in vitro and in vivo [304]

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

References

[1] R A Lockshin and C M Williams ldquoProgrammed cell death-ICytology of degeneration in the intersegmental muscles of thePernyi silkmothrdquo Journal of Insect Physiology vol 11 no 2 pp123ndash133 1965

[2] T G Cotter ldquoApoptosis and cancer the genesis of a researchfieldrdquo Nature Reviews Cancer vol 9 no 7 pp 501ndash507 2009

[3] J F Kerr A H Wyllie and A R Currie ldquoApoptosis abasic biological phenomenon with wide-ranging implicationsin tissue kineticsrdquo The British Journal of Cancer vol 26 no 4pp 239ndash257 1972

[4] T D Halazonetis V G Gorgoulis and J Bartek ldquoAn oncogene-induced DNA damage model for cancer developmentrdquo Sciencevol 319 no 5868 pp 1352ndash1355 2008

[5] S Negrini V G Gorgoulis and T D Halazonetis ldquoGenomicinstability an evolving hallmark of cancerrdquo Nature ReviewsMolecular Cell Biology vol 11 no 3 pp 220ndash228 2010


[6] S Fulda ldquoEvasion of apoptosis as a cellular stress response incancerrdquo International Journal of Cell Biology vol 2010 ArticleID 370835 6 pages 2010

[7] J Plati O Bucur and R Khosravi-Far ldquoDysregulation ofapoptotic signaling in cancer molecular mechanisms andtherapeutic opportunitiesrdquo Journal of Cellular Biochemistry vol104 no 4 pp 1124ndash1149 2008

[8] DHanahan andRAWeinberg ldquoThehallmarks of cancerrdquoCellvol 100 no 1 pp 57ndash70 2000

[9] J C Reed J M Jurgensmeier and S Matsuyama ldquoBcl-2 familyproteins and mitochondriardquo Biochimica et Biophysica Acta vol1366 no 1-2 pp 127ndash137 1998

[10] D R Green and G I Evan ldquoA matter of life and deathrdquo CancerCell vol 1 no 1 pp 19ndash30 2002

[11] Y Ionov H Yamamoto S Krajewski J C Reed and M Peru-cho ldquoMutational inactivation of the proapoptotic gene BAXconfers selective advantage during tumor clonal evolutionrdquoProceedings of the National Academy of Sciences of the UnitedStates of America vol 97 no 20 pp 10872ndash10877 2000

[12] TMiyashita S KrajewskiM Krajewska et al ldquoTumor suppres-sor p53 is a regulator of bcl-2 and bax gene expression in vitroand in vivordquo Oncogene vol 9 no 6 pp 1799ndash1805 1994

[13] D L Vaux ldquoImmunopathology of apoptosismdashintroduction andoverviewrdquo Springer Seminars in Immunopathology vol 19 no 3pp 271ndash278 1998

[14] S M Frisch and R A Screaton ldquoAnoikis mechanismsrdquo CurrentOpinion in Cell Biology vol 13 no 5 pp 555ndash562 2001

[15] J Tschopp F Martinon and K Hofmann ldquoApoptosis silencingthe death receptorsrdquo Current Biology vol 9 no 10 pp R381ndashR384 1999

[16] GMakin and J AHickman ldquoApoptosis and cancer chemother-apyrdquo Cell and Tissue Research vol 301 no 1 pp 143ndash152 2000

[17] V Cryns and J Yuan ldquoProteases to die forrdquo Genes and Develop-ment vol 12 no 11 pp 1551ndash1570 1998

[18] N A Thornberry and Y Lazebnik ldquoCaspases enemies withinrdquoScience vol 281 no 5381 pp 1312ndash1316 1998

[19] R M Locksley N Killeen and M J Lenardo ldquoThe TNF andTNF receptor superfamilies integrating mammalian biologyrdquoCell vol 104 no 4 pp 487ndash501 2001

[20] DWallach E E Varfolomeev N LMalinin Y V Goltsev A VKovalenko and M P Boldin ldquoTumor necrosis factor receptorand Fas signaling mechanismsrdquo Annual Review of Immunologyvol 17 pp 331ndash367 1999

[21] D R Green and G Kroemer ldquoThe pathophysiology of mito-chondrial cell deathrdquo Science vol 305 no 5684 pp 626ndash6292004

[22] D Chauhan T Hideshima S Rosen J C Reed S Kharbandaand K C Anderson ldquoApaf-1Cytochrome c-independent andSmac-dependent Induction of Apoptosis in Multiple Myeloma(MM)Cellsrdquo Journal of Biological Chemistry vol 276 no 27 pp24453ndash24456 2001

[23] G Kroemer and J C Reed ldquoMitochondrial control of celldeathrdquo Nature Medicine vol 6 no 5 pp 513ndash519 2000

[24] B Motyka G Korbutt M J Pinkoski et al ldquoMannose 6-phosphateinsulin-like growth factor II receptor is a deathreceptor for granzyme B during cytotoxic T cell-induced apop-tosisrdquo Cell vol 103 no 3 pp 491ndash500 2000

[25] P Salomoni and P P Pandolfi ldquoThe role of PML in tumorsuppressionrdquo Cell vol 108 no 2 pp 165ndash170 2002

[26] K L King and J A Cidlowski ldquoCell cycle regulation andapoptosisrdquo Annual Review of Physiology vol 60 pp 601ndash6171998

[27] J F Kerr and J Searle ldquoA mode of cell loss in malignantneoplasmsrdquo Journal of Pathology vol 106 no 1 1972

[28] J C Reed ldquoProapoptotic multidomain Bcl-2Bax-family pro-teins mechanisms physiological roles and therapeutic oppor-tunitiesrdquo Cell Death and Differentiation vol 13 no 8 pp 1378ndash1386 2006

[29] A Letai ldquoBCL-2 found bound and druggedrdquo Trends inMolecular Medicine vol 11 no 10 pp 442ndash444 2005

[30] H Kim M Rafiuddin-Shah H-C Tu et al ldquoHierarchicalregulation of mitochondrion-dependent apoptosis by BCL-2subfamiliesrdquo Nature Cell Biology vol 8 no 12 pp 1348ndash13582006

[31] M C Wei W-X Zong E H-Y Cheng et al ldquoProapoptoticBAX and BAK a requisite gateway to mitochondrial dysfunc-tion and deathrdquo Science vol 292 no 5517 pp 727ndash730 2001

[32] W-X Zong T Lindsten A J Ross G R MacGregor and CB Thompson ldquoBH3-only proteins that bind pro-survival Bcl-2family members fail to induce apoptosis in the absence of Baxand Bakrdquo Genes and Development vol 15 no 12 pp 1481ndash14862001

[33] D R Green ldquoAt the gates of deathrdquo Cancer Cell vol 9 no 5 pp328ndash330 2006

[34] S A Amundson T G Myers D Scudiero S Kitada J CReed and J Fornace AJ ldquoAn informatics approach identifyingmarkers of chemosensitivity in human cancer cell linesrdquoCancerResearch vol 60 no 21 pp 6101ndash6110 2000

[35] C Teixeira J C Reed and M A C Pratt ldquoEstrogen promoteschemotherapeutic drug resistance by a mechanism involvingBcl-2 proto-oncogene expression in human breast cancer cellsrdquoCancer Research vol 55 no 17 pp 3902ndash3907 1995

[36] S Elmore ldquoApoptosis a review of programmed cell deathrdquoToxicologic Pathology vol 35 no 4 pp 495ndash516 2007

[37] S Koyama N Koike and S Adachi ldquoFas receptor counterattackagainst tumor-infiltrating lymphocytes in vivo as a mechanismof immune escape in gastric carcinomardquo Journal of CancerResearch and Clinical Oncology vol 127 no 1 pp 20ndash26 2001

[38] M Bagnoli S Canevari and D Mezzanzanica ldquoCellularFLICE-inhibitory protein (c-FLIP) signalling a key regulatorof receptor-mediated apoptosis in physiologic context and incancerrdquo International Journal of Biochemistry and Cell Biologyvol 42 no 2 pp 210ndash213 2010

[39] A R Safa T W Day and C-H Wu ldquoCellular FLICE-likeinhibitory protein (C-FLIP) a novel target for cancer therapyrdquoCurrent Cancer Drug Targets vol 8 no 1 pp 37ndash46 2008

[40] T R Wilson K M Redmond K M McLaughlin et alldquoProcaspase 8 overexpression in non-small-cell lung cancerpromotes apoptosis induced by FLIP silencingrdquo Cell Death andDifferentiation vol 16 no 10 pp 1352ndash1361 2009

[41] L-Y Chen T-H Chen P-YWen et al ldquoDifferential expressionof NUDT9 at different phases of the menstrual cycle andin different components of normal and neoplastic humanendometriumrdquo Taiwanese Journal of Obstetrics and Gynecologyvol 48 no 2 pp 96ndash107 2009

[42] P Korkolopoulou A A Saetta G Levidou et al ldquoc-FLIPexpression in colorectal carcinomas association with FasFasLexpression and prognostic implicationsrdquoHistopathology vol 51no 2 pp 150ndash156 2007


[43] S Gao H Wang P Lee et al ldquoAndrogen receptor and prostateapoptosis response factor-4 target the c-FLIP gene to determinesurvival and apoptosis in the prostate glandrdquo Journal of Molec-ular Endocrinology vol 36 no 3 pp 463ndash483 2006

[44] X Zhang T-G Jin H YangWCDewolf R Khosravi-Far andA F Olumi ldquoPersistent c-FLIP(L) expression is necessary andsufficient tomaintain resistance to tumor necrosis factor-relatedapoptosis-inducing ligand-mediated apoptosis in prostate can-cerrdquo Cancer Research vol 64 no 19 pp 7086ndash7091 2004

[45] X Zhang L ZhangHYang et al ldquoc-Fos as a proapoptotic agentin TRAIL-induced apoptosis in prostate cancer cellsrdquo CancerResearch vol 67 no 19 pp 9425ndash9434 2007

[46] X Du G Bao X He et al ldquoExpression and biological signifi-cance of c-FLIP in human hepatocellular carcinomasrdquo Journalof Experimental and Clinical Cancer Research vol 28 no 1article 24 2009

[47] J H Song M C L Tse A Bellail et al ldquoLipid rafts and non-rafts mediate tumor necrosis factor-related apoptosis-inducingligand-induced apoptotic and nonapoptotic signals in non-small cell lung carcinoma cellsrdquo Cancer Research vol 67 no 14pp 6946ndash6955 2007

[48] V Baud and M Karin ldquoIs NF-120581B a good target for cancertherapy Hopes and pitfallsrdquo Nature Reviews Drug Discoveryvol 8 no 1 pp 33ndash40 2009

[49] M E Guicciardi and G J Gores ldquoLife and death by deathreceptorsrdquoTheFASEB Journal vol 23 no 6 pp 1625ndash1637 2009

[50] T S Jani J DeVecchio T Mazumdar A Agyeman and JA Houghton ldquoInhibition of NF-120581B signaling by quinacrine iscytotoxic to human colon carcinoma cell lines and is synergisticin combination with tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) or Oxaliplatinrdquo Journal of BiologicalChemistry vol 285 no 25 pp 19162ndash19172 2010

[51] X Saelens N Festjens L Vande Walle M Van Gurp GVan Loo and P Vandenabeele ldquoToxic proteins released frommitochondria in cell deathrdquo Oncogene vol 23 no 16 pp 2861ndash2874 2004

[52] S Fulda I Jeremias and K-M Debatin ldquoCooperation ofbetulinic acid and TRAIL to induce apoptosis in tumor cellsrdquoOncogene vol 23 no 46 pp 7611ndash7620 2004

[53] J Ajani ldquoReview of capecitabine as oral treatment of gastricgastroesophageal and esophageal cancersrdquo Cancer vol 107 no2 pp 221ndash231 2006

[54] W B Ershler ldquoCapecitabine use in geriatric oncology ananalysis of current safety efficacy and quality of life datardquoCritical Reviews in OncologyHematology vol 58 no 1 pp 68ndash78 2006

[55] I PetakDMTillman and J AHoughton ldquop53Dependence ofFas induction and acute apoptosis in response to 5-fluorouracil-leucovorin in human colon carcinoma cell linesrdquo ClinicalCancer Research vol 6 no 11 pp 4432ndash4441 2000

[56] H H J Backus D Wouters C G Ferreira et al ldquoThymidylatesynthase inhibition triggers apoptosis via caspases-8 and -9in both wild-type and mutant p53 colon cancer cell linesrdquoEuropean Journal of Cancer vol 39 no 9 pp 1310ndash1317 2003

[57] F Bunz P M Hwang C Torrance et al ldquoDisruption of p53 inhuman cancer cells alters the responses to therapeutic agentsrdquoJournal of Clinical Investigation vol 104 no 3 pp 263ndash2691999

[58] Y M Rustum ldquoThymidylate synthase a critical target in cancertherapyrdquo Frontiers in Bioscience vol 9 pp 2467ndash2473 2004

[59] R M Schultz V F Patel J F Worzalla and C Shih ldquoRole ofthymidylate synthase in the antitumor activity of the multitar-geted antifolate LY231514rdquo Anticancer Research vol 19 no 1 App 437ndash443 1999

[60] E Chu D M Koeller P G Johnston S Zinn and C J AllegraldquoRegulation of thymidylate synthase in human colon cancercells treated with 5-fluorouracil and interferon-120574rdquo MolecularPharmacology vol 43 no 4 pp 527ndash533 1993

[61] E Chu D M Voeller K L Jones et al ldquoIdentification ofa thymidylate synthase ribonucleoprotein complex in humancolon cancer cellsrdquoMolecular and Cellular Biology vol 14 no 1pp 207ndash213 1994

[62] D B Longley D P Harkin and P G Johnston ldquo5-Fluorouracilmechanisms of action and clinical strategiesrdquo Nature ReviewsCancer vol 3 no 5 pp 330ndash338 2003

[63] D B Longley P R Ferguson J Boyer et al ldquoCharacterizationof a thymidylate synthase (TS)-inducible cell line a modelsystem for studying sensitivity to TS- and non-TS-targetedchemotherapiesrdquo Clinical Cancer Research vol 7 no 11 pp3533ndash3539 2001

[64] D B Longley J Boyer W L Allen et al ldquoThe role ofthymidylate synthase induction in modulating p53-regulatedgene expression in response to 5-fluorouracil and antifolatesrdquoCancer Research vol 62 no 9 pp 2644ndash2649 2002

[65] P G Johnston H-J Lenz C G Leichman et al ldquoThymidylatesynthase gene and protein expression correlate and are associ-ated with response to 5-fluorouracil in human colorectal andgastric tumorsrdquo Cancer Research vol 55 no 7 pp 1407ndash14121995

[66] H-J Lenz K Hayashi D Salonga et al ldquop53 point mutationsand thymidylate synthase messenger RNA levels in dissemi-nated colorectal cancer an analysis of response and survivalrdquoClinical Cancer Research vol 4 no 5 pp 1243ndash1250 1998

[67] S Marsh and H L McLeod ldquoThymidylate synthase pharmaco-genetics in colorectal cancerrdquo Clinical Colorectal Cancer vol 1no 3 pp 175ndash179 2001

[68] J F Dillman III L P Dabney and K K Pfister ldquoCytoplasmicdynein is associated with slow axonal transportrdquo Proceedings ofthe National Academy of Sciences of the United States of Americavol 93 no 1 pp 141ndash144 1996

[69] MA Jordan R J TosoDThrower andLWilson ldquoMechanismof mitotic block and inhibition of cell proliferation by taxolat low concentrationsrdquo Proceedings of the National Academy ofSciences of the United States of America vol 90 no 20 pp 9552ndash9556 1993

[70] M A Jordan K Wendell S Gardiner W B Derry H Coppand L Wilson ldquoMitotic block induced in HeLa cells by lowconcentrations of paclitaxel (taxol) results in abnormal mitoticexit and apoptotic cell deathrdquoCancer Research vol 56 no 4 pp816ndash825 1996

[71] D PandaH PMiller A Banerjee R F Luduena andLWilsonldquoMicrotubule dynamics in vitro are regulated by the tubulinisotype compositionrdquo Proceedings of the National Academy ofSciences of the United States of America vol 91 no 24 pp 11358ndash11362 1994

[72] S Ranganathan C A Benetatos P J Colarusso D W Dexterand G R Hudes ldquoAltered 120573-tubulin isotype expression inpaclitaxel-resistant human prostate carcinoma cellsrdquoTheBritishJournal of Cancer vol 77 no 4 pp 562ndash566 1998

[73] MHaber C A Burkhart D L Regl JMadafiglioMDNorrisand S B Horwitz ldquoAltered expression of M1205732 the class II 120573-tubulin isotype in a murine J7742 cell line with a high level of


taxol resistancerdquo Journal of Biological Chemistry vol 270 no 52pp 31269ndash31275 1995

[74] K Kamath L Wilson F Cabral and M A Jordan ldquo120573III-tubulin induces paclitaxel resistance in associationwith reducedeffects onmicrotubule dynamic instabilityrdquo Journal of BiologicalChemistry vol 280 no 13 pp 12902ndash12907 2005

[75] F Cabral I Abraham and M M Gottesman ldquoIsolation of ataxol-resistant Chinese hamster ovary cell mutant that has analteration in 120572-tubulinrdquo Proceedings of the National Academy ofSciences of the United States of America vol 78 no 7 I pp 4388ndash4391 1981

[76] C H A Cheung S-Y Wu T-R Lee et al ldquoCancer cellsacquire mitotic drug resistance properties through beta i-tubulin mutations and alterations in the expression of beta-tubulin isotypesrdquo PLoS ONE vol 5 no 9 Article ID e12564pp 1ndash11 2010

[77] S Yin R Bhattacharya and F Cabral ldquoHuman mutations thatconfer paclitaxel resistancerdquoMolecular CancerTherapeutics vol9 no 2 pp 327ndash335 2010

[78] M Kartalou and J M Essigmann ldquoRecognition of cisplatinadducts by cellular proteinsrdquoMutation ResearchmdashFundamentaland Molecular Mechanisms of Mutagenesis vol 478 no 1-2 pp1ndash21 2001

[79] F J Dijt A M J Fichtinger-Schepman F Berends and JReedijk ldquoFormation and repair of cisplatin-induced adducts toDNA in cultured normal and repair-deficient human fibrob-lastsrdquo Cancer Research vol 48 no 21 pp 6058ndash6062 1988

[80] R P Perez ldquoCellular and molecular determinants of cisplatinresistancerdquo European Journal of Cancer vol 34 no 10 pp 1535ndash1542 1998

[81] A Nehme R Baskaran S Aebi et al ldquoDifferential induction ofc-JunNH2-terminal kinase and c-Abl kinase in DNAmismatchrepair-proficient and -deficient cells exposed to cisplatinrdquo Can-cer Research vol 57 no 15 pp 3253ndash3257 1997

[82] H Niedner R Christen X Lin A Kondo and S B HowellldquoIdentification of genes that mediate sensitivity to cisplatinrdquoMolecular Pharmacology vol 60 no 6 pp 1153ndash1160 2001

[83] S N Farrow and R Brown ldquoNew members of the Bcl-2 familyand their protein partnersrdquo Current Opinion in Genetics andDevelopment vol 6 no 1 pp 45ndash49 1996

[84] R Agarwal and S B Kaye ldquoOvarian cancer strategies for over-coming resistance to chemotherapyrdquo Nature Reviews Cancervol 3 no 7 pp 502ndash516 2003

[85] A G Eliopoulos D J Kerr J Herod et al ldquoThe control ofapoptosis and drug resistance in ovarian cancer influence ofp53 and Bcl-2rdquo Oncogene vol 11 no 7 pp 1217ndash1228 1995

[86] A Strasser A W Harris T Jacks and S Cory ldquoDNA damagecan induce apoptosis in proliferating lymphoid cells via p53-independent mechanisms inhibitable by Bcl-2rdquo Cell vol 79 no2 pp 329ndash339 1994

[87] J J O Herod A G Eliopoulos J Warwick G Niedobitek L SYoung and D J Kerr ldquoThe prognostic significance of Bcl-2 andp53 expression in ovarian carcinomardquo Cancer Research vol 56no 9 pp 2178ndash2184 1996

[88] HMiyake I Hara K Yamanaka S Arakawa and S KamidonoldquoSynergistic enhancement of resistance to cisplatin in humanbladder cancer cells by overexpression of mutant-type p53 andBcl-2rdquo Journal of Urology vol 162 no 6 pp 2176ndash2181 1999

[89] S Kondo ldquoApoptosis by antitumor agents and other factors inrelation to cell cycle checkpointsrdquo Journal of radiation researchvol 36 no 1 pp 56ndash62 1995

[90] J J Turchi K M Henkels I L Hermanson and S M PatrickldquoInteractions of mammalian proteins with cisplatin-damagedDNArdquo Journal of Inorganic Biochemistry vol 77 no 1-2 pp 83ndash87 1999

[91] G Gebauer A T Peter D Onesime and N DhanasekaranldquoApoptosis of ovarian granulosa cells correlation with thereduced activity of ERK-signaling modulerdquo Journal of CellularBiochemistry vol 75 no 4 pp 547ndash554 1999

[92] S H Kaufmann and D L Vaux ldquoAlterations in the apoptoticmachinery and their potential role in anticancer drug resis-tancerdquo Oncogene vol 22 no 47 pp 7414ndash7430 2003

[93] CA Schmitt C T Rosenthal and SW Lowe ldquoGenetic analysisof chemoresistance in primary murine lymphomasrdquo NatureMedicine vol 6 no 9 pp 1029ndash1035 2000

[94] J Meiler and M Schuler ldquoTherapeutic targeting of apoptoticpathways in cancerrdquo Current Drug Targets vol 7 no 10 pp1361ndash1369 2006

[95] P Gimenez-Bonafe A Tortosa and R Perez-Tomas ldquoOver-coming drug resistance by enhancing apoptosis of tumor cellsrdquoCurrent Cancer Drug Targets vol 9 no 3 pp 320ndash340 2009

[96] T R Wilson P G Johnston and D B Longley ldquoAnti-apoptoticmechanisms of drug resistance in cancerrdquo Current Cancer DrugTargets vol 9 no 3 pp 307ndash319 2009

[97] M H Kang and C P Reynolds ldquoBcI-2 Inhibitors targetingmitochondrial apoptotic pathways in cancer therapyrdquo ClinicalCancer Research vol 15 no 4 pp 1126ndash1132 2009

[98] M R Patel A Masood P S Patel and A A Chanan-KhanldquoTargeting the Bcl-2rdquo Current Opinion in Oncology vol 21 no6 pp 516ndash523 2009

[99] B Leibowitz and J Yu ldquoMitochondrial signaling in cell deathvia the Bcl-2 familyrdquo Cancer Biology and Therapy vol 9 no 6pp 417ndash422 2010

[100] M C De Almagro and D Vucic ldquoThe inhibitor of apoptosis(IAP) proteins are critical regulators of signaling pathways andtargets for anti-cancer therapyrdquo Experimental Oncology vol 34no 3 pp 200ndash211 2012

[101] TW Day andA R Safa ldquoRNA interference in cancer targetingthe anti-apoptotic protein c-FLIP for drug discoveryrdquo Mini-Reviews in Medicinal Chemistry vol 9 no 6 pp 741ndash748 2009

[102] K N Chi M E Gleave R Klasa et al ldquoA phase I dose-finding study of combined treatment with an antisense Bcl-2oligonucleotide (Genasense) andmitoxantrone in patients withmetastatic hormone-refractory prostate cancerrdquoClinical CancerResearch vol 7 no 12 pp 3920ndash3927 2001

[103] J C Reed and M Pellecchia ldquoApoptosis-based therapies forhematologic malignanciesrdquo Blood vol 106 no 2 pp 408ndash4182005

[104] D M Hockenbery ldquoTargeting mitochondria for cancer ther-apyrdquo Environmental and Molecular Mutagenesis vol 51 no 5pp 476ndash489 2010

[105] A LetaiMC Bassik LDWalenskyMD Sorcinelli SWeilerand S J Korsmeyer ldquoDistinct BH3 domains either sensitize oractivate mitochondrial apoptosis serving as prototype cancertherapeuticsrdquo Cancer Cell vol 2 no 3 pp 183ndash192 2002

[106] L D Walensky A L Kung I Escher et al ldquoActivation ofapoptosis in vivo by a hydrocarbon-stapled BH3 helixrdquo Sciencevol 305 no 5689 pp 1466ndash1470 2004

[107] TOltersdorf SW Elmore A R Shoemaker et al ldquoAn inhibitorof Bcl-2 family proteins induces regression of solid tumoursrdquoNature vol 435 no 7042 pp 677ndash681 2005


[108] C Tse A R Shoemaker J Adickes et al ldquoABT-263 a potentand orally bioavailable Bcl-2 family inhibitorrdquo Cancer Researchvol 68 no 9 pp 3421ndash3428 2008

[109] E Wesarg S Hoffarth R Wiewrodt et al ldquoTargeting BCL-2family proteins to overcome drug resistance in non-small celllung cancerrdquo International Journal of Cancer vol 121 no 11 pp2387ndash2394 2007

[110] M Certo V D G Moore M Nishino et al ldquoMitochondriaprimed by death signals determine cellular addiction to anti-apoptotic BCL-2 family membersrdquo Cancer Cell vol 9 no 5 pp351ndash365 2006

[111] R Yamaguchi E Janssen G Perkins M Ellisman S Kitadaand J C Reed ldquoEfficient elimination of cancer cells bydeoxyglucose-ABT-263737 combination therapyrdquo PLoS ONEvol 6 no 9 Article ID e24102 2011

[112] C L Hann V C Daniel E A Sugar et al ldquoTherapeutic efficacyof ABT-737 a selective inhibitor of BCL-2 in small cell lungcancerrdquo Cancer Research vol 68 no 7 pp 2321ndash2328 2008

[113] J C Byrd S Kitada I W Flinn et al ldquoThe mechanism oftumor cell clearance by rituximab in vivo in patients with B-cellchronic lymphocytic leukemia evidence of caspase activationand apoptosis inductionrdquo Blood vol 99 no 3 pp 1038ndash10432002

[114] B Gong Q Chen B Endlich S Mazumder and A AlmasanldquoIonizing radiation-induced bax-mediated cell death is depen-dent on activation of cysteine and serine proteasesrdquoCell Growthand Differentiation vol 10 no 7 pp 491ndash502 1999

[115] Q Chen B Gong and A Almasan ldquoDistinct stages ofcytochrome c release from mitochondria evidence for a feed-back amplification loop linking caspase activation tomitochon-drial dysfunction in genotoxic stress induced apoptosisrdquo CellDeath and Differentiation vol 7 no 2 pp 227ndash233 2000

[116] B Vogelstein D Lane and A J Levine ldquoSurfing the p53networkrdquo Nature vol 408 no 6810 pp 307ndash310 2000

[117] J J Fuster S M Sanz-Gonzalez U M Moll and V AndresldquoClassic and novel roles of p53 prospects for anticancer ther-apyrdquo Trends in Molecular Medicine vol 13 no 5 pp 192ndash1992007

[118] J Boyer E G McLean S Aroori et al ldquoCharacterization of p53wild-type and null isogenic colorectal cancer cell lines resistantto 5-fluorouracil oxaliplatin and irinotecanrdquo Clinical CancerResearch vol 10 no 6 pp 2158ndash2167 2004

[119] T Kamijo J D Weber G Zambetti F Zindy M F Rousseland C J Sherr ldquoFunctional and physical interactions of theARF tumor suppressor with p53 and Mdm2rdquo Proceedings of theNational Academy of Sciences of the United States of Americavol 95 no 14 pp 8292ndash8297 1998

[120] J Feng R Tamaskovic Z Yang et al ldquoStabilization ofMdm2 viadecreased ubiquitination is mediated by protein kinase BAkt-dependent phosphorylationrdquo Journal of Biological Chemistryvol 279 no 34 pp 35510ndash35517 2004

[121] J I-J Leu P Dumont M Hafey M E Murphy and D LGeorge ldquoMitochondrial p53 activates Bak and causes disruptionof a Bak-Mcl1 complexrdquo Nature Cell Biology vol 6 no 5 pp443ndash450 2004

[122] M Mihara S Erster A Zaika et al ldquop53 has a direct apopto-genic role at the mitochondriardquoMolecular Cell vol 11 no 3 pp577ndash590 2003

[123] J E Chipuk T Kuwana L Bouchier-Hayes et al ldquoDirectactivation of Bax by p53 mediates mitochondrial membranepermeabilization and apoptosisrdquo Science vol 303 no 5660 pp1010ndash1014 2004

[124] G P Dotto ldquop21(WAF1Cip1) more than a break to the cellcyclerdquo Biochimica et Biophysica ActamdashReviews on Cancer vol1471 no 1 pp M43ndashM56 2000

[125] Q Zhan I T ChenM J Antinore andA J Fornace Jr ldquoTumorsuppressor p53 can participate in transcriptional induction ofthe GADD45 promoter in the absence of direct DNA bindingrdquoMolecular and Cellular Biology vol 18 pp 2768ndash2778 1998

[126] M Schuler and D R Green ldquoMechanisms of p53-dependentapoptosisrdquo Biochemical Society Transactions vol 29 no 6 pp684ndash688 2001

[127] J Yu L Zhang P M Hwang C Rago K W Kinzler and BVogelstein ldquoIdentification and classification of p53-regulatedgenesrdquo Proceedings of the National Academy of Sciences of theUnited States of America vol 96 no 25 pp 14517ndash14522 1999

[128] KHVousden ldquop53 death starrdquoCell vol 103 no 5 pp 691ndash6942000

[129] S Vossio E Palescandolo N Pediconi et al ldquoDN-p73 isactivated after DNA damage in a p53-dependent manner toregulate p53-induced cell cycle arrestrdquoOncogene vol 21 no 23pp 3796ndash3803 2002

[130] K Oda H Arakawa T Tanaka et al ldquop53AIP1 a potentialmediator of p53-dependent apoptosis and its regulation by ser-46-phosphorylated p53rdquo Cell vol 102 no 6 pp 849ndash862 2000

[131] Y Samuels-Lev D J OConnor D Bergamaschi et al ldquoASPPproteins specifically stimulate the apoptotic function of p53rdquoMolecular Cell vol 8 no 4 pp 781ndash794 2001

[132] M Ljungman ldquoDial 9-1-1 for p53 mechanisms of p53 activationby cellular stressrdquo Neoplasia vol 2 no 3 pp 208ndash225 2000

[133] J-T Liang K-C Huang Y-M Cheng et al ldquoP53 Overexpres-sion predicts poor chemosensitivity to high-dose 5-fluorouracilplus leucovorin chemotherapy for stage IV colorectal cancersafter palliative bowel resectionrdquo International Journal of Cancervol 97 no 4 pp 451ndash457 2002

[134] D J Ahnen P Feigl G Quan et al ldquoKi-ras mutation andp53 overexpression predict the clinical behavior of colorectalcancer a Southwest Oncology Group studyrdquo Cancer Researchvol 58 no 6 pp 1149ndash1158 1998

[135] A Paradiso G Simone S Petroni et al ldquoThymidilate synthaseand p53 primary tumour expression as predictive factors foradvanced colorectal cancer patientsrdquo The British Journal ofCancer vol 82 no 3 pp 560ndash567 2000

[136] S SjogrenM Inganas T Norberg et al ldquoThe p53 gene in breastcancer prognostic value of complementary DNA sequencingversus immunohistochemistryrdquo Journal of the National CancerInstitute vol 88 no 3-4 pp 173ndash182 1996

[137] E N Pugacheva A V Ivanov J E Kravchenko B P Kopnin AJ Levine and P M Chumakov ldquoNovel gain of function activityof p53 mutants activation of the dUTPase gene expressionleading to resistance to 5-fluorouracilrdquoOncogene vol 21 no 30pp 4595ndash4600 2002

[138] S Fan W S El-Deiry I Bae et al ldquop53 Gene mutations areassociated with decreased sensitivity of human lymphoma cellsto DNA damaging agentsrdquo Cancer Research vol 54 no 22 pp5824ndash5830 1994

[139] P Perego M Giarola S C Righetti et al ldquoAssociation betweencisplatin resistance and mutation of p53 gene and reduced baxexpression in ovarian carcinoma cell systemsrdquo Cancer Researchvol 56 no 3 pp 556ndash562 1996

[140] W M Gallagher M Cairney B Schott I B Roninson andR Brown ldquoIdentification of p53 genetic suppressor elementswhich confer resistance to cisplatinrdquo Oncogene vol 14 no 2pp 185ndash193 1997


[141] S Fan M L Smith D J Rivet II et al ldquoDisruption of p53function sensitizes breast cancer MCF-7 cells to cisplatin andpentoxifyllinerdquo Cancer Research vol 55 no 8 pp 1649ndash16541995

[142] D S Hawkins G W Demers and D A Galloway ldquoInactiva-tion of p53 enhances sensitivity to multiple chemotherapeuticagentsrdquo Cancer Research vol 56 no 4 pp 892ndash898 1996

[143] B A Goff J A Ries L P Els M D Coltrera and A MGown ldquoImmunophenotype of ovarian cancer as predictor ofclinical outcome evaluation at primary surgery and second-look procedurerdquo Gynecologic Oncology vol 70 no 3 pp 378ndash385 1998

[144] M K Hassan H Watari Y Han et al ldquoClusterin is a poten-tial molecular predictor for ovarian cancer patients survivaltargeting Clusterin improves response to paclitaxelrdquo Journal ofExperimental and Clinical Cancer Research vol 30 no 1 article113 2011

[145] S C Righetti G Della Torre S Pilotti et al ldquoA compara-tive study of p53 gene mutations protein accumulation andresponse to cisplatin-based chemotherapy in advanced ovariancarcinomardquo Cancer Research vol 56 no 4 pp 689ndash693 1996

[146] D Marx H Meden T Ziemek T Lenthe W Kuhn and ASchauer ldquoExpression of the p53 tumour suppressor gene as aprognostic marker in platinum-treated patients with ovariancancerrdquo European Journal of Cancer vol 34 no 6 pp 845ndash8501998

[147] D Mayr U Pannekamp G B Baretton et al ldquoImmunohis-tochemical analysis of drug resistance-associated proteins inovarian carcinomasrdquo Pathology Research and Practice vol 196no 7 pp 469ndash475 2000

[148] D A Dart S M Picksley P A Cooper J A Double and MC Bibby ldquoThe role of p53 in the chemotherapeutic responsesto cisplatin doxorubicin and 5-fluorouracil treatmentrdquo Interna-tional Journal of Oncology vol 24 no 1 pp 115ndash125 2004

[149] V Lam J P McPherson L Salmena et al ldquop53 gene status andchemosensitivity of childhood acute lymphoblastic leukemiacells to adriamycinrdquo Leukemia Research vol 23 no 10 pp 871ndash880 1999

[150] S Geisler P E Loslashnning T Aas et al ldquoInfluence of TP53gene alterations and c-erbB-2 expression on the response totreatment with doxorubicin in locally advanced breast cancerrdquoCancer Research vol 61 no 6 pp 2505ndash2512 2001

[151] I FichtnerW Slisow J Gill et al ldquoAnticancer drug response andexpression of molecular markers in early-passage xenotrans-planted colon carcinomasrdquo European Journal of Cancer vol 40no 2 pp 298ndash307 2004

[152] B R Jacob ldquoSurviving and thrivingrdquo Rehab Management vol15 no 1 pp 50ndash51 2002

[153] V Pavillard V Charasson A Laroche-Clary I Soubeyranand J Robert ldquoCellular parameters predictive of the clinicalresponse of colorectal cancers to irinotecan A Preliminarystudyrdquo Anticancer Research vol 24 no 2 pp 579ndash585 2004

[154] C Lavarino S Pilotti M Oggionni et al ldquop53 Gene statusand response to platinumpaclitaxel-based chemotherapy inadvanced ovarian carcinomardquo Journal of Clinical Oncology vol18 no 23 pp 3936ndash3945 2000

[155] MOhtsubo AMTheodoras J Schumacher JM Roberts andM Pagano ldquoHuman cyclin E a nuclear protein essential for theG1-to-S phase transitionrdquo Molecular and Cellular Biology vol15 no 5 pp 2612ndash2624 1995

[156] D Resnitzky and S I Reed ldquoDifferent roles for cyclins D1 and Ein regulation of the G1-to-S transitionrdquo Molecular and CellularBiology vol 15 no 7 pp 3463ndash3469 1995

[157] S Mazumder B Gong Q Chen J A Drazba J C Buchsbaumand A Almasan ldquoProteolytic cleavage of cyclin E leads toinactivation of associated kinase activity and amplificationof apoptosis in hematopoietic cellsrdquo Molecular and CellularBiology vol 22 no 7 pp 2398ndash2409 2002

[158] S Mazumder E L DuPree and A Almasan ldquoA dual role ofcyclin E in cell proliferation and apoptosis may provide a targetfor cancer therapyrdquo Current Cancer Drug Targets vol 4 no 1pp 65ndash75 2004

[159] S Mazumder D Plesca M Kinter and A Almasan ldquoInterac-tion of a cyclin E fragment with Ku70 regulates Bax-mediatedapoptosisrdquo Molecular and Cellular Biology vol 27 no 9 pp3511ndash3520 2007

[160] C Subramanian A W Opipari Jr X Bian V P Castle andR P S Kwok ldquoKu70 acetylation mediates neuroblastoma celldeath induced by histone deacetylase inhibitorsrdquo Proceedings ofthe National Academy of Sciences of the United States of Americavol 102 no 13 pp 4842ndash4847 2005

[161] J M Adams and S Cory ldquoThe Bcl-2 apoptotic switch in cancerdevelopment and therapyrdquo Oncogene vol 26 no 9 pp 1324ndash1337 2007

[162] S A Lakhani A Masud K Kuida et al ldquoCaspases 3 and 7 keymediators of mitochondrial events of apoptosisrdquo Science vol311 no 5762 pp 847ndash851 2006

[163] C Subramanian A W Opipari Jr V P Castle and R P SKwok ldquoHistone deacetylase inhibition induces apoptosis inneuroblastomardquo Cell Cycle vol 4 no 12 pp 1741ndash1743 2005

[164] H Y Cohen S Lavu K J Bitterman et al ldquoAcetylation of theC terminus of Ku70 by CBP and PCAF controls Bax-mediatedapoptosisrdquoMolecular Cell vol 13 no 5 pp 627ndash638 2004

[165] Y Ma H Lu K Schwarz and M R Lieber ldquoRepair of double-strand DNA breaks by the human non-homologous DNA endjoining pathway the iterative processing modelrdquo Cell Cycle vol4 no 9 pp 1193ndash1200 2005

[166] D Zhai F Luciano X Zhu B Guo A C Satterthwait and J CReed ldquoHumanin binds and nullifies bid activity by blocking itsactivation of Bax and Bakrdquo Journal of Biological Chemistry vol280 no 16 pp 15815ndash15824 2005

[167] A B Gustafsson J G Tsai S E Logue M T Crow and R AGottlieb ldquoApoptosis repressorwith caspase recruitment domainprotects against cell death by interfering with Bax activationrdquoJournal of Biological Chemistry vol 279 no 20 pp 21233ndash212382004

[168] Y-W Mao J-P Liu H Xiang and D W-C Li ldquoHuman120572A- and 120572B-crystallins bind to Bax and Bcl-Xs to sequestertheir translocation during staurosporine-induced apoptosisrdquoCell Death and Differentiation vol 11 no 5 pp 512ndash526 2004

[169] Y Deng and X Wu ldquoPeg3Pw1 promotes p53-mediated apop-tosis by inducing Bax translocation from cytosol to mitochon-driardquo Proceedings of the National Academy of Sciences of theUnited States of America vol 97 no 22 pp 12050ndash12055 2000

[170] Y Takahashi M Karbowski H Yamaguchi et al ldquoLoss of Bif-1suppresses BaxBak conformational change and mitochondrialapoptosisrdquo Molecular and Cellular Biology vol 25 no 21 pp9369ndash9382 2005

[171] T Ohtsuka H Ryu Y A Minamishima et al ldquoASC is a Baxadaptor and regulates the p53-Bax mitochondrial apoptosispathwayrdquo Nature Cell Biology vol 6 no 2 pp 121ndash128 2004


[172] M D Vos A Dallol K Eckfeld et al ldquoThe RASSF1A tumorsuppressor activates bax via MOAP-1rdquo Journal of BiologicalChemistry vol 281 no 8 pp 4557ndash4563 2006

[173] H H Park E Logette S Raunser et al ldquoDeath domainassemnotbly mechanism revealed by crystal structure of theoligomeric PIDDosome core complexrdquo Cell vol 128 no 3 pp533ndash546 2007

[174] A Sekiyama H Ueda S-I Kashiwamura et al ldquoA stress-induced superoxide-mediated caspase-1 activation pathwaycauses plasma IL-18 upregulationrdquo Immunity vol 22 no 6 pp669ndash677 2005

[175] MWoo R Hakem C Furlonger et al ldquoCaspase-3 regulates cellcycle in B cells a consequence of substrate specificityrdquo NatureImmunology vol 4 no 10 pp 1016ndash1022 2003

[176] D R Beisner I L Chen R V Kolla A Hoffmann and S MHedrick ldquoCutting edge innate immunity conferred by B cells isregulated by caspase-8rdquo Journal of Immunology vol 175 no 6pp 3469ndash3473 2005

[177] R P Rastogi andR P Sinha ldquoApoptosis molecularmechanismsand pathogenicityrdquo EXCLI Journal vol 8 pp 155ndash181 2009

[178] J T Reardon A Vaisman S G Chaney and A SancarldquoEfficient nucleotide excision repair of cisplatin oxaliplatin andbis-acetoammine-dichloro-cyclohexylamine-platinum(IV)(JM216) platinum intrastrand DNA diadductsrdquo CancerResearch vol 59 no 16 pp 3968ndash3971 1999

[179] T Furuta T Ueda G Aune A Sarasin K H Kraemer andY Pommier ldquoTranscription-coupled nucleotide excision repairas a determinant of cisplatin sensitivity of human cellsrdquo CancerResearch vol 62 no 17 pp 4899ndash4902 2002

[180] E Reed ldquoPlatinum-DNAadduct nucleotide excision repair andplatinum based anti-cancer chemotherapyrdquo Cancer TreatmentReviews vol 24 no 5 pp 331ndash344 1998

[181] K B Lee R J Parker V Bohr T Cornelison and E ReedldquoCisplatin sensitivityresistance in UV repair-deficient Chinesehamster ovary cells of complementation groups 1 and 3rdquoCarcinogenesis vol 14 no 10 pp 2177ndash2180 1993

[182] D W Melton A-M Ketchen F Nunez et al ldquoCells fromERCC1-deficient mice show increased genome instability anda reduced frequency of S-phase-dependent illegitimate chro-mosome exchange but a normal frequency of homologousrecombinationrdquo Journal of Cell Science vol 111 no 3 pp 395ndash404 1998

[183] C K Youn M H Kim H J Cho et al ldquoOncogenic H-Ras up-regulates expression of ERCC1 to protect cells from platinum-based anticancer agentsrdquo Cancer Research vol 64 pp 4849ndash4857 2004

[184] M Dabholkar J Vionnet F Bostick-Bruton J J Yu andE Reed ldquoMessenger RNA levels of XPAC and ERCC1 inovarian cancer tissue correlate with response to platinum-basedchemotherapyrdquo Journal of Clinical Investigation vol 94 no 2pp 703ndash708 1994

[185] R Metzger C G Leichman K D Danenberg et al ldquoERCC1mRNA levels complement thymidylate synthase mRNA levelsin predicting response and survival for gastric cancer patientsreceiving combination cisplatin and fluorouracil chemother-apyrdquo Journal of Clinical Oncology vol 16 no 1 pp 309ndash3161998

[186] R V N Lord J Brabender D Gandara et al ldquoLow ERRC1expression correlates with prolonged survival after cisplatinplus gemcitabine chemotherapy in non-small cell lung cancerrdquoClinical Cancer Research vol 8 no 7 pp 2286ndash2291 2002

[187] Y Shirota J Stoehlmacher J Brabender et al ldquoERCC1 andthymidylate synthase mRNA levels predict survival for col-orectal cancer patients receiving combination oxaliplatin andfluorouracil chemotherapyrdquo Journal of Clinical Oncology vol 19no 23 pp 4298ndash4304 2001

[188] M Selvakumaran D A Pisarcik R Bao A T Yeung and TC Hamilton ldquoEnhanced cisplatin cytotoxicity by disturbing thenucleotide excision repair pathway in ovarian cancer cell linesrdquoCancer Research vol 63 no 6 pp 1311ndash1316 2003

[189] J A Houghton DM Tillman and F G Harwood ldquoRatio of 21015840-Deoxyadenosine-51015840-triphosphatethymidine-51015840-triphosphateinfluences the commitment of human colon carcinoma cells tothymineless deathrdquo Clinical Cancer Research vol 1 no 7 pp723ndash730 1995

[190] G W Aherne A Hardcastle F Raynaud and A L Jack-man ldquoImmunoreactive dUMP and TTP pools as an index ofthymidylate synthase inhibition effect of tomudex (ZD1694)and a nonpolyglutamated quinazoline antifolate (CB30900) inL1210 mouse leukaemia cellsrdquo Biochemical Pharmacology vol51 no 10 pp 1293ndash1301 1996

[191] T Lindahl ldquoAn N glycosidase from Escherichia coli thatreleases free uracil from DNA containing deaminated cytosineresiduesrdquo Proceedings of the National Academy of Sciences of theUnited States of America vol 71 no 9 pp 3649ndash3653 1974

[192] R D Ladner ldquoThe role of dUTPase and uracil-DNA repair incancer chemotherapyrdquo Current Protein and Peptide Science vol2 no 4 pp 361ndash370 2001

[193] S D Webley A Hardcastle R D Ladner A L Jackmanand G W Aherne ldquoDeoxyuridine triphosphatase (dUTPase)expression and sensitivity to the thymidylate synthase (TS)inhibitor ZD9331rdquo The British Journal of Cancer vol 83 no 6pp 792ndash799 2000

[194] S DWebley S JWelsh A L Jackman and GW Aherne ldquoTheability to accumulate deoxyuridine triphosphate and cellularresponse to thymidylate synthase (TS) inhibitionrdquo The BritishJournal of Cancer vol 85 no 3 pp 446ndash452 2001

[195] D Fink S Aebi and S B Howell ldquoThe role of DNA mismatchrepair in drug resistancerdquo Clinical Cancer Research vol 4 no 1pp 1ndash6 1998

[196] K A D Narine A M Keuling R Gombos V A Tron SE Andrew and L C Young ldquoDefining the DNA mismatchrepair-dependent apoptotic pathway in primary cells evidencefor p53-independence and involvement of centrosomal caspase2rdquo DNA Repair vol 9 no 2 pp 161ndash168 2010

[197] J-P Issa ldquoThe epigenetics of colorectal cancerrdquo Annals of theNew York Academy of Sciences vol 910 pp 140ndash155 2000

[198] B L King M-L Carcangiu D Carter et al ldquoMicrosatelliteinstability in ovarian neoplasmsrdquoThe British Journal of Cancervol 72 no 2 pp 376ndash382 1995

[199] T G Paulson F A Wright B A Parker V Russack andG M Wahl ldquoMicrosatellite instability correlates with reducedsurvival and poor disease prognosis in breast cancerrdquo CancerResearch vol 56 no 17 pp 4021ndash4026 1996

[200] K K Herfarth T P Brent R P Danam et al ldquoA specific CpGmethylation pattern of the MGMT promoter region associatedwith reducedMGMT expression in primary colorectal cancersrdquoMolecular Carcinogenesis vol 24 pp 90ndash98 1999

[201] R Fishel and R D Kolodner ldquoIdentification of mismatch repairgenes and their role in the development of cancerrdquo CurrentOpinion in Genetics and Development vol 5 no 3 pp 382ndash3951995


[202] J A Plumb G Strathdee J Sludden S B Kaye and R BrownldquoReversal of drug resistance in human tumor xenografts by21015840-deoxy-5-azacytidine-induced demethylation of the hMLH1gene promoterrdquoCancer Research vol 60 no 21 pp 6039ndash60442000

[203] Y Watanabe M Koi H Hemmi H Hoshai and K Noda ldquoAchange in microsatellite instability caused by cisplatin-basedchemotherapy of ovarian cancerrdquoThe British Journal of Cancervol 85 no 7 pp 1064ndash1069 2001

[204] D Fallik F Borrini V Boige et al ldquoMicrosatellite instability is apredictive factor of the tumor response to irinotecan in patientswith advanced colorectal cancerrdquo Cancer Research vol 63 no18 pp 5738ndash5744 2003

[205] E C Friedberg G C Walker W Siede R D Wood R ASchultz and T EllenbergerDNA Repair andMutagenesis ASMPress Washington DC USA 2006

[206] E C Friedberg ldquoDNA damage and repairrdquoNature vol 421 no6921 pp 436ndash440 2003

[207] R D Kennedy J E Quinn P B Mullan P G Johnston andD P Harkin ldquoThe role of BRCA1 in the cellular response tochemotherapyrdquo Journal of the National Cancer Institute vol 96no 22 pp 1659ndash1668 2004

[208] Y Wang D Cortez P Yazdi N Neff S J Elledge and J QinldquoBASC a super complex of BRCA1-associated proteins involvedin the recognition and repair of aberrant DNA structuresrdquoGenes and Development vol 14 no 8 pp 927ndash939 2000

[209] R I Yarden S Pardo-Reoyo M Sgagias K H Cowan and LC Brody ldquoBRCA1 regulates the G2M checkpoint by activatingChk1 kinase upon DNA damagerdquo Nature Genetics vol 30 no3 pp 285ndash289 2002

[210] P B Mullan J E Quinn P M Gilmore et al ldquoBRCA1 andGADD45 mediated G2M cell cycle arrest in response toantimicrotubule agentsrdquo Oncogene vol 20 no 43 pp 6123ndash6131 2001

[211] D P Harkin ldquoUncovering functionally relevant signaling path-ways using microarray-based expression profilingrdquo Oncologistvol 5 no 6 pp 501ndash507 2000

[212] J E Quinn R D Kennedy P B Mullan et al ldquoBRCA1functions as a differential modulator of chemotherapy-inducedapoptosisrdquo Cancer Research vol 63 no 19 pp 6221ndash6228 2003

[213] G Guo F Zhang R Gao R Delsite Z Feng and S N PowellldquoDNA repair and synthetic lethalityrdquo International Journal ofOral Science vol 3 no 4 pp 176ndash179 2011

[214] S Thode A Schafer P Pfeiffer and W Vielmetter ldquoA novelpathway of DNA end-to-end joiningrdquo Cell vol 60 no 6 pp921ndash928 1990

[215] P Baumann and S C West ldquoDNA end-joining catalyzed byhuman cell-free extractsrdquo Proceedings of the National Academyof Sciences of the United States of America vol 95 no 24 pp14066ndash14070 1998

[216] M J Difilippantonio J Zhu H T Chen et al ldquoDNA repair pro-tein Ku80 suppresses chromosomal aberrations and malignanttransformationrdquo Nature vol 404 no 6777 pp 510ndash514 2000

[217] R B Cary S R Peterson J Wang D G Bear E M Bradburyand D J Chen ldquoDNA looping by Ku and the DNA-dependentprotein kinaserdquo Proceedings of the National Academy of Sciencesof the United States of America vol 94 no 9 pp 4267ndash42721997

[218] D A Ramsden and M Geliert ldquoKu protein stimulates DNAend joining by mammalian DNA ligases a direct role for Kuin repair of DNA double-strand breaksrdquo EMBO Journal vol 17no 2 pp 609ndash614 1998

[219] T Mimori M Akizuki H Yamagata S Inada S Yoshidaand M Homma ldquoCharacterization of a high molecular weightacidic nuclear protein recognized by autoantibodies in serafrom patients with polymyositis-scleroderma overlaprdquo Journalof Clinical Investigation vol 68 no 3 pp 611ndash620 1981

[220] G C Li H Ouyang X Li et al ldquoKu70 a candidate tumorsuppressor gene for murine T cell lymphomardquo Molecular Cellvol 2 no 1 pp 1ndash8 1998

[221] R Tuteja and N Tuteja ldquoKu autoantigen a multifunctionalDNA-binding proteinrdquo Critical Reviews in Biochemistry andMolecular Biology vol 35 no 1 pp 1ndash33 2000

[222] C Gullo M Au G Feng and G Teoh ldquoThe biology of Ku andits potential oncogenic role in cancerrdquo Biochimica et BiophysicaActamdashReviews on Cancer vol 1765 no 2 pp 223ndash234 2006

[223] M Sawada W Sun P Hayes K Leskov D A Boothman andS Matsuyama ldquoKu70 suppresses the apoptotic translocation ofbax to mitochondriardquoNature Cell Biology vol 5 no 4 pp 320ndash329 2003

[224] A Kashishian H Douangpanya D Clark et al ldquoDNA-dependent protein kinase inhibitors as drug candidates for thetreatment of cancerrdquoMolecular Cancer Therapeutics vol 2 no12 pp 1257ndash1264 2003

[225] V L Gabai A B Meriin D D Mosser et al ldquoHsp70 preventsactivation of stress kinases a novel pathway of cellular thermo-tolerancerdquo Journal of Biological Chemistry vol 272 no 29 pp18033ndash18037 1997

[226] A Samali and T G Cotter ldquoHeat shock proteins increaseresistance to apoptosisrdquoExperimental Cell Research vol 223 no1 pp 163ndash170 1996

[227] G C Li F He X Shao et al ldquoAdenovirus-mediated heat-activated antisense Ku70 expression radiosensitizes tumor cellsin vitro and in vivordquo Cancer Research vol 63 no 12 pp 3268ndash3274 2003

[228] Y-T Tai K Podar S-K Kraeft et al ldquoTranslocation ofKu86Ku70 to the multiple myeloma cell membrane functionalimplicationsrdquo Experimental Hematology vol 30 no 3 pp 212ndash220 2002

[229] I S Ayene L P Ford and C J Koch ldquoKu protein targetingby Ku70 small interfering RNA enhances human cancer cellresponse to topoisomerase II inhibitor and 120574 radiationrdquoMolec-ular Cancer Therapeutics vol 4 no 4 pp 529ndash536 2005

[230] C-S Chen Y-C Wang H-C Yang et al ldquoHistone deacetylaseinhibitors sensitize prostate cancer cells to agents that produceDNA double-strand breaks by targeting Ku70 acetylationrdquoCancer Research vol 67 no 11 pp 5318ndash5327 2007

[231] A Munshi J F Kurland T Nishikawa et al ldquoHistone deacety-lase inhibitors radiosensitize human melanoma cells by sup-pressing DNA repair activityrdquo Clinical Cancer Research vol 11no 13 pp 4912ndash4922 2005

[232] M K Hassan H Watari A E Salah-Eldin et al ldquoHistonedeacetylase inhibitors sensitize lung cancer cells to hyperther-mia involvement of Ku70SirT-1 in thermo-protectionrdquo PLoSONE vol 9 no 4 Article ID e94213 2014

[233] D R Green and J C Reed ldquoMitochondria and apoptosisrdquoScience vol 281 no 5381 pp 1309ndash1312 1998

[234] A Ashkenazi ldquoTargeting the extrinsic apoptosis pathway incancerrdquo Cytokine and Growth Factor Reviews vol 19 no 3-4pp 325ndash331 2008

[235] Y Ito P Pandey A Place et al ldquoThe novel triterpenoid 2-cyano-312-dioxoolean-19-dien-28-oic acid induces apoptosisof human myeloid leukemia cells by a caspase-8-dependent


mechanismrdquo Cell Growth and Differentiation vol 11 no 5 pp261ndash267 2000

[236] K B Kim R Lotan P Yue et al ldquoIdentification of a novelsynthetic triterpenoid methyl-2-cyano-312-dioxooleana-19-dien-28-oate that potently induces caspase-mediated apoptosisin human lung cancer cellsrdquoMolecular CancerTherapeutics vol1 no 3 pp 177ndash184 2002

[237] I M Pedersen S Kitada A Schimmer et al ldquoThe triterpenoidCDDO induces apoptosis in refractory CLL B cellsrdquo Blood vol100 no 8 pp 2965ndash2972 2002

[238] L Cartee R Smith Y Dai et al ldquoSynergistic induction ofapoptosis in human myeloid leukemia cells by phorbol 12-myristate 13-acetate and flavopiridol proceeds via activation ofboth the intrinsic and tumor necrosis factor-mediated extrinsiccell death pathwaysrdquoMolecular Pharmacology vol 61 no 6 pp1313ndash1321 2002

[239] L Altucci andHGronemeyer ldquoNuclear receptors in cell life anddeathrdquo Trends in Endocrinology and Metabolism vol 12 no 10pp 460ndash468 2001

[240] F A E Kruyt ldquoTRAIL and cancer therapyrdquo Cancer Letters vol263 no 1 pp 14ndash25 2008

[241] D Mahalingam E Szegezdi M Keane S D Jong and ASamali ldquoTRAIL receptor signalling and modulation are we onthe right TRAILrdquo Cancer Treatment Reviews vol 35 no 3 pp280ndash288 2009

[242] G Brumatti M Salmanidis and P G Ekert ldquoCrossing pathsinteractions between the cell death machinery and growthfactor survival signalsrdquoCellular andMolecular Life Sciences vol67 no 10 pp 1619ndash1630 2010

[243] V Duronio ldquoThe life of a cell apoptosis regulation by thePI3KPKB pathwayrdquo Biochemical Journal vol 415 no 3 pp333ndash344 2008

[244] T Gallenne F Gautier L Oliver et al ldquoBax activation bythe BH3-only protein Puma promotes cell dependence onantiapoptotic Bcl-2 family membersrdquo Journal of Cell Biologyvol 185 no 2 pp 279ndash290 2009

[245] A Letai ldquoPuma strikes Baxrdquo Journal of Cell Biology vol 185 no2 pp 189ndash191 2009

[246] M Karin Y Cao F R Greten and Z-W Li ldquoNF-120581B in cancerfrom innocent bystander to major culpritrdquo Nature ReviewsCancer vol 2 no 4 pp 301ndash310 2002

[247] A S Baldwin ldquoControl of oncogenesis and cancer therapyresistance by the transcription factor NF-120581Brdquo Journal of ClinicalInvestigation vol 107 no 3 pp 241ndash246 2001

[248] B Leber J Lin and D W Andrews ldquoEmbedded together thelife and death consequences of interaction of the Bcl-2 familywith membranesrdquo Apoptosis vol 12 no 5 pp 897ndash911 2007

[249] S Fulda ldquoInhibitor of apoptosis proteins in hematologicalmalignanciesrdquo Leukemia vol 23 no 3 pp 467ndash476 2009

[250] M P Boldin I L Mett E E Varfolomeev et al ldquoSelf-association of the death domainsof the p55 tumor necrosisfactor (TNF) receptor and FasAPO1 prompts signaling for TNFand FasAPO1 effectsrdquo Journal of Biological Chemistry vol 270no 1 pp 387ndash391 1995

[251] S-E Chuang P-Y Yeh Y-S Lu et al ldquoBasal levels and patternsof anticancer drug-induced activation of nuclear factor-120581B (NF-120581B) and its attenuation by tamoxifen dexamethasone andcurcumin in carcinoma cellsrdquo Biochemical Pharmacology vol63 no 9 pp 1709ndash1716 2002

[252] M M M Abdel-Latif J ORiordan H J Windle et al ldquoNF-120581B activation in esophageal adenocarcinoma relationship to

Barretts metaplasia survival and response to neoadjuvantchemoradiotherapyrdquo Annals of Surgery vol 239 no 4 pp 491ndash500 2004

[253] A Arlt A Gehrz S Muerkoster et al ldquoRole of NF-120581B andAktPI3K in the resistance of pancreatic carcinoma cell linesagainst gemcitabine-induced cell deathrdquo Oncogene vol 22 no21 pp 3243ndash3251 2003

[254] TKatoDCDuffey FGOndrey et al ldquoCisplatin and radiationsensitivity in human head and neck squamous carcinomasare independently modulated by glutathione and transcriptionfactor NF-kappaBrdquo Head amp Neck vol 22 pp 748ndash759 2000

[255] J C Cusack Jr ldquoRationale for the treatment of solid tumorswith the proteasome inhibitor bortezomibrdquo Cancer TreatmentReviews vol 29 no 1 pp 21ndash31 2003

[256] P Richardson ldquoClinical update proteasome inhibitors inhematologic malignanciesrdquo Cancer Treatment Reviews vol 29supplement 1 pp 33ndash39 2003

[257] E C LaCasse D J Mahoney H H Cheung S Plenchette SBaird and R G Korneluk ldquoIAP-targeted therapies for cancerrdquoOncogene vol 27 no 48 pp 6252ndash6275 2008

[258] S Fulda ldquoTargeting inhibitor of apoptosis proteins (IAPs) forcancer therapyrdquoAnti-Cancer Agents inMedicinal Chemistry vol8 no 5 pp 533ndash539 2008

[259] S Fulda ldquoTumor resistance to apoptosisrdquo International Journalof Cancer vol 124 no 3 pp 511ndash515 2009

[260] R Mannhold S Fulda and E Carosati ldquoIAP antagonistspromising candidates for cancer therapyrdquo Drug DiscoveryToday vol 15 no 5-6 pp 210ndash219 2010

[261] K A Whitehead R Langer and D G Anderson ldquoKnockingdown barriers advances in siRNA deliveryrdquo Nature ReviewsDrug Discovery vol 8 no 2 pp 129ndash138 2009

[262] M E Davis ldquoThe first targeted delivery of siRNA in humans viaa self-assembling cyclodextrin polymer-based nanoparticlefrom concept to clinicrdquo Molecular Pharmaceutics vol 6 no 3pp 659ndash668 2009

[263] M Baker ldquoRNA interference homing in on deliveryrdquo Naturevol 464 no 7292 pp 1225ndash1228 2010

[264] M E Davis J E Zuckerman C H J Choi et al ldquoEvidenceof RNAi in humans from systemically administered siRNA viatargeted nanoparticlesrdquo Nature vol 464 no 7291 pp 1067ndash1070 2010

[265] B M Ryan N OrsquoDonovan and M J Duffy ldquoSurvivin anewtarget for anti-cancer therapyrdquo Cancer Treatment Reviewsvol 35 pp 553ndash562 2009

[266] D Picard ldquoHeat-shock protein 90 a chaperone for folding andregulationrdquo Cellular and Molecular Life Sciences vol 59 no 10pp 1640ndash1648 2002

[267] LWhitesell and S L Lindquist ldquoHSP90 and the chaperoning ofcancerrdquoNature Reviews Cancer vol 5 no 10 pp 761ndash772 2005

[268] L Neckers and K Neckers ldquoHeat-shock protein 90 inhibitorsas novel cancer chemotherapeutic agentsrdquo Expert Opinion onEmerging Drugs vol 7 no 2 pp 277ndash288 2002

[269] L Neckers ldquoHeat shock protein 90 is a rational molecular targetin breast cancerrdquo Breast Disease vol 15 pp 53ndash60 2002

[270] LNeckers ldquoHsp90 inhibitors as novel cancer chemotherapeuticagentsrdquo Trends in Molecular Medicine vol 8 no 4 supplementpp S55ndashS61 2002

[271] N Sato T Yamamoto Y Sekine et al ldquoInvolvement of heat-shock protein 90 in the interleukin-6-mediated signaling path-way through STAT3rdquo Biochemical and Biophysical ResearchCommunications vol 300 no 4 pp 847ndash852 2003


[272] C S Mitsiades N S Mitsiades C J McMullan et alldquoAntimyeloma activity of heat shock protein-90 inhibitionrdquoBlood vol 107 no 3 pp 1092ndash1100 2006

[273] M Chatterjee S Jain T Stuhmer et al ldquoSTAT3 and MAPKsignaling maintain overexpression of heat shock proteins 90120572and 120573 in multiple myeloma cells which critically contribute totumor-cell survivalrdquo Blood vol 109 no 2 pp 720ndash728 2007

[274] T W Schulte M V Blagosklonny C Ingui and L NeckersldquoDisruption of the Raf-1-Hsp90 molecular complex resultsin destabilization of Raf-1 and loss of Raf-1-Ras associationrdquoJournal of Biological Chemistry vol 270 no 41 pp 24585ndash24588 1995

[275] S Sato N Fujita and T Tsuruo ldquoModulation of Akt kinaseactivity by binding to Hsp90rdquo Proceedings of the NationalAcademy of Sciences of the United States of America vol 97 no20 pp 10832ndash10837 2000

[276] E E A Bull H Dote K J Brady et al ldquoEnhancedtumor cell radiosensitivity and abrogation of G2 and S phasearrest by the Hsp90 inhibitor 17-(dimethylaminoethylamino)-17-demethoxygeldanamycinrdquo Clinical Cancer Research vol 10no 23 pp 8077ndash8084 2004

[277] K F Pirollo Z Hao A Rait C W Ho and E H ChangldquoEvidence supporting a signal transduction pathway leadingto the radiation-resistant phenotype in human tumor cellsrdquoBiochemical andBiophysical ResearchCommunications vol 230no 1 pp 196ndash201 1997

[278] A K Gupta V J Bakanauskas G J Cerniglia et al ldquoThe rasradiation resistance pathwayrdquo Cancer Research vol 61 no 10pp 4278ndash4282 2001

[279] S Tanno N Yanagawa A Habiro et al ldquoSerinethreoninekinase AKT is frequently activated in human bile duct can-cer and is associated with increased radioresistancerdquo CancerResearch vol 64 no 10 pp 3486ndash3490 2004

[280] K S Bisht C M Bradbury D Mattson et al ldquoGeldanamycinand 17-allylamino-17-demethoxygeldanamycin potentiate the invitro and in vivo radiation response of cervical tumor cells viathe heat shock protein 90-mediated intracellular signaling andcytotoxicityrdquo Cancer Research vol 63 no 24 pp 8984ndash89952003

[281] H Machida Y Matsumoto M Shirai and N Kubota ldquoGel-danamycin an inhibitor of Hsp90 sensitizes human tumourcells to radiationrdquo International Journal of Radiation Biologyvol 79 no 12 pp 973ndash980 2003

[282] J S Russell W Burgan K A Oswald K Camphausen andP J Tofilon ldquoEnhanced cell killing induced by the combina-tion of radiation and the heat shock protein 90 inhibitor 17-allylamino-17-demethoxygeldanamycin amultitarget approachto radiosensitizationrdquo Clinical Cancer Research vol 9 no 10 Ipp 3749ndash3755 2003

[283] K Harashima T Akimoto T Nonaka K Tsuzuki N Mit-suhashi and T Nakano ldquoHeat shock protein 90 (Hsp90)chaperone complex inhibitor Radicicol potentiated radiation-induced cell killing in a hormone-sensitive prostate cancer cellline through degradation of the androgen receptorrdquo Interna-tional Journal of Radiation Biology vol 81 no 1 pp 63ndash76 2005

[284] H Dote W E Burgan K Camphausen and P J TofilonldquoInhibition of Hsp90 compromises the DNA damage responseto radiationrdquo Cancer Research vol 66 no 18 pp 9211ndash92202006

[285] A E Kabakov Y V Malyutina and D S Latchman ldquoHsf1-mediated stress response can transiently enhance cellular

radioresistancerdquoRadiation Research vol 165 no 4 pp 410ndash4232006

[286] Y-C Wu W-Y Yen T-C Lee and L-H Yih ldquoHeat shockprotein inhibitors 17-DMAG and KNK437 enhance arsenictrioxide-induced mitotic apoptosisrdquo Toxicology and AppliedPharmacology vol 236 no 2 pp 231ndash238 2009

[287] R Enmon W-H Yang A M Ballangrud et al ldquoCombinationtreatment with 17-N-allylamino-17-demethoxy geldanamycinand acute irradiation produces supra-additive growth suppres-sion in human prostate carcinoma spheroidsrdquo Cancer Researchvol 63 no 23 pp 8393ndash8399 2003

[288] L R Kelland ldquoSmall molecule anticancer drugsrdquo IDrugs vol 2no 6 pp 550ndash552 1999

[289] J L Eiseman J Lan T F Lagattuta et al ldquoPharmacokineticsand pharmacodynamics of 17-demethoxy 17-[[(2-dimethylamino)ethyl]amino]geldanamycin (17DMAGNSC 707545) in CB-17 SCID mice bearing MDA-MB-231human breast cancer xenograftsrdquo Cancer Chemotherapy andPharmacology vol 55 no 1 pp 21ndash32 2005

[290] P A Brough W Aherne X Barril et al ldquo45-DiarylisoxazoleHsp90 chaperone inhibitors potential therapeutic agents for thetreatment of cancerrdquo Journal of Medicinal Chemistry vol 51 no2 pp 196ndash218 2008

[291] S A Eccles A Massey F I Raynaud et al ldquoNVP-AUY922 anovel heat shock protein 90 inhibitor active against xenografttumor growth angiogenesis and metastasisrdquo Cancer Researchvol 68 no 8 pp 2850ndash2860 2008

[292] P A Brough X Barril J Borgognoni et al ldquoCombin-ing hit identification strategies fragment-based and in silicoapproaches to orally active 2-aminothieno[23-d]pyrimidineinhibitors of theHsp90molecular chaperonerdquo Journal ofMedic-inal Chemistry vol 52 no 15 pp 4794ndash4809 2009

[293] L Stingl T Stuhmer M Chatterjee M R Jensen M Flentjeand C S Djuzenova ldquoNovel HSP90 inhibitors NVP-AUY922and NVP-BEP800 radiosensitise tumour cells through cell-cycle impairment increased DNA damage and repair protrac-tionrdquoTheBritish Journal of Cancer vol 102 no 11 pp 1578ndash15912010

[294] I P Trougakos A So B Jansen M E Gleave and E SGonos ldquoSilencing expression of the clusterinapolipoproteinj gene in human cancer cells using small interfering RNAinduces spontaneous apoptosis reduced growth ability and cellsensitization to genotoxic andoxidative stressrdquoCancer Researchvol 64 no 5 pp 1834ndash1842 2004

[295] B ShannanM Seifert K Leskov et al ldquoChallenge and promiseroles for clusterin in pathogenesis progression and therapy ofcancerrdquo Cell Death and Differentiation vol 13 no 1 pp 12ndash192006

[296] H Miyake M Muramaki T Kurahashi et al ldquoExpression ofclusterin in prostate cancer correlates with gleason score but notwith prognosis in patients undergoing radical prostatectomywithout neoadjuvant hormonal therapyrdquo Urology vol 68 no3 pp 609ndash614 2006

[297] J Steinberg R Oyasu S Lang et al ldquoIntracellular levels of SGP-2 (Clusterin) correlate with tumor grade in prostate cancerrdquoClinical Cancer Research vol 3 no 10 pp 1707ndash1711 1997

[298] K Parczyk C Pilarsky U Rachel and C Koch-Brandt ldquoGp80(clusterin TRPM-2) mRNA level is enhanced in human renalclear cell carcinomasrdquo Journal of Cancer Research and ClinicalOncology vol 120 no 3 pp 186ndash188 1994

[299] M Redondo E Villar J Torres-Munoz T Tellez M Morelland C K Petito ldquoOverexpression of clusterin in human breast


carcinomardquo The American Journal of Pathology vol 157 no 2pp 393ndash399 2000

[300] D Xie H L Sze J S T Sham et al ldquoUp-regulated expressionof cytoplasmic clusterin in human ovarian carcinomardquo Cancervol 103 no 2 pp 277ndash283 2005

[301] S Pucci E Bonanno F Pichiorri C Angeloni and L GSpagnoli ldquoModulation of different clusterin isoforms in humancolon tumorigenesisrdquo Oncogene vol 23 no 13 pp 2298ndash23042004

[302] L V July E Beraldi A So et al ldquoNucleotide-based ther-apies targeting clusterin chemosensitize human lung adeno-carcinoma cells both in vitro and in vivordquo Molecular CancerTherapeutics vol 3 no 3 pp 223ndash232 2004

[303] N Mourra A Couvelard E Tiret S Olschwang andJ-F Flejou ldquoClusterin is highly expressed in pancreaticendocrine tumours but not in solid pseudopapillary tumoursrdquoHistopathology vol 50 no 3 pp 331ndash337 2007

[304] H Watari Y Ohta M K Hassan Y Xiong S Tanaka andN Sakuragi ldquoClusterin expression predicts survival of invasivecervical cancer patients treated with radical hysterectomy andsystematic lymphadenectomyrdquo Gynecologic Oncology vol 108pp 527ndash532 2008

[305] M Danik J-G Chabot C Mercier et al ldquoHuman gliomasand epileptic foci express high levels of a mRNA related to rattesticular sulfated glycoprotein 2 a purported marker of celldeathrdquo Proceedings of the National Academy of Sciences of theUnited States of America vol 88 no 19 pp 8577ndash8581 1991

[306] A Wellmann C Thieblemont S Pittaluga et al ldquoDetectionof differentially expressed genes in lymphomas using cDNAarrays identification of clusterin as a new diagnostic marker foranaplastic large-cell lymphomasrdquo Blood vol 96 no 2 pp 398ndash404 2000

[307] M Gleave and H Miyake ldquoUse of antisense oligonucleotidestargeting the cytoprotective gene clusterin to enhanceandrogen- and chemo-sensitivity in prostate cancerrdquo WorldJournal of Urology vol 23 no 1 pp 38ndash46 2005

[308] M E Gleave and B P Monia ldquoAntisense therapy for cancerrdquoNature Reviews Cancer vol 5 no 6 pp 468ndash479 2005

[309] H Miyake I Hara S Kamidono and M E Gleave ldquoSyn-ergistic chemsensitization and inhibition of tumor growthand metastasis by the antisense oligodeoxynucleotide targetingclusterin gene in a human bladder cancer modelrdquo ClinicalCancer Research vol 7 no 12 pp 4245ndash4252 2001

[310] I P Trougakos and E S Gonos ldquoClusterinApolipoprotein J inhuman aging and cancerrdquo International Journal of Biochemistryand Cell Biology vol 34 no 11 pp 1430ndash1448 2002

[311] M Gleave and B Jansen ldquoClusterin and IGFBPs as antisensetargets in prostate cancerrdquo Annals of the New York Academy ofSciences vol 1002 pp 95ndash104 2003

[312] T Criswell M Beman S Araki et al ldquoDelayed activation ofinsulin-like growth factor-1 receptorSrc MAPKEgr-1 signal-ing regulates clusterin expression a pro-survival factorrdquo Journalof Biological Chemistry vol 280 no 14 pp 14212ndash14221 2005

[313] T Zellweger H Miyake S Cooper et al ldquoAntitumor activityof antisense clusterin oligonucleotides is improved in vitro andin vivo by incorporation of 21015840-O-(2-methoxy) ethyl chemistryrdquoJournal of Pharmacology and Experimental Therapeutics vol298 no 3 pp 934ndash940 2001

[314] A Biroccio C DAngelo B Jansen M E Gleave and GZupi ldquoAntisense clusterin oligodeoxynucleotides increase theresponse of HER-2 gene amplified breast cancer cells to

Trastuzumabrdquo Journal of Cellular Physiology vol 204 no 2 pp463ndash469 2005

[315] M John A Hinke M Stauch et al ldquoWeekly paclitaxel plustrastuzumab in metastatic breast cancer pretreated with anth-racyclinesmdasha phase II multipractice studyrdquo BMC Cancer vol12 article 165 2012

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Anatomy Research International

PeptidesInternational Journal of


Hindawi Publishing Corporation httpwwwhindawicom

International Journal of

Volume 2014

Zoology


Molecular Biology International

GenomicsInternational Journal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014


BioinformaticsAdvances in

Marine BiologyJournal of



Signal TransductionJournal of


BioMed Research International

Evolutionary BiologyInternational Journal of



Biochemistry Research International

ArchaeaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014


Genetics Research International


Advances in

Virolog y

Hindawi Publishing Corporationhttpwwwhindawicom

Nucleic AcidsJournal of

Volume 2014

Stem CellsInternational



Enzyme Research



Microbiology


over the last few years Notably insights from proposedtargetmolecules have included different portions of the deathpathway depending on the type of cancer Applications ofmany of such targeted therapy in different cell types andsignals studied in them have emphasized selected controlpoints for each targeted therapy

2 Apoptosis Defect and Cancer

Defects in programmed cell death (apoptosis) mechanismsplay important roles in tumor pathogenesis allowing neo-plastic cells to survive over intended lifespans subverting theneed for exogenous survival factors and providing protectionfromoxidative stress and hypoxia as the tumormass expandsThat gives time for accumulation of genetic alterations thatderegulate cell proliferation interfere with differentiationpromote angiogenesis and increase invasiveness duringtumor progression [9] Apoptosis defects are now consideredan important complement of protooncogene activation asmany deregulated oncoproteins that drive cell division alsotrigger apoptosis (eg Myc E1a and Cyclin-D1) [10] Onthe other hand the noncancerous cells have a DNA repairmachinery Defects in DNA repair andor chromosome seg-regation normally trigger cell suicide as a defensemechanismfor eradicating genetically unstable cells and thus such suicidemechanismrsquos defects permit survival of genetically unstablecells providing opportunities for selection of progressivelyaggressive clones and may promote tumorigenesis [11]

There are varieties of molecular mechanisms that tumorcells use to suppress apoptosis Tumor cells can acquireresistance to apoptosis by the expression of antiapoptoticproteins such as Bcl-2 or by the downregulation or mutationof proapoptotic proteins such as BAX Since the expressionof both Bcl-2 and BAX is regulated by the p53 tumorsuppressor gene [12] some forms of human B-cell lymphomahave Bcl-2 overexpression That example represents the firstand strongest lines of evidence that failure of cell deathcontributes to cancer [13]

Apoptosis defects may allow epithelial cells to survivein a suspended state without attachment to extracellularmatrix which facilitate metastasis [14] They also promoteresistance to the immune system including many weaponsof cytolytic T cells (CTLs) and natural killer (NK) cells usedfor attacking tumors that depend on integrity of the apoptosismachinery [15] Cancer-associated defects in apoptosis playa role in treatment resistance with conventional therapieslike chemotherapy and radiotherapy increasing the thresholdfor cell death and thereby requiring higher doses for tumorkilling agents [16] Thus dysregulated or defective apoptosisregulation is a fundamental aspect of the tumor biologySuccessful eradication of cancer cells by nonsurgical means isultimately approached via induction of apoptosis Thereforeall the cancer drug designers try either to activate theinactivated apoptotic mechanism or rectify a defective oneHence all cytotoxic anticancer therapies currently in clinicaluse when they work induce apoptosis of malignant cellsHence deeper understanding of the molecular mechanismsof apoptosis and its defective status opens the gate for a newclass of targeted therapeutics

21 Induction of Apoptosis Apoptosis is caused by pro-teases known as ldquocaspasesrdquo which specifically target cysteineaspartyl [17 18] Upon receiving specific signals instructingthe cells to undergo apoptosis a number of distinctive changesoccur in the cell A family of proteins known as caspasesis typically activated in the early stages of apoptosis Theseproteins cleave key cellular components that are requiredfor normal cellular function including structural proteins inthe cytoskeleton and nuclear proteins such as DNA repairenzymes The caspases can also activate other degradativeenzymes such as DNases which begin to cleave the DNA inthe nucleus

During the apoptotic process apoptotic cells displaydistinctive morphology Typically the cell begins to shrinkfollowing the cleavage of lamins and actin filaments in thecytoskeleton The apoptotic breakdown of chromatin in thenucleus often leads to nuclear condensation andor a ldquohorse-shoerdquo like appearance Cells continue to shrink packagingthemselves into a form that allows for their removal bymacrophages These phagocytic cells are responsible forclearing the apoptotic cells from tissues in a clean and tidyfashion that avoids many of the problems associated withnecrotic cell death In order to promote their phagocytosisby macrophages apoptotic cells often undergo plasma mem-brane changes that trigger the macrophage response One ofsuch changes is the translocation of phosphatidylserine fromthe inside of the cell to the outer surface The end stagesof apoptosis are often characterised by the appearance ofmembrane blebs or blisters process and small vesicles calledapoptotic bodies

The real workers in apoptosis mechanism are caspasesCaspases family is composed of intracellular cysteine pro-teases (119899 = 11 in humans) which collaborate in proteolyticcascades These caspases activate themselves and each otherWithin these proteolytic cascades caspases can be posi-tioned as either upstream ldquoinitiatorsrdquo or downstream ldquoeffec-torsrdquo of apoptosis Several pathways for activating caspasesexist

First there are thirty members of the tumor necrosisfactor- (TNF-) family receptors eight contain a so-calleddeath domain (DD) in their cytosolic tail [19] Severalof these DD-containing TNF-family receptors use caspaseactivation as a signaling mechanism including TNFR1CD120a FasAPO1CD95 DR3Apo2Weasle DR4TrailR1DR5TrailR2 and DR6 Ligation of these receptors at thecell surface results in the recruitment of several intracellu-lar proteins including certain procaspases to the cytoso-lic domains of these receptors forming a ldquodeath-inducingsignaling complexrdquo (DISC) that triggers caspase activationconstituting the so-called ldquoextrinsicrdquo pathway for apoptosis[20] The caspase-8 and in some cases caspase-10 are thespecific caspases summoned to the DISC These caspasescontain so-called death effector domains (DEDs) in their N-terminal prodomains that bind to a corresponding DED inthe adaptor protein FADD thus linking them to the TNF-family death receptor complexes

Second is the intrinsic pathway in which mitochondriainduces apoptosis by releasing cytochrome-c (cyt-c) into thecytosol The released cytochrome c assembles a multiprotein


































































































References



















































































































































































































































































































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology


































































































References



















































































































































































































































































































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology


























































































References



















































































































































































































































































































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology
















































































References



















































































































































































































































































































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology







































































References



















































































































































































































































































































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology





























































References



















































































































































































































































































































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology



















































References



















































































































































































































































































































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology












































References



















































































































































































































































































































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology



































References



















































































































































































































































































































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology



























References



















































































































































































































































































































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology



















References



















































































































































































































































































































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology











References



















































































































































































































































































































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology














































































































































































































































































































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology








































































































































































































































































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology








































































































































































































































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology




































































































































































































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology


































































































































































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology


































































































































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology



































































































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology
































































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology

























































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology



























Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology








Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology

Documents

Review Article Apoptosis and Molecular Targeting Therapy in …downloads.hindawi.com/journals/bmri/2014/150845.pdf · 2019-07-31 · Review Article Apoptosis and Molecular Targeting