Dr Dean WillisDepartment of PharmacologyUniversity College LondonGower Street, London WC1 6BTdean.willis@ucl.ac.uk

Pharmacology of Chemotherapy

Cancer Biology

Learning Objectives

To know the basic phenotypic and biochemical differences between normal and cancer cells

To understand the basic principal of cancer chemotherapy and its limitations

To know the four main groups of anti-cancer cytotoxic drugs

To know the basic mechanisms that develop in tumour cells that leads to drug resistance

To understand the adverse effects of cancer chemotherapy

To understand the scientific rational behind drug combination studies.

Understand the pharmacological rational behind the new anti cancer chemotherapeutics

Revise mammalian DNA replication and the biosynthesis of nucleotides.

Read Pharmacology, Rang, Dale & Ritter. Anti-cancer Drugs

Chemotherapy of Neoplastic Diseases. Section IX. Goodman & Gilman’s. The Pharmacological Basis of Therapeutics. 10th Edition.

Learning Tasks & Further Reading

MICROTUBULES AS A TARGET FOR ANTICANCER DRUGS

CLINICAL TRANSLATION OF ANGIOGENESIS INHIBITORS

NF-κB IN CANCER: FROM INNOCENT BYSTANDER TO MAJOR CULPRIT

Nature Reviews in Cancer

Recent reviews relating to chemotherapy

Theory of Chemotherapy. The Man, the film?

Drug

Host Parasite

No effect Cytotoxic

For the case of Chemotherapy bacteria, fungi, protozoa, helminths, viruses and cancer cell are considered parasites.

Theory

Find Qualitative (preferable) or Quantitative Biochemical difference between Host and Parasite which when exploited by a selective drug results in a cytotoxic effect to the parasite but not host

Paul Ehrlich 1854-1915Nobel Laureate 1908

CHEMOTHERAPY: The basis of anti-cancer chemotherapy and the problem

Qualitative

Quantitative

The goal is to selectively kill malignant cells and spare normal host cells. Selective toxicity is not possible to the degree seen with antibacterial or even anti-viral chemotherapy, as malignant cells are derived from the host and the differences between normal and malignant cells are much more subtle. Therefore, successful treatment is dependent on killing malignant tumor cells with doses and strategies that allow recovery of normal proliferating cells.

Characteristics of tumour cells &sites of therapeutic intervention (present and future)

Bloodvessel

PrimaryTumour

Normalorgan/tissue

Major Modalities for Treatment for cancer

Surgery

Irradiation

Chemotherapy

Combination of the above (modality therapy)

Proliferation Apoptosis

Differentiation

Host systemsIm m unolog ica l/In flam m ation /A ng iogenes is

Invasiveness

MetastasisClassical Anti-cancer drugs

New drugs e.g. im atinib

Retinoids

M etaloprotease inhibitors

M etaloprotease inhibitors

Adhesion m olecules inhibitors

Adhesion m olecules inhibitors

Biological Response M odifiers Angiogenesis inhibitors

Extracellu larM atrix

H yperp las tic

A nap las tic

Problems associated with Anti-cancer chemotherapy

Because cells are derived from self, most therapies rely on quantitative (usually proliferation/growth) rather than qualitative. Therefor host cells are invariably effected.

Therapeutic Index= LD50/ED50

For anti-cancer drugs this tends to be low therefore Tox problems

• Bone Marrow (G-CSF shorten period of Leukopenia)• Healing• Alopecia• Damage to gastrointestinal epithelium (nutritional state)• Depression of growth (children)• Sterility• Teratogenicity• Severe nausea (treat with 5-HT3-receptor antagonist)

Problems associated with Anti-cancer chemotherapy

Growth fraction (percentage of cells actively dividing)

S

M

G 1

G 2

G 0

A

B

Cnone cycling

cells

Anti-cancer chemotherapy most effect against cells in cell fraction A. Cells in fraction B can re-enter fraction A.

Cell number(tumor size)

Time

1012

109

Problems associated with Anti-cancer chemotherapy

Cell No

Tum

ou

rS

ize

(cm

)

Pe rce n

ta ge o

fc

ell in c ycle (A

)

101210910 3 106

2

10

20

Limit of diagnostic procedures.

Exponential growth of a tumour

Problems associated with Anti-cancer chemotherapy

Cell cycle: Susceptibility of cancer cells to a given drug is often dependant on cell cycle

S

M

G 1

G 2

G 0

D ifferention

A poptos is

A

B

E

D

P ositive factorsG rowth factorsC yclins/cdks

R b gene productp53 gene product

P lant a lkaloidsVinca a lkaloids, taxanes

B leom ycinA lky la ting agents,antim etabolites,m any cytotox ic antib iotics

Log [con]

IrradiationBleomycins

Antimetabolites

Cel

l nu

mb

er

Problems associated with Anti-cancer chemotherapy

Minimal immune response

• Because the tumour is self the immune response as difficulty recognizing the tumour • The drug receives no help (or little help) from the immune system• Many anti-cancer drugs are toxic to immune cells (Bone marrow)• Cancer cells can hide

Tumour cell heterogeneity & cell phenotype instability

Drug Resistance

•Specfic drug•Drug of same chemical class•Multi-drug resistance:- P170 (mdr1 gene)

Summary anti-cancer chemotherapy's

Cytotoxic drugs•Alkylating agentsCyclophosphamide, Busulfan, Carmustin, Chloramabucil, Ifosfamide, lomustine, Melphan, TreosulfanCisplatin, Carboplatin, Oxaliplatin

•Anti-metabolitesMethotrexate, Fluoruracil, Cytarabine, Cladribine, Fludarabine phosphate, Gemcitabine, Mercaptopurine

•Cytotoxic AntibioticsBleomycin, Dactinomycin, Daunorubicin, Doxorubicin, Epirubicin, Idarubicin, Mitomycin

•Plant derivativesEtoposide, Vinblastine, Vincristine

HormoneTamoxifen, Anastrozole, Letrozole

MiscellaneousImatinib, Bortezomib, Bevacizumab, Trastuzumab, Taxol, Cristaspase, Arsenic

Summary of cytotoxic drug action

PU R IN E SYN THES IS PYR IM ID IN E SYN THE SIS

R IB O NU C LEO TIDE S

PR O TEINS

M IR O TU BU LES EN ZYM ES

D N A

R NA( )transfer, m essenger, ribosom al

D EO XY RIBO N U CLEO TID ES

PENTO STATIN (ct2)

6-M ER CAPTO PUR INE(ct2)6-TH IOG U ANIN E (ct2)

M ETH O TREXATE (ct2 )

C YTARABIN E (ct2)

5-FLU O R OU R ACIL (ct2 )

BLEOM YC IN S (ct3)

D OXO R UBIC IN (ct3)ETO PO SID E (ct4)

D ACTIN OM YCIN (ct3)

V IN C A ALKALO ID S (ct4)TAXANES (ct4)

ALKYLATIN G AG EN TS (ct1)M ITO M YC IN (ct3)C ISPLATIN (ct1)

Inh ib its adenosinedeam inase

Inh ib it pu rine syn thesisInh ib it nucleo tidein te rconversion

Inh ib its pu rine synthesisInh ib its D TM P

Inh ib its D N A po lym eraseInh ib its R N A function

Inh ib its D TM P syn thes is

D am ages D N Aand p revent repa ir

C ross-link D N A

Inh ib its topoisom erase II

Inh ib its topoisom erase II

Inh ib its R N A synthesis

Inh ib its R N A synthesis

In terca la tes in D N A

Inh ib it func tion o f m icro tubes

N

NN

N

N

N

NN

N

N

N

NN

N

N

N N

N

N

NH

NHNH

NH

NH

NH 2

NH 2

NH 2

NH 2

NH2

O

OO

O

O

O

OO

O

O

O

OO

O

O

P

PP

P

P

+

CH CH Cl2 2 CH CH Cl2 2

CH CH Cl2 2

CH CH Cl2 2

H C3 H C3

H C3

H C3

CH 2

CH 2

C H 2

C H 2

CH 2

CH 2

C H 2

C H 2

+

+N-7

Deoxyguanosine

Deoxyguanosine

N1 & N3 adenineN3 cytosine

Action of Alkylating drugs (methlorethamine) Mustine

A

A

T

T

C

C

G

G

C

C

G

G

Intra-strand linkage

Cross-linking

Other nitrogen mustardsCycloposphamideChlorambucilMelphalan

Action of Alkylating drugs

CH2

CH2

CH2 CH2

CH2 CH2CH2

CHO

NH

PO

O

Cl

Cl

NH C2

HC

4-Hydroxycyclophosphamide Aldophosphamide

Phosphamide MustardAcrolein

Cyclophosphamide

CH2 CH2

CH2 CH2

NH2

PO

OH

Cl

Cl

N

Nitrosoureas carmustine, lomustineBusulphan

Cisplatin

ResistanceDecreased permeabilityIncreased production of glutathioneIncrease DNA repairIncreased metabolism of drugs

NH2

NH2

Pt2+

Cl_

Cl_

Administered orally or i.v.tumours of testes & ovary

Anti-metabolites (methotrexate)

FF (glu)n

(glu)n

(glu)n

(G lu) (glu)n(glu)nF H 2 F H 4

F H 4

DTMP DUMPThym idyla tesynthase

D ihydro fo la tereduc tase

D ihydro fo la tereduc taseMethotrexate

Methotrexate

O ne-ca rbon U n it

C ellB lood

Polyglutam ates are retained in the cell

DTMP=Deoxythymidylic Acid

DUM P=Deoxyuridylic Acid

Cancer cells have higher rates of g lutamation enzym es levels

ResistanceDecreased transport into cellsDecreased affinity of DHF reductaseIncrease levels of DHF reductase

Administered orally or i.v.Non-Hodgkin’s lymphomaBurkitt’s lymphomaChildhood acute lymphoblastic leukemia

N

N N

N

HO

HO HO

HO

O

O O

O

O

O O

O

O

O O

O

F

F

HN

HN HNCH 3

HN

Inhib ites Thymidilate synthasevia com plexing w ith Tetrahydrofolate

Thym idilate synthaseTetrahydrofolate

P

P P

P

5-F luorouracilF luorouracil-Deoxy Urid ine

+

Thym idinePhosphorylase

D eoxyuridy lic acid D eoxythym idylic acid

Anti-metabolites (5-Fluorouracil)

ResistanceDecreased levels of thymidine phosphorylaseor affinity for 5FU

Administered parentallyBreast, ovarian, prostate,pancreatic, hepatic carcinomas

Anti-metabolites (Cytosine arabinoside, Cytarabine)

P PP P PPN N N N

H O H O H O H OH O H O H O H O

H O

O O O O

O O O OO O O O

H N H N H N H N

Cytosine arabinoside

DeoxycytidineKinase

DCM PKinase

NucleosideDiphosphate

Kinase

AraCM P AraCTPAraCDP

P revents D N A cha in e longation

ResistanceDecreased levels of deoxycytidine kinaseIncrease in dCTP

Administered oral and i.v.Chronic granulocytic leukemia

Cytotoxic antibiotics Doxorubicin, Dactinomycin, Etoposide (VA)

ResistanceMultidrug resistanceIncreased glutathione peroxidasedecreased topoisomerase

D ouble stranded D N A

D ouble stranded D N A break

N on-c leavab le com p lexTrans ien t c leavab lecom plex P ersis tan t c leavab le

com plex

Topo isom erase II

DR

UG

S trand passing, ro ta tionb reak resea ling

Administered i.v.Acute lymphocytic leukemiaAcute granulocytic leukemia

Cytotoxic antibiotics (Dactinomycin, Bleomycin)

A

A

T

T

C

C

G

G

C

C

G

G

Minor groove

Major groove

Dactinomycin

Bleomycin

Resistance not characterizedParentally administeredUsed in combination with other modalities

Resistance due to increase anti-oxidant,and DNA repair mechanismsParentally administeredTreatment of testicular and ovarian cancer

Note cytotoxic antibiotics do share some modes of action DNA binding and topoisomerase II inhibition

Plant alkaloids (vincristine & vinblastine, Taxol)

Steady state

Polym erization blocked by vincristine & vinblastine

Polym erization stabilized by Taxol

Tub lindim er

Assem bly

C ontinued d isassem bly

S table m icro tubu le

D rug

D isassem bly

Resistance due to multidrug resistance,altered tublin moleculesAdministered I.v.Childhood leukemia's, Hodgkin'sand non-Hodgkin's lymphoma, testicular,ovarian carcinomas and brain tumours

Vincristine & vinblastine

Resistancealtered tublin molecules

Administered i.v.Metastatic ovarian and breast cancer

Taxol

BindingProtein

TargetProtein

Decreaseuptake

Increaseefflux

DHRF

Nuleus

Topoisomerase II

GSH

SP

Intracellularbinding

Altered targetamount or affinity

Altered targetamount or affinity

Increases metabolism

IncreaseRepair

P-glycoprotein

Resistance to chemotherapeutic agents

New anti-cancer drugs: Imatinib

Treatment Chronic myelogenous leukaemia

CML caused by reciprocal translocation between chromosomes 9 and 22 Philadelphia chromosome BCR-ABL gene which encodes a protein with high tyrosine kinase activityFast drug to be approved by FDA, Approx 80% remission in IFN refractory patientsActivity against c-kit & PDGF receptor

New anti-cancer drugs: Bortezomib

Treat multiple myeloma ( current drugs 5 year survival is approx 29%)

In MM (and other tumors ) NF-B is constitutively expressed

I- B

I- B

I- B

I- B

I- B

NF- B

P50

P50

P50 P50

P50

P65

P65

P65 P65

P65

IKK IKK

IKK

Inflammatory genesanti-apoptotic genes

Proteasome

Bortezomib

Combination therapy

Knowledge of the pharmacokinetics of each cytotoxic agent is less important than knowing the maximal dose and the duration of that drug can be administrated before adverse side effects become unacceptable

Individual drugs must be active against the tumour

Drugs must have different modes of action• Minimize drug resistance• Hit cancer cells in different parts of cell cycle

Drugs must have limited overlapping toxicity

Individuals should be optimally scheduled

EtoposideBleomycin

CisplatinCurative therapy testicular cancer (BEP)

Renal & hepatic FunctionBone Marrow reserveImmune statusPrevious Treatments

Likely natural History of TumorPatients Wishes to undergo treatmentPatients Physical & emotional ToleranceLong term gains & Risks