Clinica Chimica Acta 417 (2013) 39–44

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Clinica Chimica Acta

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Invited critical review

ACTB in cancer

Chunmei Guo a, Shuqing Liu b, Jiasheng Wang a, Ming-Zhong Sun a,⁎, Frederick T. Greenaway c

a Department of Biotechnology, Dalian Medical University, Dalian 116044, Chinab Department of Biochemistry, Dalian Medical University, Dalian 116044, Chinac Carlson School of Chemistry and Biochemistry, Clark University, Worcester, MA 01610, USA

⁎ Corresponding author at: Department of BiotechnolDalian 116044, China. Tel.: +86 411 8611 0445.

E-mail address: mxs288@gmail.com (M.-Z. Sun).

0009-8981/$ – see front matter © 2013 Elsevier B.V. Allhttp://dx.doi.org/10.1016/j.cca.2012.12.012

a b s t r a c t

a r t i c l e i n f o

Article history:Received 25 September 2012Received in revised form 27 November 2012Accepted 1 December 2012Available online 22 December 2012

Keywords:ACTBFunctionTumorCancer

Beta-actin (ACTB) has traditionally been regarded as an endogenous housekeeping gene and has been widelyused as a reference gene/protein in quantifying expression levels in tumors. However, ACTB is closely associ-ated with a variety of cancers and accumulating evidence indicates that ACTB is de-regulated in liver, mela-noma, renal, colorectal, gastric, pancreatic, esophageal, lung, breast, prostate, ovarian cancers, leukemia andlymphoma. ACTB is generally found to be up-regulated in the majority of tumor cells and tissues. The abnor-mal expression and polymerization of ACTB and the resulting changes to the cytoskeleton are revealed to beassociated with the invasiveness and metastasis of cancers. The current review explores relevant mecha-nisms, integrates current understandings, and provides suggestions for future studies of the roles of ACTBin tumors.

© 2013 Elsevier B.V. All rights reserved.

Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 392. The association of ACTB with tumors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

2.1. ACTB is potentially involved in liver cancer development and metastasis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 402.2. ACTB is potentially correlated with melanoma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 402.3. ACTB is potentially involved in renal cancer development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 402.4. ACTB is de-regulated in tissues from colorectal cancer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 402.5. ACTB mRNA over-expression is associated with gastric cancer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 412.6. ACTB is not suitable as a reference gene for pancreatic cancer and esophageal cancer . . . . . . . . . . . . . . . . . . . . . . . . . 412.7. ACTB is closely associated with lung cancer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 412.8. ACTB might promote breast cancer cell proliferation and tumor aggressiveness . . . . . . . . . . . . . . . . . . . . . . . . . . . . 412.9. ACTB is associated with prostate cancer and ovarian cancer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 412.10. ACTB is a potential indictor and therapeutic target for leukemia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 412.11. ACTB is associated with drug-resistance of lymphoma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

3. Potential mechanisms of action of ACTB in cancer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 424. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

1. Introduction

Beta-actin (ACTB) is an abundant and highly conserved cytoskeletonstructural protein that is widely distributed in all eukaryotic cells andplays critical roles in cellmigration, cell division, embryonic development,wound healing, immune response and gene expression [1–4]. These

ogy, Dalian Medical University,

rights reserved.

functions are attributed to the ability of ACTB to form filaments that canbe rapidly assembled and disassembled in response to the needs of cells[2,3,5]. Cell migration is commonly driven by ACTB polymerization atthe leading edge, which provides the protrusive forces that push themembrane forward [6–8]. ACTB is generally regarded as a constitutivehousekeeping gene with the assumption that ACTB expression is usuallyunaffected by most experimental or physiological conditions and it hastherefore been widely used as a reference for quantification of changesof genes/proteins in cells and tissues [6–8]. However, since it is amultifunctional gene/protein, the utilization of ACTB as a reference

40 C. Guo et al. / Clinica Chimica Acta 417 (2013) 39–44

gene/protein has been challenged [9,10]. ACTB levels are highly differ-entially regulated in a variety of types of cells/tissues under certainmet-abolic conditions. Distinct correlations between ACTB levels, ACTBpolymerization, ACTB cytoskeleton organization and invasiveness andmetastatic capacity of tumor cells [2–4,8,11], suggest that ACTB playsroles in cancer pathogenesis that are not yet understood. ACTB wasfound to be differentially expressed in liver, melanoma, renal, colorec-tal, gastric, pancreatic, esophageal, lung, breast, prostate, ovarian can-cers, leukemia and lymphoma under certain conditions [12–15],which suggests that 1) ACTB might be unsuitable for gene/proteinlevel normalization in certain types of tumor cells and clinical samples;2) the utilization of ACTBmRNA as a control RNA should be chosen cau-tiously; and 3) ACTB may play a role in cancer pathogenesis.

The current paper summarizes recent research progress in under-standing the roles of ACTB in tumors and discusses relevant mecha-nisms. ACTB de-regulation is usually detected in tumors and affectsthe polymerization of ACTB at the leading edge in tumor cells, accel-erating tumor formation, invasion and metastasis. However, the de-tailed mechanisms of action of ACTB in tumor progression are stillunclear and worthy of study. ACTB de-regulation in certain tumorshighlights the significant role of this housekeeping gene in cell func-tion and provides useful insights for future study of it.

2. The association of ACTB with tumors

2.1. ACTB is potentially involved in liver cancer development and metastasis

Hepatocellular carcinoma (HCC) ranks third amongst all deathsfrom cancers, killing ~650,000 people annually [16,17]. The majorrisk factor for HCC development is liver cirrhosis following chronichepatitis viral infections from hepatitis B virus (HBV) and hepatitisC virus (HCV) [1,18].

ACTB is up-regulated in liver cancer tissues. Gene microarray andquantitative real-time RT-PCR (qRT-PCR) analyses showed thatACTB is up-regulated two- to three-fold in highly advanced stagesof HCV-induced HCC [1]. Comparison of ACTB gene levels in normalliver tissues, and in paired tumor and non-tumor tissues of patientswith HBV-related HCC indicted that ACTB is differentially expressedin these tissues, which can lead to misinterpretation of gene expres-sion results [18]. ACTB is thus unsuitable for qRT-PCR normalizationin such tissues.

The genes favoring progression ofmetastasismost probably originatein primary tumors. It is becoming a routine strategy to search for bio-markers that can be used for clinical prognosis by comparing gene ex-pression levels in tumor samples or in cells with and without invasion/metastasis. Several studies have shown a correlation of ACTBwith cancercell motility andmetastasis potential. ACTBwas de-regulated in differentTNM stages and degrees of tumor invasiveness of HCC [18,19] and wasdifferentially expressed in paired malignant and non-malignant tissuesfrom untreated patients with HCC. ACTB levels did not correlate with pa-tient age or gender, orwith tumor size, number, or stage, orwith cirrhoticstatus, but did significantly correlate with venous invasion, which is ahistopathological feature of HCC invasiveness. ACTB was significantlyup-regulated in HCC with more highly invasive tumors, consistentwith ACTB de-regulation inHCC carcinogenesis and progression [19]. Re-sults from separate groups indicated that ACTB mRNA levels wereup-regulated 2.8-fold and 4.8-fold in liver carcinoma metastatic tissuescompared with normal liver tissues [20,21]. ACTB up-regulation wasalso found in N1S1 rat hepatoma samples [22]. These results suggestthat ACTB is not a suitable internal control for comparative gene expres-sion studies in HCC, cirrhosis and normal tissues. In hepatoma Morris5123 cells, which have increased cell locomotion andhigher invasivenesscompared to parental cells, ACTB was remarkably increased and therewas an increased level of ACTB polymerization [4,8].

These results suggest that ACTB might be essential for hepatomaoncogenesis. ACTB gene levels might serve as a diagnostic indicator

for HCC as ACTB up-regulation is closely associated with liver cancergrowth and metastasis although the exact relationship between thisnovel activity of ACTB and tumor metastasis remains to be elucidated.It is also possible that changes in ACTB expression and cytoskeletonreorganization might be involved in tumor malignancy, in whichcase it could be possible to find anti-tumor drugs affecting cellmotility.

2.2. ACTB is potentially correlated with melanoma

One of the most malignant tumors, melanoma, is steadily increas-ing and has a high mortality rate. Once it metastasizes, the 5-year sur-vival rate of melanoma is below 10% [12].

ACTB has been associated with the invasiveness of melanoma cells.cDNA array analyses of different genes expressed in two melanomacells, 1C8 (a non-invasive melanoma cell) and T1C3 (an invasive mela-noma cell), derived from the samemelanoma patient indicated that themRNA level of ACTB in T1C3was twofold higher than in 1C8melanomacells [13]. ACTB is not appropriately utilized as a reference gene/proteinfor melanoma as it was significantly de-regulated in tumor cellsobtained from the samepatient or in highly heterogeneous cellular sub-populations of same pathological origin. This points out that the selec-tion of an appropriate internal control for gene or protein expressionanalyses must take into account the type of human cancer beingstudied.

2.3. ACTB is potentially involved in renal cancer development

Renal cell carcinoma (RCC) is a highly metastatic urological tumoraccounting for ~3% of adult cancers. RCC is clinically asymptomaticand usually detected in the course of routine ultrasonic scans [14,15].The lack of diagnostic and prognostic markers complicates its early de-tection, so that most cancers havemetastasized at the time of diagnosis.

The clear cell subtype of RCC (ccRCC) has ~75% incidence of malig-nant RCC with poor prognosis [15]. RT-PCR results indicate that ACTBwas significantly increased in tissues from 25 ccRCC patients comparedto matched non-malignant tissues, but that the ACTB level did not de-pend on patients' age or gender, or the tumor stage [23]. ACTB proteinwas also de-regulated in RCC cell lines and tumor tissues, and ACTB pro-tein levels varied among established RCC lines, with higher levels beingseen in malignant renal tissues in comparison with normal tissues [24].Thus ACTB might be involved in RCC and the corresponding regulationmechanisms need to be clarified.

2.4. ACTB is de-regulated in tissues from colorectal cancer

Colorectal cancer (CRC) is the third most common cancer. It affectsalmost a million people annually, and causes approximately 500,000deaths. Despite its high incidence, CRC has a better prognosis with a50% mortality rate [16,25,26].

Utilizing a model-based variance estimation strategy to select ref-erence genes for qRT-PCR data, Andersen et al. found that ACTB wasunsuitable for normalization of colon and bladder cancers [27]. A sim-ilar conclusion was reached for ACTB expression in colorectal tumorsmatched against normal specimens [28,29], and ACTB was also foundto be significantly de-regulated in CRC tissues [9,29]. Microarray dataand Western blot analysis revealed that ACTB protein levels de-creased four-fold in MDA7-transduced CRC DLD-1 cells comparedwith untransduced DLD-1 cells [20]. MDA7 is a tumor suppressorthat can induce apoptosis and dismantle the cytoskeletal make-upof cancer cells. This finding indicates that ACTB may be involved inCRC carcinogenesis [30]. The general conclusion of such findings isthat one should be cautious in using ACTB as an internal referencegene/protein for CRC studies.

41C. Guo et al. / Clinica Chimica Acta 417 (2013) 39–44

2.5. ACTB mRNA over-expression is associated with gastric cancer

Gastric cancer is the fourthmost commoncancer. Survival fromgastriccancer is poor as patients are often diagnosed at highly advanced stages[31]. ACTBwas proved to be involved in themalignancy of gastric cancer.

ACTBwas proved to be an unsuitable endogenous reference gene forgene expression studies of gastric cancer based on the fact that ACTBmRNA levels showed a 1.4-fold expression increase in gastric carcinomatissues compared to matched paracancerous normal tissues [21].Assessing the suitability of six possible reference genes by qRT-PCR in20 paired gastric cancer tissues and matched paracancerous tissuesand six gastric cancer cell lines, Rho et al. revealed that ACTB had a rel-atively lower stability unsuitably used as single reference gene. ACTBwas more highly expressed in gastric tissues than in cancer cell lines(SNU-216, SNU-638, SNU-719, AGS, MKN-28 and KATOIII) [31]. HigherACTB levels were also found in gastric cancer tissues than in AGS/SNU-638 gastric cancer cells [9], opposite to the expectation that cancercells are usually more activated in metabolism and eventually displayhigher transcription activities [31].

2.6. ACTB is not suitable as a reference gene for pancreatic cancer andesophageal cancer

The use of ACTB as an endogenous reference for gene expressionstudies of pancreatic cancer and esophageal cancer has also beenquestioned [21]. ACTB is up-regulated in pancreatic carcinomas atboth RNA and protein levels. mRNA levels of ACTB exhibited a1.7-fold increase in pancreatic carcinoma tissues over normal pancre-atic tissues [21], which indicates a role for ACTB in pancreatic cancer.

Esophageal squamous cell carcinoma (ESCC) and esophageal ade-nocarcinoma are the major histological types of esophageal cancersfound in China and in Western countries [32]. Two-dimensionalelectrophoresis-MALDI-TOF-MS assays indicated that ACTB wasup-regulated 4.4-fold in fifteen paired samples of ESCC and adjacentnormal esophageal tissues [32]. However, ACTB was down-regulatedat the RNA level in esophageal carcinoma; mRNA levels of ACTB weredecreased 0.8-fold in esophageal carcinoma tissues in comparisonwith normal esophageal tissues [21]. Thus ACTB is associated with theformation and malignancy of esophageal carcinomas, although the de-tailed action mechanism needs to be clarified.

2.7. ACTB is closely associated with lung cancer

As the leading cause of cancer-related deaths, lung cancer has anoverall five year survival rate of ~15% [16,33]. Lung cancer is usuallydiagnosed in highly advanced stages, and frequently too late for sur-gical intervention.

ACTB was proved to be unsuitable for gene expression normaliza-tion for non-small cell lung cancer (NSCLC) specimens and NSCLC celllines. ACTB mRNA levels were significantly increased in NSCLC celllines/tissues in comparison to normal ones [33,34]. Moreover, immuno-histochemistry (HIC) and proteomics results have also indicated thatACTB protein levels are also significantly up-regulated in NSCLC sam-ples compared to normal ones [35]. Serial analysis of gene expression(SAGE) profiles of fifteen malignant lung tumors and matchednon-malignant parenchyma samples also indicated that ACTB levelsare quite different between lung cancer and non-lung cancer tissues[36]. Thus ACTB de-regulation might be associated with the formationandmalignancy of lung cancer and the up-regulation of ACTB is possiblya sign of lung cancer cellular tumourigenesis.

2.8. ACTB might promote breast cancer cell proliferation and tumoraggressiveness

Breast cancer (BC) ranks first in incidence among women, it affectsmore than one million women, accounting for more than 400,000

deaths annually [16]. ACTB was found to be differentially expressed inBC and was associated with BC drug resistance.

First, ACTB was differentially expressed in BC and thus unsuitablyutilized as a reference gene/protein. qRT-PCR analyses of ACTB levelsin estrogen receptor positive (ER+) invasive BC (IBC), ER-IBC, normalbreast tissue and ER+BC cell lines indicated that ACTB is unsuitablefor qRT-PCR data normalization of normal and malignant humanbreast samples [37]. ACTB and transferrin receptor (TFRC) wasfound to be the best combination for quantification of urokinase plas-minogen activator in BC by qRT-PCR. The ACTB gene alone, however,is not suitable for quantifying gene expression in BC [38]. These resultswere also confirmed by the higher variability of ACTB across BC, whichmade it unsuitable as a single housekeeper control [39]. Second, ACTBdifferential expression was associated with metastasis of BC. qRT-PCRanalysis of ACTB expression in the four human BC lines MCF-10A,MCF-10T (MCF-10A transformed with H-ras), MCF-7 (tumorigenic butnonmetastatic) andMDA-mb-231 (metastatic) indicated that the highestexpression level of ACTBwasdetected inMDA-mb-231 [40],which impli-cated ACTB involvement in BCmetastasis. In addition, the averaged tran-script level of ACTB was significantly decreased in leucocytes from BCpatients compared with K562 cells and normal leucocytes [41]. Third,ACTB was associated with drug-resistance of BC. ACTB protein levelswere down-regulated fourfold in MDA7-transduced BC T47D cell linesin comparisonwith untransduced-T47D cells [30]. The gene level expres-sion of ACTB was also significantly decreased inMCF-7 BC cells followingtreatmentwith salicylic acid (SA) or heat shock (HS) due to drug-inducedcell apoptosis [42]. Since ACTB might play an important role indrug-related apoptosis of BC cells, the detailed mechanism of action isworthy of clarification.

2.9. ACTB is associated with prostate cancer and ovarian cancer

Prostate cancer is a leading cause of cancer death in men. Theearly detection and timely treatment of organ-confined disease iskey to reducing prostate cancer mortality [43]. qRT-PCR analysis indi-cated that ACTB was more highly expressed in human formalin-fixedparaffin-embedded (FFPE) prostate cancer tissues than in matchedperitumoral normal tissues obtained by laser microdissection [43,44].Since ACTBwas de-regulated in prostate cancer, it is unsuitable for nor-malization purposes in gene profiling studies between normal and ma-lignant prostate tissues [44].

Ovarian cancer is the leading course of death from gynecologicalmalignancy. Serous ovarian cancer accounts for approximately 60–80% of ovarian cancers and has spread to extra-ovarian sites at thetime of diagnosis for the majority of patients. The 5-year survival rateof women diagnosed with ovarian cancer at early stages of the diseaseis ~95%, but drops to less than 30% when patients are diagnosed atlate stages of the disease. Ovarian cancer survival rates have not im-proved in the past few decades [45]. Recently, new potential predictiveand prognosticmolecularmarkers for ovarian cancerwere targeted by acomparative genetic study. Interestingly, ACTB levels were found to besignificantly increased in specimens from serous ovarian cancers com-pared with normal ovarian epithelial tissues. ACTB is not suitable foruse as a reference for gene expression normalization in serous ovariancancer, but it might be involved in ovarian cancer and there is a needfor further investigation of the expression levels and roles of ACTB inother sub-types of ovarian cancer [45].

2.10. ACTB is a potential indictor and therapeutic target for leukemia

B-cell chronic lymphocytic leukemia (B-CLL) has a highly hetero-geneous clinical course and is the most common form of adult leuke-mia. There is a pressing need for better prediction of individualclinical progression to enable the selection of optimal therapies andprognostic factors for B-CLL. ACTB was found to be an unsuitable ref-erence for quantitative polymerase chain reaction (qPCR) genetic

42 C. Guo et al. / Clinica Chimica Acta 417 (2013) 39–44

expression comparison in CD19+ B cells from B-CLL patients’ periph-eral blood [46]. Using the qPCR technique, Gao et al. found that theDNA concentration and integrity of ACTB were higher in the plasmaof acute leukemia patients compare to healthy persons, which sug-gests that this increase might be a potential indicator for acute leuke-mia [47]. In addition, ACTB was up-regulated more than twofold inretinoid acid (RA) resistant human acute promyelocytic leukemia(APL) cell line NB4-R1 following As4S4 treatment for 24 h, indicatingACTB protein might have potential as a therapeutic target for drug re-sistance of leukemia [48].

2.11. ACTB is associated with drug-resistance of lymphoma

Bortezomib, a 26S proteasome inhibitor, is one of themost promisingmolecular-targeted approaches for treatment of mantle cell lymphoma(MCL) with up to 40% remission rate in relapsed MCL. ACTB levels weresignificantly decreased in bortezomib-sensitive MCL cells Granta 519,HBL-2, Jeko-1 and Rec-1 in comparison with bortezomib-resistant MCLcell NCEB-1 following treatment with 25 nM bortezomib for up to 4 h[49], suggesting that ACTB plays a critical role in MCL and should betargeted for therapeutic treatment of MCL.

3. Potential mechanisms of action of ACTB in cancer

Several studies have suggested that ACTB polymerization andlocalization might promote cancer cell motility, invasiveness and

Table 1The associations of ATCB with cancers.

Tumor type Expression pattern

Hepatocellular carcinoma (HCC) Up-regulated in HCV-induced and HBV-induced HCC;in tumorous tissues of HCC with higher invasiveness aincreased in Hepatoma Morris 5123 cells with increasACTB polymerization and in N1S1 rat hepatoma.

Melanoma ACTB mRNA levels in invasive melanoma cell T1C3 whigher than that in non-invasive melanoma cell 1C8 mderived from the same melanoma patient.

Renal cell carcinoma (RCC) ACTB significantly increased in ccRCC tissues; ACTB levaried in RCC lines and were marginally higher in matissues versus normal kidney tissues.

Colorectal cancer (CRC) ACTB protein level was down-regulated fourfold inMDA7-transduced CRC DLD-1 cells compared tountransduced-DLD-1 cells; ACTB was not stably and rexpressed in colorectal tumors and matched normal s

Gastric cancer (GC) ACTB showed a 1.4-fold expression increase in gastric ctissues compared to normal tissues at the mRNA level;expressed more positively in GC tissues than in cancer c(SNU-216, SNU-638, SNU-719, AGS, MKN-28, KATOIII, A

Pancreatic cancer (PC) ACTB was up-regulated in PC at both RNA and protein

Esophageal cancer ACTB was up-regulated by 4.4-fold in ESCC at the protedown-regulated at the RNA level by 0.8-fold

Lung cancer ACTB was significantly increased in NSCLC cell lines/NmRNA and protein levels.

Breast cancer (BC) ACTB was highly expressed in metastatic MDA-mb-23ACTB was decreased in leucocytes of BC patients comK562 cells and normal leucocytes; ACTB protein leveldown-regulated fourfold in MDA7-transduced BC T47compared to T47D; ACTB was significantly decreasedcells following treatment with salicylic acid or heat sh

Prostate cancer ACTB was more highly expressed in prostate cancer timatched peritumoral normal tissues.

Ovarian cancer (OC) ACTB was significantly increased in specimens from scompared with normal ovarian epithelial tissues.

Leukemia ACTB DNA concentrations and DNA integrity were higplasma of acute leukemia patients than that in healthACTB was up-regulated more than twofold in RA resisAPL cell line NB4-R1 following treatment with As4S4’

Lymphoma ACTB was significantly decreased in bortezomib-sensilines Granta 519, HBL-2, Jeko-1 and Rec-1 compared tbortezomibresistant MCL cell line NCEB-1.

metastasis [2,4,6,8–11]. ACTB polymerization and ACTB cytoskeletonformation drives cell protrusions and cell motility, which indicatesthat over-expression of ACTB might also enhance cancer cell motility.ACTB mRNA was found to be localized in the protrusions of differenttypes of cancer cells in which ACTB is actively polymerized, and thisability to localize mRNA was correlated with the efficiency of cell mo-tility. Accumulated localization of ACTB mRNAwas proved to be asso-ciated with the metastatic potentials of cancer cells, as delocalizationof ACTB mRNA from cell leading edges was followed by the loss of cellpolarity and directional movement. ACTB expression was significantlyup-regulated in highly invasive variants of different tumor cell lines[4,6,8,11], confirming involvement of ACTB in tumor metastasis.

The differential accumulation of ACTB mRNA in the perinucleus andat the cell leading edge might affect the metastatic capacities of cancercells by affecting the polarity and plasticity of cancer cell motility. Therelevance of the distribution of ACTBmRNA to cancer cellmetastatic po-tential was explored by using rat adenocarcinoma MTLn3 (high meta-static potential) and MTC (low metastatic potential) cell lines. ACTBmRNA was distributed in the perinuclear region and at the leadingedge in MTC cells, but was only distributed at the perinuclear regionof MTLn3 cells. This difference makes MTLn3 cells unpolarized with re-spect to all cell shape andmotility criteria in cell culture and in their his-topathological organization in primary tumors, while MTC cells arepolarized in all these respects. The increased plasticity of cell locomo-tion and invasiveness ofMTLn3 cells result from the failure ofmetastaticcells to localize ACTB mRNA properly, causing them to be less polarized

Implication References

overexpressednd metastasis;ed state of

ACTB is closely associated with liver cancer growthand metastasis.

[1,4,8,18–22]

ere twofoldelanoma cells

ACTB is not a suitable reference gene/protein formelanoma cells from either the same patient or fromheterogeneous cellular subpopulations of the samepathological origin.

[13]

vels greatlylignant renal

ACTB potentially promotes the development ofRCC.

[23,24]

eliablypecimens

ACTB is de-regulated and involved in CRC. [9,27–30]

arcinomaACTB wasell linesGS/SNU-638)

ACTB is associated with GC at the mRNA level [9,21,31]

levels. ACTB is involved in PC and unsuitable as a referencegene/protein.

[21]

in level, while ACTB de-regulation is associated with lung cancer.ACTB up-regulation might be a sign of lung cancercellular tumourigenesis.

[21,32]

SCLC tissues at [34–37]

1 BC cells;pared withwasD cell linesin MCF-7 BCock.

ACTB de-regulation is associated with BC metasta-sis and drug treatment effects on BC.

[30,38–42]

ssue than ACTB might promote prostate cancer. [43,44]

erous OC ACTB might correlate with OC. [45]

her in they controls;tant human

ACTB up-regulation correlates with leukemia and isassociated with its drug resistance.

[46–48]

tive MCL cello

ACTB might enhance drug resistance of lymphoma. [49]

43C. Guo et al. / Clinica Chimica Acta 417 (2013) 39–44

and therefore more flexible in their direction of motility. These resultsmay have prognostic value for predicting the metastatic potential ofcancer cells and cancers [50]. In addition, the increased expressionand redistribution of ACTB to the tips of pseudopodia were associatedwith the motile ability and invasiveness of cancer cells. Comparingto MDCK (Madin-Darby Canine Kidney epithelial cells) and MSV(Moloney sarcoma virus-transformed)-MDCK cells, the up-regulationand specific accumulation of ACTB in the pseudopodia drive the exten-sion of pseudopodia and regulate the invasive and metastatic abilities ofMSV-MDCK-INV (invasive MSV-MDCK cells) [6]. Clearly, the remoldingof the ACTB cytoskeleton could contribute to tumor malignancy. Atthe very least, the dynamic actin polymerization and the cytoskeletonare involved in certain cancers [51–55]. G-actin was found to be signifi-cantly decreased and F-actin was increased in three human colon adeno-carcinoma cell variants (EB3, 3LNLN, 5 W)with highmetastatic potentialand invasiveness, supporting the idea that high levels of actin polymeri-zation are a prerequisite for pseudopod formation and necessary for infil-tration of cancer cells into surrounding tissues [4,11]. Loss of F-actin,poorly arranged ACTB skeleton organization, and the presence ofF-actin aggregates correlated with increased metastatic potential oftumor cells [54]. Another study revealed that ACTB polymerization orACTB remodeling played a pivotal role in regulating the morphologicand phenotypic events of malignant cells [55].

Since ACTB appears to have several as yet poorly understood rolesin carcinogenesis, ACTB polymerization, actin cytoskeleton formationand microfilament actin remodeling could be potential targets fordrug development for prevention and treatment of certain cancers,and studies of ACTB involvement in cancers will likely provide anew perspective on molecular mechanisms of cancer initiation andgrowth.

4. Conclusions

While ACTB has been widely used as a reference gene/protein forquantifying expression in cancers, many studies have found it to bede-regulated in liver, melanoma, renal, colorectal, gastric, pancreatic,esophageal, lung, breast, prostate, ovarian cancers, leukemia and lym-phoma as summarized in Table 1. This de-regulation of ACTB expressionin tumor tissues or cells suggests that 1) caution should be shown inutilizing ACTB as a reference gene/protein even for comparable cells;2) ACTB might be not be an accurate way to normalize different typesof clinical samples; 3) ACTB might be involved in the pathogenesis, in-vasiveness and metastasis of certain cancers; 4) ACTB has potential asa biomarker and as a target for antisense gene therapy for certaintypes of cancer. Although ACTB is well known as a classical housekeep-ing gene, a better understanding of the roles of ACTB in cancers is likelyto provide valuable insights into cancer development and progression.

Acknowledgements

This work was supported by grants from the National Natural ScienceFoundation of China (81050010; 81171957; 81272186) and the KeyLaboratory of the Department of Education of Liaoning (LS2010050).

References

[1] Waxman S, Wurmbach E. De-regulation of common housekeeping genes in hepa-tocellular carcinoma. BMC Genomics 2007;8:243–51.

[2] Bunnell TM, Burbach BJ, Shimizu Y, et al. Beta-actin specifically controls cellgrowth, migration, and the G-actin pool. Mol Biol Cell 2011;22(21):4047–58.

[3] Ruan W, Lai M, et al. Actin, a reliable marker of internal control? Clin Chim Acta2007;385(1–2):1–5.

[4] Nowak D, Krawczenko A, Dus D, et al. Actin in human colon adenocarcinoma cellswith different metastatic potential. Acta Biochim Pol 2002;49(4):823–8.

[5] Pollard TD, Borisy GG. Cellular motility driven by assembly and disassembly ofactin filaments. Cell 2003;112(4):453–65.

[6] Le PU, Nguyen TN, Drolet-Savoie P, et al. Increased beta-actin expression in aninvasive moloney sarcoma virus-transformed MDCK cell variant concentrates tothe tips of multiple pseudopodia. Cancer Res 1998;58(8):1631–5.

[7] Micheva KD, Vallee A, Beaulieu C, et al. Beta-actin is confined to structures havinghigh capacity of remodelling in developing and adult rat cerebellum. Eur J Neurosci1998;10(12):3785–98.

[8] Popow A, Nowak D, Malicka-Blaszkiewicz M, et al. Actin cytoskeleton andbeta-actin expression in correlation with higher invasiveness of selected hepato-ma Morris 5123 cells. J Physiol Pharmacol 2006;57(Suppl. 7):111–23.

[9] Kwon MJ, Oh E, Lee S, et al. Identification of novel reference genes usingmultiplatform expression data and their validation for quantitative gene expres-sion analysis. PLoS One 2009;4(7):e6162–72.

[10] de Kok JB, Roelofs RW, Giesendorf BA, et al. Normalization of gene expressionmeasurements in tumor tissues: comparison of 13 endogenous control genes.Lab Invest 2005;85(1):154–9.

[11] Nowak D, Skwarek-Maruszewska A, Zemanek-Zboch M, et al. Beta-actin in humancolon adenocarcinoma cell lines with different metastatic potential. Acta BiochimPol 2005;52(2):461–8.

[12] Suzuki A, Iizuka A, Komiyama M, et al. Identification of melanoma antigens using aSerological Proteome Approach (SERPA). Cancer Genomics Proteomics 2010;7(1):17–23.

[13] Goidin D, Mamessier A, Staquet MJ, et al. Ribosomal 18S RNA prevails overglyceraldehyde-3-phosphate dehydrogenase and beta-actin genes as internalstandard for quantitative comparison of mRNA levels in invasive and noninvasivehuman melanoma cell subpopulations. Anal Biochem 2001;295(1):17–21.

[14] Jung M, Ramankulov A, Roigas J, et al. In search of suitable reference genes forgene expression studies of human renal cell carcinoma by real-time PCR. BMCMol Biol 2007;8:47–59.

[15] Vila MR, Nicolas A, Morote J, et al. Increased glyceraldehyde-3-phosphate dehy-drogenase expression in renal cell carcinoma identified by RNA-based, arbitrarilyprimed polymerase chain reaction. Cancer 2000;89(1):152–64.

[16] Parkin DM, Bray F, Ferlay J, et al. Global cancer statistics. CA Cancer J Clin2002;55(2):74–108.

[17] Llovet JM, Burroughs A, Bruix J. Hepatocellular carcinoma. Lancet 2003;362(9399):1907–17.

[18] Fu LY, Jia HL, Dong QZ, et al. Suitable reference genes for real-time PCR in humanHBV-related hepatocellular carcinomawith different clinical prognoses. BMC Cancer2009;9:49–59.

[19] Gao Q,Wang XY, Fan J, et al. Selection of reference genes for real-time PCR in humanhepatocellular carcinoma tissues. J Cancer Res Clin Oncol 2008;134(9):979–86.

[20] Blanquicett C, Johnson MR, Heslin M, et al. Housekeeping gene variability in normaland carcinomatous colorectal and liver tissues: applications in pharmacogenomicgene expression studies. Anal Biochem 2002;303(2):209–14.

[21] Rubie C, Kempf K, Hans J, et al. Housekeeping gene variability in normal and cancer-ous colorectal, pancreatic, esophageal, gastric and hepatic tissues. Mol Cell Probes2005;19(2):101–9.

[22] Chang TJ, Juan CC, Yin PH, et al. Up-regulation of beta-actin, cyclophilin andGAPDH in N1S1 rat hepatoma. Oncol Rep 1998;5(2):469–71.

[23] Lopez-Beltran A, Scarpelli M, Montironi R, et al. 2004 WHO classification of therenal tumors of the adults. Eur Urol 2006;49(5):798–805.

[24] Ferguson RE, Carroll HP, Harris A, et al. Housekeeping proteins: a preliminarystudy illustrating some limitations as useful references in protein expressionstudies. Proteomics 2005;5(2):566–71.

[25] Honda K, Yamada T, Hayashida Y, et al. Actinin-4 increases cell motility and pro-motes lymph node metastasis of colorectal cancer. Gastroenterology 2005;128(1):51–62.

[26] Sagynaliev E, Steinert R, Nestler G, et al. Web-based data warehouse on geneexpression in human colorectal cancer. Proteomics 2005;5(12):3066–78.

[27] Andersen CL, Jensen JL, Orntoft TF. Normalization of real-time quantitative re-verse transcription-PCR data: a model-based variance estimation approach toidentify genes suited for normalization, applied to bladder and colon cancerdata sets. Cancer Res 2004;64(15):5245–50.

[28] Kheirelseid EA, Chang KH, Newell J, et al. Identification of endogenous controlgenes for normalisation of real-time quantitative PCR data in colorectal cancer.BMC Mol Biol 2010;11:12–24.

[29] Dydensborg AB, Herring E, Auclair J, et al. Normalizing genes for quantitativeRT-PCR in differentiating human intestinal epithelial cells and adenocarcinomasof the colon. Am J Physiol Gastrointest Liver Physiol 2006;290(5):G1067–74.

[30] Khimani AH, Mhashilkar AM, Mikulskis A, et al. Housekeeping genes in cancer:normalization of array data. Biotechniques 2005;38(5):739–45.

[31] Rho HW, Lee BC, Choi ES, et al. Identification of valid reference genes for gene ex-pression studies of human stomach cancer by reverse transcription-qPCR. BMCCancer 2010;10:240–52.

[32] Liu Z, Feng JG, Tuersun A, et al. Proteomic identification of differentially-expressedproteins in esophageal cancer in three ethnic groups in Xinjiang. Mol Biol Rep2011;38(5):3261–9.

[33] Nguewa PA, Agorreta J, Blanco D, et al. Identification of importin 8 (IPO8) as themost accurate reference gene for the clinicopathological analysis of lung speci-mens. BMC Mol Biol 2008;9:103–23.

[34] Saviozzi S, Cordero F, Lo Iacono M, et al. Selection of suitable reference genes foraccurate normalization of gene expression profile studies in non-small cell lungcancer. BMC Cancer 2006;6:200–9.

[35] Gamez-Pozo A, Sanchez-Navarro I, Nistal M, et al. MALDI profiling of human lungcancer subtypes. PLoS One 2009;4(11):e7731–6.

[36] Chari R, Lonergan KM, Pikor LA, et al. A sequence-based approach to identify referencegenes for gene expression analysis. BMC Med Genomics 2010;3:32–42.

44 C. Guo et al. / Clinica Chimica Acta 417 (2013) 39–44

[37] Lyng MB, Laenkholm AV, Pallisgaard N, et al. Identification of genes for normaliza-tion of real-time RT-PCR data in breast carcinomas. BMC Cancer 2008;8:20–30.

[38] Majidzadeh AK, Esmaeili R, Abdoli N. TFRC and ACTB as the best reference genesto quantify Urokinase Plasminogen Activator in breast cancer. BMC Res Notes2011;4:215–21.

[39] Szabo A, Perou CM, Karaca M, et al. Statistical modeling for selecting housekeepergenes. Genome Biol 2004;5(8):R59–68.

[40] Morse DL, Carroll D, Weberg L, et al. Determining suitable internal standardsfor mRNA quantification of increasing cancer progression in human breast cellsby real-time reverse transcriptase polymerase chain reaction. Anal Biochem2005;342(1):69–77.

[41] Lupberger J, Kreuzer KA, Baskaynak G, et al. Quantitative analysis of beta-actin,beta-2- microglobulin and porphobilinogen deaminase mRNA and their compar-ison as control transcripts for RT-PCR. Mol Cell Probes 2002;16(1):25–30.

[42] Ferreira E, Cronje MJ. Selection of suitable reference genes for quantitativereal-time PCR in apoptosis-induced MCF-7 breast cancer cells. Mol Biotechnol2012;50(2):121–8.

[43] Mori R, Wang Q, Danenberg KD, et al. Both beta-actin and GAPDH are usefulreference genes for normalization of quantitative RT-PCR in human FFPE tissuesamples of prostate cancer. Prostate 2008;68(14):1555–60.

[44] Ohl F, Jung M, Xu C, et al. Gene expression studies in prostate cancer tissue: which ref-erence gene should be selected for normalization? J Mol Med (Berl) 2005;83(12):1014–24.

[45] Li YL, Ye F, Hu Y, et al. Identification of suitable reference genes for gene expressionstudies of human serous ovarian cancer by real-time polymerase chain reaction.Anal Biochem 2009;394(1):110–6.

[46] Valceckiene V, Kontenyte R, Jakubauskas A, et al. Selection of reference genesfor quantitative polymerase chain reaction studies in purified B cells from B cellchronic lymphocytic leukaemia patients. Br J Haematol 2010;151(3):232–8.

[47] Gao YJ, He YJ, Yang ZL, et al. Increased integrity of circulating cell-free DNA inplasma of patients with acute leukemia. Clin Chem Lab Med 2010;48(11):1651–6.

[48] Qi J, Zhang M, He PC, et al. Proteomic study of retinoid acid resistant NB4R1 cellsapoptosis induced by realgar. Zhonghua Xue Ye Xue Za Zhi 2010;31(11):752–7.

[49] Weinkauf M, Zimmermann Y, Hartmann E, et al. 2-D PAGE-based comparison ofproteasome inhibitor bortezomib in sensitive and resistant mantle cell lympho-ma. Electrophoresis 2009;30(6):974–86.

[50] Shestakova EA, Wyckoff J, Jones J, et al. Correlation of beta-actin messenger RNAlocalization with metastatic potential in rat adenocarcinoma cell lines. CancerRes 1999;59(6):1202–5.

[51] Ben-Ze'ev A. Cytoskeletal and adhesion proteins as tumor suppressors. Curr OpinCell Biol 1997;9(1):99–108.

[52] Decloitre F, Cassingena R, Estrade S, et al. Concomitant alterations of microfila-ments and microtubules in human epithelial cells (HBL-100) in relation to theirmalignant conversion. Tumour Biol 1991;12(2):111–9.

[53] Frontelo P, Gonzalez-Garrigues M, Vilaro S, et al. Transforming growth factor beta1 induces squamous carcinoma cell variants with increased metastatic abilitiesand a disorganized cytoskeleton. Exp Cell Res 1998;244(1):420–32.

[54] Liu CR, Ma CS, Ning JY, et al. Differential thymosin beta 10 expression levels andactin filament organization in tumor cell lines with different metastatic potential.Chin Med J (Engl) 2004;117(2):213–8.

[55] Rao J, Li N. Microfilament actin remodeling as a potential target for cancer drugdevelopment. Curr Cancer Drug Targets 2004;4(4):345–54.