p400 function is required for the adenovirus E1A-mediated suppression of EGFR and tumour cell killing

Chromatin Modifier EP400 Regulates Oocyte Quality and Zygotic Genome Activation in Mice

Epigenetic modifiers that accumulate in oocytes, play a crucial role in steering the developmental program of cleavage embryos and initiating life. However, the identification of key maternal epigenetic regulators remains elusive. In the findings, the essential role of maternal Ep400, a chaperone for H3.3, in oocyte quality and early embryo development in mice is highlighted. Depletion of Ep400 in oocytes resulted in a decline in oocyte quality and abnormalities in fertilization. Preimplantation embryos lacking maternal Ep400 exhibited reduced major zygotic genome activation (ZGA) and experienced developmental arrest at the 2-to-4-cell stage. The study shows that EP400 forms protein complex with NFYA, occupies promoters of major ZGA genes, modulates H3.3 distribution between euchromatin and heterochromatin, promotes transcription elongation, activates the expression of genes regulating mitochondrial functions, and facilitates the expression of rate-limiting enzymes of the TCA cycle. This intricate process driven by Ep400 ensures the proper execution of the developmental program, emphasizing its critical role in maternal-to-embryonic transition.

Prognostic Significance of HMGA1 Expression in Lung Cancer Based on Bioinformatics Analysis

High-mobility group protein 1 (HMGA1) participates in the processes of DNA transcription, replication, recombination, and repair. The HMGA1 gene is expressed abundantly during embryogenesis and is reactivated during carcinogenesis. HMGA1 gene expression has been associated with a high degree of malignancy, metastatic tendency, and poor survival in breast, colon, ovary, and pancreatic cancers. However, its prognostic significance in lung cancer remains unclear. Using publicly available data, HMGA1 was shown to be overexpressed in both small and non-small lung tumors, with higher expression compared to both the adjacent non-malignant lung tissues and non-tumor lung tissues of healthy individuals. Elevated HMGA1 expression could result from lowered HMGA1 methylation and was connected with some clinicopathological features like sex, age, and stage of the disease. The high HMGA1 expression level was connected with shorter overall and first progression survival time among lung adenocarcinoma patients, but not lung squamous cell carcinoma patients. HMGA1 could interact with proteins involved in cellular senescence and cell cycle control (TP53, RB1, RPS6KB1, and CDK1), transcription regulation (EP400 and HMGA2), chromatin assembly and remodeling (LMNB1), and cholesterol and isoprene biosynthesis (HMGCR and INSIG1). Taken together, HMGA1 overexpression could be an essential element of lung carcinogenesis and a prognostic feature in lung cancer.

A novel role mediated by adenoviral E1A in suppressing cancer through modulating decorin

Oncolytic adenovirus is an emerging alternative to current therapeutics. The adenoviral E1A, the first protein expressed upon oncolytic adenoviral infection, has been identified as an antitumor agent, but the mechanisms of its tumor inhibition ability are unclear enough. Decorin is ubiquitous in the extracellular matrix (ECM), which regulates multiple functions through interaction with ECM. Here, we intended to explore the effects of adenoviral E1A on the tumor extracellular matrix during gene therapy. We demonstrated that reduced decorin expression was found in patients with lung cancer. The adenoviral E1A or a mutant adenoviral E1A with Rb-binding ability absent (E1A 30-60aa, 120-127aa deletion) could increase the expression of decorin and down-regulate VEGF, two members of tumor ECM, involved in both vasculogenesis and angiogenesis. E1A/mE1A-mediated suppressing the migration and invasion ability of tumor cells was depended on decorin. E1A interacted with decorin directly and induced the proteasomal degradation of VEGF. In addition, E1A or mE1A can inhibit tumor growth in a subcutaneous lung cancer xenograft model. It suggested that decorin might be a crucial mediator among ECM components for adenoviral E1A-mediated antitumor activities. These studies on adenovirus E1A provide a new mechanism for the emerging therapies of tumor gene therapy.

Sensitisation to mitoxantrone-induced apoptosis by the oncolytic adenovirus Ad∆∆ through Bcl-2-dependent attenuation of autophagy

Anti-apoptotic Bcl-2 is frequently activated in human malignant cells to promote cell survival and inhibit cell death. Replication-selective oncolytic adenoviruses deleted in the functional Bcl-2 homologue E1B19K potently synergise with apoptosis-inducing chemotherapeutic drugs, including mitoxantrone for prostate cancer. Here, we demonstrate that our previously generated oncolytic mutant Ad∆∆ (E1B19K- and E1ACR2-deleted) caused potent synergistic apoptotic cell death in both drug-sensitive 22Rv1, and drug-insensitive PC3 and PC3M prostate cancer cells. The synergistic cell killing was dependent on Bcl-2 expression and was prevented by Bcl-2 knockdown, which led to activation of the autophagy pathway. Mitoxantrone-induced autophagy, which was decreased in combination with Ad∆∆-infection resulting in increased apoptosis. Expression of the viral E1A12S protein alone mimicked the synergistic effects with Ad∆∆ in combination with mitoxantrone while intact wild-type virus (Ad5) had no effect. Early and late-stage inhibition of autophagy by Atg7 knockdown and chloroquine respectively, promoted apoptotic cell killing with mitoxantrone similar to Ad∆∆. These findings revealed currently unexplored actions of E1B19K-deleted oncolytic adenoviruses and the central role of Bcl-2 in the synergistic cell killing. This study suggests that cancers with functional Bcl-2 expression may be selectively re-sensitised to drugs by Ad∆∆.

C-Terminal Binding Protein is Involved in Promoting to the Carcinogenesis of Human Glioma

C-terminal binding protein (CtBP) is responsible for regulating the pathogenesis of a lot of cancer types. However, whether CtBP1/2 is involved in regulating the growth and development of human glioma is still obscure. In the present study presented here, our results firstly reveal that CtBP1/2 deficiency, induced by siRNA interference, disrupts the functional integrity of the MRN complex that is responsible for DNA repair in human glioma cells. The dysfunction of the MRN complex further contributes to the up-regulation of ATM and Rad3-related kinase (ATR) and Chk1 signaling pathway, which inhibits cell cycle progression mediated by CDK2, preparing for the initiation of DNA repair. Under the condition of hypoxia, hypoxia-inducible factor-1α (HIF-1α) can be directly regulated by CDK2 on protein level, playing coordinately regulatory role in the carcinogenesis of human glioma cells. Overall, our findings reveal that CtBP1/2 is essential to promote to human glioma cell growth through maintaining the DNA stability regulated by the MRN/ATR/Chk1/CDK2/HIF-1α signaling pathway.

A Bagged, Partially Linear, Tree-Based Regression Procedure for Prediction and Variable Selection

OBJECTIVES

In genomics, variable selection and prediction accounting for the complex interrelationships between explanatory variables represent major challenges. Tree-based methods are powerful alternatives to classical regression models. We have recently proposed the generalized, partially linear, tree-based regression (GPLTR) procedure that integrates the advantages of generalized linear regression (allowing the incorporation of confounding variables) and of tree-based models. In this work, we use bagging to address a classical concern of tree-based methods: their instability.

METHODS

We present a bagged GPLTR procedure and three scores for variable importance. The prediction accuracy and the performance of the scores are assessed by simulation. The use of this procedure is exemplified by the analysis of a lung cancer data set. The aim is to predict the epidermal growth factor receptor (EGFR) mutation based on gene expression measurements, taking into account the ethnicity (confounder variable) and perform variable selection.

RESULTS

The procedure performs well in terms of prediction accuracy. The scores differentiate predictive variables from noise variables. Based on a lung adenocarcinoma data set, the procedure achieves good predictive performance for EGFR mutation and selects relevant genes.

CONCLUSION

The proposed bagged GPLTR procedure performs well for prediction and variable selection.

Computational extraction of a neural molecular network through alternative splicing

BACKGROUND

Generally, the results of high throughput analyses contain information about gene expressions, and about exon expressions. Approximately 90% of primary protein-coding transcripts undergo alternative splicing in mammals. However, changes induced by alternative exons have not been properly analyzed for their impact on important molecular networks or their biological events. Even when alternative exons are identified, they are usually subjected to bioinformatics analysis in the same way as the gene ignoring the possibility of functionality change because of the alteration of domain caused by alternative exon. Here, we reveal an effective computational approach to explore an important molecular network based on potential changes of functionality induced by alternative exons obtained from our comprehensive analysis of neuronal cell differentiation.

RESULTS

From our previously identified 262 differentially alternatively spliced exons during neuronal cell differentiations, we extracted 241 sets that changed the amino acid sequences between the alternatively spliced sequences. Conserved domain searches indicated that annotated domain(s) were changed in 128 sets. We obtained 49 genes whose terms overlapped between domain description and gene annotation. Thus, these 49 genes have alternatively differentially spliced in exons that affect their main functions. We performed pathway analysis using these 49 genes and identified the EGFR (epidermal growth factor receptor) and mTOR (mammalian target of rapamycin) signaling pathway as being involved frequently. Recent studies reported that the mTOR pathway is associated with neuronal cell differentiation, vindicating that our approach extracted an important molecular network successfully.

CONCLUSIONS

Effective informatics approaches for exons should be more complex than those for genes, because changes in alternative exons affect protein functions via alterations of amino acid sequences and functional domains. Our method extracted alterations of functional domains and identified key alternative splicing events. We identified the EGFR and mTOR signaling pathway as the most affected pathway. The mTOR pathway is important for neuronal differentiation, suggesting that this in silico extraction of alternative splicing networks is useful. This preliminary analysis indicated that automated analysis of the effects of alternative splicing would provide a rich source of biologically relevant information.

Evaluation of apoptogenic adenovirus type 5 oncolytic vectors in a Syrian hamster head and neck cancer model

Human adenovirus (HAdV) vectors are intensely investigated for virotherapy of a wide variety of human cancers. Here, we have evaluated the effect of two apoptogenic HAdV5 vectors in an immunocompetent Syrian hamster animal model of head and neck cancer. We established two cell lines of hamster cheek pouch squamous cell carcinomas, induced by treatment with 9, 10-dimethyl-1, 2-benzanthracene (DMBA). These cell lines, when infected with HAdV5 mutants lp11w and lp11w/Δ55K (which are defective in the expression of either E1B-19K alone or both E1B-19K and E1B-55K proteins) exhibited enhanced apoptotic and cytotoxic responses. The cheek pouch tumor cells transplanted either subcutaneously at the flanks or in the cheek pouches of hamsters readily formed tumors. Intra-tumoral administration of HAdV5 E1B mutants efficiently suppressed the growth of tumors at both sites. Histological examination of orthotopic tumors revealed reduced vascularity and the expression of the viral fiber antigen in virus-administered cheek pouch tumors. These tumors also exhibited increased caspase-3 levels, suggesting virus-induced apoptosis may contribute to tumor growth suppression. Our results suggest that the apoptogenic HAdV5 vectors may have utility for the treatment of human head and neck cancers.

Association of oncolytic adenoviruses with chemotherapies: an overview and future directions

Oncolytic adenoviruses have been used in different preclinical and clinical studies, showing their capacity to kill tumor cells without major adverse events. However, these studies also underline the limitations of this approach. The efficacy of oncolytic adenoviruses is hampered by their limited ability to transduce some tumor types, their lack of selectivity, and their poor dissemination within tumors. In addition, the host immune response may limit oncolytic adenovirus efficacy. Combining oncolytic adenoviruses with chemotherapeutics constitutes an appealing strategy to increase their potency. The first part of this review describes the molecular basis of oncolytic adenoviruses, their use in preclinical studies and clinical trials, their limitations, and strategies to circumvent these limitations. The second part will focus on studies combining oncolytic adenoviruses with chemotherapeutic drugs, including standard chemotherapeutic drugs, molecularly targeted drugs, and other drugs that have been combined with oncolytic adenoviruses. Finally, based on these studies, we describe future directions and general rules that could be followed to identify chemotherapeutic drugs displaying additive/synergistic effects when combined with oncolytic adenoviruses.

Senescence-associated protein p400 is a prognostic marker in renal cell carcinoma

Mutations of the von Hippel-Lindau (VHL) tumor suppressor gene cause hereditary and sporadic renal cell carcinomas (RCCs). The best characterized function of VHL protein is suppression of the α subunit of hypoxia inducible factor (HIF). Additional VHL functions have been reported, including induction of senescence upon loss of VHL mediated by downregulation of the chromatin remodeling factor p400. Induction of senescence either by oncogene activation or inactivation of tumor suppressors is considered a critical feature of mammalian cells by which to suppress tumorigenesis. In the present study, we investigated the relationship between the expression of p400 and patient survival following RCC diagnosis taking advantage of a large and well-documented series of RCC patients with long-term follow-up information. The expression of p400 was measured by immunohistochemistry using a tissue microarray containing tumor tissue samples from 868 RCC patients. Chi-squared tests, Kaplan-Meier curves, Cox regression models and Spearman's rank correlation estimates were used to investigate the possible relationship between p400 expression and Ki-67 proliferative index, clinical and pathological characteristics and patient survival. Complete loss of p400 expression was detected in 64% of all tumor specimens, and decreased p400 expression was associated with advanced tumor stage, higher grade of malignancy and regional lymph node metastasis. Among well-differentiated RCCs, high proliferation (Ki-67 index>10) was found in 12% of carcinomas with an increased p400 expression, compared to 5% of RCCs with decreased p400 expression. Multiple Cox regression indicated that patients with low proliferative tumors and increased p400 expression had a 60% lower cancer-specific mortality risk compared to those affected by low proliferative RCCs with decreased p400 expression. In summary, patients affected by highly proliferative tumors with decreased p400 expression exhibit a poor prognosis by multiple Cox regression. Our data suggest that the highly proliferative, decreased-p400 subgroup of RCCs represents tumors that are characterized by a loss of the tumor-suppressive mechanism of senescence.

HDAC2 phosphorylation-dependent Klf5 deacetylation and RARα acetylation induced by RAR agonist switch the transcription regulatory programs of p21 in VSMCs

Abnormal proliferation of vascular smooth muscle cells (VSMCs) occurs in hypertension, atherosclerosis and restenosis after angioplasty, leading to pathophysiological vascular remodeling. As an important growth arrest gene, p21 plays critical roles in vascular remodeling. Regulation of p21 expression by retinoic acid receptor (RAR) and its ligand has important implications for control of pathological vascular remodeling. Nevertheless, the mechanism of RAR-mediated p21 expression in VSMCs remains poorly understood. Here, we show that, under basal conditions, RARα forms a complex with histone deacetylase 2 (HDAC2) and Krüppel-like factor 5 (Klf5) at the p21 promoter to inhibit its expression. Upon RARα agonist stimulation, HDAC2 is phosphorylated by CK2α. Phosphorylation of HDAC2, on the one hand, promotes its dissociation from RARα, thus allowing the liganded-RARα to interact with co-activators; on the other hand, it increases its interaction with Klf5, thus leading to deacetylation of Klf5. Deacetylation of Klf5 facilitates its dissociation from the p21 promoter, relieving its repressive effect on the p21 promoter. Interference with HDAC2 phosphorylation by either CK2α knockdown or the use of phosphorylation-deficient mutant of HDAC2 prevents the dissociation of Klf5 from the p21 promoter and impairs RAR agonist-induced p21 activation. Our results reveal a novel mechanism involving a phosphorylation-deacetylation cascade that functions to remove the basal repression complex from the p21 promoter upon RAR agonist treatment, allowing for optimum agonist-induced p21 expression.

Genome-wide siRNA screen identifies SMCX, EP400, and Brd4 as E2-dependent regulators of human papillomavirus oncogene expression

An essential step in the pathogenesis of human papillomavirus (HPV)-associated cancers is the dysregulated expression of the viral oncogenes. The papillomavirus E2 protein can silence the long control region (LCR) promoter that controls viral E6 and E7 oncogene expression. The mechanisms by which E2 represses oncogene expression and the cellular factors through which E2 mediates this silencing are largely unknown. We conducted an unbiased, genome-wide siRNA screen and series of secondary screens that identified 96 cellular genes that contribute to the repression of the HPV LCR. In addition to confirming a role for the E2-binding bromodomain protein Brd4 in E2-mediated silencing, we identified a number of genes that have not previously been implicated in E2 repression, including the demethylase JARID1C/SMCX as well as EP400, a component of the NuA4/TIP60 histone acetyltransferase complex. Each of these genes contributes independently and additively to E2-mediated silencing, indicating that E2 functions through several distinct cellular complexes to repress E6 and E7 expression.

Improved potency and selectivity of an oncolytic E1ACR2 and E1B19K deleted adenoviral mutant in prostate and pancreatic cancers

PURPOSE

Replication-selective oncolytic adenoviruses are a promising class of tumor-targeting agents with proven safety in hundreds of patients. However, clinical responses have been limited and viral mutants with higher potency are needed. Here, we report on the generation of a novel set of mutants with improved efficacy in prostate and pancreatic carcinoma models. Currently, no curative treatments are available for late-stage metastatic prostate or rapidly progressing pancreatic cancers.

EXPERIMENTAL DESIGN

Adenovirus type 5 mutants were created with deletions in the E1ACR2 region for tumor selectivity and/or the E1B19K gene for attenuated replication in vivo; all constructs retain the E3 genes intact. Cell-killing efficacy, replication, and cytotoxicity in combination with chemotherapeutics were investigated in normal cells (PrEC and NHBE), seven carcinoma cell lines, and human (PC3 and DU145) and murine (TRAMPC, CMT-64, and CMT-93) tumor models in vivo.

RESULTS

The double-deleted AdDeltaDelta (DeltaE1ACR2 and DeltaE1B19K) mutant had high cell-killing activity in prostate, pancreatic, and lung carcinomas. Replication was similar to wild-type in all tumor cells and was attenuated in normal cells to levels less than the single-deleted AdDeltaCR2 mutant. AdDeltaDelta combined with the chemotherapeutics docetaxel and mitoxantrone resulted in synergistically enhanced cell killing and greatly improved antitumor efficacy in prostate xenografts in vivo. In murine immunocompetent in vivo models efficacy was greater for mutants with the E3B genes intact even in the absence of viral replication, indicating attenuated macrophage-dependent clearance.

CONCLUSIONS

These data suggest that the novel oncolytic mutant AdDeltaDelta is a promising candidate for targeting of solid tumors specifically in combination with chemotherapeutics.

Down-regulation of multiple cell survival proteins in head and neck cancer cells by an apoptogenic mutant of adenovirus type 5

Head and neck squamous cell carcinomas (HNSCC) are one of the leading causes of cancer deaths world wide. Up-regulation of the epidermal growth factor receptor (EGFR) and BCL-2 family anti-apoptosis proteins in these cancers is linked to aggressive tumor growth, metastasis and chemoresistance. Infection of two HNSCC cell lines, SCC25 and CAL27 by an Ad5 mutant (lp11w) defective in coding for the viral anti-apoptosis protein, E1B-19K efficiently induced apoptotic cell death. In cells infected with lp11w there was a dramatic down-regulation of EGFR by apoptosis-dependent and -independent mechanisms. The levels of the anti-apoptotic proteins BCL-2, BCL-xL and MCL-1 were also down-regulated in lp11w-infected cells compared to uninfected or Ad5-RM infected cells. Infection with lp11w also enhanced sensitivity of the HNSCC cells to the chemotherapeutic drug cisplatin. Our results suggest that adenoviral vectors defective in E1B-19K would be valuable for efficient down-regulation of cell survival proteins and EGFR in epithelial cancers and could be exploited as oncolytic agents to treat HNSCCs.

PML involvement in the p73-mediated E1A-induced suppression of EGFR and induction of apoptosis in head and neck cancers

Epidermal growth factor receptor (EGFR) tyrosine kinase is commonly overexpressed in human cancers; however, the cellular mechanisms regulating EGFR expression remain unclear. p53, p63 and p73 are transcription factors regulating many cellular targets involved in controlling the cell cycle and apoptosis. p53 activates EGFR expression, whereas TAp63 represses EGFR transcription. The involvement of p73 in the regulation of EGFR has not been reported. Here, a strong correlation between EGFR overexpression and increased levels of the oncogenic DeltaNp73 isoform in head and neck squamous cell carcinoma (HNSCC) cell lines was observed. Ectopic expression of TAp73, particularly TAp73beta, resulted in suppression of the EGFR promoter, significant downregulation of EGFR protein and efficient induction of cell death in all six EGFR-overexpressing HNSCC cell lines. EGFR overexpression from a heterologous LTR promoter protected lung cancer cells from TAp73beta-induced EGFR suppression and apoptosis. Expression of TAp73beta efficiently induced promyelocytic leukaemia (PML) protein expression and PML knockdown by shRNA attenuated the downregulation of EGFR and induction of apoptosis by p73 in HNSCC cells. Furthermore, PML was found to be important for E1A-induced suppression of EGFR and subsequent killing of HNSCC cells. Our data therefore suggest a novel pathway involving PML and p73 in the regulation of EGFR expression.

Requirements for E1A dependent transcription in the yeast Saccharomyces cerevisiae

BACKGROUND

The human adenovirus type 5 early region 1A (E1A) gene encodes proteins that are potent regulators of transcription. E1A does not bind DNA directly, but is recruited to target promoters by the interaction with sequence specific DNA binding proteins. In mammalian systems, E1A has been shown to contain two regions that can independently induce transcription when fused to a heterologous DNA binding domain. When expressed in Saccharomyces cerevisiae, each of these regions of E1A also acts as a strong transcriptional activator. This allows yeast to be used as a model system to study mechanisms by which E1A stimulates transcription.

RESULTS

Using 81 mutant yeast strains, we have evaluated the effect of deleting components of the ADA, COMPASS, CSR, INO80, ISW1, NuA3, NuA4, Mediator, PAF, RSC, SAGA, SAS, SLIK, SWI/SNF and SWR1 transcriptional regulatory complexes on E1A dependent transcription. In addition, we examined the role of histone H2B ubiquitylation by Rad6/Bre1 on transcriptional activation.

CONCLUSION

Our analysis indicates that the two activation domains of E1A function via distinct mechanisms, identify new factors regulating E1A dependent transcription and suggest that yeast can serve as a valid model system for at least some aspects of E1A function.

Identification of genes differentially expressed as result of adenovirus type 5- and adenovirus type 12-transformation

BACKGROUND

Cells transformed by human adenoviruses (Ad) exhibit differential capacities to induce tumours in immunocompetent rodents; for example, Ad12-transformed rodent cells are oncogenic whereas Ad5-transformed cells are not. The E1A gene determines oncogenic phenotype, is a transcriptional regulator and dysregulates host cell gene expression, a key factor in both cellular transformation and oncogenesis. To reveal differences in gene expression between cells transformed with oncogenic and non-oncogenic adenoviruses we have performed comparative analysis of transcript profiles with the aim of identifying candidate genes involved in the process of neoplastic transformation.

RESULTS

Analysis of microarray data revealed that a total of 232 genes were differentially expressed in Ad12 E1- or Ad5 E1-transformed BRK cells compared to untransformed baby rat kidney (BRK) cells. Gene information was available for 193 transcripts and using gene ontology (GO) classifications and literature searches it was possible to assign known or suggested functions to 166 of these identified genes. A subset of differentially-expressed genes from the microarray was further examined by real-time PCR and Western blotting using BRK cells immortalised by Ad12 E1A or Ad5 E1A in addition to Ad12 E1- or Ad5 E1-transformed BRK cells. Up-regulation of RelA and significant dysregulation of collagen type I mRNA transcripts and proteins were found in Ad-transformed cells.

CONCLUSION

These results suggest that a complex web of cellular pathways become altered in Ad-transformed cells and that Ad E1A is sufficient for the observed dysregulation. Further work will focus on investigating which splice variant of Ad E1A is responsible for the observed dysregulation at the pathway level, and the mechanisms of E1A-mediated transcriptional regulation.

pRB-E2F1 complexes are resistant to adenovirus E1A-mediated disruption

Disruption of pRB-E2F interactions by E1A is a key event in the adenoviral life cycle that drives expression of early viral transcription and induces cell cycle progression. This function of E1A is complicated by E2F1, an E2F family member that controls multiple processes besides proliferation, including apoptosis and DNA repair. Recently, a second interaction site in pRB that only contacts E2F1 has been discovered, allowing pRB to control proliferation separately from other E2F1-dependent activities. Based on this new insight into pRB-E2F1 regulation, we investigated how E1A affects control of E2F1 by pRB. Our data reveal that pRB-E2F1 interactions are resistant to E1A-mediated disruption. Using mutant forms of pRB that selectively force E2F1 to bind through only one of the two binding sites on pRB, we determined that E1A is unable to disrupt E2F1's unique interaction with pRB. Furthermore, analysis of pRB-E2F complexes during adenoviral infection reveals the selective maintenance of pRB-E2F1 interactions despite the presence of E1A. Our experiments also demonstrate that E2F1 functions to maintain cell viability in response to E1A expression. This suggests that adenovirus E1A's seemingly complex mechanism of disrupting pRB-E2F interactions provides selectivity in promoting viral transcription and cell cycle advancement, while maintaining cell viability.

E1A inhibits the proliferation of human cervical cancer cells (HeLa cells) by apoptosis induction through activation of HER-2/Neu/Caspase-3 pathway

OBJECTIVE

This study is to investigate the inhibitory effect of E1A gene on the cell proliferation of HeLa cells and its mechanism related to apoptosis.

METHODS

MTT assay and soft agar colony formation assay were employed to justify the inhibition activity of E1A on the proliferation of HeLa cells transfected with E1A gene. Western Blot, RT-PCR and Real-time quantitative RT-PCR were used to detect the gene expression of E1A, HER-2/Neu and Caspase-3 in HeLa cells, respectively. The Caspase-3 activity was monitored by ApoAlert Caspase-3 Assay. The redistribution of cell cycles and apoptosis of HeLa cells regulated by E1A expression were evaluated by flow cytometry.

RESULTS

E1A expression significantly inhibits the cell proliferation and anchorage-independent cell growth of HeLa, with the respective highest inhibition rate of 40.7% and 43.4% (P < 0.01). HER-2/Neu expression in HeLa was significantly down-regulated by E1A, while the protein expression and activity of Caspase-3 was up-regulated by E1A expression. Flow cytometry revealed that E1A transfection in HeLa increased the cell number at G1 stage and simultaneously decreased the cell number at S stage. E1A transfection induced 8.71% of HeLa cells at apoptosis status.

CONCLUSIONS

E1A significantly inhibits the cell proliferation of HeLa by the apoptosis induction through HER-2/Neu/Caspase-3 pathway. These results encourage us to continue an in-vivo study and preclinical development of LPD-E1A as a novel gene therapeutic agent for human cervical cancer.