ABSTRACT: Activating transcription factor 3 (ATF3), a stress-inducible gene, is a regulator of cisplatin-induced cytotoxicity, and enhancement of the ATF3 expression potentiates this cytotoxicity.
ATF3 expression and its binding to the transcription target CHOP were evaluated by western blot and chromatin immunoprecipitation (ChIP), respectively, in a panel of five cell lines (WI38, MCF7, PC3, A549). MTT assays were employed to assess the effects of many drugs, including disulfiram, on cell viability.
ATF3 protein expression was up-regulated after cytotoxic doses of cisplatin treatment and it directly bound to the CHOP gene promoter, increasing this pro-apoptotic protein's expression. In a library screen of 1200 compounds, disulfiram, a dithiocarbamate drug, was identified as an enhancer of the cytotoxic effects of cisplatin. This increased cytotoxic action was synergistic and likely due to their ability to induce ATF3 independently.
Understanding the role of ATF3 in cisplatin-induced cytotoxicity will lead to novel therapeutic approaches that could improve this drug's efficacy.
Anticancer research 07/2012; 32(7):2679-88. · 1.73 Impact Factor
ABSTRACT: Activating Transcription Factor (ATF) 3 is a key regulator of the cellular integrated stress response whose expression has also been correlated with pro-apoptotic activities in tumour cell models. Combination treatments with chemotherapeutic drugs, such as cisplatin, and histone deacetylase (HDAC) inhibitors have been demonstrated to enhance tumour cell cytotoxicity. We recently demonstrated a role for ATF3 in regulating cisplatin-induced apoptosis and others have shown that HDAC inhibition can also induce cellular stress. In this study, we evaluated the role of ATF3 in regulating the co-operative cytotoxicity of cisplatin in combination with an HDAC inhibitor.
The HDAC inhibitor M344 induced ATF3 expression at the protein and mRNA level in a panel of human derived cancer cell lines as determined by Western blot and quantitative RT-PCR analyses. Combination treatment with M344 and cisplatin lead to increased induction of ATF3 compared with cisplatin alone. Utilizing the MTT cell viability assay, M344 treatments also enhanced the cytotoxic effects of cisplatin in these cancer cell lines. The mechanism of ATF3 induction by M344 was found to be independent of MAPKinase pathways and dependent on ATF4, a known regulator of ATF3 expression. ATF4 heterozygote (+/-) and knock out (-/-) mouse embryonic fibroblast (MEF) as well as chromatin immunoprecipitation (ChIP) assays were utilized in determining the mechanistic induction of ATF3 by M344. We also demonstrated that ATF3 regulates the enhanced cytotoxicity of M344 in combination with cisplatin as evidenced by attenuation of cytotoxicity in shRNAs targeting ATF3 expressing cells.
This study identifies the pro-apoptotic factor, ATF3 as a novel target of M344, as well as a mediator of the co-operative effects of cisplatin and M344 induced tumour cell cytotoxicity.
Cancer Cell International 01/2010; 10:32. · 1.97 Impact Factor
ABSTRACT: This study compares Breast Cancer 1 (BRCA1) and excision repair cross complementation group 1 (ERCC1) expression as predictive markers and evaluates the in vitro enhancement of platinum sensitivity using targeted agents in sporadic ovarian cancer (OC). A retrospective study was performed of advanced stage OC patients receiving platinum-based chemotherapy. BRCA1 and ERCC1 mRNA expression was determined from frozen tissue of 51 patients. Median overall survival (OS) was longer for patients with lower BRCA1 vs. higher BRCA1 (46 vs.33 months, p = 0.03). High BRCA1 was predictive of poorer OS specifically in patients with residual disease (RD) <2 cm (p = 0.03). There was a non-significant association for patients with lower ERCC1 and RD <2 cm in favor of improved OS and time to progression. Patients who expressed higher levels of both BRCA1 and ERCC1 mRNA had a shorter OS compared to patients with lower levels of either or both transcript (33 vs.46 months, p = 0.04). When Cox proportional modeling was used by representing BRCA1 and ERCC1 mRNA expression as a continuous variable, both emerge as potential predictors of survival. OC cell lines were exposed to chemotherapy in combination with DNA repair pathway inhibitors and cell viability was assessed. In vitro histone deacetylase (HDAC) inhibition increased the sensitivity of A2780s/cp cells to cisplatin and carboplatin but not to taxol, coincident with a significant decrease in BRCA1 and ERCC1 expression, suggesting that this compound directly targets DNA repair. In summary, this study shows that low BRCA1 and ERCC1 expression correlate with improved survival in advanced OC and HDAC inhibition induces synergistic cytotoxicity with platinum in vitro.
International Journal of Cancer 10/2008; 124(4):806-15. · 5.44 Impact Factor