Objective: To investigate the regulation of the subunits of BRAF-HDAC complex, a gene transcription repression complex, which regulates the interaction of histone methylation, histone acetylation, DNA methylation and DNA repair in response to chemotherapy in ovarian cancer cell lines with different treatment strategies. We hypothesized that combining different epigenetic modifiers with low dose Cisplatin would result in an optimal therapeutic regime for ovarian cancer. Materials and Methods: Two epigenetic modifiers Trichostatin A (TSA), a histone deacetylase inhibitor and 5-aza-2′- deoxycytidine (Decitabine), a demethylating agent were evaluated in different doses alone and in combination with Cisplatin on the expression of subunits of BRAF-HDAC complex, histone methylation, acetylation and the associated pathways affected. Three cell lines, A2780, Hey and SKOV3 were used. Spheroids were grown in serum free medium and injected IP in SCID mice. Western blots confirmed protein expression. Results: Different combinations of TSA, Decitabine and low dose Cisplatin significantly inhibited the expression of the subunits LSD1 and CoREST in the BRAF-HDAC complex, two proteins which together demethylate H3K4 and H3K9. The BRAF-HDAC complex cofactor subunit BRAF35 was also significantly suppressed by the combination treatment. The BRAF-HDAC complex subunit repressor increased significantly after combined treatment. indicating that the combination of TSA, Decitabine and Cisplatin suppresses the expression of H3K4 and H3K9 methylation and increases the expression of Histone H3 lys9/14 and Histone H4 ser1/lys5/lys8/lys12 acetylation. Along with these methylation and acetylation changes, we found a decrease in epithelial-mesenchymal transition, cancer cell proliferation, chemoresistance and pluripotency. Spheroid formation was decreased in vitro and there was no tumor formation in SCID mice in presence of these epigenetic modifiers and low dose Cisplatin. Conclusions: The combination of epigenetic modifiers and low dose Cisplatin can regulate and modify the expression of subunits of BRAF-HDAC complex, resulting in decreased expression of tri- and di- methylated H3K4 and H3K9 and increased acetylation of Histone H3 and H4, subsequently modifying the tumor biology and tumorigenicity of these ovarian cancer cell lines. Further investigation of these mechanisms could provide the development of more effective and less toxic treatment for ovarian cancer.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1041. doi:1538-7445.AM2012-1041

©2012 American Association for Cancer Research
2012