Abstract 783: Combination treatment with epigallocatechin-3-gallate and sulforaphane sensitize ovarian cancer cells to cisplatin

Abstract

Abstract Objective: A number of tumor suppressor genes (TSGs), responsible for drug resistance in high stages of ovarian cancers, were silenced due to epigenetic mechanisms. Epigallocatechin-3-gallate (EGCG), which is a major component of green tea, is known for its role as a DNA methyltransferase (DNMT) inhibitor. Sulforaphane (SFN), which is derived from broccoli, is known for its role as a histone deacetylation inhibitor. Both of these compounds have anti-cancer effects in a number of cancers including ovarian. The objective of the study is to test whether EGCG and SFN combination treatment can sensitize ovarian cancer cells to cisplatin treatment. Methods: EGCG, SFN and cisplatin combination treatments were applied to A2780/CP20 (cisplatin-resistant) and A2780 (cisplatin-sensitive) cells to determine their effects on sensitization. Cell viability was measured via MTT assay. Flow cytometry analysis was adopted to reveal cell cycle arrest and apoptosis. Real time quantitative PCR was employed to analyze changes in gene expression in response to the combination treatment. Results: For A2780/CP20 cells, 50% inhibiting concentrations (IC50) to cisplatin was lowered from 13 µM to less than 1 µM with combination treatment. For A2780 cells, IC50 was decreased from 3 µM to 1.5 with combination treatment. Apoptosis analyses revealed that SFN can induce apoptosis in A2780/CP20 and A2780 cells, EGCG or cisplatin can potentiate the effect in both cell types. Cell cycle analyses revealed that 28.58% of A2780/CP20 cells were arrested in G2/M phase with SFN treatment alone compared with 14.3% of vehicle treated cells. Additionally, combination treatment leads to an increase to 52.14% of cells in G2/M phase arrest. Furthermore, we found that 20.45% of A2780 cells were arrested in G2/M phase with SFN treatment compared with 8.02% of vehicle-treated cells, while, combination treatment led to a slight increase to 29.33% of cells in the G2/M phase. There is also a synergistic effect on G2/M phase arrest when EGCG, SFN or cisplatin were used together compared with alone in both cell types. On the molecular level, mRNAs of p21 and hMLH1 were upregulated (18.5 and 28.4 fold respectively, P<0.01) in response to SFN treatment in A2780/CP20. Combination treatment leads to an increase to 35 and 76 fold on their expression (P<0.01). In A2780 cells, mRNA of p21 was upregulated (463 fold, P<0.01) in response to SFN treatment compared with vehicle treatment and combination treatment leads to an increase to 888 fold (P<0.01). No significant change in hMLH1 gene expression was detected in A2780 cells. Conclusion: EGCG and SFN can sensitize ovarian cancer cells to cisplatin treatment through enhanced G2/M cell cycle arrest and apoptosis which may occur via upregulation of p21. Upregulation of hMLH1 in A2780/CP20 cells may be responsible for the added sensitivity to cisplatin. 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 783. doi:1538-7445.AM2012-783