Platinum resistance in ovarian cancer continues to be an impediment to clinical effectiveness. While multiple alterations associated with platinum resistance have been proposed, mechanisms responsible for those alterations, particularly epigenetic alterations, are still under investigation. Epigenetic alterations, specifically epigenetic silencing induced by DNA methylation, to genes involved in drug response is a common occurrence in platinum resistance. We have previously published that activation of the Epidermal Growth Factor Receptor (EGFR) in ovarian cancer cells increases activity of DNA methyltransferases (DNMTs) and extended EGFR activation can also increase global DNA methylation. In a concurrent abstract, we show that acute cisplatin treatment activates the EGFR and increases DNMT activity. Our overarching hypothesis for this work is that the EGFR is a key player in the development of platinum resistance by its ability to regulate DNMT activity and DNA methylation and thereby could be a therapeutic target for preventing acquisition of platinum resistance during chemotherapeutic treatment. Here, we show data obtained using a cellular model of platinum resistance that we have generated in the lab. We show that OVCA 433 cells treated repeatedly with increasing doses of cisplatin acquire resistance and demonstrate resistance in a 3D model which is more indicative of the ovarian cancer cell microenvironment. These cisplatin resistant cells (CPR) also display significantly increased DNMT activity compared to passage control (non-resistant) cells, with modest increases in global DNA methylation. While hyperactivation of the EGFR is not observed in this chronic model of cisplatin treatment, we do see a significant decrease in Copper transporter 1 (CTR1) levels in CPR cells. CTR1 is particularly important in cisplatin drug uptake, thus we believe that platinum resistance in CPR cells is due to downregulation of CTR1 potentially by DNA methylation. Current studies are evaluating DNA methylation of CTR1 and other genes that may be contributing to the development of platinum resistance. Future studies inhibiting the EGFR during cisplatin treatment will be imperative in linking cisplatin induced EGFR activation to the changes in DNMT activity and methylation that we are observing in our model of platinum resistance. This work implicates EGFR driven alterations to DNMT activity and DNA methylation as a novel mechanism for development of platinum resistance.

Citation Format: Sabrina L. Samudio-Ruiz, Michaela L. Granados, Laurie G. Hudson. Epigenetic alterations associated with platinum resistance in an ovarian cancer cell model. [abstract]. In: Proceedings of the AACR Precision Medicine Series: Drug Sensitivity and Resistance: Improving Cancer Therapy; Jun 18-21, 2014; Orlando, FL. Philadelphia (PA): AACR; Clin Cancer Res 2015;21(4 Suppl): Abstract nr B46.

©2015 American Association for Cancer Research.
2015