Abstract 4437: DNA methylation analysis in cisplatin resistant ovarian cancer cells and recurrent ovarian cancer patient samples

Acquisition of platinum resistance following first line platinum therapy is commonly observed in ovarian cancer patients and is a major obstacle to clinical effectiveness. Currently there are no options available to prevent platinum resistance; however, studies show that demethylating agents may resensitize patients to platinum therapy thereby demonstrating DNA methylation as a critical contributor to the development of platinum resistance. Using a cellular model of platinum resistance we have previously shown that resistant cells have increased DNA methyltransferase (DNMT) activity as well as increased global DNA methylation. These observations were dependent on cisplatin induced activation of the Epidermal Growth Factor Receptor (EGFR) which we previously identified as a novel a regulator of DNMT activity and DNA methylation. Inhibition of the EGFR conferred during a platinum resistance paradigm decreased DNMT activity, decreased global methylation and attenuated resistance in our platinum resistant model. We hypothesized that further genome wide analysis of DNA methylation in resistant, parental and EGFR inhibited cell lines at specific CG sites would reveal targets of methylation important for the development of platinum resistance. Using the Illumina 450K methylation array, we found few significant alterations in DNA methylation for given genes between control and cisplatin resistant (CPR) cells. However, additional DNA methylation analysis with the 450K methylation array of patient tumor samples at initial diagnosis as well as after relapse, while not significant, showed similar trends in the data for certain genes namely CSRNP3, LOC400904, LYPD6, MTMR9L, NIPAL4 and RBP7. We are still evaluating the effects of EGFR inhibition in vitro on DNA methylation patterns. We suggest that while the in vitro model of platinum resistance corresponds to patient samples in some aspects, ovarian cancer cells display a great deal of heterogeneity in DNA methylation as described by others and a much larger sample size is necessary to draw concrete conclusions. Current studies are evaluating gene expression in control and resistant cells to validate whether alterations in DNA methylation coincide with changes in expression. Citation Format: Michaela L. Granados, Laurie G. Hudson, Li Luo, Sabrina L. Samudio-Ruiz. DNA methylation analysis in cisplatin resistant ovarian cancer cells and recurrent ovarian cancer patient samples. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4437.