Abstract A46: Loss of DOK2 induces carboplatin resistance in ovarian cancer via suppression of apoptosis

Abstract

Abstract Ovarian cancers are highly heterogeneous and while chemotherapy is the preferred treatment many patients are intrinsically resistant or quickly develop resistance. Furthermore, all tumors that recur ultimately become resistant. Recent evidence suggests that epigenetic deregulation may be a key factor in the onset and maintenance of chemoresistance. Epigenetic events are reversible and the identification of genes altered by this mechanism may lead to studies on how to reprogram the process leading up to resistance. We set out to identify epigenetically silenced genes that affect chemoresistance. The epigenomes of a total of 45 ovarian samples were analyzed to identify epigenetically altered genes that segregate with platinum response, and further filtered with expression data to identify genes that were suppressed. A tissue culture carboplatin resistance screen was utilized to functionally validate this set of candidate platinum resistance genes. Our screen identified a number of genes that when suppressed altered the chemoresistance of the cells in culture. One of the validated candidate genes identified through the pooled shRNA screen was DOK2, an adapter protein downstream of tyrosine kinase, which has been shown by others to be a lung cancer tumor suppressor. We show that suppression of DOK2 by short hairpin RNAs in ovarian cell lines conferred resistance to platinum treatment. Functional analysis of loss of DOK2 effect on chemoresistance determined that there was no change in growth or influx or efflux of carboplatin. However, we determined that loss of DOK2 increased growth in soft agar and also increased migratory capabilities. Furthermore the loss of DOK2 decreased the level of apoptosis in response to carboplatin. Furthermore, in cells with reduced DOK2, the level of anoikis was decreased. We have developed a screening methodology that analyzes the epigenome and informatically identifies candidate genes followed by in vitro culture screening of the candidate genes. To validate our screening methodology we further characterized one candidate gene, DOK2, and showed that loss of DOK2 induces chemotherapy resistance by decreasing the level of apoptosis in response to treatment. Citation Format: Michele Vigliotti, Elena Lum, nilanjana Banerjee, Noelle Cutter, Kazimierz O. Wrzeszczynski, Sohail Khan, Sitharthan Kamalakaran, Douglas A. Levine, Nevenka Dimitrova, Robert Lucito. Loss of DOK2 induces carboplatin resistance in ovarian cancer via suppression of apoptosis. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Ovarian Cancer Research: From Concept to Clinic; Sep 18-21, 2013; Miami, FL. Philadelphia (PA): AACR; Clin Cancer Res 2013;19(19 Suppl):Abstract nr A46.