Silencing pathways that underlie platinum resistance in ovarian cancer cells using small interfering RNA

Abstract

5117 Background: Primary therapy for women with advanced stage epithelial ovarian cancer includes primary surgical cytoreduction followed by platinum-based chemotherapy. Although nearly 70% of patients demonstrate a complete clinical response to primary therapy, the majority of patients will develop platinum-resistant recurrent disease. Our understanding of this chemo-resistance remains incomplete. The expression of genes such as c-myc have been shown to be associated with chemoresistance in several human cancers. Recently, using microarray expression analysis of 55 primary epithelial ovarian cancers, we demonstrated that members of the c-myc pathway are predictive of response to primary platinum therapy. We hypothesized that increased c-myc gene expression also underlies platinum resistance in ovarian cancer cell lines, and that it can be reduced by use of a c-myc-targeted small interfering RNA (si-cmyc) approach, thus reversing platinum resistance. Methods: Expression of the c-myc gene was measured in platinum-sensitive (OV2008) mother and platinum-resistant (C13) daughter ovarian cancer cell lines using quantitative real time polymerase chain reaction (QRTPCR). Platinum-resistant cells were then subject to c-myc-targeted small interfering RNA (50nM, 100nM and 150nM), and c-myc gene expression was evaluated using Western blot analysis. Platinum-resistant ovarian cancer cells, subject to successful c-myc expression silencing by siRNA, were then evaluated for platinum-response using the MMT assay. Results: Expression of the c-myc gene was 1.78-fold higher in platinum-resistant versus platinum-sensitive ovarian cancer cells. Western blot analysis demonstrated a reduction of c-myc gene expression by 95% in platinum-resistant ovarian cancer cells subject to c-myc-targeted siRNA at 150nM. Conclusions: These findings support the hypothesis that the c-myc gene pathway is an important determinant of platinum-response in ovarian cancer cells. Further, we have demonstrated that siRNA approaches can selectively silence genes that underlie platinum-response and may thus represent a novel targeted molecular therapeutic approach to patients with platinum-resistant ovarian cancer. No significant financial relationships to disclose.