Cancer Therapy: Preclinical Silencing Survivin Splice Variant 2B Leads to Antitumor Activity in Taxane-Resistant Ovarian Cancer

Purpose: To study the role of survivin and its splice variants in taxane-resistant ovarian cancer. Experimental Design: We assessed the mRNA levels of survivin splice variants in ovarian cancer cell lines and ovarian tumor samples. siRNAs targeting survivin were designed to silence all survivin splice variants (T-siRNA) or survivin 2B (2B-siRNA) in vitro and orthotopic murine models of ovarian cancer. The mechanism of cell death was studied in taxane-resistant ovarian cancer cells and in tumor sections obtained from different mouse tumors. Results: Taxane-resistant ovarian cancer cells express higher survivin mRNA levels than their taxanesensitive counterparts. Survivin 2B expression was significantly higher in taxane-resistant compared with -sensitive cells. Silencing survivin 2B induced growth inhibitory effects similar to silencing total survivin in vitro. In addition, survivin 2B-siRNA incorporated into DOPC (1,2-dioleoyl-sn-glycero-3-phosphocholine) nanoliposomes resulted in significant reduction in tumor growth (P < 0.05) in orthotopic murine models of ovarian cancer, and these effects were similar to T-siRNA-DOPC. The antitumor effects were further enhanced in combination with docetaxel chemotherapy (P < 0.01). Finally, we found a significant association between survivin 2B expression and progression-free survival in 117 epithelial ovarian cancers obtained at primary debulking surgery. Conclusions: These data identify survivin 2B as an important target in ovarian cancer and provide a translational path forward for developing new therapies against this target. Clin Cancer Res; 17(11); 3716– 26. 2011 AACR.