Silencing Survivin Splice Variant 2B Leads to Antitumor Activity in Taxane-Resistant Ovarian Cancer
ABSTRACT To study the role of survivin and its splice variants in taxane-resistant ovarian cancer.
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.
Taxane-resistant ovarian cancer cells express higher survivin mRNA levels than their taxane-sensitive 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.
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.
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ABSTRACT: Array of new targets for investigation as cancer therapeutics has great potential to grow as new splice-variants are identified and characterized in cancer cell-lines and tumor samples. Tumor-specific splice variants are being discovered at an increasing rate and their functions are also investigated in cancer progression. The tumor-specific splice variants whose expression patterns and activities are successfully characterized may become attractive targets for ablation or splicing modification. The extreme specificity of their expression suggests that a variant-specific treatment may allow for targeting of cancerous cells with minimal impact to healthy tissues. Clinical investigation of applying antisense oligonucleotides to down-regulate mRNAs that contribute to cancer cell survival and to modify splicing patterns in muscular dystrophy has shown promising results. These results show that antisense therapy may be applied effectively and safely in humans. As these treatment strategies continue to improve and novel tumor-specific splice-variants are identified, modification of splicing patterns will become an important field of investigation to develop more effective and safe cancer therapies.Indian journal of experimental biology 11/2011; 49(11):836-9.
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ABSTRACT: Integrin-linked kinase (ILK), a multidomain focal adhesion protein serine/threonine kinase, plays an essential role in ovarian carcinoma. There are reports that the expression and activity of ILK are increased in ovarian cancer. To test the hypothesis that ILK pathway mediates the apoptosis of ovarian carcinoma SKOV3 cell influencing the cell survival, we performed these studies. We applied lentivirus transfection, 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl-tetrazolium bromide (MTT), apoptotic proteins expressions assay, and Hoechst to study our hypothesis. We found that silencing of the ILK increases the cell cytotoxic, growth inhibition, and apoptosis. Moreover, after blocking the activation of ILK with ILK shRNA, up-regulation of pro-apoptotic bax expression and down-regulation of the anti-apoptotic bcl-2 expression were found in ovarian cancer SKOV3 cell line. These were associated with an increasing cleaved caspase-3 activity and chromatin condensation of cell nuclear. Furthermore, the expressions of fas and fas ligand (fasL), belonging to the tumor necrosis factor family and controlling the cell apoptosis, were also enhanced. Thus, these findings indicate that both the intrinsic pathway and the extrinsic death receptor pathway are involved in the process that silencing of the ILK gene induces the apoptosis in ovarian carcinoma SKOV3 cell.Journal of Receptor and Signal Transduction Research 03/2012; 32(2):120-7. DOI:10.3109/10799893.2012.660534
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ABSTRACT: This study investigated the effect of shRNA targeting survivin on cultured ovarian cancer cells and on a murine ovarian cancer xenograft. An RNAi plasmid for survivin was transfected into SKOV3 cells, and the effect of shRNA targeting survivin on the expression of survivin was determined. Transmission electron microscopy (TEM), flow cytometry, and TUNEL staining were used to assess apoptosis. The MTT assay was used to measure cell growth and changes in cisplatin sensitivity. SKOV3 cells were injected into nude mice, and the effect of shRNA targeting the survivin gene on tumor growth was assessed. SKOV3 cells transfected with an RNAi plasmid against survivin had increased apoptosis and slower growth. At the molecular level, these cells also had lower expression of survivin. Nude mice inoculated with SKOV3 cells developed cancers, and treatment with shRNA targeting survivin markedly inhibited the growth of these cancers with no obvious side effects. Our studies of SKOV3 cells and ovarian cancer xenografts in nude mice indicate that shRNA targeting survivin has potential for the treatment of ovarian cancer.Journal of Cancer Research and Clinical Oncology 03/2012; 138(7):1221-9. DOI:10.1007/s00432-012-1196-0