Silencing Survivin Splice Variant 2B Leads to Antitumor Activity in Taxane-Resistant Ovarian Cancer
Department of Biochemistry, University of Puerto Rico, Medical Science Campus, San Juan, Puerto Rico. Clinical Cancer Research
(Impact Factor: 8.72).
06/2011; 17(11):3716-26. DOI: 10.1158/1078-0432.CCR-11-0233
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.
Available from: Pablo E Vivas-Mejia
- "Melt curve analysis was always performed at the end of the PCR reaction. Relative miR-21 expression was calculated with the ΔΔCt-method ,,. "
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ABSTRACT: Cisplatin has been the most accepted drug for the treatment of ovarian cancer for almost 40 years. Although the majority of patients with ovarian cancer respond to front-line platinum combination chemotherapy, many patients will develop cisplatin-resistance disease, which is extremely rapid and fatal. Although various mechanisms of cisplatin resistance have been postulated, the key molecules involved in such resistance have not been identified. MiRNAs are endogenously expressed small non-coding RNAs, which are evolutionarily conserved and function as post-transcriptional regulators of gene expression. Dysregulation of miRNAs have been associated with cancer initiation, progression and drug resistance. The oncogenic miRNA-21, one of the best-studied miRNAs, is upregulated in almost all human cancers. However, the regulation of miR-21 in cisplatin resistant ovarian cancer cells has not been assessed. In this study, we measured the miR-21 expression by real-time PCR and found upregulation of miR-21 in cisplatin resistant compared with cisplatin sensitive ovarian cancer cells. Chromatin immunoprecipitation studies demonstrated the association of the c-Jun transcription factor to the pri-mir-21 DNA promoter regions. Blocking the JNK-1, the major activator of c-Jun phosphorylation, reduced the expression of pre-mir-21 and increased the expression of its well-known target gene, PDCD4. Overexpression of miR-21 in cisplatin sensitive cells decreased PDCD4 levels and increased cell proliferation. Finally, targeting miR-21 reduced cell growth, proliferation and invasion of cisplatin resistant ovarian cancer cells. These results suggest that the JNK-1/c-Jun/miR-21 pathway contributes to the cisplatin resistance of ovarian cancer cells and demonstrated that miR-21 is a plausible target to overcome cisplatin resistance.
Available from: Xiaolin zi
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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.
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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.
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