Survivin counteracts the therapeutic effect of microtubule de-stabilizers by stabilizing tubulin polymers

• Published in: Molecular cancer 2009-07, Vol.8 (1), p.43-43, Article 43
• Main Authors: Cheung, Chun Hei Antonio, Chen, Huang-Hui, Kuo, Ching-Chuan, Chang, Chi-Yen, Coumar, Mohane S, Hsieh, Hsing-Pang, Chang, Jang-Yang
• Format: Article
• Language: English
• Subjects: Antineoplastic Agents - pharmacology; Apoptosis; Apoptosis - drug effects; Caspase 3 - metabolism; Caspase 7 - metabolism; Cell Line, Tumor; Colchicine - pharmacology; Down-Regulation; Drug resistance; Humans; Indoles - pharmacology; Inhibitor of Apoptosis Proteins; Microtubule-Associated Proteins - genetics; Microtubule-Associated Proteins - metabolism; Microtubules; Microtubules - drug effects; Microtubules - metabolism; Physiological aspects; Risk factors; RNA, Small Interfering - genetics; RNA, Small Interfering - metabolism; Translocation, Genetic; Tubulin - metabolism; Tubulins
• ISSN: 1476-4598; 1476-4598
• DOI: 10.1186/1476-4598-8-43

Survivin is a dual function protein. It inhibits the apoptosis of cells by inhibiting caspases, and also promotes cell growth by stabilizing microtubules during mitosis. Over-expression of survivin has been demonstrated to induce drug-resistance to various chemo-therapeutic agents such as cisplatin (DNA damaging agent) and paclitaxel (microtubule stabilizer) in cancers. However, survivin-induced resistance to microtubule de-stabilizers such as Vinca alkaloids and Combretastatin A-4 (CA-4)-related compounds were seldom demonstrated in the past. Furthermore, the question remains as to whether survivin plays a dominant role in processing cytokinesis or inhibiting caspases activity in cells treated with anti-mitotic compounds. The purpose of this study is to evaluate the effect of survivin on the resistance and susceptibility of human cancer cells to microtubule de-stabilizer-induced cell death. BPR0L075 is a CA-4 analog that induces microtubule de-polymerization and subsequent caspase-dependent apoptosis. To study the relationship between the expression of survivin and the resistance to microtubule de-stabilizers, a KB-derived BPR0L075-resistant cancer cell line, KB-L30, was generated for this study. Here, we found that survivin was over-expressed in the KB-L30 cells. Down-regulation of survivin by siRNA induced hyper-sensitivity to BPR0L075 in KB cells and partially re-stored sensitivity to BPR0L075 in KB-L30 cells. Western blot analysis revealed that down-regulation of survivin induced microtubule de-stabilization in both KB and KB-L30 cells. However, the same treatment did not enhance the down-stream caspase-3/-7 activities in BPR0L075-treated KB cells. Translocation of a caspase-independent apoptosis-related molecule, apoptosis-inducing factor (AIF), from cytoplasm to the nucleus was observed in survivin-targeted KB cells under BPR0L075 treatment. In this study, survivin plays an important role in the stability of microtubules, but not with caspases inhibition. Over-expression of survivin counteracts the therapeutic effect of microtubule de-stabilizer BPR0L075 probably by stabilizing tubulin polymers, instead of the inhibition of caspase activity in cancer cells. Besides microtubule-related caspase-dependent cell death, caspase-independent mitotic cell death could be initiated in survivin/BPR0L075 combination treatments. We suggest that combining microtubule de-stabilizers with a survivin inhibitor may attribute to a better clinical outcome than the use o