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


RESULTS
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.


CONCLUSIONS
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 of anti-mitotic monotherapy in clinical situations.
Cheung
Chun Hei Antonio
CH
National Institute of Cancer Research, National Health Research Institutes, Tainan 704, Taiwan ROC. a.cheung@nhri.org.tw
Chen
Huang-Hui
HH
Kuo
Ching-Chuan
CC
Chang
Chi-Yen
CY
Coumar
Mohane S
MS
Hsieh
Hsing-Pang
HP
Chang
Jang-Yang
JY
D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D053148:Caspase 3 / Q000378:metabolism; D053179:Caspase 7 / Q000378:metabolism; D045744:Cell Line, Tumor; D003078:Colchicine / Q000494:pharmacology*; D015536:Down-Regulation; D006801:Humans; D007211:Indoles / Q000494:pharmacology*; D051034:Inhibitor of Apoptosis Proteins; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism*; D008870:Microtubules / Q000187:drug effects / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D000077022:Survivin; D014178:Translocation, Genetic; D014404:Tubulin / Q000378:metabolism*
C488735:6-methoxy-3-(3',4',5'-trimethoxybenzoyl)-1H-indole; D000970:Antineoplastic Agents; C107489:BIRC5 protein, human; D007211:Indoles; D051034:Inhibitor of Apoptosis Proteins; D008869:Microtubule-Associated Proteins; D034741:RNA, Small Interfering; D000077022:Survivin; D014404:Tubulin; C505520:CASP7 protein, human; D053148:Caspase 3; D053179:Caspase 7; D003078:Colchicine