Malignant melanoma is refractory to various chemotherapeutics including antitubulin agents such as paclitaxel. Previous studies have suggested a link between βIII-tubulin overexpression and paclitaxel resistance through alterations in the properties of the mitotic spindle. We found that paclitaxel treatment induced temporary mitotic arrest in 7 melanoma cell lines irrespective of the βIII-tubulin level, suggesting that βIII-tubulin had no significant influence on spindle properties. On the other hand, the amount of BCL2, an anti-apoptotic protein, was well correlated with paclitaxel resistance. Treatment of the paclitaxel-resistant cell lines with ABT-737, an inhibitor of BCL2 and BCLxL, or simultaneous knock-down of BCL2 and BCLxL dramatically increased the cells' sensitivity, while knock-down of MCL1, another member of the BCL2 family, had only a minimal effect. Our results suggest that the paclitaxel sensitivity of melanoma cells is attributable to apoptosis susceptibility rather than a change in spindle properties and that BCL2 and BCLxL play a pivotal role in the former.
Keywords: BCL2; BCLxL; apoptosis; melanoma; paclitaxel.
© 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.