Enhanced stability of microtubules contributes in the development of colchicine resistance in MCF-7 cells
Understanding the mechanism of resistance to tubulin-targeted anticancer drugs is important for improved chemotherapy. In this work, a colchicine-resistant MCF-7 cell line (MCF-7Col30) was generated by the gradual increment of colchicine treatment and the MCF-7Col30 showed ˜8-fold resistance towards colchicine. MCF-7Col30 cells showed ˜2.5-fold resistance against microtubule depolymerizing agents, vinblastine, and nocodazole. In contrast, it displayed more sensitivity towards paclitaxel, a microtubule-polymerizing agent. MCF-7 and MCF-7Col30 cells showed similar sensitivity towards cisplatin. Further, the level of P-glycoprotein did not increase in MCF-7Col30 cells. MCF-7Col30 cells resisted the microtubule depolymerizing effects of colchicine. The time-lapse imaging of individual microtubules in live cells showed that the dynamics of microtubules in MCF-7Col30 cells was suppressed as compared to the parent MCF-7 cells. The levels of tubulin acetylation and glutamylation increased in MCF-7Col30 cells than the parent MCF-7 cells suggesting that microtubules are stabilized in MCF-7Col30 cells. Interestingly, the level of βIII tubulin was increased by 2.3 folds whereas that of βII and βIV tubulin was decreased by 55 and 150%, respectively in MCF-7Col30 cells. The results suggested that the changes in the level of β-tubulin isoforms and the post-translational modifications of microtubules altered the stability and dynamics of microtubules and contributed to the development of colchicine-resistance in MCF-7 cells.