RESUMO
In the present study, we compared the dynamics and composition of microtubules in cell lines derived from the human breast adenocarcinoma MCF-7 containing either the wild-type p53 (wt-p53; MN1) or a dominant-negative variant of p53 gene (mut-p53; MDD2). Mut-p53 cells were significantly resistant to the cytotoxicity of the microtubule-targeted drugs (vinca alkaloids and taxanes), as compared with wt-p53 cells. Studies by high-resolution time-lapse fluorescence microscopy in living cells indicated that the dynamics of microtubules of mut-p53 cells were altered in complex ways and were significantly increased as compared with microtubules in wt-p53 cells. The percentage of time microtubules spent in growing and shortening phases increased significantly, their catastrophe frequency increased, and their overall dynamicity increased by 33%. In contrast, their shortening rate and the mean length shortened decreased. Cells containing mut-p53 displayed increased polymerisation of tubulin, increased protein levels of the class IV beta-tubulin isotype, STOP and survivin, and reduced protein levels of class II beta-tubulin isotype, MAP4 and FHIT. We conclude that p53 protein may contribute to the regulation of microtubule composition and function, and that alterations in p53 function may generate complex microtubule-associated mechanisms of resistance to tubulin-binding agents.
