Apoptosis and appearance of multinuclear C6 glioma cells after treatment by microtubule poisons

Microtubules play a crucial role in a large number of cellular functions, including chromosome separation during cell division. Microtubule poisons, drugs that perturb microtubule function, are used for the treatment of a number of malignant tumors, although the precise mechanisms of their cytotoxic effect are still not well understood. In this study, we have investigated the effects of two microtubule poisons, colchicine and paclitaxel, on rat astrocytoma C6 cell line in vitro. Cells were incubated 24-72 hours with, or without poisons, fixed and processed for analysis by light and electron microscopy. Both type of drugs displayed effects on the microtubule network of C6 glioma cells observed by electron microscopy. Furthermore, microtubule poisons triggered apoptotic cell death, although the extent of apoptosis was rather low, while the number of cells arrested in mitosis was significant (33% after 24h treatment with paclitaxel). The most striking effect of paclitaxel was obesreved after 72h, when over 66% of cells displayed multiple nuclei, implying that glioma cells escape mitotic arrest, that results in formation of multinucleated cells. The results showed that C6 glioma cells are largely resistant to induction of apoptosis by microtubule poisons, so further studies are needed to examine the possibilities to overcome resistance.