Cell fate after mitotic arrest in different tumor cells is determined by the balance between slippage and apoptotic threshold

Microtubule poisons and other anti-mitotic drugs induce tumor death but the molecular events linking mitotic arrest to cell death are still not fully understood. We have analyzed cell fate after mitotic arrest produced by the microtubule-destabilizing drug vincristine in a panel of human tumor cell lines showing different response to vincristine. In Jurkat, RPMI 8226 and HeLa cells, apoptosis was triggered shortly after vincristine-induced mitotic arrest. However, A549 cells, which express a great amount of Bcl-xL and undetectable amounts of Bak, underwent mitotic slippage prior to cell death. However, when Bcl-xL gene was silenced in A549 cells, vincristine induced apoptosis during mitotic arrest. Another different behavior was found in MiaPaca2 cells, where vincristine caused death by mitotic catastrophe that switched to apoptosis when cyclin B1 degradation was prevented by proteasome inhibition. Overexpression of Bcl-xL or silencing Bax and Bak expression delayed the onset of apoptosis in Jurkat and RPMI 8226 cells, enabling mitotic slippage and endoreduplication. In HeLa cells, overexpression of Bcl-xL switched cell death from apoptosis to mitotic catastrophe. Mcl-1 offered limited protection to vincristine-induced cell death and Mcl-1 degradation was not essential for vincristine-induced death. All these results, taken together, indicate that the Bcl-xL/Bak ratio and the ability to degrade cyclin B1 determine cell fate after mitotic arrest in the different tumor cell types.

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► Vincristine induces cell death by apoptosis or mitotic catastrophe.
► Apoptosis-proficient cells die by apoptosis during mitosis upon vincristine treatment.
► p53wt apoptosis-deficient cells undergo apoptosis from a G1-like tetraploid state.
► p53mt apoptosis-deficient cells can survive and divide giving rise to 8N cells.