Abstract

Anti-cancer drugs that disrupt mitosis inhibit cell proliferation and induce apoptosis, although the mechanisms of these responses are poorly understood. Here, we characterize a mitotic stress response that determines cell fate in response to microtubule poisons. We show that mitotic arrest induced by these drugs produces a temporally controlled DNA damage response (DDR) characterized by the caspase-dependent formation of γH2AX foci in non-apoptotic cells. Following exit from a delayed mitosis, this initial response results in activation of DDR protein kinases, phosphorylation of the tumour suppressor p53 and a delay in subsequent cell cycle progression. We show that this response is controlled by Mcl-1, a regulator of caspase activation that becomes degraded during mitotic arrest. Chemical inhibition of Mcl-1 and the related proteins Bcl-2 and Bcl-xL by a BH3 mimetic enhances the mitotic DDR, promotes p53 activation and inhibits subsequent cell cycle progression. We also show that inhibitors of DDR protein kinases as well as BH3 mimetics promote apoptosis synergistically with taxol (paclitaxel) in a variety of cancer cell lines. Our work demonstrates the role of mitotic DNA damage responses in determining cell fate in response to microtubule poisons and BH3 mimetics, providing a rationale for anti-cancer combination chemotherapies.

Highlights

  • Microtubule poisons such as taxol disrupt mitotic spindle assembly and delay or arrest proliferating cells in a prometaphase-like state through the prolonged activity of the spindle assembly checkpoint (SAC), which restrains anaphase by inhibiting the widespread destruction of mitotic regulators such as cyclin B1 and securin [1]

  • Cells held in mitosis by microtubule poisons can undergo caspase-dependent apoptosis [2], which is influenced by the duration of the mitotic arrest [3,4], or they can slip out of mitosis after a prolonged period [5,6]

  • Mitotic delay induced by microtubule poisons activates DNA damage signalling and affects subsequent cell cycle progression and apoptosis

Read more

Summary

Introduction

Microtubule poisons such as taxol (paclitaxel) disrupt mitotic spindle assembly and delay or arrest proliferating cells in a prometaphase-like state through the prolonged activity of the spindle assembly checkpoint (SAC), which restrains anaphase by inhibiting the widespread destruction of mitotic regulators such as cyclin B1 and securin [1]. After exit from mitosis [3,6] The balance between these cell fates is likely to determine the effectiveness of microtubule poisons and other anti-mitotic drugs in cancer chemotherapy [3,4,6,7,8,9]. If metaphase is not successfully resolved, apoptosis can be initiated after the anti-apoptotic protein Mcl-1 is degraded, which occurs subsequent to its phosphorylation by CDK1 –cyclin B1 [11,12]. The slow degradation of cyclin B1 even though the SAC is active can

Methods
Results
Discussion
Conclusion
Full Text
Published version (Free)

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call