Abstract
Mitotic inhibitors are widely utilized chemotherapeutic agents that take advantage of mitotic defects in cancer cells. We have identified a novel class of piperazine-based mitotic inhibitors, of which AK301 is the most potent derivative identified to date (EC50 < 200 nM). Colon cancer cells arrested in mitosis with AK301 readily underwent a p53-dependent apoptosis following compound withdrawal and arrest release. This apoptotic response was significantly higher for AK301 than for other mitotic inhibitors tested (colchicine, vincristine, and BI 2536). AK301-treated cells exhibited a robust mitosis-associated DNA damage response, including ATM activation, γH2AX phosphorylation and p53 stabilization. The association between mitotic signaling and the DNA damage response was supported by the finding that Aurora B inhibition reduced the level of γH2AX staining. Confocal imaging of AK301-treated cells revealed multiple γ-tubulin microtubule organizing centers attached to microtubules, but with limited centrosome migration, raising the possibility that aberrant microtubule pulling may underlie DNA breakage. AK301 selectively targeted APC-mutant colonocytes and promoted TNF-induced apoptosis in p53-mutant colon cancer cells. Our findings indicate that AK301 induces a mitotic arrest state with a highly active DNA damage response. Together with a reversible arrest state, AK301 is a potent promoter of a mitosis-to-apoptosis transition that can target cancer cells with mitotic defects.
Highlights
Mitosis is an intricate process in actively dividing cells, orchestrating a myriad of kinases and signaling pathways
We show that the most potent of these compounds, AK301, is effective at inducing a mitosis-to-apoptosis transition in the absence of a death ligand in p53-normal colon cancer cells
Cells arrested in mitosis by other agents have been reported to activate ataxia telangiectasia mutated (ATM) and components of the DNA damage response pathway, AK301 arrests cells in a state in which this response is especially robust [21]
Summary
Mitosis is an intricate process in actively dividing cells, orchestrating a myriad of kinases and signaling pathways. Ascribing to this complexity, mitosis is a sensitive phase of the cell cycle [1]. A number of mitotic checkpoints ensure the fidelity of chromosome segregation and cytokinesis; failure of mitotic checkpoints often results in chromosomal alterations, culminating in mitotic catastrophe or cancer-promoting chromosomal instability [2, 3]. Cancer cells often lack important cell cycle checkpoints and may execute mitosis with improper spindle assembly [2]. Mitotic inhibitors are among the most widely utilized chemotherapeutic agents in PLOS ONE | DOI:10.1371/journal.pone.0153818. Mitotic inhibitors are among the most widely utilized chemotherapeutic agents in PLOS ONE | DOI:10.1371/journal.pone.0153818 April 20, 2016
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