Cell cycle‐dependent cytotoxicity and mitotic spindle checkpoint dependency of investigational and approved antimitotic agents

Abstract

The mitotic spindle checkpoint (SPC) is a highly regulated mechanism in eukaryotic cells that ensures the even distribution of the duplicated genome between daughter cells. Malfunction of the SPC or deregulated expression of SPC regulatory proteins is frequently associated with a poor response to chemotherapeutic agents. We investigated various approved and investigational mitosis‐specific agents, including spindle poisons, an Eg5 kinesin inhibitor, inhibitors of polo‐like kinase 1 (Plk1) or Aurora‐B kinase, a benzamide class HDAC inhibitor and compounds identified in a chemical genetics screen for their cell cycle‐dependent cytotoxicities and for their activities toward SPC deficient (HT29, Caco‐2, T47D) and SPC proficient human cell lines (A2780, HCT116, SW480). Using the RKOp27 cell system that allows inducible cell cycle arrest by the tunable expression of the cdk inhibitor p27Kip1, we found an exquisite proliferation‐dependent cytotoxicity for all compounds except the aurora kinase inhibitor VX‐680. Cytotoxicity of the antimitotic compounds was in general higher on SPC proficient than on deficient cells. We found two exceptions, a benzamide HDAC inhibitor which was effective on SPC proficient and deficient cells and an investigational compound, BYK72767, with a yet unknown mode of action. The degree of increased mitotic index was no predictor of cytotoxicity of the compounds nor was the phosphorylation of BubR1. However, SPC deficient cell lines were able to tolerate mitotic arrest for far longer times than SPC proficient cells. We conclude that targeting of SPC deficient cancers with novel antimitotic principles remains a challenge but certain drug classes may be equally efficacious regardless of SPC status.

The GTPase Gem and its partner Kif9 are required for chromosome alignment, spindle length control, and mitotic progression

“…S1A), suggesting that the spindle checkpoint is active in Gem-depleted cells, and therefore that Gem is unlikely to be involved in this checkpoint. Furthermore, depletion of Gem from T47D cells, which are deficient in the spindle checkpoint (25,26), failed to induce prometaphase accumulation (Supplemental Fig. S1B).…”

Mitotic Exit Dysfunction through the Deregulation of APC/C Characterizes Cisplatin-Resistant State in Epithelial Ovarian Cancer

“…Several mitotic targeted therapies are being explored in cancers including EOC (8), such as inhibitors of the mitotic entry regulator Cyclin-dependent kinase 1, the mitotic kinase Aurora-kinase A, and the mitotic kinesin Eg5 (11). Most of the mitotic targeting drugs induce spindle checkpoint mediated cell death by directly disrupting mitotic spindle apparatus(12)(13). Cancer cells that are deficient in spindle checkpoint activity can exhibit tolerance to these approaches(14)(15).…”

(Z)-1-Aryl-3-arylamino-2-propen-1-ones, Highly Active Stimulators of Tubulin Polymerization: Synthesis, Structure–Activity Relationship (SAR), Tubulin Polymerization, and Cell Growth Inhibition Studies

“…Concurrently to the accumulation of phospho-histone H3, the protein levels of both cyclin B1 (2.5 fold) and PLK-1(2.5 fold) increased after 6 h of treatment. The expression of these proteins is known to be closely linked to progression through mitosis. − Phosphorylation of BubR1 is a useful marker of mitotic arrest due to the activation of the spindle checkpoint, , so we next analyzed the phosphorylation status of this protein. Similar to histone H3 and Bcl-2, BubR1 (2.95-fold) became phosphorylated at 6 h following treatment of cancer cells with 10ae .…”