Multimodal Effects of Small Molecule ROCK and LIMK Inhibitors on Mitosis, and Their Implication as Anti-Leukemia Agents

Yusuke Oku,Kentaro Yoshida,Shinichi Takaya,Naoyuki Nishiya,Haruki Ujiie,Yoshimasa Uehara,Sayaka Osaka,Chiaki Tareyanagi,Qiliang Cai

doi:10.1371/journal.pone.0092402

Yusuke Oku, Kentaro Yoshida + Show 7 more

Open Access

https://doi.org/10.1371/journal.pone.0092402

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Journal: PLoS ONE	Publication Date: Mar 18, 2014
Citations: 56	License type: CC BY 4.0

Affiliation: Iwate Medical University

Abstract

Accurate chromosome segregation is vital for cell viability. Many cancer cells show chromosome instability (CIN) due to aberrant expression of the genes involved in chromosome segregation. The induction of massive chromosome segregation errors in such cancer cells by small molecule inhibitors is an emerging strategy to kill these cells selectively. Here we screened and characterized small molecule inhibitors which cause mitotic chromosome segregation errors to target cancer cell growth. We screened about 300 chemicals with known targets, and found that Rho-associated coiled-coil kinase (ROCK) inhibitors bypassed the spindle assembly checkpoint (SAC), which delays anaphase onset until proper kinetochore-microtubule interactions are established. We investigated how ROCK inhibitors affect chromosome segregation, and found that they induced microtubule-dependent centrosome fragmentation. Knockdown of ROCK1 and ROCK2 revealed their additive roles in centrosome integrity. Pharmacological inhibition of LIMK also induced centrosome fragmentation similar to that by ROCK inhibitors. Inhibition of ROCK or LIMK hyper-stabilized mitotic spindles and impaired Aurora-A activation. These results suggested that ROCK and LIMK are directly or indirectly involved in microtubule dynamics and activation of Aurora-A. Furthermore, inhibition of ROCK or LIMK suppressed T cell leukemia growth in vitro, but not peripheral blood mononuclear cells. They induced centrosome fragmentation and apoptosis in T cell leukemia cells. These results suggested that ROCK and LIMK can be a potential target for anti-cancer drugs.

Highlights

Aneuploidy is a common feature of cancer cells, found in about 90% of solid human tumors and .50% of hematopoietic cancers [1]
We found that Rho-associated coiled-coil kinase (ROCK) and LIMK inhibitors are effective against T cell leukemia cells in vitro by inducing centrosome fragmentation and apoptosis, but not against peripheral blood mononuclear cells
To address whether ROCK inhibitors inhibit spindle assembly checkpoint (SAC) directly, we examined the degradation of cyclin B1 in nocodazole-arrested cells treated with ROCK inhibitors

Summary

Introduction

Aneuploidy is a common feature of cancer cells, found in about 90% of solid human tumors and .50% of hematopoietic cancers [1]. Many genes involved in chromosome segregation are mutated or aberrantly expressed in cancer cells [2,3]. These abnormalities lead to chromosome instability through defects in sister chromatid cohesion, problems in kinetochore-microtubule interactions, and defective spindle assembly checkpoint (SAC) [1]. SAC is one of the best characterized systems for maintaining chromosome stability, and is activated at every cell cycle after entry into mitosis. It represents a ‘wait anaphase’ signal that is elicited by the presence of unattached kinetochores. Higher concentrations of paclitaxel induce multiple asters, leading to SAC satisfaction [14]

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