K858, a novel inhibitor of mitotic kinesin Eg5 and antitumor agent, induces cell death in cancer cells

Ryuichiro Nakai, Shin Ichi Iida, Takeshi Takahashi, Tetsuya Tsujita, Seiho Okamoto, Chie Takada, Kazuhito Akasaka, Shunji Ichikawa, Hiroyuki Ishida, Hideaki Kusaka, Shiro Akinaga, Chikara Murakata, Shinobu Honda, Masayuki Nitta, Hideyuki Saya, Yoshinori Yamashita

Research output: Contribution to journalArticlepeer-review

79 Citations (Scopus)


The aim of this study was to investigate the mechanism of inhibition of Eg5 (kinesin spindle protein), a mitotic kinesin that plays an essential role in establishing mitotic spindle bipolarity, by the novel small molecule inhibitor K858. K858 was selected in a phenotype-based forward chemical genetics screen as an antimitotic agent, and subsequently characterized as an inhibitor of Eg5. K858 blocked centrosome separation, activated the spindle checkpoint, and induced mitotic arrest in cells accompanied by the formation of monopolar spindles. Long-term continuous treatment of cancer cells with K858 resulted in antiproliferative effects through the induction of mitotic cell death, and polyploidization followed by senescence. In contrast, treatment of nontransformed cells with K858 resulted in mitotic slippage without cell death, and cell cycle arrest in G1 phase in a tetraploid state. In contrast to paclitaxel, K858 did not induce the formation of micronuclei in either cancer or nontransformed cells, suggesting that K858 has minimal effects on abnormalities in the number and structure of chromosomes. K858 exhibited potent antitumor activity in xenograft models of cancer, and induced the accumulation of mitotic cells with monopolar spindles in tumor tissues. Importantly, K858, unlike antimicrotubule agents, had no effect on microtubule polymerization in cell-free and cellbased assays, and was not neurotoxic in a motor coordination test in mice. Taken together, the Eg5 inhibitor K858 represents an important compound for further investigation as a novel anticancer therapeutic.

Original languageEnglish
Pages (from-to)3901-3909
Number of pages9
JournalCancer Research
Issue number9
Publication statusPublished - 2009 May 1
Externally publishedYes

ASJC Scopus subject areas

  • Oncology
  • Cancer Research


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