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Identification of a checkpoint modulator with synthetic lethality to p53 mutants

Naoki Harada1, Yoshinori Watanabe, Yasushi Yoshimura

  • 1Pharmaceutical Research Department II, Chugai Pharmaceutical Co. Ltd., Kanagawa, Japan. haradanok@chugai-pharm.co.jp

Anti-Cancer Drugs
|August 9, 2011
PubMed

Insights

Researchers discovered CBP-93872, a novel G(2) checkpoint inhibitor. This drug selectively targets and suppresses the growth of p53-deficient cancer cells by inhibiting Chk1 phosphorylation, offering a potential new cancer therapy.

Area of Science:

  • Cell Biology
  • Molecular Oncology
  • Cancer Therapeutics

Background:

  • The G(2) checkpoint is crucial for DNA repair and cell cycle progression, particularly in cancers with non-functional p53.
  • Disrupting the G(2) checkpoint offers a promising therapeutic strategy for p53-deficient cancers.
  • Targeting the ataxia-telangiectasia-mutated and Rad3-related (ATR) and checkpoint kinase 1 (Chk1) pathway is a key focus in cancer research.

Purpose of the Study:

  • To identify a novel inhibitor of the G(2) checkpoint pathway.
  • To find a compound that selectively suppresses the growth of p53-deficient cancer cells.
  • To investigate the mechanism of action of potential G(2) checkpoint inhibitors.

Main Methods:

  • Development of a high-throughput screening system to detect G(2) checkpoint abrogation in X-irradiated HT-29 cells.
  • Screening for compounds that inhibit the DNA damage-induced G(2) checkpoint.
  • Assessing the effect of identified compounds on cancer cell growth and cell cycle arrest.
  • Investigating the impact of the compound on key cell cycle regulatory proteins like Chk1 and Chk2.

Main Results:

  • Identification of CBP-93872, a guanidine analog, as a potent inhibitor of the G(2) checkpoint.
  • CBP-93872 demonstrated dose-dependent inhibition of the G(2) checkpoint following DNA damage.
  • The compound selectively suppressed the growth of p53-mutated cancer cell lines with wild-type CDKN2A by inducing G(1) arrest.
  • CBP-93872 inhibited Chk1 phosphorylation, leading to decreased phospho-cdc2 Y15, without affecting Chk2 activity.

Conclusions:

  • CBP-93872 acts as a G(2) checkpoint modulator by inhibiting Chk1 phosphorylation.
  • This inhibition leads to synthetic lethality in p53-deficient cells, suggesting selective anti-cancer activity.
  • The findings support the development of Chk1-targeting agents for the treatment of p53-deficient cancers.

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