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Arsenic trioxide augments Chk2/p53-mediated apoptosis by inhibiting oncogenic Wip1 phosphatase

Akinori Yoda1, Kyoko Toyoshima, Yasuhide Watanabe

  • 1Department of Physiology and Cell Biology, Faculty of Medical Sciences, Graduate School of Medicine, Kobe University, 7-5-1, Kusunoki-cho, Chuo-ku, Kobe 650-0017, Japan.

The Journal of Biological Chemistry
|May 17, 2008
PubMed

Insights

Arsenic trioxide (ATO) inhibits the Wip1 phosphatase, a key regulator of DNA damage responses. This inhibition is crucial for ATO

Area of Science:

  • Molecular Biology
  • Cancer Research
  • Cell Signaling

Background:

  • The Wip1 phosphatase (PPM1D) is an oncogene induced by DNA damage, suppressing cell cycle arrest and apoptosis by dephosphorylating key kinases like Chk2, Chk1, and ATM.
  • Arsenic trioxide (ATO), a chemotherapeutic agent, activates the Chk2/p53 and p38 MAPK/p53 pathways, inducing apoptosis, particularly in acute promyelocytic leukemia.

Purpose of the Study:

  • To investigate the direct molecular interaction between arsenic trioxide (ATO) and Wip1 phosphatase.
  • To elucidate the role of Wip1 inhibition in ATO-mediated cancer cell apoptosis.

Main Methods:

  • In vitro assays using purified Wip1 and phosphorylated substrates (Chk2, p38).
  • Cell culture experiments involving ectopic Wip1 expression and ATO treatment.
  • siRNA-mediated Wip1 suppression in acute promyelocytic leukemia cells.
  • Analysis of Chk2 and p38 MAPK phosphorylation and activation.

Main Results:

  • ATO directly inhibits Wip1 phosphatase activity in a dose-dependent manner in vitro.
  • Ectopic Wip1 suppresses DNA damage-induced Chk2 and p38 phosphorylation, an effect reversed by ATO.
  • ATO treatment induces Chk2 and p38 MAPK phosphorylation and activation in acute promyelocytic leukemia cells.
  • Wip1 suppression enhances ATO-induced apoptosis, confirming in vivo inhibition of Wip1 by ATO.

Conclusions:

  • Wip1 phosphatase is a direct molecular target of arsenic trioxide (ATO).
  • ATO's inhibition of Wip1 contributes to the activation of apoptotic pathways, enhancing its anti-cancer efficacy.

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