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Nuclear PTEN-mediated growth suppression is independent of Akt down-regulation

Juinn-Lin Liu1, Xiaoyang Sheng, Zsuzsanna K Hortobagyi

  • 1Brain Tumor Center, Department of Neuro-Oncology, UT M. D. Anderson Cancer Center, 1515 Holcombe Blvd., Box 431, Houston, Texas 77030, USA. .

Molecular and Cellular Biology
|July 1, 2005
PubMed

Insights

Nuclear PTEN suppresses tumor growth and induces cell cycle arrest independently of Akt. This finding reveals a novel Akt-independent pathway for PTEN tumor suppression.

Area of Science:

  • Molecular Biology
  • Cancer Research
  • Cell Biology

Background:

  • The tumor suppressor gene PTEN is frequently inactivated in human cancers.
  • PTEN is a phosphoinositide phosphatase found in both the cytoplasm and nucleus.
  • Subcellular localization influences PTEN's biological functions.

Purpose of the Study:

  • To investigate the relationship between PTEN's subcellular localization and its growth-suppressive activities.
  • To determine if nuclear PTEN can induce cell cycle arrest independently of Akt signaling.

Main Methods:

  • Constructed PTEN mutants targeting specific subcellular compartments (e.g., nuclear, membrane).
  • Assessed the effects of PTEN mutants on anchorage-independent growth and G1 arrest in U251MG cells.
  • Investigated the role of the lipid phosphatase domain and Akt signaling in PTEN-mediated growth suppression.

Main Results:

  • Nuclear PTEN suppressed anchorage-independent growth and induced G1 arrest without inhibiting Akt.
  • PTEN's growth suppression in the nucleus requires a functional lipid phosphatase domain.
  • p70S6K down-regulation was partly mediated by AMP-activated protein kinase in an Akt-independent manner.
  • A constitutively active Akt mutant only partially rescued nuclear PTEN-induced growth suppression.

Conclusions:

  • PTEN can induce G1 cell cycle arrest through an Akt-independent signaling pathway.
  • Nuclear localization is critical for PTEN's ability to suppress growth via this novel pathway.
  • These findings offer new insights into PTEN's tumor suppressor mechanisms.

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