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PTEN/MMAC1 overexpression decreases insulin-like growth factor-I-mediated protection from apoptosis in neuroblastoma

C M van Golen1, T S Schwab, K M Ignatoski

  • 1University of Michigan Department of Neurology, Neuroscience Program, Ann Arbor, Michigan 48109, USA.

Cell Growth & Differentiation : the Molecular Biology Journal of the American Association for Cancer Research
|July 18, 2001
PubMed

Insights

Insulin-like growth factor I (IGF-I) signaling is modulated by PTEN, which impacts cell survival and growth. PTEN

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Biochemistry

Background:

  • Insulin-like growth factor I (IGF-I) promotes cell survival by activating phosphatidylinositol-3 kinase and Akt.
  • PTEN negatively regulates the PI3K/Akt pathway, controlling cell cycle, migration, and apoptosis.
  • Understanding PTEN's role is crucial for neuroblastoma and cancer research.

Purpose of the Study:

  • To investigate the role of PTEN in modulating IGF-I signaling and cellular responses.
  • To determine how PTEN mutations affect IGF-I-mediated Akt activation and apoptosis.
  • To elucidate PTEN's function in neuroblastoma cell growth and survival.

Main Methods:

  • Overexpression of wild-type PTEN and PTEN mutants (G129E, C124S) in SHEP neuroblastoma cells.
  • Assessment of Akt activity using biochemical assays.
  • Evaluation of apoptosis induction via serum withdrawal and hyperosmotic stress.
  • Measurement of cell growth and IGF-I protection.

Main Results:

  • PTEN overexpression inhibited IGF-I-induced Akt activity, enhanced apoptosis, and reduced cell growth and IGF-I protection.
  • The PTEN lipid phosphatase-dead mutant (G129E) failed to block IGF-I-stimulated Akt activity and apoptosis protection.
  • The PTEN C124S mutant (lacking both lipid and protein phosphatase activity) inhibited growth and serum withdrawal-induced apoptosis but not hyperosmotic-induced apoptosis or Akt activity.

Conclusions:

  • PTEN plays a significant role in regulating IGF-I's effects on Akt activity, neuroblastoma cell growth, and apoptosis.
  • PTEN's lipid phosphatase activity is critical for inhibiting IGF-I-mediated Akt activation and promoting apoptosis.
  • Specific PTEN mutations differentially affect cellular responses to IGF-I and apoptotic stimuli.

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