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Activation of the PI3K pathway in cancer through inhibition of PTEN by exchange factor P-REX2a

Barry Fine1, Cindy Hodakoski, Susan Koujak

  • 1Institute for Cancer Genetics and Herbert Irving Comprehensive Cancer Center, Columbia University, 1130 St. Nicholas Avenue, New York, NY 10032, USA.

Science (New York, N.Y.)
|September 5, 2009
PubMed

Insights

Phosphatase and tensin homolog (PTEN) is a tumor suppressor. Researchers found P-REX2a protein interacts with PTEN, inhibiting its activity and promoting cancer cell growth, revealing a new pathway in cancer regulation.

Area of Science:

  • Oncology
  • Molecular Biology
  • Biochemistry

Background:

  • PTEN (phosphatase and tensin homolog on chromosome 10) is a critical tumor suppressor protein.
  • The precise cellular mechanisms regulating PTEN activity are not fully elucidated.
  • Understanding PTEN regulation is crucial for developing targeted cancer therapies.

Purpose of the Study:

  • To identify novel proteins that interact with PTEN.
  • To investigate the functional role of P-REX2a in PTEN regulation and cancer cell proliferation.
  • To explore the therapeutic potential of targeting the PTEN-P-REX2a interaction.

Main Methods:

  • Protein-protein interaction studies to identify PTEN-binding partners.
  • Quantitative PCR to assess P-REX2a mRNA levels in human cancer cells and tumors.
  • Biochemical assays to measure PTEN lipid phosphatase activity.
  • Cell growth and proliferation assays, including soft agar colony formation.
  • Western blotting to detect levels of phosphorylated AKT.

Main Results:

  • P-REX2a was identified as a novel PTEN-interacting protein.
  • P-REX2a mRNA levels were elevated in human cancer cells and specific tumor types with wild-type PTEN and PIK3CA mutations.
  • P-REX2a inhibited PTEN activity and activated the PI3K pathway in a PTEN-dependent manner.
  • P-REX2a promoted cell growth, factor-independent proliferation, and transformation, cooperating with PIK3CA mutants.
  • Depletion of P-REX2a reduced AKT phosphorylation and cell growth in PTEN-intact human cell lines.

Conclusions:

  • P-REX2a acts as a negative regulator of PTEN tumor suppressor activity.
  • P-REX2a is a key component of the PI3K pathway that antagonizes PTEN function in cancer.
  • Targeting P-REX2a may represent a novel therapeutic strategy for cancers with intact PTEN and PI3K pathway activation.

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