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Suppression of TGF-beta signaling by phospholipase D

Noga Gadir1, Evan Lee, Avalon Garcia

  • 1Department of Biological Sciences, Hunter College of the City University of New York, 695 Park Avenue, New York, New York 10021, USA.

Cell Cycle (Georgetown, Tex.)
|November 23, 2007
PubMed

Insights

Elevated phospholipase D (PLD) activity in cancer cells suppresses tumor-suppressing TGF-beta signals. Inhibiting PLD restores TGF-beta signaling, potentially offering new therapeutic strategies for breast and pancreatic cancers.

Area of Science:

  • Oncology
  • Molecular Biology
  • Cell Signaling

Background:

  • MDA-MB-231 breast cancer cells exhibit a survival signal driven by phospholipase D (PLD), involving mTOR and MAP kinase activation.
  • Transforming growth factor-beta (TGF-beta) signaling, which normally inhibits cell cycle progression, is suppressed in these cells.

Purpose of the Study:

  • To investigate the role of elevated phospholipase D (PLD) activity in suppressing TGF-beta signaling in MDA-MB-231 and PANC-1 cancer cells.
  • To elucidate the downstream mechanisms by which PLD impacts TGF-beta pathway components and cell cycle regulators.

Main Methods:

  • Suppression of PLD activity and/or expression in cancer cell lines.
  • Analysis of Smad2 and Smad3 phosphorylation at sites regulated by TGF-beta receptor and MAP kinase.
  • Assessment of cyclin-dependent kinase (CDK) inhibitor expression (p21Cip1, p27Kip1) and pRb phosphorylation.

Main Results:

  • Suppression of PLD activity increased Smad2/3 phosphorylation at TGF-beta receptor-regulated sites, dependent on TGF-beta presence.
  • PLD suppression decreased Smad2 phosphorylation at MAP kinase-regulated sites.
  • Inhibition of PLD led to increased expression of CDK inhibitors p21Cip1 and p27Kip1 and decreased pRb phosphorylation.

Conclusions:

  • Elevated PLD activity in MDA-MB-231 and PANC-1 cells suppresses TGF-beta signaling, contributing to cancer cell survival.
  • The PLD-mediated suppression of TGF-beta signaling is linked to mTOR and MAP kinase pathways.
  • Targeting PLD could restore TGF-beta-induced G(1) arrest, offering a potential therapeutic strategy.

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