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Pharmacological inhibition of Ras-transformed epithelial cell growth is linked to down-regulation of epidermal growth

N Sizemore1, A D Cox, J A Barnard

  • 1Departments of Medicine and Cell Biology, Vanderbilt University and Veterans Affairs Medical Center, Nashville, Tennessee, USA.

Gastroenterology
|August 28, 1999
PubMed
Abstract

Insights

Farnesyl transferase inhibitors (FTIs) block H-Ras-transformed epithelial cell growth by reducing epidermal growth factor receptor (EGFR) ligand production. This selective inhibition offers a targeted approach for cancer therapy.

Area of Science:

  • Oncology
  • Molecular Biology
  • Cell Biology

Background:

  • Posttranslational farnesylation is crucial for Ras protein activation and cell transformation.
  • Farnesyl transferase inhibitors (FTIs) are known to impede protein farnesylation, inhibiting the growth of Ras-transformed cells.
  • Rat intestinal epithelial (RIE-1) cells transformed by activated Ras exhibit a distinct phenotype involving an epidermal growth factor receptor (EGFR) autocrine loop.

Purpose of the Study:

  • To evaluate the efficacy of FTIs in blocking the proliferation of Ras-transformed RIE-1 cells.
  • To investigate the correlation between FTI treatment and the production of EGFR ligands.
  • To elucidate the specific mechanism by which FTIs affect H-Ras-transformed epithelial cells.

Main Methods:

  • Treatment of H-Ras-transformed RIE-1 cells with FTI L744,832.
  • Assessment of cell proliferation and farnesylated H-Ras protein levels.
  • Quantification of transforming growth factor (TGF)-alpha and amphiregulin expression.
  • Evaluation of the effects of exogenous TGF-alpha and EGFR blockade on cell proliferation.

Main Results:

  • FTI L744,832 selectively inhibited the proliferation of H-Ras-transformed RIE-1 cells in a dose-dependent and reversible manner.
  • Growth inhibition correlated with decreased farnesylated H-Ras protein and reduced expression of TGF-alpha and amphiregulin.
  • Exogenous TGF-alpha could overcome the inhibitory effects of L744,832, while combined EGFR blockade enhanced growth inhibition.

Conclusions:

  • FTIs inhibit the growth of H-Ras-transformed epithelial cells by diminishing Ras-induced EGFR ligand production.
  • This mechanism highlights the role of the EGFR autocrine loop in H-Ras-mediated cell transformation.
  • FTIs represent a potential therapeutic strategy targeting specific pathways in epithelial cancers.

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