Transforming growth factor-alpha prevents detachment-induced inhibition of c-Src kinase activity, Bcl-XL down-regulation, and apoptosis of intestinal epithelial cells

J Biol Chem. 2001 Oct 5;276(40):37273-9. doi: 10.1074/jbc.M106424200. Epub 2001 Aug 3.

Abstract

Detachment of epithelial cells from the extracellular matrix (ECM) results in apoptosis, a phenomenon often referred to as anoikis. Acquisition of anoikis resistance is now thought to be a prerequisite for the progression of carcinomas. Colorectal cancer cells frequently secrete epidermal growth factor receptor (EGFR) ligands, which are known to have anti-apoptotic activity. However, whether these ligands have the ability to inhibit anoikis of intestinal epithelial cells is unclear, since at least in some cell types efficient EGFR signaling requires cell-ECM adhesion. Here we report that transforming growth factor-alpha (TGF-alpha), an EGFR ligand that is frequently secreted by colorectal cancer cells, strongly inhibits anoikis of the non-malignant rat intestinal epithelial cell lines, IEC-18 and RIE-1. TGF-alpha exerts its anti-anoikis effect by preventing detachment-induced inhibition of c-Src kinase activity. We also show that Fas activation, a molecular event known to play a critical role in anoikis, is not suppressed by TGF-alpha. On the other hand, this growth factor strongly inhibits the detachment-induced down-regulation of Bcl-X(L), another change that is involved in the induction of anoikis. We further demonstrate that this inhibition occurs in a c-Src-dependent manner. We conclude that TGF-alpha has the ability to suppress anoikis of intestinal epithelial cells, at least in part, by reverting the loss of c-Src activity and Bcl-X(L) expression induced by detachment from the ECM.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apoptosis*
  • CSK Tyrosine-Protein Kinase
  • Caspase 3
  • Caspase Inhibitors
  • Caspases / biosynthesis
  • Cells, Cultured
  • Down-Regulation
  • Enzyme Activation / drug effects
  • Intestinal Mucosa / cytology
  • Intestinal Mucosa / drug effects*
  • Protein-Tyrosine Kinases / antagonists & inhibitors
  • Protein-Tyrosine Kinases / metabolism*
  • Proto-Oncogene Proteins c-bcl-2 / biosynthesis
  • Proto-Oncogene Proteins c-bcl-2 / metabolism*
  • Rats
  • Transforming Growth Factor alpha / pharmacology*
  • bcl-X Protein
  • src-Family Kinases

Substances

  • Bcl2l1 protein, rat
  • Caspase Inhibitors
  • Proto-Oncogene Proteins c-bcl-2
  • Transforming Growth Factor alpha
  • bcl-X Protein
  • Protein-Tyrosine Kinases
  • CSK Tyrosine-Protein Kinase
  • src-Family Kinases
  • Casp3 protein, rat
  • Caspase 3
  • Caspases