HGF-independent potentiation of EGFR action by c-Met

Oncogene. 2011 Aug 18;30(33):3625-35. doi: 10.1038/onc.2011.84. Epub 2011 Mar 21.

Abstract

The c-Met receptor is a potential therapeutic target for non-small cell lung cancer (NSCLC). Signaling interactions between c-Met and the mutant epidermal growth factor receptor (EGFR) have been studied extensively, but signaling intermediates and biological consequences of lateral signaling to c-Met in EGFR wild-type tumors are minimally understood. Our observations indicate that delayed c-Met activation in NSCLC cell lines is initiated by wild-type EGFR, the receptor most often found in NSCLC tumors. EGFR ligands induce accumulation of activated c-Met, which begins at 8 h and continues for 48 h. This effect is accompanied by an increase in c-Met expression and phosphorylation of critical c-Met tyrosine residues without activation of mitogen-activated protein kinase (MAPK) or Akt. Gene transcription is required for delayed c-Met activation; however, phosphorylation of c-Met by EGFR occurs without production of hepatocyte growth factor (HGF) or another secreted factor, supporting a ligand-independent mechanism. Lateral signaling is blocked by two selective c-Met tyrosine kinase inhibitors (TKIs), PF2341066 and SU11274, or with gefitinib, an EGFR TKI, suggesting kinase activity of both receptors is required for this effect. Prolonged c-Src phosphorylation is observed, and c-Src pathway is essential for EGFR to c-Met communication. Pretreatment with pan-Src family kinase inhibitors, PP2 and dasatinib, abolishes delayed c-Met phosphorylation. A c-Src dominant-negative construct reduces EGF-induced c-Met phosphorylation compared with control, further confirming a c-Src requirement. Inhibition of c-Met with PF2341066 and siRNA decreases EGF-induced phenotypes of invasion by ~86% and motility by ~81%, suggesting that a novel form of c-Met activation is utilized by EGFR to maximize these biological effects. Combined targeting of c-Met and EGFR leads to increased xenograft antitumor activity, demonstrating that inhibition of downstream and lateral signaling from the EGFR-c-Src-c-Met axis might be effective in treatment of NSCLC.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • CSK Tyrosine-Protein Kinase
  • Carcinoma, Non-Small-Cell Lung / drug therapy
  • Carcinoma, Non-Small-Cell Lung / pathology*
  • Cell Line, Tumor
  • Epidermal Growth Factor / pharmacology
  • ErbB Receptors / physiology*
  • Hepatocyte Growth Factor / physiology*
  • Humans
  • Lung Neoplasms / drug therapy
  • Lung Neoplasms / pathology*
  • Phosphorylation
  • Protein-Tyrosine Kinases / physiology
  • Proto-Oncogene Proteins c-myc / physiology*
  • Signal Transduction
  • src-Family Kinases

Substances

  • HGF protein, human
  • MYC protein, human
  • Proto-Oncogene Proteins c-myc
  • Epidermal Growth Factor
  • Hepatocyte Growth Factor
  • EGFR protein, human
  • ErbB Receptors
  • Protein-Tyrosine Kinases
  • CSK Tyrosine-Protein Kinase
  • src-Family Kinases
  • CSK protein, human