title: HGF rescues colorectal cancer cells from EGFR inhibition via MET activation.
abstract: OBJECTIVE
  Cetuximab, an antibody targeting the epidermal growth factor receptor (EGFR), is active in colorectal cancer (CRC). However, response rates range from only 10% to 20%. Here, we investigate hepatocyte growth factor (HGF)-dependent mesenchymal-epithelial transition factor (MET) activation as a mediator of cetuximab resistance through signal diversification in CRC cell lines.
  
  
  METHODS
  DiFi, GEO, and LIM1215 cells were treated with varying concentrations and combinations of EGF, HGF, cetuximab, and PHA-665752 (a highly specific MET kinase inhibitor). Biological end points included proliferation, cell cycle arrest, and apoptosis. Proliferation was measured using WST-1 assays and synergy investigated via isobolograms. Expression and signaling were examined using immunoblotting.
  
  
  RESULTS
  EGFR and MET are coexpressed in these CRC cell lines, and dual receptor activation synergistically increased proliferation. Cetuximab inhibited cell growth by 60%-80% with an associated dephosphorylation of EGFR, MAPK, and/or AKT. Addition of HGF to cetuximab-treated cells phosphorylated MET, but not EGFR or ErbB3, restimulated the MAPK and AKT pathways, restored cell proliferation, and rescued cells from G1 arrest and apoptosis. Importantly, this effect could be abrogated by inhibiting MET activation with PHA-665752 or by downregulating MET expression with RNAi.
  
  
  CONCLUSIONS
  HGF-induced MET activation is a novel mechanism of cetuximab resistance in CRC. Inhibition of the HGF-MET pathway may improve response to EGFR inhibitors in CRC, and combination therapy should be further investigated.
authors.affiliation: Department of Surgery, Memorial Sloan-Kettering Cancer Center, New York, NY 10065, USA.
authors.forename: David
authors.initials: D
authors.lastname: Liska
authors.forename: Chin-Tung
authors.initials: CT
authors.lastname: Chen
authors.forename: Thomas
authors.initials: T
authors.lastname: Bachleitner-Hofmann
authors.forename: James G
authors.initials: JG
authors.lastname: Christensen
authors.forename: Martin R
authors.initials: MR
authors.lastname: Weiser
mesh_terms: D000911:Antibodies, Monoclonal / Q000494:pharmacology / Q000627:therapeutic use*; D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents / Q000494:pharmacology; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D000068818:Cetuximab; D015179:Colorectal Neoplasms / Q000188:drug therapy* / Q000378:metabolism*; D019008:Drug Resistance, Neoplasm / Q000187:drug effects; D066246:ErbB Receptors / Q000037:antagonists & inhibitors* / Q000378:metabolism; D017228:Hepatocyte Growth Factor / Q000494:pharmacology*; D006801:Humans; D019859:Proto-Oncogene Proteins c-met / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D015533:Transcriptional Activation / Q000187:drug effects
chemical_list: D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents; D017228:Hepatocyte Growth Factor; D066246:ErbB Receptors; D019859:Proto-Oncogene Proteins c-met; D000068818:Cetuximab