title: Met and c-Src cooperate to compensate for loss of epidermal growth factor receptor kinase activity in breast cancer cells.
abstract: Breast cancers are not responsive to epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKI), although 30% of breast cancers overexpress EGFR. The mechanism of intrinsic resistance to EGFR TKIs in breast cancer is the focus of current studies. Here, we observed that EGFR remains tyrosine phosphorylated in breast cancer cells that proliferate in the presence of EGFR TKIs. In one such cell line, SUM229, inhibiting c-Src kinase activity with either a dominant-negative c-Src or a c-Src TKI decreased EGFR phosphorylation on Tyr(845), Tyr(992), and Tyr(1086) in the presence of EGFR TKIs. Conversely, overexpressing wild-type (wt) c-Src in the EGFR TKI-sensitive breast cancer cell line SUM149 increased EGFR kinase-independent EGFR tyrosine phosphorylation. In addition, in the presence of EGFR TKIs, inhibiting c-Src kinase activity decreased cell growth in SUM229 cells, and overexpressing wt-c-Src increased cell growth in SUM149 cells. We identified the receptor tyrosine kinase Met to be responsible for activating c-Src in SUM229 cells. Inhibiting Met kinase activity with a small molecule inhibitor decreased c-Src phosphorylation and kinase activation. In addition, inhibiting Met kinase activity in SUM229 cells decreased EGFR tyrosine phosphorylation and growth in the presence of EGFR TKIs. Stimulating Met kinase activity in SUM149 cells with hepatocyte growth factor increased EGFR tyrosine phosphorylation and cell growth in the presence of EGFR TKIs. These data suggest a Met/c-Src-mediated signaling pathway as a mediator of EGFR tyrosine phosphorylation and cell growth in the presence of EGFR TKIs.
authors.affiliation: Karmanos Cancer Institute, Wayne State University, Detroit, MI 48201, USA.
authors.forename: Kelly L
authors.initials: KL
authors.lastname: Mueller
authors.forename: Lauren A
authors.initials: LA
authors.lastname: Hunter
authors.forename: Stephen P
authors.initials: SP
authors.lastname: Ethier
authors.forename: Julie L
authors.initials: JL
authors.lastname: Boerner
mesh_terms: D001943:Breast Neoplasms / Q000201:enzymology* / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects; D004338:Drug Combinations; D004789:Enzyme Activation / Q000187:drug effects; D066246:ErbB Receptors / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000077156:Gefitinib; D017228:Hepatocyte Growth Factor / Q000494:pharmacology; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D010766:Phosphorylation; D010879:Piperazines / Q000494:pharmacology; D040081:Protein Array Analysis; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D019859:Proto-Oncogene Proteins c-met / Q000378:metabolism / Q000502:physiology*; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D011799:Quinazolines / Q000494:pharmacology; D013449:Sulfonamides / Q000494:pharmacology; D014407:Tumor Cells, Cultured
chemical_list: C478479:((3Z)-N-(3-chlorophenyl)-3-((3,5-dimethyl-4-((4-methylpiperazin-1-yl)carbonyl)-1H-pyrrol-2-yl)methylene)-N-methyl-2-oxo-2,3-dihydro-1H-indole-5-sulfonamide); D004338:Drug Combinations; D007211:Indoles; D010879:Piperazines; D011799:Quinazolines; D013449:Sulfonamides; D017228:Hepatocyte Growth Factor; D066246:ErbB Receptors; D011505:Protein-Tyrosine Kinases; D019859:Proto-Oncogene Proteins c-met; D016392:Proto-Oncogene Proteins pp60(c-src); D000077156:Gefitinib