title: Src and FAK mediate cell-matrix adhesion-dependent activation of Met during transformation of breast epithelial cells.
abstract: Cell-matrix adhesion has been shown to promote activation of the hepatocyte growth factor receptor, Met, in a ligand-independent manner. This process has been linked to transformation and tumorigenesis in a variety of cancer types. In the present report, we describe a key role of integrin signaling via the Src/FAK axis in the activation of Met in breast epithelial and carcinoma cells. Expression of an activated Src mutant in non-neoplastic breast epithelial cells or in carcinoma cells was found to increase phosphorylation of Met at regulatory tyrosines in the auto-activation loop domain, correlating with increased cell spreading and filopodia extensions. Furthermore, phosphorylated Met is complexed with beta1 integrins and is co-localized with vinculin and FAK at focal adhesions in epithelial cells expressing activated Src. Conversely, genetic or pharmacological inhibition of Src abrogates constitutive Met phosphorylation in carcinoma cells or epithelial cells expressing activated Src, and inhibits filopodia formation. Interestingly, Src-dependent phosphorylation of Met requires cell-matrix adhesion, as well as actin stress fiber assembly. Phosphorylation of FAK by Src is also required for Src-induced Met phosphorylation, emphasizing the importance of the Src/FAK signaling pathway. However, stimulation of Met phosphorylation by addition of exogenous HGF in epithelial cells is refractory to inhibition of Src family kinases, indicating that HGF-dependent and Src/integrin-dependent Met activation occur via distinct mechanisms. Together these findings demonstrate a novel mechanism by which the Src/FAK axis links signals from the integrin adhesion complex to promote Met activation in breast epithelial cells.
authors.affiliation: Division of Cancer Biology and Genetics, Queen's University Cancer Research Institute, Kingston, Ontario, Canada.
authors.forename: Angela Y
authors.initials: AY
authors.lastname: Hui
authors.forename: Jalna A
authors.initials: JA
authors.lastname: Meens
authors.forename: Colleen
authors.initials: C
authors.lastname: Schick
authors.forename: Shawna L
authors.initials: SL
authors.lastname: Organ
authors.forename: Hui
authors.initials: H
authors.lastname: Qiao
authors.forename: Eric A
authors.initials: EA
authors.lastname: Tremblay
authors.forename: Erik
authors.initials: E
authors.lastname: Schaeffer
authors.forename: Shashi
authors.initials: S
authors.lastname: Uniyal
authors.forename: Bosco M C
authors.initials: BM
authors.lastname: Chan
authors.forename: Bruce E
authors.initials: BE
authors.lastname: Elliott
mesh_terms: D000818:Animals; D002448:Cell Adhesion; D045744:Cell Line, Tumor; D048430:Cell Shape; D002471:Cell Transformation, Neoplastic; D004847:Epithelial Cells / Q000473:pathology; D005260:Female; D051416:Focal Adhesion Protein-Tyrosine Kinases / Q000378:metabolism*; D016023:Integrins; D015674:Mammary Neoplasms, Animal / Q000473:pathology*; D051379:Mice; D010766:Phosphorylation; D019859:Proto-Oncogene Proteins c-met / Q000378:metabolism*; D011554:Pseudopodia; D019061:src-Family Kinases / Q000378:metabolism*
chemical_list: D016023:Integrins; D019859:Proto-Oncogene Proteins c-met; D051416:Focal Adhesion Protein-Tyrosine Kinases; D019061:src-Family Kinases