Abstract 535A: The tyrosine kinase Src co-operates with the ERM family member ezrin to promote Met activation and ECM degradation in a breast epithelial cell model

Over-expression and aberrant activation of the Met proto-oncogene frequently occurs in invasive breast cancer, and is linked with poor patient prognosis. We and others have shown that the tyrosine kinase Src mediates cell-adhesion dependent activation of Met in the absence of ligand (JCB 107:1168-81, 2009). We have also shown that Src acts co-operatively with the membrane cytoskeletal crosslinker ezrin to disrupt cell-cell contacts, and to increase cell spreading and scattering, all characteristics of epithelial-to-mesenchymal transition (EMT) (JCB 92:16-28, 2004). We therefore examined the role of Src and ezrin in Met activation and invasion of breast epithelial cells. As a model, we used the HC11 breast epithelial cell line expressing various combinations of activated Src and ezrin mutants, as well as a dominant negative ezrin mutant. In contrast to activated Src, which promotes the phosphorylation and hence activation of Met and cell spreading, activated ezrin alone induces the formation of numerous filopodia-like structures, but not Met phosphorylation or cell spreading. Co-activation of Src and ezrin produces a combination of both cell spreading and filopodia-like structures, and strongly increases Met phosphorylation over levels resulting from activated Src alone. Interestingly, Src/ezrin co-operativity dramatically increases tyrosine-phosphorylation of cortactin and MMP2 expression, resulting in the formation of invadopodia and extracellular matrix degradation, a hallmark feature of invading cancer cells. However expression of a dominant negative ezrin domain (aa1-309) abolishes Src and ezrin-induced morphological phenotypes, as well as Src-dependent Met phosphorylation and invadopodia formation, suggesting an important requirement for ezrin in these processes. These findings implicate the Src/ezrin axis in regulating adhesion-dependent Met activation and invadopodia formation, and may provide important clues toward treatment strategies for invasive breast tumors which exploit this signaling pathway (Supported by CBCRA and CIHR). Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 535A.