Differential regulation of cell motility and invasion by FAK

Cell migration and invasion are fundamental components of tumor cell metastasis. Increased focal adhesion kinase (FAK) expression and tyrosine phosphorylation are connected with elevated tumorigenesis. Null mutation of FAK results in embryonic lethality, and FAK^−/− fibroblasts exhibit cell migration defects in culture. Here we show that viral Src (v-Src) transformation of FAK^−/− cells promotes integrin-stimulated motility equal to stable FAK reexpression. However, FAK^−/− v-Src cells were not invasive, and FAK reexpression, Tyr-397 phosphorylation, and FAK kinase activity were required for the generation of an invasive cell phenotype. Cell invasion was linked to transient FAK accumulation at lamellipodia, formation of a FAK–Src-p130Cas–Dock180 signaling complex, elevated Rac and c-Jun NH₂-terminal kinase activation, and increased matrix metalloproteinase expression and activity. Our studies support a dual role for FAK in promoting cell motility and invasion through the activation of distinct signaling pathways.