Focal adhesion kinase family is a newly defined kinase family which consists of two family members, FAK (PTK2) and PYK2. The first FAK family member is FAK (PTK2) which was found as an integrin-dependent phosphorylated protein. Integrin-mediated cell adhesion causes phosphorylation of FAK, a 120 kDa protein. FAK is the first identified signaling molecule among integrins.
A functional FAK is required for embryonic development. Results have shown that disruption of FAK in mice is embryonic lethal and a pronounced defect in cell migration. Current studies have shown that FAK expression is associated with cancer. Increased FAK mRNA expression was observed in most cancer tissue samples but not in normal samples. Another study also showed that the increased level is relative high with a 100% increase in colon tumor samples. The mechanism of increased FAK expression is still under investigation. Furthermore, FAK also has a role in angiogenesis as FAK is expressed in the developing vasculature during embryogenesis.