PTK2 and neoplasm: Next, the double phosphorylation on Y576 and Y577 residues triggered by the proto-oncogene tyrosine-protein kinase Src (c-Src) kinase may enhance the FAK catalytic activity [35,47], whereas the phosphorylation of FAK at the K454 and H58 residues is involved in diverse cellular functions such as cell polarity, resistance to apoptosis and tumor growth [48,49,50].