PTK2 protein tyrosine kinase 2 (PTK2), also known as focal adhesion kinase (FAK), is a protein that, in humans, is encoded by the PTK2 gene.[4] PTK2 is a focal adhesion-associated protein kinase involved in cellular adhesion (how cells stick to each other and their surroundings) and spreading processes (how cells move around).[5] It has been shown that when FAK was blocked, breast cancer cells became less metastatic due to decreased mobility.[6]