Focal adhesion kinase (FAK) was first identified as a highly phosphorylated substrate of the viral Src oncogene product (v-Src) localized to the integrin cluster of focal adhesions. FAK is ubiquitously expressed and functions as a non-receptor cytoplasmic tyrosine kinase as well as a scaffold protein, mediating and regulating specific signals initiated at sites of integrin-mediated cell-extracellular matrix (ECM) attachment, as well as those triggered by activated growth factor receptors. Several types of signaling events initiate FAK activation, such as such as epithelial growth factor (EGF), hepatocyte growth factor (HGF), vascular endothelial growth factor (VEGF) and platelet derived growth factor (PDGF), activation of particular G-protein-coupled receptors, and the binding of interacting partners of the FAK FERM domain such as ezrin in an integrin-independent manner. FAK plays an integral role in tumorigenesis by promoting sustained proliferative and survival signals. 
Signalling from the FAK/Src complex to Akt1 and extracellular signal-regulated kinase 1/2 (Erk1/2) has been implicated in FAK-mediated suppression of anoikis and both the tyrosine kinase PTK6, and the cytokine TGF1, act upstream of FAK and PI3K/Akt to confer anoikisresistance. FAK signaling to PI3K/Akt also protects cells from other types of apoptotic stimuli.  Disruption of fibronectin matrix assembly suppresses FAK tyrosine phosphorylation, and results in delayed G1 to S phase transition. FAK regulates the cell cycle machinery through other signaling pathways in addition to the RAS-Erk pathway.  FAK has long been considered as a potential target for cancer therapeutics, reflecting its pivotal role in governing malignant characteristics and the evidence of high expression and activity in both preclinical cancer models and human cancers.

References

1.Lee BY, et al. Pharmacol Ther. 2015;146:132–149.