YAP1 and cancer: In cancer cells, transmembrane cell surface growth factor receptors and downstream intracellular signaling pathways, including EGFR, PDGFR, PI3K/Akt/mTOR, and RhoA, have been reported to mainly activate YAP mediated by Src kinase through three mechanisms: (1) direct phosphorylation; (2) the activation of pathways repressing Hippo kinases; and (3) Hippo-independent mechanisms [128,129,130,131,132,133,134,135].