PTK2 and hepatocellular carcinoma: It is believed that CD63 can mediate the TGF-β signaling pathway through binding of inhibitors of metalloproteinase-1 (TIMP-1), a key mediator of TGF-β-mediated crosstalk between hepatic stellate cells (HSCs) and HCC cells, activate the FAK-Akt signaling pathway in HCC cells, and further favor migration and survival of HCC cells (31).