PTK2 and hepatocellular carcinoma: In conclusion, to our knowledge, we showed for the first time that LOXL4 can be transferred between HCC cells with different expression levels of LOXL4 via exosomes and that intracellular LOXL4 promotes HCC motility and metastasis by activating the FAK/Src pathway dependent on its amine oxidase activity through a hydrogen peroxide-mediated mechanism; in addition, exosomes derived from HCC cells can transfer LOXL4 to HUVECs to promote angiogenesis via maintaining cell survival, promoting cell migration, and inducing tube formation (Fig. 9).