LOXL4 and hepatocellular carcinoma: At present, studies on the tumor-promoting mechanism of LOXL2 mainly focus on its extracellular effect: LOXL4 can be transferred between cells by HCC-derived exosomes, which can not only activate the FAK/SRC pathway in a H2O2-dependent manner to promote the migration of HCC cells, but also can be transferred to VECs to promote angiogenesis [94].