CXCR4 and hepatocellular carcinoma: AFP can also promote HCC cell invasion and metastasis through upregulating the expression of matrix metalloproteinase (MMP) 2/9 (Figure 1), epithelial cell adhesion molecule (EpCAM), and C-X-C chemokine receptor type 4 (CXCR4), and AFP knockout significantly inhibits the migration and invasion abilities of HCC cells (26–28).