CXCR2 and neoplasm: MDSCs express several chemokine receptors such as CCR2, CXCR2, CXCR4, and CXCR5, while liver tumor cells or malignant hepatocytes express chemokines such as CCL2, CCL5, CXCL1, CXCL5, and CXCL12, and the chemokine/its receptor axis mediates MDSC infiltration in the tumor microenvironment [55,56,57].