In colorectal cancer, VGEF-A secreted by colorectal cancer cells can stimulate TAMs to produce chemokine (C-X-C motif) ligand 1 (CXCL1) in the primary tumor, and CXCL1 recruits chemokine (C-X-C motif) receptor-2 (CXCR2)-positive MDSCs into liver tissue to form a pre-metastatic niche and promote liver metastasis of colon cancer (Wang et al. 2017a). Here, CXCR2 is linked to colorectal cancer.