CCL2 and neoplasm: CCL2 were highly expressed in metastatic CRC liver tumors compared with normal liver tissue, and CCL2 mediated bone marrow-derived circulating CCR2 + IM (CD11b + , CD14 + , CCR2 +) migration to the site of liver metastasis in CRC patients, where they differentiated into immunosuppressive TAMs (CD115 + , CD14 + , CD68 +) and supported metastatic tumor growth.