CCL2 and hepatocellular carcinoma: Specific cytokines released by HCC, such as interleukin-4 (IL-4), interleukin-13 (IL-13), colony stimulating factor 1 (CSF-1), CCL2, C-X-C motif chemokine ligand 12 (CXCL12), and connective tissue growth factor (CTGF), are known to induce TAMs derived from other sources [21].