CCL2 and neoplasm: During tumour progression, TAMs may be more inclined to the M2 polarized state [18] and can secrete various growth factors such as VEGF, PDGF, EGF, chemokines and cytokines such as IL-10, TGF-β, CCL2 and CXCL12 [19]; thus, the tissue trophic function of M2-type TAMs instead promotes tumour progression [20].