CCL2 and neoplasm: TAM, which are derived from circulating CD14+/CD16+ monocytes, are recruited into the TME by a wide range of chemokines, including monocyte chemoattractant protein (MCP)-1/CCL2, C-X-C motif chemokine ligand (CXCL)1, CXCL10, and stromal-derived factor (SDF)-1/CXCL12, secreted by tumor cells or other stromal cells [112,113] (Figure 1).