CCL2 and cancer: Inflammatory monocytes are rapidly recruited to sites of inflammation, including cancer, by chemokines such as macrophage-colony stimulating factor 1 (CSF-1), C-C motif chemokine ligand 2 (CCL2), and stromal cell-derived factor 1 alpha (SDF-1α), where they extravasate from the blood vessels and differentiate into monocyte-derived macrophages [16–18].