CCL2 and neoplasm: Although tumor infiltration by cytotoxic lymphocytes is generally correlated with a favorable outcome (34), substantial evidence has shown that myeloid cells, such as monocytes, DCs, and macrophages, can instead promote tumorigenesis by supplying cytokines (such as CCL2, IGF-1, and EGF) that stimulate tumor proliferation, tissue invasion, and/or angiogenesis (35, 36).