NOS2 and neoplasm: M1 macrophages exhibit an anti-tumor and pro-inflammatory phenotype, and can release pro-inflammatory cytokines, such as tumor necrosis factor-α (TNF-α), C-C motif chemokine ligand 2 (CCL2), IL-6, inducible nitric oxide synthase (iNOS), IL-1α, IL-1β, IL-12, IL-23, IL-18, type I IFN (-α and -β), C-X-C motif chemokine ligand 1–3 (CXCL1–3), CXCL5, and CXCL8–10.