NOS2 and neoplasm: Classically activated (M1) MΦ are induced in response to IFN-γ and lipopolysaccharides and they are characterized by the production of high levels of pro-inflammatory cytokines including tumor necrosis factor-α (TNF-α), interleukin IL-1, IL-6, IL-12, IL-23 and inducible nitric oxide synthase (iNOS), which play a crucial role in their anti-tumor activity.