NOS2 and neoplasm: In the presence of lactate, the anti-tumor function of M1 macrophages is inhibited by reducing the expression of IL-6 (interleukin 6), IL–1 (interleukin 1), iNOS (inducible nitric oxide synthase), and TNF (tumor necrosis factor) [72, 74], while inactivated macrophages undergo an induced polarization process changing their phenotypes, that results in the formation of pro-tumor M2 macrophages [75, 76].