M1 macrophages express inducible nitric oxide synthase (iNOS) and produce nitric oxide (NO), IL-12, IL-23, tumor necrosis factor (TNF), IL-1β and IL-6, whereas anti-inflammatory M2 tumor-associated macrophages (TAMs) secrete immunosuppressive cytokines and express arginase-1, which promotes the depletion of extracellular arginine and leads to the metabolic suppression of tumor-infiltrating T cells (65, 69, 71). The gene discussed is ARG1; the disease is neoplasm.