MDSCs, characterized as granulocytic/polymorphonuclear (G/PMN-MDSCs) or monocytic (M-MDSCs) based on their cell lineage of origin, further suppress the anti-tumor immune response through multiple mechanisms including the production of arginase-1, reactive oxygen species, TGF-β, and IL-10 [59]. The gene discussed is ARG1; the disease is neoplasm.