NOS2 and cancer: In particular, myeloid-derived suppressor cells (MDSCs) consisting of precursors of granulocytes, macrophages or dendritic cells that potently inhibit the maturation and function of lymphocytes T, natural killer and dendritic cells were reported to greatly expand in human [11–13] and murine cancer [14], and their activity was linked to increased arginine metabolism by ARG and inducible nitric oxide synthase (iNOS) [15].