NOS2 and cancer: It has been shown that MDSCs mediate their effect on T lymphocytes in cancer through direct contact and/or through a combination of multiple major mediators such as inducible nitric oxide synthase (iNOS), arginase-1 (Arg1), reactive oxygen species (ROS), transforming growth factor-β (TGF-β), IL-10, regulatory T-cells (Treg), and macrophages [38].