NOS2 and neoplasm: At the same time, IL-2 and IFN-γ levels were increased in mouse tumor sera, and the infiltration and function of CD8+ T cells were promoted [84], It has been demonstrated that interferon (IFN) promotes the increase of Treg cells and MDSCs in TME and is detrimental to the therapeutic effectiveness of PD-1 by inducing nitric oxide synthase 2 (NOS2) expression [33].