NOS2 and cancer: Sangaletti et al. reported that cancer metastasis was significantly suppressed in SPP1-deficient mice, and cancer-derived SPP1 was related to the immunosuppressive function of MDSCs via regulating immune-related molecules such as arginase 1, nitric oxide synthase 2 (NOS2), vascular endothelial growth factor (VEGF), and IL-6 [87].