Serafini et al. showed that sildenafil increased cGMP, reduced IL-4Rα expression and down-regulated ArgI and NOS2 enzymatic activity of tumor infiltrating MDSCs thereby reduced the immunosuppression of G1+/CD11+ myeloid cells with improving the efficacy of adoptive T-cell therapy in tumor bearing mice [169] (Table 3). The gene discussed is NOS2; the disease is neoplasm.