NOS2 and neoplasm: In this particular model system the combination of radiation with PD-1 and CTLA-4 inhibition only minimally altered the immunologically cold tumor microenvironment, but the addition of cyclophosphamide and the iNOS inhibitor shifted the balance of infiltrated immune cells away from immunosuppressive types (such as MDSCs) to those more associated with anti-tumor immunity (such as dendritic cells and anti-tumor M1 macrophages).