By in vitro experiments carried out in human and murine tumor cell models, i.e. U373 and Gl261 glioma cells, that do not natively express NOSs, and culturing these cells with macrophages derived from the bone marrow of wt and iNOS−/− mice, we observed that the presence in tumor milieu of M2-like macrophages expressing iNOS renders tumor cells resistant to CDDP by protecting them from apoptosis. This evidence concerns the gene NOS2 and neoplasm.