However, while C-CM (control-conditioned media) tend to induce an M2b polarization of microglia, with production of free oxygen radicals and a significant up-regulation of IL-10 gene expression, CM obtained after glioma stimulation with LI-CM [LPS (lipopolysaccharide)–IFNγ (interferon γ)-conditioned media] induced a significant up-regulation of iNOS (inducible nitric oxide synthase), ARG (arginase) and IL-10 gene expression, indicating the induction of a mixed polarization profile, i.e. both M1 and M2a/b (mixture of polarization phenotypes) phenotypes. This evidence concerns the gene NOS2 and central nervous system cancer.