NOS2 and glioblastoma: In intracranial U87 xenografts, immunostaining revealed that bevacizumab-resistant glioblastoma showed an increased amount of TAMs and increased M2/M1 ratio, defined by M2 markers (Arg-1, TGF-β, MMP9) and M1 markers (NOS2, CXCL10, IL-1β), compared to bevacizumab-sensitive glioblastoma [232].