NOS2 and ovarian cancer: Similarly, in ovarian cancer, elevated levels of C5a impact the levels of immunoregulators in the TME, such as arginase, inducible nitric oxide synthase (iNOS), vascular endothelial growth factor (VEGF), and tumor necrosis factor alpha (TNF-α), thereby reducing the infiltration of CD4+ and CD8+ T cells and promoting tumor growth (36).