NOS2 and neoplasm: They impair the functions of Teff and NK cells through mechanisms involving substances such as arginase 1, inducible nitric oxide synthase (iNOS), reactive oxygen species (ROS), and peroxynitrite.100 Furthermore, MDSCs influence the maturation of Tregs and drive macrophages toward a suppressive phenotype, contributing to tumor angiogenesis, invasion, and metastasis.101 Clinical data indicate a correlation between MDSCs presence and poorer cancer outcomes, including diminished responses to immunotherapies.102