Second, ‘ONOO− scavengers combined with immune checkpoint inhibition’ (e.g., anti-PD-1) address RNS-driven immunosuppression: preclinical studies in melanoma models demonstrated that FeTPPS (a selective ONOO− scavenger) reduced Treg infiltration by 35% and enhanced CD8+ T cell cytotoxicity, synergizing with anti-PD-1 to shrink tumors by 60% – a effect attributed to diminished ONOO−-mediated PD-L1 upregulation on tumor cells [203]. Here, CD274 is linked to neoplasm.