PDCD1 and neoplasm: mtROS production stimulates IFN γ-dependent reprogramming in CD8+TILs.Reduces tumor-infiltrating Treg (TiTreg)Inhibits G-MDSCsActivates the Hippo signaling pathway to regulate PD-L1Increases CD8+ T cell infiltration and survival in hypoxic tumor regionsT cell metabolic reprogrammingCombination with PD-1 blockers improves intra-tumoral T cell function and tumor clearance.