PDCD1 and neoplasm: The accumulation of depolarised mitochondria in anti-tumour T-cells contributes to exhaustion whilst supplementation with nicotinamide riboside reduced the accumulation of depolarized mitochondria in T-cells via Drp-1-dependent mitophagy, improving T-cell mitochondrial fitness and responses to anti-PD-1 ICB in OVA melanoma-engrafted mice by [202].