CD8A and neoplasm: In terms of immunometabolism, NAMPT (nicotinamide phosphoribosyltransferase) in NAD+ (nicotinamide adenine dinucleotide) metabolism increases PD-L1 expression in tumor cells through the Stat1-dependent IFN-γ signaling pathway, inducing CD8+ T cell exhaustion, thus resulting in tumor immune escape and poor prognosis for patients [126].