NAD+ supplement potentiates tumor-killing function by rescuing defective TUB-mediated NAMPT transcription in tumor-infiltrated T cells

Although tumor-infiltrating lymphocytes (TILs) maintain their ability to proliferate, persist, and eradicate tumors, they are frequently dysfunctional in situ. By performing both whole-genome CRISPR and metabolic inhibitor screens, we identify that nicotinamide phosphoribosyltransferase (NAMPT) is required for T cell activation. NAMPT is low in TILs, and its expression is controlled by the transcriptional factor Tubby (TUB), whose activity depends on the T cell receptor-phospholipase C gamma (TCR-PLCγ) signaling axis. The intracellular level of NAD⁺, whose synthesis is dependent on the NAMPT-mediated salvage pathway, is also decreased in TILs. Liquid chromatography-mass spectrometry (LC-MS) and isotopic labeling studies confirm that NAD⁺ depletion led to suppressed glycolysis, disrupted mitochondrial function, and dampened ATP synthesis. Excitingly, both adoptive CAR-T and anti-PD1 immune checkpoint blockade mouse models demonstrate that NAD⁺ supplementation enhanced the tumor-killing efficacy of T cells. Collectively, this study reveals that an impaired TCR-TUB-NAMPT-NAD⁺ axis leads to T cell dysfunction in the tumor microenvironment, and an over-the-counter nutrient supplement of NAD⁺ could boost T-cell-based immunotherapy.