Tumor immunotherapies have provided clinical benefits, yet great potential remains for optimizing therapeutic effects. Here, we show that low NAD + levels restrict the function of 20 tumor infiltrating T lymphocytes (TILs). TILs harvested from human ovarian tumor tissues showed decreased NAD + levels compared with T cells from paired peripheral blood samples.The combination of whole-genome CRISPR and large-scale metabolic inhibitor screens implicated the NAD + biosynthesis enzyme nicotinamide phosphoribosyltransferase (NAMPT) is required for T cell activation. Further isotopic labeling and LC-MS studies confirmed that NAD + 25 depletion suppressed mitochondrial energy biosynthesis in T cells. Excitingly, NAD + supplementation significantly enhanced the tumor cell-killing efficacy of CAR-T cells ex vivo, and extended animal survive in both adoptive CAR-T model and immune checkpoint blockade treatment models in vivo. This study demonstrates an over-the-counter nutrient supplement NAD + could robustly boost the efficacy of T cell-based immunotherapy and provides insights 30 into the cellular basis of T cell metabolic reprogramming in treating cancers.
One Sentence Summary:NAD + supplementation during cancer immunotherapies significantly enhances T cell activation and tumor killing capacity.Main Text: 35 Cancer immunotherapies including adoptive transfer of naturally-occurring tumor infiltrating lymphocytes (TIL) and genetically-engineered T cells, as well as the use of immune checkpoint inhibitors to boost the function of T cells have emerged as promising approaches to achieve durable clinical responses of otherwise treatment-refractory cancers 1-5 . Although cancer immunotherapies have been successfully utilized in the clinic for subsets of patients, there are 40 several limitations which prevent the broad use of these therapies for entire patient populations 6,7 . Given the function of T cells as key mediators for tumor destruction, their characteristics (e.g., durability, longevity, and killing efficiency, etc.) substantially determine the clinical outcomes of many immunotherapies [8][9][10][11] . Studies have established that successful clearance of tumors mediated by infiltrated T cells can be limited by physical barriers generated by stroma 45 3 cells 12 , immuno-suppressive networks 13 , and nutrient limitations within the microenvironment 14,15 . Thus, efforts to promote the stemness, proliferation and activation capacity of T cells should enable improvements to the efficacy of cancer immunotherapies.Recently, cellular metabolic processes have been reported to shape T cell differentiation and functional activity [16][17][18] . Modulation of metabolic process such as fatty acid catabolism can 50 improve T cell activation and therapeutic function [19][20][21][22][23][24] . It was also reported that there is a strong link between metabolic activity in tumor infiltrated T cells (TIL) and their effector function 25,26 , and stimulation mitochondrial biogenesis via enforced expression of PGC1α resulted in...