QPRT (quinolinate phosphoribosyltransferase) is a rate-limiting enzyme in de novo NAD+ biosynthesis from tryptophan, catalyzing the conversion of quinolinate to nicotinic acid mononucleotide. Beyond its canonical metabolic role, QPRT has emerged as a critical regulator in multiple disease contexts. In acute kidney injury, QPRT activity defends renal NAD+ levels; QPRT heterozygous mice exhibit impaired NAD+ and elevated susceptibility to AKI, and oral nicotinamide supplementation—which bypasses QPRT—was associated with reduced AKI in critically ill patients 1. In triple-negative breast cancer, LAT1-mediated L-tryptophan uptake upregulates QPRT to amplify NAD+ synthesis and promote glycolytic reprogramming; LAT1 inhibition with JPH203 synergistically enhanced doxorubicin efficacy in resistant cells 2. In liver cancer, chr16 stress suppresses hepatic QPRT expression via β2-adrenergic signaling disruption, diverting kynurenine metabolism toward kynurenic acid accumulation and impairing CD8+ T cell immunity; nicotinamide administration recovered immune function and reduced cancer progression 3. High QPRT expression in breast cancer correlates with worse overall survival, distant metastasis-free survival, and recurrence-free survival and predicts benefit from taxane or anthracycline therapy 4. In leukemic cells, WT1 directly transcriptional activates QPRT, conferring partial imatinib resistance through NAD+-independent anti-apoptotic mechanisms 5. These findings position QPRT as a metabolic checkpoint integrating energy homeostasis with immune surveillance and chemoresistance.