Targeting the NAD⁺ Salvage Pathway Blocks Metabolic Recovery and Enhances β-Lapachone Toxicity in NQO1-Expressing Glioblastoma Cells

Glioblastoma (GBM) is a highly heterogeneous tumor, with some cell NAD⁺ and evade β-lap toxicity. We identified the NAD⁺ salvage pathway to populations overexpressing genes that give them a survival advantage. be the primary pathway responsible for maintaining NAD⁺ levels in GBM. One such gene is NAD(P)H quinone oxidoreductase 1 (NQO1), which We demonstrate that targeting this pathway with the nicotinamide phosprotects cells from oxidative stress. Although NQO1 overexpression shields phoribosyltransferase (NAMPT) inhibitor FK866 prevents NAD⁺ cells from endogenous oxidants, the enzyme can also bioactivate certain regeneration after β-lap exposure and enhances β-lap cytotoxicity in compounds, including the naphthoquinone β-lapachone (β-lap). This acti- NQO1-expressing GBM. Altered NAD⁺ metabolism in GBM reprevation triggers repeated cycles of oxidative stress that ultimately drive cell sents a potential metabolic vulnerability. Our results suggest that death. In this study, we investigated whether NQO1 overexpression could be targeting NQO1-expressing GBM with NQO1-bioactivatable com-exploited as a selective vulnerability to induce toxicity in GBM cells. pounds in combination with NAMPT inhibitors is a promising NQO1 expression status in the U87 GBM cell line, multiple patient-derived therapeutic strategy for the treatment of GBM. GBM cell lines, and normal human astrocytes (NHA) was evaluated. Dose–response studies, NAD⁺ quantification, and immunoblot analysis were uti- Significance: NAD⁺ metabolism is altered in GBM. However, there are lized to evaluate the link between NAD⁺ synthesis and β-lap toxicity. We limited therapeutic options for targeting this metabolic vulnerability. demonstrate that NQO1 is highly expressed in multiple GBM cell lines and This study identifies NQO1+ GBM as highly susceptible to β-lap–β-lap induces selective cytotoxicity in these cells while sparing low NQO1- induced NAD⁺ depletion and cell death. Blocking the NAD⁺ salvage expressing cells including NHAs. β-lap induces acute NAD⁺ depletion and pathway prevents metabolic recovery in GBM and increases β-lap toxDNA damage. However, high NQO1-expressing GBM cells may regenerate icity in NQO1+ cells.