Abstract B108: NUDT5 inhibition differentially affects IDH1-Wildtype and Mutant high-grade glioma to induce NAD+ independent radiosensitization and anti-proliferative effects
Authors: Cox Thomas J.R , Ozcagli Eren , Schettino Giuseppe , Meira Lisiane B 
Published: December 2023

Abstract
Adult-type diffuse gliomas are aggressive brain cancers. The widespread standard treatment for these high-grade gliomas (HGG) is the Stupp Protocol, consisting of maximal safe surgical resection followed by concurrent chemoradiotherapy. However, since the Stupp Protocol, no significant therapeutic advances have been as widely and easily adopted, halting improvements in HGG patient survival. Therefore, identifying new drug targets or treatments that enhance the Stupp Protocol would result in therapeutic benefit. HGG are classified by distinct genetic and metabolic alterations; the most well-known being somatic gain of function mutations in isocitrate dehydrogenase (IDH) 1/2 genes. These mutations distinguish the two most severe HGGs, namely Grade 4 IDH-Mutant Astrocytoma and IDH-Wildtype Glioblastoma (GBM). IDH-mutant tumors accumulate the oncometabolite D-2-Hydroxyglutarate, which alters metabolic pathways and DNA damage responses. One metabolic alteration is decreased nicotinamide adenine dinucleotide (NAD+) levels, a metabolite essential for cellular homeostasis, and crucial in IDH-mutants as targeting NAD+ homeostasis is effective against IDH-mutant tumors. Here, we investigated if additional metabolic vulnerabilities within NAD+ and purine biosynthetic pathways could be identified in HGG cells. For this, a panel of cell lines, including an isogenic IDH1-mutant cell line, was screened for their sensitivity to a range of metabolic inhibitors in combination or not with chemo- and radiotherapy. This screen identified NUDT5, a Nudix hydrolase that metabolizes ADP-Ribose into Ribose-5-Phosphate (R-5-P) to replenish NAD+ pools, and synthesizes nuclear ATP for hormone driven chromatin remodeling, as an important determinant in glioma cell survival. Cell viability assays determined NUDT5 inhibition (NUDT5i) sensitized IDH1-wildtype HGG cells to different radiotherapy modalities, specifically X-rays and alpha particles, whilst IDH1-mutant HGG were sensitive to NUDT5i alone. Live-cell imaging analysis indicated NUDT5i induced cytostasis followed by cytotoxicity in the IDH1-mutant, suggesting IDH1-mutations confer exploitable metabolic dependencies on NUDT5 for proliferation and survival. NUDT5i did not significantly deplete NAD+ levels and NAD+ precursor supplementation failed to rescue cell survival and proliferation, indicating effects of NUDT5i are NAD+ independent. Our results indicate NUDT5 plays a crucial role in HGG proliferation and survival. Given that NUDT5 produces R-5-P for downstream nucleotide synthesis, we hypothesize that NUDT5i impairs nucleotide homeostasis and leads to replication stress. Current investigations include nucleoside supplementation and characterization of replication stress signaling by western blotting. We anticipate our results to prelude further investigations into NUDT5 as a potential therapeutic target in HGG. We suggest NUDT5i could enhance the effectiveness of the Stupp Protocol regardless of IDH-Status and advance HGG therapies.
Citation Format: Thomas J.R Cox, Eren Ozcagli, Giuseppe Schettino, Lisiane B Meira. NUDT5 inhibition differentially affects IDH1-Wildtype and Mutant high-grade glioma to induce NAD+ independent radiosensitization and anti-proliferative effects [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr B108.