Regulation of de novo nucleotide synthesis and Glioblastoma response to radiochemotherapy

Cancer cells are highly dependent on the de novo synthesis of nucleotides to maintain sufficient pools to support DNA/RNA metabolism and cell proliferation. The dysregulation of the de novo nucleotide biosynthetic pathway contributes to the development of many human diseases, such as cancer. Many enzymes in this pathway are overactivated in different cancers. The phosphoribosyl pyrophosphate synthetase (PRPS1/2) enzymes are critical regulators of de novo nucleotide biosynthetic pathway. PRPS1/2 generate a critical precursor necessary for producing all nucleotide species and function as a `molecular throttle' capable of increasing or decreasing the rate at which these genetic building blocks are made. PRPS1/2 is linked to different cancer types, but the underlying mechanism is not fully understood. Our preliminary work revealed that PRPS1, but not PRPS2, is phosphorylated at tyrosine residue Y146 by fibroblast growth factor receptor 1 (FGFR1) and epidermal growth factor receptor (EGFR) in glioblastoma (GBM) cancer cells. This phosphorylation event primed PRPS1 for S-palmitoylation by ZDHHC3. S-palmitoylation constitutes a reversible lipid post-translational modification widely present in cells. Palmitoylation boosted PRPS1 enzyme activity and de novo nucleotide synthesis, and induced tumor development. Of therapeutic significance, depletion of ZDHHC3 sensitizes GBM to radiation and TMZ, indicating that ZDHHC3 could serve as a novel potential therapeutic target for GBM. Based on these preliminary findings, we hypothesize that ZDHHC3 governs de novo nucleotide synthesis by palmitoylating and boosting PRPS1 funcions and that targeting this pathway sensitizes cancer cells to raidochemotherapy. To test this novel hypothesis and further our goal, we will examine how ZDHHC3-PRPS1 axis promotes de novo nucleotide synthesis (Aim 1), explore the molecular mechanisms by which FGFR1 and EGFR signal modulates PRPS1 palmitoylation (Aim 2), and investigate an important role of PRPS1 palmitoylation in promoting resistance to radiochemotherapy in vivo (Aim 3). Our studies will reveal a previously unappreciated role of palmitoylation in de novo nucleotide synthesis pathway, and point to a novel mechanism for radiochemotherapy resistance. Built upon multidisciplinary expertise, compelling scientific premises, and rigorous research strategy, our studies promise to have a significant impact on the development of the next generation of safer, more targeted therapies and rational approaches for ameliorating cancers associated with perturbed nucleotide homeostasis. Project Number: 1R01CA301624-01A1 | Fiscal Year: 2026 | NIH Institute/Center: National Cancer Institute (NCI) | Principal Investigator: Huadong Pei (+1 co-PI) | Institution: GEORGETOWN UNIVERSITY, WASHINGTON, DC | Award Amount: $656,469 | Activity Code: R01 | Study Section: Biochemical and Cellular Oncogenesis Study Section[BCO] View on NIH RePORTER: https://reporter.nih.gov/project-details/11296018