Abstract C097: Cancer-selective metabolic vulnerabilities in MYC-amplified medulloblastoma

Abstract Background: MYC-amplified group 3 (G3) medulloblastoma (MB) represents a clinically aggressive subgroup of MB that is defined by leptomeningeal metastases, disease recurrence and particularly poor survivorship in comparison to other MB subgroups. There is an urgent need for a more thorough molecular understanding of G3 MB to develop more effective therapeutic modalities that will improve the durability of remission. Methods: We mapped the functional G3 MB metabologenomic landscape via parallel genome-wide CRISPR-Cas9 screening and untargeted liquid chromatography-mass spectrometry (LC-MS) metabolomics. The tractability of potential therapeutic targets was assessed using patient-derived orthotopic preclinical models of G3 MB. Transcriptomics, functional genomics, and metabolomics were employed to discern a mechanism whereby inhibition of DHODH (dihydroorotate dehydrogenase), which is a mitochondrial-bound enzyme that facilitates de novo pyrimidine biosynthesis, selectively impairs G3 MB tumor cell fitness. Results: Untargeted metabolomic profiling shows enrichment of de novo pyrimidine biosynthesis and depletion of salvage pyrimidine intermediates in G3 MB tumor cells in comparison to neural stem cells (NSC), which are the prospective cell-of-origin of MB. In agreement with reprogrammed nucleotide metabolism, DHODH was identified as a corresponding ‘druggable hit’ in the genetic screen. We demonstrate that genetic or pharmacological inhibition of DHODH selectively targets G3 MB brain tumor initiating cells (BTIC) while sparing normal NSC. We further show that MYC-amplified G3 MB tumors harbor subgroup-specific transcriptomic signatures that delineate enrichment of de novo pyrimidine biosynthesis, which sustains c-Myc activity via a metabolite-protein interaction. Significance: Despite clear evidence favoring an altered metabolic landscape in MYC-driven cancers, there have been few reports into the role of metabolic reprogramming in MYC-amplified G3 MB. This metabolic vulnerability is hence not exclusive to MB and has recently been identified in other primary brain malignancies; current efforts are focused on establishing relevant biomarkers that will facilitate clinical translation. Citation Format: Sheila Singh, William Gwynne, Yujin Suk, Jeremy Chan, Andrew Qualie, Laura Escudero, Kevin Brown, Chitra Venugopal, Jason Moffat, Rafael Montenegro-Burke. Cancer-selective metabolic vulnerabilities in MYC-amplified medulloblastoma [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 C097.