Abstract 4164: Targeting glycogen metabolism as a potential therapy for Ewing sarcoma

Abstract Ewing sarcoma (EWS) is a malignant bone tumor or soft-tissue tumor that mainly affects children, adolescents, and young adults. We recently demonstrated that the PAS+ accumulations in EWS indicate extensive deposits of glycogen, a macro-metabolite that provides an immediate source of glucose to support cellular energy needs. In this study, we sought to elucidate the role of glycogen and its related enzymes in EWS tumorigenesis and metastasis. Though complex carbohydrates like glycogen are traditionally difficult to study due to their biochemical and biophysical properties, the Gentry and Sun laboratories recently developed a robust workflow of matrix-assisted laser desorption/ionization (MALDI)-imaging of complex carbohydrates (MICC), a spatial technique to visualize glycogen in situ. Leveraging this technique, we profiled glycogen accumulation in a cohort of EWS patient tumors. This analysis revealed glycogen levels were dramatically higher in the intra-tumoral regions across all EWS samples. Additionally, through our comprehensive pan-cancer study encompassing 12 different cancer classes, we revealed that glycogen accumulation varies among tumor origins, signifying its unique role in EWS. Lysosomal glycogen degradation is catalyzed by acid α-glucosidase (GAA). Preliminary data from our laboratory demonstrates that glycogen colocalizes with GAA in EWS patient tumors and that small-molecule inhibition of GAA significantly impairs EWS cell proliferation and migration. Transcriptomic analyses revealed a strong correlation between GAA expression and known EWS metastasis regulators, including TGF-β and Wnt/β-catenin signaling pathways. Further experiments revealed that while glycogen synthase 1 inhibitor reduced glycogen levels and impaired EWS cell viability, a small molecule promoting lysosomal glycogen degradation reduced glycogen but paradoxically enhanced cell viability. These findings highlight the critical role of lysosomal glycogen utilization in EWS cell viability, suggesting a potential link between GAA-regulated glycogen degradation, energy homeostasis, and apoptotic pathways in EWS. Moving forward, we are defining the efficacy and mechanism of GAAi in the treatment of EWS preclinical models both as a single agent and in additive therapy with other chemotherapies. To assess the efficacy of GAAi in metastatic EWS, spontaneous lung metastatic mice models will be established by subcutaneous implantation of EWS patient-derived tumor in NSG mice. Our state-of-the art integrated spatial analysis of metabolome, lipidome, and glycome followed by high dimensionality reduction and spatial clustering, annotation, pathway enrichment analysis will provide in-depth spatial insights into tumor and stromal metabolism profile of EWS. Future potential of GAAi study is to conduct clinical trial to identify when and how to add GAAi to current standard care EWS therapy and improve survival outcomes. Citation Format: Yueying Liu, Pankaj K. Singh, Lyndsay E. Young, Harrison A. Clarke, Tara R. Hawkinson, Meagan L. McCall, Elias Sayour, Craig W. Vander Kooi, Li Chen, Ramon C. Sun, Matthew S. Gentry. Targeting glycogen metabolism as a potential therapy for Ewing sarcoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 4164.