Targeting Glycogen Metabolism in Ewing's Sarcoma: Diagnostic, Prognostic, and Therapeutic Applications

Abstract: Ewing’s Sarcoma (ES) is the second most common pediatric bone cancer. Intensified chemotherapy regimens have only incrementally improved recurrent or metastatic ES outcomes, motivating research and development of new treatment options to combat this deadly disease. The accumulation of large glycogen granules,

clinically known as Periodic acid-Schiff (PAS) positive, is a clinical hallmark of ES. However, the origin and pathology of ES-glycogen remains a critical knowledge gap and it has not been pursued as a therapeutic target. Recent reports, including our own, reveal critical roles for complex carbohydrates such as glycogen and

N-linked glycans in tumor progression. We developed a robust and highly sensitive workflow called MALDI imaging of complex carbohydrates (MICC) in situ with near single cell spatial resolution. Using this workflow, we interrogated complex carbohydrates in over 1000 tumor specimens from prostate, lung, colon, and ES

patients. Our data demonstrate that: 1) high glycogen is a unique clinical hallmark of ES; 2) three independent strategies (i.e., CRISPR knockout, small molecule inhibition, and genetic re-expression) led to dramatic reduction of ES glycogen and resulted in blunted ES tumor growth in vivo in athymic mouse models; 3) a

glycogen synthase inhibitor synergized with metformin at improving AMPK activity and preventing tumorigenesis. Collectively, these results provide strong evidence to support our hypothesis that glycogen is a unique and clinically actionable hallmark of ES that can be leveraged in the clinic for both diagnostic and

therapeutic interventions. The objective of this study is to define the role of glycogen in ES clinical outcomes, cancer metabolism, and leverage glycogen targeting strategies as therapeutic options for ES. To achieve this, we will: Define diagnostic and predictive potentials of glycogen in ES clinical course. (Aim 1). Then, we will

Define spatio-cellular roles of ES glycogen utilization to support cancer growth. (Aim 2). Finally, we will assess Glycogen as an ES therapeutic target. (Aim3). Our study presents a pioneering, integrated approach to explore the distinct ES hallmark of excessive glycogen using powerful methodologies like mass spectrometry imaging

and unique clinical cohorts of ES tumors. This proposal builds on the foundation of exciting preliminary data and our transdisciplinary team's expertise to define the ES clinical course, understand ES tumor metabolism, and improve treatment of documented disease. Our findings will substantially enrich the knowledge base,

spurring the development of personalized therapies for ES patients who currently rely solely on conventional chemotherapies. Our goal is to improving patient care outcomes and provide better treatment options for children suffering from ES.