Abstract 2819: Mass spectrometry imaging reveals heterogeneous glycogen metabolism in non small cell lung cancer
Authors: Conroy Lindsey R. , Young Lyndsay EA , Clarke Harrison A. , Stanback Alexandra E. , Buoncristiani Michael D. , Brainson Christine F. , Allison Derek B. , Sun Ramon C. , Drake Richard R. 
Published: July 2021

Lung cancer is the leading cause of cancer related death worldwide, with a high mortality rate even when diagnosed at an early stage. Identifying the unique molecular features that drive disease progression within distinct tumor subtypes is a critical step in lung cancer research that could advance our understanding of lung cancer biology, leading to predictive biomarkers and novel therapies. Glycogen is the primary source of carbohydrate storage in most issues, and its degradation products are intimately connection to central carbon metabolism. Recently, aberrant glycogen accumulation has been observed in lung tumors and been reported to promote lung cancer progression. Despite these findings, the full clinical implications of dysregulated glycogen metabolism and its role in lung cancer tumorigenesis remain largely unknown. Due to its unique physiochemical properties, glycogen is extremely difficult to measure biochemically and visualize in situ. Herein, we describe a novel method to image microenvironmental glycogen via enzymatic release of glycogen substrates coupled to matrix-assisted laser desorption ionization-mass spectrometry imaging (MALDI-MSI). Our assay provides robust information on glycogen structure and phosphate composition with spatial distribution. With this technique, we analyzed glycogen chain length and glycogen phosphate content from tissue microarrays containing over 200 lung cancer patient samples banked at the University of Kentucky with over 10 years of clinical metadata. Using MALDI-MSI, we found significant glycogen accumulation in lung tumor tissue compared to match normal lung across all patients, and found adenocarcinoma (LUAD) samples contained higher glycogen content than squamous cell carcinoma (SCC). Regional analysis by MALDI-MSI revealed SCC primarily accumulates glycogen in the stroma and blood vessels, but not in tumors. Notably, LUAD patient tumors exhibit decreased expression of laforin, a glucan phosphatase that plays a key role in glycogen phosphorylation and glycogen degradation. Low laforin expression also corresponds to poorer overall survival in LUAD patients. In vivo, deletion of Epm2a (the gene that encodes laforin) in KRASG12D/p53-/- mice results in increased tumor burden and accumulation of hyperphosphorylated intratumoral glycogen. Further, A549 LUAD xenografts treated with guaiacol, a glycogen synthase inhibitor, show markedly reduced tumor growth, while guaiacol had no effect on H2030 SCC tumor growth. Given the significant effect of glycogen accumulation on in vivo tumor growth, our data suggest the glycogen metabolic pathway represents a novel therapeutic target specifically for LUAD patients. Together, our study describes a novel method to visualize glycogen structure using MALDI-MSI and reveals unique metabolic features that contribute to LUAD disease progression.

Citation Format: Lindsey R. Conroy, Lyndsay EA Young, Harrison A. Clarke, Alexandra E. Stanback, Michael D. Buoncristiani, Christine F. Brainson, Derek B. Allison, Ramon C. Sun, Richard R. Drake. Mass spectrometry imaging reveals heterogeneous glycogen metabolism in non small cell lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2819.