Abstract 766: Spatial evaluation of tumor sialylation of N-linked glycans in prostate cancer tissues

Abstract Aberrant sialylation is a common feature of prostate cancer. Sialylation is part of the co-translational glycosylation machinery, where sialic acids are enzymatically added to glycoproteins as a quality control mechanism to ensure proper protein folding and stability. However, in solid tumors like prostate cancer, this process becomes dysregulated, resulting in hypersialylation. Tumor cells exploit this alteration to mask their identity, evade immune detection, and promote aggressive tumor growth. In humans, α2,3 and α2,6 isomers of N-acetylneuraminic acid are the most abundant species detected in sialylated N-glycans. The presence of α2,6 sialylated glycans is a well-established marker for PCa aggressiveness, while α2,3 sialylation is a known feature of sialyl Lewis x/a tumor antigens. Distinguishing between these isomers is crucial due to their distinct chemical and biological properties, which can offer deeper insights into disease pathology, thus we used N-glycan mass spectrometry imaging to preserve histology and spatial distribution of both sialic acid isomeric species. In this study, we evaluated N-linked sialylated glycans in a large cohort of 381 primary prostatectomy samples in tissue microarray format. A double amidation chemical treatment to differentially add mass tags specific to each isomer was done, followed by matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI). This platform enabled high-resolution spatial analysis of α2,3 and α2,6 sialylated N-glycan isomers in each tumor core. Initial data grouping compared the intensities of 80 sialylated N-glycan isomers across Gleason scores G6 (n = 134), G7[3+4] (n = 181), and G7[4+3] (n = 66). Significant differences in the levels of specific N-glycans were determined between these groups, including upregulation of α2,3-linked tetra-antennary fucosylated glycans, downregulation of bi-antennary α2,3- and α2,6-linked species, and fluctuations in tri- and tetra-antennary glycans of both isomers, suggesting glycan remodeling with tumor advancement. Additional clinical data assessments are ongoing to evaluate sialylation differences associated with tumor stage, race, BMI, age, and other parameters. The combination of double amidation isomer tagging and MALDI-MSI provides a promising advancement in the differentiation and characterization of previously difficult-to-identify sialic acid isomers, enhancing potential applications in prostate cancer diagnostics. Citation Format: Kameisha Rashford, Caroline Kittrell, Bettina F. Drake, Ariana Ahmed, Aleksandra Klim, Eric Kim, Peggi Angel, Joseph E. Ippolito, Richard Drake. Spatial evaluation of tumor sialylation of N-linked glycans in prostate cancer tissues [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 766.