Abstract 174: Multimodal mass spectrometry imaging of immune cell glycosylation across three immunosuppressive tumor microenvironments

Abstract Glycosylation is essential for the development, trafficking, and activation of the immune system. The complex interaction between the immune system and tumor cells within the tumor microenvironment is crucial to understand cancer progression and improve therapeutic interventions. Immunotherapy is an emerging tool in cancer treatment, showing promise across various malignancies, however; its effectiveness in solid tumors remains limited and inconsistent. Colorectal carcinoma (CRC) has demonstrated enhanced sensitivity to immunotherapy, particularly in cases with high microsatellite instability or mismatch repair deficiency. In contrast, the immune cold prostate (PCa) and pancreatic ductal adenocarcinoma (PDAC) cancers are typically less responsive to immunotherapy due to an immunosuppressive tumor microenvironment. Emerging evidence for the role of N-glycosylation modulating activity in the tumor microenvironment suggests it could be an indicator of response to immunotherapy. We aimed to establish spatial profiles of immune cells surrounding and within tumor tissues of CRC, PCa, and PDAC using Matrix-Assisted Laser Desorption-Ionization Mass Spectrometry Imaging (MALDI-MSI) for N-glycomic profiling and MALDI-immunohistochemistry to identify the cellular compositions of the tumor microenvironment. Utilizing 73 tissue samples collected from patients with varying stages of CRC, PCa, and PDAC, our lab has characterized the N-linked glycan profile of over 250 immune cell clusters within and surrounding these tumors. Using an established photocleavable-mass tagged antibody panel (CD20, CD3, CD8, CD44, CD11b, CD68) we broadly characterized the immune microenvironment. In CRC, we identified immune clusters of CD20+ B cells and CD3/CD44+ T cells distinctive and predictive with signature profiles of bisecting and branched N-glycans. In PCa and PDAC, we identified a similar cellular makeup for the immune clusters as seen in CRC; however, high mannose and core fucosylated N-glycans were more prevalent within and surrounding these tumors. Additionally, N-glycan signatures varied depending on spatial proximity to the tumor in PCa and PDAC tissues. Our innovative, two dimensional approach provides critical insights into the cellular composition and metabolic complexity of the tumor microenvironment. Importantly, establishing a cellular and metabolic profile of the tumor immune microenvironment may offer valuable indicators of immunotherapy effectiveness, paving the way for improved personalized medicine. Citation Format: Lyndsay E. Young, Caroline G. Kittrell, Kameisha Rashford, Grace Grimsley, David N. Lewin, Anand S. Mehta, Peggi M. Angel, Kristin Wallace, Richard R. Drake. Multimodal mass spectrometry imaging of immune cell glycosylation across three immunosuppressive tumor microenvironments [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 174.