Abstract B076: Targeting cancer glycomes sensitizes ovarian tumors to immunotherapy

Abstract Aberrant glycans on tumor cell surface contribute to immune escape. The purpose of this study is to establish novel immunotherapeutic strategies for HGSOC tumors by targeting glycans-mediated immune escape in high-grade serous ovarian cancer (HGSOC). Here, we performed in vivo screens targeting 96 glycan structures among a series of mouse HGSOC tumors with different genotypes. We identified β1, 6-GlcNAc branched N-glycan as a major determinant of immune escape in a homologous recombination (HR) -proficiency dependent manner in HGSOCs. Mechanistically, BRCA1/2 transcriptionally suppresses the expression of MGAT5 that produces β1, 6-GlcNAc branched glycans. Using in vitro T cell killing assay, we observed that removal of β1, 6-GlcNAc branched glycans by a small molecule inhibitor or genetically knocking down MGAT5, sensitizes HR-proficient human HGSOC cells to T cells assault. Consistently, using orthotopic syngeneic mouse models, we observed that inhibition of β1, 6-GlcNAc branched glycans sensitizes and synergizes with anti-PD-L1 in HR-proficient, but not HR-deficient HGSOCs. In summary, we identified β1, 6-GlcNAc branched N-glycan as a key mediator of immune escape in HR-proficient HGSOCs. Our findings indicate that MGAT5 represents a therapeutic target to overcome immune escape in a HR-status dependent manner and inhibition of β1, 6-GlcNAc branched glycans sensitizes HR-proficient HGSOCs to immune checkpoint blockades. Citation Format: Hao Nie, Pratima Saini, Heng Liu, Wei Zhou, Chen Wang, Daniel Claiborne, Nan Zhang, Mohamed Abdel-Mohsen, Rugang Zhang. Targeting cancer glycomes sensitizes ovarian tumors to immunotherapy abstract. In: Proceedings of the AACR Special Conference on Ovarian Cancer; 2023 Oct 5-7; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84 (5 Suppl₂): Abstract nr B076.