Abstract 3719: Fasting-mimicking diet plus 2-DG drives antitumor immunity by targeting EDEM3-induced PD-L1 glycosylation

Abstract The PD-1/PD-L1 axis plays an essential role in immune escape and immunotherapy. Importantly, translated N-linked glycosylation of PD-L1 stabilizes protein, enters the cell membrane binding to PD-1, renders T cells anergic and leads to T-cell exhaustion and dysfunction. Targeting PD-L1 glycosylation as an attractive target by a rational combination of cancer immunotherapies. Cancer-associated fibroblasts (CAFs), a predominant cell component of the tumor microenvironment, exert crucial functions in promoting immune escape and immunotherapy resistance by increasing the tumor PD-L1 expression. However, whether and how CAFs upregulate the glycosylation of PD-L1 has never been reported. This study shows that CAFs can upregulate PD-L1 glycosylation and enhance PD-L1 cell surface expression via glycosyltransferase EDEM3, thus cancer immune evasion. Then, the study delves into the relationship between EDEM3 expression, prognosis and immunogenicity. We demonstrate that EDEM3 plays a role in tumor immunity during tumor progression, as evidenced by EDEM3 expression is only significantly correlated with poor prognosis in the CD8+ T cell-enriched population. In subcutaneous tumor models, we observed high cell-surface PD-L1 expression accompanied by decreased CD8+ T cell infiltration and increased M2 macrophage in immunocompetent mice transplanted with EDEM3 over-expressed CRC cells that promote resistance to PD-1/PD-L1 blockade cancer immunotherapy. By performing bioinformatic analysis, we found that the hexosamine biosynthesis pathway (HBP) is highly affected in EDEM3-upregulated CRC cancer. Subsequently, the production of the UDP-GlcNAc (the end product of HBP metabolic flow), a donor substrate for N-linked glycosylation, is significantly increased in EDEM3 over-expressed CRC cells by LC/MS. Meanwhile, glucose is confirmed to be the primary effector of PD-L1 glycosylation in CRC cells, and the glucose restriction attenuates EDEM3-modified PD-L1 glycosylation by reducing UDP-GlcNAc biosynthesis. Finally, we demonstrate that modulation of glucose metabolism through a fasting-mimicking diet (FMD) in combination with 2-deoxy glucose (2-DG) treatment enhances antitumor immunity, especially in tumors with high-EDEM3 expression that exhibit resistance to immunotherapy. We propose potential therapeutic targets for CRC that inhibit PD-L1 glycosylation through FMD+2-DG and could augment the efficacy of immune checkpoint blockers. Citation Format: Xiaoxia Liu, Shaoyong Peng, Xiaolin Wang, Huichuan Yu, Yanxin Luo. Fasting-mimicking diet plus 2-DG drives antitumor immunity by targeting EDEM3-induced PD-L1 glycosylation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3719.