Targeting UDP-GlcNAc–mediated O-GlcNAcylation in regulatory T cells attenuates immunotherapy resistance in esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) exhibits heterogeneous responses to immunotherapy, partly driven by metabolic alterations within the tumor microenvironment. Integrative untargeted metabolomic and single-cell transcriptomic analyses of tumors from patients receiving neoadjuvant anti–PD-1 therapy identified UDP-GlcNAc as a metabolite enriched in non-responders and strongly associated with poor outcomes. UDP-GlcNAc enhanced O-GlcNAcylation in regulatory T (Treg) cells, promoting their expansion and suppressive function. Mechanistically, O-GlcNAcylation stabilized the deubiquitinase EIF3H, which in turn deubiquitinated and stabilized lactotransferrin (LTF), reducing intracellular iron levels and conferring ferroptosis resistance in Tregs. Single-cell RNA sequencing revealed GFPT1 upregulation in Tregs from non-responders, while metabolic-flux tracing confirmed that GFPT1-driven glutamine metabolism fuels UDP-GlcNAc accumulation. Functional assays and in-vivo therapeutic models demonstrated that pharmacologic inhibition of this metabolic–O-GlcNAc axis decreased Treg infiltration, restored antitumor immunity, and enhanced PD-1 blockade efficacy. Collectively, these findings delineate a metabolic–post-translational modification axis linking glutamine metabolism to Treg ferroptosis resistance through UDP-GlcNAc–mediated O-GlcNAcylation of EIF3H, and highlight this pathway as a promising target to overcome immunotherapy resistance in ESCC.