GFPT1 facilitates immune escape in breast cancer by promoting the OGT-mediate O-GlcNAcylation of CD39

Breast cancer (BC) remains a major cause of cancer-related mortality among women worldwide, with immune escape being a critical mechanism contributing to tumor progression and therapy resistance. Glutamine-fructose-6-phosphate transaminase 1 (GFPT1) has been implicated in cancer metabolism, yet its role in tumor immunity remains poorly understood. This study aimed to investigate whether GFPT1 promotes immune evasion in BC and to elucidate the underlying molecular mechanisms. A Transwell-based co-culture system with pre-activated human PBMCs was used to model immune‒tumor interactions. Flow cytometry was used to assess T cell subsets, and quantitative real-time PCR evaluated exhaustion markers. LDH release and cytokine levels were measured to evaluate cytotoxicity. Molecular interactions were examined through immunoprecipitation (IP), Co-IP, immunofluorescence, and Western blot. The results showed that GFPT1 was significantly overexpressed in BC tissues and cell lines, correlating with poor patient survival. Knockdown of GFPT1 enhanced CD8⁺ T-cell infiltration, cytotoxic activity, and pro-inflammatory cytokine release, while reducing the expression of exhaustion markers. GFPT1 physically interacted with OGT and regulated its expression. Mechanically, OGT mediated the O-GlcNAcylation of CD39 at Ser239, increasing its stability. CD39 overexpression rescued the immune-inhibitory phenotype after OGT knockdown. In vivo, GFPT1 silencing suppressed tumor growth. Overall, this study displayed the promoting effect of GFPT1 on the immune escape of BC, which provides new therapeutic targets for the immunotherapy of BC.