Tumor-derived EBI3 promotes CD8+ T cell exhaustion via STAT4-IL-10/CCL5 in gastric cancer.

Combination chemotherapy and immunotherapy are effective against advanced gastric cancer (GC). However, T cell exhaustion in the tumor microenvironment may decrease the immune response and compromise the effectiveness of immunotherapy. Herein, we report the potential role of EBI3 in promoting T cell exhaustion and its mechanism in GC, showing high expression of EBI3 in GC. Correlation analysis between EBI3 expression level and clinical-pathological features indicated significant associations with Tumor stage, Nodal staging, pathologic stage, and degree of tumor differentiation. EBI3 expression levels correlated with a state of high CD8+ T cell exhaustion, as identified by transcriptome sequencing and mice orthotopic GC models. On exposure to EBI3, CD8+ T cells showed signs of cell exhaustion as reduced cytokine secretion and increased expression of inhibitory receptors in vitro/vivo studies. Mechanistically, EBI3 induced T cell exhaustion by promoting phosphorylation of STAT4, upregulating the transcription of downstream target genes CCL5 and IL-10. An anti-EBI3 heptapeptide (Val-Tyr-Leu-His-Trp-His-Asp) was developed, which competitively bound EBI3 and reversed the induction of T cell exhaustion. Taken together, we identified a T cell exhaustion mechanism in GC via the EBI3-STAT4-IL10/CCL5 axis and developed an anti-EBI3 heptapeptide with an antagonistic function. These findings provide a potential immunotherapeutic target and support the development of EBI3-based interventions to enhance immunotherapy efficacy in GC.