The effects of TNF‐α/TNFR2 in regulatory T cells on the microenvironment and progression of gastric cancer

TNFR2(+) regulatory T cells preferentially accumulate in the tumor microenvironment, express high levels of immunosuppressive molecules and possess strong suppressive activity. Our study aimed to explore the characteristics and role of TNFR2(+) Tregs in the microenvironment and progression of gastric cancer via polychromatic immunofluorescence, single‐cell RNA sequencing and flow cytometry assays. The TNFR2(+) Treg infiltration level in the tumor microenvironment increased significantly as gastric cancer progressed and was demonstrated to be a prognostic marker. Single‐cell RNA sequencing revealed high levels of TNFR2 in tumor‐infiltrating Tregs. The TNF‐α/TNFR2 signaling pathway was activated, accompanied by the upregulation of costimulatory molecules. Unlike blood Tregs, tumor‐infiltrating Tregs existed in activated and effector states. In addition to expressing costimulatory molecules such as TNFR2, 4‐1BB, OX40 and GITR, tumor‐infiltrating Tregs were also characterized by high expression levels of immune checkpoints such as CTLA‐4 and TIGIT and chemokines such as CCR6. In vitro studies showed that the TNF‐α/TNFR2 pathway increased the Foxp3 expression in CD4(+)CD25(+) T cells and the latent TGF‐β production in Tregs as well as enhanced the immunosuppressive function of Tregs. In summary, our study revealed high infiltration levels of TNFR2(+) Tregs that were in activated and effector states in the tumor microenvironment. The infiltration level of TNFR2(+) Tregs is a prognostic marker and an independent risk factor for gastric cancer. Activation of the TNF‐α/TNFR2 pathway promotes the immunosuppressive phenotype and function of Tregs. Our study provides a new theoretical basis for TNFR2(+) Tregs as a therapeutic target in gastric cancer.