Proinflammatory follicular helper T cells promote immunoglobulin G secretion, suppress regulatory B cell development, and correlate with worse clinical outcomes in gastric cancer.

Gastric cancer is one of the most common and aggressive malignancies. Both bacterial virulence factors and host chronic inflammation are thought to promote gastric cancer development. In this study, we investigated the potential involvement of follicular helper T cells in gastric cancer. Functions of follicular helper T subsets were examined in Helicobacter pylori-infected gastric cancer patients and H. pylori-infected but asymptomatic individuals. We found that the follicular helper T cells in gastric cancer individuals were skewed toward the Th1 and Th17 subsets compared to those in H. pylori-infected but asymptomatic individuals. In a naive B cell-follicular helper T cell coculture, the Th1-follicular helper T cells by themselves were ineffective at stimulating a robust antibody response, unlike the Th2-follicular helper T and Th17-follicular helper T cells. However, Th1-follicular helper T cells significantly promoted the immunoglobulin G response in collaboration with other follicular helper T subsets, through the secretion of interferon gamma. We also found that Th1-follicular helper T cells suppressed the development of interleukin-10+ regulatory B cells, a cell type previously thought to protect H. pylori-infected individuals from tissue damage. In addition, the frequency of Th1-follicular helper T cells in gastric cancer patients was negatively correlated with the disease-free survival of gastric cancer patients after tumor resection. These results suggested that dysregulation of follicular helper T subsets in gastric cancer patients, characterized by increased Th1-follicular helper T cells, contributed to inflammation and tumor development.

Preferential Tim-3 expression on Treg and CD8(+) T cells, supported by tumor-associated macrophages, is associated with worse prognosis in gastric cancer.

While infection with H. pylori is a strong risk factor for gastric cancer, most H. pylori-colonized individuals, even those with the high-risk CagA(+)VacA(+) strain, remain asymptomatic over their lifetime. We hypothesized that the discordant outcomes were due to differences in the host immune responses. Previously, Tim-3-mediated immune modulation was observed in H. pylori-challenged mice. In this study, we compared Tim-3-related responses in CagA(+)VacA(+) H. pylori-infected asymptomatic individuals and H. pylori-associated gastric adenocarcinoma patients. We showed that compared to H. pylori-uninfected individuals, both H. pylori-infected asymptomatic and gastric cancer patients upregulated Tim-3 overall. However, the Tim-3 upregulation was enriched on Th1 cells in asymptomatic patients and on Treg and CD8(+) T cells in gastric cancer patients, with respective differences in T cell subset functions. In gastric cancer patients, high Tim-3 expression on Treg and CD8(+) T cells, but not on Th1 cells, was associated with worse prognosis. H. pylori-antigen presentation by tumor-associated macrophages upregulated Tim-3 expression more effectively than by blood monocyte-derived macrophages in vitro. The upregulation of Tim-3 in vitro depended on the concentration of H. pylori antigen but not on whether the cells were from asymptomatic or cancer patients. These data suggest that the discrepancy in Tim-3 upregulation in asymptomatic and cancer subjects is induced by cancer but not the other way around. Once gastric cancer is developed, Tim-3 expression is associated with worse prognosis.