Activation of Toll-like receptor 2 enhances peripheral and tumor-infiltrating CD8+ T cell cytotoxicity in patients with gastric cancer.

BACKGROUND Toll-like receptors (TLRs) play central roles in the initiation of innate immune response, and also control adaptive immunity activation. Thus, the aim of the study was to investigate the regulation of TLR activation to CD8+ T cells has not been fully elucidated in gastric cancer (GC). MATERIALS AND METHODS Thirty-two GC patients and twenty-three healthy controls were enrolled. Expression profile of TLRs in peripheral and tumor-infiltrating CD8+ T cells was investigated. Purified CD8+ T cells were stimulated with Pam3Csk4, an agonist of TLR2, and cytotoxic and co-inhibitory molecules in CD8+ T cells was measured. Direct and indirect contact coculture system between CD8+ T cells and AGS cells was set up. Modulation of TLR2 activation to CD8+ T cells was assessed by measuring lactate dehydrogenase release and cytokine secretion. RESULTS TLR2 mRNA and TLR2+ cell percentage was down-regulated in GC derived peripheral and tumor-infiltrating CD8+ T cells. CD8+ T cells from GC patients showed exhausted phenotype, which presented as decreased perforin/granzyme B, increased programmed death-1, and reduced cytotoxicity to AGS cells. TLR2 activation by Pam3Csk4 enhanced perforin and granzyme B expression in CD8+ T cells, however, did not affect either proinflammatory cytokine production or co-inhibitory molecules expression. Pam3Csk4 stimulation enhanced cytolytic activation of peripheral and tumor-infiltrating CD8+ T cells from GC, but not those from healthy individuals. CONCLUSION The present data revealed an important immunomodulatory activity of TLR2 to CD8+ T cells in GC patients.