Increased PD‐1 expression on CD4+ and CD8+ T cells is involved in immune evasion in gastric cancer

BACKGROUND: Co-signaling molecules play an important role in T cells. Programmed death-1 (PD-1) is an immunoinhibitory receptor and its overexpression on T cells appears to be involved in immune evasion in cancer patients. The present study was designed to investigate PD-1 expression on T cells and its relationship with immune evasion in gastric cancer patients. METHODS: PD-1 expression on CD4+ and CD8+ T cells obtained from peripheral blood mononuclear cells (PBMC), normal gastric mucosa, and gastric cancer tissue was evaluated by multicolor flow cytometry. RESULTS: PD-1 expression on CD4+ and CD8+ T cells from gastric cancer patients was significantly higher than that from normal controls. PD-1 expression on CD4+ and CD8+ T cells was related to disease progression. Furthermore, PD-1 expression on CD4+ and CD8+ T cells from gastric cancer tissue was significantly higher than that from normal gastric mucosa and PBMC. PD-1 positive CD4+ and CD8+ T cells produced significantly less IFN-gamma than PD-1 negative CD4+ and CD8+ T cells. CONCLUSIONS: Upregulation of PD-1 on both CD4+ and CD8+ T cells may be, in part, responsible for immune evasion in gastric cancer patients.