Programmed cell death protein 1 expression is an independent prognostic factor in gastric cancer after curative resection

Programmed cell death protein 1 (PD-1) and its ligand PD-L1 downregulate T cell activation and are related to immune tolerance. The aim of this study was to clarify the significance of PD-1 and PD-L1 expression and to analyze the relationships among PD-1, PD-L1, and Foxp3 expression in gastric cancer. A total of 105 patients who underwent curative gastrectomy for stage II/III gastric cancer were included in this study. PD-1, PD-L1, and Foxp3 expression were examined by immunohistochemistry and related to prognostic factors by univariate and multivariate analyses. PD-1 expression was correlated with both PD-L1 and Foxp3 expression. Disease-free survival (DFS) was significantly poorer in PD-1-positive patients than in PD-1-negative patients (3-year DFS, 36.1 % vs. 64.7 %, respectively; p < 0.05). Overall survival also tended to be poorer in PD-L1-positive patients than in PD-L1-negative patients. Univariate analysis identified sex, T factor, lymphatic invasion, and PD-1 positivity as significant predictors of poor DFS. Multivariate analysis confirmed male sex, lymphatic invasion, and positive PD-1 expression as independent prognostic indicators. PD-1 expression is associated with a poor prognosis and is correlated with PD-L1 and Foxp3 expression in patients with gastric cancer.