Relationship of programmed death 1 (PD-1) expression to the recurrence in gastric cancer

31 Background: PD-1 (Programmed Death 1), a member of the B7-CD28 family, is a cell surface coinhibitory receptor expressed on T cells, B cells, monocytes, and natural killer T cells, following activation. Recently, PD-1 expression is involved with malignancy have been reported in cancer cells and virus-infected cells. The aim of this study is to clarify the impact of PD-1 expression on long term outcome of gastric cancer. Methods: Total of 105 patients who were performed gastrectomy in Stage 2/3 gastric cancer. For resected specimen was performed immunostaining of PD-1. We counted PD-1 positive T cells in the tumor across five adjoining high power fields (×400 magnification level). And, we calculated the percentage of the total cell number, it was considered PD-1 positive more than 40%. We investigated clinicopathological factors and survival. Results: 28 cases were PD-1 positive expression. There was no significant difference between the two groups in the clinicopathological factors (age, gender, tumor size, differentiation, depth of invasion, lymph node metastasis, stage, lymphatic invasion and venous invasion). There was no difference in overall survival rate at 3 years (PD-1 positive vs. negative 76% vs. 81%, p=0.552). PD-1 positive expression was significantly poorer in disease-free survival rate (36% vs. 65%, p=0.022). 10 cases were Foxp3 positive expression, and Foxp3 positive expression was related with PD-1 expression. Conclusions: The PD-1 expression in the tumor could be a potential prognostic factor in gastric cancer.