Expression patterns of programmed death-1 and programmed death-1 ligand-1 on T cells in gastric cancer.

The aim of the present study was to evaluate programmed death-1 (PD-1) and programmed death-1 ligand-1 (PD-L1) expression in gastric carcinoma and to assess their effect on survival rate. A total of 170 surgically resected specimens were obtained from patients diagnosed with gastric carcinoma at St. Vincents Hospital, The Catholic University of Korea. Paraffin tissue sections from tissue microarray blocks were subjected to immunohistochemical analysis of PD-1 and PD-L1. In addition, PD-1 expression on CD4(+) and CD8(+) T cells isolated from peripheral blood mononuclear cells and gastric cancer tissues was evaluated by multicolor flow cytometry. PD-1 and PD-L1 were expressed in 30.0 and 60.5% of the gastric cancer tissues, respectively. The expression of PD-L1 was higher in patients with advanced T (P=0.035) and Tumor, Node and Metastasis stage (P=0.05). The patients with positive PD-L1 expression had shorter disease-free survival time than those without PD-L1 expression (P=0.005). Additionally, PD-L1 expression was significantly associated with poor prognosis (P=0.015). PD-1 and PD-L1 expression levels were significantly higher on CD8(+) T cells than on CD4(+) T cells (P<0.001). The data of the present study suggested that PD-L1 expression may be an independent indicator of poor prognosis in patients with gastric cancer. Furthermore, PD-L1 expression may play a role in immune evasion of gastric cancer.