Programmed cell death ligand 1 (PD-L1) expression on gastric cancer and its relationship with clinicopathologic factors.

Background: Targeting the immune checkpoints in solid tumors becomes hot recently. Programmed cell death ligand 1 (PD-L1) is ligand for programmed death 1 (PD-1), which is known to negatively regulate T-cell activation. In the present study, we investigated the expression of PD-L1 in tumor specimens of gastric cancer and its relationships with clinicopathological variables and survival. Methods: The expression of PD-L1 in 132 surgically resected specimens of stage II and III gastric cancer was evaluated by immunohistochemistry in microarray tissue. Results: Expression of PD-L1 was observed in 50.8% (67/132) of gastric cancer tumor specimens. Patients whose tumor size over 5cm had a higher positive rate of PD-L1 expression. There was no relationship between the expression of PD-L1 and other clinicopathological variables including age, gender, clinical stage, location as well as histological differentiation. PD-L1 positive patients had significantly poorer survival than negative patients. The 5-year survival rates was 83.1% in those with PD-L1 negative patients and 50.7% for PD-L1 positive patients (P<0.001). The multivariate analysis indicated that both PD-L1 positive and Tumor-node-metastasis stage were independent prognostic factors in gastric cancer patients (P=0.001 and 0.025, respectively). Conclusions: The expression of PD-L1 was found in half of stages II and III gastric cancer patients. Positive of PD-L1 expression indicated poor survival in Chinese stages II and III gastric adenocarcinoma patients. These results may provide the clue for immunotherapy in the adjuvant treatment setting of gastric cancer patients.