PD-L1 expression analysis in gastric carcinoma tissue and blocking of tumor-associated PD-L1 signaling by two functional monoclonal antibodies.

Programmed death-1 ligand-1 (PD-L1), a member of the B7 family of costimulatory molecules, plays an important role in the regulations of the cellular and humoral immune responses. In this study, two mouse anti-human PD-L1 monoclonal antibodies named 10E10 and 2H11 were successfully generated and further characterized. Monoclonal antibody 10E10 bound to distinct PD-L1 epitope comparing an available anti-PD-L1 monoclonal antibody on a series of malignant cell lines, activated T lymphocytes, B lymphocytes and dendritic cells. Then, by using immunohistochemistry staining with monoclonal antibody 2H11, the expression of PD-L1 was found in human gastric carcinoma specimens but not in normal or gastric adenoma tissues. Additional data show that PD-L1 can be regarded as a decisive factor in evaluating gastric carcinoma prognosis and anti-human PD-L1 monoclonal antibody 10E10 could inhibit T-cell apoptosis induced by tumor-associated PD-L1. Taken together, these results showed that the two functional mouse anti-human PD-L1 monoclonal antibodies we generated might be of great value for further exploration of the costimulatory molecule regulating network and immunointervention for tumor immunotherapy.