Comprehensive Characterization Of Pdl-1 And Ctla-4 In Gastric Cancer.

4056 Background: Recently remarkable efficacy of immune checkpoint inhibition has been reported for several kinds of solid cancers. This study is the first comprehensive analysis of cytotoxic T lymphocyte antigen 4 (CTLA-4) and programmed death 1 ligand 1 (PD-L1) in gastric cancer and the first study integrating oncogenomic analyses. Methods: PD-L1 and CTLA-4 were stained on paraffin embedded tumor sections of 127 patients with gastric cancer by immunohistochemistry. Genetic driver mutations were identified by next-generation Sequencing and FISH analysis. Expression of PD-1, PD-L1 and CTLA-4 on lymphocytes in tumor sections, lymph nodes and peripheral blood were studied by 10-colour flow cytometry and 4-colour immune-fluorescence microscopy in an additional cohort. Results: PD-L1 and CTLA-4 were expressed on primary tumor cells by 44.9%(57/127) and 86.6%(110/127) of the analyzed gastric cancer samples, respectively. Correlation to clinical and pathological parameters revealed no correlation for PD-L1, whe...