Clinical Significance of Tumor and Immune Cell PD-L1 Expression in Gastric Adenocarcinoma

Background/Aim: The prognostic relevance of programmed cell death ligand-1 (PD-L1) protein expression in gastric cancer (GC) remains controversial. The aims of the present study were to determine the correlations between tumor cell (TC) and immune cell (IC) PD-L1 protein levels with prognosis, and to determine the correlation between PD-L1 expression and different molecular GC subtypes. Materials and Methods: TC and IC PD-L1 protein levels were measured in 286 GC patients. The patients were classified according to the Cancer Genome Atlas and Asian Cancer Research Group guidelines using immunohistochemistry and in situ hybridization. Results: TC and IC PD-L1 protein levels were positively correlated with patient survival. TC PD-L1 expression was negatively correlated with tumor grade. TC and IC PD-L1 expression was associated with improved prognosis in Epstein-Barr virus negative (EBV-), microsatellite instability (MSI) rather than microsatellite stability (MSS) subgroup GC patients. Conclusion: PD-L1 protein expression in TCs and ICs can be used as a prognostic indicator for GC patients, particularly in the EBV-, MSI, and MSS subgroups.