PD-L1 expression is associated with massive lymphocyte infiltration and histology in gastric cancer.

The mechanism of carcinogenesis of gastric cancer (GC) is still unclear now. This study aimed to explore the correlations among PD-L1, Epstein-Barr virus (EBV) infection, lymphocyte infiltration, HER2 expression, HER2 gene status, histology, and other clinicopathological factors in GC. A total of 44 GC patients with massive lymphocyte infiltration (GC-MLI) and 93 GC patients without massive lymphocyte infiltration were involved in this study. Immunohistochemical analysis was used to test the expression levels of PD-L1 and HER2. Fluorescence in situ hybridization was used on HER2-positive cases with a score of 2+ to test the HER2 gene status. EBV-encoded RNA was used to test for EBV infection. In univariate analysis, PD-L1 expression was significantly associated with GC-MLI (P<.001), lower age (P=.019), EBV infection (P<.001), lower HER2 expression (P=.011), and diffuse/mixed type of histology (P=.022). EBV-encoded RNA-positive cases were significantly associated with GC-MLI (P<.001), lower age (P=.016), diffuse/mixed type of histology (P=.011), and lower HER2 expression (P=.032). In the multivariate logistic regression model, GC-MLI and the diffuse/mixed type histology were identified as 2 independent factors that affected PD-L1 expression (P<.001). Furthermore, PD-L1-positive cases have worse overall survival than do PD-L1-negative cases (P=.011). These results suggest that massive lymphocyte infiltration and the diffuse/mixed type histology of GC should be taken into consideration to select the appropriate patients for PD-L1 inhibitory treatment in the future.