Profiles of PD-1, PD-L1, PD-L2 in Gastric Cancer and Their Relation with Mutation, Immune Infiltration, and Survival

Background. Although multiple types of cancers demonstrated favorable outcome after immunotherapy of PD-1/PD-L1 blockade, the specific regulatory mechanism of PD genes in gastric cancer (GC) remains largely unknown. Materials and Methods. Expression of RNA, copy number variants, and clinical parameters of GC individuals from TCGA were analyzed. Coexpressed genes for PD-1, PD-L1, and PD-L2 were selected by correlation analysis and confirmed by STRING. Gene Ontology and KEGG pathway analyses were performed by clusterProfiler. The influence of PD-1/PD-L1/PD-L2 on immune cell infiltration was investigated by MCP-counter. Results. PD-L2 demonstrated significant relation with clinical stage of GC (P=0.043). Survival analysis showed that PD-1 expression was correlated with better prognosis of GC patients (HR=0.70, P=0.031), but PD-L2 expression was related with worse survival (HR=1.42, P=0.032). Mutation of PIK3CA could alter the level of PD-1, PD-L1, and PD-L2 (P