PDCD1 and neoplasm: As discussed above, the TCGA identified EBV-positive tumors as a distinct GC subgroup.19 Among other features, these tumors are characterized by rich lymphocytic infiltrates, containing CD8-positive cytotoxic T cells and high number of mature dendritic cells, and are enriched in immune cell signaling pathways.49,66 Furthermore, about 15% of EBV-positive GCs have amplification of the PD-L1- and PD-L2-encoding genes, and have PD-L1 expression in both tumor cells and immune cells.19,50,67 These features suggest that EBV-positive GC may be more susceptible to PD-1/PD-L1 blockade.