Interestingly, PD-1 (gene symbol, PDCD1) and PD-L2 (gene symbol, PDCD1LG2), but not PD-L1 (gene symbol, CD274), are included in this global immune gene signature, likely because PD-L1 was expressed in intraepithelial immune cells, but not in tumor cells [17]. Here, PDCD1 is linked to neoplasm.