PDCD1 and hepatocellular carcinoma: In addition, we examined the differential expression of immune checkpoints in HCC and normal tissues with a total of eight immune checkpoints (including SIGLEC15, HAVCR2, CD274, PDCD1LG2, PDCD1, LAG3, CTLA4, and TIGIT) and the results displayed that all immune checkpoints, except HAVCR2 and PDCD1, were differential expressed in HCC and normal tissues (Figure 5B).