Nevertheless, our results were supported by previous studies which demonstrated that some B7 family molecules such as PD-L1 (64, 65), PD-L2 (66), PD-1 (67), B7-H2 (68), B7-H3 (69) and IDO (70) play a significant functional role in modulating anti-HCC immunity. Here, IDO1 is linked to hepatocellular carcinoma.