The risk score was significantly and positively associated with the expression levels of CD274 (r = 0.38; P = 4.9e-14), CTLA-4 (r = 0.22; P = 3.1e-05), HAVCR2 (r = 0.33; P = 5.1e− 11), IDO1 (r = 0.16; P = 0.0028), PDCD1 (r = 0.19; P = 0.00027), and PDCD1LG2 (r = 0.28; P = 4e− 8; Fig. 6B-G), suggesting that risk score may act as a key driving factor in immunotherapeutic prediction of HCC. Here, IDO1 is linked to hepatocellular carcinoma.