PDCD1 and hepatocellular carcinoma: Studies demonstrated higher levels of PD-1 [22,24,30,37,47,71], TIGIT [22], CTLA-4 [20,37,71], TIM-3 [30,37], LAG-3 [22], and TOX [22,30] in HBV-associated HCC compared with non-HBV HCC.