PDCD1 and hepatocellular carcinoma: Previous studies have indicated that the overexpression of PD-1/PD-L1 in HCC patients is closely related to their poor prognosis and tumor recurrence14,17,34–40; PD-1/PD-L1 expression may serve as a biomarker for predicting ICI treatment response in HCC patients13,33,36,41,42.