PDCD1 and hepatocellular carcinoma: Interestingly, the frequency of CD8+ TRM cells and PD-1 expression on the CD8+ TRM cells were different between HBV-related HCC and non-viral HCC [32], suggesting that the etiology of HCC might have an impact on the generation or survival of CD8+ TRM cells in HCC and thereby can affect the T cell immunity in HCC and the clinical outcome, especially receiving ICI treatment.