PDCD1 and hepatocellular carcinoma: Generally, “hot” tumors respond more favorably to ICIs due to their pre-existing immune activity and augmented expression of immune checkpoint molecules, such as PD-1 and PD-L1 (Ortega et al., 2024).For instance, Zhou et al. found that DSF/Cu can upregulate PD-L1 expression in hepatocellular carcinoma cells by inhibiting PARP1 and enhancing GSK3β phosphorylation at Ser9 point, and combination therapy with DSF/Cu and an anti-PD-1 antibody showed much better antitumor efficacy than monotherapy (Zhou et al., 2019).