PDCD1 and hepatocellular carcinoma: PD-1 is a common immunosuppressive factor on the surface of T cells, PD-L1 is overexpressed on the surface of malignant tumor cells and binds to PD-1 to inhibit T cell proliferation and activation, making T cells inactivated and eventually inducing immune escape, resulting in treatment failure (5).PD-1/PD-L1-based pathways play an important role in cancer immunotherapy, and their inhibitors have made breakthroughs in treatment, bringing hope to HCC patients (6–8).