PDCD1 and hepatocellular carcinoma: In addition, the immune microenvironment of HCC provides a suitable growth environment for tumor development (13), and chimeric antigen receptor (CAR) T-cell therapies and monoclonal antibodies against programmed cell death protein 1 (PD-1), thus improving the prognosis of patients with HCC by altering the pathways where immune cell checkpoints are located and thus improve the prognosis of patients with HCC (14).