PDCD1 and hepatocellular carcinoma: Henceforth, it will be very important to investigate the compensatory immunosuppressive checkpoints of PD-1: PD-L1/L2 pathway on 28ζ CAR T cells in the HCC microenvironment, and the CRISPR-mediated combinatorial disruption of checkpoints will be beneficial for the 28ζ CAR T cells achieving the sustained regression and eradication of HCC.