This result is consistent with the results that CAR-T cell therapy containing the synthetic PD-1/CD28 switch molecule can prevent the inhibition of T-cell activity due to the binding of PD-1 and PD-L1 and activate T-cell proliferation and differentiation by CD28; therefore, it has the advantage of increasing the complete remission rate for solid cancers, such as pancreatic and liver cancers, more effectively than conventional CAR-T cell therapy (Guo & Cui, 2020). Here, PDCD1 is linked to liver cancer.