PDCD1 and liver cancer: For example, a variety of therapeutic antibodies blocked the immune checkpoints, such as programmed cell death protein 1 (PD1) and cytotoxic T lymphocyte-associated antigen 4 (CTLA4), which have demonstrated superior performance in the treatment of many tumors such as glioma, liver cancer, and non-small-cell lung cancer (Johnston and Khakoo 2019; Xu et al. 2020).