In recent years, application of immune checkpoint inhibitors (ICIs), especially programmed cell death protein 1 (PD-1), programmed cell death ligand 1 (PD-L1), and cytotoxic T lymphocyte antigen 4 (CTLA-4) monoclonal antibodies against immune regulatory checkpoints on immune and tumor cells, represents a major breakthrough in the treatment of many solid tumors, such as HCC (6, 7). Here, PDCD1 is linked to neoplasm.