In recent years, immune checkpoint inhibitors (ICIs), such as anti-cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) inhibitors and anti-programmed death 1 (PD-1)/programmed death-ligand 1 (PD-L1) inhibitors, in combination with chemotherapy and immunotherapy have made significant progress in multiple types of cancers (2). Here, PDCD1 is linked to cancer.