Immune checkpoint inhibitors (ICIs) targeting programmed cell death 1/programmed cell death ligand 1 (PD-1/PD-L1) and/or cytotoxic T lymphocyte antigen-4 (CTLA-4) have made impressive breakthroughs in the treatment of multiple cancer types, ranging from non-small cell lung cancer (NSCLC) to various solid malignant tumors (1–3). Here, PDCD1 is linked to cancer.