PDCD1 and melanoma: For instance, immune checkpoint inhibitors (ICIs) targeting programmed cell death protein 1 and its ligand (PD-1/PD-L1), as well as cytotoxic T lymphocyte-associated protein 4 (CTLA-4), have demonstrated substantial clinical benefits in malignancies such as melanoma and non-small cell lung cancer (NSCLC), significantly improving overall survival (9).