PDCD1 and cancer: In recent years, ICB has brought about significant advancements, reshaping the treatment landscape for various cancers, including non-small cell lung cancer (NSCLC), melanoma, and breast cancer, in which immune checkpoint inhibitors (ICIs) targeting the programmed cell death protein 1 (PD-1) and its ligand (PD-L1), either as monotherapies or in combination, have become the standard regimen.