PDCD1 and cancer: Immunotherapy has emerged as a transformative approach in the treatment of cancer, particularly through checkpoint inhibitors such as Programmed Cell Death Protein 1 (PD-1) and Cytotoxic T-Lymphocyte Antigen 4 (CTLA-4), which have altered cancer care by utilizing the immune system of the body to target and destroy tumor cells in diverse cancers such as melanoma, lung cancer, bladder cancer, and other types of cancer [164].