PDCD1 and cancer: Indeed, the recent clinical application of immune checkpoint inhibitors such as anti-programmed cell death protein-1 (PD-1) (Pembrolizumab, Nivolumab) and anti-cytotoxic T-lymphocyte-associated protein-4 (CTLA4) (Ipilimumab) has been quite successful in certain types of cancer such as malignant melanoma, non-small cell lung carcinoma, renal cell carcinoma, and bladder cancer [196,197,198].