PDCD1 and cancer: While anti-CTLA-4 and anti-PD-1/PD-L1 immune checkpoint blockade has shown varying success in cancers, including melanoma, non-small cell lung carcinoma (NSCLC), and urothelial carcinoma, many show low or no response, including gastrointestinal, breast, pancreatic, prostate, sarcoma, and colorectal cancers [39,40,41,42,43,44,45,46,47].