PDCD1 and colorectal carcinoma: Great emphasis has thus been placed on developing immunotherapies for CRC treatment4,5, particularly after the Food and Drug Administration’s approval of the cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) antibody ipilimumab in 20116, the programmed cell death protein 1 (PD-1) antibodies pembrolizumab and nivolumab in 20147, and the PD-1 ligand (PD-L1) antibody atezolizumab in 20158.