Programmed cell death protein 1/programmed death ligand 1 (PD1/PD-L1) blockade therapy was found effective in microsatellite instability-high and mismatch repair (MMR)-deficient CRC, a type of CRC exhibiting high somatic mutations; however the type is represented by only 5% of the patient population 13. Here, PDCD1 is linked to colorectal carcinoma.