MSI-H or mismatch repair-deficient (dMMR) colorectal cancer is characterized by high expression of PD-L1 (programmed death ligand-1) and is therefore amenable to treatment with anti-PD-1 (programmed cell death protein-1)/PD-L1 checkpoint inhibitors, a type of immunomodulatory therapy [21]. Here, PDCD1 is linked to colorectal cancer.