PDCD1 and malignant colon neoplasm: However, neither PD-1/L1 nor CTLA-4 has yet been confirmed to have relevant efficacy in unselected colon cancer, and only the subgroups of deficient mismatch repair (dMMR) or microsatellite instable high (MSI-H) tumors of colon cancer are amenable to checkpoint inhibition [7, 8].