Compared to MSS tumors, the tumor microenvironment of dMMR/MSI-H CRC shows a significant upregulation of immune checkpoints like PD-L1, CTLA-4, LAG-3, and IDO, which generate tumor-associated immunogenic antigens (Le et al., 2015; Toh et al., 2016). The gene discussed is IDO1; the disease is colorectal carcinoma.