This confirmed that PD-1 expression on immune cell infiltrates in the TIL and stromal compartment and the invasive front compartment differed significantly between the dMMR and pMMR CRC groups (p=0.001 for both), as did the PD-L1 expression percentage on immune cell infiltrates (p=0.036) and IDO expression (p=0.014). This evidence concerns the gene IDO1 and colorectal carcinoma.