IDO1 and malignant colon neoplasm: As shown in Fig. 7A-C and Additional file 4: Figure S3H-N, as opposed to the low-risk colon cancer patients, the high-risk cases showed higher expressions of CTLA-4 (p < 0.001), PD-1 (p < 0.01), PD-L1 (p < 0.001), IDO1 (p < 0.05), IDO2 (p < 0.05), HAVCR2 (p < 0.001), and LAG3 (p < 0.05).