IDO1 and cancer: Figure 9I shows that cancer-associated fibroblasts (CAF) have the strongest correlation with risk scores. In order to study the potential changes between immune checkpoint expression in high and low risk groups, a total of 47 immune checkpoint-related genes were included, among which CD200, CD244, TNFSF9, CD274, KIR3DL1, PDCD1LG2, CD86, CD28, TIGIT, NRP1, TNFRSF4, CD70, TNFRSF18, HAVCR2, LAIR1, CD80, TNFSF4, CD40, TNFSF18, IDO1, TNFRSF9, CTLA4, LAG3, ICOS, CD276, CD48, and TNFRSF8 were more expressed in high-risk groups than in low-risk groups (Figure 9J).