TDO2 and cancer: Based on Pearson correlation analysis, cell abundance was screened to be significantly correlated with immune checkpoint expression levels, and the results showed that the abundance of B cells, cancer-associated fibroblasts (CAFs), endothelial cells, and plasmocytes were significantly correlated with immune checkpoints TDO2 (p = .043), PDCD1 (p = .017), LGALS9 (p = .017), and PVR (p = .026), respectively (Figure 2B).