IDO1 and esophageal cancer: Zhou et al. (2020) revealed that IDO1 and PD-L1 expression and CD8 density increased significantly after neoadjuvant chemoradiation therapy in ESCC, and could serve as prognostic biomarkers for survival. IDO1 promoter hypomethylation was found to regulate its mRNA upregulation in esophageal cancer (Kiyozumi et al., 2019b). Mechanically, IDO1 facilitated esophageal carcinoma progression by driving the direct binding of NF-κB and CXCL10 (Yao et al., 2023).