ChIP‐qPCR assays indicated that H3K4me3 levels were enriched in the PD‐L1 promoter region at approximately −1000 to 0 bp and in the IDO‐1 promoter region at approximately −1500 to −500 bp in ESCC cells (Figure 4B,C and Figure S4B,C). This evidence concerns the gene IDO1 and esophageal squamous cell carcinoma.