PTGDR and esophageal squamous cell carcinoma: We found that methylation level of ZEB1‐AS1 promoter in ESCC tissues and cells was significantly lower than that in normal tissues and cells (P < .0001), and meanwhile, a negative correlation between methylation level of ZEB1‐AS1 promoter and ZEB1‐AS1 expression was found, which is consistent with previous investigation in hepatocellular carcinoma.28 These data imply that ZEB1‐AS1 at high level may be tightly associated with ZEB1‐AS1 promoter hypomethylation.