['Cigarette smoke extracts (CSE) could promote esophageal squamous cell carcinoma (ESCC) through upregulation of cyclooxygenase-2 (COX-2) expression. Promoter methylation mediates the transcriptional modulation of the COX-2 gene. The aim of the study was to explore whether COX-2 promoter methylation regulated COX-2 expression and functional activity in ESCC exposed to CSE.', 'The methylation status of COX-2 promoter in two human ESCC cell lines, EC109 and TE-1, was examined using bisulfite sequencing analysis. COX-2 mRNA and protein expression were detected by reverse-transcription polymerase chain reaction and Western blot. Prostaglandin E₂ (PGE₂) was examined by enzyme linked immunosorbent assay (ELISA).', "The promoter was hypermethylated in TE-1 which had a low level of COX-2 expression and was hypomethylated in EC109 with a relatively high level of COX-2 expression. Stimulation by cigarette smoke ethanol extract (EE) resulted in increased COX-2 expression in EC109, but not in TE-1. Treatment with 5-aza-2'-deoxycytidine (5-aza-DC) demethylated the promoter and upregulated COX-2 expression as well as PGE(2) production in TE-1, especially followed by EE stimulation. No significant effect was observed in EC109."] Does promoter methylation regulate cigarette smoke-stimulated cyclooxygenase-2 expression in esophageal squamous cell carcinoma?