Abstract: Objective To determine the relationship between cyclooxygenase-2(COX-2) expression and its promoter methylation status in lower expressed COX-2 esophageal squamous cell carcinoma(ESCC), as well as to investigate the significance of combining demethylating agent with selective COX-2 inhibitor in depression of ESCC. Methods ESCC cell line TE-1 was used in this study, and 5-aza-deoxycytidine(50-aza-DC) and nimesulide were added into the cultured TE-1 cell line. Promoter methylation status of cyclooxygenase-2 was examined by bisulfate sequencing analysis. RT-PCR was used to determine the expression of COX-2 mRNA. Cells proliferation of ESCC was tested with MTT reduction assay. Prostaglandin E2(PGE2 ) value was examined by ELISA.
Results Lower expression of COX-2 mRNA was found in TE-1 cells, while its promoter methylation status was high(58.3%). After treatment with 10 μmol/L 5-Aza-DC, the methylation status was decreased to 30%, on the other hand the mRNA level was increased. Single treatment with nimesulide showed lower suppressing effect compared to combined interference, the reduction value was 16.2% vs 48.63%, respectively(P<0.05). The concentration of PGE2 was raised after 5-Aza-DC treatment from 553.96 pg/mL to 647.54 pg/mL.
Conclusion For lower expression of COX-2 ESCC, promoter hypermethylation may be a mechanism to control gene expression. Demethylating could increase COX-2 mRNA expression. Combined treatment of ESCC with 5-Aza-DC and selective COX-2 inhibitor may be an alternative choice for depressing ESCC.

Key words: esophageal squamous cell carcinoma(ESCC), cyclooxygenase2(COX2), methylation, nimesulide