COX-2 inhibition induces apoptosis in human esophageal epithelial cells: implication for chemoprevention

Abstract

Background and Objective: Cyclooxygenase (COX-2) inhibitors suppress cell proliferation and induce apoptosis in several GI cancer cell lines. However, it is not clear whether they have effect on precancerous cells. In this study, NS-398, a specific COX-2 inhibitor, was used to study the effect of COX-2 inhibition on immortalized human esophageal epithelial cells. Methods: Primary culture of normal human esophageal epithelial cells was used for immortalization. Open reading frames of human papilloma virus type 16 E6/E7 and hTERT, the catalytic subunit of telomerase, were used in esophageal cell infection. The immortalized cells in passage 36 were used for NS-398 treatment. After 24h treatment, the effect of NS- 398 on immortalized esophageal cells was determined by MTT assay, flow cytometry, semiquantitative RT-PCR, and Western blot analysis. Result: An immortalized esophageal epithelial cell model, named NECA6E6E7/hTERT, was established successfully. The expression of COX-2 mRNA in NECA6E6E7/hTERT passage 36 was 52 folds higher than that in primary culture normal cells (untransfection). MTT analysis showed that NS-398 suppressed the proliferation of NECA6E6E7/hTERT in doseand time-dependent manners, while cytometric analysis found an increase in the G1 phase and a decrease in the S phase. Moreover, an increase of phosphorylated-Rb and a decrease of bcl-2 protein were observed after NS-398 treatment. Conclusion: NS-398 can suppress proliferation and induce apoptosis in non-cancer esophageal cells, implying that COX-2 inhibition may offer an effective approach for esophageal cancer chemoprevention.