Inflammatory Nitrergic Dysfunction Evokes Intestinal Dysmotility

COX-2 expressing vector, and HCA-7, a COX-2 expressing human colon cancer cells were used. Stemness was estimated by ability to form spheroid known to enrich in stem cells and oct-4 expression. DNA methyltransferase activity, demethylase activity, and DNA global hypomethylation were measured. Promoter methylation of tumor suppressor genes (p16, E-cadherin, and hMLH1), and an oncogene, S100A, was determined by MSP or COBRA. Expressions of DNMT-1, -3A, and -3B and demethylase genes (AID and glycosylase) were determined by RT-PCR. [Results] RIE-COX showed significantly elevated potential for spheroid formation, oct-4 expression, DNA demethylase activity and expression, promoter hypermethylation of tumor suppressors and hypomethylation of S100A, and DNMT-3a expression and activity, and it also showed significantly downregulated global DNA methylation, compared with RIE. siRNA for COX-2 or celecoxib, a COX-2 specific inhibitor, significantly inhibited spheroid formation, global hypomethylation, hypermethylation of tumor suppressor genes, and DNA demethylase activity/expression in HCA-7. siRNA for DNMT3a or AID partly suppressed spheroid formation of HCA-7 and oct-4 expression. [Conclusion] These results indicate that COX-2 is involved in intricate epigenetic regulation; simultaneous global hypomethylation and gene-specific hypermethylation, through discrete modulation of DNMT/demethylase expression, and it is also suggested that COX-2 inhibitors have a potential to prevent epigenetic dysregulation and aberrant biology of cancer stem cell in carcinogenesis.