Aberrant methylation of microRNA-193b in human Barrett's esophagus and esophageal adenocarcinoma

Abstract

The present study aimed to investigate the expression and regulation of microRNA-193b (miR-193b) in tissues and cells from esophageal cancer and Barrett's esophagus (BE). Surgical biopsies of esophageal lesions and adjacent normal tissues were obtained, and the miR-193b expression and promoter methylation status were examined. Human BE and esophageal cancer cells were analyzed for miR-193b expression and promoter methylation, with or without treatment with the hypomethylating agent 5-azacytidine. Immunohistochemistry was performed to determine the expression and distribution of Kirsten rat sarcoma viral oncogene homolog (K-Ras), a target of miR-193b. miR-193b expression was significantly downregulated in BE and esophageal cancer tissues compared with corresponding normal tissues. The miR-193b level was significantly reduced in esophageal cancer compared with BE tissue. 5-Azacytidine treatment resulted in a significant upregulation of miR-193b in BE and esophageal cancer cells. Methylation-specific polymerase chain reaction analysis and bisulfite pyrosequencing confirmed hypermethylation of miR-193b promoter regions in esophageal cancer and BE cells, whereas hypermethylation was not observed in normal esophageal squamous epithelial cells. The methylation rate in BE and esophageal cancer tissues was significantly increased compared with the adjacent normal esophageal tissues. BE and esophageal cancer tissues exhibited increased K-Ras protein expression levels compared with the adjacent normal tissues. To the best of our knowledge, this is the first report describing DNA methylation-mediated silencing of miR-193b in esophageal cancer and BE tissues.