Methylation Status of miR-200b Promoter in Colorectal Polyp and Adenocarcinoma Tissues

Background: Aberrant DNA methylation is a common molecular feature in colorectal cancer (CRC). Hypermethylation of miR-200b promoter, as an epigenetic factor, is involved in CRC tumorigenesis. The methylation status of miR-200b has been examined in CRC and adjacent normal tissues.  Objectives: This study aimed to investigate miR-200b methylation in a series of colorectal adenomatous polyps, hyperplastic polyps, and adenocarcinoma tissues as precursors of CRC in the Iranian population for the first time. Materials and Methods: In this cross-sectional study (2017-2018), the methylation status of the miR-200b promoter was investigated using methylation-specific PCR in 131 fresh samples, including 30 adenocarcinoma specimens, 17 tumor-adjacent normal tissues, 78 primary lesions (55 adenomatous polyps and 23 hyperplastic polyps) and 6 healthy individuals. Results: Methylation of miR-200b was detected in adenocarcinoma samples (86%) and adenomatous polyps (85%); however, most of the hyperplastic polyps were unmethylated (69.6%). Neither control individuals nor tumor-adjacent normal tissues exhibited methylation in the miR-200b promoter. Aberrant methylation of miR-200b was significantly more common in tumor tissues and adenomatous polyps than in hyperplastic polyps (P<0.0001) and tumor-adjacent normal samples (P<0.0001). Conclusion: Methylation status of the miR-200b promoter was significantly altered during CRC development and may be identified as an attractive biomarker for the early detection of the disease.