en زیست شناسی ملکولی Molecular Biology مقالات اصلی Original Article <div style="text-align: justify;"><strong><em>Background:</em></strong> Abnormal DNA methylation leading to altered transcription of certain genes occurs frequently in colorectal cancer (CRC). As with protein-coding genes, microRNAs (miRNAs) may be targeted for methylation in CRC; however, the methylation state of miRNA genes in CRC, especially in primary lesions, has not yet been completely elucidated. To understand the impact of DNA methylation on the miR-200c/141 cluster promoter, we investigated the methylation and expression of miR-141 in precancerous lesions and colorectal cancer.<br> <br> <strong><em>Methods:</em></strong> In this cross-sectional study, 208 colorectal tissue samples, including 34 tumor tissue samples, 60 precancerous lesions with matched normal&nbsp;adjacent&nbsp;tissues, and 20 normal tissue samples, were collected. Promoter methylation of the miR-200c/141 cluster was studied using methylation-specific PCR. MiR-141 expression was examined using quantitative real-time PCR.<br> <br> <strong><em>Results:</em></strong> Our findings showed that the miR-200c/141 cluster promoter region was most frequently hypermethylated in colorectal tumors and adenomatous polyps, but unmethylated in hyperplastic polyp tissues (P < 0.001). DNA methylation of the miR-200c/141 cluster and the tumor stage were significantly correlated (P = 0.002); however, miR-141 expression difference between the tumor and polyp samples was not significant (p = 0.6).<br> <br> <strong><em>Conclusions:</em></strong> The DNA methylation status of the miR-200c/141 cluster could serve as a progression&nbsp;marker from&nbsp;benign&nbsp;polyps&nbsp;to&nbsp;colorectal&nbsp;cancer.</div> Colonic Polyps, Colorectal Cancer, DNA methylation, MiR-141 208 215 http://rbmb.net/browse.php?a_code=A-10-313-1&slc_lang=en&sid=1 Zahra Taheri zahra_taheri_2005@yahoo.com 100319475328460017321 100319475328460017321 No Department of Biology, Science and Research Branch, Islamic Azad University, Tehran, Iran. Hamid Asadzadeh Aghdaei hamid.assadzadeh@gmail.com 100319475328460017322 100319475328460017322 No Basic and Molecular Epidemiology of Gastroenterology Disorders Research Center, Research Institute for Gastroenterology and Liver Diseases, Shahid Beheshti University of Medical Sciences, Tehran, Iran. Shiva Irani shi_irani@yahoo.com 100319475328460017323 100319475328460017323 Yes Department of Biology, Science and Research Branch, Islamic Azad University, Tehran, Iran. Mohammad Hossein Modarressi modaresi@tums.ac.ir 100319475328460017324 100319475328460017324 No Department of Medical Genetics, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran. Zahra Noormohammadi marjannm@yahoo.com 100319475328460017325 100319475328460017325 No Department of Biology, Science and Research Branch, Islamic Azad University, Tehran, Iran.