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SP1 mediates the link between methylation of the tumour suppressor miR-149 and outcome in colorectal cancer

Authors


  • No conflicts of interest were declared.

Huan-Long Qin, Department of Surgery, Shanghai Tenth People's Hospital Affiliated to Tongji University, 301 Middle Yanchang Road, Shanghai 200072, China. e-mail: hlong_qin@live.com

Abstract

Although recent studies indicate that DNA methylation contributes to the down-regulation of microRNAs (miRNAs) in colorectal cancer (CRC), this field remains largely unexplored. To identify methylation-silenced miRNAs and clarify their role in CRC, we performed a microarray analysis and screened for miRNAs that were induced in CRC cells by 5-aza-2′-deoxycytidine treatment or by the knockdown of DNA methyltransferases. The DNA methylation status of the candidate miRNA was analysed by bisulphite sequencing PCR and methylation-specific PCR. We found that miRNA-149 (miR-149) was epigenetically silenced in CRC and down-regulation of miR-149 was associated with hypermethylation of the neighbouring CpG island (CGI). Quantitative RT-PCR analysis demonstrated that the miR-149 level was markedly reduced in 51.6% of the CRC tissues compared with matched non-cancerous tissues. In addition, low expression of miR-149 was associated with a greater depth of invasion (equation image), lower 5-year survival rate (equation image), and was found to be an independent prognostic factor for overall survival (equation image) in a multivariate analysis. Moreover, transfection of miR-149 inhibited cell growth and invasion of CRC cells in vitro. We also identified mRNA for Specificity Protein 1 (SP1, Sp1), a potential oncogenic protein, as a target of miR-149. Our data suggest that, as a methylation-sensitive miRNA, miR-149 may play an important role as a tumour suppressor in CRC, which has prognostic and therapeutic implications. Copyright © 2012 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

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