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Epigenetic silencing of miR-137 is an early event in colorectal carcinogenesis.

ABSTRACT: Global downregulation of microRNAs (miRNA) is a common feature in colorectal cancer (CRC). Whereas CpG island hypermethylation constitutes a mechanism for miRNA silencing, this field largely remains unexplored. Herein, we describe the epigenetic regulation of miR-137 and its contribution to colorectal carcinogenesis. We determined the methylation status of miR-137 CpG island in a panel of six CRC cell lines and 409 colorectal tissues [21 normal colonic mucosa from healthy individuals (N-N), 160 primary CRC tissues and their corresponding normal mucosa (N-C), and 68 adenomas]. TaqMan reverse transcription-PCR and in situ hybridization were used to analyze miR-137 expression. In vitro functional analysis of miR-137 was performed. Gene targets of miR-137 were identified using a combination of bioinformatic and transcriptomic approaches. We experimentally validated the miRNA:mRNA interactions. Methylation of the miR-137 CpG island was a cancer-specific event and was frequently observed in CRC cell lines (100%), adenomas (82.3%), and CRC (81.4%), but not in N-C (14.4%; P < 0.0001 for CRC) and N-N (4.7%; P < 0.0001 for CRC). Expression of miR-137 was restricted to the colonocytes in normal mucosa and inversely correlated with the level of methylation. Transfection of miR-137 precursor in CRC cells significantly inhibited cell proliferation. Gene expression profiling after miR-137 transfection discovered novel potential mRNA targets. We validated the interaction between miR-137 and LSD-1. Our data indicate that miR-137 acts as a tumor suppressor in the colon and is frequently silenced by promoter hypermethylation. Methylation silencing of miR-137 in colorectal adenomas suggests it to be an early event, which has prognostic and therapeutic implications.

SUBMITTER: Balaguer F

PROVIDER: S-EPMC2922409 | biostudies-literature | 2010 Aug

REPOSITORIES: biostudies-literature

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Epigenetic silencing of miR-137 is an early event in colorectal carcinogenesis.

Balaguer Francesc F Link Alexander A Lozano Juan Jose JJ Cuatrecasas Miriam M Nagasaka Takeshi T Boland C Richard CR Goel Ajay A

Cancer research 20100803 16

Global downregulation of microRNAs (miRNA) is a common feature in colorectal cancer (CRC). Whereas CpG island hypermethylation constitutes a mechanism for miRNA silencing, this field largely remains unexplored. Herein, we describe the epigenetic regulation of miR-137 and its contribution to colorectal carcinogenesis. We determined the methylation status of miR-137 CpG island in a panel of six CRC cell lines and 409 colorectal tissues [21 normal colonic mucosa from healthy individuals (N-N), 160 ...[more]

PMID: 20682795

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Project description:BACKGROUND:MicroRNAs are dysregulated in colorectal cancer and subsets correlated with advanced tumor stage and metastasis. Data are lacking on microRNA dysregulation from early to late-stage disease. OBJECTIVE:The purpose of this study was to identify a microRNA signature associated with the primary tumor and metastatic site in stage IV disease and to examine whether the signature is evident in earlier stages. DESIGN:A microRNA profile was generated and then explored in normal colon tissue (n = 5), early stage (stage I and II; n = 10), and late-stage (stage III and IV; n = 14) colorectal primary tumors via polymerase chain reaction to delineate molecular events that may promote colorectal carcinogenesis. SETTING:Genome-wide microRNA expression profiling was performed. PATIENTS:A total of 14 patient-matched stage IV primary colorectal cancer tumors and corresponding liver metastases were included. MAIN OUTCOME MEASURES:MicroRNA array technology was used to identify microRNA expression-predictive metastatic potential in the primary tumor. RESULTS:A distinct 9-member signature group of microRNAs was concurrent in stage IV primary colorectal cancer and their corresponding liver metastases, when compared with surrounding unaffected colon and liver tissue (microRNA-18b, microRNA-93, microRNA-182, microRNA-183, microRNA21, microRNA-486-5p, microRNA-500a, microRNA-552, and microRNA-941). Of the microRNA panel, only microRNA486-5p was differentially expressed in early stage colorectal cancer samples compared with normal tissue (p = 0.001) and additionally differentially expressed between late-stage colorectal cancer samples and normal tissue (p < 0.01). LIMITATIONS:Our microRNA profile was generated in a small subset of patients and will require validation in more samples. CONCLUSIONS:We identified a distinct microRNA signature in primary colon and matched metastatic disease. On additional investigation, 1 microRNA was differentially expressed in both early and late-stage cancer patient samples, and it may herald an early event in colorectal carcinogenesis. This study warrants additional investigation with a larger patient cohort to better understand the effect of microRNAs in carcinogenesis. See Video Abstract at http://links.lww.com/DCR/A723.

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Epigenetic silencing of miR-137 is an early event in colorectal carcinogenesis.

Publications

Epigenetic silencing of miR-137 is an early event in colorectal carcinogenesis.

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