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Gastroenterology. 2013 Aug;145(2):426-36.e1-6. doi: 10.1053/j.gastro.2013.04.004. Epub 2013 Apr 9.

Genetic and epigenetic down-regulation of microRNA-212 promotes colorectal tumor metastasis via dysregulation of MnSOD.

Author information

1
State Key Laboratory of Oncology in South China, Sun Yat-sen University Cancer Center, Guangzhou, PR China.

Abstract

BACKGROUND & AIMS:

Altered functions of microRNAs (miRNAs) have been associated with colorectal cancer (CRC). miR-212 is transcribed from a stable intron of a non-protein coding gene, and is reportedly down-regulated in different tumor types. We investigated the role of miR-212 in colorectal carcinogenesis and progression.

METHODS:

We analyzed the expression of miR-212 by real-time polymerase chain reaction (PCR) analysis of colorectal cell lines and 180 paired tumor samples and surrounding healthy tissue. We overexpressed and knocked down miR-212 in CRC cell lines and assessed the in vitro effects. We also studied the effects of miR-212 overexpression on metastasis of tumors grown from HCT116 cells in nude mice.

RESULTS:

Overexpression of miR-212 inhibited CRC cell migration and invasion in vitro and formation of intrahepatic and pulmonary metastasis in vivo. We identified manganese superoxide dismutase (MnSOD) messenger RNA as a direct target of miR-212, and observed an inverse correlation between the level of miR-212 and MnSOD protein in colorectal tumor samples. MnSOD was required for down-regulation of epithelial markers and up-regulation of mesenchymal markers in CRC cells, indicating that it promoted the epithelial-mesenchymal transition. Overexpression of miR-212 reduced the levels of MnSOD to block the epithelial-mesenchymal transition process. Loss of heterozygosity and promoter hypermethylation each contributed to the down-regulation of miR-212. Reduced levels of miR-212 were associated with a more aggressive tumor phenotype and short disease-free survival times of patients (P = .0045; overall survival, P = .0015).

CONCLUSIONS:

miR-212 is down-regulated in human CRC tissues via genetic and epigenetic mechanisms. miR-212 might prevent tumor progression by targeting MnSOD messenger RNA; reduction of miR-212 could be a prognostic marker for patients with CRC. miR-212 and MnSOD might also be therapeutic targets for cancer.

KEYWORDS:

3′-UTR; 3′-untranslated region; CRC; Colorectal Cancer; EMT; Epigenetic Regulation; Gene Expression; Genetic Alteration; LOH; MnSOD; NC; PCR; colorectal cancer; epithelial−mesenchymal transition; loss of heterozygosity; manganese superoxide dismutase; miRNA; microRNA; negative control; polymerase chain reaction; si; small interfering

PMID:
23583431
DOI:
10.1053/j.gastro.2013.04.004
[Indexed for MEDLINE]

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