Characterization of global microRNA expression reveals oncogenic potential of miR-145 in metastatic colorectal cancer

Greg M Arndt,Kathy Retzlaff,Chunyan Zhang,Michael Eisbacher,Mitch Raponi,Anton Bittner,Hongtao Fan,Nham Tran,Angela Lai,Lara M Cullen,Lesley Dossey,Riki Druker

doi:10.1186/1471-2407-9-374

Abstract

BackgroundMicroRNAs (MiRNAs) are short non-coding RNAs that control protein expression through various mechanisms. Their altered expression has been shown to be associated with various cancers. The aim of this study was to profile miRNA expression in colorectal cancer (CRC) and to analyze the function of specific miRNAs in CRC cells. MirVana miRNA Bioarrays were used to determine the miRNA expression profile in eight CRC cell line models, 45 human CRC samples of different stages, and four matched normal colon tissue samples. SW620 CRC cells were stably transduced with miR-143 or miR-145 expression vectors and analyzed in vitro for cell proliferation, cell differentiation and anchorage-independent growth. Signalling pathways associated with differentially expressed miRNAs were identified using a gene set enrichment analysis.ResultsThe expression analysis of clinical CRC samples identified 37 miRNAs that were differentially expressed between CRC and normal tissue. Furthermore, several of these miRNAs were associated with CRC tumor progression including loss of miR-133a and gain of miR-224. We identified 11 common miRNAs that were differentially expressed between normal colon and CRC in both the cell line models and clinical samples. In vitro functional studies indicated that miR-143 and miR-145 appear to function in opposing manners to either inhibit or augment cell proliferation in a metastatic CRC model. The pathways targeted by miR-143 and miR-145 showed no significant overlap. Furthermore, gene expression analysis of metastatic versus non-metastatic isogenic cell lines indicated that miR-145 targets involved in cell cycle and neuregulin pathways were significantly down-regulated in the metastatic context.ConclusionMiRNAs showing altered expression at different stages of CRC could be targets for CRC therapies and be further developed as potential diagnostic and prognostic analytes. The identified biological processes and signalling pathways collectively targeted by co-expressed miRNAs in CRC provide a basis for understanding the functional role of miRNAs in cancer.

Highlights

MicroRNAs (MiRNAs) are short non-coding RNAs that control protein expression through various mechanisms
Taqman miRNA expression assays were performed on 169 miRNAs from 4 matched fresh frozen and formalin fixed paraffin embedded (FFPE) samples and Ct measurements were compared by linear regression
In summary we have screened a large set of clinical colorectal cancer (CRC) samples and matched normal colorectal tissue for miRNA expression

Summary

Introduction

MicroRNAs (MiRNAs) are short non-coding RNAs that control protein expression through various mechanisms. Their altered expression has been shown to be associated with various cancers. Most sporadic CRC cases include changes in the WNT, KRAS, TGFβ, β-catenin and p53 pathways, there appears to be added complexity with additional signaling pathways showing accumulated mutations [5,6]. This suggests that alternative factors contribute to CRC and that underlying levels of regulation exist to control the complex cross-talk between different signal transduction pathways

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