title: MiR-145 modulates multiple components of the insulin-like growth factor pathway in hepatocellular carcinoma.
abstract: Profiling of microRNA expression in human cancers has highlighted downregulation of miR-145 as a common event in epithelial malignancies. Here, we describe recurrent underexpression of miR-145 in hepatocellular carcinoma (HCC) and the identification of a biological pathway by which miR-145 exerts its functional effects in liver tumorigenesis. In a cohort of 80 HCC patients, quantitative reverse transcription polymerase chain reaction corroborated reduced miR-145 expression in 50% of tumors, which also correlated with a shorter disease-free survival of patients. One HCC tumor analyzed with low endogenous miR-145 was propagated as cell line. This in vitro model HKCI-C2 maintained low miR-145 level and upon restoration of miR-145 expression, a consistent inhibitory effect on cell viability and proliferation was readily found. Flow cytometric analysis indicated that miR-145 re-expression could induce G(2)-M cell cycle arrest and apoptosis. Multiple in silico algorithms predicted that miR-145 could target a number of genes along the insulin-like growth factor (IGF) signaling, including insulin receptor substrate (IRS1)-1, IRS2 and insulin-like growth factor 1 receptor. We found protein expression of these putative targets was concordantly downregulated in the presence of miR-145. Luciferase reporter assay further verified direct target association of miR-145 to specific sites of the IRS1 and IRS2 3'-untranslated regions. Subsequent analysis also affirmed miR-145 modulation on the IGF signaling cascade by reducing its downstream mediator, namely the active β-catenin level. Taken together, our study shows for the first time the pleiotropic effect of miR-145 in targeting multiple components of the oncogenic IGF signaling pathway in HCC.
authors.affiliation: Department of Anatomical and Cellular Pathology, The Chinese University of Hong Kong, Shatin, NT, Hong Kong.
authors.forename: Priscilla T-Y
authors.initials: PT
authors.lastname: Law
authors.forename: Arthur K-K
authors.initials: AK
authors.lastname: Ching
authors.forename: Anthony W-H
authors.initials: AW
authors.lastname: Chan
authors.forename: Queenie W-L
authors.initials: QW
authors.lastname: Wong
authors.forename: Chun-Kwok
authors.initials: CK
authors.lastname: Wong
authors.forename: Ka-Fai
authors.initials: KF
authors.lastname: To
authors.forename: Nathalie
authors.initials: N
authors.lastname: Wong
mesh_terms: D017209:Apoptosis; D006528:Carcinoma, Hepatocellular / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D049109:Cell Proliferation; D002470:Cell Survival; D002478:Cells, Cultured; D018572:Disease-Free Survival; D059565:G2 Phase Cell Cycle Checkpoints; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D055504:Insulin Receptor Substrate Proteins / Q000378:metabolism; D008099:Liver / Q000473:pathology; D008113:Liver Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D035683:MicroRNAs / Q000235:genetics* / Q000378:metabolism*; D017526:Receptor, IGF Type 1 / Q000378:metabolism; D015398:Signal Transduction / Q000235:genetics; D013002:Somatomedins / Q000378:metabolism*; D051176:beta Catenin / Q000096:biosynthesis
chemical_list: C526292:IRS1 protein, human; C526297:IRS2 protein, human; D055504:Insulin Receptor Substrate Proteins; C541010:MIRN145 microRNA, human; D035683:MicroRNAs; D013002:Somatomedins; D051176:beta Catenin; D017526:Receptor, IGF Type 1