BACKGROUND & AIMS: Bcl-xL, an anti-apoptotic member of the Bcl-2 family, is over-expressed in human hepatocellular carcinoma, conferring a survival advantage to tumour cells. The mechanisms underlying its dysregulation have not been clarified. In the present study, we explored the involvement of microRNAs that act as endogenous sequence-specific suppressors of gene expression. METHODS: The expression profiles of microRNAs in Huh7 hepatoma cells and primary human hepatocytes were compared by microarray analysis. The effect of let-7 on Bcl-xL expression was examined by Western blot and a reporter assay. The involvement of let-7 microRNAs in human tissues was analysed by western blot and reverse transcription-PCR. RESULTS: Microarray analysis, followed by in silico target prediction, identified let-7 microRNAs as being downregulated in Huh7 hepatoma cells in comparison with primary human hepatocytes, as well as possessing a putative target site in the bcl-xl mRNA. Over-expression of let-7c or let-7g led to a clear decrease of Bcl-xL expression in Huh7 and HepG2 cell lines. Reporter assays revealed direct post-transcriptional regulation involving let-7c or let-7g and the 3'-untranslated region of bcl-xl mRNA. Human hepatocellular carcinoma tissues with low expression of let-7c displayed higher expression of Bcl-xL protein than those with high expression of let-7c, suggesting that low let-7 microRNA expression contributes to Bcl-xL over-expression. Finally, expression of let-7c enhanced apoptosis of hepatoma cells upon exposure to sorafenib, which downregulates expression of another anti-apoptotic Bcl-2 protein, Mcl-1. CONCLUSIONS: let-7 microRNAs negatively regulate Bcl-xL expression in human hepatocellular carcinomas and induce apoptosis in cooperation with an anti-cancer drug targeting Mcl-1. Copyright (c) 2010 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.
BACKGROUND & AIMS:Bcl-xL, an anti-apoptotic member of the Bcl-2 family, is over-expressed in humanhepatocellular carcinoma, conferring a survival advantage to tumour cells. The mechanisms underlying its dysregulation have not been clarified. In the present study, we explored the involvement of microRNAs that act as endogenous sequence-specific suppressors of gene expression. METHODS: The expression profiles of microRNAs in Huh7hepatoma cells and primary human hepatocytes were compared by microarray analysis. The effect of let-7 on Bcl-xL expression was examined by Western blot and a reporter assay. The involvement of let-7 microRNAs in human tissues was analysed by western blot and reverse transcription-PCR. RESULTS: Microarray analysis, followed by in silico target prediction, identified let-7 microRNAs as being downregulated in Huh7hepatoma cells in comparison with primary human hepatocytes, as well as possessing a putative target site in the bcl-xl mRNA. Over-expression of let-7c or let-7g led to a clear decrease of Bcl-xL expression in Huh7 and HepG2 cell lines. Reporter assays revealed direct post-transcriptional regulation involving let-7c or let-7g and the 3'-untranslated region of bcl-xl mRNA. Humanhepatocellular carcinoma tissues with low expression of let-7c displayed higher expression of Bcl-xL protein than those with high expression of let-7c, suggesting that low let-7 microRNA expression contributes to Bcl-xL over-expression. Finally, expression of let-7c enhanced apoptosis of hepatoma cells upon exposure to sorafenib, which downregulates expression of another anti-apoptotic Bcl-2 protein, Mcl-1. CONCLUSIONS: let-7 microRNAs negatively regulate Bcl-xL expression in humanhepatocellular carcinomas and induce apoptosis in cooperation with an anti-cancer drug targeting Mcl-1. Copyright (c) 2010 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.
Authors: Zifeng Wang; Sheng Lin; Julia Jun Li; Zhenhua Xu; Hong Yao; Xiao Zhu; Dan Xie; Zan Shen; Johnny Sze; Kui Li; Gang Lu; Danny Tat-Ming Chan; Wai Sang Poon; Hsiang-fu Kung; Marie Chia-mi Lin Journal: J Biol Chem Date: 2011-09-08 Impact factor: 5.157
Authors: Katey S S Enfield; Greg L Stewart; Larissa A Pikor; Carlos E Alvarez; Stephen Lam; Wan L Lam; Raj Chari Journal: J Biomed Biotechnol Date: 2011-03-31