title: Hepatitis B virus X protein promotes hepatocellular carcinoma transformation through interleukin-6 activation of microRNA-21 expression.
abstract: Hepatocellular carcinoma (HCC) is one of the most common cancers worldwide, and chronic hepatitis B virus (HBV) infection is the major risk factor of HCC. The virus encodes HBV X (HBx) protein that plays a critical role in the development of HCC. Studies have revealed numerous HBx-altered genes and signalling pathways that heavily contribute to tumourigenesis of non-tumour hepatocytes. However, the role of HBx in regulating other critical gene regulators such as microRNAs is poorly understood, which impedes the exploration of a complete HBx-associated carcinogenic network. Besides, critical microRNAs that drive the transformation of non-tumour hepatocytes are yet to be identified. Here, we overexpressed C-terminal truncated HBx protein in a non-tumour hepatocyte cell line MIHA, and measured a panel of cancer-associated miRNAs. We observed that oncogenic miR-21 was upregulated upon ectopic expression of this viral protein variant. HBx-miR-21 pathway was prevalent in HCC cells as inhibition of HBx in Hep3B and PLC/PRF/5 cells significantly suppressed miR-21 expression. Subsequently, we showed that the upregulation of miR-21 was mediated by HBx-induced interleukin-6 pathway followed by activation of STAT3 transcriptional factor. The high dependency of miR-21 expression to HBx protein suggested a unique viral oncogenic pathway that could aberrantly affect a network of gene expression. Importantly, miR-21 was essential in the HBx-induced transformation of non-tumour hepatocytes. Inhibition of miR-21 effectively attenuated anchorage-independent colony formation and subcutaneous tumour growth of MIHA cells. Our study suggested that overexpression of miR-21 was critical to promote early carcinogenesis of hepatocytes upon HBV infection.
authors.affiliation: School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong.
authors.forename: Chi Han
authors.initials: CH
authors.lastname: Li
authors.affiliation: School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong.
authors.forename: Feiyue
authors.initials: F
authors.lastname: Xu
authors.affiliation: School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong.
authors.forename: Sheungching
authors.initials: S
authors.lastname: Chow
authors.affiliation: School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong.
authors.forename: Lu
authors.initials: L
authors.lastname: Feng
authors.affiliation: Department of Internal Medicine, College of Medicine, East Tennessee State University, Johnson City, TN 37604, USA.
authors.forename: Deling
authors.initials: D
authors.lastname: Yin
authors.affiliation: School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong.
authors.forename: Tzi Bun
authors.initials: TB
authors.lastname: Ng
authors.affiliation: School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong; Shenzhen Research Institute, The Chinese University of Hong Kong, Shenzhen 518057, China. Electronic address: frankch@cuhk.edu.hk.
authors.forename: Yangchao
authors.initials: Y
authors.lastname: Chen
mesh_terms: D000818:Animals; D015153:Blotting, Western; D006528:Carcinoma, Hepatocellular / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D002460:Cell Line; D045744:Cell Line, Tumor; D002471:Cell Transformation, Neoplastic / Q000235:genetics* / Q000378:metabolism; D015870:Gene Expression; D057809:HEK293 Cells; D022781:Hepatocytes / Q000166:cytology / Q000378:metabolism; D006801:Humans; D015850:Interleukin-6 / Q000235:genetics* / Q000378:metabolism; D008113:Liver Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D035683:MicroRNAs / Q000235:genetics*; D009154:Mutation; D010766:Phosphorylation; D034622:RNA Interference; D020133:Reverse Transcriptase Polymerase Chain Reaction; D050796:STAT3 Transcription Factor / Q000378:metabolism; D015534:Trans-Activators / Q000235:genetics* / Q000378:metabolism; D014183:Transplantation, Heterologous; D054334:Viral Regulatory and Accessory Proteins
chemical_list: D015850:Interleukin-6; C531950:MIRN21 microRNA, mouse; D035683:MicroRNAs; D050796:STAT3 Transcription Factor; D015534:Trans-Activators; D054334:Viral Regulatory and Accessory Proteins; C057628:hepatitis B virus X protein
keywords: Hepatitis B X protein; Hepatitis B virus; Hepatocellular carcinoma; Interleukin 6; MicroRNA-21