Hepatitis B virus X protein downregulates expression of the miR-16 family in malignant hepatocytes in vitro

• Published in: British journal of cancer 2011-06, Vol.105 (1), p.146-153
• Main Authors: Wu, G, Yu, F, Xiao, Z, Xu, K, Xu, J, Tang, W, Wang, J, Song, E
• Format: Article
• Language: English
• Subjects: 631/326/596/2555; 631/92/555; 692/699/255/234/2513/1549; 692/699/67/1504/1610; Apoptosis; Biological and medical sciences; Biomedical and Life Sciences; Biomedicine; Blotting, Western; Cancer Research; Carcinoma, Hepatocellular - genetics; Carcinoma, Hepatocellular - metabolism; Cell Cycle; Cell Proliferation; Cells, Cultured; Down-Regulation; Drug Resistance; Epidemiology; Gastroenterology. Liver. Pancreas. Abdomen; Hepatitis B virus; Hepatocytes - metabolism; Hepatocytes - pathology; Humans; In Vitro Techniques; Liver Neoplasms - genetics; Liver Neoplasms - metabolism; Liver. Biliary tract. Portal circulation. Exocrine pancreas; Luciferases - metabolism; Medical sciences; MicroRNAs - genetics; MicroRNAs - metabolism; Molecular Diagnostics; Molecular Medicine; Oncology; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger - genetics; Trans-Activators - genetics; Trans-Activators - metabolism; Tumors; Viral Regulatory and Accessory Proteins
• ISSN: 0007-0920; 1532-1827
• DOI: 10.1038/bjc.2011.190

Background: Hepatitis B virus X protein (HBx) is involved in the initiation and progression of hepatocellular carcinoma (HCC) by regulating the host protein-coding genes. In this study, we showed that HBx altered the expression of microRNAs (miRNAs) to promote proliferation and transformation in malignant hepatocytes in vitro. Methods: miRNA microarray and quantitative reverse-transcription polymerase chain reactions (qRT-PCRs) were performed to identify miRNAs that were differentially regulated by HBx in HCC cells. Protein, mRNA, and miRNA expression analyses; cell cycle and apoptosis analyses; loss/gain-of-function analysis; and luciferase reporter assays were performed to delineate the consequences of miR-16 family repression in HepG2 cells. Results: Hepatitis B virus X protein induced widespread deregulation of miRNAs in HepG2 cells, and the downregulation of the miR-16 family was reproducible in HepG2, SK-HEP-1, and Huh7 cells. CCND1 , a target of the miR-16 family, was derepressed by HBx in HepG2 cells. c-Myc mediated the HBx-induced repression of miR-15a/16 in HepG2 cells. Ectopically expressed miR-15a/16 suppressed the proliferation, clonogenicity, and anchorage-independent growth of HBx-expressing HepG2 cells by arresting them in the G1 phase and inducing apoptosis, whereas reduced expression of miR-16 accelerated the growth and cell-cycle progression of HepG2 cells. Conclusions: Hepatitis B virus X protein altered the in vitro expression of miRNAs in host malignant hepatocytes, particularly downregulating the miR-16 family. Repression of miR-15a/16 is c-Myc mediated and is required for the HBx-induced transformation of HepG2 cells in vitro . Therefore, miR-16 family may serve as a therapeutic target for hepatitis B virus (HBV)-associated HCC.