Hepatitis B virus (HBV) RNA in serum has recently been linked to efficacy and prognosis of chronic hepatitis B (CHB) treatment. This study explored the nature, origin, underlying mechanisms, and potential clinical significance of serum HBV RNA. The levels of HBV DNA and RNA were determined in the supernatant of induced HepAD38, HBV-expressing HepG2.2.15 cells and primary human hepatocytes (PHH), and in the serum of transgenic mice and CHB patients. NP-40 and proteinase K treatment, sucrose density gradient centrifugation, electron microscopy, northern blot, multiple identification PCRs and 5' rapid-amplification of cDNA ends were performed to identify the nature of serum HBV RNA. Although significantly lower than HBV DNA levels, abundant HBV RNA was present in the serum of CHB patients. A series of experiments demonstrated that serum HBV RNA was pregenome RNA (pgRNA) and present in virus-like particles. HBV pgRNA virion levels increased after blocking the reverse transcription activity of HBV DNA polymerase, and decreased after blocking the encapsidation of pgRNA. Furthermore, the presence of HBV pgRNA virion was associated with risk of viral rebound after discontinuation of nucleot(s)ide analogues (NAs) therapy in CHB patients. Serum HBV RNA was confirmed to be pgRNA present in virus-like particles. HBV pgRNA virions were produced from encapsidated particles in which the pgRNA was non- or partially reverse transcribed. Clinically, HBV pgRNA virion might be a potential biomarker for monitoring safe discontinuation of NA-therapy. HBV may have another virion form in which the nucleic acid is composed of RNA, not DNA. The level of HBV RNA virion in serum may be associated with risk of HBV viral rebound after withdrawal of treatment, and therefore, a potential predictive biomarker to monitor the safe discontinuation of nucleot(s)ide analogues-therapy.

Although hepatitis B virus (HBV) integration into the human genome has been considered as one of the major causative factors to hepatocarcinogenesis, the underlying mechanism(s) was still elusive. Here we investigate the essential difference(s) of HBV integration between HCC tumor and adjacent non-tumor tissues and explore the factor(s) that determine the oncogenicity of HBV integration. 1115 HBV integration sites were collected from four recent studies. Functional annotation analysis of integration targeted host genes (ITGs) was performed using DAVID based on Gene Ontology and KEGG pathway databases. Array-based expression profiles, real-time qPCR and western blot were used to detect the expression of recurrent integration targeted genes (RTGs). The biological consequences of the overexpression of UBXN8 in 8 HCC cell lines were studied in vitro. HBV is prone to integrate in genic regions (exons, introns, and promoters) and gene-dense regions. Functional annotation analysis reveals that, compared to those in adjacent non-tumor tissues, ITGs in HCC tumor tissues were significantly enriched in functional terms related to negative regulation of cell death, transcription regulation, development and differentiation, and cancer related pathways. 32% of the 75 RTGs identified in this analysis expressed abnormally in HCC tissues. UBXN8, one of the RTGs, was identified as a new tumor suppressor candidate which functions in a TP53 dependent manner. The oncogenicity of HBV integration was determined, to some extend by the function of HBV integration targeted host genes in HCC.

BACKGROUND: Recent research has suggested that the oncomir microRNA 155 (miR‐155) is up‐regulated in hepatocellular carcinoma (HCC). In this study, the authors investigated the tumorigenic mechanism of this oncomir in the development of HCC.METHODS: Quantitative reverse transcriptase‐polymerase chain reaction (RT‐PCR) was conducted to analyze the expressions of miR‐155 and its potential target genes in paired tumor tissues and adjacent tumor‐free tissues and in disease‐free liver tissue samples. The in silico predicted target genes of miR‐155 were assessed by dual‐luciferase reporting assay, real‐time RT‐PCR, and Western blot analyses. U6 promoters that drive miR‐155 precursor overexpression and miR‐155 tough decoy knock‐down constructs were used to study its affects on cell proliferation in vitro and on tumor formation in nude mice.RESULTS: Quantitative RT‐PCR demonstrated a gradual ascension of miR‐155 expression in cirrhotic liver tissues and in HCC tumor tissues compared with low expression levels in normal liver tissues. Ectopic expression of miR‐155 in HepG2 cells enhanced its tumorigenesis, whereas depletion of the endogenous miR‐155 reversed these tumorigenic properties. Ectopic expression of sex‐determining region Y box 6 (SOX6) was able to reverse the growth‐promoting property of miR‐155. Concordantly, the results demonstrated for the first time that SOX6 is a direct target of miR‐155. Further analysis revealed that SOX6 reduced cell growth by up‐regulating p21waf1/cip1 expression in a p53‐dependent manner. In addition, a decline in p21waf1/cip1 expression caused by miR‐155 could be reversed by SOX6 expression.CONCLUSIONS: The current data indicated that SOX6 is a novel target of miR‐155 and that miR‐155 enhances liver cell tumorigenesis at least in part through the novel miR‐155/SOX6/p21waf1/cip1 axis. These findings suggest that miR‐155 may be a potential target for HCC treatment. Cancer 2012. © 2011 American Cancer Society.