Hepatitis B virus and hepatocellular carcinoma

miR-338-3p is down-regulated by hepatitis B virus X and inhibits cell proliferation by targeting the 3'-UTR region of CyclinD1

Hepatitis B virus X protein (HBx) is recognized as an oncogene in hepatocellular carcinoma (HCC). HBx regulates microRNA expression, including down-regulating miR-338-3p in LO2 cells. Here, we investigated miR-338-3p function in HBx-mediated hepatocarcinogenesis. In 23 HBV-infected HCC clinical patient tumor and adjacent non-tumor control tissues, 17 and 19 tumors expressed HBx mRNA and protein, respectively. When considered as a group, HBV-infected HCC tumors had lower miR-338-3p expression than controls; however, miR-338-3p was only significantly down-regulated in HBx-positive tumors, indicating that HBx inversely correlated with miR-338-3p. Functional characterization of miR-338-3p indicated that miR-338-3p mimics inhibited cell proliferation by inducing cell cycle arrest at the G1/S phase as assessed by EdU and cell cycle assays in HBx-expressing LO2 cells. CyclinD1, containing two putative miR-338-3p targets, was confirmed as a direct target using 3′-UTR luciferase reporter assays from cells transfected with mutated binding sites. Mutating the 2397–2403 nt binding site conferred the greatest resistance to miR-338-3p suppression of CyclinD1, indicating that miR-338-3p suppresses CyclinD1 at this site. Overall, this study demonstrates that miR-338-3p inhibits proliferation by regulating CyclinD1, and HBx down-regulates miR-338-3p in HCC. This newly identified miR-338-3p/CyclinD1 interaction provides novel insights into HBx-mediated hepatocarcinogenesis and may facilitate therapeutic development against HCC.

Saudi guidelines for the diagnosis and management of hepatocellular carcinoma: technical review and practice guidelines

Recognizing the significant prevalence of hepatocellular carcinoma (HCC) in Saudi Arabia, and the difficulties often faced in early and accurate diagnoses, evidence-based management, and the need for appropriate referral of HCC patients, the Saudi Association for the Study of Liver diseases and Transplantation (SASLT) formed a multi-disciplinary task force to evaluate and update the previously published guidelines by the Saudi Gastroenterology Association. These guidelines were later reviewed, adopted and endorsed by the Saudi Oncology Society (SOS) as its official HCC guidelines as well. The committee assigned to revise the Saudi HCC guidelines was composed of hepatologists, oncologists, liver surgeons, transplant surgeons, and interventional radiologists. Two members of the task force served as guidelines editors. A wide based search on all published reports on all aspects of the epidemiology, natural history, risk factors, diagnosis, and management of HCC was performed. All available literature was critically examined and available evidence was then classified according to its strength. The whole document and the recommendations were then discussed in detail by members and consensus was obtained. All recommendations in these guidelines were based on the best available evidence, but were tailored to the patients treated in Saudi Arabia. We hope that these guidelines will improve HCC patient care and enhance the multidisciplinary care needed for these patients.

Induction of Bcl-2 expression by hepatitis B virus pre-S2 mutant large surface protein resistance to 5-fluorouracil treatment in Huh-7 cells

BACKGROUND

Hepatocellular carcinoma (HCC) is one of the most common malignancies worldwide with poor prognosis due to resistance to conventional chemotherapy and limited efficacy of radiotherapy. Our previous studies have indicated that expression of Hepatitis B virus pre-S2 large mutant surface antigen (HBV pre-S2Δ) is associated with a significant risk of developing HCC. However, the relationship between HBV pre-S2Δ protein and the resistance of chemotherapeutic drug treatment is still unclear.

METHODOLOGY/PRINCIPAL FINDINGS

Here, we show that the expression of HBV pre-S2Δ mutant surface protein in Huh-7 cell significantly promoted cell growth and colony formation. Furthermore, HBV pre-S2Δ protein increased both mRNA (2.7±0.5-fold vs. vehicle, p=0.05) and protein (3.2±0.3-fold vs. vehicle, p=0.01) levels of Bcl-2 in Huh-7 cells. HBV pre-S2Δ protein also enhances Bcl-2 family, Bcl-xL and Mcl-1, expression in Huh-7 cells. Meanwhile, induction of NF-κB p65, ERK, and Akt phosphorylation, and GRP78 expression, an unfolded protein response chaperone, were observed in HBV pre-S2Δ and HBV pre-S-expressing cells. Induction of Bcl-2 expression by HBV pre-S2Δ protein resulted in resistance to 5-fluorouracil treatment in colony formation, caspase-3 assay, and cell apoptosis, and can enhance cell death by co-incubation with Bcl-2 inhibitor. Similarly, transgenic mice showed higher expression of Bcl-2 in liver tissue expressing HBV pre-S2Δ large surface protein in vivo.

CONCLUSION/SIGNIFICANCE

Our result demonstrates that HBV pre-S2Δ increased Bcl-2 expression which plays an important role in resistance to 5-fluorouracil-caused cell death. Therefore, these data provide an important chemotherapeutic strategy in HBV pre-S2Δ-associated tumor.

Seasonal variation in TP53 R249S-mutated serum DNA with aflatoxin exposure and hepatitis B virus infection

BACKGROUND

Chronic hepatitis B virus (HBV) infection and dietary aflatoxin B1 (AFB1) exposure are etiological factors for hepatocellular carcinoma (HCC) in countries with hot, humid climates. HCC often harbors a TP53 (tumor protein p53) mutation at codon 249 (R249S). In chronic carriers, 1762T/1764A mutations in the HBV X gene are associated with increased HCC risk. Both mutations have been detected in circulating cell-free DNA (CFDNA) from asymptomatic HBV carriers.

OBJECTIVE

We evaluated seasonal variation in R249S and HBV in relation to AFB1 exposure.

METHODS

R249S was quantitated by mass spectrometry in CFDNA in a cross-sectional survey of 473 asymptomatic subjects (237 HBV carriers and 236 noncarriers) recruited in three villages in the Gambia over a 10-month period. 1762T/1764A HBV mutations were detected by quantitative polymerase chain reaction. In addition, the HBV S gene was sequenced in 99 subjects positive for HBV surface antigen (HBsAg).

RESULTS

We observed a seasonal variation of serum R249S levels. Positivity for R249S and average concentration were significantly higher in HBsAg-positive subjects surveyed during April-July (61%; 5,690 ± 11,300 R249S copies/mL serum) than in those surveyed October-March [32% and 480 ± 1,030 copies/mL serum (odds ratio = 3.59; 95% confidence interval: 2.05, 6.30; p < 0.001)]. Positivity for HBV e antigen (HBeAg) (a marker of HBV replication) and viral DNA load also varied seasonally, with 15-30% of subjects surveyed between April and June HBeAg positive, compared with < 10% surveyed during other months. We detected 1762T/1764A mutations in 8% of carriers, half of whom were positive for R249S. We found HBV genotype E in 95 of 99 HBsAg-positive subjects.

CONCLUSION

R249S is detectable in CFDNA of asymptomatic subjects. Evidence of temporal and quantitative variations suggests an interaction among AFB1 exposure, HBV positivity, and replication on TP53 mutation formation or persistence.

Therapeutics Based on microRNA: A New Approach for Liver Cancer

Hepatocellular carcinoma (HCC) is a serious public health hazard. Polygenes involvement, accumulation of genetic and epigenetic changes and immune response of viral vector during gene therapy have resulted in the high mortality rate without marked change. To provide a safeguard for gene therapy and the feasibility for a clinical application, efforts have been focused predominantly upon constructing liver-targeted vector recently. MicroRNAs (miRNAs), a class of short endogenous RNAs, regulate the gene expression at the post-transcriptional level through imperfect base pairing with the 3′-untranslated region of target mRNAs. miRNAs, especially the liver-specific miRNA: miR-122, have multiple functions in liver development and abnormal expression of miRNAs could lead to liver diseases. Altered miRNA expressions have been observed in HCCs, viral hepatitis and hepatic fibrosis. The different expression profiles of miRNAs in HCC suggest that miRNAs may serve as either novel potential targets acting directly as oncogenes or therapeutic molecules working as tumor suppressor genes. Moreover, the abundance in general and liver specificity in particular, all together make them attractive to be considered as elements for hepatic specific targeting viral vector. This review describes recent progress in miRNA investigation on liver associated for better understanding the relationship between miRNA and liver cancer in order to raise prospects for therapy.

Caffeoyl pyrrolidine derivative LY52 inhibits hepatocellular carcinoma invasion via suppressing matrix metalloproteinase-2

PURPOSE

In this study, we examined the effects of LY52, a caffeoyl pyrrolidine derivative designed to fit the S'1 active pocket of gelatinases, on the expressions of matrix metalloproteinases and invasion abilities of hepatocellular carcinoma cells.

METHODS

The effects of LY52 on the proliferations of HepG2 (hepatitis B virus (HBV) negative) and HepG2.2.15 (HBV-producing) cells were detected by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Gelatin zymography was used to detect the effects of LY52 on matrix metalloproteinases expressions and Western blot was used to detect matrix metalloproteinase-2 expressions. Transwell chamber assay was used to detect the effects of LY52 on invasion of the cells.

RESULTS

Gelatin zymography and Western blot showed that matrix metalloproteinase-2 expressions were inhibited by LY52 in a dose-dependent manner, and inhibitory rates of LY52 on HepG2 cells were higher than on HepG2.2.15 cells. Transwell chamber showed that LY52 could significantly inhibit the invasion of both cells, although the inhibitory effects of LY52 on HepG2.2.15 cells were was not as obvious as on HepG2 cells.

CONCLUSIONS

These results suggested that LY52 might inhibit the invasion of hepatocellular carcinoma cells by suppressing matrix metalloproteinase-2, although the inhibitory effects of LY52 on HBV-negative cells were more obvious than that of HBV-infected cells.

Progress in the use of RNA interference as a therapy for chronic hepatitis B virus infection

Chronic infection with hepatitis B virus (HBV) occurs in approximately 6% of the world's population and carriers of the virus are at risk for hepatocellular carcinoma and cirrhosis. Current treatment regimens, which include interferon-α and nucleoside/nucleotide analogs, are only partially effective and new treatment methods remain an important objective. Harnessing the RNA interference (RNAi) pathway to achieve post-transcriptional silencing of rogue genetic elements is an exciting avenue for development of novel therapeutic strategies. The specific and potent suppression of HBV gene expression and replication is an attractive option as a novel and effective approach for the treatment of chronic HBV infection. However, despite significant and rapid progress, existing RNAi technologies require further refinement before clinical applications can be realized. Here, we review current efforts aimed at improving the efficiency of anti-HBV RNAi-based delivery systems, at limiting the toxicities associated with RNAi modalities and at preventing reactivation of viral replication. We discuss the progress towards clinical implementation of anti-HBV RNAi therapies.

Nuclear HBx binds the HBV minichromosome and modifies the epigenetic regulation of cccDNA function

HBV cccDNA, the template for transcription of all viral mRNAs, accumulates in the nucleus of infected cells as a stable episome organized into minichromosomes by histones and non-histone viral and cellular proteins. Using a cccDNA-specific chromatin immunoprecipitation (ChIP)-based quantitative assay, we have previously shown that transcription of the HBV minichromosome is regulated by epigenetic changes of cccDNA-bound histones and that modulation of the acetylation status of cccDNA-bound H3/H4 histones impacts on HBV replication. We now show that the cellular histone acetyltransferases CBP, p300, and PCAF/GCN5, and the histone deacetylases HDAC1 and hSirt1 are all recruited in vivo onto the cccDNA. We also found that the HBx regulatory protein produced in HBV replicating cells is recruited onto the cccDNA minichromosome, and the kinetics of HBx recruitment on the cccDNA parallels the HBV replication. As expected, an HBV mutant that does not express HBx is impaired in its replication, and exogenously expressed HBx transcomplements the replication defects. p300 recruitment is severely impaired, and cccDNA-bound histones are rapidly hypoacetylated in cells replicating the HBx mutant, whereas the recruitment of the histone deacetylases hSirt1 and HDAC1 is increased and occurs at earlier times. Finally, HBx mutant cccDNA transcribes significantly less pgRNA. Altogether our results further support the existence of a complex network of epigenetic events that influence cccDNA function and HBV replication and identify an epigenetic mechanism (i.e., to prevent cccDNA deacetylation) by which HBx controls HBV replication.

HBX-mediated migration of HBV-replicating HepG2 cells: insights on development of hepatocellular carcinoma

Hepatitus B virus (HBV) is a major cause of the development of hepatpcellular carcinoma (HCC). One of the significant characteristics of tumor progression is cell migration which is reflective of cytoskeletal dynamics. The Rho GTPases contribute to a multiple cellular processes, including the cellular cytoskeletal reorganization and motility. It has been found that some Rho GTPases have oncogenic activity and can promote cancer cell invasion. Here we discuss one of the Rho GTPases, Rac1 can be activated by HBV replication and such activation results in the high motility of HBV-replicating cells. The enhanced cell motility can be interestingly alleviated by the mutation at the sites of proline rich domain located in HBX. Our findings may provide new insights on the mechanism of HCC development associated with chronic HBV infection.

A pre-S gene chip to detect pre-S deletions in hepatitis B virus large surface antigen as a predictive marker for hepatoma risk in chronic hepatitis B virus carriers

BACKGROUND

Chronic hepatitis B virus (HBV) infection is an important cause of hepatocellular carcinoma (HCC) worldwide. The pre-S1 and -S2 mutant large HBV surface antigen (LHBS), in which the pre-S1 and -S2 regions of the LHBS gene are partially deleted, are highly associated with HBV-related HCC.

METHODS

The pre-S region of the LHBS gene in two hundred and one HBV-positive serum samples was PCR-amplified and sequenced. A pre-S oligonucleotide gene chip was developed to efficiently detect pre-S deletions in chronic HBV carriers. Twenty serum samples from chronic HBV carriers were analyzed using the chip.

RESULTS

The pre-S deletion rates were relatively low (7%) in the sera of patients with acute HBV infection. They gradually increased in periods of persistent HBV infection: pre-S mutation rates were 37% in chronic HBV carriers, and as high as 60% in HCC patients. The Pre-S Gene Chip offers a highly sensitive and specific method for pre-S deletion detection and is less expensive and more efficient (turnaround time 3 days) than DNA sequencing analysis.

CONCLUSION

The pre-S1/2 mutants may emerge during the long-term persistence of the HBV genome in carriers and facilitate HCC development. Combined detection of pre-S mutations, other markers of HBV replication, and viral titers, offers a reliable predictive method for HCC risks in chronic HBV carriers.

Role of hepatitis B surface antigen in the development of hepatocellular carcinoma: regulation of lymphoid enhancer-binding factor 1

Background

There are around 350 million of hepatitis B surface antigen (HBsAg) carriers worldwide, and among them, high risk of developing hepatocellular carcinoma (HCC) has been identified by epidemiological studies. To date, the molecular role of HBsAg in HCC development has not been fully studied. We have previously reported that in cell cultures, HBsAg up-regulated the expression of lymphoid enhancer-binding factor 1 (LEF-1), a key component of the Wnt pathway. In this study we aimed to study this effect of HBsAg on LEF-1 in the development of HCC.

Methods

Expression of HBsAg, LEF-1 and its downstream effector genes were compared among 30 HCCs, their peritumor tissue counterparts and 9 normal control liver tissues by quantitative real-time PCR. In addition, immunohistochemical staining studies on HBsAg and LEF-1 expression were conducted among these samples.

Results

The expression of LEF-1 was compared between 13 HBsAg positive HCC tissues and 17 HBsAg negative HCC tissues. Simultaneous detection of LEF-1 and HBsAg was observed in HBsAg positive HCC tissues and, additionally, the simultaneous detection of HBsAg and LEF-1 was more pronounced in peritumor tissues, compared to that in the tumor tissues. The distribution of cellular LEF-1 in peritumor tissues was predominantly in the cytoplasm; while LEF-1 in the tumor tissues was located either exclusively in the nucleus or both in the nucleus and cytoplasm. By real-time PCR, the expression levels of LEF-1 downstream effector genes cyclin D1 and c-myc were higher in peritumor cells compared to that of the tumor cells. However, a 38 kDa truncated isoform of LEF-1, rather than the 55 kDa wild-type LEF-1, was significantly elevated in the HBsAg positive tumor cells.

Conclusion

Data indicate that deregulation of the Wnt pathway by HBsAg occurred in HBV-associated HCCs, but was more pronounced in the peritumor cells. It is speculated that HBsAg could stimulate proliferation and functional modification of hepatocytes via LEF-1 through the Wnt pathway at the pre-malignant stage.

Prospective evaluation of hepatitis B 1762(T)/1764(A) mutations on hepatocellular carcinoma development in Shanghai, China

Chronic infection with the hepatitis B virus (HBV) is the most important risk factor for hepatocellular carcinoma (HCC). However, determinants of HCC risk in infected individuals are not well understood. We prospectively evaluated the association between acquired HBV 1762(T)/1764(A) double mutations and HCC risk among 49 incident HCC cases and 97 controls with seropositive hepatitis B surface antigen at baseline from a cohort of 18,244 men in Shanghai, China, enrolled during 1986 to 1989. Compared with HBV carriers without the mutations, chronic HBV carriers with the HBV 1762(T)/1764(A) double mutations experienced an elevated risk of HCC (odds ratio, 2.47; 95% confidence interval, 1.04-5.85; P = 0.04). Risk increased with increasing copies of the double mutations; men with > or =500 copies/microL serum had an odds ratio of 14.57 (95% confidence interval, 2.41-87.98) relative to those without the double mutations (P(trend) = 0.004). Thus, the HBV 1762(T)/1764(A) double mutation is a codeterminant of HCC risk for people chronically infected with HBV.

Rapid and sensitive detection of hepatitis B virus 1762T/1764A double mutation from hepatocellular carcinomas using LNA-mediated PCR clamping and hybridization probes

The 1762T/1764A double mutation of the hepatitis B virus (HBV) basal core promoter has been suggested to be a potential biomarker for hepatocellular carcinoma (HCC) among individuals with chronic HBV infection. In this study, a real-time PCR assay is established using the hybridization probes and an oligonucleotide clamp containing locked nucleic acids (LNAs). The LNA-containing oligonucleotide clamp specific for the wild type HBV is able to suppress the amplification of the wild type HBV templates. In addition, the clamp can inhibit the binding of the WT templates to the fluorescence probes thereby suppress the wild type HBV signals during the melting curve analyses. These effects facilitated the detection of HBV double mutation in the presence of 3000-fold excess of the wild type genome. Thus PCR amplification coupled with the melting curve analyses provides a quick, simple, and highly sensitive tool for the detection of this HBV double mutation.

Lectin of Concanavalin A as an anti-hepatoma therapeutic agent

Liver cancer is the predominant cause of cancer mortality in males of Southern China and Taiwan. The current therapy is not satisfactory, and more effective treatments are needed. In the search for new therapies for liver tumor, we found that Concanavalin A (Con A), a lectin from Jack bean seeds, can have a potent anti-hepatoma effect. Con A after binding to the mannose moiety on the cell membrane glycoprotein is internalized preferentially to the mitochondria. An autophagy is triggered which leads to cell death. Con A as a T cell mitogen subsequently activates the immune response in the liver and results in the eradication of the tumor in a murine in situ hepatoma model. The liver tumor nodule formation is inhibited by the CD8⁺ T cells, and a tumor antigen-specific immune memory is established during the hepatic inflammation. The dual properties (autophagic cytotoxicity and immunomodulation) via the specific carbohydrate binding let Con A exert a potent anti-hepatoma therapeutic effect. The novel mechanism of the Con A anti-hepatoma effect is discussed. The prototype of Con with an anti-hepatoma activity gives support to the search for other natural lectins as anti-cancer compounds.

Harnessing the RNA interference pathway to advance treatment and prevention of hepatocellular carcinoma

Primary liver cancer is the fifth most common malignancy in the world and is a leading cause of cancer-related mortality. Available treatment for hepatocellular carcinoma (HCC), the commonest primary liver cancer, is rarely curative and there is a need to develop therapy that is more effective. Specific and powerful gene silencing that can be achieved by activating RNA interference (RNAi) has generated enthusiasm for exploiting this pathway for HCC therapy. Many studies have been carried out with the aim of silencing HCC-related cellular oncogenes or the hepatocarcinogenic hepatitis B virus (HBV) and hepatitis C virus (HCV). Proof of principle studies have demonstrated promising results, and an early clinical trial assessing RNAi-based HBV therapy is currently in progress. Although the data augur well, there are several significant hurdles that need to be overcome before the goal of RNAi-based therapy for HCC is realized. Particularly important are the efficient and safe delivery of RNAi effecters to target malignant tissue and the limitation of unintended harmful non-specific effects.

The new core promoter element XCPE1 (X Core Promoter Element 1) directs activator-, mediator-, and TATA-binding protein-dependent but TFIID-independent RNA polymerase II transcription from TATA-less promoters

The core promoter is a critical DNA element required for accurate transcription and regulation of transcription. Several core promoter elements have been previously identified in eukaryotes, but those cannot account for transcription from most RNA polymerase II-transcribed genes. Additional, as-yet-unidentified core promoter elements must be present in eukaryotic genomes. From extensive analyses of the hepatitis B virus X gene promoter, here we identify a new core promoter element, XCPE1 (the X gene core promoter element 1), that drives RNA polymerase II transcription. XCPE1 is located between nucleotides -8 and +2 relative to the transcriptional start site (+1) and has a consensus sequence of G/A/T-G/C-G-T/C-G-G-G/A-A-G/C(+1)-A/C. XCPE1 shows fairly weak transcriptional activity alone but exerts significant, specific promoter activity when accompanied by activator-binding sites. XCPE1 is also found in the core promoter regions of about 1% of human genes, particularly in poorly characterized TATA-less genes. Our in vitro transcription studies suggest that the XCPE1-driven transcription can be highly active in the absence of TFIID because it can utilize either free TBP or the complete TFIID complex. Our findings suggest the possibility of the existence of a TAF1 (TFIID)-independent transcriptional initiation mechanism that may be used by a category of TATA-less promoters in higher eukaryotes.

Hepatitis B genotypes: relation to clinical outcome in patients with chronic hepatitis B in Saudi Arabia

AIM

To identify the most common hepatitis B virus (HBV) genotype in Saudi Arabia, and correlate the prevailing genotypes with the clinical outcome of patients.

METHODS

Patients were consecutively recruited from the hepatology clinics of two tertiary care referral centers. Patients were categorized into 4 different groups: group 1, patients with hepatitis B and normal liver enzymes; group 2, patients with hepatitis B and abnormal liver enzymes but without cirrhosis; group 3, patients with hepatitis B and liver cirrhosis; group 4, patients with hepatitis B and hepatocellular carcinoma. All patients had a positive hepatitis B surface antigen (HBsAg). Genotyping of HBV was performed by nested PCR-mediated amplification of the target sequence and hybridization with sequence-specific oligonucleotides.

RESULTS

Seventy patients were enrolled in this study. They were predominantly male (72.9%) in their mid-forty's (mean age 47 years). Forty-nine (70%) patients were hepatitis B envelope antigen (HBeAg) negative. The majority of patients (64%) acquired HBV through unknown risk factors. Hepatitis B genotyping revealed that 57 patients (81.4%) were genotype D, 1 patient (1.4%) had genotype A, 1 patient (1.4%) had genotype C, and 4 patients (5.7%) had genotype E, while 7 patients (10%) had mixed genotype (4 patients ADG, 1 patient DE, 1 patient DF, and 1 patient ADFG). Based on univariate analysis of genotype D patients, significant predictors of advanced liver disease were age, gender, aspartate transaminase, alanine transaminase, albumin, bilirubin, and alkaline phosphatase (all P < 0.001). In multivariate analysis decreased hemoglobin (r = -0.05; 95% CI: -0.08 to -0.03; P = 0.001) and albumin levels (r = -0.004; 95% CI: -0.007 to -0.001; P = 0.002) were highly significant predictors of advanced liver disease. In patients with HBV genotype D, HBeAg negativity was found to increase across advancing stages of liver disease (P = 0.024).

CONCLUSION

This study highlights that the vast majority of Saudi patients with chronic hepatitis B have genotype D. No correlation could be observed between the different genotypes and epidemiological or clinical factors. The relationship between genotype D and HBeAg status in terms of disease severity needs to be further elucidated in larger longitudinal studies.

Toll-like receptor 4 plays an anti-HBV role in a murine model of acute hepatitis B virus expression

AIM

Toll-like receptor 4 (TLR4) has been shown to be important for bacterial infection, especially to lipopolysaccharide signaling. Its possible role in HBV infection is studied in the present study.

MATERIALS AND METHODS

pHBV3.6 plasmid, containing full-length HBV genome was used in the murine model of acute HBV expression by hydrodynamics in vivo transfection. TLR4 normal or mutant mouse strain was compared to investigate the possible role of TLR4 in acute HBV expression.

RESULTS

After pHBV3.6 injection, the infiltrating leukocytes expressed TLR4 were observed nearby the HBsAg-expressing hepatocytes. The HBV antigenemia as well as the replication and transcription were higher in TLR4-mutant C3H/HeJ mice than in normal C3H/HeN mice. The HBV-specific immune responses were impaired in the liver or spleen of the C3H/HeJ mice. Their inducible nitric oxide synthase (iNOS) expression on the hepatic infiltrating cells was also impaired. When adoptively transferring splenocytes from C3H/HeN mice to C3H/HeJ mice, the HBV replication was inhibited to the level as that of C3H/HeN.

CONCLUSION

These results suggest that TLR4 plays an anti-HBV role in vivo through the induction of iNOS expression and HBV-specific immune responses after HBV expression.

Upregulation of human telomerase reverse transcriptase mRNA expression by in vitro transfection of hepatitis B virus X gene into human hepatocarcinoma and cholangiocarcinoma cells

AIM: To study the changes of human telomerase reverse transcriptase (hTERT) mRNA expression in human hepatocarcinoma cell lines (HepG2) and cholangiocarcinoma cell lines (QBC939) after HBx gene transfection and to illustrate the significance of transcriptional regulation of hTERT gene by HBx gene in the carcinogenesis.

METHODS: HepG2 and QBC939 cell lines were cultured and co-transfected with eukaryotic expression vector containing the HBx coding region and cloning vector containing enhanced green fluorescent protein (EGFP) coding sequence using lipid-mediated gene transduction technique. Thirty-six hours after transfection, EGFP expression in cells was used as the indicator of successful transfection. Flow cytometry was performed to determine the transfection efficiency. Cells were harvested and total RNA was extracted using TRIzol^® reagent. The expression of hTERT mRNA in HepG2 and QBC939 cell lines was assayed by reverse transcription-polymerase chain reaction. The expression of HBx protein in both cell lines was detected by immunocytochemical staining and Western blotting.

RESULTS: Flow cytometry showed that the transfection efficiency was 46.4% in HepG2 cells and 29.6% in QBC939 cells for both HBx gene expression vector and blank vector. The expression of hTERT mRNA was meaningfully increased in HepG2 and QBC939 cell lines when transfected with HBx gene expression vector compared to those transfected with OPTI-MEM medium and blank vector. Immunocytochemical staining and Western blotting revealed HBx protein expression in HepG2 and QBC939 cells only when transfected with HBx gene.

CONCLUSION: HBx gene transfection can upregulate the transcriptional expression of hTERT mRNA. The transactiv-ation of hTERT gene by HBx gene is a newfound mechanism for pathogenesis of hepatocarcinomas and cholangioca-rcinomas after HBV infection.

The transcriptional transactivation function of HBx protein is important for its augmentation role in hepatitis B virus replication

The role and functional domain of hepatitis B virus (HBV) X protein (HBx) in regulating HBV transcription and replication were investigated with a transient transfection system in the human hepatoma cell line HepG2 using wild-type or HBx-minus HBV genome constructs and a series of deletion or mutation HBx expression plasmids. We show here that HBx has augmentation effects on HBV transcription and replication as a HBV mutant genome with defective X gene led to decreased levels of 3.5-kb HBV RNA and HBV replication intermediates and that these decreases can be restored by either transient ectopic expression of HBx or a stable HBx expression cell line. The C-terminal two-thirds (amino acids [aa] 51 to 154), which contain the transactivation domain, is required for this function of HBx; the N-terminal one-third (aa 1 to 50) is not required. Using the alanine scanning mutagenesis strategy, we demonstrated that the regions between aa 52 to 65 and 88 to 154 are important for the augmentation function of HBx in HBV replication. By the luciferase reporter gene analysis, we found that the transactivation and coactivation activities of HBx coincide well with its augmentation function in HBV transcription and replication. These results suggest that HBx has an important role in stimulating HBV transcription and replication and that the transcriptional transactivation function of HBx may be critical for its augmentation effect on HBV replication.

Specific mutations of hepatitis B virus in plasma predict liver cancer development

A major risk factor for hepatocellular carcinoma (HCC) is hepatitis B virus (HBV), whose pathogenesis is exacerbated by the acquisition of mutations that accelerate carcinogenesis. We examined, with mass spectrometry, the temporality of an HBV 1762(T)/1764(A) double mutation in plasma and tumors. Initial studies found that 52 of 70 (74.3%) tumors from patients residing in Qidong, People's Republic of China, contained this HBV mutation. Paired plasma samples were available for six of the tumor specimens; four tumors had the HBV 1762(T)/1764(A) mutation, whereas three of the paired plasma samples were also positive. The potential predictive value of this biomarker was explored by using stored plasma samples from a study of 120 residents of Qidong who had been monitored for aflatoxin exposure and HBV infection. After 10 years of passive follow-up, there were six cases of major liver disease including HCC (four cases), hepatitis (one case), and cirrhosis (one case). All six cases had detectable levels of the HBV 1762(T)/1764(A) mutation up to 8 years before diagnosis. Finally, 15 liver cancers were selected from a prospective cohort of 1,638 high-risk individuals in Qidong on the basis of available plasma samples spanning the years before and after diagnosis. The HBV 1762(T)/1764(A) mutation was detected in 8 of the 15 cases (53.3%) before cancer. The persistence of detection of this mutation was statistically significant (P = 0.022, two-tailed). We therefore found that a prediagnosis biomarker of specific HBV mutations can be measured in plasma and suggest this marker for use as an intermediate endpoint in prevention and intervention trials.

Anti-HBV effect of TAT- HBV targeted ribonuclease

AIM: To prepare and purify TAT-HBV targeted ribonuclease fusion protein, evaluate its transduction activity and investigate its effect on HBV replication in 2.2.15 cells.

METHODS: The prokaryotic expression vector pTAT containing TR gene was used in transforming E.coli BL21 (DE3) LysS and TR was expressed with the induction of IPTG. The TAT-TR fusion protein was purified using Ni-NTA-agrose and PD-10 desalting columns, and analyzed by SDS-PAGE. Transduction efficiency of TAT-TR was detected with immunofluorescence assay and the concentration of HBeAg in the supernatant of the 2.2.15 cells was determined via solid-phase radioimmunoassay (spRIA). MTT assay was used to detect the cytotoxicity of TAT-TR.

RESULTS: The SDS-PAGE showed that the TAT-TR fusion protein was purified successfully, and the purity of TAT-TR was 90%. The visualization of TAT-TR by immunofluorescence assay indicated its high efficiency in transducing 2.2.15 cells. RIA result suggests that TAT-TR could inhibit the replication of HBV effectively, it didn’t affect cell growth and had no cytotoxicity.

CONCLUSION: TAT-TR possesses a significant anti-HBV activity and the preparation of TAT-TR fusion protein has laid the foundation for the use of TR in the therapeutic trial of HBV infection.

Hepatitis B virus core protein stimulates the proteasome-mediated degradation of viral X protein

Hepatitis B virus (HBV) X protein (HBx) plays an essential role in viral replication and in the development of hepatocellular carcinoma. HBx has the ability to transactivate the expression of all HBV proteins, including the viral core protein HBc. Consistent with its regulatory role, HBx is relatively unstable and is present at low levels in the cell. We report here that the level of HBx was significantly reduced by the coexpression of HBc in cultured human hepatoma cells, whereas the level of HBx mRNA was unaffected. The repression of HBx by HBc was relieved by treating cells with the proteasome inhibitor MG132, indicating that HBc acts by stimulating the proteasome-mediated degradation of HBx. Moreover, the inhibitory effect of HBc was specific to HBx and did not affect other proteins, including p53, a known target of the proteasome. Although no direct physical interaction between HBc and HBx could be demonstrated, mutational analysis indicated that the C-terminal half of HBc is responsible for its inhibitory effect. These results suggest that HBc functions as a novel regulator of the HBV life cycle and of hepatocellular carcinogenesis through control of the HBx level via an inhibitory feedback type of mechanism.

Expression of hepatitis B virus X protein in transgenic mice

AIM: To establish a mice model harboring hepatitis B virus x gene (adr subtype) for studying the function of hepatitis B virus X protein, a transactivator of viral and cellular promoter/enhancer elements.

METHODS: Expression vector pcDNA3-HBx, containing CMV promoter and hepatitis B virus x gene open reading fragment, was constructed by recombination DNA technique. Hela cells were cultured in DMEM and transfected with pcDNA3-HBx or control pcDNA3 plasmids using FuGENE6 Transfection Reagent. Expression of pcDNA3-HBx vectors in the transfected Hela cells was confirmed by Western blotting. After restriction endonuclease digestion, the coding elements were microinjected into male pronuclei of mice zygotes. The pups were evaluated by multiplex polymerase chain reaction (PCR) at genomic DNA level. The x gene transgenic mice founders were confirmed at protein level by Western blotting, immunohistochemistry and immunogold transmission electron microscopy.

RESULTS: Expression vector pcDNA3-HBx was constructed by recombination DNA technique and identified right by restriction endonuclease digestion and DNA direct sequencing. With Western blotting, hepatitis X protein was detected in Hela cells transfected with pcDNA3-HBx plasmids, suggesting pcDNA3-HBx plasmids could express in eukaryotic cells. Following microinjection of coding sequence of pcDNA3-HBx, the embryos were transferred to oviducts of psedopregnant females. Four pups were born and survived. Two of them were verified to have the HBx gene integrated in their genomic DNA by multiplex PCR assay, and named C57-TgN (HBx)S MMU1 and C57-TgN (HB x) SMMU3 respectively. They expressed 17KD X protein in liver tissue by Western blotting assay. With the immunohistochemistry, X protein was detected mainly in hepatocytes cytoplasm of transgenic mice, which was furthermore confirmed by immunogold transmission electon microscopy.

CONCLUSION: We have constructed the expression vector pcDNA3-HBx that can be used to study the function of HBx gene in eukaryotic cells in vitro. We also established HBx gene (adr subtype) transgenic mice named C57-TgN (HBx) SMMU harboring HBx gene in their genome and express X protein in hepatocytes, Which might be a valuable animal system for studying the roles of HBx gene in hepatitis B virus life cycle and development of hepatocellular carcinoma in vivo.

p73β inhibits transcriptional activities of enhancer I and X promoter in hepatitis B virus more efficiently than p73α

AIM: p73, as a novel member of a family of p53-related transcription factors, shares redundant functions with p53, such as the abilities of inducing apoptosis and suppressing growth. It is well known that p53 can repress HBV expression and transcription efficiently. The aim of this paper is to investigate the transcriptional effect of p73α and p73β on hepatitis B virus (HBV) and to understand the correlation between HBV and p73.

METHODS: To construct an x-gene inactivated HBV plasmid which was cotransfected with p73α or p73β expression vectors into HepG2 cells. After transiently transfection, HBV surface antigen (HBsAg) and HBV e antigen (HBeAg) were detected by ELISA. Viral transcripts synthesized by HBV were evaluated by Northern blotting analysis. The activities of HBV regulatory elements, including enhancer I/X promoter (ENI/Xp) and enhancer II/core promoter (ENII/Cp) were monitored by luciferase assays.

RESULTS: Both p73α and p73β could repress HBsAg and HBeAg expression by downregulating the ENI/Xp and ENII/ Cp activities. But p73β exerted stronger inhibition on the activity of ENI/Xp than p73α, resulting in much lower level of viral transcripts and the antigens expression.

CONCLUSION: p73β as a novel member of p53 family can efficiently inhibit HBV transcription mainly through downregulating the activities of the HBV ENI/Xp regulatory elements.

Hepatitis Bx antigen stimulates expression of a novel cellular gene, URG4, that promotes hepatocellular growth and survival

Hepatitis B virus encoded X antigen (HBxAg) may contribute to the development of hepatocellular carcinoma (HCC) by up- or downregulating the expression of cellular genes that promote cell growth and survival. To test this hypothesis, HBxAg-positive and -negative HepG2 cells were constructed, and the patterns of cellular gene expression compared by polymerase chain reaction select cDNA subtraction. The full-length clone of one of these upregulated genes (URG), URG4, encoded a protein of about 104 kDa. URG4 was strongly expressed in hepatitis B-infected liver and in HCC cells, where it costained with HBxAg, and was weakly expressed in uninfected liver, suggesting URG4 was an effector of HBxAg in vivo. Overexpression of URG4 in HepG2 cells promoted hepatocellular growth and survival in tissue culture and in soft agar, and accelerated tumor development in nude mice. Hence, URG4 may be a natural effector of HBxAg that contributes importantly to multistep hepatocarcinogenesis.

Turnover of hepatitis B virus X protein is regulated by damaged DNA-binding complex

Mammalian hepatitis B viruses encode an essential regulatory protein, termed X, which may also be implicated in liver cancer development associated with chronic infection. X protein, also referred to as HBx in human virus and WHx in woodchuck virus, has been reported to bind to a number of cellular proteins, including the DDB1 subunit of the damaged DNA-binding (DDB) complex. Our previous work provided genetic evidence for the importance of WHx-DDB1 interaction in both the activity of the X protein and establishment of viral infection in woodchucks. In the present study, a direct action of DDB1 on the X protein is documented. Physical interaction between the two proteins leads to an increase in X protein stability. This effect results from protection of the viral protein from proteasome-mediated degradation. Protection of WHx is overcome in the presence DDB2, the second subunit of the DDB heterodimer. In keeping with observations reported for HBx, DDB2 was found to directly bind to WHx. Nonetheless, the counteracting effect of DDB2 on X stabilization requires DDB2-DDB1 interaction. Taken together, these findings substantiate the physical and functional connection between the X protein and the DDB1-DDB2 heterodimer, leading to the regulation of the pool of the viral protein.

Applying a highly specific and reproducible cDNA RDA method to clone garlic up-regulated genes in human gastric cancer cells

AIM: To develop and optimize cDNA representational difference analysis (cDNA RDA) method and to identify and clone garlic up-regulated genes in human gastric cancer (HGC) cells.

METHODS: We performed cDNA RDA method by using abundant double-stranded cDNA messages provided by two self-constructed cDNA libraries (Allitridi-treated and paternal HGC cell line BGC823 cells cDNA libraries respectively). BamH I and Xho I restriction sites harbored in the library vector were used to select representations. Northern and Slot blots analyses were employed to identify the obtained difference products.

RESULTS: Fragments released from the cDNA library vector after restriction endonuclease digestion acted as good marker indicating the appropriate digestion degree for library DNA. Two novel expressed sequence tags (ESTs) and a recombinant gene were obtained. Slot blots result showed a 8-fold increase of glia-derived nexin/protease nexin 1 (GDN/PN1) gene expression level and 4-fold increase of hepatitis B virus x-interacting protein (XIP) mRNA level in BGC823 cells after Allitridi treatment for 72 h.

CONCLUSION: Elevated levels of GDN/PN1 and XIP mRNAs induced by Allitridi provide valuable molecular evidence for elucidating the garlic's efficacies against neurodegenerative and inflammatory diseases. Isolation of a recombinant gene and two novel ESTs further show cDNA RDA based on cDNA libraries to be a powerful method with high specificity and reproducibility in cloning differentially expressed genes.

Anti-HBV hairpin ribozyme-mediated cleavage of target RNA in vitro

AIM: To study the preparation and cleavage activity of HpRz directed against the transcript of HBV core gene in vitro.

METHODS: HpRz gene designed by computer targeting the transcript of HBV core gene was cloned into the vector p1.5 between 5’-cis-Rz and 3’-cis-Rz. ³²p-labeled HpRz transcript proved whether the vector fit for the preparation of hairpin ribozyme in vitro. ³²p-labeled pKC transcript containing HBV core region as target-RNA was transcribed using T₇ RNA polymerase and purified by denaturing PAGE. Cold HpRz transcript was incubated with ³²p-labeled target-RNAs under different conditions and radio autographed after denaturing polyacrylamide gel electrophoresis.

RESULTS: HpRz has the specific ability of cleavage of target RNA at 37 °C and 12 mM MgCl₂. K_m = 26.31 nmol/L, K_cat = 0.18/min. These results revealed that the design of HpRz was correct.

CONCLUSION: HpRz prepared in this study possesses specific catalytic activity from the identification of cleavage activity. These results indicate that hairpin ribozyme may intracellularly inhibit the replication of HBV, therefore it may become a novel potent weapon for the treatment of hepatitis B.