Molecular mechanisms of hepatitis B virus-associated liver cancer

Hepatitis B virus X protein upregulates DNA methyltransferase 3A/3B and enhances SOCS-1CpG island methylation

The aim of the present study was to investigate the effect of hepatitis B virus X protein (HBx) on the expression of DNA methyltransferase (DNMT)3A/3B and suppressors of cytokine signaling‑1 (SOCS‑1), as well as promoter CpG island methylation of the SOCS‑1 gene. Stable hepatocyte cell lines expressing the HBx gene (pcDNA‑X/QSG7701) or an empty gene (pcDNA3.0/QSG7701) were established. Reverse transcription quantitative polymerase chain reaction (PCR) was used to detect the mRNA expression levels of DNMT3A/3B and SOCS‑1. Immunohistochemistry was used to detect the protein expression of DNMT3A/3B. Methylation‑specific PCR (MSP) was used to detect the methylation status of the SOCS‑1 gene promoter. The mRNA and protein expression levels of DNMT3A/3B were significantly higher in the pcDNA‑X/QSG7701‑transfected cells, compared with those in the pcDNA3.0/QSG7701 or non‑transfected QSG7701 cells (P<0.05), whereas the relative mRNA expression of SOCS‑1 was significantly lower in the pcDNA‑X/QSG7701 cells compared with the pcDNA3.0/QSG7701 and non‑transfected QSG7701 cells (F=19.6; P<0.05). Western blot analysis showed that the protein expression of SOCS‑1 was significantly lower in the pcDNA‑X/QSG7701 cells, compared with the pcDNA3.0/QSG7701 or non‑transfected QSG7701 cells (F=19.4; P<0.05). The results of the MSP analysis showed that SOCS‑1 promoter region methylation was present only in the pcDNA‑X/QSG7701 cells. The HBV‑X gene upregulated the mRNA and protein expression levels of DNMT3A/3B, downregulated the expression of SOCS‑1 and increased SOCS‑1 gene promoter CpG island methylation. This may provide a potential explanation of the mechanism underlying HBx-associated hepatocellular carcinoma.

Inhibition of hepatitis B virus cccDNA by siRNA in transgenic mice

The elimination of viral covalently closed circular DNA (cccDNA) from the nucleus of infected hepatocytes is an obstacle to achieving sustained viral clearance during antiviral therapy of chronic hepatitis B virus (HBV) infection. The aim of our study was to determine whether treatment with siRNA is able to suppress viral cccDNA amplification using a HBV-transgenic mice model. The experimental results revealed that siRNAs can serve as efficient alternative anti-HBV agents, because they showed better inhibitory effect on viral replication and antigen expression in transgenic mice. More importantly, the siRNA markedly inhibited HBV cccDNA amplification.

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.

Tumor initiation and progression in hepatocellular carcinoma: risk factors, classification, and therapeutic targets

Hepatocellular carcinoma (HCC) is a major health problem worldwide responsible for 500 000 deaths annually. A number of risk factors are associated with either the induction of the disease or its progression; these include infection with hepatitis B or C virus, alcohol consumption, non-alcoholic steatohepatitis and certain congenital disorders. In around 80% of the cases, HCC is associated with cirrhosis or advanced fibrosis and with inflammation and oxidative stress. In this review we focus firstly on the different risk factors for HCC and summarize the mechanisms by which each is considered to contribute to HCC. In the second part we look at the molecular processes involved in cancer progression. HCC development is recognized as a multistep process that normally develops over many years. Over this period several mutations accumulate in the cell and that stimulate malign transformation, growth, and metastatic behavior. Over the recent years it has become evident that not only the tumor cell itself but also the tumor microenviroment plays a major role in the development of a tumor. There is a direct link between the role of inflammation and cirrhosis with this microenviroment. Both in vitro and in vivo it has been shown that tumor formation and metastatic properties are linked to epithelial-mesenchymal transition (EMT), a process by which facillitates the tumor cell's attempts to migrate to a more favourable microenviroment. Several groups have analyzed the gene expression in HCC and its surrounding tissue by microarray and this has resulted in the molecular classification into a distinct number of classes. Here we also found a role for hypoxia induced gene expression leading to a clinically more aggressive gene expression in HCC. Molecular analysis also helped to identify important cellular pathways and possible therapeutic targets. The first molecule that in this way has shown clinical application for liver cancer is the multikinase inhibitor sorafenib, others are currently in different stages of clinical studies like the mTOR inhibitor everolimus.

Persistent viral infection elevates central nervous system MHC class I through chronic production of interferons

Persistence of even the stealthiest viruses can perturb immune function either to the benefit or detriment of the host. Lymphocytic choriomeningitis virus (LCMV) establishes lifelong, systemic persistence when introduced in utero or at birth. Despite a highly evolved host-pathogen relationship, LCMV cannot escape detection by the innate immune system, which results in chronic stimulation of the type 1 IFN pathway in adult carrier mice. In this study we demonstrate that IFN-beta is chronically up-regulated in peripheral lymphoid and nonlymphoid tissues (but not the CNS) of mice persistently infected from birth with LCMV and that dendritic cells (DCs) represent at least one source of IFN-beta. Interestingly, chronic stimulation of this innate pathway significantly elevated MHC class I expression in the CNS as well as the periphery. Elevated MHC I expression was dependent on IFN-alphabeta receptor but not MyD88-dependent signaling, as only genetic deletion of the former reduced MHC I to normal levels. An increase in circulating virus was also observed in the IFN-alphabeta receptor deficient carrier mice, signifying that type I IFN continually exerts anti-viral pressure during a LCMV carrier state. Finally, to determine whether heightened CNS MHC I could be therapeutically corrected, we purged LCMV carrier mice of their persistent infection using adoptive immunotherapy. This treatment significantly reduced CNS MHC I expression. Collectively, these data demonstrate that even a well adapted pathogen can chronically stimulate the innate immune system and consequently alter the expression of Ag presenting machinery in an immunologically specialized compartment like the CNS.

Suppression of hepatitis B virus-derived human hepatocellular carcinoma by NF-kappaB-inducing kinase-specific siRNA using liver-targeting liposomes

Hepatitis B virus triggers an increase of NF-kappaB inducing kinase (NIK)-dependent NF-kappaB activation, followed by the promotion of hepatocellular carcinoma (HCC). Here, we examined the inhibitory effect of NIK-specific siRNA on NF-kappaB signaling and HCC. The results of this study indicated that these siRNAs suppressed HBV-derived HCC by regulating NIK activation. To exert a protective effect from degradation enzyme, cationic liposomes were contrived and modified to contain beta-sitosterol glucoside to target the asialoglycoprotein receptors in liver cancer cells. The cationic dimyristoyl diacyltrimethylammonium propane liposomes were prepared by a reverse-phase evaporation method with slight modification. beta-Sitosterol glucoside was added to the lipid mixture at the beginning of the liposome preparation for the purpose of liver targeting. These liposomes assisted the delivery of the siRNA to specific cells and protected it from various lyases, followed by the ultimate suppression of HCC.

The Molecular Diagnosis of Hepatitis B Virus-Associated Hepatocellular Carcinoma

Hepatitis B virus (HBV) infection is the major cause of hepatocellular carcinoma (HCC) worldwide. The pathogenesis of HBV-associated HCC has been studied extensively, and molecular changes during malignant transformation have been identified. It has been proposed that the insertion of HBV DNA into the human genome results in chromosomal instability and inactivation of tumor suppressor genes. Transactivation of oncogenes, inactivation of tumor suppressor genes, and alteration of the cell cycle by HBV proteins are also involved in the progression of hepatocellular carcinogenesis. Traditional clinical examinations of HCC, such as biopsy, computer tomography, ultrasonic imaging, and detection of such biomarkers as a-fetoprotein, are currently the "gold standard" in diagnosis. These tests diagnose HCC only in the late stages of disease. This limitation has greatly reduced the chance of survival of HCC patients. To resolve this problem, new biomarkers that can diagnose HCC in earlier stages are necessary. Based on recent molecular studies of the effects of HBV on cellular transformation, differentially expressed biomarkers of HBV infection have been elucidated. With the analyses of the HBV replication profile, the viral load (HBV DNA levels) of patients, and the viral protein expression, the severity of hepatitis in the preneoplastic stages can be assessed. In the future, with the molecular profiles identified by genomic and proteomic approaches, stage-specific biomarkers should be identified to monitor the progression and prognosis of HCC.

Increased plasma apoM levels in the patients suffered from hepatocellular carcinoma and other chronic liver diseases

OBJECTIVE

To determine plasma apolipoprotein M (apoM) levels and other lipid profiles in hepatocellular carcinoma (HCC) patients compared to other chronic liver diseases and normal subjects.

MATERIALS AND METHODS

36 HCC, 68 chronic hepatitis, 29 liver cirrhosis patients and 64 normal controls were subjected in the present study. Serum lipids, lipoproteins, apolipoprotein AI (apoAI) and apoB were determined by the conventional methods. Plasma apoM levels were semi-quantitatively determined by both dot-blotting and western blotting analysis.

RESULTS

Serum levels of triglycerides (TG), HDL-cholesterol, apoAI and lipoprotein (a) (Lp(a)) were significantly lower in the HCC patients than in the normal subjects, whereas there were no obvious differences on serum total cholesterol, LDL-cholesterol and apoB between HCC patients and normal subjects. However, plasma apoM levels in HCC patients were significantly increased than those in the normal subjects, but lower than those in the chronic hepatitis and cirrhosis patients.

CONCLUSION

It is concluded that serum TG, apoAI, HDL-C and Lp(a) were significantly decreased in HCC patients than in controls, whereas plasma apoM levels were significantly increased in the HCC patients. Decreased serum TG, apoAI, HDL-C and Lp(a) may reflect the liver damage in HCC patients, whereas the clinical significance of increased plasma apoM levels in relation to HCC is not clear.

Future of molecular profiling of human hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a fatal disease occurring worldwide and developing mainly in chronic liver diseased patients. Despite routine screening of individuals at high risk, most of the patients are diagnosed at late stages of HCC. In addition, the recurrence rate after surgical resection of small tumors is high. Molecular profiling, including expression analysis, comparative genomics and proteomics, provides powerful tools to gain insight into the molecular mechanisms underlying carcinogenesis. Advances in bioinformatics have also allowed for the evaluation of large data sets. Therefore, molecular profiling of HCC using a Biological Expression Network Discovery (BLEND) strategy that integrates global molecular profiling data, including mRNA, miRNA, DNA methylation and DNA copy numbers from both the tumor and the surrounding microenvironment, along with mechanistic studies, may improve the diagnosis, treatment and prognosis of HCC patients. Such an approach will provide mechanistic insight into the pathogenesis of HCC, potentially leading to personalized medicine and the identification of new therapeutic targets.

HBx or HCV core gene expression in HepG2 human liver cells results in a survival benefit against oxidative stress with possible implications for HCC development

Hepatitis virus replication in the liver is often accompanied by inflammation resulting in the formation of reactive oxygen species (ROS) and nitric oxide (NO) and these may induce cell death. We investigated whether the expression of HBx or HCV core protein in HepG2 cells has an influence on the sensitivity of these cells for oxidative radicals. Our previous study, using the inducible HBV model of HepAD38, revealed that oxidative-stress-related genes are upregulated by virus replication. In the present study, we examined the intracellular pro-oxidant status with dichlorofluorescein (DCF) in HepG2 cell lines transfected with HBx, HbsAg and HCV core. Baseline intracellular oxidative levels were not different in the cell lines expressing viral proteins as compared to control. However, when these cells were exposed to H(2)O(2), the viral protein expressing cells, especially those expressing HBx, showed a reduced level of ROS. This suggests that HBx and HCV core transfected cells can convert H(2)O(2) to less reactive compounds at a higher rate than the control cells. When HBx or HCV core expressing cells were exposed to peroxynitrite (a highly reactive product formed under physiological conditions through interaction of superoxide (O(2)(-)) with NO) these cells were less sensitive to induction of cell death. In addition, these cell lines were less prone to cell death when exposed to H(2)O(2) directly. In conclusion, HBx and HCV core expression in HepG2 cells leads to a survival benefit under oxidative stress which in vivo can be induced during inflammation.

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Hepatitis B virus replication causes oxidative stress in HepAD38 liver cells

We used human hepatoma HepAD38 cells, in which HBV production is under the control of a tetracycline-regulated promotor, to investigate changes induced in the host cell by HBV replication that could contribute to malignant transformation. Parameters of oxidative stress (malondialdehyde, glutathione) and cell proliferation were determined at different times after induction (0-96 h). In HBV-producing cells, the redox status peaked at 72 h. cDNA micro array analysis at 72 h post induction revealed 3 groups of genes that were up-regulated by HBV: (i) heat shock proteins, (ii) oxidative and metabolic stress and (iii) growth and apoptosis related genes. Continuous HBV production did not accelerate karyotypic changes in cells cultured for 4 months (18 passages).

IN CONCLUSION

HBV replication modulates host gene expression and induces oxidative stress. In this HepAD38 model early events (0-4 days) in the host cell after induction of HBV replication can be studied under strictly defined conditions.

Up-regulation of cyclin D1 by HBx is mediated by NF-kappaB2/BCL3 complex through kappaB site of cyclin D1 promoter

Cyclin D1 is frequently overexpressed in hepatocellular carcinoma (HCC) exhibiting increased malignant phenotypes. It has also been known that the hepatitis Bx (HBx) protein is strongly associated with HCC development and progression. Although overexpression of both proteins is related to HCC, the relationship between the two has not been well studied. Here we show that HBx up-regulates cyclin D1 and that this process is mediated by the NF-kappaB2(p52)/BCL-3 complex. Our experiments indicate that HBx up-regulates BCL-3 in the mRNA level, which subsequently results in the up-regulation of the NF-kappaB2(p52)/BCL-3 complex in the nucleus. Moreover, impaired HBx-mediated BCL-3 up-regulation by small interfering RNA for BCL-3 reduced HBx-mediated cyclin D1 up-regulation. Down-regulation of the HBx protein level by p53 also reduced HBx-mediated cyclin D1 up-regulation. From these results, we conclude that the up-regulation of cyclin D1 by HBx is mediated by the up-regulation of NF-kappaB2(p52)/BCL-3 in the nucleus. This HBx-mediated-cyclin D1 up-regulation might play an important role in the HBx-mediated HCC development and progression.

Influence of liver cancer on lipid and lipoprotein metabolism

Liver plays a key role in the metabolism of plasma apolipoproteins, endogenous lipids and lipoproteins. Hepatocellular carcinoma (HCC) is one of the most common fatal malignant tumors in China and in other Southeast Asian countries. This has been attributed to the high incidence of hepatitis B infection. Hepatitis B proteins, such as the hepatitis B X protein (HBx) that is large hepatitis B surface protein could regulate transcription of many candidate genes for liver carcinogenesis. It has known that patients who suffered from acute hepatitis B could have lipid disorders such as decreased plasma level of high-density lipoproteins (HDL). Furthermore, aberrations of lipid metabolism are often seen in the chronic hepatitis B infection. Plasma lipid profiles could be changed under HCC. In majority of the reports in HCC, plasma levels of triglycerides (TG), cholesterol, free fatty acids (FFA), HDL, low-density lipoproteins (LDL), lipoprotein (a) (Lp(a)), apolipoprotein AI (apoAI) and apoB were slight to significantly decreased, however, in some cases plasma levels of TG and Lp(a) might be increased. It has been suggested that analysis of plasma levels of lipids, lipoproteins and apolipoproteins in the patients suffered from HCC reflects on the hepatic cellular impairment status. Studies revealed that alterations seen in the plasma levels of lipids, lipoproteins and apolipoproteins reflecting patients' pathologic conditions. Decreased serum levels of cholesterol and apoAI may indicate a poor prognosis. Human leukaemic cells and certain tumor tissues have a higher receptor-mediated uptake of HDL and LDL than the corresponding normal cells or tissues. LDL and HDL have therefore been proposed as a carrier for the water-insoluble anti-cancer agents.

Apoptosis and its pathway in X gene-transfected HepG2 cells

AIM: To investigate the effect of hepatitis B virus (HBV) X gene on apoptosis and expressions of apoptosis factors in X gene-transfected HepG₂ cells.

METHODS: The HBV X gene eukaryon expression vector pcDNA3-X was transiently transfected into HepG₂ cells by lipid-media transfection. Untransfected HepG₂ and HepG₂ transfected with pcDNA3 were used as controls. Expression of HBx in HepG₂ was identified by RT-PCR. MTT and TUNEL were employed to measure proliferation and apoptosis of cells in three groups. Semi-quantified RT-PCR was used to evaluate the expression levels of Fas/FasL, Bax/Bcl-xL, and c-myc in each group.

RESULTS: HBV X gene was transfected into HepG₂ cells successfully. RT-PCR showed that HBx was only expressed in HepG₂/pcDNA3-X cells, but not expressed in HepG₂ and HepG₂/pcDNA3 cells. Analyzed by MTT, cell proliferation capacity was obviously lower in HepG₂/pcDNA3-X cells (0.08910±0.003164) than in HepG₂ (0.14410±0.004927) and HepG₂/pcDNA3 cells (0.12150±0.007159) (P<0.05 and P<0.01). Analyzed by TUNEL, cell apoptosis was much more in HepG₂/pcDNA3-X cells (980/2 000) than HepG₂ (420/2 000), HepG₂/pcDNA3 cells (520/2 000) (P<0.05 and P<0.01). Evaluated by semi-quantified RT-PCR, the expression level of Fas/FasL was significantly higher in HepG₂ cells transfected with HBx than in HepG₂ and HepG₂/pcDNA3cells (P<0.05 and P<0.01). Bax/Bcl-xL expression level was also elevated in HepG₂/pcDNA3-X cells (P<0.05 and P<0.01). Expression of c-myc was markedly higher in HepG₂/pcDNA3-X cells than in HepG₂ and HepG₂/pcDNA3 cells (P<0.05 andP<0.01).

CONCLUSION: HBV X gene can impair cell proliferation capacity, improve cell apoptosis, and upregulate expression of apoptosis factors. The intervention of HBV X gene on the expression of apoptosis factors may be a possible mechanism responsible for the change in cell apoptosis and proliferation.

Interferon-gamma inhibits hepatitis B virus-induced NF-kappaB activation through nuclear localization of NF-kappaB-inducing kinase

BACKGROUND & AIMS

Nuclear factor-kappaB (NF-kappaB) signaling pathway is an important regulating pathway in liver diseases, including hepatocellular carcinoma. In our study, immunohistochemical analysis showed that NF-kappaB-inducing kinase (NIK), an upstream kinase of IkappaB kinases, nuclear localization occurs only in liver tissues obtained from hepatitis B surface antigen (HBsAg)(+) patients but not in tissues from HBsAg(-) patients. The aim of the present study was to identify the inducer of NIK nuclear localization and determine whether the NIK nuclear localization affects the hepatitis B virus (HBV)-mediated NF-kappaB activation.

METHODS

The experiments were performed on HepG2.2.15 cells and on HepG2 cells transfected with pHBV1.2x, a plasmid encoding all HBV messages, using NF-kappaB-dependent luciferase reporter gene assay, electrophoretic mobility shift assay, immunoblot analysis, and fluorescent microscopy analysis.

RESULTS

HBV induced NIK-dependent NF-kappaB activation. However, interferon (IFN)-gamma induced NIK nuclear localization and inhibited NF-kappaB activation in HepG2.2.15 cells and in HepG2 cells transfected with pHBV1.2x. When NIK nuclear localization was inhibited by deletion of nuclear localization signal on NIK, IFN-gamma did not induce the NIK nuclear localization and did not inhibit NF-kappaB activation.

CONCLUSIONS

IFN-gamma selectively inhibits HBV-mediated NF-kappaB activation. This inhibition is accomplished by NIK nuclear localization, which is a novel mechanism of NF-kappaB inhibition.

Clinicopathological significance of loss of heterozygosity and microsatellite instability in hepatocellular carcinoma in China

AIM: To determine the features of microsatellite alterations and their association with clinicopathological characteristics of hepatocellular carcinoma (HCC).

METHODS: Loss of heterozygosity (LOH) and microsatellite instability (MSI) of 55 microsatellite loci were detected with PCR-based microsatellite polymorphism analyses in tumors and corresponding noncancerous liver tissues of 56 surgically resected HCCs using the MegaBACE 500 automatic DNA analysis system.

RESULTS: LOH was found in 44 of 56 HCCs (78.6%) at one or several loci. Frequencies of LOH on 1p, 4q, 8p, 16q, and 17p were 69.6% (39/56), 71.4% (40/56), 66.1% (37/56), 66.1% (37/56), and 64.3% (36/56), respectively. MSI was found in 18 of 56 HCCs (32.1%) at one or several loci. Ten of fifty-six (17.9%) HCCs had MSI-H. Serum HBV infection, alpha-fetoprotein concentration, tumor size, cirrhosis, histological grade, tumor capsule, as well as tumor intrahepatic metastasis, might be correlated with LOH on certain chromosome regions.

CONCLUSION: Frequent microsatellite alterations exist in HCC. LOH, which represents a tumor suppressor gene pathway, plays a more important role in hepatocarcin-ogenesis. MSI, which represents a mismatch repair gene pathway, is a rare event during liver carcinogenesis. Furthermore, LOH on certain chromosome regions may be correlated with clinicopathological characteristics in HCC.

Accumulation of 8-hydroxy-2'-deoxyguanosine adducts in HBx recombinant HepG2 cells and HBx transgenic mice

BACKGROUND/AIMS

Transgenic mice overexpressing hepatitis B x protein (HBx) show an increased susceptibility to mutations if exposed to mutagens. Also involved in HBx signalling, reactive oxygen intermediates (ROI) can induce DNA adducts such as 8-hydroxy-2'-deoxyguanosine that can in turn lead to G/T transversion mutations. Therefore, we investigated whether HBx expression increases the level of the mutational precursor 8-hydroxy-2'-deoxyguanosine in hepatocellular DNA.

METHODS

8-hydroxy-2'-deoxyguanosine concentrations of DNA hydrolysates of HBx protein expressing HepG2 cells and livers of HBx transgenic mouse lines were determined electrochemically after HPLC fractionation.

RESULTS

8-hydroxy-2'-deoxyguanosine concentrations in genomic DNA of HBx protein expressing cell lines correlated with the factor of transactivation. The 8-hydroxy-2'-deoxyguanosine levels were reduced after incubation of HBx recombinant cell lines with 0.1 or 1 mM of the antioxidant N-acetylcysteine. Hepatic 8-hydroxy-2'-deoxyguanosine concentrations in DNA of old transgenic mice were significantly, i.e. twofold, (p < 0.01) increased as compared to those of old nontransgenic or young transgenic controls and of control mice expressing a second HBV transactivator (MHBs(t76)).

CONCLUSION

HBx expression results in elevated DNA adduct levels. This could reflect a direct inhibitory interaction of HBx with cellular repair mechanisms. Alternatively, this may be an effect of an increased generation of reactive oxygen intermediates through HBx.

Replication and gene expression of mutant hepatitis B virus in a transgenic mouse containing the complete viral genome with mutant s gene

AIM: To establish the transgenic mouse line harbouring complete hepatitis B virus (HBV) genome with mutant s gene (adr subtype).

METHODS: Transgenic mice were generated by microinjecting HBV genome into fertilized eggs. Integration, expression, replication of HBV gene and histological changes in transgenic mice were estimated by genomic DNA PCR, serum DNA PCR, Southern blot, ELISA, HE staining, immunohistochemistry and transmission electron microscopy. Transgenic mice with HBsAg positive in serum were bred and analyzed.

RESULTS: A total of 288 eggs survived from microinjections were transplanted into the oviducts of 13 pseudopregnant mice and 49 pups were produced. Twenty-six mice were identified to have the integrated HBV gene. Serum HBsAg and HBeAg were detected in 2 of 43 mice. HBsAg and HBcAg in cytoplasm or nuclei of hepatocytes were detected in 10 mice. Founders with HBsAg in serum were named lineages G145R-15 and G145R-18. Of the 16 F1 offsprings generated by G145R-15 founder, 12 were positive for HBV genome with PCR, 10 were positive for HBsAg and HBcAg with immunohistochemistry and 7 were positive for HBsAg and HBeAg with ELISA. Only 1 of 8 F1 offsprings generated by G145R-18 founder was survived and it was detected positive for HBV genome, HBsAg, HBcAg and HBeAg. Both of the two lineages had some pathological characteristics of mild chronic hepatitis B in the liver, such as swelling of hepatocytes and focal hepatocellular necrosis and parenchymal lymphomononuclear cell infiltrate.

CONCLUSION: Transgenic mice harbouring HBV with mutant s gene can be generated. The HBV genes are integrated in the transgenic mice genome and can be expressed, replicated, packaged and excreted. HBV DNA can be stably transmitted in the transgenic mice.

Genomic instability in hepatocellular carcinoma revealed by using the random amplified polymorphic DNA method

PURPOSE

To investigate the genomic instability and their association with clinicopathological characteristics in hepatocellular carcinoma (HCC).

METHODS

DNA isolated from tumors and corresponding non-cancerous liver tissues of 56 patients with HCC was amplified with ten random 10-mer arbitrary primers by the random amplified polymorphic DNA (RAPD) method.

RESULTS

All the cases of HCC were demonstrated to have genomic instability by at least one primer. The incidence of genomic instability ranged from 20 to 70% in each case, and 17.9-50% in each primer. Serum AFP concentration, HBV infection, tumor size, histological grade, tumor capsule invasion, as well as intrahepatic metastasis were associated with the genomic instability on certain primers.

CONCLUSIONS

Genomic instability is a frequent event in HCC. The RAPD is an effective method for the identification and analysis of genomic instability in HCC, and it may provide new information for further evaluating the molecular mechanism of hepatocarcinogenesis.

High risk of hepatocellular carcinoma in anti-HBe positive liver cirrhosis patients developing lamivudine resistance

The emergence of drug-resistant virus in hepatitis B virus patients treated with lamivudine is well documented. However, its clinical impact in the long-term treatment of anti-HBe positive compensated cirrhotic patients is not well known. In this study, we treated 22 consecutive patients with anti-HBe compensated cirrhosis with lamivudine for a median period of 42 months. All patients responded to lamivudine, but viral breakthrough occurred in 13 patients (59%) between 9 and 42 months of therapy due to the emergence of a mutant strain. During the follow-up, 11 developed hepatocellular carcinoma. Of these, 10 occurred soon after the emergence of viral resistance, generally showing aggressive behaviour, and one in the nine long-term responder patients (P = 0.013). Lamivudine resistance was the only independent predictor of hepatocellular carcinoma development (risk ratio: 10.4; 95% CI: 1.3-84.9). Our study suggests that the occurrence of lamivudine resistance increases the risk of hepatocellular carcinoma in anti-HBe positive cirrhosis and warrants further research.

Screening and identification of genes trans-regulated by HBV pre-S2 protein with cDNA microarray

AIM: To understand the target genes up-regulated or down-regulated by HBV pre-S2 protein, we compared the differentially expressed genes between the hepatoblastoma cell line HepG2 transfected by pcDNA3.1(-) and pcDNA3.1(-)-preS2, respectively with cDNA microarray technique.

METHODS: The HBV pre-S2 coding DNA fragment was amplified with polymerase chain reaction (PCR) technique by using G376-7 plasmid containing the full length of HBV genome as the template. The expressive vector of pcDNA3.1-preS2 was constructed by routine molecular biological methods. The HepG2 cells were transfected by pcDNA3.1(-) and pcDNA3.1(-)-preS2, respectively, using FuGENE6 transfection reagent. The total RNA was isolated and reversely transcribed. The cDNAs were subjected for microarray screening with 1 152 cDNA probes.

RESULTS: The expressive vector was constructed and confirmed by restriction enzyme digestion and DNA sequencing analysis. High quality mRNA and cDNA were prepared and successful microarray screening conducted. From the scanning results, it was found 42 genes were up-regulated and 36 genes down-regulated by pre-S2 protein of HBV.

CONCLUSION: HBV pre-S2 protein is a transactivator. The expression of pre-S2 protein affects the expression spectrum of HBV infected hepatocyte.

Relationship between PBMC apoptosis and serum HBV level in HBV positive patients

AIM: To investigate the relationship between the serum HBV DNA quantification and the PBMCs apoptosis of the chronic hepatitis B.

METHODS: Peripheral blood mononuclear cells (PBMCs) were isolated from 10 healthy blood donors and 42 patients with HBV positive. PBMCs were cultured with PHA for 72 h in vitro. Then we used TUNEL and flow cytometry to assay the apoptosis. The HBV-DNA extracted from the serum in patients by PCR was quantified by ELISA. We used the one way ANOVA to analysis the apoptosis and the HBV-DNA quantity, and made correlation analysis between the apoptosis and the HBV-DNA quantity.

RESULTS: We identified the apoptosis by TUNEL and flow cytometry in cultured PBMCs. The apoptosis rate in mild type of chronic hepatitis B, moderate type of chronic hepatitis B and cirrhosis were (29.3% ± 9.3%, 24.8% ± 10.8%, 28.8% ± 5.0%), compared to the healthy group (18.0% ± 6.4%). Serum HBV-DNA level was the highest in mild type of chronic hepatitis B (14.3×10⁷ cp/L ± 24.8×10⁷ cp/L), which was higher than other groups(P < 0.05). The serum HBV-DNA level in mild type of chronic hepatitis B is the highest. The serum HBV-DNA level had the correlation with the apoptosis in PBMC (r = 0.338, P = 0.014).

CONCLUSION: There is apoptosis in PBMC of the HBV chronic infections. The serum virus level is the highest in mild type of chronic hepatitis B, while its apoptosis is also the highest. The immune and HBV virus persistent condition are related to the apoptosis. The percentage of the apoptosis in PBMC has the correlation with the virus level in serum of the HBV chronic infections.