Hepatitis B virus-transfected Hep G2 cells demonstrate genetic alterations and de novo viral integration in cells replicating HBV

Sparse logistic regression revealed the associations between HBV PreS quasispecies and hepatocellular carcinoma

BACKGROUND

Chronic infection with hepatitis B virus (HBV) has been proved highly associated with the development of hepatocellular carcinoma (HCC).

AIMS

The purpose of the study is to investigate the association between HBV preS region quasispecies and HCC development, as well as to develop HCC diagnosis model using HBV preS region quasispecies.

METHODS

A total of 104 chronic hepatitis B (CHB) patients and 117 HBV-related HCC patients were enrolled. HBV preS region was sequenced using next generation sequencing (NGS) and the nucleotide entropy was calculated for quasispecies evaluation. Sparse logistic regression (SLR) was used to predict HCC development and prediction performances were evaluated using receiver operating characteristic curves.

RESULTS

Entropy of HBV preS1, preS2 regions and several nucleotide points showed significant divergence between CHB and HCC patients. Using SLR, the classification of HCC/CHB groups achieved a mean area under the receiver operating characteristic curve (AUC) of 0.883 in the training data and 0.795 in the test data. The prediction model was also validated by a completely independent dataset from Hong Kong. The 10 selected nucleotide positions showed significantly different entropy between CHB and HCC patients. The HBV quasispecies also classified three clinical parameters, including HBeAg, HBVDNA, and Alkaline phosphatase (ALP) with the AUC value greater than 0.6 in the test data.

CONCLUSIONS

Using NGS and SLR, the association between HBV preS region nucleotide entropy and HCC development was validated in our study and this could promote the understanding of HCC progression mechanism.

HBV Integration-mediated Cell Apoptosis in HepG2.2.15

Hepatocellular carcinoma (HCC) is the most common type of primary liver cancer and the second leading cause of cancer deaths in the word. Hepatitis B virus (HBV) infection plays an important role in the development of HCC. However, the mechanisms by which HBV integration affects host cells remain poorly understood. HepG2.2.15 cell line is derived from HCC cell line HepG2 with stable transfection HBV expression. In this study, HepG2.2.15 cells showed decreased proliferation, G1 cell cycle arrest and increased apoptosis, when compared to HepG2 cells. HBV capture sequencing was conducted in both genome and transcriptome level, followed by RNA expression sequencing in HepG2.2.15. Here, CAMSAP2/CCDC12/DPP7/OR4F3 were found to be targets for HBV integration in both genome and transcriptome level, accompanied by alteration in their expression when compared to HepG2. Among these genes, DPP7 was the only one gene with HBV integration into its exon, meanwhile DPP7 expression level was also downregulated in HepG2.2.15 as compared to HepG2. Furthermore, DPP7 knockdown resulted in increased apoptosis through upregulation of the Bax/Bcl2 ratio in HepG2 cells. Our results suggest that HBV integration of DPP7 was involved in cell apoptosis.

Proportion of transcriptionally active DNA virus integrants: a meta-analysis

Oncoviruses are collectively responsible for over 1,000,000 new cases of cancer per year; some can integrate into the host's chromosomes. The present work was aimed at assessing the proportion of transcriptionally active viral integrants through a systematic review of the scientific publications present on the MedLine database. From the articles screened, 628 viral integrants overall were retrieved, of which 530.84 were transcriptionally active (84.53%); among the clinical samples, 264 of 323 integrants were active (81.73%). The causes for the silencing were not addressed in the articles analyzed. These findings might highlight a possible risk factor for the insurgence of cancer since some oncovirus integrants could be reactivated by stimuli of disparate nature. Further studies should address such possibility.

Targeting selenium nanoparticles combined with baicalin to treat HBV-infected liver cancer

Herein, we demonstrate baicalin-loaded selenium nanoparticles with a liver-targeting folic acid moiety to treat HBV-infected liver cancer.

Role of the line probe assay INNO-LiPA HBV DR and ultradeep pyrosequencing in detecting resistance mutations to nucleoside/nucleotide analogues in viral samples isolated from chronic hepatitis B patients

Despite the effectiveness of nucleoside/nucleotide analogues in the treatment of chronic hepatitis B (CHB), their long-term administration is associated with the emergence of resistant hepatitis B virus (HBV) mutants. In this study, mutations resulting in antiviral resistance in HBV DNA samples isolated from 23 CHB patients (nine treatment naïve and 14 treated previously) were studied using a line probe assay (INNO-LiPA HBV DR; Innogenetics) and ultradeep pyrosequencing (UDPS) methods. Whilst the INNO-LiPA HBV DR showed no resistance mutations in HBV DNA samples from treatment-naive patients, mutations mediating lamivudine resistance were detected in three samples by UDPS. Among patients who were treated previously, 19 mutations were detected in eight samples using the INNO-LiPA HBV DR and 29 mutations were detected in 12 samples using UDPS. All mutations detected by the INNO-LiPA HBV DR were also detected by UDPS. There were no mutations that could be detected by INNO-LiPA HBV DR but not by UDPS. A total of ten mutations were detected by UDPS but not by INNO-LiPA HBV DR, and the mean frequency of these mutations was 14.7 %. It was concluded that, although INNO-LiPA HBV DR is a sensitive and practical method commonly used for the detection of resistance mutations in HBV infection, UDPS may significantly increase the detection rate of genotypic resistance in HBV at an early stage.

Effects of hepatitis B virus mutations on its replication and liver disease severity

Hepatitis B virus (HBV), nowadays, is one of the major human pathogens worldwide. Approximately, 400 million people worldwide have chronic HBV infection. Only 5% of persons infected during adulthood develop chronic infection. The reverse is true for those infected at birth or in early childhood, i.e. more than 90% of these persons progress to chronic infection. Currently, eight different genotypes o f HBV have been identified, differing in nucleotide sequence by greater than 8%. In addition, numerous subgenotypes have a l s o been recognized based on the nucleotide sequence variability of 4- 8%. It has invariably been found that these genotypes and mutations play a pivotal role in the liver disease aggravation and virus replication. The precore mutations (G1896A) and the double mutation (T1762/A1764) in the basal core promoter are important mutations that alter expression of the hepatitis B e antigen (HBeAg). The HBeAg is important for establishing viral persistence. The precore G1896A mutation abrogates the expression of HBeAg. Numerous other mutations alter the disease severity and progression. It is predictive that the infected patient has high risk of hepatocellular carcinoma if the genotype C is incriminated or if HBV possesses basal core promoter double mutation. Association of the remaining genotypes have been noted but with less degree than genotype C. Phenotypic assays of the different HBV protein markers with different molecular techniques illustrate the replication efficiency of the virus in cell lines. This review will discuss various mutations into their association with liver disease severity and progression as well as virus replication.

Hepatitis B virus induces G1 phase arrest by regulating cell cycle genes in HepG2.2.15 cells

Background

To investigate the effect of HBV on the proliferative ability of host cells and explore the potential mechanism.

Methods

MTT, colony formation assay and tumourigenicity in nude mice were performed to investigate the effect of HBV on the proliferative capability of host cells. In order to explore the potential mechanism, cell cycle and apoptosis were analysed. The cell cycle genes controlling the G1/S phase transition were detected by immunohistochemistry, westernblot and RT-PCR.

Results

HepG2.2.15 cells showed decreased proliferation ability compared to HepG2 cells. G1 phase arrest was the main cause but was not associated with apoptosis. p53, p21 and total retinoblastoma (Rb) were determined to be up-regulated, whereas cyclinE was down-regulated at both the protein and mRNA levels in HepG2.2.15 cells. The phosphorylated Rb in HepG2.2.15 cells was decreased.

Conclusions

Our results suggested that HBV inhibited the capability of proliferation of HepG2.2.15 cells by regulating cell cycle genes expression and inducing G1 arrest.

Hepatitis B virus X protein induces apoptosis and cell cycle deregulation through interfering with DNA repair and checkpoint responses

AIM

To investigate the effects of hepatitis B virus X (HBx) gene on apoptosis and cell cycle in hepatocyte line HL-7702 and to discuss the possible mechanisms in the pathway.

METHODS

The recombinant plasmid pcDNA3-X and vector pcDNA3 were transfected into HL-7702 cells and selected by G418 to construct two new cell lines, which were named HL-7702-HBx and HL-7702-con, respectively. Reverse transcription polymerase chain reaction (RT-PCR) and western blot analysis were used to confirm that HBx gene was expressed steadily in the HL-7702-HBx cells. Then apoptosis and cell cycle of the two cells were detected by DNA ladder, flow cytometric analysis, and electronic microscope observation. Apoptosis and cell cycle gene expressions in the two cells were subsequently evaluated by using gene arrays. Some of results were further confirmed by real-time PCR and western blot analysis.

RESULTS

RT-PCR and the western blot analysis showed that HL-7702-HBx expressed the HBx gene steadily. Comparedwith the HL-7702-con cells, there was increased apoptosis and accumulation of the S phase in the HL-7702-HBx cells. The gene array analysis indicated that some DNA repair genes (XRCC1, DDB1, etc.) and DNA damage checkpoint-related genes (Cdc47, RAD17, etc.) played roles in the HBx-mediated imbalance of apoptosis and cell cycle. Both cDNA array analysis and real-time RT-PCR showed that mRNA of XRCC1, Cdc47 and RAD17 were upregulated by HBx. Unexpectedly, the western blot analysis revealed that HBx inhibited their protein expression.

CONCLUSION

The expression of HBx in HL-7702 cells promoted apoptosis and accumulation of the S phase through the inhibition of DNA repair and checkpoints via post-transcriptional mechanisms.

Dysregulation of apoptotic death in the pathogenesis of virus-induced cytogenetic instability of blood lymphocytes

The cytogenetic status and activity of regulatory systems for stability of the cell genome were evaluated in patients with chronic viral persistence. Hepatitis B and C viruses damage the chromosome apparatus of peripheral blood lymphocytes. Cytogenetic instability of immunocompetent cells during chronic viral infection was associated with inhibition of DNA excision repair system and dysregulation of apoptosis in target cells.

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.

Differential effects on apoptosis induction in hepatocyte lines by stable expression of hepatitis B virus X protein

AIM: Hepatitis B virus protein X (HBx) has been shown to be weakly oncogenic in vitro. The transforming activities of HBx have been linked with the inhibition of several functions of the tumor suppressor p53. We have studied whether HBx may have different effects on p53 depending on the cell type.

METHODS: We used the human hepatoma cell line HepG2 and the immortalized murine hepatocyte line AML12 and analyzed stably transfected clones which expressed physiological amounts of HBx. P53 was induced by UV irradiation.

RESULTS: The p53 induction by UV irradiation was unaffected by stable expression of HBx. However, the expression of the cyclin kinase inhibitor p21^waf/cip/sdi which gets activated by p53 was affected in the HBx transformed cell line AML12-HBx9, but not in HepG2. In AML-HBx9 cells, p21^waf/cip/sdi-protein expression and p21^waf/cip/sdi transcription were deregulated. Furthermore, the process of apoptosis was affected in opposite ways in the two cell lines investigated. While stable expression of HBx enhanced apoptosis induced by UV irradiation in HepG2-cells, apoptosis was decreased in HBx transformed AML12-HBx9. P53 repressed transcription from the HBV enhancer I, when expressed from expression vectors or after induction of endogenous p53 by UV irradiation. Repression by endogenous p53 was partially reversible by stably expressed HBx in both cell lines.

CONCLUSION: Stable expression of HBx leads to deregulation of apoptosis induced by UV irradiation depending on the cell line used. In an immortalized hepatocyte line HBx acted anti-apoptotic whereas expression in a carcinoma derived hepatocyte line HBx enhanced apoptosis.

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Effects of hepatitis B virus on p53 expression in hepatoma cell line SMMU-7721

AIM

To investigate the contribution of HBV in the development of hepatocarcinoma by examining the effects of HBV on p53 function in SMMU-7721 cell line.

METHODS

Plasmid pCMVp53 was transfected or cotransfected with pCMVHBVa (wild-type HBV) or PCMVHBVb (mutation type HBV) into the hepatoma cell line SMMU-7721 by lipofectamine. Apoptosis cells were labeled with annexin V-FITC and confirmed by flow cytometry. Reporter plasmid PG13-CAT or p21-luc was cotransfected, respectively, into each group to determine the transactivation activity of p53 and its effect on p21 promoter. Western blot was performed to observe p53 expression in hepatoma cell line of each group.

RESULTS

The group transfected with pCMVp53 alone exhibited higher luciferase activity and higher apoptosis rate, otherwise, the p53 expression and reporter activity of PG13-CAT or P21-luc as well as cell apoptosis rate were obviously higher in the group cotransfected of pCMVp53 with pCMVHBVa, but not in the other cotransfected group.

CONCLUSION

Transient transfection of HBV into the SMMU-7721 cell line can enhance p53 expression and its effects on development of hepatocarcinoma.

Mitotic Aberration Coupled With Centrosome Amplification Is Induced by Hepatitis B Virus X Oncoprotein via the Ras-Mitogen-Activated Protein/Extracellular Signal-Regulated Kinase-Mitogen-Activated Protein Pathway

Multinucleated cells have been noted in pathophysiological states of the liver including infection with hepatitis B virus (HBV), the status of which is also closely associated with genomic instability in liver cancer. Here, we showed that hepatitis B virus X oncoprotein (HBx) expression in Chang cells results in a multinuclear phenotype and an abnormal number of centrosomes (n  ≥ 3). Regulation of centrosome duplication in HBx-expressing ChangX-34 cells was defective and uncoupled from the cell cycle. HBx induced amplification of centrosomes, multipolar spindle formation, and chromosomal missegregation during mitosis and subsequently increased the generation of multinucleated cells and micronuclei formation. Treatment with PD98059, a mitogen-activated protein/extracellular signal-regulated kinase (MEK) 1/2 inhibitor, significantly reduced the number of cells with hyperamplified centrosomes and decreased the multinucleated cells and micronuclei formation. Consistently, the phospho-ERK level during cell progression was substantially higher in ChangX-34 cells than that of Chang cells. In contrast, neither wortmannin, an inhibitor of phosphoinositide-3 kinase, nor SB203589, an inhibitor of p38 mitogen-activated protein kinase (MAPK), showed any effects. Introduction of Ras dominant-negative (D/N) and MEK2 D/N genes into ChangX-34 cells significantly alleviated centrosome amplification, whereas introduction of the PKC D/N and PKB D/N genes did not. Thus, our results demonstrate that the HBx induced centrosome hyperamplification and mitotic aberration by activation of the Ras-MEK-MAPK. Intervention of this signaling pathway could suppress the centrosome amplification as well as mitotic aberration. These findings may provide a possible mechanism by which HBx promotes phenotypic progression by predisposing chromosomal alteration in HBV-infected liver.

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Effects of hepatitis B virus infection on human sperm chromosomes

AIM: To evaluate the level of sperm chromosome aberrations in male patients with hepatitis B, and to directly detect whether there are HBV DNA integrations in sperm chromosomes of hepatitis B patients.

METHODS: Sperm chromosomes of 14 tested subjects (5 healthy controls, 9 patients with HBV infection, including 1 with acute hepatitis B, 2 with chronic active hepatitis B, 4 with chronic persistent hepatitis B, 2 chronic HBsAg carriers with no clinical symptoms) were prepared using interspecific in vitro fertilization between zona-free golden hamster ova and human spermatozoa, and the frequencies of aberration spermatozoa were compared between subjects of HBV infection and controls. Fluorescence in situ hybridization (FISH) to sperm chromosome spreads was carried out with biotin-labeled full length HBV DNA probe to detect the specific HBV DNA sequences in the sperm chromosomes.

RESULTS: The total frequency of sperm chromosome aberrations in HBV infection group (14.8%, 33/223) was significantly higher than that in the control group (4.3%, 5/116). Moreover, the sperm chromosomes in HBV infection patients commonly presented stickiness, clumping, failure to staining, etc, which would affect the analysis of sperm chromosomes. Specific fluorescent signal spots for HBV DNA were seen in sperm chromosomes of one patient with chronic persistent hepatitis. In 9 (9/42) sperm chromosome complements containing fluorescent signal spots, one presented 5 obvious FISH spots, others presented 2 to 4 signals. There was significant difference of fluorescence intensity among the signal spots. The distribution of signal sites among chromosomes was random.

CONCLUSION: HBV infection can bring about mutagenic effects on sperm chromosomes. Integrations of viral DNA into sperm chromosomes which are multisites and nonspecific, can further increase the instability of sperm chromosomes. This study suggested that HBV infection can create extensively hereditary effects by alteration genetic constituent and/or induction chromosome aberrations, as well as the possibility of vertical transmission of HBV via the germ line to the next generation.

Increased chromosomal alterations and micronuclei formation in human hepatoma HepG2 cells transfected with the hepatitis B virus HBX gene

The protein encoded by the hepatitis B virus (HBV)-X gene, HBX, has been implicated to be involved in the development of HBV-associated liver cancer. HBX is a multifunctional regulatory protein that has been identified as a potential oncogene but its exact function remains unclear. HBX was documented to interact with several factors involved in cellular DNA repair as well as compromise the cell's ability to repair damaged DNA. We previously documented an accumulation of genetic alterations in two HepG2 cell lines independently transfected with HBV. In this report, we investigate the effect of the HBV-X gene (HBX) on the stability of the host genome using HepG2 stable transfectants (HepG2-HBX) and vector controls (HepG2-neo). We document that all HepG2-HBX clones analyzed contain HBX gene integrated and HBX transcript. Our data demonstrate that HepG2-HBX cells have an increased number of chromosome alterations and micronuclei formation compared to vector controls. A total of 10 de novo chromosomal rearrangements involving nine different chromosomes were detected in the HepG2-HBX clones, while no new rearrangements were found in vector controls. Each HepG2-HBX clone contained independently occurring de novo alterations not found in other HBX or vector clones. A three-fold increase of micronuclei formation was detected in HepG2-HBX cells compared to vector controls. Micronuclei originated from all chromosomes, however, preliminary data indicated that micronuclei originating from chromosomes 2, 3, 7, 18 and 20 were found in a greater amount in cells expressing the HBX gene. Interestingly, chromosomes 2, 18 and 20 were three of the chromosomes found rearranged in HepG2-HBX clones. These data provide evidence that genomic integrity was affected in cells expressing the HBX gene. De novo cytogenetic alterations identified in HepG2-HBX clones implicate the involvement of HBX in the process and support the hypothesis that HBX may interfere with normal cellular processes responsible for genomic integrity, increasing the risk for acquiring genetic mutations in infected hepatocytes.

Expression of GP73, a resident Golgi membrane protein, in viral and nonviral liver disease

GP73 is a novel type II Golgi membrane protein of unknown function that is expressed in the hepatocytes of patients with adult giant-cell hepatitis (Gene 2000;249:53-65). Its expression pattern in human liver disease and the regulation of its expression in hepatocytes have not been systematically studied. The aims of the present study were to compare GP73 protein levels in viral and nonviral human liver disease and in normal livers, to identify its cellular sources, and to study the regulation of its expression in hepatoma cells in vitro. GP73 protein levels were quantitated in explant livers of patients with well-defined disease etiologies and compared with the levels in normal donor livers. GP73-expressing cells were identified immunohistochemically. GP73 expression in vitro was studied by Western blotting and immunofluorescence microscopy in HepG2 and SK-Hep-1 cells and in the HepG2-derived, hepatitis B virus (HBV)-transfected HepG2215 and HepG2T14.1 cell lines. Whole organ levels of GP73 were low in normal livers. Significant increases were found in liver disease due to viral causes (HBV, HCV) or nonviral causes (alcohol-induced liver disease, autoimmune hepatitis). In normal livers, GP73 was constitutively expressed by biliary epithelial cells but not by hepatocytes. Hepatocyte expression of GP73 was dramatically up-regulated in diseased livers, regardless of the etiology, whereas biliary epithelial cell expression did not change appreciably. GP73 was present at high levels in HepG2215 cells (a cell line that supports active HBV replication), but was absent in HepG2T14.1 cells (an HBV-transfected cell line that does not support HBV replication) and in HBV-free HepG2 cells. In SK-Hep-1 cells, GP73 expression was increased in response to interferon gamma (IFN-gamma), and inhibited by tumor necrosis factor alpha (TNF-alpha). In conclusion, increased expression of GP73 in hepatocytes appears to be a general feature of advanced liver disease, and may be regulated via distinct pathways that involve hepatotropic viruses or cytokines.