Woodchuck hepatitis virus-induced carcinoma as a relevant natural model for therapy of human hepatoma

Animal Models for the Study of Hepatitis B Virus Pathobiology and Immunity: Past, Present, and Future

Hepatitis B virus (HBV) infection is a global public health problem that plagues approximately 240 million people. Chronic hepatitis B (CHB) often leads to liver inflammation and aberrant repair which results in diseases ranging from liver fibrosis, cirrhosis, to hepatocellular carcinoma. Despite its narrow species tropism, researchers have established various in vivo models for HBV or its related viruses which have provided a wealth of knowledge on viral lifecycle, pathogenesis, and immunity. Here we briefly revisit over five decades of endeavor in animal model development for HBV and summarize their advantages and limitations. We also suggest directions for further improvements that are crucial for elucidation of the viral immune-evasion strategies and for development of novel therapeutics for a functional cure.

Application of the woodchuck animal model for the treatment of hepatitis B virus-induced liver cancer

This review describes woodchucks chronically infected with the woodchuck hepatitis virus (WHV) as an animal model for hepatocarcinogenesis and treatment of primary liver cancer or hepatocellular carcinoma (HCC) induced by the hepatitis B virus (HBV). Since laboratory animal models susceptible to HBV infection are limited, woodchucks experimentally infected with WHV, a hepatitis virus closely related to HBV, are increasingly used to enhance our understanding of virus-host interactions, immune response, and liver disease progression. A correlation of severe liver pathogenesis with high-level viral replication and deficient antiviral immunity has been established, which are present during chronic infection after WHV inoculation of neonatal woodchucks for modeling vertical HBV transmission in humans. HCC in chronic carrier woodchucks develops 17 to 36 mo after neonatal WHV infection and involves liver tumors that are comparable in size, morphology, and molecular gene signature to those of HBV-infected patients. Accordingly, woodchucks with WHV-induced liver tumors have been used for the improvement of imaging and ablation techniques of human HCC. In addition, drug efficacy studies in woodchucks with chronic WHV infection have revealed that prolonged treatment with nucleos(t)ide analogs, alone or in combination with other compounds, minimizes the risk of liver disease progression to HCC. More recently, woodchucks have been utilized in the delineation of mechanisms involved in innate and adaptive immune responses against WHV during acute, self-limited and chronic infections. Therapeutic interventions based on modulating the deficient host antiviral immunity have been explored in woodchucks for inducing functional cure in HBV-infected patients and for reducing or even delaying associated liver disease sequelae, including the onset of HCC. Therefore, woodchucks with chronic WHV infection constitute a well-characterized, fully immunocompetent animal model for HBV-induced liver cancer and for preclinical evaluation of the safety and efficacy of new modalities, which are based on chemo, gene, and immune therapy, for the prevention and treatment of HCC in patients for which current treatment options are dismal.

Dose-Dependent Sorafenib-Induced Immunosuppression Is Associated with Aberrant NFAT Activation and Expression of PD-1 in T Cells

The multikinase inhibitor sorafenib is the only standard first-line therapy for hepatocellular carcinoma (HCC). Here, we report the dose-dependent effects of sorafenib on the immune response, which is related to nuclear factor of activated T cells 1 (NFAT1) activity. In vitro and in vivo experiments were performed with low and high doses of sorafenib using human T cells and spontaneous developed woodchuck HCC models. In vitro studies demonstrated that following exposure to a high dose of sorafenib the baseline activity of NFAT1 in T cells was significantly increased. In a parallel event, high dose sorafenib resulted in a significant decrease in T cell proliferation and increased the proportion of PD-1 expressing CD8+ T cells with NFAT1 activation. In the in vivo model, smaller tumors were detected in the low-dose sorafenib treated group compared to the placebo and high-dose treated groups. The low-dose sorafenib group showed a significant tumor growth delay with significantly more CD3+ cells in tumor. This study demonstrates that sorafenib has immunomodulatory effects in a dose- and time-dependent manner. Higher dose of sorafenib treatment was associated with immunosuppressive action. This observed effect of sorafenib should be taken into consideration in the selection of optimum starting dose for future trials.

The Use of the Woodchuck as an Animal Model for Evaluation of Transarterial Embolization

There are many shortcomings of current animal models as surrogates of hepatocellular carcinoma that handicap preclinical testing of embolization agents. The present study explores the feasibility of using the woodchuck (Marmota monax) as an animal model for the testing of novel embolization agents. Four woodchucks underwent magnetic resonance imaging, angiography, and left lobar hepatic artery particle embolization. Percutaneous access, arteriography, and lobar embolization were successful in all animals, with angiographic stasis obtained in the target vessel with minimal reflux of embolic material. These results support the feasibility of the woodchuck as an animal model for preclinical testing of embolization agents.

Suspected Hepadnavirus Association with a Hepatocellular Carcinoma in a Black-Tailed Prairie Dog (Cynomys ludovicianus)

Hepatocellular carcinomas are the most commonly reported neoplasm of black-tailed prairie dogs (Cynomys ludovicianus). In several other closely related Sciuridae species, infection with species-specific hepadnaviruses is associated with the development of these tumours, but such a hepadnavirus has not yet been identified in any prairie dog species, although its presence has been hypothesized previously. An adult prairie dog was humanely destroyed due to progressive illness and the identification of a cranial abdominal mass that was determined on histopathology to be a hepatocellular carcinoma. Deep sequencing of the tumour tissue identified the presence of a hepadnavirus, similar in its genetic structure to woodchuck hepatitis virus. Electron microscopy showed the presence of viral particles similar in structure to other hepadnaviral particles. This report suggests that a hepadnavirus may be associated with the development of hepatocellular carcinomas in the prairie dog.

Molecular cloning, characterization and expression analysis of TGF-β and receptor genes in the woodchuck model

Transforming growth factor beta (TGF-β) is an important cytokine with pleiotropic regulatory functions in the immune system and in the responses against viral infections. TGF-β acts on a variety of immune cells through the cell surface TGF-β receptor (University of Duisburg-EssenTGFBR). The woodchuck has been used as a biomedical model for studies of obesity and energy balance, endocrine and metabolic function, cardiovascular, cerebrovascular and neoplastic disease. Woodchucks infected with woodchuck hepatitis virus (WHV) represent an informative animal model to study hepatitis B virus (HBV) infection. In this study, the cDNA sequences of woodchuck TGF-β1, TGF-β2, TGFBR1 and TGFBR2 were cloned, sequenced and characterized. The full-length TGFBR1 cDNA sequence consisted of 1305bp coding sequence (CDS) that encoded 434 amino acids with a molecular weight of 48.9kDa. The phylogenetic tree analysis revealed that the woodchuck TGF-β family genes had a closer genetic relationship with Ictidomys tridecemlineatus. One antibody with cross-reactivity to woodchuck TGFBR1 was identified by flow cytometry. Moreover, the expression of these genes were analyzed at the transcriptional level. The quantitative PCR analysis showed that the TGF-β family transcripts were constitutively expressed in many tissues tested. Altered expression levels of the TGF-β family transcripts in the liver of WHV infected woodchucks were observed. These results serve as a foundation for further insight into the role of the TGF-β family in viral hepatitis in woodchuck model. Our work also possesses the potential value for characterizing the TGF-β family in other related diseases, such as obesity-related diseases, metabolic disorder, cardiovascular disease and cancer.

Development of a High-Throughput Molecular Imaging-Based Orthotopic Hepatocellular Carcinoma Model

We have developed a novel orthotopic rat hepatocellular (HCC) model and have assessed the ability to use bioluminescence imaging (BLI), positron emission tomography (PET), and ultrasound for early tumor detection and monitoring of disease progression.  Briefly, rat HCC cells were stably transfected with click beetle red as a reporter gene for BLI. Tumor cells were injected under direct visualization into the left or middle lobe of the liver in 37 rats. In six animals, serial PET, BLI, and ultrasound imaging were performed at 10-time points in 28 days. The remainder of the animals underwent PET imaging at 14 days. Tumor implantation was successful in 34 of 37 animals (91.9%). In the six animals that underwent serial imaging, tumor formation was first detected with BLI on Day 4 with continued increase through Day 21, and hypermetabolic activity on PET was first noted on Days 14-15 with continued increase through Day 28. PET activity was seen on Day 14 in the 28 other animals that demonstrated tumor development. Anatomic tumor formation was detected with ultrasound at Days 10-12 with continued growth through Day 28. The first metastases were detected by PET after Day 24.        We have successfully developed and validated a novel orthotopic HCC small animal model that permits longitudinal assessment of change in tumor size using molecular imaging techniques. BLI is the most sensitive imaging method for detection of early tumor formation and growth. This model permits high-throughput in vivo evaluation of image-guided therapies.

Subset of Suz12/PRC2 target genes is activated during hepatitis B virus replication and liver carcinogenesis associated with HBV X protein

Chronic hepatitis B virus (HBV) infection is a major risk factor for developing liver cancer, and the HBV X protein (pX) has been implicated as a cofactor in hepatocyte transformation. We have shown that HBV replication as well as in vitro transformation by pX are associated with induction of the mitotic polo-like kinase 1 (Plk1) and down-regulation of the chromatin remodeling components Suz12 and Znf198. Herein, we demonstrate the same inverse relationship between Plk1 and Suz12/Znf198 in liver tumors from X/c-myc bitransgenic mice and woodchuck hepatitis virus (WHV)-infected woodchucks. Employing these animal models and the HBV replicating HepAD38 cells we examined the effect of Suz12/Znf198 down-regulation on gene expression. Genes analyzed include hepatic cancer stem cell markers BAMBI, DKK1,2, DLK1, EpCAM, MYC, and proliferation genes CCNA1, CCND2, IGFII, MCM4-6, PLK1, RPA2, and TYMS. Suz12 occupancy at the promoters of BAMBI, CCND2, DKK2, DLK1, EpCAM, and IGFII was demonstrated by chromatin immunoprecipitation in untransformed hepatocytes, but was markedly reduced in pX-transformed and Suz12 knockdown cells. Accordingly, we refer to these genes as "Suz12 repressed" genes in untransformed hepatocytes. The Suz12 repressed genes and proliferation genes were induced in HBV-replicating HepAD38 cells and, interestingly, they exhibited distinct expression profiles during hepatocellular carcinoma (HCC) progression in X/c-myc bitransgenics. Specifically, CCND2, EpCAM, and IGFII expression was elevated at the proliferative and preneoplastic stages in X/c-myc bitransgenic livers, whereas BAMBI and PLK1 were overexpressed in hepatic tumors from X/c-myc bitransgenics and WHV-infected woodchucks. Importantly, most of these genes were selectively up-regulated in HBV-induced HCCs.

CONCLUSION

The distinct expression profile of the identified Suz12 repressed genes in combination with the proliferation genes hold promise as biomarkers for progression of chronic HBV infection to HCC.

Development of an animal model for radiofrequency ablation of primary, virally induced hepatocellular carcinoma in the woodchuck

PURPOSE

To develop a consistent and reproducible method in an animal model for studies of radiofrequency (RF) ablation of primary hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

Fifteen woodchucks were inoculated with woodchuck hepatitis virus (WHV) to establish chronic infections. When serum γ-glutamyl transpeptidase levels became elevated, the animals were evaluated with ultrasound, and, in most cases, preoperative magnetic resonance (MR) imaging to confirm tumor development. Ultimately, RF ablation of tumors was performed by using a 1-cm probe with the animal submerged in a water bath for grounding. Ablation effectiveness was evaluated with contrast-enhanced MR imaging and gross and histopathologic analysis.

RESULTS

RF ablation was performed in 15 woodchucks. Modifications were made to the initial study design to adapt methodology for the woodchuck. The last 10 of these animals were treated with a standardized protocol using a 1-cm probe that produced a consistent area of tumor necrosis (mean size of ablation, 10.2 mm × 13.1 mm) and led to no complications.

CONCLUSIONS

A safe, reliable and consistent method was developed to study RF ablation of spontaneous primary HCC using chronically WHV-infected woodchucks, an animal model of hepatitis B virus-induced HCC.

Combining antiangiogenic therapy with immunotherapy exerts better therapeutical effects on large tumors in a woodchuck hepatoma model

Cytokine and antiangiogenic gene therapies have proved effective in implanted hepatocellular carcinoma (HCC) models in which small tumor burdens were established in small rodents. These models, however, may not reflect human HCCs, which are frequently detected at a stage when tumors are large and multifocal. In addition, HCC in patients is often associated with viral hepatitis. To investigate the effectiveness of a mixture type of gene therapy strategy on large tumor burdens, we used the woodchuck model in which woodchuck hepatitis virus-induced HCCs are large and multifocal, simulating the conditions in humans. Adenoviruses encoding antiangiogenic factors (pigment epithelium-derived factor and endostatin) or cytokines (GM-CSF and IL-12) were delivered via the hepatic artery separately or in combination into woodchuck livers bearing HCCs. Our results showed that the mixture type of strategy, which contained two cytokines and two antiangiogenic factors, had better antitumor effects on large tumors as compared with monotherapy either with antiangiogenic or cytokine genes. The immunotherapy recruited significant levels of CD3(+) T cells that infiltrated the tumors, whereas the antiangiogenesis-based therapy significantly reduced tumor vasculature. The mixture type of gene therapy achieved both effects. In addition, it induced high levels of natural killer cells and apoptotic cells and reduced the levels of immunosuppressive effectors in the tumor regions. Hence, antiangiogenic therapy may provide the advantage of reducing immune tolerance in large tumors, making them more vulnerable to the immune reactions. Our study implies that in the future, the combination therapy may prove effective for the treatment of patients with advanced HCC.

A model of interaction: aflatoxins and hepatitis viruses in liver cancer aetiology and prevention

Hepatocellular carcinoma (HCC) is one of the most common cancers worldwide and has an extremely poor prognosis. The majority of cases occur in south-east Asia and sub-Saharan Africa where the major risk factors are chronic infection with hepatitis B and C viruses (HBV and HCV) as well as dietary exposure to aflatoxins. Aflatoxin B1, the most commonly occurring and potent of the aflatoxins is associated with a specific AGG to AGT transversion mutation at codon 249 of the p53 gene in human HCC, providing mechanistic support to a causal link between exposure and disease. Prospective epidemiological studies have shown a more than multiplicative interaction between HBV and aflatoxins in terms of HCC risk. However, the biology underlying this statistical interaction is not fully understood. There are a number of potential mechanisms including, among others: the fixation of AFB1-induced mutations in the presence of liver regeneration and hyperplasia induced by chronic HBV infection; the predisposition of HBV-infected hepatocytes to aflatoxin-induced DNA damage; an increase in susceptibility to chronic HBV infection in aflatoxin-exposed individuals; and oxidative stress exacerbated by co-exposure to aflatoxins and chronic hepatitis infection. Priorities for prevention are global HBV vaccination, primary and secondary prevention strategies against aflatoxin and the avoidance of transmission of HCV through good hygiene practices.

Cross-species hybridization of woodchuck hepatitis viral infection-induced woodchuck hepatocellular carcinoma using human, rat and mouse oligonucleotide microarrays

BACKGROUND AND AIM

We aimed to evaluate the transcriptional characteristics of viral infection-induced woodchuck hepatocellular carcinoma (HCC), to compare the use of human, rat and mouse gene arrays for cross-species hybridization, and to look into gene expression profiles in woodchuck HCC by the combined use of these arrays.

METHODS

Commercially available human, rat and mouse oligonucleotide microarrays were used to determine the gene expression profiles on the same woodchuck liver samples. Differentially expressed genes between HCC and the surrounding hepatic tissues found in the arrays were selected for quantitative reverse transcription polymerase chain reaction.

RESULTS

Despite the difference in the number of the probes from each array, the percentage of genes that were detectable was similar. Stringent microarray data analysis using both supervised and unsupervised methods identified 281 differentially expressed genes via the human array with a false discovery rate (FDR) of 0.99%, 107 genes via the rat array with an FDR of 1.85% and 78 genes via the mouse array with an FDR of 7.41%. Eleven genes were differentially changed in all three arrays that include the upregulation of NPM1, H2AFZ, EEF1G, HNRPAB, RPS18, EIF5, CKS2, ARIH1, RPS12 and RPS10, and the downregulation of EGR1. The quantitative reverse transcription polymerase chain reaction with woodchuck-specific primers confirmed the reliability of the microarray results.

CONCLUSION

This study further demonstrated the utility of cross-species hybridization of microarrays on woodchuck HCC. A combined use of three types of arrays identified more differential genes in HCC than individual arrays with the human array providing the richest information among the three arrays used.

Characterization of interleukin 8 in woodchucks with chronic hepatitis B and hepatocellular carcinoma

The eastern woodchuck, Marmota monax, represents a useful animal model to study hepatitis B virus infection in humans. However, immunological studies in this model have been impeded by a lack of basic information about the components of the immune system such as cytokines and chemokines. To clarify the role(s) of interleukin 8 (IL-8) in chronic hepatitis B and hepatocellular carcinoma (HCC) in the woodchuck model, we cloned and characterized the woodchuck IL-8 cDNA and genomic DNA. Sequence analysis revealed that the organization of the wk-IL-8 gene is similar to that of the human IL-8 gene and consists of four exons and three introns. Woodchuck IL-8 protein exhibits the conserved ELRCXC motif of IL-8 and shows 87, 82, 82 and 79% similarity with rabbit, ovine, bovine and human IL-8 proteins, respectively. The biological activity of wk-IL-8 was demonstrated using neutrophil chemotaxis assays. Wk-IL-8 could be readily detected in both tumor and non-tumor tissues with higher expression in the non-tumor tissues in most cases. The results from this study will facilitate the investigation of IL-8 in the immunopathogenesis of hepadnavirus-related diseases by the woodchuck model.

Heat-zone effect after surface application of dissecting sealer on the "in situ margin" after tumorectomy for liver tumors

BACKGROUND

Resection remains the gold standard in the treatment of liver tumors. But radiofrequency ablation allows destruction of small liver tumors. The aim of this study was to evaluate the effect of surface application of a saline-linked dissecting sealer (TL) on the tumor bed that might contain residual microscopic tumor cells after resection (in situ margin).

STUDY DESIGN

Five hepatitis-infected woodchucks bearing primary liver tumors were used. Tumors > 1 cm in diameter were removed by tumorectomy. Alternately, the in situ margins were treated or not by TL. All samples were frozen and stained with hematoxylin and eosin and nicotine adenine dinucleotide (cell viability test). The median tumor diameter was 22 mm (range 10 to 53 mm). Among 84 in situ retrieved samples, 50 were from TL-treated tumors and 34 were from untreated controls.

RESULTS

The mean (+/-SD) heat-zone area was 12.6+/-2.8 mm in TL-treated tumors and 0.6+/-0.7 mm in controls (p < 0.001). Hematoxylin and eosin and nicotine adenine dinucleotide analyses showed 70% to 98% of cell destruction inside the heat-zone area in the TL-treated samples. There were macroscopic residual tumor cells (R2 resection) in 53 samples, with a median length of tumoral tissue inside the in situ margin of 3.5 mm. Among them, the heat-zone area was considerably longer in TL-treated versus untreated controls (13.3+/-2.6 mm versus 0.7+/-0.9 mm, p < 0.001). In samples with no residual tumor cells or microscopic residual tumor cells (R0/R1; n=31), the length of the tumoral margin was similar between TL-treated and untreated controls (0.7+/-0.2 mm and 0.9+/-0.2 mm, respectively, p=NS). Compared with controls, no viable cell was visible (up to 5 mm of depth) in the in situ margins in the TL-treated samples (p < 0.05).

CONCLUSIONS

These results support the hypothesis that surface application of the TL device on the in situ margins after tumorectomy could induce a substantial heat-zone area ranging from 10 to 13 mm, inside which, on a regressive heat gradient, up to 98% of cells could be destroyed. These observations could help to reduce marginal recurrence, especially in patients requiring multiple tumorectomies or complex liver resections for malignancy.

A colorimetric assay method to measure acetyl-CoA synthetase activity: application to woodchuck model of hepatitis virus-induced hepatocellular carcinoma

A new spectrophotometric method for quantitation of acetyl-CoA synthetase (ACAS) activity is developed. It has been applied for ACAS assay in the liver tissues of a woodchuck model of hepatitis virus-induced hepatocellular carcinoma (HCC). The assay is based on the established pyrophosphate (PPi) detection system. ACAS activity is indexed by the amount of PPi, the product of ACAS reaction system of activated form of acetate (acetyl-CoA) with ACAS catalysis. PPi is determined quantitatively as the amount of chromophore formed with molybdate reagent, 1-amino-2-naphthol-4-sulfonic acid in bisulfite and 2-mercaptoethanol. PPi reacts with molybdate reagent to produce phosphomolybdate and PPi-molybdate complexes. 2-mercaptoethanol is responsible for color formation which has the peak absorbance at 580 nm. This method was sensitive from 1 to 20 nmol of PPi in a 380-mul sample (1-cm cuvette). A ten-fold excess of Pi did not interfere with the determination of PPi. To study the major metabolic pathways of imaging tracer [1-(11)C]-acetate in tumors for detection of HCC by Positron Emission Tomography (PET), the activity of one of the key enzymes involved in acetate or [1-(11)C]-acetate metabolism, ACAS was assayed by this newly developed assay in the tissue samples of woodchuck HCCs. A significant increase of ACAS activity was observed in the liver tissues of woodchuck HCCs as compared with neighboring regions surrounding the tumors (P<0.05). The respective ACAS activities in the subcellular locations were also significantly higher in HCCs than in the surrounding tissues (P<0.05) (total soluble fraction: 876.61+/-34.64 vs. 361.62+/-49.97 mU/g tissue; cytoplasmic fraction: 1122.02+/-112.39 vs. 732.32+/-84.44 mU/g tissue; organelle content: 815.79+/-100.77 vs. 547.91+/-97.05 mU/ g tissue; sedimentable fragment: 251.92+/-51.56 vs. 90.94+/-18.98 mU/ g tissue). The finding suggests an increase in ACAS activity in the liver cancer of woodchuck models of HCC as compared to that in the normal woodchuck liver. The developed assay is rapid, simple and accurate and is suitable for the investigation of ACAS activity under physiologic and pathophysiologic conditions.

The woodchuck as an animal model for pathogenesis and therapy of chronic hepatitis B virus infection

This review describes the woodchuck and the woodchuck hepatitis virus (WHV) as an animal model for pathogenesis and therapy of chronic hepatitis B virus (HBV) infection and disease in humans. The establishment of woodchuck breeding colonies, and use of laboratory-reared woodchucks infected with defined WHV inocula, have enhanced our understanding of the virology and immunology of HBV infection and disease pathogenesis, including major sequelae like chronic hepatitis and hepatocellular carcinoma. The role of persistent WHV infection and of viral load on the natural history of infection and disease progression has been firmly established along the way. More recently, the model has shed new light on the role of host immune responses in these natural processes, and on how the immune system of the chronic carrier can be manipulated therapeutically to reduce or delay serious disease sequelae through induction of the recovery phenotype. The woodchuck is an outbred species and is not well defined immunologically due to a limitation of available host markers. However, the recent development of several key host response assays for woodchucks provides experimental opportunities for further mechanistic studies of outcome predictors in neonatal- and adult-acquired infections. Understanding the virological and immunological mechanisms responsible for resolution of self-limited infection, and for the onset and maintenance of chronic infection, will greatly facilitate the development of successful strategies for the therapeutic eradication of established chronic HBV infection. Likewise, the results of drug efficacy and toxicity studies in the chronic carrier woodchucks are predictive for responses of patients chronically infected with HBV. Therefore, chronic WHV carrier woodchucks provide a well-characterized mammalian model for preclinical evaluation of the safety and efficacy of drug candidates, experimental therapeutic vaccines, and immunomodulators for the treatment and prevention of HBV disease sequelae.

Hexokinase and glucose-6-phosphatase activity in woodchuck model of hepatitis virus-induced hepatocellular carcinoma

2-Deoxy-2-[(18)F]fluoro-D-glucose ([(18)F] FDG) is used for PET imaging of woodchuck (Marmota monax) model of hepatocellular carcinoma (HCC). The usefulness of FDG on this animal model needs to be validated according to the hypothesized mechanisms. In this study, two key enzymes involved in glucose or [(18)F] FDG metabolism, hexokinase (HK) and glucose-6-phophatase (G6Pase), were examined for their enzymatic activities in the woodchuck models of HCC, which has not been studied before. After dynamic PET scans, woodchuck liver tissue samples were harvested and the homogenate was centrifuged. The supernatant was used for HK activity assay and the microsomal pellet was used for G6Pase assay. HK and G6Pase activities were measured by means of colorimetric reactions via kinetic and end-point assays, respectively. Total protein content was measured by the Bradford method and used to normalize all enzyme activities. HK and G6Pase activities in woodchuck HCC will be used to correlate with in vivo PET imaging data. The woodchuck model of HCC had significantly increased levels of HK in the livers compared to the age-matching healthy woodchuck (7.96 +/- 1.27 vs. 2.74 +/- 0.66 mU/mg protein, P < 0.01) and significantly decreased levels of G6Pase compared to healthy woodchuck (40.35 +/- 19.28 vs. 237.01 +/- 17.32 mU/mg protein, P < 0.01), reflecting an increase in glycolysis. In addition, significant differences were found in HK and G6Pase activities between HCC liver region (HK: 7.96 +/- 1.27 mU/mg protein; G6Pase: 40.35 +/- 19.28 mU/mg protein) and surrounding normal liver region (HK: 2.98 +/- 0.92 mU/mg protein; G6Pase: 140.87 +/- 30.62 mU/mg protein) in the same woodchuck model of HCC (P < 0.01). Our study demonstrated an increased HK activity and a decreased G6Pase activity in liver of the woodchuck models of HCC as compared to normal woodchuck liver.

Hepatocellular carcinoma in the woodchuck model of hepatitis B virus infection

The Eastern woodchuck ( Marmota monax ) harbors a DNA virus (Woodchuck hepatitis virus [WHV]) that is similar in structure and replicative life cycle to the human hepatitis B virus (HBV). Like HBV, WHV infects the liver and can cause acute and chronic hepatitis. Furthermore, chronic WHV infection in woodchucks usually leads to development of hepatocellular carcinoma (HCC) within the first 2-4 years of life. The woodchuck model has been important in the preclinical evaluation of safety and efficacy of the antiviral drugs now in use for treatment of HBV infection and continues to serve as an important, predictive model for innovative forms of therapy of hepatitis B using antiviral nucleosides and immune response modifiers alone or in combination. Almost all woodchucks that become chronic WHV carriers after experimental neonatal inoculation develop HCC with a median HCC-free survival of 24 months and a median life expectancy of 30-32 months. The woodchuck model of viral-induced HCC has been used effectively for the development of new imaging agents for enhancement of detection of hepatic neoplasms by ultrasound and magnetic resonance imaging. The chemoprevention of HCC using long-term antiviral nucleoside therapy has been shown in the woodchuck, and "proof of principal" has been established for some of the innovative, molecular methods for treatment of HCC. The model is available for fundamental investigations of the viral and molecular mechanisms responsible for hepatocarcinogenesis and should have substantial value for future development of innovative methods for chemoprevention and gene therapy of human HCC.

Integration of woodchuck hepatitis and N-myc rearrangement determine size and histologic grade of hepatic tumors

Integrations of woodchuck hepatitis virus (WHV) DNA and rearrangements of the N-myc 2 gene have been detected frequently in hepatocellular carcinoma (HCC) of Eastern woodchucks (Marmota monax) chronically infected with WHV. Fifty-five hepatocellular neoplasms and matched nontumor hepatic tissue specimens obtained postmortem from 13 chronic WHV carriers were analyzed and the frequency of WHV DNA integrations and of N-myc rearrangements compared in tumors of different size and histologic grade. Four small tumor nodules were classified histologically as adenomas and integrated sequences of WHV DNA were detected in two of the four tumor nodules. In one of the two nodules, there was evidence of N-myc rearrangement. Fifty-one neoplasms were classified as HCC. Seven were grade 1 HCCs. WHV DNA integrations were demonstrated in 43% but none had N-myc rearrangements. Twenty grade 2 HCCs had WHV DNA integrations in 80% and in 38% N-myc rearrangements were present. Twenty-four grade 3 HCCs had integrations of WHV DNA in 79% and N-myc rearrangements in 74%. In two other grade 3 HCCs, rearrangements of N-myc were detected in the absence of WHV DNA integrations. The 12 largest tumors in the series all were grade 2 or 3 HCCs, and in 83%, both WHV DNA integrations and N-myc rearrangements were demonstrated. In conclusion, molecular changes observed in this study suggest a progression of genetic alterations providing either a significant proliferative stimulation and/or a growth advantage in hepatocarcinogenesis of woodchucks with chronic WHV infection.

Gene therapy of hepatocarcinoma: a long way from the concept to the therapeutical impact

Hepatocellular carcinoma (HCC), the most prevalent histological form of primary liver cancer is one of the most frequent cancer worldwide. This pathology still requires the development of new therapeutical approaches. Gene therapy strategies focusing on the genetic manipulation of accessory cells involved in the immune reaction against cancer cells, or on the direct transduction of tumor cells with transgenes able to "suicide" cancer cells have been largely developed for more than ten years.

Hepatoma cell-specific ganciclovir-mediated toxicity of a lentivirally transduced HSV-TkEGFP fusion protein gene placed under the control of rat alpha-fetoprotein gene regulatory sequences

Suicide gene therapy combining herpes simplex virus thymidine kinase gene transfer and ganciclovir administration can be envisioned as a powerful therapeutical approach in the treatment of hepatocellular carcinoma; however, safety issues regarding transgene expression in parenchyma cells have to be addressed. In this study, we constructed LATKW, a lentiviral vector expressing the HSV-TkEGFP gene placed under the control of the promoter elements that control the expression of the rat alpha-fetoprotein, and assayed its specific expression in vitro in hepatocarcinoma and nonhepatocarcinoma human cell lines, and in epidermal growth factor stimulated human primary hepatocytes. Using LATKW, a strong expression of the transgene was found in transduced hepatocarcinoma cells compared to a very low expression in nonhepatocarcinoma human cell lines, as assessed by Northern blot, RT-PCR, FACS analysis and ganciclovir-mediated toxicity assay, and no expression was found in lentivirally transduced normal human hepatocytes. Altogether, these results demonstrate the possibility to use a lentivirally transduced expression unit containing the rat alpha-fetoprotein promoter to restrict the HSV-TK-mediated induced GCV sensitivity to human hepatocarcinoma cells.

Immunotherapy of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the third leading cause of cancer death, with over a million new cases annually. It is generally advanced upon detection due to underlying liver disease, which further complicates treatment. Most of the therapeutic strategies in current use (surgery, transplantation, irradiation or chemotherapy) are either palliative or only of benefit to a small percentage of patients. This article reviews the biology of HCC, including many of the molecular changes and mechanisms leading to HCC development. This article discusses the recent innovative strategies to interfere with the progression of HCC, including novel gene therapy strategies. The most recent data supporting the use of immunotherapy for hepatocellular cancer is reviewed in detail.

Antiviral activity of beta-L-2',3'-dideoxy-2',3'-didehydro-5-fluorocytidine in woodchucks chronically infected with woodchuck hepatitis virus

The L-nucleoside analog beta-L-2',3'-dideoxy-2',3'-didehydro-5-fluorocytidine (beta-L-Fd4C) was first shown to exhibit potent activity against hepatitis B virus (HBV) in tissue culture and then to significantly inhibit viral spread during acute infection in the duck HBV model (F. Le Guerhier et al., Antimicrob. Agents Chemother. 44:111-122, 2000). We have therefore examined its antiviral activity in a mammalian model of chronic HBV infection, the woodchuck chronically infected with woodchuck hepatitis virus (WHV). Side-by-side comparison of beta-L-Fd4C and lamivudine administered intraperitoneally during short-term and long-term protocols demonstrated a more profound inhibition of viremia in beta-L-Fd4C-treated groups. Moreover, beta-L-Fd4C induced a marked inhibition of intrahepatic viral DNA synthesis compared with that induced by lamivudine. Nevertheless, covalently closed circular (CCC) DNA persistence explained the lack of clearance of infected hepatocytes expressing viral antigens and the relapse of WHV replication after drug withdrawal. Liver histology showed a decrease in the inflammatory activity of chronic hepatitis in woodchucks receiving beta-L-Fd4C. An electron microscopy study showed the absence of ultrastructural changes of hepatic mitochondria, biliary canaliculi, and bile ducts. However, a loss of weight was observed in all animals, whatever the treatment, as was a transient skin pigmentation in all woodchucks during beta-L-Fd4C treatment. There was no evidence that lamivudine or beta-L-Fd4C could prevent the development of hepatocellular carcinoma with the protocols used. These results indicate that beta-L-Fd4C exhibits a more potent antiviral effect than lamivudine in the WHV model but was not able to eradicate CCC DNA and infected cells from the liver at the dosage and with the protocol used.

Large nontransplanted hepatocellular carcinoma in woodchucks: treatment with adenovirus-mediated delivery of interleukin 12/B7.1 genes

BACKGROUND

Cytokine-based gene therapy strategies efficiently stimulate immune responses against many established transplanted tumors, leading to rejection of the tumor. In this study, we investigated the therapeutic potential of cancer immunotherapy in a clinically more relevant model, woodchucks with primary hepatocellular carcinomas induced by woodchuck hepatitis virus.

METHODS

Large (2-5 cm), established intrahepatic tumors were given an injection once with 1 x 10(9) plaque-forming units of AdIL-12/B7.1, an adenovirus vector carrying genes for murine interleukin 12 and B7.1, or of AdEGFP, the control virus, and regression of the tumors was then monitored. Five animals were used in total.

RESULTS

In four tumor-bearing animals, the antitumor response was assessed by autopsy and histologic analysis within 1-2 weeks after treatment. In all animals treated with AdIL-12/B7.1 therapy versus AdEGFP therapy, we observed substantial tumor regression (P =.006; two-sided unpaired Student's t test) accompanied by a massive infiltration of T lymphocytes. These tumors also contained increased levels of CD4(+) and CD8(+) T cells and interferon gamma (IFN gamma). In continuously growing tumor nodules given an injection of the control virus or in nontumoral liver, no such effects (i.e., tumor regression and increased levels of CD4(+) and CD8(+) T cells and IFN gamma) were detected. In the fifth animal, monitored for long-term antitumor efficacy by magnetic resonance imaging (MRI) after intratumoral vector administration by MRI guidance, the tumor was almost completely eliminated (> or = 95%) 7 weeks after treatment.

CONCLUSION

Adenovirus vector-based immunotherapy appears to be an effective treatment of large nontransplanted (orthotopic) tumors that acquire malignant characteristics in a stepwise process, reflecting the real-world scenario of hepatocellular carcinoma in humans.

Hepatocellular carcinoma

Hepatocellular carcinoma (HCC) for most patients is a terminal complication of chronic inflammatory and fibrotic liver disease. With regrettably few exceptions, treatment is largely palliative, and long-term survival is rare. However, the major causes of HCC worldwide are known and preventable. Hepatitis B and C exist only in man; the viruses have no known non-human reservoirs. Transmission of the viruses can be interrupted by vaccination against hepatitis B virus infection and improvements in medical techniques for hepatitis C, for which no vaccine has yet been developed.