Spontaneous development of hepatocellular carcinomas in the FLS mice with hereditary fatty liver

Novel insights into metabolic-associated steatotic liver disease preclinical models

Metabolic-associated steatotic liver disease (MASLD) encompasses a wide spectrum of metabolic conditions associated with an excess of fat accumulation in the liver, ranging from simple hepatic steatosis to cirrhosis and hepatocellular carcinoma. Finding appropriate tools to study its development and progression is essential to address essential unmet therapeutic and staging needs. This review discusses advantages and shortcomings of different dietary, chemical and genetic factors that can be used to mimic this disease and its progression in mice from a hepatic and metabolic point of view. Also, this review will highlight some additional factors and considerations that could have a strong impact on the outcomes of our model to end up providing recommendations and a checklist to facilitate the selection of the appropriate MASLD preclinical model based on clinical aims.

Sex difference in liver diseases: How preclinical models help to dissect the sex-related mechanisms sustaining NAFLD and hepatocellular carcinoma

Only a few preclinical findings are confirmed in the clinic, posing a critical issue for clinical development. Therefore, identifying the best preclinical models can help to dissect molecular and mechanistic insights into liver disease pathogenesis while being clinically relevant. In this context, the sex relevance of most preclinical models has been only partially considered. This is particularly significant in NAFLD and HCC, which have a higher prevalence in men when compared to pre-menopause women but not to those in post-menopausal status, suggesting a role for sex hormones in the pathogenesis of the diseases. This review gathers the sex-relevant findings and the available preclinical models focusing on both in vitro and in vivo studies and discusses the potential implications and perspectives of introducing the sex effect in the selection of the best preclinical model. This is a critical aspect that would help to tailor personalized therapies based on sex.

Experimental mouse models for translational human cancer research

The development and growth of tumors remains an important and ongoing threat to human life around the world. While advanced therapeutic strategies such as immune checkpoint therapy and CAR-T have achieved astonishing progress in the treatment of both solid and hematological malignancies, the malignant initiation and progression of cancer remains a controversial issue, and further research is urgently required. The experimental animal model not only has great advantages in simulating the occurrence, development, and malignant transformation mechanisms of tumors, but also can be used to evaluate the therapeutic effects of a diverse array of clinical interventions, gradually becoming an indispensable method for cancer research. In this paper, we have reviewed recent research progress in relation to mouse and rat models, focusing on spontaneous, induced, transgenic, and transplantable tumor models, to help guide the future study of malignant mechanisms and tumor prevention.

Genetic and Diet-Induced Animal Models for Non-Alcoholic Fatty Liver Disease (NAFLD) Research

A rapidly increasing incidence of non-alcoholic fatty liver disease (NAFLD) is noted worldwide due to the adoption of western-type lifestyles and eating habits. This makes the understanding of the molecular mechanisms that drive the pathogenesis of this chronic disease and the development of newly approved treatments of utmost necessity. Animal models are indispensable tools for achieving these ends. Although the ideal mouse model for human NAFLD does not exist yet, several models have arisen with the combination of dietary interventions, genetic manipulations and/or administration of chemical substances. Herein, we present the most common mouse models used in the research of NAFLD, either for the whole disease spectrum or for a particular disease stage (e.g., non-alcoholic steatohepatitis). We also discuss the advantages and disadvantages of each model, along with the challenges facing the researchers who aim to develop and use animal models for translational research in NAFLD. Based on these characteristics and the specific study aims/needs, researchers should select the most appropriate model with caution when translating results from animal to human.

Role of Neutrophils in the Pathogenesis of Nonalcoholic Steatohepatitis

Nonalcoholic fatty liver disease (NAFLD) includes a spectrum of liver disorders, from fatty liver to nonalcoholic steatohepatitis (NASH), cirrhosis, and hepatocellular carcinoma. Compared with fatty liver, NASH is characterized by increased liver injury and inflammation, in which liver-infiltrating immune cells, with neutrophil infiltration as a hallmark of NASH, play a critical role in promoting the progression of fatty liver to NASH. Neutrophils are the first responders to injury and infection in various tissues, establishing the first line of defense through multiple mechanisms such as phagocytosis, cytokine secretion, reactive oxygen species production, and neutrophil extracellular trap formation; however, their roles in the pathogenesis of NASH remain obscure. The current review summarizes the roles of neutrophils that facilitate the progression of fatty liver to NASH and their involvement in inflammation resolution during NASH pathogenesis. The notion that neutrophils are potential therapeutic targets for the treatment of NASH is also discussed.

Study on the hepatocellular carcinoma model with metastasis

Hepatocellular carcinoma (HCC) is one of the most common causes of cancer-related death around the world due to advanced clinical stage at diagnosis, high incidence of recurrence and metastasis after surgical treatment. It is in urgent need to create appropriate animal models to explore the mechanism, patterns, risk factors, and therapeutic strategies of HCC metastasis and recurrence. However, most of the established models lack the phenotype of invasion and metastasis in patient, or have unstable phenotype. To establish HCC models with stable metastasis phenotype requires profound understanding in cancer metastasis biology and scientific methodology. Over the past 3 decades, HCC models with stable metastasis have been extensively studied. This paper reviewed the history and development of HCC animal models and cell models, focusing on the screening and maintaining of metastatic potential and phenotype. In-depth studies using these models vastly promote the understanding of cellular and molecular mechanisms and development of therapeutic strategies on HCC metastasis.

Risk factors for hepatocellular carcinoma (HCC) in the northeast of the United States: results of a case-control study

PURPOSE

HCC incidence has been continuously rising in the US for the past 30 years. To understand the increase in HCC risk, we conducted a case-control study in Connecticut, New Jersey and part of New York City.

METHODS

Through rapid case ascertainment and random digit dialing, we recruited 673 incident HCC patients and 1,166 controls. Information on demographic and anthropometric characteristics, lifestyle factors, medical and family cancer histories, were ascertained through telephone interviews using a structured questionnaire. Saliva specimens were collected for testing hepatitis C virus (HCV) antibodies. Unconditional logistic regression models were utilized to calculate odds ratio (OR) and 95% confidence interval (CI) to determine HCC associations with risk factors.

RESULTS

The study confirmed that HCV infection and obesity were important risk factors for HCC, ORs 110 (95% CI 59.2-204) and 2.13 (95% CI 1.52-3.00), respectively. High BMI and HCV infection had synergy in association with elevated HCC risk. Patients both obese and infected with HCV had HCC detected on average nearly 10 years earlier than those with neither factor. Diabetes, cigarette smoking and heavy alcohol intake were all associated with increased risk of HCC, whereas aspirin and other NSAID use were associated with reduced risk. HCC cases tended to attain less education, with lower household incomes, unmarried, and to have had more sexual partners than the controls.

CONCLUSIONS

Individuals at risk of HCC in the US comprise a unique population with low socioeconomic status and unhealthy lifestyle choices. Given the multifactorial nature, a comprehensive approach is needed in HCC prevention.

Gene Expression Analysis of the Activating Factor 3/Nuclear Protein 1 Axis in a Non-alcoholic Steatohepatitis Mouse Model

Background

Nonalcoholic fatty liver disease/steatohepatitis (NAFLD/NASH) is a chronic liver disease related to metabolic syndrome that can progress to liver cirrhosis. The involvement of the endoplasmic reticulum (ER) stress response in NAFLD progression and the roles played by activating factor 3 (ATF3) and the downstream nuclear protein 1 (NUPR1) are poorly understood. The aim of this study was to determine the gene expression profiles around the ATF3/NUPR1 axis in relation to the development of NAFLD using novel mouse models.

Methods

Fatty liver Shionogi (FLS) mice (n = 12) as a NAFLD model and FLS-ob/ob mice (n = 28) as a NASH model were fed a standard diet. The FLS mice were sacrificed at 24 weeks of age as a control, whereas the FLS-ob/ob mice were sacrificed at 24, 36, and 48 weeks of age. Hepatic steatosis, inflammation, and fibrosis were evaluated by biochemical, histological, and gene expression analyses. The expression levels of the ER-stress related genes Jun proto-oncogene (C-jun), Atf3, Nupr1, and C/EBP homologous protein (Chop) were measured in liver tissue. Apoptosis was evaluated by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining.

Results

Control mice demonstrated hepatic steatosis alone without apparent fibrosis. On the other hand, FLS-ob/ob mice showed severe steatohepatitis at both 24 and 36 weeks of age and severe fibrosis at both 36 and 48 weeks of age. The expression levels of Atf3, Nupr-1, and C-jun significantly increased from 24 to 48 weeks of age in FLS-ob/ob mice compared with control mice. The expression level of Chop was already high in FLS mice and maintained similar levels in FLS-ob/ob mice; the expression level was consistent with the percentage of TUNEL-positive cells.

Conclusion

The ATF3/NUPR1 axis plays a pivotal role in NASH progression in association with C-jun and Chop and appears to induce apoptosis from early steatosis in the NASH model mice.

Mouse models of liver cancer: Progress and recommendations

To clarify the pathogenesis of hepatocellular carcinoma (HCC) and investigate the effects of potential therapies, a number of mouse models have been developed. Subcutaneous xenograft models are widely used in the past decades. Yet, with the advent of in vivo imaging technology, investigators are more and more concerned with the orthotopic models nowadays. Genetically engineered mouse models (GEM) have greatly facilitated studies of gene function in HCC development. Recently, GEM of miR-122 and miR-221 provided new approaches for better understanding of the in vivo functions of microRNA in hepatocarcinogenesis. Chemically induced liver tumors in animals share many of the morphological, histogenic, and biochemical features of human HCC. Yet, the complicated and obscure genomic alternation restricts their applications. In this review, we highlight both the frequently used mouse models and some emerging ones with emphasis on their merits or defects, and give advises for investigators to chose a “best-fit” animal model in HCC research.

How Useful Are Monogenic Rodent Models for the Study of Human Non-Alcoholic Fatty Liver Disease?

Improving understanding of the genetic basis of human non-alcoholic fatty liver disease (NAFLD) has the potential to facilitate risk stratification of affected patients, permit personalized treatment, and inform development of new therapeutic strategies. Animal models have been widely used to interrogate the pathophysiology of, and genetic predisposition to, NAFLD. Nevertheless, considerable interspecies differences in intermediary metabolism potentially limit the extent to which results can be extrapolated to humans. For example, human genome-wide association studies have identified polymorphisms in PNPLA3 and TM6SF2 as the two most prevalent determinants of susceptibility to NAFLD and its inflammatory component (NASH), but animal models of these mutations have had only variable success in recapitulating this link. In this review, we critically appraise selected murine monogenic models of NAFLD, NASH, and hepatocellular carcinoma (HCC) with a focus on how closely they mirror human disease.

Modeling progressive non-alcoholic fatty liver disease in the laboratory mouse

Non-alcoholic fatty liver disease (NAFLD) is the most common liver disease in the world and its prevalence is rising. In the absence of disease progression, fatty liver poses minimal risk of detrimental health outcomes. However, advancement to non-alcoholic steatohepatitis (NASH) confers a markedly increased likelihood of developing severe liver pathologies, including fibrosis, cirrhosis, organ failure, and cancer. Although a substantial percentage of NAFLD patients develop NASH, the genetic and molecular mechanisms driving this progression are poorly understood, making it difficult to predict which patients will ultimately develop advanced liver disease. Deficiencies in mechanistic understanding preclude the identification of beneficial prognostic indicators and the development of effective therapies. Mouse models of progressive NAFLD serve as a complementary approach to the direct analysis of human patients. By providing an easily manipulated experimental system that can be rigorously controlled, they facilitate an improved understanding of disease development and progression. In this review, we discuss genetically- and chemically-induced models of NAFLD that progress to NASH, fibrosis, and liver cancer in the context of the major signaling pathways whose disruption has been implicated as a driving force for their development. Additionally, an overview of nutritional models of progressive NAFLD is provided.

The FLS (fatty liver Shionogi) mouse reveals local expressions of lipocalin-2, CXCL1 and CXCL9 in the liver with non-alcoholic steatohepatitis

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) encompasses a wide spectrum of diseases, ranging from simple steatosis to nonalcoholic steatohepatitis (NASH), which carries a significant risk of progression to cirrhosis and hepatocellular carcinoma. Since NASH is a progressive but reversible condition, it is desirable to distinguish NASH from simple steatosis, and to treat NASH patients at an early stage. To establish appropriate diagnosis and therapy, the pathological mechanisms of the disease should be elucidated; however, these have not been fully clarified for both NASH and simple steatosis. This study aims to reveal the differences between simple steatosis and NASH.

METHODS

This study used fatty liver Shionogi (FLS) mice as a NASH model, for comparison with dd Shionogi (DS) mice as a model of simple steatosis. Genome-wide gene expression analysis was performed using Affymetrix GeneChip Mouse Genome 430 2.0 Array, which contains 45101 probe sets for known and predicted genes. Quantitative reverse transcription polymerase chain reaction (qRT-PCR) and immunohistochemistry were used to investigate gene expression changes and protein localizations.

RESULTS

DNA microarray analysis of the liver transcriptomes and qRT-PCR of both types of mice revealed that LCN2, CXCL1 and CXCL9 mRNAs were overexpressed in FLS mouse livers. Immunohistochemistry showed that CXCL1 protein was mainly localized to steatotic hepatocytes. CXCL9 protein-expressing hepatocytes and sinusoidal endothelium were localized in some areas of inflammatory cell infiltration. Most interestingly, hepatocytes expressing LCN2, a kind of adipokine, were localized around almost all inflammatory cell clusters. Furthermore, there was a positive correlation between the number of LCN2-positive hepatocytes in the specimen and the number of inflammatory foci.

CONCLUSIONS

Overexpression and distinct localization of LCN2, CXCL1 and CXCL9 in the liver of fatty liver Shionogi mice suggest significant roles of these proteins in the pathogenesis of NASH.

Fatty liver Shionogi-ob/ob mouse: A new candidate for a non-alcoholic steatohepatitis model

AIM

The fatty liver Shionogi (FLS) mouse develops hereditary fatty liver without obesity. The FLS-ob/ob mouse made by transferring the leptin(ob) gene demonstrates several metabolic disorders and marked fat deposition in the liver. The aim was to evaluate which mouse model, the FLS or FLS-ob/ob, is more useful for non-alcoholic steatohepatitis research.

METHODS

FLS (n = 40) and FLS-ob/ob (n = 40) mice were fed a standard diet for 12, 24, 36 and 48 weeks, and then killed. The degree of fat deposition, oxidative stress, fibrosis and apoptosis were analyzed in the liver. Hepatic mRNA expression of fibrogenic and pro-inflammatory cytokines was measured.

RESULTS

FLS mice developed hepatic steatosis and slight fibrosis without obesity between 12 and 48 weeks of age. Conversely, FLS-ob/ob mice developed severe steatosis at 12 weeks of age, and steatohepatitis with increased oxidative stress and advanced fibrosis between 24 and 36 weeks of age. At 48 weeks of age, some FLS-ob/ob but not FLS mice, progressed to cirrhosis. Transforming growth factor-β1, connective tissue growth factor and tumor necrosis factor-α mRNA expression levels were greater in FLS-ob/ob than FLS mice between 24 and 48 weeks of age. The number of apoptotic cells in the liver was greater at 12 weeks of age in FLS mice and at 48 weeks of age in FLS-ob/ob mice.

CONCLUSION

FLS-ob/ob mice developed more severe steatohepatitis with fibrosis than FLS mice, and had increased oxidative stress and apoptosis. These findings indicate that the FLS-ob/ob mouse is a more useful model for steatohepatitis research.

Insulin resistance, steatohepatitis, and hepatocellular carcinoma in a new congenic strain of Fatty Liver Shionogi (FLS) mice with the Lep(ob) gene

In order to examine the influence of obesity on metabolic disorder and liver pathogenesis of the Fatty Liver Shionogi (FLS) mouse, which develops hereditary fatty liver and spontaneous liver tumors, we established a new congenic strain named FLS-Lep(ob). The Lep(ob) gene of the C57BL/6JWakShi (B6)-Lep(ob)/Lep(ob) mouse was transferred into the genome of the FLS mouse, by backcross mating. FLS-Lep(ob)/Lep(ob) mice were maintained by intercrossing between Lep(ob)-heterozygous littermates. The FLS-Lep(ob)/Lep(ob) mice of both sexes developed remarkable hyperphagia, obesity and type 2 diabetes mellitus. At 12 weeks of age, glucosuria was detected in all male and female FLS-Lep(ob)/Lep(ob) mice. Biochemical examination demonstrated that the FLS-Lep(ob)/Lep(ob) mice have severe hyperlipidemia and hyperinsulinemia. The livers of FLS-Lep(ob)/Lep(ob) mice showed microvesicular steatosis and deposition of large lipid droplets in hepatocytes throughout the lobules. The steatohepatitis-like lesions including the multifocal mononuclear cell infiltration and clusters of foamy cells were observed earlier in FLS-Lep(ob)/ Lep(ob) mice than in FLS mice. B6-Lep(ob)/Lep(ob) mice did not show hepatic inflammatory change. Furthermore, FLS-Lep(ob)/Lep(ob) mice developed multiple hepatic tumors including hepatocellular adenomas and carcinomas following steatohepatitis. In conclusion, the FLS-Lep(ob)/Lep(ob) mice developed steatohepatitis and hepatic tumors following hepatic steatosis. The FLS-Lep(ob)/Lep(ob) mouse with obesity and type 2 diabetes mellitus might be a useful animal model for human non-alcoholic steatohepatitis (NASH).

Involvement of microsomal triglyceride transfer protein in nonalcoholic steatohepatitis in novel spontaneous mouse model

BACKGROUND & AIMS

Nonalcoholic fatty liver disease (NAFLD) is currently recognized as a global health issue and encompasses a wide spectrum of entities, ranging from simple hepatic steatosis to nonalcoholic steatohepatitis (NASH). The lack of a spontaneous animal model of NASH, however, has hampered basic research in this field.

METHODS

We examined the hepatic lesions in the inbred Fatty Liver Shionogi (FLS) mouse, which exhibits type 2 diabetes, and investigated the molecular mechanism leading to NAFLD/NASH. Using vector-mediated hepatic expression of microsomal triglyceride transfer protein (MTP), a key molecule for very low density lipoprotein (VLDL) assembly and export, its contribution to the hepatic lesions as well as to glucose intolerance was examined.

RESULTS

The FLS mouse, maintained on normal chow, exhibited excessive hepatic triglyceride (TG) accumulation due to impaired VLDL secretion, and subsequently hepatic lesions comparable to NASH, with increased expression of inflammatory molecules as well as insulin resistance. Gene expression and Western blot analyses demonstrated reduced hepatic expression of MTP in the FLS mouse. Hepatic induction of MTP resulted in a reduction in hepatic TG accumulation, improvement of VLDL export, and amelioration of NASH-like lesions, as well as glucose intolerance.

CONCLUSIONS

These data suggest that the FLS mouse could serve as a spontaneous model of NASH with insulin resistance, and that reduced MTP is involved in the development of NASH, pointing towards MTP as a critical target for the prevention and treatment of NASH.

Animal models of non-alcoholic fatty liver disease: recent advances

Nonalcoholic fatty liver disease (NAFLD) refers to a wide spectrum of disorders that range from simple steatosis to steatohepatitis, advanced fibrosis, and cirrhosis. NAFLD is associated strongly with the components of metabolic syndrome, such as obesity, diabetes and insulin resistance. To date, the pathogenesis of NAFLD has not been well elucidated, and few effective therapeutic approaches for NAFLD are available. The development of animal models of NAFLD can enhance our understanding of its pathogenesis. In this article, we will review the recent advances in animal models currently available for studying NAFLD.

Effect of endurance exercise on hepatic lipid content, enzymes, and adiposity in men and women

Obesity and physical inactivity are independent risk factors for the development of nonalcoholic fatty liver disease (NAFLD). We determined the effect of endurance exercise training on hepatic lipid content and hepatic enzyme concentration in men and women. Waist circumference (WC), percent body fat (BF), computed tomography (CT) scans for liver attenuation (inverse relationship with hepatic lipid), bilirubin, alanine aminotransferase (ALT), and gamma-glutamyltransferase (GGT) plasma concentrations were measured before and after 12 weeks of endurance training in 41 lean and obese men and women. Exercise training did not change liver attenuation, body weight, percent BF, bilirubin, or ALT concentration, but did lower WC (P < 0.0001), and decreased GGT in men only (P = 0.01). Obese subjects had a lower liver attenuation than lean subjects (P = 0.04). Obese women had lower ALT than obese men (P = 0.03). GGT was lower in women before and after training. WC was positively correlated with GGT (r = 0.32, P = 0.003) and ALT (r = 0.320, P = 0.004) and negatively correlated with liver attenuation (r = -0.340, P = 0.03). Percent BF was negatively correlated with bilirubin (r = -0.374, P = 0.005). Liver attenuation was negatively correlated with ALT (r = -0.405, P = 0.003). Short-term endurance training without weight loss does not alter hepatic lipid content. There was a strong relationship between GGT/ALT and body composition (percent BF) as well as between ALT and hepatic lipid content.

Chemoprevention of spontaneous development of hepatocellular carcinomas in fatty liver Shionogi mice by a cyclooxygenase-2 inhibitor

Cyclooxygenase 2 (COX-2) and retinoid X receptor alpha (RXRalpha) are suggested to have roles in carcinogenesis. COX-2 inhibitors have been reported to suppress growth of hepatocellular carcinoma (HCC) cell lines in vitro. However, little is known about the preventive effect of these drugs on spontaneous hepatocarcinogenesis in vivo. Etodolac exists in a racemic mixture containing S- and R-etodolac. S-etodolac is responsible for COX-2 inhibitory activity and R-etodolac is related to the downregulation of RXRalpha. Here, the effect of etodolac on spontaneous development of HCC in fatty liver Shionogi mice is evaluated. Etodolac was administered at a low (2 mg/kg) or high (10 mg/kg) dose three times a week for 16 months starting at the age of 3 months. The development of HCC was suppressed slightly in the high-dose group, and suppressed markedly in the low-dose group, although the development of fatty liver was not inhibited in either group. Plasma prostaglandin E2 levels were also decreased significantly in the low-dose group, consistent with the suppression of HCC. The expression of RXRalpha and proliferating cell nuclear antigen in non-tumorous liver tissues was decreased significantly in both the low-dose and high-dose groups. These findings show that etodolac treatment at an optimum dose suppresses hepatocarcinogenesis in vivo, and may be useful for preventing the development of HCC in humans.

Fenofibrate, a peroxisome proliferator-activated receptor alpha agonist, reduces hepatic steatosis and lipid peroxidation in fatty liver Shionogi mice with hereditary fatty liver

BACKGROUND AND AIMS

The fatty liver Shionogi (FLS) mouse, a unique model for nonalcoholic fatty liver disease (NAFLD), is an inbred strain that develops spontaneous hepatic steatosis without obesity or diabetes mellitus. Peroxisome proliferator-activated receptor (PPAR) alpha controls fatty acid metabolism. In the present study, we investigated the effect of fenofibrate, a PPARalpha agonist, on hepatic steatosis in FLS mice.

METHODS

Thirteen-week-old FLS mice were fed a diet with 0.1% fenofibrate (w/w) for 12 days. The degree of hepatic steatosis was estimated by histological examination and hepatic triglyceride levels. Expression levels of genes involved in fatty acid turnover, including Acox1, Cpt1a, Fabp1, Acadl, and Acadm, were determined by Northern blot analyses. We measured levels of lipid peroxidation, glutathione, and anti-oxidative enzymes, such as superoxide dismutase, catalase, and glutathione peroxidase, in the liver.

RESULT

Treatment of FLS mice with fenofibrate improved hepatic steatosis by activating expression of genes involved in fatty acid turnover and decreased hepatic lipid peroxidation. Fenofibrate increased the activity of catalase by upregulating its mRNA levels.

CONCLUSION

Fenofibrate, which is currently used in therapy of hyperlipidemia, might also be useful for treating patients with NAFLD even in cases where NAFLD is not associated with obesity or diabetes mellitus.

High sensitivity of fatty liver Shionogi (FLS) mice to diethylnitrosamine hepatocarcinogenesis: comparison to C3H and C57 mice

The fatty liver Shionogi (FLS) mouse is a new inbred strain that spontaneously develops fatty liver with infiltration of mononuclear cells. Moreover, this mouse is known to frequently develop spontaneous hepatic cancers. Recently, human non-alcholic steatohepatitis (NASH) has been focused of attention regarding hepatocellular carcinoma. Therefore, this mouse has potential as a model for human hepatic cancer due to steatosis. It is of interest therefore, whether it exhibits elevated susceptibility not only regarding spontaneous tumor development but also to chemical hepatocarcinogens. To examine this concern, we examined diethylnitrosamine (DEN) hepatocarcinogenesis in FLS mice with 30ppm in drinking water for 26 weeks in comparison to two other strains of mice, C3H and C57. The induction of spontaneous and DEN-induced hepatic tumors was clearly increased in the FLS case, along with levels of 8-hydroxy-2'-deoxyguanosine (8-OHdG), a marker of oxidative DNA damage, as compared to the other strains, with or without DEN treatment. These results indicate that the oxidative DNA stress is intimately involved in hepatocarcinogenesis in FLS mice and provide further support for use of this mouse as a useful model for investigating hepatocarcinogenesis due to human hepatic steatosis.

Hepatocellular carcinoma and nonalcoholic steatohepatitis developing during long-term administration of valproic acid

We report a case of hepatocellular carcinoma (HCC) arising in nonalcoholic steatohepatitis (NASH). The patient, a 64-year-old man, was incidentally found to have multiple tumors in the liver when admitted for pneumonia. He had been obese, had been receiving a standard dose of valproic acid since clipping surgery for subarachnoid hemorrhage 17 years previously, and had not consumed any alcohol since the surgery. Laboratory data revealed moderate hyperlipidemia and no evidence of diabetes mellitus, hepatitis B or C infection. The patient died of hepatic insufficiency, and an autopsy was performed. A tumor, a maximum of 13 cm in diameter, grossly occupied the entire left lobe and one third of the right lobe of the liver. Histologically, moderately differentiated HCC was found with foci of poorly differentiated HCC. The non-tumorous area showed NASH with moderate bridging fibrosis, without interface hepatitis, hemochromatosis, or copper accumulation. In this patient, obesity, hyperlipidemia, and long-term treatment with valproic acid could have all been associated with induction of NASH. The present case suggests that HCC could develop in non-cirrhotic NASH liver, and that chronic inflammation in itself could be an important risk factor in the development of HCC.

Genotypic variability of hepatitis viruses associated with chronic infection and the development of hepatocellular carcinoma

At least five hepatitis viruses are known to date. Infection by enterically transmitted viruses (HAV and HEV) is generally benign compared with the disease caused by parenterally transmitted viruses (HBV, HCV, and HDV). Chronic infection by HBV is common and may evolve to cirrhosis and hepatocellular carcinoma (HCC). Eight HBV genotypes (A-H) have been described, with the South American genotype F being the most divergent. Seven clades of HDV have been described; among them, the South American genotype III is associated to a high frequency of fulminant hepatitis. HCV infection leads to a high rate of chronicity and HCC. From the six HCV genotypes, infection with genotype 1 might have the worst prognostic. Chronic infection by HCV and HBV is the major risk factor for HCC, which occurs, in the majority of the cases, as a consequence of cirrhosis. However, there is growing evidence that some HBV and HCV proteins might contribute to the generation of HCC. Some HBV and HCV variants and specific mutations within the viral genomes might be more frequently associated with the evolution to HCC. Although more studies are needed, emerging evidence indicates that it might be important to address the genetic variability of these viruses and their contribution to the development of HCC.

Obesity and hepatocellular carcinoma

Epidemiological studies have shown that obesity is a risk factor for hepatocellular carcinoma. Similar studies further indicate that diabetes is also a major risk factor. Both obesity and diabetes are frequently associated with nonalcoholic fatty liver disease, and case reports have shown progression of nonalcoholic fatty liver disease to cirrhosis and hepatocellular carcinoma. Although no study has clearly tied all of these variables together, it is likely that the association of hepatocellular carcinoma with obesity represents the progression of underlying nonalcoholic fatty liver disease to cirrhosis. The mechanism most likely involves replicative senescence of steatotic mature hepatocytes and compensatory hyperplasia of progenitor (oval) cells as a reaction to chronic injury due to ongoing nonalcoholic steatohepatitis and resultant hepatic fibrosis. Growth factors associated with chronic inflammation, type 2 diabetes, and DNA mutations as a result of lipid peroxidation probably play significant roles in clonal expansion and hepatocellular carcinoma progression. It remains unclear whether cirrhosis is a prerequisite for the development of hepatocellular carcinoma or whether hepatocellular carcinoma can develop in fatty liver in the absence of cirrhosis. However, well-documented case reports suggest that most cases of hepatocellular carcinoma arise in the setting of nonalcoholic steatohepatitis with cirrhosis. Whether therapy aimed at nonalcoholic fatty liver disease reduces the risk of hepatocellular carcinoma remains to be shown. Prophylactic measures and the role of cancer surveillance have not been adequately investigated, but current evidence suggests a risk for hepatocellular carcinoma in nonalcoholic steatohepatitis-related cirrhosis that rivals that of hepatocellular carcinoma in hepatitis C virus-related cirrhosis, particularly in older male patients.

Spontaneous tumors of small mammals

The most common tumor of guinea pigs is bronchogenic papillary adenoma; of hedgehogs is mammary gland adenocarcinoma; of hamsters is adrenal cortical adenoma; of gerbils is ovarian granulosa cell and theca cell tumors; of mice is pulmonary carcinoma; and of rats is mammary fibroadenoma. A relatively low incidence of tumors is described for chinchillas and hamsters, whereas the incidence of tumors is high for gerbils, hedgehogs, mice, and rats. Limited literature regarding neoplasia exists for prairie dogs, sugar gliders, and chinchillas.