Modification of an in vivo lung metastasis model of hepatocellular carcinoma by low dose N-nitrosomorpholine and diethylnitrosamine

Design and evaluation of collagenase-loaded nanoparticles for mechanical intervention of orthotopic hepatocellular carcinoma in rat model

Altered tissue mechanics is vital for cancer development and malignancy, whether targeting the mechanical microenvironment could retard the initiation and progression of tumor is less explored. In this study, an orthotopic hepatocellular carcinoma (HCC) rat model was constructed to reproduce the mechanical and pathophysiological microenvironment of HCC development. LpMSN@CLG, a liver-targeted (L) and pH-sensitive (p) mesoporous silica nanoparticle (MSN) encapsulated with collagenase type-I (CLG), and DOX-LpMSN@CLG, on the basis of LpMSN@CLG, encapsulated with CLG and doxorubicin (DOX), were prepared to reduce matrix stiffness by degrading collagen in liver and HCC tumor. LpMSN@CLG, and DOX-LpMSN@CLG were respectively injected (i.v.) into rats at the stage of fibrosis and HCC, resulting in decreased collagen content in liver and HCC tissue, as well as reduced matrix stiffness. In addition, LpMSN@CLG treatment at the fibrosis stage retarded HCC initiation, and DOX-LpMSN@CLG treatment inhibited the growth of HCC tumor when compared with that of the rats treated by DOX alone, suggesting that reducing matrix stiffness in HCC tumor can improve the therapeutic efficacy of DOX. Taken together, our study demonstrated that mechanical intervention of tissue stiffness by CLG-loaded nanoparticles could retard the initiation and progression of HCC, suggesting the promising of mechanical intervention of hepatocellular carcinoma.

Activity-Based Dicyanoisophorone Derivatives: Fluorogenic Toolbox Enables Direct Visualization and Monitoring of Esterase Activity in Tumor Models

The visualization and spatiotemporal monitoring of endogenous esterase activity are crucial for clinical diagnostics and treatment of liver diseases. Our research adopts a novel substrate hydrolysis-enzymatic activity (SHEA) approach using dicyanoisophorone-based fluorogenic ester substrates DCIP-R (R = R1-R6) to evaluate esterase preferences on diverse substrate libraries. Esterase-mediated hydrolysis yielded fluorescent DCIP-OH with a nanomolar detection limit in vitro. These probes effectively monitor ester hydrolysis kinetics with a turnover number of 4.73 s-1 and catalytic efficiency (kcat/Km) of 106 M-1 s-1 (DCIP-R1). Comparative studies utilizing two-photon imaging have indicated that substrates containing alkyl groups (DCIP-R1) as recognition elements exhibit enhanced enzymatic cleavage compared to those containing phenyl substitution on alkyl chains (DCIP-R4). Time-dependent variations in endogenous esterase levels were tracked in healthy and liver tumor models, especially in diethylnitrosamine (DEN)-induced tumors and HepG2-transplanted liver tumors. Overall, fluorescence signal quantifications demonstrated the excellent proficiency of DCIP-R1 in detecting esterase activity both in vitro and in vivo, showing promising potential for biomedical applications.

Investigation of the effects of Theranekron and Sorafenib treatments on carcinogenesis, apoptosis and biochemical profile in hepatocellular carcinoma in rats

This study aimed to investigate the effects of Tarantula cubensis alcohol extract (TCAE, Theranekron) and Sorafenib (S) treatments on carcinogenesis, apoptosis and biochemical profile of rats with experimentally induced hepatocellular carcinoma (HCC). In the presented study, 58 male rats were divided into 7 groups; Negative Control (NC, n = 6), NC + TCAE (NCT, n = 6), NC + Sorafenib (NCS, n = 6), Positive Control (PC, n = 10), Positive Control + TCAE (PCT, n = 10), Positive Control + Sorafenib (PCS, n = 10), Positive Control + TCAE + Sorafenib (PCTS, n = 10). The active ingredients Diethylnitrosamine (DEN, 120 mg/kg, single dose) and Nitrosomorpholine (NMOR, 50 ppm, 21 weeks orally) were used to induce HCC in rats. At the end of the experiment, the animals were euthanized under appropriate conditions and samples were collected for biochemical and pathological investigations. In the PC group, alanine aminotransferase (ALT), aspartate aminotransferase (AST) and gamma-glutamyl transpeptidase (GGT) levels were higher (p < 0.001) and urea levels were lower (p < 0.001) compared to all other groups. Treatment groups reorganized the relevant markers (ALT, AST, GGT, and urea). A significant increase was detected in Caspase-10, Caspase-3 and Granzyme-B (GrzB) (p < 0.001) in blood and Caspase-10 and GrzB (p < 0.05) in liver tissue in PCT, PCS and PCTS groups compared to the PC group. Histopathological examination revealed that the PC group showed cancer morphology, and the treatment groups caused a decrease in tumor incidence and size. Our current findings suggest that the mechanism of action of TCAE in HCC is through the NKs/CTLs-GrzB-Casp10-Casp3 signaling pathway and can be used in combination with chemotherapy drugs for the development of future drug designs.

Dynamic expression of H19 and MALAT1 and their correlation with tumor progression biomarkers in a multistage hepatocarcinogenesis model

Hepatocellular carcinoma (HCC) progresses sequentially in a stepwise pattern. Long noncoding RNA (lncRNA) can regulate the complex cascade of hepatocarcinogenesis. Our study aimed to elucidate the expression profile of H19 and MALAT1 during the different stages of hepatocarcinogenesis and the correlation between H19 and MALAT1 with the genes implicated in the carcinogenesis cascade. We employed a chemically induced hepatocarcinogenesis murine model to mimic the successive stages of human HCC development. Using real-time PCR, we analyzed the expression patterns of H19 and MALAT1, as well as the expression of biomarkers implicated in the Epithelial-Mesenchymal transition (EMT). The protein expression of the mesenchymal marker vimentin was also evaluated using immunohistochemistry in the stepwise induced stages. The histopathological evaluation of the liver tissue sections revealed significant changes during the experiment, with HCC developing at the final stage. Throughout the stages, there was a dynamic significant increase in the expression of H19 and MALAT1 compared to the normal control. Nevertheless, there was no significant difference between each stage and the preceding one. The tumor progression biomarkers (Matrix Metalloproteinases, vimentin, and β-catenin) exhibited the same trend of steadily increasing levels. However, in the case of Zinc finger E-box-binding homeobox 1 and 2 (ZEB1 and ZEB2), the significant elevation was only detected at the last stage of induction. The correlation between lncRNAs and the tumor progression biomarkers revealed a strong positive correlation between the expression pattern of H19 and MALAT1 with Matrix Metalloproteinases 2 and 9 and vimentin. Our findings imply that genetic and epigenetic alterations influence HCC development in a stepwise progressive pattern.

The distribution of liver cancer stem cells correlates with the mechanical heterogeneity of liver cancer tissue

The survival of cancer stem cells is usually limited to a specific tumor microenvironment, and this microenvironment plays a vital role in the development of tumors. The mechanical properties of the microenvironment differ in different regions of solid tumors. However, in solid tumors, whether the distribution of cancer stem cells relates to the mechanical microenvironment of different regions is still unclear. In this study, we undertook a biophysical and biochemical assessment of the changes in the mechanical properties of liver tissue during the progression of liver cancer and explored the distribution of liver cancer stem cells in liver cancer tissues. Our analysis confirmed previous observations that the stiffness of liver tissue gradually increased with the progress of fibrosis. In liver cancer tissues, we found obvious mechanical heterogeneity: the core of the tumor was soft, the invasive front tissue was the hardest, and the para-cancer tissue was in an intermediate state. Interestingly, the greatest number of liver cancer stem cells was found in the invasive front part of the tumor. We finally established that stroma stiffness correlated with the number of liver cancer stem cells. These findings indicate that the distribution of liver cancer stem cells correlates with the mechanical heterogeneity of liver cancer tissue. This result provides a theoretical basis for the development of targeted therapies against the mechanical microenvironment of liver cancer stem cells.

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.

Establishment of rat liver cancer cell lines with different metastatic potential

The gloomy outcome of liver cancer is mainly due to the high rates of metastasis and recurrence, even after curative resection for early stage liver cancer. Our study was conducted to find the animal model suitable for the study of liver cancer metastasis. In our study, two liver cancer cells were obtained from N-nitrosodiethylamine (DEN) and N-nitrosomorpholine (NMOR) induced rats, and they were cultivated, screened and cloning cultivated. Bionomics of cells was analyzed. The results show that 2 cells had different metastatic potentiality. They were named Wrh-f2 and Wrh-s2, and they have the characteristics of Hepatocellular carcinoma cells. The bionomics of 2 cells showed: (1) The chromosome karyotype analysis showed that the mode of Wrh-f2 was 80–83 and Wrh-s2 was 55–57; (2) AFP positive cytoplasmic staining was observed in Wrh-f2 and Wrh-s2. Cytokeratin (CK) 7 and CK8 positive staining was present in Wrh-f2. CK8 positive staining was present in Wrh-s2; (3) The numbers of Wrh-f2 and Wrh-s2 that passed through the Transwells were 98 ± 12 and 55 ± 15;(4) Wrh-f2 had the significant higher colony formation (78%) than Wrh-s2(8%) (P < 0.01). (5) The animal models generated solid tumours when 2 cells were inoculated to nude mouse and rat. And Wrh-f2 developed stable pulmonary metastasis. The established cell lines with different metastatic potential showed obvious advantages over liver cancer in mimicking the biological properties of malignant liver cancer tumors. It provided a suitable model for the mechanism of liver cancer metastasis in vivo and in vitro.

Genetically Engineered Mouse Models for Liver Cancer

Liver cancer is the fourth leading cause of cancer-related death globally, accounting for approximately 800,000 deaths annually. Hepatocellular carcinoma (HCC) is the most common type of liver cancer, comprising approximately 80% of cases. Murine models of HCC, such as chemically-induced models, xenograft models, and genetically engineered mouse (GEM) models, are valuable tools to reproduce human HCC biopathology and biochemistry. These models can be used to identify potential biomarkers, evaluate potential novel therapeutic drugs in pre-clinical trials, and develop molecular target therapies. Considering molecular target therapies, a novel approach has been developed to create genetically engineered murine models for HCC, employing hydrodynamics-based transfection (HT). The HT method, coupled with the Sleeping Beauty transposon system or the CRISPR/Cas9 genome editing tool, has been used to rapidly and cost-effectively produce a variety of HCC models containing diverse oncogenes or inactivated tumor suppressor genes. The versatility of these models is expected to broaden our knowledge of the genetic mechanisms underlying human hepatocarcinogenesis, allowing the study of premalignant and malignant liver lesions and the evaluation of new therapeutic strategies. Here, we review recent advances in GEM models of HCC with an emphasis on new technologies.

Liver Protective Effects of Renin-Angiotensin System Inhibition Have No Survival Benefits in Hepatocellular Carcinoma Induced By Repetitive Administration of Diethylnitrosamine in Mice

BACKGROUND:

Preclinical studies have demonstrated that renin-angiotensin system (RAS) signalling has strong tumour-promoting effects and RAS inhibition was associated with improvement in the overall survival in some cancer types including hepatocellular carcinoma (HCC).

OBJECTIVE:

We aimed to investigate the effect of angiotensin-converting enzyme inhibitors (ACEIs) or angiotensin-II-receptor blockers (ARBs) on the survival of mice with diethylnitrosamine (DEN) induced HCC.

METHODS:

HCC was induced by weekly i.p. administration of DEN. Mice were treated with sorafenib (SO) (30 mg/kg), perindopril (PE) (1 mg/kg), fosinopril (FO) (2 mg/kg), losartan (LO) (10 mg/kg), PE (1 mg/kg) + SO (30 mg/kg), FO (2 mg/kg) + SO (30 mg/kg), or LO (10 mg/kg) + SO (30 mg/kg). Survival analysis was done using the Kaplan-Meier method, and the log-rank test was used for assessing the significance of difference between groups.

RESULTS:

The administration of PE, FO and LO as monotherapy or as combined with SO resulted in marked improvement in the liver histologic picture with no impact on overall survival of mice.

CONCLUSION:

Interfering the RAS either through the inhibition of ACE or the blockade of angiotensin II type 1 (AT1) receptors has similar effects on the liver of DEN-induced HCC mice and is not associated with longer survival due to detrimental effects of DEN on other organs. Hence, repetitive administration of DEN in such models of HCC is not suitable for mortality assessment studies.

Animal models as a tool in hepatocellular carcinoma research: A Review

Cancer is the first cause of death in developed countries and the second in developing countries. Concerning the most frequent worldwide-diagnosed cancer, primary liver cancer represents approximately 4% of all new cancer cases diagnosed globally. However, among primary liver cancer, hepatocellular carcinoma is by far the most common histological subtype. Notwithstanding the health promotion and disease prevention campaigns, more than half a million new hepatocellular carcinoma cases are reported yearly, being estimated to growth continuously until 2020. Taking this scenario under consideration and the fact that some aspects concerning hepatocellular carcinoma evolution and metastasize process are still unknown, animal models assume a crucial role to understand this disease. The animal models have also provided the opportunity to screen new therapeutic strategies. The present review was supported on research and review papers aiming the complexity and often neglected chemically induced animal models in hepatocarcinogenesis research. Despite the ongoing debate, chemically induced animal models, namely, mice and rat, can provide unique valuable information on the biotransformation mechanisms against xenobiotics and apprehend the deleterious effects on DNA and cell proteins leading to carcinogenic development. In addition, taking under consideration that no model achieves all hepatocellular carcinoma research purposes, criteria to define the " ideal" animal model, depending on the researchers' approach, are also discussed in this review.

Effect of toll-like receptor 7 and 9 targeted therapy to prevent the development of hepatocellular carcinoma

BACKGROUND & AIMS

Chronic liver disease is a predisposing factor for development of hepatocellular carcinoma (HCC). Toll-like receptors play a crucial role in immunity against microbial pathogens and recent evidence suggests that they may also be important in pathogenesis of chronic liver disease. The purpose of this study was to determine whether TLR7 and TLR9 are potential targets for prevention and progression of HCC.

METHODS

Tissue microarrays containing liver samples from patients with cirrhosis, viral hepatitis and HCC were examined for expression of TLR7 and TLR9 and the data obtained was validated in liver specimens from the hospital archives. Proliferation of human HCC cell lines was studied following stimulation of TLR7 and TLR9 using agonists (imiquimod and CpG-ODN respectively) and inhibition with a specific antagonist (IRS-954) or chloroquine. The effect of these interventions was confirmed in a xenograft model and diethylnitrosamine (DEN)/nitrosomorpholine (NMOR)-induced model of HCC.

RESULTS

TLR7 and TLR9 expression was up-regulated in human HCC tissue. Proliferation of HuH7 cells in vitro increased significantly in response to stimulation of TLR7. TLR7 and TLR9 inhibition using IRS-954 or chloroquine significantly reduced HuH7 cell proliferation in vitro and inhibited tumour growth in the mouse xenograft model. HCC development in the DEN/NMOR rat model was also significantly inhibited by chloroquine (P < 0.001).

CONCLUSION

The data suggest that inhibiting TLR7 and TLR9 with IRS-954 or chloroquine could potentially be used as a novel therapeutic approach for preventing HCC development and/or progression in susceptible patients.

Oxidative stress and cell damage in a model of precancerous lesions and advanced hepatocellular carcinoma in rats

Hepatocellular carcinoma (HCC) is the third most frequent cause of cancer deaths throughout the world. This study was aimed to analyze oxidative stress and cell damage in a multistage model of liver carcinogenesis induced by diethylnitrosamine (DEN) in rats. Male Wistar rats weighing 145–150 g were divided into three groups: control, precancerous lesions (PL) (which received 100 mg DEN once a week every 6 weeks up to 28 weeks), and advanced HCC (50 mg DEN once/twice per week up to 19 weeks). Lipid peroxidation (TBARS), superoxide dismutase (SOD) activity, and expression of transforming growth factor-1 beta (TGF)-1β, endothelial and inducible nitric oxide syntahese (eNOS, iNOS), NADPH quinone oxireductase (NQO)-1, nuclear factor erythroid 2-related factor (NrF)2, kelch-like ECH-associated protein (Keap)1 and heat shock protein (HSP)70 were measured. TBARS concentration was augmented in the PL and advanced HCC groups. SOD activity, TGF-1β and Nrf2 expression were higher in animals with precancerous lesions. In advanced HCC, expression of NQO1 and iNOS increased while there was a decrease in HPS70 expression. Data obtained provide evidence for the differential activation of proteins involved in oxidative stress and cell damage during progression of carcinogenesis in an animal model of HCC.

Silencing of connexin 43 suppresses invasion, migration and lung metastasis of rat hepatocellular carcinoma cells

To reduce cancer mortality, understanding of mechanisms of cancer metastasis is crucial. We have established six rat hepatocellular carcinoma (HCC) cell lines, which exhibit differing metastatic potential to the lung after inoculation into the tail veins of nude mice. In the present experiment, we investigated the process of cell attachment to metastatic sites and possible regulating factors. One hour after inoculation, two of two HCC cell lines with high metastatic potential and one of two HCC cell lines with low metastatic potential exhibited many attached cells in the lung. One day after inoculation, lung metastatic foci were observed only with highly-metastatic cells with elevated connexin 43 (Cx43) expression as assessed by cDNA array analysis. Furthermore, 24 or 48 h after transfection of an siRNA targeting Cx43, in vitro invasion and migration were suppressed by 68% (P < 0.001) and 36% (P < 0.05) compared with control-siRNA transfected cells, despite no differences in cellular morphology, cell proliferation or apoptotic activity. Moreover, the number of metastatic nodules per lung area in nude mice was significantly (P < 0.01) reduced. In conclusion, suppression of Cx43 expression in tumor cells reduced in vitro migration and invasion capacity and in vivo metastatic ability so that Cx43 has potential as a molecular target for prevention of cancer metastasis with Cx43 overexpressing tumors.

Hepatocellular carcinoma: insight from animal models

Hepatocellular carcinoma (HCC) ranks as the third most common cause of death from cancer worldwide. Although major risk factors for the development of HCC have been defined, many aspects of the evolution of hepatocellular carcinogenesis and metastasis are still unknown. Suitable animal models are, therefore, essential to promote our understanding of the molecular, cellular and pathophysiological mechanisms of HCC and for the development of new therapeutic strategies. This Review provides an overview of animal models that are relevant to HCC development, metastasis and treatment. For HCC development, this Review focuses on transgenic mouse models of HBV and HCV infection, which provide experimental evidence that viral genes could initiate or promote liver carcinogenesis. Animal models of HCC metastasis provide platforms to elucidate the mechanisms of HCC metastasis, to study the interaction between the microenvironment and HCC invasion and to conduct intervention studies. In addition, animal models have been developed to investigate the effects of new treatment modalities. The criteria for establishing ideal HCC animal models are also discussed.

Effect of change in transporter expression on gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid-enhanced magnetic resonance imaging during hepatocarcinogenesis in rats

BACKGROUND AND AIMS

To analyze the difference in signal intensity on gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid (Gd-EOB-DTPA)-enhanced magnetic resonance imaging (MRI) among various hepatocellular nodules during hepatocarcinogenesis as correlated with the expressions of the transporters of Gd-EOB-DTPA.

METHODS

We received institutional animal review board approval prior to the commencement of all studies. Forty rats were divided into three groups. The rats in the tumor groups received N-nitrosomorpholine solution (n = 16), and rats in the cirrhosis group (thioacetamide [TAA] group) received thioacetamide solution (n = 12). As a control, the remaining 12 rats were fed normal water. Each group was divided into two sub-groups: Group 1 for Gd-EOB-DTPA-enhanced MRI (0.025 mmol Gd/kg, n =7) and Group 2 for reverse transcription-polymerase chain reaction to compare transporter (oatp1 and mrp2) expressions (n = 5 for control and TAA groups, n = 9 for tumor groups).

RESULTS

Signal enhancement of tumors decreased according to the progress of hepatocarcinogenesis. Although the relative enhancement of each tumor group was significantly lower than that of the control group (P < 0.01), and there was no significant difference between TAA, hyperplastic nodules (HPN), and HCC(well) groups. The relative enhancement of the HCC(mod) group was significantly lower than the other groups (P < 0.01). The oatp1 expression of HPN tended to be higher than those of HCC(well) and HCC(mod). The mrp2 expression of TAA was significantly higher than those of HCC(well), HCC(mod), HPN and control (P < 0.01). The mrp2 expression of HPN tended to be higher than those of HCC(well ) and HCC(mod).

CONCLUSION

It was suggested that the signal enhancement on Gd-EOB-DTPA-enhanced MRI would correlate with the transporter expression in various hepatocellular nodules during hepatocarcinogenesis.

Antitumoral activity of rapamycin mediated through inhibition of HIF-1alpha and VEGF in hepatocellular carcinoma

Rapamycin (RAPA) inhibits tumor growth and angiogenesis in hepatocellular carcinoma (HCC). The molecular mechanism underlying the antitumoral effects of RAPA remains unclear. Here we established a chemical-induced rat HCC model to investigate the signaling pathways mediating RAPA's antitumor activity. We found that RAPA exposure significantly diminished tumor growth, angiogenesis, and metastasis of HCC. Meanwhile, the antitumor drug dramatically decreased expression of HIF-1alpha and VEGF, either at mRNA or protein levels. Moreover, the low-dose of RAPA (1.5 mg/kg/day) was effective enough to markedly inhibit tumor progression of HCC. The preliminary results suggested that the antitumoral effects of RAPA might be at least partially mediated through downregulation of HIF-1alpha and VEGF, and low-dose RAPA-based regimens exhibited a promising future in treatment of HCC.

Expression and correlation of hypoxia-inducible factor-1alpha, vascular endothelial growth factor and microvessel density in experimental rat hepatocarcinogenesis

An experimental rat hepatocellular carcinoma (HCC) model was established using diethylnitrosamine and N-nitrosomorpholine to induce carcinogenesis in Sprague-Dawley rats. During hepatocarcinogenesis, seven rats were sacrificed at 0, 4, 8, 12 and 16 weeks and 10 rats were sacrificed at 20 weeks. The levels of hypoxia-inducible factor-1alpha (HIF-1alpha) and vascular endothelial growth factor (VEGF) protein and mRNA were examined by immunohistochemistry, Western blot and semi-quantitative reverse transcriptase-polymerase chain reaction at different stages in the rat HCC model. Twenty weeks after induction of hepatocarcinogenesis, the expression of HIF-1alpha and VEGF protein and mRNA significantly increased compared with week 0. Microvessel density (MVD) increased considerably once liver cancer developed. There was a significant positive correlation between MVD and both HIF-1alpha and VEGF, and between HIF-1alpha and VEGF levels. These results suggest that HIF-1alpha and VEGF play important roles in tumour occurrence and development during rat hepatocarcinogenesis, possibly through promoting tumour angiogenesis.

Both early and late stages of hepatocarcinogenesis are enhanced in Cx32 dominant negative mutant transgenic rats with disrupted gap junctional intercellular communication

Connexins are a family of transmembrane proteins essential for the gap junctions, which mediate cell-to-cell communication. Several connexins are reported to be tumor suppressors, and we have established transgenic (Tg) rats with a connexin 32 (Cx32) dominant negative mutant showing high sensitivity to early-stage diethylnitrosamine (DEN)-induced liver carcinogenesis. In this study, we carried out two independent experiments using Tg rats to further investigate the roles of disrupted Cx32 in late-stage carcinogenesis (carcinoma induction and metastasis) in the liver. In the first experiment, of 50 weeks' duration, DEN was administered at 6 weeks of age and at 26 weeks to explore the effects of carcinogen treatments at different stages. The number of hepatocellular carcinomas (HCCs) was significantly increased in Tg compared with non-Tg rats. The second experiment focused on the effects of Cx32 disruption on metastasis by HCCs induced by administration of DEN and N-nitrosomorpholine. Only Tg rats had multiple metastases of HCCs in the lung, and the development and growth of HCCs was dramatically accelerated in Tg compared to non-Tg rats. Thus, normal function of Cx32 may be essential for suppression of both early and late stages of hepatocarcinogenesis.