Higher susceptibility to aflatoxin B(1)-related hepatocellular carcinoma in glycine N-methyltransferase knockout mice

Advances in experimental animal models of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a common malignant tumor with insidious early symptoms, easy metastasis, postoperative recurrence, poor drug efficacy, and a high drug resistance rate when surgery is missed, leading to a low 5-year survival rate. Research on the pathogenesis and drugs is particularly important for clinical treatment. Animal models are crucial for basic research, which is conducive to studying pathogenesis and drug screening more conveniently and effectively. An appropriate animal model can better reflect disease occurrence and development, and the process of anti-tumor immune response in the human body. This review summarizes the classification, characteristics, and advances in experimental animal models of HCC to provide a reference for researchers on model selection.

Chemical Biopsy for GNMT as Noninvasive and Tumorigenesis-Relevant Diagnosis of Liver Cancer

Early diagnosis of hepatocellular carcinoma (HCC) is difficult; the lack of convenient biomarker-based diagnostic modalities renders high-risk HCC patients burdened by life-long periodical examinations. Here, a new chemical biopsy approach was developed for noninvasive diagnosis of HCC using urine samples. Bioinformatic screening for tumor suppressors yielded glycine N-methyltransferase (GNMT) as a biomarker with clinical relevance to HCC tumorigenesis. A liquid chromatography-mass spectrometry (LC-MS)-based chemical biopsy detecting nonradioactive ¹³C-sarcosine from ¹³C-glycine was designed to noninvasively assess liver GNMT activity extrahepatically. ¹³C-Sarcosine showed a strong correlation with GNMT in normal and cancerous liver cells. In an autochthonous animal model developing visible cancer nodules at 17 weeks, the urinary ¹³C-sarcosine chemical biopsy exhibited notable changes as early as 8 weeks, showing significant correlations with liver GNMT and molecular pathological changes. Our chemical biopsy approach should facilitate early and noninvasive diagnosis of HCC, with direct relevance to tumorigenesis, which can be straightforwardly applied to other diseases.

Nuclear localization dictates hepatocarcinogenesis suppression by glycine N-methyltransferase

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GNMT gene expression contributes to determine hepatocellular carcinoma (HCC) prognosis.

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GNMT expression is genetically determined.

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Nuclear GNMT binds to CYP1A1, PREX2, PARP1, and NFKB gene promoters and strongly inhibits their expression.

Background

GNMT (glycine N-methyltransferase) is a tumor suppressor gene, but the mechanisms mediating its suppressive activity are not entirely known.

Methods

We investigated the oncosuppressive mechanisms of GNMT in human hepatocellular carcinoma (HCC). GNMT mRNA and protein levels were evaluated by quantitative RT-PCR and immunoblotting. GNMT effect in HCC cell lines was modulated through GNMT cDNA induced overexpression or anti-GNMT siRNA transfection.

Results

GNMT was expressed at low level in human HCCs with a better prognosis (HCCB) while it was almost absent in fast-growing tumors (HCCP). In HCCB, the nuclear localization of the GNMT protein was much more pronounced than in HCCP. In Huh7 and HepG2 cell lines, GNMT forced expression inhibited the proliferation and promoted apoptosis. At the molecular level, GNMT overexpression inhibited the expression of CYP1A (Cytochrome p450, aromatic compound-inducible), PREX2 (Phosphatidylinositol-3,4,5-trisphosphate-dependent Rac exchange factor 2), PARP1 [Poly (ADP-ribose) polymerase 1], and NFKB (nuclear factor-kB) genes. By chromatin immunoprecipitation, we found GNMT binding to the promoters of CYP1A1, PREX2, PARP1, and NFKB genes resulting in their strong inhibition. These genes are implicated in hepatocarcinogenesis, and are involved in the GNMT oncosuppressive action.

Conclusion

Overall, the present data indicate that GNMT exerts a multifaceted suppressive action by interacting with various cancer-related genes and inhibiting their expression.

Tumor suppressor gene glycine N-methyltransferase and its potential in liver disorders and hepatocellular carcinoma

Glycine N-methyltransferase is a protein with many functions. In addition to catalyzing the production of sarcosine in the one carbon metabolism pathway, it plays a role in the detoxification of environmental carcinogens such as benzo[a]pyrene, aflatoxin B1, and aristocholic acid. There is also increasing evidence suggesting a role of GNMT deficiency in liver carcinogenesis. In this review, we discuss the role of GNMT in the detoxification of xenobiotics and the mechanism of GNMT suppression during liver tumorigenesis. The protective role of GNMT in the liver allows GNMT to not only serve as a marker of liver disease, but also potentially be applied in the treatment of liver disorders and hepatocellular carcinoma. We describe the potential use of GNMT in gene therapy and we introduce the development of a GNMT promoter reporter assay that can be used to screen medicinal drugs and herbal libraries for natural compounds with anti-cancer properties.

Dysregulated transmethylation leading to hepatocellular carcinoma compromises redox homeostasis and glucose formation

Objective

The loss of liver glycine N-methyltransferase (GNMT) promotes liver steatosis and the transition to hepatocellular carcinoma (HCC). Previous work showed endogenous glucose production is reduced in GNMT-null mice with gluconeogenic precursors being used in alternative biosynthetic pathways that utilize methyl donors and are linked to tumorigenesis. This metabolic programming occurs before the appearance of HCC in GNMT-null mice. The metabolic physiology that sustains liver tumor formation in GNMT-null mice is unknown. The studies presented here tested the hypothesis that nutrient flux pivots from glucose production to pathways that incorporate and metabolize methyl groups in GNMT-null mice with HCC.

Methods

²H/¹³C metabolic flux analysis was performed in conscious, unrestrained mice lacking GNMT to quantify glucose formation and associated nutrient fluxes. Molecular analyses of livers from mice lacking GNMT including metabolomic, immunoblotting, and immunochemistry were completed to fully interpret the nutrient fluxes.

Results

GNMT knockout (KO) mice showed lower blood glucose that was accompanied by a reduction in liver glycogenolysis and gluconeogenesis. NAD⁺ was lower and the NAD(P)H-to-NAD(P)⁺ ratio was higher in livers of KO mice. Indices of NAD⁺ synthesis and catabolism, pentose phosphate pathway flux, and glutathione synthesis were dysregulated in KO mice.

Conclusion

Glucose precursor flux away from glucose formation towards pathways that regulate redox status increase in the liver. Moreover, synthesis and scavenging of NAD⁺ are both impaired resulting in reduced concentrations. This metabolic program blunts an increase in methyl donor availability, however, biosynthetic pathways underlying HCC are activated.

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Loss of glycine N-methyltransferase results in hepatocellular carcinoma.

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Metabolic reprogramming ensues to attenuate the increased S-adenosylmethionine.

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The metabolic changes include dysregulated liver NAD⁺ homeostasis and redox state.

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Liver glucose formation is reduced and precursors directed to biosynthetic pathways.

Induction of GNMT by 1,2,3,4,6-penta-O-galloyl-beta-D-glucopyranoside through proteasome-independent MYC downregulation in hepatocellular carcinoma

Glycine-N-methyl transferase (GNMT) a tumor suppressor for hepatocellular carcinoma (HCC) plays a crucial role in liver homeostasis. Its expression is downregulated in almost all the tumor tissues of HCC while the mechanism of this downregulation is not yet fully understood. Recently, we identified 1,2,3,4,6-penta-O-galloyl-beta-D-glucopyranoside (PGG) as a GNMT promoter enhancer compound in HCC. In this study, we aimed to delineate the mechanism by which PGG enhances GNMT expression and to investigate its effect on GNMT suppression in HCC. Microarray and pathway enrichment analysis revealed that MYC was a major target of PGG. PGG suppressed MYC mRNA and protein expression in Huh7 and Hep G2 cells in a dose- and time-dependent fashion. Furthermore, MYC expression was also reduced in xenograft tumors in PGG treated mice. Moreover, shRNA-mediated knocked-down or pharmacological inhibition of MYC resulted in a significant induction of GNMT promoter activity and endogenous GNMT mRNA expression in Huh7 cells. In contrast, overexpression of MYC significantly inhibited GNMT promoter activity and endogenous GNMT protein expression. In addition, antibodies against MYC effectively precipitated the human GNMT promoter in a chromatin immunoprecipitation assay. Lastly, GNMT expression was negatively correlated with MYC expression in human HCC samples. Interestingly, PGG not only inhibited MYC gene expression but also promoted MYC protein degradation through proteasome-independent pathways. This work reveals a novel anticancer mechanism of PGG via downregulation of MYC expression and establishes a therapeutic rationale for treatment of MYC overexpressing cancers using PGG. Our data also provide a novel mechanistic understanding of GNMT regulation through MYC in the pathogenesis of HCC.

mTOR Activation in Liver Tumors Is Associated with Metabolic Syndrome and Non-Alcoholic Steatohepatitis in Both Mouse Models and Humans

Non-alcoholic steatohepatitis (NASH) can cause liver fibrosis and cirrhosis, with final progression to hepatocellular carcinoma (HCC) in some cases. Various factors have been suggested to be involved in the development of NASH. Considering the many possible contributing factors, we postulated that mechanisms of progression from NASH to HCC could differ depending on the risk factors. In the present study, we applied two mouse models of NASH⁻HCC and performed histopathological and proteome analyses of mouse liver tumors. Furthermore, to compare the mechanisms of NASH⁻HCC progression in mice and humans, we investigated HCCs in humans with a background of metabolic syndrome and NASH, as well as HCCs associated with hepatitis virus infection by immunohistochemistry. It was demonstrated that upstream regulators associated with the mammalian target of rapamycin (mTOR) pathway were altered in liver tumors of mice with metabolic syndrome characteristics (TSOD mice) using proteome analysis. Immunohistochemical analysis showed that mTOR was characteristically phosphorylated in liver tumors of TSOD mice and HCCs from metabolic syndrome cases in humans. These results indicated that the mTOR pathway is characteristically activated in liver tumors with metabolic syndrome and NASH, unlike liver tumors with other etiologies.

Glycine N-methyltransferase deletion in mice diverts carbon flux from gluconeogenesis to pathways that utilize excess methionine cycle intermediates

Glycine N-methyltransferase (GNMT) is the most abundant liver methyltransferase regulating the availability of the biological methyl donor, S-adenosylmethionine (SAM). Moreover, GNMT has been identified to be down-regulated in hepatocellular carcinoma (HCC). Despite its role in regulating SAM levels and association of its down-regulation with liver tumorigenesis, the impact of reduced GNMT on metabolic reprogramming before the manifestation of HCC has not been investigated in detail. Herein, we used ²H/¹³C metabolic flux analysis in conscious, unrestrained mice to test the hypothesis that the absence of GNMT causes metabolic reprogramming. GNMT-null (KO) mice displayed a reduction in blood glucose that was associated with a decline in both hepatic glycogenolysis and gluconeogenesis. The reduced gluconeogenesis was due to a decrease in liver gluconeogenic precursors, citric acid cycle fluxes, and anaplerosis and cataplerosis. A concurrent elevation in both hepatic SAM and metabolites of SAM utilization pathways was observed in the KO mice. Specifically, the increase in metabolites of SAM utilization pathways indicated that hepatic polyamine synthesis and catabolism, transsulfuration, and de novo lipogenesis pathways were increased in the KO mice. Of note, these pathways utilize substrates that could otherwise be used for gluconeogenesis. Also, this metabolic reprogramming occurs before the well-documented appearance of HCC in GNMT-null mice. Together, these results indicate that GNMT deletion promotes a metabolic shift whereby nutrients are channeled away from glucose formation toward pathways that utilize the elevated SAM.

Glycine N-methyltransferase inhibits aristolochic acid nephropathy by increasing CYP3A44 and decreasing NQO1 expression in female mouse hepatocytes

Plants containing aristolochic acids (AA) are nephrotoxins. Glycine N-methyltransferase (GNMT) acts to bind environmental toxins such as benzo(a)pyrene and aflatoxin B1, translocate into nucleus, and alter hepatic metabolism. This study aims to determine the role of GNMT in AA-induced nephropathy. We established an AA nephropathy mouse model and found that AA type I (AAI)-induced nephropathy at a lower concentration in male than in female mice, implying sex differences in AAI resistance. Microarray analysis and AAI-treated mouse models showed that GNMT moderately reduced AAI-induced nephropathy by lowering the upregulated level of NQO1 in male, but significantly improved the nephropathy additionally by increasing Cyp3A44/3A41 in female. The protective effects of GNMT were absent in female GNMT knockout mice, in which re-expression of hepatic GNMT significantly decreased AAI-induced nephropathy. Mechanism-wise, AAI enhanced GNMT nuclear translocation, resulting in GNMT interaction with the promoter region of the genes encoding Nrf2 and CAR/PXR, the transcription factors for NQO1 and CYP3A44/3A41, respectively. Unlike the preference for Nrf2/NQO1 transcriptions at lower levels of GNMT, overexpression of GNMT preferred CAR/PXR/CYP3A44/3A41 transcriptions and alleviated kidney injury upon AAI treatment. In summary, hepatic GNMT protected mice from AAI nephropathy by enhancing CAR/PXR/CYP3A44/3A41 transcriptions and reducing Nrf2/NQO1 transcriptions.

HAfTs are novel lncRNA transcripts from aflatoxin exposure

The transcriptome can reveal insights into precancer biology. We recently conducted RNA-Seq analysis on liver RNA from male rats exposed to the carcinogen, aflatoxin B1 (AFB1), for 90 days prior to liver tumor onset. Among >1,000 differentially expressed transcripts, several novel, unannotated Cufflinks-assembled transcripts, or HAfTs (Hepatic Aflatoxin Transcripts) were found. We hypothesized PCR-cloning and RACE (rapid amplification of cDNA ends) could further HAfT identification. Sanger data was obtained for 6 transcripts by PCR and 16 transcripts by 5’- and 3’-RACE. BLAST alignments showed, with two exceptions, HAfT transcripts were lncRNAs, >200nt without apparent long open reading frames. Six rat HAfT transcripts were classified as ‘novel’ without RefSeq annotation. Sequence alignment and genomic synteny showed each rat lncRNA had a homologous locus in the mouse genome and over half had homologous loci in the human genome, including at least two loci (and possibly three others) that were previously unannotated. While HAfT functions are not yet clear, coregulatory roles may be possible from their adjacent orientation to known coding genes with altered expression that include 8 HAfT-gene pairs. For example, a unique rat HAfT, homologous to Pvt1, was adjacent to known genes controlling cell proliferation. Additionally, PCR and RACE Sanger sequencing showed many alternative splice variants and refinements of exon sequences compared to Cufflinks assembled transcripts and gene prediction algorithms. Presence of multiple splice variants and short tandem repeats found in some HAfTs may be consequential for secondary structure, transcriptional regulation, and function. In summary, we report novel, differentially expressed lncRNAs after exposure to the genotoxicant, AFB1, prior to neoplastic lesions. Complete cloning and sequencing of such transcripts could pave the way for a new set of sensitive and early prediction markers for chemical hepatocarcinogens.

Glycine N-methyltransferase deficiency in female mice impairs insulin signaling and promotes gluconeogenesis by modulating the PI3K/Akt pathway in the liver

Background

Glycine N-methyltransferase (GNMT) is abundantly expressed in the normal liver but is down-regulated in liver cancer tissues. GNMT knockout (Gnmt−/−) mice can spontaneously develop chronic hepatitis, fatty liver, and liver cancer. We previously demonstrated that hepatic GNMT is decreased in high-fat-diet-induced type 2 diabetes mellitus, but its contribution to metabolic syndrome is unclear. Here we show that GNMT modulates key aspects of metabolic syndrome in mice.

Methods

Eleven-week-old Gnmt−/− and wild-type (WT) mice with a C57BL/6 genetic background were used in this study. The metabolic defects of GNMT deficiency were measured by glucose and insulin tolerance tests, lipid homeostasis, gluconeogenesis, and insulin signaling.

Results

Gnmt−/− mice, especially females, exhibited glucose intolerance and insulin resistance. However, their body fat and lean mass, food and water intakes, and energy expenditure did not differ from those of WT mice. In addition, glucose-stimulated insulin secretion and insulin-stimulated glucagon secretion were normal in the serum and pancreatic islets of Gnmt−/− mice. Importantly, we found that GNMT deficiency increased lipogenesis and triglycerides in the liver. The elevated triglycerides disrupted the ability of insulin to induce Akt and S6 ribosomal protein phosphorylation, and then triggered insulin resistance and gluconeogenesis in female Gnmt−/− mice.

Conclusions

Our data indicate that hepatic GNMT regulates lipid and glucose homeostasis, and provide insight into the development of insulin resistance through modulating the PI3K/Akt pathway.

Electronic supplementary material

The online version of this article (doi:10.1186/s12929-016-0278-8) contains supplementary material, which is available to authorized users.

Interaction Between Polymorphisms of IFN-γ and MICA Correlated with Hepatocellular Carcinoma

Background

We explored the relationship of interferon--γ (IFN-γ) and MHC class-I chain related gene A (MICA) genes polymorphisms with hepatocellular carcinoma (HCC) risk, and tried to determine whether the interaction existed between these two genes polymorphisms on the basis of HCC.

Material/Methods

Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method was used to detect the genotypes of the 3 single-nucleotide polymorphisms (SNPs) and to analyze the correlation of each SNP with HCC susceptibility in 120 HCC patients and 124 healthy people. The association strength between the 3 SNPs and HCC is represented with odds ratio (OR) and 95% confidence interval (95% CI). Hardy-Weinberg equilibrium (HWE) was tested by χ² test in the control group.

Results

GG genotype of IFN-γ rs2069727 polymorphism had apparently different distributions in case and control groups (P<0.05), and might confer increased risk of HCC (OR=3.40, 95%CI=1.23–9.38). Analysis of MICA rs2596542 polymorphism also yielded the same result (OR=2.90, 95%CI=1.10–7.67), as did their risk alleles. Specifically, the interaction between rs2596542 and rs2069705 polymorphisms increased the HCC risk by 1.41 times and between rs2596542 and rs2069727 polymorphisms the increased risk of HCC by 5.56 times.

Conclusions

IFN-γ rs2069727 and MICA rs2596542 polymorphisms may be related to the incidence of HCC. Interaction exists between the polymorphisms of IFN-γ and MICA, which may increase risk of HCC.

Mammalian models of chemically induced primary malignancies exploitable for imaging-based preclinical theragnostic research

Compared with transplanted tumor models or genetically engineered cancer models, chemically induced primary malignancies in experimental animals can mimic the clinical cancer progress from the early stage on. Cancer caused by chemical carcinogens generally develops through three phases namely initiation, promotion and progression. Based on different mechanisms, chemical carcinogens can be divided into genotoxic and non-genotoxic ones, or complete and incomplete ones, usually with an organ-specific property. Chemical carcinogens can be classified upon their origins such as environmental pollutants, cooked meat derived carcinogens, N-nitroso compounds, food additives, antineoplastic agents, naturally occurring substances and synthetic carcinogens, etc. Carcinogen-induced models of primary cancers can be used to evaluate the diagnostic/therapeutic effects of candidate drugs, investigate the biological influential factors, explore preventive measures for carcinogenicity, and better understand molecular mechanisms involved in tumor initiation, promotion and progression. Among commonly adopted cancer models, chemically induced primary malignancies in mammals have several advantages including the easy procedures, fruitful tumor generation and high analogy to clinical human primary cancers. However, in addition to the time-consuming process, the major drawback of chemical carcinogenesis for translational research is the difficulty in noninvasive tumor burden assessment in small animals. Like human cancers, tumors occur unpredictably also among animals in terms of timing, location and the number of lesions. Thanks to the availability of magnetic resonance imaging (MRI) with various advantages such as ionizing-free scanning, superb soft tissue contrast, multi-parametric information, and utility of diverse contrast agents, now a workable solution to this bottleneck problem is to apply MRI for noninvasive detection, diagnosis and therapeutic monitoring on those otherwise uncontrollable animal models with primary cancers. Moreover, it is foreseeable that the combined use of chemically induced primary cancer models and molecular imaging techniques may help to develop new anticancer diagnostics and therapeutics.

Pleiotropic effects of methionine adenosyltransferases deregulation as determinants of liver cancer progression and prognosis

Downregulation of liver-specific MAT1A gene, encoding S-adenosylmethionine (SAM) synthesizing isozymes MATI/III, and upregulation of widely expressed MAT2A, encoding MATII isozyme, known as MAT1A:MAT2A switch, occurs in hepatocellular carcinoma (HCC). Being inhibited by its reaction product, MATII isoform upregulation cannot compensate for MATI/III decrease. Therefore, MAT1A:MAT2A switch contributes to decrease in SAM level in rodent and human hepatocarcinogenesis. SAM administration to carcinogen-treated rats prevents hepatocarcinogenesis, whereas MAT1A-KO mice, characterized by chronic SAM deficiency, exhibit macrovesicular steatosis, mononuclear cell infiltration in periportal areas, and HCC development. This review focuses upon the pleiotropic changes, induced by MAT1A/MAT2A switch, associated with HCC development. Epigenetic control of MATs expression occurs at transcriptional and post-transcriptional levels. In HCC cells, MAT1A/MAT2A switch is associated with global DNA hypomethylation, decrease in DNA repair, genomic instability, and signaling deregulation including c-MYC overexpression, rise in polyamine synthesis, upregulation of RAS/ERK, IKK/NF-kB, PI3K/AKT, and LKB1/AMPK axis. Furthermore, decrease in MAT1A expression and SAM levels results in increased HCC cell proliferation, cell survival, and microvascularization. All of these changes are reversed by SAM treatment in vivo or forced MAT1A overexpression or MAT2A inhibition in cultured HCC cells. In human HCC, MAT1A:MAT2A and MATI/III:MATII ratios correlate negatively with cell proliferation and genomic instability, and positively with apoptosis and global DNA methylation. This suggests that SAM decrease and MATs deregulation represent potential therapeutic targets for HCC. Finally, MATI/III:MATII ratio strongly predicts patients' survival length suggesting that MAT1A:MAT2A expression ratio is a putative prognostic marker for human HCC.

The multi-functional roles of GNMT in toxicology and cancer

Although glycine N-methyltransferase (GNMT) has been discovered for five decades, its function was not elucidated until recently. In this review, we discuss the multiple roles of GNMT in toxicology and cancer. Besides catalyzing the production of methylglycine (sarcosine) in one carbon metabolism pathway, GNMT was found to be able to bind a number of polycyclic aromatic hydrocarbons and inhibit DNA adducts formation. Moreover, GNMT exerts protective effects against the cytotoxicity and carcinogenicity of benzo(a)pyrene and aflatoxin B(1) in vitro and in vivo. Occupational study showed that workers who had genotypes with higher GNMT promoter activity may have lower content of oxidative damaged DNA products in their urine. In terms of cancer, recent studies using GNMT knockout mouse models demonstrated that GNMT deficiency has high penetrance in inducing the development of steatohepatitis and hepatocellular carcinoma. In terms of the mechanism, besides dysregulation of epigenetic modification, insights have been provided by recent identification of two novel proteins interacting with GNMT-DEPTOR and NPC2. These studies suggest that GNMT not only is involved in mTOR signaling pathway, but also plays an important role in the intracellular trafficking of cholesterol. The implication of these findings to the preventive medicine and translational research will be discussed.

Non-invasive in vivo imaging for liver tumour progression using an orthotopic hepatocellular carcinoma model in immunocompetent mice

BACKGROUND

Maintenance of complex transgenic colonies and labour-intensive techniques pose significant challenges in work involving mouse models for hepatocellular carcinoma (HCC). Other animal models of unusual species are generally impractical for research purposes.

AIMS

To develop a highly reproducible orthotopic mouse model for HCC based on the murine α-foetoprotein (AFP), producing cell line Hepa1-6 and to monitor liver tumour progression via in vivo imaging, and measurement of plasma AFP.

METHODS

Intrahepatic tumour was induced following subcapsular implantation of 10(+6) Hepa1-6 cells into C57L/J mice. AFP production was examined in vitro and in vivo using immunoblotting. Three confirmatory non-invasive imaging modalities were applied to follow tumour progression over time including ultrasound biomicroscopy (UBM), micromagnetic resonance imaging (microMRI), and bioluminescence.

RESULTS

α-foetoprotein expression was confirmed both in vitro and in vivo, with increasing levels in the plasma as tumours progressed. UBM, microMRI and bioluminescence detected intrahepatic tumours to a 2 mm resolution by day 14. Sequential imaging studies demonstrated an intrahepatic pattern of disease progression with an observed median survival of 29 days. Immunosuppression of tumour-bearing mice led to a greater tumour size and decreased survival.

CONCLUSIONS

Intrahepatic implantation of Hepa1-6 as a mouse model for HCC is a highly reproducible in vivo system with tumour biology analogous to human disease and is regulated by the presence of an intact host immune system. Tumour progression may be monitored in vivo by UBM, microMRI and bioluminescence. Plasma AFP increases over time, allowing redundancy in non-invasive means of following tumour progression.

Recurrence and poor prognosis following resection of small hepatitis B-related hepatocellular carcinoma lesions are associated with aberrant tumor expression profiles of glypican 3 and osteopontin

BACKGROUND

Early detection and following appropriate treatments of hepatocellular carcinoma (HCC) is still the gold standard for favored outcome of HCC patients; nevertheless, a small portion of hepatitis B virus (HBV)-related small HCC (<5 cm) patients got poor prognosis. Furthermore, the study for small HBV-HCC was limited. Therefore, the aim of this study was to explore the potential genetic signature for HBV-related small HCC as novel prognostic factors.

METHODS

We examined expression profiles of HBV-related small HCC using an Affymetrix U133A GeneChip, evaluated differential gene expression by quantitative real-time polymerase chain reaction (qRT-PCR), and finally validated these expression patterns by immunohistochemistry (IHC).

RESULTS

A total of 57 genes were differentially expressed between tumor and normal parts (n = 20 pairs) using Affymetrix U133A chip, and 16 genes were further evaluated by qRT-PCR. The result was compatible with the finding of oligonucleotide microarray (Pearson's correlation, r = 0.87). Furthermore, the expression pattern in HCC tissue by IHC in another group of small HBV-HCC (n = 100) showed overexpression of either osteopontin (OPN) or glypican 3 (GPC3) is an independent prognostic factor for disease-free survival (DFS) in HBV-positive small HCC (P < 0.01 and 0.03, respectively). Long-term DFS and overall survival (OS) for small HBV-HCC patients with high risk (both elevated GPC3(+)/OPN(+)) were DFS 0%, OS 0%, respectively; on the other hand, DFS and OS in patients with moderate (only 1 gene elevated) or low (OPN(-)/GPC3(-)) risk were 35.0 and 46.5%, respectively.

CONCLUSIONS

Elevation of both OPN and GPC3 may act as an adverse indicator for HBV-related small HCC patients after curative resection.

Increased incidence of aflatoxin B1-induced liver tumors in hepatitis virus C transgenic mice

Viral hepatitis and aflatoxin B1 (AFB1) exposure are common risk factors for hepatocellular carcinoma (HCC). The incidence of HCC in individuals coexposed to hepatitis C (HCV) or B virus and AFB1 is greater than could be explained by the additive effect; yet, the mechanisms are poorly understood because of the lack of an animal model. Our study investigated the outcomes and mechanisms of combined exposure to HCV and AFB1. We hypothesized that HCV transgenic (HCV-Tg; expressing core, E1, E2 and p7, nucleotides 342-2771) mice will be prone to hepatocarcinogenesis when exposed to AFB1. Neonatal (7 days old) HCV-Tg or C57BL/6J wild-type (WT) mice were exposed to AFB1 (6 μg/g bw) or tricaprylin vehicle (15 μl/g bw), and male offspring were followed for up to 12 months. No liver lesions were observed in vehicle-treated WT or HCV-Tg mice. Tumors (adenomas or carcinomas) and preneoplastic lesions (hyperplasia or foci) were observed in 22.5% (9 of 40) of AFB1-treated WT mice. In AFB1-treated HCV-Tg mice, the incidence of tumorous or pretumorous lesions was significantly elevated (50%, 18 of 36), with the difference largely due to a 2.5-fold increase in the incidence of adenomas (30.5 vs. 12.5%). Although oxidative stress and steatohepatitis were observed in both AFB1-treated groups, molecular changes indicative of the enhanced inflammatory response and altered lipid metabolism were more pronounced in HCV-Tg mice. In summary, HCV proteins core, E1, E2 and p7 are sufficient to reproduce the cocarcinogenic effect of HCV and AFB1, which is a known clinical phenomenon.