Early Stages Of Hepatocarcinogenesis Research Articles

Promoter occupancy of MLL1 histone methyltransferase seems to specify the proliferative and apoptotic functions of E2F1 in a tumour microenvironment

The E2F family of transcription factors are considered versatile modulators, poised at biological crossroads to execute diverse cellular functions. Despite extensive studies on E2F, the molecular mechanisms that control specific biological functions of the E2F1 transcription factor are still not fully understood. Here we have addressed the molecular underpinnings of paradoxical functions of E2F1 in a tumour microenvironment using the 'X15-myc' oncomouse model of hepatocellular carcinoma. We observed that the HBx oncoprotein of hepatitis B virus regulates E2F1 functions by interfering with its binding to Skp2 E3 ubiquitin ligase. The HBx-Skp2 interaction led to the accumulation of transcriptionally active E2F1 and histone methyltransferase mixed lineage leukemia 1 (MLL1) protein. During early stages of hepatocarcinogenesis, the increased E2F1 activity promoted cellular proliferation by stimulating the genes involved in cell cycle control and replication. However, during the late stages, E2F1 triggered replication-stress-induced DNA damage and sensitized cells to apoptotic death in a p53-independent manner. Interestingly, the different promoter occupancy of MLL1 during the early and late stages of tumour development seemed to specify the proliferative and apoptotic functions of E2F1, through its dynamic interaction with the co-activator CBP or co-repressor Brg1. Thus, the temporally regulated promoter occupancy of histone methyltransferase could be a regulatory mechanism associated with the diverse cellular functions of the E2F family of transcription factors.

Functional consequences of WNT3/Frizzled7-mediated signaling in non-transformed hepatic cells

We have previously demonstrated that WNT3 and Frizzled7 (FZD7) expression levelswere upregulated in hepatocellular carcinoma (HCC) and that they directly interact to activate the canonical Wnt/β–catenin pathway in HCC cell lines. In this study, we investigated the functional consequences of WNT3 and FZD7 expression levels in non-transformed hepatic cells to address the question of whether WNT3/FZD7-mediated signal transduction could be involved in cellular transformation. After stable transfection of WNT3 and FZD7, the activation of the Wnt/β–catenin pathway was confirmed by western blot, immunostaining and quantitative real-time reverse transcriptase–PCR (qRT–PCR) analysis in two non-transformed hepatocyte-derived cell lines. In vitro characteristics of the malignant phenotype were measured, including cell proliferation, migration, invasion and anchorage-independent growth in soft agar. Stable expression of WNT3 and FZD7 in the two cell lines led to cellular accumulation of β-catenin and expression of downstream target genes activated by this pathway. In the stable WNT3/FZD7-expressing clones, hepatic cell proliferation, migration, invasion as well as soft agar colony formation were enhanced compared with the non-transformed control cells. The epithelial–mesenchymal transition (EMT) factors, Twist, Snail and Vimentin, were increased in cells expressing WNT3 and FZD7. However, the WNT3/FZD7-expressing cells did not form tumors in vivo. We conclude that activation of the WNT3/FZD7 canonical pathway has a role in the early stages of hepatocarcinogenesis by promoting the acquisition of a malignant phenotype with features of EMT.

Bortezomib induces tumor-specific cell death and growth inhibition in hepatocellular carcinoma and improves liver fibrosis

Human hepatocellular carcinoma (HCC) is highly ubiquitinated. The ubiquitination is important to the generatation of HCC. The antitumor and antifibrosis effects of an ubiquitin-proteasome system inhibitor, bortezomib, on HCC with liver cirrhosis (LC) were analyzed in vitro and in vivo. The effect of bortezomib was analyzed in the rat hepatocarcinogenesis model using a DEN and CDAA diet (DEN/CDAA model), which shows severe LC and generation of HCC. The decrease of GST-P-positive foci and HCC were analyzed in vivo. Cell death was analyzed by cell death detection kit. Liver fibrosis was checked by sirius-red staining and α-smooth muscle actin staining. The in vitro study involved 3 HCC cell lines (HepG2, HuH7, and HLF) and primary rat and human hepatocytes. The proliferation rate of the HCC cell line was analyzed using the MTT assay and FACS analysis. The toxicity of bortezomib was checked using the LDH release assay for primary human and rat hepatocytes. In the rat hepatocarcinogenesis model, bortezomib prevented the development of preneoplastic lesions during the early stages of hepatocarcinogenesis and specifically induced cell death in HCC. Furthermore, bortezomib inhibited cell proliferation and induced tumor-specific cell death in HCC cell lines with decrease of cyclin D1 and phospho-Rb expression. Further, bortezomib showed no hepatotoxicity of primary rat and human hepatocytes, suggesting that it might be an HCC-specific drug. Bortezomib also prevented the activation of hepatic stellate cells and inhibited the liver fibrosis of the DEN/CDAA model. Bortezomib appears to be an ideal target drug for HCC with LC.

Silibinin (Milk Thistle) potentiates ethanol-dependent hepatocellular carcinoma progression in male mice

Hepatocellular carcinoma (HCC) is a global health burden with limited treatment options and poor prognosis. Silibinin, an antioxidant derived from the Milk Thistle plant (Silybum marianum), is reported to exert hepatoprotective and antitumorigenic effects in vitro and in vivo by suppressing oxidative stress and proliferation. Using a DEN-initiated mouse model of HCC, this study examined the effects of dietary silibinin supplementation alone, or in combination with chronic ethanol consumption on HCC progression. Our data demonstrate silibinin exerted marginal hepatoprotective effects in early stages of hepatocarcinogenesis but, when co-administered with ethanol, exacerbated the promotional effects of ethanol in HCC bearing mice, but only in males.

Up‐regulated aldo‐keto reductase family 1 member B10 in chronic hepatitis C: association with serum alpha‐fetoprotein and hepatocellular carcinoma

BackgroundElevated serum alpha-fetoprotein (AFP) is not only a diagnostic marker for hepatocellular carcinoma (HCC), but is also a risk factor for HCC in chronic hepatitis C patients who do not have HCC.AimThe aim was to analyse the hepatic gene expression signature in chronic hepatitis C patients with elevated AFP, who were at high risk for HCC.MethodsLiver tissue samples from 48 chronic hepatitis C patients were stratified by their serum AFP levels and analysed for gene expression profiles. The association between aldo-keto reductase family 1 member B10 (AKR1B10) expression and serum AFP was confirmed by quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR) and immunohistochemical analyses. A matched case-control study was performed to evaluate the risk of AKR1B10 expression for HCC development.ResultsDistinct hepatic gene expression patterns were demonstrated in patients with elevated AFP (≥10 ng/mL) and normal AFP (<10 ng/mL). Of the 627 differently expressed genes, the most abundantly expressed gene in patients with elevated AFP was AKR1B10 (fold change, 26.2; P < 0.001), which was originally isolated as an overexpressed gene in human HCC. The qRT-PCR and immunohistochemical studies confirmed a proportional correlation between AKR1B10 expression and serum AFP. A matched case-control study identified that AKR1B10 up-regulation (>6%) was an independent risk factor for HCC development (hazard ratio, 21.4; P = 0.001).ConclusionAKR1B10 was up-regulated in association with serum AFP, and was an independent risk factor for HCC in chronic hepatitis C patients, suggesting its possible involvement at a very early stage of hepatocarcinogenesis.

Targeting Liver Cancer: First Steps toward a miRacle?

In a recent issue of Cell, Iliopoulos and colleagues demonstrate a novel and targetable epigenetic amplification loop in hepatocellular carcinoma involving HNF4α, miR-124, IL6-R, Stat3, miR-24, and miR-629. These results establish microRNAs as novel players in early stages of hepatocarcinogenesis and as potential targets for the treatment of hepatocellular carcinoma.

RPL36 as a prognostic marker in hepatocellular carcinoma

Ribosomal proteins (RP) play key roles in the regulation of apoptosis, multidrug resistance and carcinogenesis. The aim of this study was to investigate the expression of ribosomal protein L36 (RPL36) in hepatocellular carcinoma (HCC) and to correlate it with clinicopathological parameters and clinical outcome. Liver specimens were obtained from 60 HCC patients who had undergone a partial hepatectomy. Expression of RPL36 in tumor tissue and surrounding non-tumorous tissues was evaluated on a tissue microarray by immunohistochemistry. RPL36 was expressed in 45 of 60 (75%) HCC by immunohistochemistry, but was not detected in corresponding non-tumors. RPL36 expression correlated significantly with serum levels of albumin (P= 0.044) and prothrombin time (P= 0.026), which reflect liver synthetic function. Moreover, expression of RPL36 was found to be higher in patients with early tumor stages (I/II) (P= 0.038) or without portal vein thrombosis (P= 0.005). In univariate analysis, patients with RPL36 expression revealed better overall survival (P= 0.037). By multivariate survival analysis, RPL36 expression was found to be an independent prognostic factor for overall survival (P= 0.026). Our data suggest that RPL36 may be involved in the early stage of hepatocarcinogenesis, and it can be used as an independent and potential prognostic marker for resected HCC.

Abstract 909: Activation of NF-κB and its downstream targets play a key role in the dramatic induction of hepatocarcinogenesis in metallothionein null mice

Abstract Hepatocellular Carcinoma (HCC) is one of the most prevalent cancers in the world and the third leading cause of cancer-related death. Although hepatitis C and fatty liver disease appear to be the main risk factors in most western countries other factors including alcohol, tobacco, diabetes, and other metabolic disorders can also increase the likelihood of HCC development. HCC is believed to develop through a tumor promoting mechanism involving inflammation and oxidative stress. We have previously shown that metallothionein (MT), a ubiquitously expressed free radical scavenger, is dramatically downregulated in human and rodent HCCs. To test the hypothesis that MT protects the liver from carcinogenesis by relieving oxidative stress, MT knockout (MTKO) mice were injected with Diethylnitrosamine (DEN), a potent liver carcinogen. When compared to wild-type DEN treated mice, the MTKO groups exhibited significantly higher (5-fold) incidence and an accelerated rate of hepatocarcinogenesis. Gene expression analysis at the preneoplastic stage revealed a dramatic increase in the levels of Serpine-1 in the MTKO mice, which was validated by real-time PCR. Serpine-1, a tissue glycoprotein and an active suppressor of fibrinolysis through the inhibition of tissue plasminogen activator and urokinase plasminogen activator, is also believed to increase cell migration and angiogenesis. Real-time PCR analysis of the pro-inflammatory cytokines known to induce Serpine-1 revealed substantial upregulation of TNF-α, IL-6, and IL-1β in the MTKO/DEN mice compared to the WT/DEN and untreated controls. Electrophoretic mobility shift assay confirmed differential activation of NF-κB, a downstream effector of pro-inflammatory cytokines and inducer of Serpine-1 expression, in the MTKO/DEN mice at the preneoplastic stage. These data demonstrate that Serpine-1 and NF- κB act in concert at the early stages of hepatocarcinogenesis when free radical scavenging is compromised. These data show the protective role of MT against HCC induction in a mouse model and provide the rationale for an alternate therapeutic strategy in HCC therapy. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 909. doi:10.1158/1538-7445.AM2011-909

Hepatocelluar nodules in liver cirrhosis: hemodynamic evaluation (angiography-assisted CT) with special reference to multi-step hepatocarcinogenesis

To understand the hemodynamics of hepatocellular carcinoma (HCC) is important for the precise imaging diagnosis and treatment, because there is an intense correlation between their hemodynamics and pathophysiology. Angiogenesis such as sinusoidal capillarization and unpaired arteries shows gradual increase during multi-step hepatocarcinogenesis from high-grade dysplastic nodule to classic hypervascular HCC. In accordance with this angiogenesis, the intranodular portal supply is decreased, whereas the intranodular arterial supply is first decreased during the early stage of hepatocarcinogenesis and then increased in parallel with increasing grade of malignancy of the nodules. On the other hand, the main drainage vessels of hepatocellular nodules change from hepatic veins to hepatic sinusoids and then to portal veins during multi-step hepatocarcinogenesis, mainly due to disappearance of the hepatic veins from the nodules. Therefore, in early HCC, no perinodular corona enhancement is seen on portal to equilibrium phase CT, but it is definite in hypervascular classical HCC. Corona enhancement is thicker in encapsulated HCC and thin in HCC without pseudocapsule. To understand these hemodynamic changes during multi-step hepatocarcinogenesis is important, especially for early diagnosis and treatment of HCCs.

Jun Activation Domain Binding Protein 1 is Overexpressed from the Very Early Stages of Hepatocarcinogenesis

As is known for many types of human cancers, the hepatocellular carcinoma (HCC) associated with chronic liver disease shows an obvious multistage process of tumor progression. Despite the demonstrated importance of cell-cycle regulators in tumor biology, there have only been a few studies of their role in multistep hepatocarcinogenesis. Recently, we reported that a high level of p27(Kip1) expression is evident from the very early stages of hepatocarcinogenesis. In the present study, expression of p27(Kip1) and Jun activation domain binding protein-1 (Jab1), which is a key molecule involved in posttranslational regulation of p27(Kip1), was evaluated in surgically resected specimens of 8 dysplastic nodules (DNs), 16 early HCCs, and 126 classical HCCs. Immunohistochemistry revealed no Jab1 expression in the majority of hepatocytes in noncancerous normal liver tissue and cases of chronic hepatitis or cirrhosis. In contrast, Jab1 was overexpressed in 50% (4/8) and 50% (8/16) of DNs and early HCCs, respectively, and the labeling index was increased in line with the degree of loss of differentiation in classical HCCs. Real-time quantitative reverse transcription polymerase chain reactions revealed the Jab1 mRNA levels in all tested early and well-differentiated HCCs to be increased compared with matched nontumorous liver specimens. The Spearman coefficient pointed to a high correlation between p27(Kip1) and Jab1 mRNA expression levels (P = 0.0014). Jab1 expression, as well as p27(Kip1) upregulation, is evident from the very early stages of hepatocarcinogenesis, suggesting that Jab1 could be a diagnostic marker and a treatment target for precancerous lesions and early HCCs.

Promotion of Anchorage-independent Growth by Cytoplasmic and Nuclear Histone Deacetylase 9

Genetic mutation is a trigger for the generation of malignant cells and an aberrant epigenetic status contributes to the maintenance of mutations and proliferation of mutated cells. Along with DNA methylation, histone modifications such as acetylation and methylation are significant to biological processes. Histone deacetylases (HDACs) are important epigenetic regulators of chromatin modifications and gene expression. Though several HDAC inhibitors are currently being tested in clinical trials, the roles of HDACs in malignant transformation remain unknown. Here, we showed that the expression of two forms of Hdac9, a full-length version (Hdac9FL) and a splicing variant lacking exon 7 (Hdac9Δ7), both class IIa HDACs, was up-regulated during chemically induced hepatocarcinogenesis. In addition, we found that HDAC9FL and HDAC9Δ7 are located in the nucleus and cytoplasm, respectively. We also found their nuclear localization and nuclear export signals to be encoded in exon 7 and exon 25, respectively. Though the two isoforms could not transform mouse NIH-3T3 fibroblasts, they promoted tumor cell anchorage-independent growth on soft agarose. The HDAC9 variants do not seem to cause cell transformation, but cytoplasmic and nuclear HDAC9 may contribute to the survival of malignant cells in the early stages of hepatocarcinogenesis.

Proteomic analysis of liver tissue fromHBx‐transgenic mice at early stages of hepatocarcinogenesis

The hepatitis B virus X-protein (HBx), a multifunctional viral regulator, participates in the viral life cycle and in the development of hepatocellular carcinoma (HCC). We previously reported a high incidence of HCC in transgenic mice expressing HBx. In this study, proteomic analysis was performed to identify proteins that may be involved in hepatocarcinogenesis and/or that could be utilized as early detection biomarkers for HCC. Proteins from the liver tissue of HBx-transgenic mice at early stages of carcinogenesis (dysplasia and hepatocellular adenoma) were separated by 2-DE, and quantitative changes were analyzed. A total of 22 spots displaying significant quantitative changes were identified using LC-MS/MS. In particular, several proteins involved in glucose and fatty acid metabolism, such as mitochondrial 3-ketoacyl-CoA thiolase, intestinal fatty acid-binding protein 2 and cytoplasmic malate dehydrogenase, were differentially expressed, implying that significant metabolic alterations occurred during the early stages of hepatocarcinogenesis. The results of this proteomic analysis provide insights into the mechanism of HBx-mediated hepatocarcinogenesis. Additionally, this study identifies possible therapeutic targets for HCC diagnosis and novel drug development for treatment of the disease.

111 TRANSIENT TELOMERE DYSFUNCTION PROMOTES HEPATOCARCINOGENESIS

Background: Chromosomal instability, short telomeres, and telomerase activation are hallmarks of human hepatocellular carcinoma. Studies in mouse models have shown that telomere dysfunction induces chromosomal instability and tumor initiation. However, telomere stabilization is required for tumor progression since too high levels of instability impair tumor cell survival. These results suggested that a sequence of telomere dysfunction followed by telomerase re-activation may enhance tumor initiation and progression during human carcinogenesis. Aims: The aim of this study was to test the hypothesis that telomere dysfunction followed by telomerase activation promote tumorigenesis. Methods: We produced transgenic mice allowing doxycycline inducible and transient expression of TRF2DBDM (inducing a transient peak of telomere dysfunction) in the liver. These mice were injected at postnatal day 15 with di-ethyl-nitrosamine. The same mice were treated with intrasplenic injection of doxycycline to induce transient expression of TRF2DBDM and telomere dysfunction. Control mice lacked the TRF2DBDM transgene but were treated the same way. The animals were analysed at an age of 13 months. Results: Doxycycline induced expression of TRF2DBDM in the liver of double-transgenic mice correlated with transient induction of telomere dysfunction in 2−4 month old mice as measured by induction of anaphase bridges (morphological correlate of chromosomal fusions). After 13 months both the LAPrtTA-TRF2DBDM (n = 23) and the control group (n = 29) developed HCC. However, transient telomere dysfunction in LAPrtTA-TRF2DBDM double transgenic mice strongly increased tumor formation. The tumor size was significantly increased by more than two fold in male LAPrtTA-TRF2DBDM mice compared to controls (p< 0.0001). In addition, the number of tumors was significantly increased in female LAPrtTA-TRF2DBDM mice compared to controls (p = 0.019). Chromosomal instability measured by array CGH revealed an increase of aberrations in double-transgenic mice. Conclusions: The results provide first experimental evidence that transient induction of telomere dysfunction during early stages of hepatocarcinogenesis leads to a significant acceleration of tumor formation. These results appear to be important for human hepatocarcinogenesis, which is characterized by telomere shortening and chromosomal instability.

P27Kip1 is overexpressed in very early stages of hepatocarcinogenesis

Hepatocellular carcinoma (HCC) associated with chronic liver disease evolves from precancerous lesions and early HCC to more malignant forms. Despite the demonstrated importance of cell-cycle regulators in tumor biology, there have been few studies of their role in multistep hepatocarcinogenesis. Expression of p27(Kip1) and a degradation pathway associated protein, S-phase kinase-interacting protein 2 (Skp2), was therefore evaluated in surgically resected specimens of eight adenomatous hyperplasias, 16 early HCC and 126 classical HCC. Immunohistochemistry revealed no p27(Kip1) expression in the majority of hepatocytes from normal and cirrhotic liver, whereas positive staining for p27(Kip1) protein was found in 75.0% and 93.8% of adenomatous hyperplasias and early HCC, respectively. The average p27(Kip1) labeling indices (LI) for adenomatous hyperplasias, early HCC, well differentiated HCC, moderately differentiated HCC and poorly differentiated HCC were 36.99, 43.59, 47.73, 49.24, and 30.21, respectively. Real-time quantitative reverse transcription-polymerase chain reaction (RT-PCR) analyses confirmed the increases. Skp2 LI were also significantly elevated in accordance with stepwise progression of hepatocarcinogenesis. Increased expression of Skp2 mRNA was observed most frequently in less differentiated tumors and Kaplan-Meier survival analysis showed a significantly association with a poor prognosis (P = 0.0496). In conclusion, a high level of p27(Kip1) expression is evident from early stages of hepatocarcinogenesis, indicating that this parameter could be a useful diagnostic marker for precancerous lesions and early HCC. In addition, Skp2 expression correlates with tumor dedifferentiation and may contribute to biological aggression in HCC.

How I became a biochemist

How I became a biochemist

Piperonyl butoxide activates c-Jun and ATF-2 in the hepatocytes of mice

In order to clarify the possible mechanism of hepatocarcinogenesis induced by piperonyl butoxide, we attempted to identify the transcription factor activated by piperonyl butoxide in the male ICR mouse liver. Administration of 0.6% piperonyl butoxide for 24 h elevated the level of liver nuclear proteins that bind to an AP-1 consensus oligonucleotide, and these proteins demonstrated a supershift with the anti-c-Jun antibody. Additionally, immunoblot analysis revealed that piperonyl butoxide induced c-Jun phosphorylation within 8 h of administration, and phosphorylated ATF-2 was detected after 24 h of piperonyl butoxide treatment. Immunohistochemical analysis also demonstrated the presence of phosphorylated ATF-2 in the hepatocyte nuclei of mice fed with 0.6% piperonyl butoxide for 24 h. Furthermore, piperonyl butoxide induced ATF-2 phosphorylation in TLR-3, a mouse immortalized hepatocyte cell line. These results indicated that piperonyl butoxide activated c-Jun and ATF-2 in mouse hepatocytes during the early stage of hepatocarcinogenesis.

Development of glutathione S‐transferase‐P‐negative foci accompanying nuclear factor‐erythroid 2‐related factor 2 expression during early stage of rat hepatocarcinogenesis

Glutathione S-transferase P (GST-P), a marker for rat hepatic preneoplastic lesions, is suggested to bind to Jun N-terminal kinase (JNK) to repress stress response, and GST-P gene expression is regulated by a transcription factor, nuclear factor-erythroid 2-related factor 2 (Nrf2). In this study, we examined by immunohistochemistry whether JNK2, p38 mitogen-activated protein kinase, and Nrf2 were expressed in GST-P-positive foci induced by the Solt-Farber protocol. At 2 weeks after partial hepatectomy, all GST-P-positive foci were negative for p38, and 86.4 +/- 5.6% and 64.7 +/- 6.3% of GST-P-positive foci were negative for JNK2 and Nrf2, respectively. Western blot analysis showed decreased p38 mitogen-activated protein kinase and JNK2 expression in livers treated with the protocol. In immunohistochemistry, besides GST-P-positive foci, GST-P-negative foci were detected as p38-negative foci in the surrounding tissues positive for p38. In contrast to GST-P-positive foci, most GST-P-negative foci showed enhanced Nrf2 expression. The number of GST-P-negative foci was 76 +/- 18/10 mm(2) of liver section at 2 weeks, but was undetectable at 1 week. The area of GST-P-negative foci was 0.09 +/- 0.05 mm(2), smaller than that of GST-P-positive ones (0.29 +/- 0.23). After treatment with carbon tetrachloride, small vacuoles due to liver injury were frequently observed inside GST-P-negative foci but less frequently in GST-P-positive foci. However, this treatment resulted in expression of JNK2, p38, and Nrf2 in both foci. These results showed development of GST-P-negative foci during the early stage of hepatocarcinogenesis and suggested that Nrf2 is not responsible for GST-P expression in rat hepatic preneoplastic foci.

Expression of the transcription factor Klf6 in cirrhosis, macronodules, and hepatocellular carcinoma

Macronodules (MN) occurring in cirrhosis are considered to be precursor lesions for hepatocellular carcinoma (HCC). However, early molecular events in hepatocellular carcinogenesis are poorly understood. The aim of this study was to compare gene expression profiling between cirrhotic tissues, MN, and HCC, to identify genes early involved in liver carcinogenesis. Tissues were obtained from explanted livers: nine cirrhosis, 10 MN, and seven HCC. Total RNAs were extracted by RNeasy and reverse transcribed with labelled [(33)P]-alpha ATP. Hybridations were performed on Atlas Human Cancer 1.2 membranes (1176 genes). A two-way hierarchical clustering algorithm successfully isolated specific gene expression profiles when comparing MN, cirrhosis, and HCC. A total of 16 and 14 genes were up- and down-expressed, respectively, in HCC as compared to cirrhotic tissues. The molecular signature of MN was characterized by the down-expression of 23 and 42 genes as compared to cirrhosis and HCC, respectively. Among them, Klf6 was down-expressed in all MN samples whereas it was over-expressed in cirrhosis and HCC. This result was confirmed at RNA level by quantitative real time-polymerase chain reaction and at protein level by Western blotting. However, no mutation in the exon 2 of Klf6 was detected. We identified a molecular signature of MN characterized by a down-expression of several genes. One of them, Klf6 was found to be down-expressed in all MN without evidence of somatic mutations in the exon 2. This gene could be involved at an early stage of hepatocarcinogenesis.

Molecular Mechanisms of Liver Carcinogenesis in the Mdr2-Knockout Mice

Mouse models of hepatocellular carcinoma (HCC) simulate specific subgroups of human HCC. We investigated hepatocarcinogenesis in Mdr2-knockout (Mdr2-KO) mice, a model of inflammation-associated HCC, using gene expression profiling and immunohistochemical analyses. Gene expression profiling showed that although Mdr2-KO mice differ from other published murine HCC models, they share several important deregulated pathways and many coordinately differentially expressed genes with human HCC data sets. Analysis of genome positions of differentially expressed genes in liver tumors revealed a prolonged region of down-regulated genes on murine chromosome 8 in three of the six analyzed tumor samples. This region is syntenic to human chromosomal regions that are frequently deleted in human HCC and harbor multiple tumor suppressor genes. Real-time reverse transcription-PCR analysis of 16 tumor samples confirmed down-regulation of several tumor suppressors in most tumors. We show that in the aged Mdr2-KO mice, cyclin D1 nuclear level is increased in dysplastic hepatocytes that do not form nodules; however, it is decreased in most dysplastic nodules and in liver tumors. We found that this decrease is mostly at the protein, rather than the mRNA, level. These findings raise the question on the role of cyclin D1 at early stages of hepatocarcinogenesis in the Mdr2-KO HCC model. Furthermore, we show that most liver tumors in Mdr2-KO mice were characterized by the absence of beta-catenin activation. In conclusion, the Mdr2-KO mouse may serve as a model for beta-catenin-negative subgroup of human HCCs characterized by low nuclear cyclin D1 levels in tumor cells and by down-regulation of multiple tumor suppressor genes.

Expression of microsomal prostaglandin E synthase‐1 in human hepatocelluar carcinoma

The objective of this study was to evaluate the expression of microsomal prostaglandin E synthase-1 (mPGES-1) in hepatocellular carcinoma (HCC) tissues. Forty surgically resected HCC tissues with adjacent non-tumorous liver tissues and 14 surgically resected, histologically normal liver tissues were used. The immunohistochemical expressions of the mPGES-1 protein in these HCC tissues and normal control livers were analysed. mPGES-1 mRNA expression was also analysed by the real-time polymerase chain reaction method using the same tissues. Microsomal prostaglandin E synthase-1 was not expressed in hepatocytes but instead in vascular endothelial cells and bile duct epithelial cells in normal liver tissues. The mPGES-1 expression in HCC tissues was significantly greater than its expression in the non-tumorous tissues. All types of HCC expressed more mPGES-1 than normal or hepatitis livers, and the levels of mPGES-1 expression in poorly differentiated HCC were similar to the levels in well-differentiated HCC. The mPGES-1 mRNA expression paralleled its protein expression in these tumorous and non-tumorous tissues. The present study is the first to demonstrate a high expression of mPGES-1 in well-differentiated HCC as well as in poorly differentiated HCC. These findings suggest that mPGES-1 may play a role in the advanced as well as early stage of hepatocarcinogenesis.