HNF1alpha inactivation promotes lipogenesis in human hepatocellular adenoma independently of SREBP-1 and carbohydrate-response element-binding protein (ChREBP) activation

Gene mutations in hepatocellular adenomas

Hepatocellular adenomas (HCA) are rare, benign liver tumours that often occur in women of reproductive age. HCA has been associated with the use of oral contraceptives, but the increased incidence of the tumour in older women and in men has linked the tumour type to other diseases, including the metabolic syndrome. Genotypical classification of the adenomas has led to the identification of four subgroups that correlate genotype with phenotype: human hepatocyte nuclear factor-1 alpha (HNF1α) inactivating HCA, β-catenin activating HCA, inflammatory HCA and unclassified HCA. HNF1α inactivating HCA is associated with bi-allelic mutations in the TCF1 gene and morphologically has marked steatosis. β-catenin activating HCA has increased activity of the Wnt/β-catenin pathway and is associated with possible malignant transformation. Inflammatory HCA is characterized by an oncogene-induced inflammation due to alterations in the Janus kinase/signal transducer and activator of transcription (JAK/STAT) pathway. In the diagnostic setting, sub classification of HCA is based primarily on immunohistochemical analyzes, and has had an increasing impact on choice of treatment and individual prognostic assessment. This review offers an overview of the reported gene mutations associated with hepatocellular adenomas together with a discussion of the diagnostic and prognostic value.

Update on the new classification of hepatic adenomas: clinical, molecular, and pathologic characteristics

CONTEXT

Hepatic adenoma is an uncommon, benign, hepatic neoplasm that typically occurs in women of child-bearing age, often with a history of long-term use of oral contraceptive drugs. This is usually detected as an incidental mass lesion in a noncirrhotic liver during imaging studies. Pathologic evaluation by needle core biopsy remains the gold standard for diagnosis. Molecular studies have revealed that hepatic adenomas involve unique molecular pathways that are distinct from hepatocellular carcinoma. Based on these studies, a French collaborative group has recently proposed a molecular-pathologic classification for hepatic adenomas. In addition, advances in molecular studies have led to reclassification of the "telangiectatic variant of focal nodular hyperplasia" as "hepatic adenoma, inflammatory subtype."

OBJECTIVE

To review the proposed, new classification of hepatic adenoma and the changes in diagnostic workup in light of the above-mentioned developments.

DATA SOURCES

Review of published literature and illustrations from clinical case material.

CONCLUSIONS

Definitive diagnosis of liver mass lesion on needle core biopsies has a decisive role in clinical management. With the advent of the new classification of hepatic adenomas and its prognostic implications, it is vital for pathologists to be aware of the morphologic features seen in different subtypes and the available diagnostic tools, such as immunohistochemistry, to help identify the correct subtype.

Resection, transplantation and local regional therapies for liver adenomas

Hepatocellular adenoma (HCA) is a rare benign liver-cell neoplasm, occurring predominantly in young obese women using oral contraceptives. HCA is a heterogeneous disease, which includes four subtypes (including unclassified) associated with various risks of haemorrhagic complications and malignant transformation. Magnetic resonance imaging is the modality of choice for both diagnosis and subtype characterization of HCA whereas percutaneous biopsy has only limited impact on the therapeutic strategy. In men HCA should be always resected while in women surgery should only be considered for lesions ≥5 cm and after cessation of hormonal therapy. Women with single or multiple HCAs <5 cm may be followed with regular MRI imaging since the vast majority of HCA remains stable or decreases in size. Pregnancy should not be discouraged provided close sonographic surveillance is undertaken.

Hepatocellular adenoma showing high uptake of (18)F-fluorodeoxyglucose (FDG) via an increased expression of glucose transporter 2 (GLUT-2)

Hepatocellular adenoma (HCA) is a benign liver neoplasm composed of hepatocytes. We experienced HCA demonstrating a high uptake of (18)F-fluorodeoxyglucose (FDG) on positron emission tomography-computed tomography, mimicking a malignant tumor. The mechanism underlying the uptake of FDG has not been identified. Here, we discuss that an enhancement of glucose metabolism via an increased expression of glucose transporter 2 may have a role in the high uptake of FDG shown by HCAs.

Overexpression of phosphatidylinositol 4-kinase type IIIα is associated with undifferentiated status and poor prognosis of human hepatocellular carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) is a particularly severe disease characterized by a high rate of recurrence and death even after surgical resection. Molecular characterization of HCC helps refine prognosis and may facilitate the development of improved therapy. Phosphatidylinositol 4-kinases have recently been identified as cellular factors associated with cancer. Also, phosphatidylinositol 4-kinase type IIIα (PI4KA) is necessary for the propagation of the hepatitis C virus, a major etiological factor for HCC.

METHODS

Reverse transcription, quantitative real-time PCR was used to assay PI4KA mRNA. The expression levels were investigated both in a collection of molecularly and clinically characterized hepatic tissues from 344 patients with diverse liver diseases and in human hepatocyte cell lines whose proliferative and differentiation status was controlled by specific culture conditions. Analytical microarray data for 60 HCC and six normal liver tissue samples were exploited to study correlations between PI4KA mRNA levels and cell proliferation markers in vivo. Postoperative disease-specific survival and time to recurrence in a set of 214 patients with HCC were studied by univariate and multivariate analyses.

RESULTS

PI4KA mRNA was more abundant in HCC than normal healthy tissues. This upregulation correlated significantly with both poor differentiation and the active proliferation rate in HCC. These associations were confirmed with in vitro models. Moreover, patients with HCC who had been treated by surgical resection and had higher PI4KA mRNA concentrations in their tumor tissue exhibited a higher risk of tumor recurrence (median time: 20 months versus 49 months, P = 0.0012) and shorter disease-specific survival (first quartile time: 16 months versus 48 months, P = 0.0004). Finally, the abundance of PI4KA mRNA proved to be an independent prognostic marker of survival for cases of HCC (hazard ratio = 2.36, P = 0.0064).

CONCLUSIONS

PI4KA mRNA could be used as a new molecular marker to improve established prognostic models for HCC. These findings also indicate possible new lines of research for the development of innovative therapeutic approaches targeting PI4KA.

Hepatitis C virus modulates lipid regulatory factor Angiopoietin-like 3 gene expression by repressing HNF-1α activity

BACKGROUND & AIMS

HCV relies on host lipid metabolism to complete its life cycle and HCV core is crucial to this interaction. Liver secreted ANGPTL-3 is an LXR- and HNF-1α-regulated protein, which plays a key role in lipid metabolism by increasing plasma lipids via inhibition of lipase enzymes. Here we aimed to investigate the modulation of ANGPTL-3 by HCV core and identify the molecular mechanisms involved.

METHODS

qRT-PCR and ELISA were used to assess ANGPTL-3 mRNA and protein levels in HCV patients, the JFH-1 infectious system and liver cell lines. Transfections, chromatin immunoprecipitation and immunofluorescence delineated parts of the molecular mechanisms implicated in the core-mediated regulation of ANGPTL-3 gene expression.

RESULTS

ANGPTL-3 gene expression was decreased in HCV-infected patients and the JFH-1 infectious system. mRNA and promoter activity levels were down-regulated by core. The response was lost when an HNF-1α element in ANGPTL-3 promoter was mutated, while loss of HNF-1α DNA binding to this site was recorded in the presence of HCV core. HNF-1α mRNA and protein levels were not altered by core. However, trafficking between nucleus and cytoplasm was observed and then blocked by an inhibitor of the HNF-1α-specific kinase Mirk/Dyrk1B. Transactivation of LXR/RXR signalling could not restore core-mediated down-regulation of ANGPTL-3 promoter activity.

CONCLUSIONS

ANGPTL-3 is negatively regulated by HCV in vivo and in vitro. HCV core represses ANGPTL-3 expression through loss of HNF-1α binding activity and blockage of LXR/RXR transactivation. The putative ensuing increase in serum lipid clearance and uptake by the liver may sustain HCV virus replication and persistence.

Clinicopathological analysis of hepatocellular adenoma according to new bordeaux classification: report of eight korean cases

Background

Hepatocellular adenoma (HCA) is a rare benign tumor of the liver. A subtype classification of HCA (hepatocyte nuclear factor 1α [HNF1α]-mutated, β-catenin-mutated HCA, inflammatory HCA, and unclassified HCA) has recently been established based on a single institutional review of a HCA series by the Bordeaux group.

Methods

We used histologic and immunohistochemical parameters to classify and evaluate eight cases from our institution. We evaluated the new classification method and analyzed correlations between our results and those of other reports.

Results

Seven of our eight cases showed histologic and immunohistochemical results consistent with previous reports. However, one case showed overlapping histologic features, as previously described by the Bordeaux group. Four cases showed glutamine synthetase immunohistochemical staining inconsistent with their classification, indicating that glutamine synthetase staining may not be diagnostic for β-catenin-mutated HCA. HNF1α-mutated HCA may be indicated by the absence of liver fatty acid binding protein expression. Detection of amyloid A may indicate inflammatory HCA. HCA with no mutation in the HNF1α or β-catenin genes and no inflammatory protein expression is categorized as unclassified HCA.

Conclusions

Although the new classification is now generally accepted, validation through follow-up studies is necessary.

Hepatocellular benign tumors-from molecular classification to personalized clinical care

Focal nodular hyperplasia (FNH) and hepatocellular adenoma (HCA) are benign hepatocellular tumors that develop most frequently in women without cirrhosis. Genomic approaches have identified signaling pathways related to these benign hepatocyte proliferations. FNH, a polyclonal lesion, is characterized by local vascular abnormalities and heterogeneous activation of Wnt/β-catenin and transforming growth factor β signaling. Four major subgroups of HCAs have been identified based on mutations in specific oncogenes and tumor suppressor genes. Each molecular subtype of HCA has been associated with specific pathways, providing new information about benign tumorigenesis. Key features include metabolic alterations (induced by defects in HNF1A), oncogene-induced inflammation (activation of JAK-STAT signaling in inflammatory adenomas), and an association between activation of Wnt/β-catenin signaling and progression of HCAs in hepatocellular carcinomas. Benign hepatocellular tumors can be classified using immunohistochemical analyses. Studies of genotypes and phenotypes of FNH and HCAs have led to the identification of risk factors and improved invasive and noninvasive diagnostic techniques, evaluation of prognosis, and treatment. We review the molecular pathways involved in benign hepatocyte proliferation and discuss how this basic knowledge has been progressively translated into personalized clinical care.

SSAT/AHPBA joint symposium on evaluation and treatment of benign liver lesions

BACKGROUND

Benign liver lesions are common incidental radiologic findings.

METHODS

Experts convened in 2011 at a Society for Surgery of the Alimentary Tract/ Americas Hepato-Pancreato-Biliary Association joint symposium to discuss the evaluation and treatment of benign liver lesions.

RESULTS

Most benign liver lesions can be accurately diagnosed with high-quality imaging, including ultrasonography, multiphase computed tomography, and magnetic resonance imaging, particularly with hepatocyte-specific contrast agents. Percutaneous biopsy is reserved for lesions that cannot be characterized radiographically, and its accuracy is improved with immunophenotypic markers. Hepatic cysts are the most commonly diagnosed benign liver lesions; these must be distinguished from malignant cystic lesions, which are rare. Among the solid benign liver lesions, hemangiomas and focal nodular hyperplasia seldom require treatment. In contrast, hepatocellular adenomas are associated with a risk for complications. A new classification system for hepatocellular adenomas based on genetic and phenotypic features can help guide patient care. In patients who are symptomatic or at risk for complications, multidisciplinary evaluation and treatment based on clinicopathologic, radiographic, and molecular analysis is needed.

CONCLUSIONS

Most benign liver lesions can be accurately diagnosed radiographically and do not require treatment. Treatment is necessary for patients with symptoms or at risk for complications.

Molecular characterization of hepatocellular adenomas developed in patients with glycogen storage disease type I

BACKGROUND & AIMS

Hepatocellular adenomas (HCA) are benign liver tumors mainly related to oral contraception and classified into 4 molecular subgroups: inflammatory (IHCA), HNF1A-inactivated (H-HCA), β-catenin-activated (bHCA) or unclassified (UHCA). Glycogen storage disease type I (GSD) is a rare hereditary metabolic disease that predisposes to HCA development. The aim of our study was to characterize the molecular profile of GSD-associated HCA.

METHODS

We characterized a series of 25 HCAs developed in 15 patients with GSD by gene expression and DNA sequence of HNF1A, CTNNB1, IL6ST, GNAS, and STAT3 genes. Moreover, we searched for glycolysis, gluconeogenesis, and fatty acid synthesis alterations in GSD non-tumor livers and compared our results to those observed in a series of sporadic H-HCA and various non-GSD liver samples.

RESULTS

GSD adenomas were classified as IHCA (52%) mutated for IL6ST or GNAS, bHCA (28%) or UHCA (20%). In contrast, no HNF1A inactivation was observed, showing a different molecular subtype distribution in GSD-associated HCA from that observed in sporadic HCA (p = 0.0008). In non-tumor GSD liver samples, we identified glycolysis and fatty acid synthesis activation with gluconeogenesis repression. Interestingly, this gene expression profile was similar to that observed in sporadic H-HCA.

CONCLUSIONS

Our study showed a particular molecular profile in GSD-related HCA characterized by a lack of HNF1A inactivation. This exclusion could be explained by similar metabolic defects observed with HNF1A inactivation and glucose-6-phosphatase deficiency. Inversely, the high frequency of β-catenin mutations could be related to the increased frequency of malignant transformation in hepatocellular carcinoma.

Molecular classification of hepatocellular adenomas

Hepatocellular adenomas (HCAs) are benign tumors developed in normal liver most frequently in women before menopause. HCAs lead to diagnostic pitfalls and several difficulties to assess the risk of malignant transformation in these young patients. Recent advances in basic knowledge have revealed a molecular classification related to risk factors, pathological features, and risk of transformation in hepatocellular carcinoma. Three major molecular pathways have been identified altered in specific HCA subgroups that are defined by either (1) inactivation of hepatocyte nuclear factor 1A (HNF1A) transcription factor, (2) activation of the WNT/β-catenin by CTNNB1 mutations, or (3) activation of the IL6/STAT3 pathway by somatic mutation of IL6ST, GNAS, or STAT3. Here, we will review the different molecular classes of HCA.

Molecular pathogenesis of hepatic adenomas and its implications for surgical management

INTRODUCTION

Hepatic adenomas (HAs) are benign tumors of the liver, which can be solitary or multiple, and have a definite risk of malignant degeneration.

DISCUSSION

The pathogenesis and natural history of this disease entity were previously unknown. Recent research into the molecular pathogenesis of this condition has provided evidence for the malignant transformation of some of these adenomas. In the current article, we discuss the current evidence on the molecular biology underlying malignant transformation of hepatic adenomas and the implications for the surgical management of this disease.

A transgenic zebrafish liver tumor model with inducible Myc expression reveals conserved Myc signatures with mammalian liver tumors

Myc is a pleiotropic transcription factor that is involved in many cellular activities relevant to carcinogenesis, including hepatocarcinogenesis. The zebrafish has been increasingly used to model human diseases and it is particularly valuable in helping to identify common and conserved molecular mechanisms in vertebrates. Here we generated a liver tumor model in transgenic zebrafish by liver-specific expression of mouse Myc using a Tet-On system. Dosage-dependent induction of Myc expression specifically in the liver was observed in our Myc transgenic zebrafish, TO(Myc), and the elevated Myc expression caused liver hyperplasia, which progressed to hepatocellular adenoma and carcinoma with prolonged induction. Next generation sequencing-based transcriptomic analyses indicated that ribosome proteins were overwhelmingly upregulated in the Myc-induced liver tumors. Cross-species analyses showed that the zebrafish Myc model correlated well with Myc transgenic mouse models for liver cancers. The Myc-induced zebrafish liver tumors also possessed molecular signatures highly similar to human those of hepatocellular carcinoma. Finally, we found that a small Myc target gene set of 16 genes could be used to identify liver tumors due to Myc upregulation. Thus, our zebrafish model demonstrated the conserved role of Myc in promoting hepatocarcinogenesis in all vertebrate species.

Integrated analysis of somatic mutations and focal copy-number changes identifies key genes and pathways in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the most common primary liver malignancy. Here, we performed high-resolution copy-number analysis on 125 HCC tumors and whole-exome sequencing on 24 of these tumors. We identified 135 homozygous deletions and 994 somatic mutations of genes with predicted functional consequences. We found new recurrent alterations in four genes (ARID1A, RPS6KA3, NFE2L2 and IRF2) not previously described in HCC. Functional analyses showed tumor suppressor properties for IRF2, whose inactivation, exclusively found in hepatitis B virus (HBV)-related tumors, led to impaired TP53 function. In contrast, inactivation of chromatin remodelers was frequent and predominant in alcohol-related tumors. Moreover, association of mutations in specific genes (RPS6KA3-AXIN1 and NFE2L2-CTNNB1) suggested that Wnt/β-catenin signaling might cooperate in liver carcinogenesis with both oxidative stress metabolism and Ras/mitogen-activated protein kinase (MAPK) pathways. This study provides insight into the somatic mutational landscape in HCC and identifies interactions between mutations in oncogene and tumor suppressor gene mutations related to specific risk factors.

Role of low-density lipoprotein receptor in the hepatitis C virus life cycle

Hepatitis C virus (HCV) particles are known to be in complex with lipoproteins. As a result of this interaction, the low-density lipoprotein (LDL) receptor (LDLR) has been proposed as a potential entry factor for HCV; however, its implication in virus entry remains unclear. Here, we reinvestigated the role of the LDLR in the HCV life cycle by comparing virus entry to the mechanism of lipoprotein uptake. A small interfering RNA targeting the LDLR in Huh-7 cells reduced HCV infectivity, confirming that this receptor plays a role in the life cycle of HCV generated in cell culture. However, kinetics of internalization were much faster for lipoproteins than for infectious HCV particles. Furthermore, a decrease in HCV RNA replication was observed by blocking the LDLR with a specific antibody, and this was associated with an increase in the ratio of phosphatidylethanolamine to phosphatidylcholine in host cells. Nevertheless, a soluble form of the LDLR inhibited both HCV entry into the hepatocytes and its binding to the LDLR expressed on Chinese hamster ovary cells, suggesting a direct interaction between the HCV particle and the LDLR. Finally, we showed that modification of HCV particles by lipoprotein lipase (LPL) reduces HCV infectivity and increases HCV binding to LDLR. Importantly, LPL treatment also induced an increase in RNA internalization, suggesting that LDLR, at least in some conditions, leads to nonproductive internalization of HCV.

CONCLUSION

The LDLR is not essential for infectious HCV particle entry, whereas the physiological function of this receptor is important for optimal replication of the HCV genome.

Genetics and imaging of hepatocellular adenomas: 2011 update

Hepatocellular adenomas are benign liver neoplasms with specific but varied histopathologic findings and tumor biology. The results from recent studies of the pathologic and genetic basis of hepatocellular adenomas provide important insights into the pathogenesis and molecular changes, as well as the putative oncologic pathways used by diverse adenoma subtypes. On the basis of the genetic and pathologic features, hepatocellular adenomas are categorized into three distinct subtypes: (a) inflammatory hepatocellular adenomas, (b) hepatocyte nuclear factor 1 α-mutated hepatocellular adenomas, and (c) β-catenin-mutated hepatocellular adenomas. Different subtypes show variable clinical behavior, imaging findings, and natural history, and thus the options for treatment and surveillance may vary. Cross-sectional imaging plays an important role in the diagnosis, subtype characterization, identification of complications, and surveillance of hepatocellular adenomas. New schemas for genotype-phenotype classification of hepatic adenomas, as well as management triage of patients with specific subtypes of adenomas, are being proposed in an attempt to improve clinical outcomes.

GNAS-activating mutations define a rare subgroup of inflammatory liver tumors characterized by STAT3 activation

BACKGROUND & AIMS

Mosaic G-protein alpha-subunit (GNAS)-activating mutations are responsible for the McCune-Albright (MCA) syndrome. This oncogene that activates the adenylate cyclase is also mutated in various tumor types leading to the accumulation of cyclic-AMP. Identification of a hepatocellular adenoma (HCA) in two MCA patients led us to search for GNAS activation in benign and malignant hepatocellular carcinogenesis.

METHODS

GNAS mutations were screened by sequencing 164 HCA, 245 hepatocellular carcinoma (HCC), and 17 fibrolamellar carcinomas. Tumors were characterized by quantitative RT-PCR, gene mutation screening and pathological reviewing. The consequences of wild type and mutant GNAS expression were analyzed in hepatocellular cell lines.

RESULTS

A somatic GNAS-activating mutation was identified in 5 benign tumors and in 2 HCC. In benign tumors, GNAS mutations were exclusive from HNF1A, CTNNB1, and IL6ST mutations whereas one HCC demonstrated both CTNNB1 and GNAS mutations. Quantitative RT-PCR showed an activation of the IL-6 and interferon pathways in GNAS-mutated tumor tissues. Accordingly, pathological reviewing identified in GNAS-mutated tumors an inflammatory phenotype characterized by fibrosis and STAT3 activation. We further demonstrated in HCC cell lines that GNAS mutant expression induced inflammatory response and STAT3 activation.

CONCLUSIONS

We identified for the first time the association between two rare diseases, MCA syndrome and HCA occurrence, but also that somatic GNAS-activating mutations in sporadic benign and malignant liver tumors are characterized by an inflammatory phenotype. These results showed a cross-talk between cyclic-AMP and JAK/STAT pathways in liver tumors and they reinforce the role of STAT3 activation in liver tumorigenesis.

Indications and Long-Term Outcome after Elective Surgery for Hepatocellular Adenoma

The management of hepatocellular adenoma (HA) is dependent on several parameters, which are influencing the decision for further management. The aim of this study was to evaluate the clinical presentation, indications, and long-term outcome of surgical treatment in a single-institution analysis. Forty-nine patients underwent elective hepatectomy for HA between 1990 and 2007. Analysis parameters included demographic data, lesion number and size, diagnostic method, mode of surgery, and postoperative outcome. Mean follow-up was 108 months. Thirty-six patients underwent hormone therapy and four patients had a history of cancer before surgical treatment. The mean tumor diameter was 9.8 cm. Mild or moderate postoperative complications were recorded in 16 patients. There was no perioperative mortality. Symptoms were relieved in 95 per cent of the patients. Intratumoral hemorrhage was detected in 21 specimens (43%); malignant transformation was detected in zero specimens. Among patients with HA with clinical symptoms, tumor diameter greater than 5 cm and in male patients the indication for surgery should be given because of the high risk of tumor-related complications. Elective liver resection for HA is a safe procedure and results in a good long-term outcome.

MicroRNA-194 is a target of transcription factor 1 (Tcf1, HNF1α) in adult liver and controls expression of frizzled-6

Transcription factor 1 (Tcf1; hepatocyte nuclear factor 1α [HNF1α]) is critical for hepatocyte development and function. Whether Tcf1 also regulates hepatic microRNAs (miRNAs) has not been investigated yet. Here we analyzed Tcf1-dependent miRNA expression in adult mice in which this transcription factor had been genetically deleted (Tcf1(-/-) ) using miRNA microarray analysis. The miR-192/-194 cluster was markedly down-regulated in liver of Tcf1(-/-) mice. MiR-192/-194 levels were also decreased in two other tissues that express Tcf1, kidney and small intestine, although to a lesser extent than in liver. In order to identify targets of miR-192/-194 in vivo we combined Affymetrix gene analysis of liver in which miR-192/-194 had been silenced or overexpressed, respectively, and tested regulated messenger RNAs (mRNAs) with multiple binding sites for these miRNAs. This approach revealed frizzled-6 (Fzd6) as a robust endogenous target of miR-194. MiR-194 also targets human FZD6 and expression of miR-194 and Fzd6 are inversely correlated in a mouse model of hepatocellular carcinoma (Dgcr8(flox/flox) p53(flox/flox) × Alb-Cre).

CONCLUSION

Our results support a role of miR-194 in liver tumorigenesis through its endogenous target Fzd6. These results may have important implications for Tcf1-mediated liver proliferation.

HNF1α inhibition triggers epithelial-mesenchymal transition in human liver cancer cell lines

Background

Hepatocyte Nuclear Factor 1α (HNF1α) is an atypical homeodomain-containing transcription factor that transactivates liver-specific genes including albumin, α-1-antitrypsin and α- and β-fibrinogen. Biallelic inactivating mutations of HNF1A have been frequently identified in hepatocellular adenomas (HCA), rare benign liver tumors usually developed in women under oral contraceptives, and in rare cases of hepatocellular carcinomas developed in non-cirrhotic liver. HNF1α-mutated HCA (H-HCA) are characterized by a marked steatosis and show activation of glycolysis, lipogenesis, translational machinery and mTOR pathway. We studied the consequences of HNF1α silencing in hepatic cell lines, HepG2 and Hep3B and we reproduced most of the deregulations identified in H-HCA.

Methods

We transfected hepatoma cell lines HepG2 and Hep3B with siRNA targeting HNF1α and obtained a strong inhibition of HNF1α expression. We then looked at the phenotypic changes by microscopy and studied changes in gene expression using qRT-PCR and Western Blot.

Results

Hepatocytes transfected with HNF1α siRNA underwent severe phenotypic changes with loss of cell-cell contacts and development of migration structures. In HNF1α-inhibited cells, hepatocyte and epithelial markers were diminished and mesenchymal markers were over-expressed. This epithelial-mesenchymal transition (EMT) was related to the up regulation of several EMT transcription factors, in particular SNAIL and SLUG. We also found an overexpression of TGFβ1, an EMT initiator, in both cells transfected with HNF1α siRNA and H-HCA. Moreover, TGFβ1 expression is strongly correlated to HNF1α expression in cell models, suggesting regulation of TGFβ1 expression by HNF1α.

Conclusion

Our results suggest that HNF1α is not only important for hepatocyte differentiation, but has also a role in the maintenance of epithelial phenotype in hepatocytes.

Recent advances in cytogenetics and molecular biology of adult hepatocellular tumors: implications for imaging and management

Focal nodular hyperplasia (FNH), hepatocellular adenoma (HCA), and hepatocellular carcinoma (HCC) compose hepatocellular neoplasms that occur in adults. These tumors demonstrate characteristic epidemiologic and histopathologic features and clinical and imaging manifestations. HCAs are monoclonal neoplasms characterized by increased predilection to hemorrhage or rupture and occasional transformation to HCC. On the other hand, FNH is a polyclonal tumorlike lesion that occurs in response to increased perfusion and has an indolent clinical course. Up to 90% of HCCs occur in the setting of cirrhosis. Chronic viral hepatitis (hepatitis B and hepatitis C) infection and metabolic syndrome are major risk factors that can induce HCCs in nonfibrotic liver. Recent advances in pathology and genetics have led to better understanding of the histogenesis, natural history, and molecular events that determine specific oncologic pathways used by these neoplasms. HCAs are now believed to result from specific genetic mutations involving TCF1 (transcription factor 1 gene), IL6ST (interleukin 6 signal transducer gene), and CTNNB1 (β catenin-1 gene); FNHs are characterized by an "imbalance" of angiopoietin. While the β catenin signaling pathway is associated with well- and moderately differentiated HCCs, mutations involving p53 (tumor protein 53 gene), MMP14 (matrix metalloproteinase 14 gene), and RhoC (Ras homolog gene family, member C) are associated with larger tumor size, higher tumor grade with resultant shortened tumor-free survival, and poor prognosis. Fibrolamellar carcinoma (FLC), a unique HCC subtype, exhibits genomic homogeneity that partly explains its better overall prognosis. On the basis of recent study results involving cytogenetics and oncologic pathways of HCCs, novel drugs that act against molecular targets are being developed. Indeed, sorafenib (a multikinase inhibitor) is currently being used in the successful treatment of patients with advanced HCC. Characterization of genetic abnormalities and genotype-phenotype correlations in adult hepatocellular tumors provides better understanding of tumor pathology and biology, imaging findings, prognosis, and response to molecular therapeutics.

Hepatocellular adenomas: current update on genetics, taxonomy, and management

Hepatocellular adenomas (HCAs) are uncommon, benign hepatocellular neoplasms that commonly occur in young women. Recent advances in pathology and cytogenetics have thrown fresh light on the pathogenesis of HCAs leading to classification of HCAs into 3 distinct subtypes, each with a characteristic epidemiology, histopathology, oncogenesis, and imaging findings. The aim of the article was to provide a comprehensive review of contemporary taxonomy of HCAs, with an emphasis on cross-sectional imaging findings and management.

Is Crohn's creeping fat an adipose tissue?

BACKGROUND

In human pathology, the "creeping fat" (CF) of the mesentery is unique to Crohn's disease (CD). CF is usually referred to as an ectopic extension of mesenteric adipose tissue (MAT). However, since no animal model developing CF has ever been established, very little is known about this type of fat-depot expansion and its role in the development of the disease.

METHODS

We developed and standardized an experimental protocol in mice that reproducibly induces CF development when a severe colonic inflammation is obtained by intracolonic instillation of DNBS.

RESULTS

Macro-microscopic observations revealed a fatty appearance of CF. Yet when compared to MAT from the same animals, CF contains very little triglycerides, few adipocytes, and we observed a very low expression and protein levels of both adipose markers (hormone-sensitive lipase, perilipin) and adipocytokines (leptin, adiponectin). The decreased expression of perilipin in CF was also observed by immunohistochemistry. Conversely, the expression of proinflammatory and fibrous markers (Pref-1) was much higher in CF than in MAT. These observations were fully consistent with those made on CF recovered from five CD patients and compared with subcutaneous and mesenteric fat from the same patients.

CONCLUSIONS

Altogether, this work reports an original experimental mice model of CF. In this model we establish for the first time that CF only occurs in severe colonic inflammation and shows an inflammatory, fibrous but not an adipose pattern.

Focal nodular hyperplasia with major sinusoidal dilatation: a misleading entity

Focal nodular hyperplasia (FNH) is a benign liver lesion thought to be a non-specific response to locally increased blood flow. Although the diagnosis of FNH and hepatocellular adenoma (HCA) has made great progress over the last few years using modern imaging techniques, there are still in daily practice some difficulties concerning some atypical nodules. Here, the authors report the case of a 47-year-old woman with a single liver lesion thought to be, by imaging, an inflammatory HCA with major sinusoidal congestion. This nodule was revealed to be, at the microscopical level and after specific immunostaining and molecular analysis, an FNH with sinusoidal dilatation (so-called telangiectatic focal nodular hyperplasia).

ELOVL2 controls the level of n-6 28:5 and 30:5 fatty acids in testis, a prerequisite for male fertility and sperm maturation in mice

ELOVL2 is a member of the mammalian microsomal ELOVL fatty acid enzyme family, involved in the elongation of very long-chain fatty acids including PUFAs required for various cellular functions in mammals. Here, we used ELOVL2-ablated (Elovl2(-/-)) mice to show that the PUFAs with 24-30 carbon atoms of the ω-6 family in testis are indispensable for normal sperm formation and fertility in male mice. The lack of Elovl2 was associated with a complete arrest of spermatogenesis, with seminiferous tubules displaying only spermatogonia and primary spermatocytes without further germinal cells. Furthermore, based on acyl-CoA profiling, heterozygous Elovl2(+/-) male mice exhibited haploinsufficiency, with reduced levels of C28:5 and C30:5n-6 PUFAs, which gave rise to impaired formation and function of haploid spermatides. These new insights reveal a novel mechanism involving ELOVL2-derived PUFAs in mammals and previously unrecognized roles for C28 and C30 n-6 PUFAs in male fertility. In accordance with the function suggested for ELOVL2, the Elovl2(-/-) mice show distorted levels of serum C20 and C22 PUFAs from both the n-3 and the n-6 series. However, dietary supplementation with C22:6n-3 could not restore male fertility to Elovl2(+/-) mice, suggesting that the changes in n-6 fatty acid composition seen in the testis of the Elovl2(+/-) mice, cannot be compensated by increased C22:6n-3 content.

Ablation of the very-long-chain fatty acid elongase ELOVL3 in mice leads to constrained lipid storage and resistance to diet-induced obesity

Although saturated and monounsaturated very-long-chain fatty acids (VLCFAs) have long been associated with undesirable effects on health, including obesity, heart failure, and atherosclerosis, the physiological role of endogenous synthesis is largely unknown. The fatty acid elongase ELOVL3 is involved in the synthesis of C20-C24 saturated and monounsaturated VLCFAs mainly in liver, brown and white adipose tissue, and triglyceride-rich glands such as the sebaceous and meibomian glands. Here we show that ablation of ELOVL3 leads to reduced adiponectin levels, constrained expansion of adipose tissue, and resistance against diet-induced obesity, a situation that is more exaggerated in female mice. Both female and male knockout mice show reduced hepatic lipogenic gene expression and triglyceride content, a situation that is associated with reduced de novo fatty acid synthesis and uptake. As a consequence, the VLDL-triglyceride level in serum is significantly reduced. Remarkably, despite increased energy expenditure, markedly reduced serum levels of leptin, and increased expression of orexigenic peptides in the hypothalamus, the Elovl3(-/-) mice do not compensate by increased food intake. Thus, these results reveal that C20-C22 saturated and monounsaturated VLCFAs produced by ELOVL3 are indispensable for appropriate synthesis of liver triglycerides, fatty acid uptake, and storage in adipose tissue.

Molecular classification of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the most frequent tumour derived from the malignant transformation of hepatocytes. It is well established that cancer is a disease of the genome and, as in other types of solid tumours, a large number of genetic and epigenetic alterations are accumulated during the hepatocarcinogenesis process. Recent developments using comprehensive genomic tools have enabled the identification of the molecular diversity in human HCC. Consequently, several molecular classifications have been described using different approaches and important progress has been made particularly with the transcriptomic, genetic, chromosomal, miRNA and methylation profiling. On the whole, all these molecular classifications are related and one of the major determinants of the identified subgroups of tumours are gene mutations found in oncogenes and tumour suppressors. However, the full understanding of the HCC molecular classification requires additional comprehensive studies using both genomic and pathway analyses. Finally, a refinement of the molecular classification of HCC, taking into account the geographical and genetic diversity of the patients, will be essential for an efficient design of the forthcoming personalized clinical treatments.

Spectrum of HNF1A somatic mutations in hepatocellular adenoma differs from that in patients with MODY3 and suggests genotoxic damage

OBJECTIVE

Maturity onset diabetes of the young type 3 (MODY3) is a consequence of heterozygous germline mutation in HNF1A. A subtype of hepatocellular adenoma (HCA) is also caused by biallelic somatic HNF1A mutations (H-HCA), and rare HCA may be related to MODY3. To better understand a relationship between the development of MODY3 and HCA, we compared both germline and somatic spectra of HNF1A mutations.

RESEARCH DESIGN AND METHODS

We compared 151 somatic HNF1A mutations in HCA with 364 germline mutations described in MODY3. We searched for genotoxic and oxidative stress features in HCA and surrounding liver tissue.

RESULTS

A spectrum of HNF1A somatic mutations significantly differed from the germline changes in MODY3. In HCA, we identified a specific hot spot at codon 206, nonsense and frameshift mutations mainly in the NH(2)-terminal part, and almost all amino acid substitutions were restricted to the POU-H domain. The high frequency of G-to-T tranversions, predominantly found on the nontranscribed DNA strand, suggested a genotoxic mechanism. However, no features of oxidative stress were observed in the nontumor liver tissue. Finally, in a few MODY3 patients with HNF1A germline mutation leading to amino acid substitutions outside the POU-H domain, we identified a different subtype of HCA either with a gp130 and/or CTNNB1 activating mutation.

CONCLUSIONS

Germline HNF1A mutations could be associated with different molecular subtypes of HCA. H-HCA showed mutations profoundly inactivating hepatocyte nuclear factor-1alpha function; they are associated with a genotoxic signature suggesting a specific toxicant exposure that could be associated with genetic predisposition.

Loss of hepatocyte nuclear factor 1alpha function in human hepatocellular adenomas leads to aberrant activation of signaling pathways involved in tumorigenesis

Hepatocellular adenomas (HCAs) are benign liver tumors that usually develop in women who are taking oral contraceptives. Among these tumors, biallelic inactivating mutations of the hepatocyte nuclear factor 1alpha (HNF1A) transcription factor have been frequently identified and in rare cases of hepatocellular carcinomas developed in noncirrhotic liver. Because HNF1A meets the genetic criteria of a tumor suppressor gene, we aimed to elucidate the tumorigenic mechanisms related to HNF1alpha inactivation in hepatocytes. We searched for signaling pathways aberrantly activated in human HNF1A-mutated HCA (H-HCA) using a genome-wide transcriptome analysis comparing five H-HCA with four normal livers. We validated the main pathways by quantitative reverse transcription polymerase chain reaction (RT-PCR) and western blotting in a large series of samples. Then, we assessed the role of HNF1alpha in the observed deregulations in hepatocellular cell models (HepG2 and Hep3B) by silencing its endogenous expression using small interfering RNA. Along with the previously described induction of glycolysis and lipogenesis, H-HCA also displayed overexpression of several genes encoding growth factor receptors, components of the translation machinery, cell cycle, and angiogenesis regulators, with, in particular, activation of the mammalian target of rapamycin (mTOR) pathway. Moreover, estradiol detoxification activities were shut down, suggesting a hypersensitivity of H-HCA to estrogenic stimulation. In the cell model, inhibition of HNF1alpha recapitulated most of these identified transcriptional deregulations, demonstrating that they were related to HNF1alpha inhibition.

CONCLUSION

H-HCA showed a combination of alterations related to HNF1alpha inactivation that may cooperate to promote tumor development. Interestingly, mTOR appears as a potential new attractive therapeutic target for treatment of this group of HCAs.

Role of Wnt/β-catenin signaling in liver metabolism and cancer

Wnt/β-catenin signaling is known for its role in embryogenesis as well as carcinogenesis. In the liver, it plays many critical roles during hepatic development and regeneration, and its dysregulation is evident in aberrant hepatic growth during various liver tumors. Its chief cellular roles in the liver include regulation of processes of cell proliferation, apoptosis, oxidative stress and differentiation, which in turn contributes to hepatic growth, zonation, xenobiotic metabolism and other metabolic processes inherent to the liver. Most of these functions of the Wnt/β-catenin signaling are dictated through the highly temporal and tissue-specific or non-specific transcriptional targets of the pathway. In addition, some of the critical functions such as cell-cell adhesion and perhaps maintenance of various junctions that are critical from an epithelial cell biology perspective are also a function of β-catenin, which is the central component of the canonical Wnt pathway. Various animal models and clinical studies have demonstrated the spectra of Wnt/β-catenin signaling in liver health and disease. Thus therapeutic modulation of this pathway for improved hepatic health is inevitable in the future. The current review discusses the advances in our understanding of the Wnt/β-catenin signaling in liver physiology and pathology especially in hepatic metabolism and various tumors in adult liver and goes on to extrapolate the pre-clinical significance and possible translational implications of such findings.

Role of Wnt/β-catenin signaling in liver metabolism and cancer

Wnt/β-catenin signaling is known for its role in embryogenesis as well as carcinogenesis. In the liver, it plays many critical roles during hepatic development and regeneration, and its dysregulation is evident in aberrant hepatic growth during various liver tumors. Its chief cellular roles in the liver include regulation of processes of cell proliferation, apoptosis, oxidative stress and differentiation, which in turn contributes to hepatic growth, zonation, xenobiotic metabolism and other metabolic processes inherent to the liver. Most of these functions of the Wnt/β-catenin signaling are dictated through the highly temporal and tissue-specific or non-specific transcriptional targets of the pathway. In addition, some of the critical functions such as cell-cell adhesion and perhaps maintenance of various junctions that are critical from an epithelial cell biology perspective are also a function of β-catenin, which is the central component of the canonical Wnt pathway. Various animal models and clinical studies have demonstrated the spectra of Wnt/β-catenin signaling in liver health and disease. Thus therapeutic modulation of this pathway for improved hepatic health is inevitable in the future. The current review discusses the advances in our understanding of the Wnt/β-catenin signaling in liver physiology and pathology especially in hepatic metabolism and various tumors in adult liver and goes on to extrapolate the pre-clinical significance and possible translational implications of such findings.

Recent developments in liver pathology

CONTEXT

Hepatocellular carcinoma is the sixth most common malignancy and the third leading cause of cancer deaths worldwide, making pathologic identification of precursor lesions essential. Recent molecular genetic, pathologic, and clinical data have led to the stratification of hepatic adenomas into subgroups with unique molecular profiles and varying potential for malignant transformation, as well as to the reclassification of telangiectatic focal nodular hyperplasia as telangiectatic adenoma. Clinical, morphologic, and molecular genetic studies have also established juvenile hemochromatosis and pediatric nonalcoholic steatohepatitis as entities distinct from their adult counterparts.

OBJECTIVE

To review the recent molecular genetic characterization of telangiectatic hepatic adenomas and juvenile hemochromatosis, as well as the recent clinicopathologic characterization of pediatric nonalcoholic steatohepatitis.

DATA SOURCES

Literature review, personal experience, and material from the University of Chicago.

CONCLUSIONS

Basic science and translational research have led to the classification of many pathologic entities of the liver according to molecular genetic and protein expression profiles that correspond to traditional morphologic categories. Insights into signal transduction pathways that are activated in, and protein expression patterns unique to, an individual disease may lead to the development of new therapeutic agents and novel diagnostic biomarkers.

Expression of xenobiotic and steroid hormone metabolizing enzymes in hepatocellular tumors of the non-cirrhotic liver

Hepatocellular adenomas (HCA) and some hepatocellular carcinomas (HCC) arise in the non-cirrhotic liver. Although the liver is involved in the metabolism of a huge number of exogenous and endogenous substances, little is known about the role of metabolic enzymes in the development of liver tumors in the absence of cirrhosis. We analyzed the expression of glutathione S-transferases (GST) and cytochrome P450 enzymes (CYP) in 23 HCA, 20 HCC, and 22 focal nodular hyperplasias (FNH) using immunohistochemistry. The liver tissue revealed consistent specific staining for GST alpha, CYP1A1, 1A2, 2E1, and 3A4. In HCA and HCC, GST alpha expression was significantly reduced (p<0.001 and 0.043). Reduced GST alpha expression was significantly associated with steatosis in HCA and HCC (n=12, p=0.006), but not in non-neoplastic liver tissue. CYP3A4 expression was also reduced in HCA and HCC (p=0.03 and 0.02), and this was correlated with diabetes mellitus type 2 (p=0.02). In conclusion, HCA and HCC revealed changes in the expression of certain metabolic enzymes as compared with the non-neoplastic liver tissue or FNH. Therefore, reduced expression of GST alpha and CYP3A4 may indicate specific metabolic defects in the tumor tissue characterizing subgroups of HCA and HCC.

Functional targets of the monogenic diabetes transcription factors HNF-1alpha and HNF-4alpha are highly conserved between mice and humans

OBJECTIVE

The evolutionary conservation of transcriptional mechanisms has been widely exploited to understand human biology and disease. Recent findings, however, unexpectedly showed that the transcriptional regulators hepatocyte nuclear factor (HNF)-1alpha and -4alpha rarely bind to the same genes in mice and humans, leading to the proposal that tissue-specific transcriptional regulation has undergone extensive divergence in the two species. Such observations have major implications for the use of mouse models to understand HNF-1alpha- and HNF-4alpha-deficient diabetes. However, the significance of studies that assess binding without considering regulatory function is poorly understood.

RESEARCH DESIGN AND METHODS

We compared previously reported mouse and human HNF-1alpha and HNF-4alpha binding studies with independent binding experiments. We also integrated binding studies with mouse and human loss-of-function gene expression datasets.

RESULTS

First, we confirmed the existence of species-specific HNF-1alpha and -4alpha binding, yet observed incomplete detection of binding in the different datasets, causing an underestimation of binding conservation. Second, only a minor fraction of HNF-1alpha- and HNF-4alpha-bound genes were downregulated in the absence of these regulators. This subset of functional targets did not show evidence for evolutionary divergence of binding or binding sequence motifs. Finally, we observed differences between conserved and species-specific binding properties. For example, conserved binding was more frequently located near transcriptional start sites and was more likely to involve multiple binding events in the same gene.

CONCLUSIONS

Despite evolutionary changes in binding, essential direct transcriptional functions of HNF-1alpha and -4alpha are largely conserved between mice and humans.

Frequent in-frame somatic deletions activate gp130 in inflammatory hepatocellular tumours

Inflammatory hepatocellular adenomas are benign liver tumours defined by the presence of inflammatory infiltrates and by the increased expression of inflammatory proteins in tumour hepatocytes. Here we show a marked activation of the interleukin (IL)-6 signalling pathway in this tumour type; sequencing candidate genes pinpointed this response to somatic gain-of-function mutations in the IL6ST gene, which encodes the signalling co-receptor gp130. Indeed, 60% of inflammatory hepatocellular adenomas harbour small in-frame deletions that target the binding site of gp130 for IL-6, and expression of four different gp130 mutants in hepatocellular cells activates signal transducer and activator of transcription 3 (STAT3) in the absence of ligand. Furthermore, analysis of hepatocellular carcinomas revealed that rare gp130 alterations are always accompanied by beta-catenin-activating mutations, suggesting a cooperative effect of these signalling pathways in the malignant conversion of hepatocytes. The recurrent gain-of-function gp130 mutations in these human hepatocellular adenomas fully explains activation of the acute inflammatory phase observed in tumourous hepatocytes, and suggests that similar alterations may occur in other inflammatory epithelial tumours with STAT3 activation.

ATP citrate lyase: activation and therapeutic implications in non-small cell lung cancer

Enhanced glucose and lipid metabolism is one of the most common properties of malignant cells. ATP citrate lyase (ACLY) is a key enzyme of de novo fatty acid synthesis responsible for generating cytosolic acetyl-CoA and oxaloacetate. To evaluate its role in lung cancer progression, we here analyzed ACLY expression in a subset of human lung adenocarcinoma cell lines and showed a relationship with the phosphatidyl-inositol-3 kinase-Akt pathway. The introduction of constitutively active Akt into cells enhanced the phosphorylation of ACLY, whereas dominant-negative Akt caused attenuation. In human lung adenocarcinoma samples, ACLY activity was found to be significantly higher than in normal lung tissue. Immunohistochemical analysis further showed phosphorylated ACLY overexpression in 162 tumors, well-correlating with stage, differentiation grade, and a poorer prognosis. Finally, to show the therapeutic potential and mechanism of ACLY inhibition for lung cancer treatment, we assessed the effect of RNA interference targeting ACLY on lipogenesis and cell proliferation in A549 cells. ACLY inhibition resulted in growth arrest in vitro and in vivo. Interestingly, increased intracellular lipids were found in ACLY knockdown cells, whereas de novo lipogenesis was inhibited. Supplementation of insulin could rescue the proliferative arrest elicited by ACLY inhibition; however, in contrast, fatty acid palmitate induced cell death. Taken together, these findings suggest that ACLY is involved in lung cancer pathogenesis associated with metabolic abnormality and might offer a novel therapeutic target.

Hepatocellular adenomas: magnetic resonance imaging features as a function of molecular pathological classification

Hepatocellular adenomas (HCAs) are a group of benign tumors forming three molecular pathological subgroups: (1) hepatocyte nuclear factor 1alpha (HNF-1alpha)-inactivated, (2) beta-catenin-activated, and (3) inflammatory. Some HCAs present both beta-catenin activation and inflammation. We analyzed magnetic resonance imaging (MRI) data for correlations between features on imaging and pathological classification of HCAs. We included 50 cases for which pathology specimens were classified into three groups based on immunohistochemical staining. Two characteristic MRI profiles were identified corresponding to HNF-1alpha-inactivated and inflammatory HCAs. Fifteen HCAs were HNF-1alpha-inactivated. The corresponding lesions showed (1) diffuse signal dropout on T1-weighted chemical shift sequence due to steatosis, (2) isosignal or slight hypersignal on T2-weighted (T2W) images, and (3) moderate enhancement in the arterial phase, with no persistent enhancement in the portal venous and delayed phases. For the diagnosis of HNF-1alpha-inactivated HCA, the positive predictive value of homogeneous signal dropout on chemical shift images was 100%, the negative predictive value was 94.7%, the sensitivity was 86.7%, and the specificity was 100%. Twenty-three HCAs were inflammatory and showed (1) an absence or only focal signal dropout on chemical shift sequence; (2) marked hypersignal on T2W sequences, with a stronger signal in the outer part of the lesions, correlating with sinusoidal dilatation areas; and (3) strong arterial enhancement, with persistent enhancement in the portal venous and delayed phases. Marked hypersignal on T2W sequences associated with delayed persistent enhancement had a positive predictive value of 88.5%, a negative predictive value of 84%, a sensitivity of 85.2%, and a specificity of 87.5% for the diagnosis of inflammatory HCA.

CONCLUSION

HNF-1alpha-mutated HCAs and inflammatory HCAs were associated with specific MRI patterns related to diffuse fat repartition and sinusoidal dilatation, respectively.

MicroRNA profiling in hepatocellular tumors is associated with clinical features and oncogene/tumor suppressor gene mutations

Molecular classifications defining new tumor subtypes have been recently refined with genetic and transcriptomic analyses of benign and malignant hepatocellular tumors. Here, we performed microRNA (miRNA) profiling in two series of fully annotated liver tumors to uncover associations between oncogene/tumor suppressor mutations and clinical and pathological features. Expression levels of 250 miRNAs in 46 benign and malignant hepatocellular tumors were compared to those of 4 normal liver samples with quantitative reverse-transcriptase polymerase chain reaction. miRNAs associated with genetic and clinical characteristics were validated in a second series of 43 liver tumor samples and 16 nontumor samples. miRNA profiling unsupervised analysis classified samples in unique clusters characterized by histological features (tumor/nontumor, P < 0.001; benign/malignant tumors, P < 0.01; inflammatory adenoma and focal nodular hyperplasia, P < 0.01), clinical characteristics [hepatitis B virus (HBV) infection, P < 0.001; alcohol consumption, P < 0.05], and oncogene/tumor suppressor gene mutations [beta-catenin, P < 0.01; hepatocyte nuclear factor 1alpha (HNF1alpha), P < 0.01]. Our study identified and validated miR-224 overexpression in all tumors and miR-200c, miR-200, miR-21, miR-224, miR-10b, and miR-222 specific deregulation in benign or malignant tumors. Moreover, miR-96 was overexpressed in HBV tumors, and miR-126* was down-regulated in alcohol-related hepatocellular carcinoma. Down-regulations of miR-107 and miR-375 were specifically associated with HNF1alpha and beta-catenin gene mutations, respectively. miR-375 expression was highly correlated to that of beta-catenin-targeted genes as miR-107 expression was correlated to that of HNF1alpha in a small interfering RNA cell line model. Thus, this strongly suggests that beta-catenin and HNF1alpha could regulate miR-375 and miR-107 expression levels, respectively.

CONCLUSION

Hepatocellular tumors may have a distinct miRNA expression fingerprint according to malignancy, risk factors, and oncogene/tumor suppressor gene alterations. Dissecting these relationships provides a new hypothesis to understand the functional impact of miRNA deregulation in liver tumorigenesis and the promising use of miRNAs as diagnostic markers.

Hepatocellular adenoma: what is new in 2008

Patients (85%) with hepatocellular adenoma (HCA) are women taking oral contraceptives. They can be divided into four subgroups according to their genotype/phenotype features. (1) Hepatocyte nuclear factor 1α (HNF1α) biallelic somatic mutations are observed in 35% of the HCA cases. It occurs in almost all cases in women. HNF1α-mutated HCA are most of the time, highly steatotic, with a lack of expression of liver fatty acid binding protein (LFABP) in immunohistochemistry analyses. Adenomatosis is frequently detected in this context. An HNF1α germline mutation is observed in less than 5% of HCA cases and can be associated with MODY 3 diabetes. (2) An activating β-catenin mutation was found in 10% of HCA. These β-catenin activated HCAs are observed in men and women, and specific risk factors, such as male hormone administration or glycogenosis, are associated with their development. Immunohistochemistry studies show that these HCAs overexpress β-catenin (nuclear and cytoplasmic) and glutamine synthetase. This group of tumours has a higher risk of malignant transformation into hepatocellular carcinoma. (3) Inflammatory HCAs are observed in 40% of the cases, and they are most frequent in women but are also found in men. Lesions are characterised by inflammatory infiltrates, dystrophic arteries, sinusoidal dilatation and ductular reaction. They express serum amyloid A and C-reactive protein. In this group, GGT is frequently elevated, with a biological inflammatory syndrome present. Also, there are more overweight patients in this group. An additional 10% of inflammatory HCAs express β-catenin, and are also at risk of malignant transformation. (4) Currently, less than 10% of HCAs are unclassified. It is hoped that in the near future it will be possible with clinical, biological and imaging data to predict in which of the 2 major groups (HNF1α-mutated HCA and inflammatory HCA) the patient belongs and to propose better guidelines in terms of surveillance and treatment.

Molecular pathogenesis of focal nodular hyperplasia and hepatocellular adenoma

Focal nodular hyperplasia (FNH) and hepatocellular adenomas (HCAs) are benign tumors that occur in otherwise normal liver parenchyma. FNH is considered to be the result of a hyperplastic response to increased blood flow secondary to vascular malformations. Most FNH are polyclonal and to date, the molecular pathway and mechanisms that are altered in FNH have yet to be elucidated. In contrast, HCAs are consistently monoclonal tumors, which have been divided up into three subtypes of tumors depending on the molecular alteration detected in the tumors: HNF1alpha inactivation, beta-catenin activation and/or an acute inflammatory response in the tumor. These molecular features are closely related to clinical and pathological characteristics, and one of the most critical correlations is the higher risk of malignant transformation for beta-catenin activated HCA cases. Moreover, various risk factors, such as oral contraception and obesity, are associated with HCA occurrence and may collaborate with constitutional genetic predisposition related to HNF1alpha or CYP1B1 germline mutations. Altogether, the recent identification of different molecular pathways that contribute to tumor development has significantly increased our knowledge of benign hepatocellular tumorigenesis. These findings may modify our clinical practice, particularly in the diagnosis and follow-up of HCA patients.

Comparative analysis of the protein profiles from primary gastric tumors and their adjacent regions: MAWBP could be a new protein candidate involved in gastric cancer

The study of tumor biomarkers is generally facilitated by the adoption of proteomic strategies. With limitations of techniques and individual varieties of biological samples, the biomarkers for gastric cancer (GC) have not reached a common agreement derived from the proteomic investigations. Herein, we reported a new set of data for screening the biomarkers from the gastric tissues, on the basis of the proteomic strategy developed in our laboratory. Ten pairs of the clinic samples were collected and treated with protein extraction. The gastric proteins were well-resolved by 2-DE, and the GC-associated proteins were identified by MALDI-TOF/TOF MS following image analysis, including 12 up-regulated and 13 down-regulated unique ones. MAWBP was found to be one of the new GC proteins which appeared with lower expression in the GC tissues. We expanded a systematical examination to deeply pursue the relevance between MAWBP and GC. Quantitatively, we measured the expression of MAWBP with Western blot and Real-Time PCR. Extendedly, we estimated the existence of MAWBP with immunohistochemical staining in a large number of the GC cases. Specifically, we inquired whether MAWD, a protein with high affinity to MAWBP, could coexpress and interact with MAWBP in vivo. On the basis of all the results, we concluded that MAWBP could be a new GC-related protein even though its physiological roles remain unexplored.