P53 gene and Wnt signaling in benign neoplasms: beta-catenin mutations in hepatic adenoma but not in focal nodular hyperplasia

Clonality and allelotype analyses of focal nodular hyperplasia compared with hepatocellular adenoma and carcinoma

AIM: To identify clonality and genetic alterations in focal nodular hyperplasia (FNH) and the nodules derived from it.

METHODS: Twelve FNH lesions were examined. Twelve hepatocellular adenomas (HCAs) and 22 hepatocellular carcinomas (HCCs) were used as references. Nodules of different types were identified and isolated from FNH by microdissection. An X-chromosome inactivation assay was employed to describe their clonality status. Loss of heterozygosity (LOH) was detected, using 57 markers, for genetic alterations.

RESULTS: Nodules of altered hepatocytes (NAH), the putative precursors of HCA and HCC, were found in all the FNH lesions. Polyclonality was revealed in 10 FNH lesions from female patients, and LOH was not detected in any of the six FNH lesions examined, the results apparently showing their polyclonal nature. In contrast, monoclonality was demonstrated in all the eight HCAs and in four of the HCCs from females, and allelic imbalances were found in the HCAs (9/9) and HCCs (15/18), with chromosomal arms 11p, 13q and 17p affected in the former, and 6q, 8p, 11p, 16q and 17p affected in the latter lesions in high frequencies (≥ 30%). Monoclonality was revealed in 21 (40%) of the 52 microdissected NAH, but was not found in any of the five ordinary nodules. LOH was found in all of the 13 NAH tested, being highly frequent at six loci on 8p, 11p, 13q and 17p.

CONCLUSION: FNH, as a whole, is polyclonal, but some of the NAH lesions derived from it are already neoplastic and harbor similar allelic imbalances as HCAs.

Chromosomal and genetic alterations in human hepatocellular adenomas associated with type Ia glycogen storage disease

Hepatocellular adenoma (HCA) is a frequent long-term complication of glycogen storage disease type I (GSD I) and malignant transformation to hepatocellular carcinoma (HCC) is known to occur in some cases. However, the molecular pathogenesis of tumor development in GSD I is unclear. This study was conducted to systematically investigate chromosomal and genetic alterations in HCA associated with GSD I. Genome-wide SNP analysis and mutation detection of target genes was performed in ten GSD Ia-associated HCA and seven general population HCA cases for comparison. Chromosomal aberrations were detected in 60% of the GSD Ia HCA and 57% of general population HCA. Intriguingly, simultaneous gain of chromosome 6p and loss of 6q were only seen in GSD Ia HCA (three cases) with one additional GSD I patient showing submicroscopic 6q14.1 deletion. The sizes of GSD Ia adenomas with chromosome 6 aberrations were larger than the sizes of adenomas without the changes (P = 0.012). Expression of IGF2R and LATS1 candidate tumor suppressor genes at 6q was reduced in more than 50% of GSD Ia HCA that were examined (n = 7). None of the GSD Ia HCA had biallelic mutations in the HNF1A gene. These findings give the first insight into the distinct genomic and genetic characteristics of HCA associated with GSD Ia. These results strongly suggest that chromosome 6 alterations could be an early event in the liver tumorigenesis in GSD I, and may be in general population. These results also suggest an interesting relationship between GSD Ia HCA and steps to HCC transformation.

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.

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.

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.

Wnt signaling in liver cancer

Hepatocellular carcinoma (HCC) is a major cause of cancer death worldwide. As in many other types of cancer, aberrant activation of the canonical Wnt/beta-catenin signaling pathway is an important contributor to tumorigenesis. In HCC this frequently occurs through mutations in the N-terminal region of beta-catenin that stabilize the protein and permit an elevated level of constitutive transcriptional activation by beta-catenin/TCF complexes. In this article we review the abundant evidence that Wnt/beta-catenin signaling contributes to liver carcinogenesis. We also discuss what is known about the roles of Wnt signaling in liver development, regeneration, and stem cell behavior, in an effort to understand the mechanisms by which activation of the canonical Wnt pathway promotes tumor formation in this organ. The Wnt/beta-catenin pathway presents itself as an attractive target for developing novel rational therapies for HCC, a disease for which few successful treatment strategies are currently available.

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.

Surgical management of hepatocellular adenoma: take it or leave it?

BACKGROUND

Hepatocellular adenoma (HA) is a rare benign tumor of the liver. Surgical resection is generally indicated to reduce risks of hemorrhage and malignant transformation. We sought to evaluate clinical presentation, surgical management, and outcomes of patients with HA at our institution.

METHODS

We performed a retrospective review of 41 patients who underwent surgical resection for HA between 1988 and 2007.

RESULTS

Thirty-eight patients were women, and the median age at presentation was 36 years (range, 19-65 years). The most common clinical presentation was abdominal pain (70%) followed by incidental radiological finding (17%). Twenty-two patients had a history of oral contraceptive use. Median number of HA was one (range, 1-3). There were 32 open cases (3 trisectionectomy, 15 hemihepatectomy, 7 sectionectomy, 4 segmentectomy, and 3 wedge resection), and 9 laparoscopic cases (1 hemihepatectomy, 5 sectionectomy, 1 segmentectomy, and 2 wedge resection). The median estimated blood loss was 225 mL (range, 0-3400 mL). The median length of stay was 6 days (range, 1-15 days). Surgical morbidities included pleural effusion requiring percutaneous drainage (n = 2), pneumonia (n = 1), and wound infection (n = 1). There was no perioperative mortality. Twelve patients had hemorrhage from HA. Hepatocellular carcinoma was observed in two patients with HA. Median follow-up was 23 months (range, 1-194 months), at which time all patients were alive.

CONCLUSION

In view of 29% hemorrhagic and 5% malignant complication rates, we recommend surgical resection over observation if patient comorbidities and anatomic location of HA are favorable. A laparoscopic approach can be safely used in selected cases.

The beta-catenin pathway is activated in focal nodular hyperplasia but not in cirrhotic FNH-like nodules

BACKGROUND/AIMS

Focal nodular hyperplasias (FNHs) are benign liver lesions considered to be a hyperplastic response to increased blood flow in normal liver. In contrast, FNH-like lesions/nodules occur in cirrhotic liver but share similar histopathological features. We conducted a transcriptome analysis to identify biological pathways deregulated in FNH.

METHODS

Gene expression profiles obtained in FNH and normal livers were compared. Differentially-expressed genes were validated using quantitative-RT-PCR in 70 benign liver tumors including FNH-like lesions.

RESULTS

Among the deregulated genes in FNHs, 19 displayed physiological restricted distribution in the normal liver. All six perivenous genes were up-regulated in FNH, whereas 13 periportal genes were down-regulated. Almost all these genes are known to be regulated by beta-catenin. Glutamine synthetase was markedly overexpressed in anastomosed areas usually centered on visible veins. Moreover, activated hypophosphorylated beta-catenin protein accumulated in FNH in the absence of activating mutations. These results suggest the zonated activation of the beta-catenin pathway in FNH, whereas the other benign hepatocellular tumors, including FNH-like lesions, demonstrated an entirely different pattern of beta-catenin expression.

CONCLUSIONS

In FNH, increased activation of the beta-catenin pathway was found restricted to enlarged perivenous areas. FNH-like nodules may have a different pathogenetic origin.

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.

Malignant transformation of hepatic adenomas

Hepatic adenomas are benign neoplasms of the liver that occur in several well-defined clinical settings, but principally that of excess hormone exposure. They have a small but poorly characterized risk of malignant degeneration. The clinical presentation and pathological findings were reviewed for all hepatic adenomas resected between January 1, 2003 and July 1, 2006. Immunohistochemistry for p53, beta-catenin and alpha-fetoprotein (AFP) were performed on those cases with malignant transformation and exon 3 of beta-catenin was amplified and sequenced. A total of 17 hepatic adenomas were resected and 3 showed malignant transformation. All three cases were in women with an age range of 23-33 years. The clinical presentations were vague abdominal pain. Histologically, the malignant transformation occurred within otherwise typical hepatic adenomas. Two of three cases showed patchy atypia throughout the hepatic adenoma. The hepatocellular carcinoma arose as distinct nodules directly within the adenomas, effectively ruling out synchronous lesions. The hepatocellular carcinomas were unifocal in two cases and multifocal in one case with the greatest dimensions of the hepatocellular carcinoma being 2.5, 2.2, and 1 cm. Immunostains for AFP and beta-catenin were negative in both the hepatic adenomas and areas of hepatocellular carcinoma. p53 immunostaining was positive within the areas of malignant transformation in one case. No mutations or deletions were seen in exon 3 of the beta-catenin gene for either the adenomas or the carcinoma. In conclusion, two of the cases that developed hepatocellular carcinomas showed cytological atypia in the background adenoma. The hepatocellular carcinomas arose as distinct nodules within the adenomas. No common molecular pathway of hepatocellular carcinogenesis was observed by examining AFP, beta-catenin, and p53 immunostains and no beta-catenin mutations or deletions were found.

Advances in the relationship between canonical Wnt pathway and liver

A number of studies have demonstrated the important roles of canonical Wnt pathway in the essential physiologic processes in liver, such as development, growth, regeneration, zonation, metabolism, and oxidative stress. Likewise, there have been advances have been made in understanding the role of β-catenin in the development of various liver diseases. Studies of pathological specimens and rodent models of liver diseases have demonstrated aberrations in the canonical Wnt pathway in conditions ranging from hepatitis to hepatocellular carcinoma (HCC). In this article, we review the above roles of canonical Wnt pathway in liver health and diseases.

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.

Hepatocellular adenoma subtype classification using molecular markers and immunohistochemistry

Hepatocellular adenomas (HCA) with activated beta-catenin present a high risk of malignant transformation. To permit robust routine diagnosis to allow for HCA subtype classification, we searched new useful markers. We analyzed the expression of candidate genes by quantitative reverse transcription polymerase chain reaction QRT-PCR followed by immunohistochemistry to validate their specificity and sensitivity according to hepatocyte nuclear factor 1 alpha (HNF1alpha) and beta-catenin mutations as well as inflammatory phenotype. Quantitative RT-PCR showed that FABP1 (liver fatty acid binding protein) and UGT2B7 were downregulated in HNF1alpha-inactivated HCA (P <or= 0.0002); GLUL (glutamine synthetase) and GPR49 overexpression were associated with beta-catenin-activating mutations (P <or= 0.0005), and SAA2 (serum amyloid A2) and CRP (C-reactive protein) were upregulated in inflammatory HCA (P = 0.0001). Immunohistochemistry validation confirmed that the absence of liver-fatty acid binding protein (L-FABP) expression rightly indicated HNF1alpha mutation (100% sensitivity and specificity), the combination of glutamine synthetase overexpression and nuclear beta-catenin staining were excellent predictors of beta-catenin-activating mutation (85% sensitivity, 100% specificity), and SAA hepatocytic staining was ideal to classify inflammatory HCA (91% sensitivity and specificity). Finally, a series of 93 HCA was unambiguously classified using our 4 validated immunohistochemical markers. Importantly, new associations were revealed for inflammatory HCA defined by SAA staining with frequent hemorrhages (P = 0.003), telangiectatic phenotype (P < 0.001), high body mass index, and alcohol intake (P <or= 0.04). Previously described associations were confirmed and in particular the significant association between beta-catenin-activated HCA and hepatocellular carcinomas (HCC) at diagnosis or during follow-up (P < 10(-5)).

CONCLUSION

We refined HCA classification and its phenotypic correlations, providing a routine test to classify hepatocellular adenomas using simple and robust immunohistochemistry.

Telangiectatic adenoma: an entity associated with increased body mass index and inflammation

What were previously called telangiectatic focal nodular hyperplasias are in fact true adenomas with telangiectatic features (TAs) without overt characterized genetic abnormalities. The aim of our study was to review a surgical series of TAs in order to describe clinical, biological, and radiological findings of these lesions and to evaluate their outcomes. From January 1996 to November 2005, 284 patients with benign hepatocellular nodules underwent surgical resection at Beaujon Hospital. Among them, 32 TAs from 27 patients were diagnosed. Ninety-two percent of the patients were women. Mean age was 38 years (range 17-63). Mean body mass index was 28 (range 18-49), with 16 patients being overweight. Symptoms revealed lesions in 10 patients. In 13 patients, TA was associated with another benign liver lesion. Mean size of the TAs was 5 cm (range 1-17 cm). Histological analysis showed cellular atypias in 6 cases (19%), steatosis in 17 cases (53%), vascular changes in 19 cases (59%), and significant inflammatory infiltrate in 29 cases (91%). In 1 case, the TA had foci of well-differentiated hepatocellular carcinoma. In 18 of the 26 cases (69%), adjacent liver showed significant steatosis. Serum biomarkers of inflammation were increased in 90% of patients (19 of 22). After surgical resection, inflammatory marker levels returned to normal values in all patients tested.

CONCLUSION

This study has shown that TAs occur in a characteristic background of overweight patients and are often associated with a biological inflammatory syndrome. Moreover, a TA may progress to malignancy.

Genotype phenotype classification of hepatocellular adenoma

Studies that compare tumor genotype with phenotype have provided the basis of a new histological/molecular classification of hepatocellular adenomas. Based on two molecular criteria (presence of a TCF1/HNF1α or β-catenin mutation), and an additional histological criterion (presence or absence of an inflammatory infiltrate), subgroups of hepatocellular adenoma can be defined and distinguished from focal nodular hyperplasia. Analysis of 96 hepatocellular adenomas performed by a French collaborative network showed that they can be divided into four broad subgroups: the first one is defined by the presence of mutations in TCF1 gene inactivating the hepatocyte nuclear factor 1 (HNF1α); the second by the presence of β-catenin activating mutations; the category without mutations of HNF1α or β-catenin is further divided into 2 subgroups depending on the presence or absence of inflammation. Therefore, the approach to the diagnosis of problematic benign hepatocytic nodules may be entering a new era directed by new molecular information. It is hoped that immunohistological tools will improve significantly diagnosis of liver biopsy in our ability to distinguish hepatocellular adenoma from focal nodular hyperplasia (FNH), and to delineate clinically meaningful entities within each group to define the best clinical management. The optimal care of patients with a liver nodule will benefit from the recent knowledge coming from molecular biology and the combined expertise of hepatologists, pathologists, radiologists, and surgeons.

WNT/beta-catenin signaling in liver health and disease

Wnt/beta-catenin signaling is emerging as a forerunner for its critical roles in many facets of human biology. Its roles in embryogenesis, organogenesis, and maintaining tissue and organ homeostasis demonstrate its munificent character. Its roles in pathological conditions such as cancer and other human disorders such as inflammatory disorders and fibrosis reveal its villainous disposition. In liver, it also maintains its dual personality and is clearly of essence in several physiological events such as development, regeneration, and growth. Its aberrant activation is also evident in many different tumors of the liver, and recent studies are beginning to identify its role in additional hepatic pathological conditions. It is contributing to liver physiology and pathology by regulating various basic cellular events, including differentiation, proliferation, survival, oxidative stress, morphogenesis, and others. This review discusses the contribution of the Wnt/beta-catenin signaling pathway in these events and simultaneously provides an essential overview of the major developments in the field of Wnt/beta-catenin and liver pathobiology. In addition, areas that are currently deficient or understudied are identified and discussed along with the avenues of translational and clinical relevance.

Association of CYP1B1 germ line mutations with hepatocyte nuclear factor 1alpha-mutated hepatocellular adenoma

Biallelic somatic mutations of TCF1 coding for hepatocyte nuclear factor 1alpha (HNF1alpha) are found in 50% of the hepatocellular adenoma (HCA) cases usually associated with oral contraception. In rare cases, HNF1alpha germ line mutations could also predispose to familial adenomatosis. In order to identify new genetic factors predisposing to HNF1alpha-mutated HCA, we searched for mutations in genes involved in the metabolism of estrogen. For 10 genes (CYP1A1, CYP1A2, CYP3A4, CYP3A5, COMT, UGT2B7, NQO1, GSTM1, GSTP1, and GSTT1), we did not find mutations nor differences in the allele distribution among 32 women presenting HNF1alpha-mutated adenomas compared with 58 controls. In contrast, we identified a CYP1B1 germ line heterozygous mutation in 4 of 32 women presenting HNF1alpha-mutated adenomas compared with none in 58 controls. We confirmed these results with the identification of four additional CYP1B1 mutations in a second series of 26 cases. No mutations were found in the control group, which was extended to 98 individuals, and only a known rare genetic variant was observed in two controls (P = 0.0003). We did an ethoxyresorufin O-deethylase assay to evaluate the functional consequence of the CYP1B1 mutations. We found reduced enzymatic activity in each CYP1B1 variant. In addition, an E229K CYP1B1 mutation was found in a woman with a germ line HNF1alpha mutation in a familial adenomatosis context. In this large family, all three patients with adenomatosis bore both HNF1 and CYP1B1 germ line mutations. In conclusion, our data suggested that CYP1B1 germ line-inactivating mutations might increase the incidence of HCA in women with HNF1alpha mutations.

Hepatocellular adenoma displaying a HNF1alpha inactivation in a patient with familial adenomatous polyposis coli

Patients with familial adenomatous polyposis coli (FAP) may rarely develop hepatocellular adenoma. Here we report the case of a 37-year-old FAP woman presenting a hepatocellular adenoma after oestroprogestative oral contraception use. In this steatotic adenoma, we identified an inactivating biallelic mutation of HNF1alpha. In addition to the known germline APC mutation Q1062fs, we did not find an inactivation of the second APC allele nor an activation of the beta-catenin target genes GLUL and GPR49. Our findings contrast with two hepatocellular adenoma cases related to FAP, for which a biallelic inactivation of the APC gene was previously described. Altogether, these results suggest that benign hepatocellular carcinogenesis may be dependent on or independent of the Wnt/beta-catenin pathway in patients with FAP.

[Hepatocellular adenoma. Malignancy potential and differentiation from hepatocellular carcinoma]

In contrast to hepatocellular carcinoma (HCC), very few molecular pathological studies have been carried out on hepatocellular adenoma (HCA). Particularly from the surgical point of view, based on views passed on verbally and in the literature of the 1970s and 1980s, a possible degeneration of the HCA provides grounds for operating. Published cases of transitions from HCA into HCC were evaluated on the basis of today's morphological standards. A comparison was made between the patterns of new molecular pathological studies of HCA, above all the work of our own groups, and those of HCC. The results speak against the suggestion that a typical solitary HCA in pre-menopausal women is a precursor lesion of HCC. After a critical review of the literature, only one casuistic case of a transition of HCA to HCC under a hormone therapy, which is no longer practiced today, remained. A limitation of particular HCA in genetic and metabolic diseases, children, adult males, adenomatosis, and HCA-like tumors with known risk factors of HCC would seem pragmatically meaningful. With classic HCA, however, the oncological indication for surgery does not apply. A prerequisite is a histological clarification, if necessary with the support of molecular pathological methods.

Genetics of hepatocellular tumors

Numerous genetic alterations are accumulated during the process of hepatocarcinogenesis. These genetic alterations can be divided into two groups. The first set of genetic alterations is specific of hepatocellular tumor risk factors. It includes integration of hepatitis B virus (HBV) DNA, R249S TP53 (tumor protein p53) mutation in aflatoxin B1-exposed patients, KRAS mutations related to vinyl chloride exposure, hepatocyte nuclear factor 1alpha (HNF1alpha) mutations associated to hepatocellular adenomas and adenomatosis polyposis coli (APC) germline mutations predisposing to hepatoblastomas. The second set of genetic alterations are etiological nonspecific, it includes recurrent gains and losses of chromosomes, alteration of TP53 gene, activation of WNT/beta-catenin pathway through CTNNB1/beta-catenin and AXIN (axis inhibition protein) mutations, inactivation of retinoblastoma and IGF2R (insulin-like growth factor 2 receptor) pathways through inactivation of RB1 (retinoblastoma 1), P16 and IGF2R. Comprehensive analyses of these genetic alterations have defined two pathways of hepatocarcinogenesis according to the presence or the absence of chromosomal instability. Hepatitis B virus and poorly differentiated tumors are related to chromosome instable tumors associated with frequent TP53 mutations, whereas non-HBV and well-differentiated tumors are related to chromosomal stable samples that are frequently beta-catenin activated. These classifications have clinical relevance as genetic alterations may also be related to prognosis.

Genotype-phenotype correlation in hepatocellular adenoma: new classification and relationship with HCC

Hepatocellular adenomas are benign tumors that can be difficult to diagnose. To refine their classification, we performed a comprehensive analysis of their genetic, pathological, and clinical features. A multicentric series of 96 liver tumors with a firm or possible diagnosis of hepatocellular adenoma was reviewed by liver pathologists. In all cases, the genes coding for hepatocyte nuclear factor 1alpha (HNF1alpha) and beta-catenin were sequenced. No tumors were mutated in both HNF1alpha and beta-catenin enabling tumors to be classified into 3 groups, according to genotype. Tumors with HNF1alpha mutations formed the most important group of adenomas (44 cases). They were phenotypically characterized by marked steatosis (P < 10(-4)), lack of cytological abnormalities (P < 10(-6)), and no inflammatory infiltrates (P < 10(-4)). In contrast, the group of tumors defined by beta-catenin activation included 13 lesions with frequent cytological abnormalities and pseudo-glandular formation (P < 10(-5)). The third group of tumors without mutation was divided into two subgroups based on the presence of inflammatory infiltrates. The subgroup of tumors consisting of 17 inflammatory lesions, resembled telangiectatic focal nodular hyperplasias, with frequent cytological abnormalities (P = 10(-3)), ductular reaction (P < 10(-2)), and dystrophic vessels (P = .02). In this classification, hepatocellular carcinoma associated with adenoma or borderline lesions between carcinoma and adenoma is found in 46% of the beta-catenin-mutated tumors whereas they are never observed in inflammatory lesions and are rarely found in HNF1alpha mutated tumors (P = .004). In conclusion, the molecular and pathological classification of hepatocellular adenomas permits the identification of strong genotype-phenotype correlations and suggests that adenomas with beta-catenin activation have a higher risk of malignant transformation.

Overexpression of regenerating islet-derived 1 alpha and 3 alpha genes in human primary liver tumors with β-catenin mutations

The Wnt/beta-catenin signaling pathway is activated in many human hepatocellular carcinomas (HCC). We tried to identify the genes involved in carcinogenesis and progression of HCC with beta-catenin mutations. We used PCR-based subtractive hybridization to compare gene expression between malignant and benign components of a human HCC occurring in pre-existing adenoma activated for beta-catenin. Two of the genes identified belong to the Regenerating gene (REG) family. They encode the Regenerating islet-derived 3 alpha (REG3A/HIP/PAP/REG-III) and 1 alpha (REG1A) proteins, both involved in liver and pancreatic regeneration and proliferation. Using siRNA directed against beta-catenin, we demonstrated that REG3A is a target of beta-catenin signaling in Huh7 hepatoma cells. The upregulation of REG3A and REG1A expression is significantly correlated to the beta-catenin status in 42 HCC and 28 hepatoblastomas characterized for their beta-catenin status. Thus, we report strong evidence that both genes are downstream targets of the Wnt pathway during liver tumorigenesis.

Pathogenesis of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common malignant tumours worldwide. The major aetiologies and risk factors for the development of HCC are well defined and some of the multiple steps involved in hepatocarcinogenesis have been elucidated in recent years. However, no clear picture of how and in what sequence these factors interact at the molecular level has emerged yet. Malignant transformation of hepatocytes may occur as a consequence of various aetiologies, such as chronic viral hepatitis, alcohol, and metabolic disorders, in the context of increased cellular turnover induced by chronic liver injury, regeneration and cirrhosis. Activation of cellular oncogenes, inactivation of tumour suppressor genes, genomic instability, including DNA mismatch repair defects and impaired chromosomal segregation, overexpression of growth and angiogenic factors, and telomerase activation may contribute to the development of HCC. Overall, HCCs are genetically very heterogeneous tumours. New technologies, including gene expression profiling and proteomic analyses, should allow us to further elucidate the molecular events underlying HCC development and identify novel diagnostic markers as well as therapeutic targets.

Hepatitis B virus X protein is essential for the activation of Wnt/beta-catenin signaling in hepatoma cells

Wnt/beta-catenin signaling contributes to diverse cellular functions, such as Drosophila wing development and colon carcinogenesis. Recently, stabilizing mutations of beta-catenin, a hallmark of Wnt signaling, were documented in significant numbers of primary hepatocellular carcinomas (HCC). However, whether the beta-catenin mutation leads to the activation of Wnt/beta-catenin signaling in hepatoma cells has not been established. We found that Wnt/beta-catenin signaling could be activated by ectopic expression of Wnt-1 in some hepatoma cells, such as Hep3B and PLC/PRF/5 cells, but not in others, such as Huh7 and Chang cells. Importantly, we noted that the former were derived from hepatitis B virus (HBV)-infected livers, whereas the latter were derived from HBV-negative livers. It was then speculated that HBx, a viral regulatory protein of HBV, is involved in activating Wnt/beta-catenin signaling in hepatoma cells. In agreement with this notion, ectopic expression of HBx along with Wnt-1 activated Wnt/beta-catenin signaling in Huh7 cells by stabilizing cytoplasmic beta-catenin. Further, we showed that such stabilization of beta-catenin by HBx was achieved by suppressing glycogen synthase kinase 3 activity via the activation of Src kinase. In conclusion, the data suggest that Wnt-1 is necessary but insufficient to activate Wnt/beta-catenin signaling in hepatoma cells and the enhanced stabilization of beta-catenin by HBx, in addition to Wnt-1, is essential for the activation of Wnt/beta-catenin signaling in hepatoma cells.

Telangiectatic focal nodular hyperplasia: a variant of hepatocellular adenoma

BACKGROUND & AIMS

"Telangiectatic focal nodular hyperplasia" designate atypical lesions considered as variants of focal nodular hyperplasia (FNH). However, because "telangiectatic FNH" share several morphologic patterns with hepatocellular adenomas, classification of such lesions deserve further clarification. Therefore, the aim of the present study was to reconsider the classification of telangiectatic FNH with the help of a molecular approach.

METHODS

Ten telangiectatic FNH, 6 typical FNH, and 6 hepatocellular adenomas were studied. DNA, RNA, and protein from each lesion were extracted. Clonality was assessed by the study of the X chromosome inactivation pattern (HUMARA assay). Angiopoietin (ANGPT-1 and ANGPT-2) mRNA, genes the expression of which is typically modified in FNH, were quantified by a real-time RT-PCR procedure. Protein profiles were analyzed by SELDI-TOF PROTEINCHIP (Cyphergen Biosystem, Inc., Fremont, CA) technology.

RESULTS

Although all informative cases of FNH (5 of 6) and hepatocellular adenomas (6 of 6) were polyclonal and monoclonal, respectively, clonal analysis showed a nonrandom pattern of X chromosome inactivation consistent with a monoclonal lesion in 6 of 8 cases of telangiectatic FNH. The mean value of the ANGPT-1/ANGPT-2 mRNA ratio was 21.4 in FNH, 2.6 in adenomas, and 2.1 in telangiectatic FNH (P <or = 0.001 in telangiectatic FNH vs. FNH). SELDI-TOF PROTEINCHIP profiling and hierarchical clustering analysis showed that all except 1 telangiectatic FNH clustered within the group of hepatocellular adenomas.

CONCLUSIONS

These results show that telangiectatic FNH display a molecular pattern closer to that of hepatocellular adenomas than to FNH and suggest that these lesions should instead be referred to as "telangiectatic hepatocellular adenomas."

ERK1/2 contributes negative regulation to STAT3 activity in HSS-transfected HepG2 cells

Signal transducer and activator of transcription 3 (STAT3) is a recently characterized transcription factor which is essential to liver regeneration. We have previously reported that hepatic stimulator substance (HSS), a novel growth-promoting substance, phosphorylated the epidermal growth factor (EGF) receptors and activated downstream Ras-MAP kinase (extracellular signal-regulated kinases, ERK1/2) cascade. However, whether HSS signal is related to STAT3 pathway remains unclear. The present study is aiming to explore the regulatory effect of activation of ERK1/2 evoked by HSS on STAT3 phosphorylation and STAT3 signaling. Human hepatoma cell line HepG2 was stably transfected with HSS cDNA and HSS expression was measured by Northern blot. The results showed that the transfection of HSS into HepG2 resulted in remarkable increase in cellular proliferation as compared with the non-transfected cells, and it was further proved that the cellular proliferation in the HSS-transfected cells was related to ERK1/2 activation. Treatment of the cells with 50 mM of PD98059, an ERK1/2 specific upstream inhibitor, resulted in ERK1/2 inactivation completely. Inhibition of ERK1/2 allowed the tyrosine of STAT3 to be phosphorylated in a dose-dependent manner to PD98059. Furthermore, transient transfection of STAT3 mutant (STAT3S727A) into HSS-bearing cells could remarkably reverse the inhibitory effect of ERK1/2 on STAT3 phosphorylation. Based upon these results, it is concluded that ERK1/2 negatively modulates STAT3 phosphorylation and this function is dependent on residual serine-727 (S727) of STAT3.

Cellular retinol-binding protein-1 in hepatocellular carcinoma correlates with beta-catenin, Ki-67 index, and patient survival

The cellular retinol-binding protein-1 (CRBP-1) plays a key role in the esterification and intercellular transfer of retinol. By in situ hybridization, immunohistochemistry, and confocal laser scanning microscopy (CLSM), we show that, in normal liver, CRBP-1 is strongly expressed in the cytoplasm of hepatic stellate cells (HSCs) and myofibroblasts (MFs) with only low CRBP-1 levels in hepatocytes. By contrast, in 196 hepatocellular carcinoma (HCC) specimens CRBP-1 expression in MFs was down-regulated in 83%. Patients with high CRBP-1 expression in MFs had a significantly higher 2-year survival as compared with patients with low CRBP-1 expression (52% vs. 29%, respectively; P =.034). An aberrant nuclear CRBP-1 accumulation resulting from cytoplasmic invagination was found in 29% of HCCs. Nuclear CRBP-1 staining correlated positively with a favorable tumor stage (Okuda stage I; P =.01) and negatively with the Ki-67(+) proliferation fraction (PF). A Ki-67(+) PF of > or =10% was associated with a lower 2-year survival probability as compared with patients with a Ki-67(+) PF of <10% (12% vs. 40%, respectively; P =.015). Prognosis did not correlate with the nuclear beta-catenin expression. There was, however, a close correlation between nuclear CRBP-1 inclusions and nuclear beta-catenin staining in HCCs (P =.008), suggesting a cross talk between CRBP-1 and the Wnt/wingless signal transduction pathway. In conclusion, our findings demonstrate that CRBP-1 detection may be useful for the discrimination between nonneoplastic and neoplastic liver cells and suggest that modulation of CRBP-1 expression in HCCs contributes to tumor growth and progression via retinoid-mediated signaling and disruption of cellular vitamin A homeostasis.