Publications by authors named "Laura Amicone"

24 Publications

  • Page 1 of 1

YAP integrates the regulatory Snail/HNF4α circuitry controlling epithelial/hepatocyte differentiation.

Cell Death Dis 2019 10 10;10(10):768. Epub 2019 Oct 10.

Istituto Pasteur-Fondazione Cenci Bolognetti, Department of Molecular Medicine, Sapienza University of Rome, Rome, Italy.

Yes-associated protein (YAP) is a transcriptional co-factor involved in many cell processes, including development, proliferation, stemness, differentiation, and tumorigenesis. It has been described as a sensor of mechanical and biochemical stimuli that enables cells to integrate environmental signals. Although in the liver the correlation between extracellular matrix elasticity (greatly increased in the most of chronic hepatic diseases), differentiation/functional state of parenchymal cells and subcellular localization/activation of YAP has been previously reported, its role as regulator of the hepatocyte differentiation remains to be clarified. The aim of this study was to evaluate the role of YAP in the regulation of epithelial/hepatocyte differentiation and to clarify how a transducer of general stimuli can integrate tissue-specific molecular mechanisms determining specific cell outcomes. By means of YAP silencing and overexpression we demonstrated that YAP has a functional role in the repression of epithelial/hepatocyte differentiation by inversely modulating the expression of Snail (master regulator of the epithelial-to-mesenchymal transition and liver stemness) and HNF4α (master regulator of hepatocyte differentiation) at transcriptional level, through the direct occupancy of their promoters. Furthermore, we found that Snail, in turn, is able to positively control YAP expression influencing protein level and subcellular localization and that HNF4α stably represses YAP transcription in differentiated hepatocytes both in cell culture and in adult liver. Overall, our data indicate YAP as a new member of the HNF4/Snail epistatic molecular circuitry previously demonstrated to control liver cell state. In this model, the dynamic balance between three main transcriptional regulators, that are able to control reciprocally their expression/activity, is responsible for the induction/maintenance of different liver cell differentiation states and its modulation could be the aim of therapeutic protocols for several chronic liver diseases.
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http://dx.doi.org/10.1038/s41419-019-2000-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6787001PMC
October 2019

TGFβ Impairs HNF1α Functional Activity in Epithelial-to-Mesenchymal Transition Interfering With the Recruitment of CBP/p300 Acetyltransferases.

Front Pharmacol 2019 30;10:942. Epub 2019 Aug 30.

Istituto Pasteur Italia-Fondazione Cenci Bolognetti, Department of Molecular Medicine, Sapienza University of Rome, Rome, Italy.

The cytokine transforming growth factor β (TGFβ) plays a crucial role in the induction of both epithelial-to-mesenchymal transition (EMT) program and fibro-cirrhotic process in the liver, where it contributes also to organ inflammation following several chronic injuries. All these pathological situations greatly increase the risk of hepatocellular carcinoma (HCC) and contribute to tumor progression. In particular, late-stage HCCs are characterized by constitutive activation of TGFβ pathway and by an EMT molecular signature leading to the acquisition of invasive and metastatic properties. In these pathological conditions, the cytokine has been shown to induce the transcriptional downregulation of HNF1α, a master regulator of the epithelial/hepatocyte differentiation and of the EMT reverse process, the mesenchymal-to-epithelial transition (MET). Therefore, the restoration of HNF1α expression/activity has been proposed as targeted therapeutic strategy for liver fibro-cirrhosis and late-stage HCCs. In this study, TGFβ is found to trigger an early functional inactivation of HNF1α during EMT process that anticipates the effects of the transcriptional downregulation of its own gene. Mechanistically, the cytokine, while not affecting the HNF1α DNA-binding capacity, impaired its ability to recruit CBP/p300 acetyltransferases on target gene promoters and, consequently, its transactivating function. The loss of HNF1α capacity to bind to CBP/p300 and HNF1α functional inactivation have been found to correlate with a change of its posttranslational modification profile. Collectively, the results obtained in this work unveil a new level of HNF1α functional inactivation by TGFβ and contribute to shed light on the early events triggering EMT in hepatocytes. Moreover, these data suggest that the use of HNF1α as anti-EMT tool in a TGFβ-containing microenvironment may require the design of new therapeutic strategies overcoming the TGFβ-induced HNF1α inactivation.
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http://dx.doi.org/10.3389/fphar.2019.00942DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6728925PMC
August 2019

Microenvironment and tumor cells: two targets for new molecular therapies of hepatocellular carcinoma.

Transl Gastroenterol Hepatol 2018 2;3:24. Epub 2018 May 2.

Department of Cellular Biotechnologies and Hematology, Sapienza University of Rome, Rome, Italy.

Hepatocellular carcinoma (HCC), is one of the most frequent human cancer and is characterized by a high mortality rate. The aggressiveness appears strictly related to the liver pathological background on which cancer develops. Inflammation and the consequent fibro/cirrhosis, derived from chronic injuries of several origins (viral, toxic and metabolic) and observable in almost all oncological patients, represents the most powerful risk factor for HCC and, at the same time, an important obstacle to the efficacy of systemic therapy. Multiple microenvironmental cues, indeed, play a pivotal role in the pathogenesis, evolution and recurrence of HCC as well as in the resistance to standard therapies observed in most of patients. The identification of altered pathways in cancer cells and of microenvironmental changes, strictly connected in pathogenic feedback loop, may permit to plan new therapeutic approaches targeting tumor cells and their permissive microenvironment, simultaneously.
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http://dx.doi.org/10.21037/tgh.2018.04.05DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6002256PMC
May 2018

TGFbeta Induces Binucleation/Polyploidization in Hepatocytes through a Src-Dependent Cytokinesis Failure.

PLoS One 2016 28;11(11):e0167158. Epub 2016 Nov 28.

Istituto Pasteur Italia-Fondazione Cenci Bolognetti, Department of Cellular Biotechnologies and Haematology, Sapienza University of Rome, Rome, Italy.

In all mammals, the adult liver shows binucleated as well as mononucleated polyploid hepatocytes. The hepatic polyploidization starts after birth with an extensive hepatocyte binucleation and generates hepatocytes of several ploidy classes. While the functional significance of hepatocyte polyploidy is becoming clearer, how it is triggered and maintained needs to be clarified. Aim of this study was to identify a major inducer of hepatocyte binucleation/polyploidization and the cellular and molecular mechanisms involved. We found that, among several cytokines analyzed, known to be involved in early liver development and/or mass control, TGFbeta1 was capable to induce, together with the expected morphological changes, binucleation in hepatocytes in culture. Most importantly, the pharmacological inhibition of TGFbeta signaling in healthy mice during weaning, when the physiological binucleation occurs, induced a significant decrease of hepatocyte binucleation rate, without affecting cell proliferation and hepatic index. The TGFbeta-induced hepatocyte binucleation resulted from a cytokinesis failure, as assessed by video microscopy, and is associated with a delocalization of the cytokinesis regulator RhoA-GTPase from the mid-body of dividing cells. The use of specific chemical inhibitors demonstrated that the observed events are Src-dependent. Finally, the restoration of a fully epithelial phenotype by TGFbeta withdrawal gave rise to a cell progeny capable to maintain the polyploid state. In conclusion, we identified TGFbeta as a major inducer of hepatocyte binucleation both in vitro and in vivo, thus ascribing a novel role to this pleiotropic cytokine. The production of binucleated/tetraploid hepatocytes is due to a cytokinesis failure controlled by the molecular axis TGFbeta/Src/RhoA.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0167158PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5125678PMC
August 2017

Modulating the Substrate Stiffness to Manipulate Differentiation of Resident Liver Stem Cells and to Improve the Differentiation State of Hepatocytes.

Stem Cells Int 2016 12;2016:5481493. Epub 2016 Jan 12.

Department of Cellular Biotechnologies and Hematology, Section of Molecular Genetics, Sapienza University of Rome, Viale Regina Elena, 324, 00161 Rome, Italy.

In many cell types, several cellular processes, such as differentiation of stem/precursor cells, maintenance of differentiated phenotype, motility, adhesion, growth, and survival, strictly depend on the stiffness of extracellular matrix that, in vivo, characterizes their correspondent organ and tissue. In the liver, the stromal rigidity is essential to obtain the correct organ physiology whereas any alteration causes liver cell dysfunctions. The rigidity of the substrate is an element no longer negligible for the cultivation of several cell types, so that many data so far obtained, where cells have been cultured on plastic, could be revised. Regarding liver cells, standard culture conditions lead to the dedifferentiation of primary hepatocytes, transdifferentiation of stellate cells into myofibroblasts, and loss of fenestration of sinusoidal endothelium. Furthermore, standard cultivation of liver stem/precursor cells impedes an efficient execution of the epithelial/hepatocyte differentiation program, leading to the expansion of a cell population expressing only partially liver functions and products. Overcoming these limitations is mandatory for any approach of liver tissue engineering. Here we propose cell lines as in vitro models of liver stem cells and hepatocytes and an innovative culture method that takes into account the substrate stiffness to obtain, respectively, a rapid and efficient differentiation process and the maintenance of the fully differentiated phenotype.
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http://dx.doi.org/10.1155/2016/5481493DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4737459PMC
April 2016

Molecular Mechanisms Underlying Peritoneal EMT and Fibrosis.

Stem Cells Int 2016 31;2016:3543678. Epub 2016 Jan 31.

Department of Cellular Biotechnologies and Hematology, Section of Molecular Genetics, Sapienza University of Rome, Viale Regina Elena 324, 00161 Rome, Italy.

Peritoneal dialysis is a form of renal replacement alternative to the hemodialysis. During this treatment, the peritoneal membrane acts as a permeable barrier for exchange of solutes and water. Continual exposure to dialysis solutions, as well as episodes of peritonitis and hemoperitoneum, can cause acute/chronic inflammation and injury to the peritoneal membrane, which undergoes progressive fibrosis, angiogenesis, and vasculopathy, eventually leading to discontinuation of the peritoneal dialysis. Among the different events controlling this pathological process, epithelial to mesenchymal transition of mesothelial cells plays a main role in the induction of fibrosis and in subsequent functional deterioration of the peritoneal membrane. Here, the main extracellular inducers and cellular players are described. Moreover, signaling pathways acting during this process are elucidated, with emphasis on signals delivered by TGF-β family members and by Toll-like/IL-1β receptors. The understanding of molecular mechanisms underlying fibrosis of the peritoneal membrane has both a basic and a translational relevance, since it may be useful for setup of therapies aimed at counteracting the deterioration as well as restoring the homeostasis of the peritoneal membrane.
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http://dx.doi.org/10.1155/2016/3543678DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4752998PMC
March 2016

Epigenetic control of EMT/MET dynamics: HNF4α impacts DNMT3s through miRs-29.

Biochim Biophys Acta 2015 Aug 21;1849(8):919-29. Epub 2015 May 21.

Istituto Pasteur-Fondazione Cenci Bolognetti, Department of Cellular Biotechnologies and Hematology, Section of Molecular Genetics, Sapienza University of Rome, Rome, Italy; National Institute for Infectious Diseases L. Spallanzani, IRCCS, Rome, Italy. Electronic address:

Background And Aims: Epithelial-to-mesenchymal transition (EMT) and the reverse mesenchymal-to-epithelial transition (MET) are manifestations of cellular plasticity that imply a dynamic and profound gene expression reprogramming. While a major epigenetic code controlling the coordinated regulation of a whole transcriptional profile is guaranteed by DNA methylation, DNA methyltransferase (DNMT) activities in EMT/MET dynamics are still largely unexplored. Here, we investigated the molecular mechanisms directly linking HNF4α, the master effector of MET, to the regulation of both de novo of DNMT 3A and 3B.

Methods: Correlation among EMT/MET markers, microRNA29 and DNMT3s expression was evaluated by RT-qPCR, Western blotting and immunocytochemical analysis. Functional roles of microRNAs and DNMT3s were tested by anti-miRs, microRNA precursors and chemical inhibitors. ChIP was utilized for investigating HNF4α DNA binding activity.

Results: HNF4α silencing was sufficient to induce positive modulation of DNMT3B, in in vitro differentiated hepatocytes as well as in vivo hepatocyte-specific Hnf4α knockout mice, and DNMT3A, in vitro, but not DNMT1. In exploring the molecular mechanisms underlying these observations, evidence have been gathered for (i) the inverse correlation between DNMT3 levels and the expression of their regulators miR-29a and miR-29b and (ii) the role of HNF4α as a direct regulator of miR-29a-b transcription. Notably, during TGFβ-induced EMT, DNMT3s' pivotal function has been proved, thus suggesting the need for the repression of these DNMTs in the maintenance of a differentiated phenotype.

Conclusions: HNF4α maintains hepatocyte identity by regulating miR-29a and -29b expression, which in turn control epigenetic modifications by limiting DNMT3A and DNMT3B levels.
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http://dx.doi.org/10.1016/j.bbagrm.2015.05.005DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6319628PMC
August 2015

Epigenetic regulation in hepatocellular carcinoma requires long noncoding RNAs.

Biomed Res Int 2015 10;2015:473942. Epub 2015 Mar 10.

Istituto Pasteur-Fondazione Cenci Bolognetti, Dipartimento di Biotecnologie Cellulari ed Ematologia, Sezione di Genetica Molecolare, Sapienza University of Rome, Viale Regina Elena 324, 00161 Rome, Italy.

Recent evidence has proven the relevance of epigenetic changes in the development of hepatocellular carcinoma (HCC), the major adult liver malignancy. Moreover, HCC onset and progression correlate with the deregulation of several long noncoding RNAs (lncRNAs), exhibiting great biological significance. As discussed in this review, many of these transcripts are able to specifically act as tumor suppressors or oncogenes by means of their role as molecular platforms. Indeed, these lncRNAs are able to bind and recruit epigenetic modifiers on specific genomic loci, ultimately resulting in regulation of the gene expression relevant in cancer development. The evidence presented in this review highlights that lncRNAs-mediated epigenetic regulation should be taken into account for potential targeted therapeutic approaches.
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http://dx.doi.org/10.1155/2015/473942DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4377435PMC
December 2015

Molecular mechanisms controlling the phenotype and the EMT/MET dynamics of hepatocyte.

Liver Int 2015 Feb 20;35(2):302-10. Epub 2014 May 20.

Istituto Pasteur-Fondazione Cenci Bolognetti, Department of Cellular Biotechnologies and Haematology, Sapienza University of Rome, Rome, Italy.

The complex spatial and paracrine relationships between the various liver histotypes are essential for proper functioning of the hepatic parenchymal cells. Only within a correct tissue organization, in fact, they stably maintain their identity and differentiated phenotype. The loss of histotype identity, which invariably occurs in the primary hepatocytes in culture, or in vivo in particular pathological conditions (fibrosis and tumours), is mainly because of the phenomenon of epithelial-to-mesenchymal transition (EMT). The EMT process, that occurs in the many epithelial cells, appears to be driven by a number of general, non-tissue-specific, master transcriptional regulators. The reverse process, the mesenchymal-to-epithelial transition (MET), as yet much less characterized at a molecular level, restores specific epithelial identities, and thus must include tissue-specific master elements. In this review, we will summarize the so far unveiled events of EMT/MET occurring in liver cells. In particular, we will focus on hepatocyte and describe the pivotal role in the control of EMT/MET dynamics exerted by a tissue-specific molecular mini-circuitry. Recent evidence, indeed, highlighted as two transcriptional factors, the master gene of EMT Snail, and the master gene of hepatocyte differentiation HNF4α, exhorting a direct reciprocal repression, act as pivotal elements in determining opposite cellular outcomes. The different balances between these two master regulators, further integrated by specific microRNAs, in fact, were found responsible for the EMT/METs dynamics as well as for the preservation of both hepatocyte and stem/precursor cells identity and differentiation. Overall, these findings impact the maintenance of stem cells and differentiated cells both in in vivo EMT/MET physio-pathological processes as well as in culture.
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http://dx.doi.org/10.1111/liv.12577DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4344819PMC
February 2015

Spike-in SILAC proteomic approach reveals the vitronectin as an early molecular signature of liver fibrosis in hepatitis C infections with hepatic iron overload.

Proteomics 2014 May;14(9):1107-15

Department of Cellular Biotechnologies and Haematology, Istituto Pasteur-Fondazione Cenci Bolognetti, Sapienza University of Rome, Italy; "L. Spallanzani" National Institute for Infectious Diseases, IRCCS, Rome, Italy.

Hepatitis C virus (HCV)-induced iron overload has been shown to promote liver fibrosis, steatosis, and hepatocellular carcinoma. The zonal-restricted histological distribution of pathological iron deposits has hampered the attempt to perform large-scale in vivo molecular investigations on the comorbidity between iron and HCV. Diagnostic and prognostic markers are not yet available to assess iron overload-induced liver fibrogenesis and progression in HCV infections. Here, by means of Spike-in SILAC proteomic approach, we first unveiled a specific membrane protein expression signature of HCV cell cultures in the presence of iron overload. Computational analysis of proteomic dataset highlighted the hepatocytic vitronectin expression as the most promising specific biomarker for iron-associated fibrogenesis in HCV infections. Next, the robustness of our in vitro findings was challenged in human liver biopsies by immunohistochemistry and yielded two major results: (i) hepatocytic vitronectin expression is associated to liver fibrogenesis in HCV-infected patients with iron overload; (ii) hepatic vitronectin expression was found to discriminate also the transition between mild to moderate fibrosis in HCV-infected patients without iron overload.
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http://dx.doi.org/10.1002/pmic.201300422DOI Listing
May 2014

Human haemato-endothelial precursors: cord blood CD34+ cells produce haemogenic endothelium.

PLoS One 2012 4;7(12):e51109. Epub 2012 Dec 4.

Department of Haematology, Oncology and Molecular Medicine, Istituto Superiore di Sanità, Rome, Italy.

Embryologic and genetic evidence suggest a common origin of haematopoietic and endothelial lineages. In the murine embryo, recent studies indicate the presence of haemogenic endothelium and of a common haemato-endothelial precursor, the haemangioblast. Conversely, so far, little evidence supports the presence of haemogenic endothelium and haemangioblasts in later stages of development. Our studies indicate that human cord blood haematopoietic progenitors (CD34+45+144-), triggered by murine hepatocyte conditioned medium, differentiate into adherent proliferating endothelial precursors (CD144+CD105+CD146+CD31+CD45-) capable of functioning as haemogenic endothelium. These cells, proven to give rise to functional vasculature in vivo, if further instructed by haematopoietic growth factors, first switch to transitional CD144+45+ cells and then to haematopoietic cells. These results highlight the plasticity of haemato-endhothelial precursors in human post-natal life. Furthermore, these studies may provide highly enriched populations of human post-fetal haemogenic endothelium, paving the way for innovative projects at a basic and possibly clinical level.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0051109PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3514182PMC
May 2013

Ferritin heavy chain is the host factor responsible for HCV-induced inhibition of apoB-100 production and is required for efficient viral infection.

J Proteome Res 2012 May 10;11(5):2786-97. Epub 2012 Apr 10.

L. Spallanzani National Institute for Infectious Diseases, IRCCS, via Portuense 292, 00149, Rome, Italy.

Hepatic fat export occurs by apolipoprotein B-100-containing lipoprotein production, whereas impaired production leads to liver steatosis. Hepatitis C virus (HCV) infection is associated to dysregulation of apoB-100 secretion and steatosis; however, the molecular mechanism by which HCV affects the apoB-100 secretion is not understood. Here, combining quantitative proteomics and computational biology, we propose ferritin heavy chain (Fth) as being the cellular determinant of apoB-100 production inhibition. By means of molecular analyses, we found that HCV nonstructural proteins and NS5A appear to be sufficient for inducing Fth up-regulation. Fth in turn was found to inhibit apoB-100 secretion leading to increased intracellular degradation via proteasome. Notably, intracellular Fth down-regulation by siRNA restores apoB-100 secretion. The inverse correlation between ferritin and plasma apoB-100 concentrations was also found in JFH-1 HCV cell culture systems (HCVcc) and HCV-infected patients. Finally, Fth expression was found to be required for robust HCV infection. These observations provide a further molecular explanation for the onset of liver steatosis and allow for hypothesizing on new therapeutic and antiviral strategies.
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http://dx.doi.org/10.1021/pr201128sDOI Listing
May 2012

The new murine hepatic 3A cell line responds to stress stimuli by activating an efficient Unfolded Protein Response (UPR).

Toxicol In Vitro 2012 Feb 4;26(1):7-15. Epub 2011 Oct 4.

National Research Institute on Food and Nutrition (INRAN), Rome, Italy.

In the present study we have investigated the properties of a novel cell line (3A cells) obtained from the liver of 14.5 days post coitum (dpc) wild-type mouse embryo. 3A cells morphology was characterized by fluorescent localization of F-actin and β-catenin. The expression of specific genes and proteins essential to liver function in these cells was comparable or even more efficient then in the differentiated hepatocytic cell line MMH-D6. 3A cells also showed the capability to excrete molecules in extracellular spaces resembling functional bile canaliculi, glycogen storage activity and the ability to control retinol-binding protein 4 secretion in response to retinol deprivation. Their response to the exogenous stress stimulus induced by tunicamycin was analysed by PCR Pathway Array containing 84 genes involved in the Unfolded Protein Response (UPR). 3A cells were shown to activate the UPR following a typical stressful event, indicating that this cellular model could be further exploited to investigate hepatic proteins secretion and specific reaction to different injuries.
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http://dx.doi.org/10.1016/j.tiv.2011.09.020DOI Listing
February 2012

The stable repression of mesenchymal program is required for hepatocyte identity: a novel role for hepatocyte nuclear factor 4α.

Hepatology 2011 Jun;53(6):2063-74

Department of Cellular Biotechnologies and Hematology, Pasteur Institute-Cenci Bolognetti Foundation, Sapienza University of Rome, Rome, Italy.

Unlabelled: The concept that cellular terminal differentiation is stably maintained once development is complete has been questioned by numerous observations showing that differentiated epithelium may undergo an epithelial-to-mesenchymal transition (EMT) program. EMT and the reverse process, mesenchymal-to-epithelial transition (MET), are typical events of development, tissue repair, and tumor progression. In this study, we aimed to clarify the molecular mechanisms underlying these phenotypic conversions in hepatocytes. Hepatocyte nuclear factor 4α (HNF4α) was overexpressed in different hepatocyte cell lines and the resulting gene expression profile was determined by real-time quantitative polymerase chain reaction. HNF4α recruitment on promoters of both mesenchymal and EMT regulator genes was determined by way of electrophoretic mobility shift assay and chromatin immunoprecipitation. The effect of HNF4α depletion was assessed in silenced cells and in the context of the whole liver of HNF4 knockout animals. Our results identified key EMT regulators and mesenchymal genes as new targets of HNF4α. HNF4α, in cooperation with its target HNF1α, directly inhibits transcription of the EMT master regulatory genes Snail, Slug, and HMGA2 and of several mesenchymal markers. HNF4α-mediated repression of EMT genes induces MET in hepatomas, and its silencing triggers the mesenchymal program in differentiated hepatocytes both in cell culture and in the whole liver.

Conclusion: The pivotal role of HNF4α in the induction and maintenance of hepatocyte differentiation should also be ascribed to its capacity to continuously repress the mesenchymal program; thus, both HNF4α activator and repressor functions are necessary for the identity of hepatocytes.
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http://dx.doi.org/10.1002/hep.24280DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6624426PMC
June 2011

Hepatitis C virus production requires apolipoprotein A-I and affects its association with nascent low-density lipoproteins.

Gut 2011 Mar 12;60(3):378-86. Epub 2010 Oct 12.

National Institute for Infectious Diseases L Spallanzani IRCCS, Rome, Italy.

Background/aims: The life cycle of hepatitis C virus (HCV) is intimately linked to the lipid metabolism of the host. In particular, HCV exploits the metabolic machinery of the lipoproteins in several steps of its life cycle such as circulation in the bloodstream, cell attachment and entry, assembly and release of viral particles. However, the details of how HCV interacts with and influences the metabolism of the host lipoproteins are not well understood. A study was undertaken to investigate whether HCV directly affects the protein composition of host circulating lipoproteins.

Methods: A proteomic analysis of circulating very low-, low- and high-density lipoproteins (VLDL, LDL and HDL), isolated from either in-treatment naïve HCV-infected patients or healthy donors (HD), was performed using two-dimensional gel electrophoresis and tandem mass spectrometry (MALDI-TOF/TOF). The results obtained were further investigated using in vitro models of HCV infection and replication.

Results: A decreased level of apolipoprotein A-I (apoA-I) was found in the LDL fractions of HCV-infected patients. This result was confirmed by western blot and ELISA analysis. HCV cellular models (JFH1 HCV cell culture system (HCVcc) and HCV subgenomic replicons) showed that the decreased apoA-I/LDL association originates from hepatic biogenesis rather than lipoprotein catabolism occurring in the circulation, and is not due to a downregulation of the apoA-I protein concentration. The sole non-structural viral proteins were sufficient to impair the apoA-I/LDL association. Functional evidence was obtained for involvement of apoA-I in the viral life cycle such as RNA replication and virion production. The specific siRNA-mediated downregulation of apoA-I led to a reduction in both HCV RNA and viral particle levels in culture.

Conclusions: This study shows that HCV induces lipoprotein structural modification and that its replication and production are linked to the host lipoprotein metabolism, suggesting apoA-I as a new possible target for antiviral therapy.
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http://dx.doi.org/10.1136/gut.2010.211292DOI Listing
March 2011

Proteomic analysis reveals a major role for contact inhibition in the terminal differentiation of hepatocytes.

J Hepatol 2010 Feb 25;52(2):234-43. Epub 2009 Nov 25.

Laboratory of Gene Expression, National Institute for Infectious Diseases L. Spallanzani IRCCS, Via Portuense 292, Rome, Italy.

Background & Aims: Hepatocytes are considered an exception of the paradigmatic inverse correlation between cell proliferation and terminal differentiation. In fact, hepatic vital functions are guaranteed by proliferating parenchymal cells during liver regeneration. However, a fine molecular characterization of the relationship between proliferation and differentiation in hepatocytes has been hampered by the lack of reliable in vivo or in vitro models.

Methods: The hepatocyte terminal differentiation program was characterized in the immortalized, untransformed and differentiated hepatocytic cell line MMH, using several techniques. Particularly, two-dimensional difference gel electrophoresis combined to tandem mass spectrometry proteomic approach was used. Cell cycle and cell adhesion properties of MMH have been altered using either myc-overexpression and MEK1/2 inhibition or a constitutive active beta-catenin mutant, respectively.

Results: The hepatocyte terminal differentiation program is stimulated by the exit from the cell cycle induced by cell-cell contact. Comparative proteomic analysis of proliferating versus quiescent hepatocytes validated the importance of contact inhibition, identifying 68 differently expressed gene products, representing 49 unique proteins. Notably, enzymes involved in important liver functions such as detoxification processes, lipid metabolism, iron and vitamin A storage and secretion, anti-inflammatory response and exocytosis were found significantly up-regulated in quiescent hepatocytes. Finally, we found that: (i) cell cycle arrest induced by MEK1/2 inhibition is not sufficient to induce hepatic product expression; (ii) constitutive activation of beta-catenin counteracts the contact inhibition-induced terminal differentiation.

Conclusion: The hepatocyte terminal differentiation program requires a quiescent state maintained by cell-cell contact through the E-cadherin/beta-catenin pathway, rather than the inhibition of proliferation.
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http://dx.doi.org/10.1016/j.jhep.2009.11.013DOI Listing
February 2010

Convergence of Wnt signaling on the HNF4alpha-driven transcription in controlling liver zonation.

Gastroenterology 2009 Aug 18;137(2):660-72. Epub 2009 May 18.

Department of Cellular Biotechnologies and Haematology, Istituto Pasteur-Fondazione Cenci Bolognetti, University Sapienza of Rome, Italy.

Background & Aims: In each hepatocyte, the specific repertoire of gene expression is influenced by its exact location along the portocentrovenular axis of the hepatic lobule and provides a reason for the liver functions compartmentalization defined "metabolic zonation." So far, few molecular players controlling genetic programs of periportal (PP) and perivenular (PV) hepatocytes have been identified; the elucidation of zonation mechanisms remains a challenge for experimental hepatology. Recently, a key role in induction and maintenance of the hepatocyte heterogeneity has been ascribed to Wnt/beta-catenin pathway. We sought to clarify how this wide-ranging stimulus integrates with hepatocyte specificity.

Methods: Reverse transcriptase polymerase chain reaction (RT-PCR) allowed the transcriptional profiling of hepatocytes derived from in vitro differentiation of liver stem cells. The GSK3beta inhibitor 6-bromoindirubin-3'-oxime (BIO) was used for beta-catenin stabilization. Co-immunoprecipitations were used to study biochemical protein interactions while ChIP assays allowed the in vivo inspection of PV and PP genes regulatory regions.

Results: We found that spontaneous differentiation of liver stem cells gives rise to PP hepatocytes that, after Wnt pathway activation, switch into PV hepatocytes. Next, we showed that the Wnt downstream player LEF1 interacts with the liver-enriched transcriptional factor HNF4alpha. Finally, we unveiled that the BIO induced activation of PV genes correlates with LEF1 binding to both its own and HNF4alpha consensus, and the repression of PP genes correlates with HNF4alpha displacement from its own consensus.

Conclusion: Our data show a direct and hitherto unknown convergence of the canonical Wnt signaling on the HNF4alpha-driven transcription providing evidences of a mechanism controlling liver zonated gene expression.
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http://dx.doi.org/10.1053/j.gastro.2009.05.038DOI Listing
August 2009

Elucidation of lipoprotein particles structure by proteomic analysis.

Expert Rev Proteomics 2008 Feb;5(1):91-104

National Institute for Infectious Diseases, L. Spallanzani, IRCCS, Rome, Italy.

Lipoproteins are responsible for lipid packaging and transport through the bloodstream, and for their delivery to target tissues. Their participation in process, such as inflammation and innate immunity has also been suggested recently. Lipoprotein particles have very complex biochemical structures, which result from intricate processes involving coordinated mechanisms of protein and lipid synthesis, intracellular assembling and trafficking, and intra- and extracellular metabolism. Alterations in these mechanisms cause several negative effects on human health. The ability of current proteomic approaches to dissect the dynamic nature of complex particles revealing protein composition and post-translational modifications is shedding further light on lipoprotein structures and functions. This review summarizes lipoprotein classification, biogenesis and metabolism as well as discussing how the results of 20 proteomics-based reports integrate our knowledge on both their biochemical composition and their effects on target cells, thus contributing to reveal the possible functions.
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http://dx.doi.org/10.1586/14789450.5.1.91DOI Listing
February 2008

TGFbeta-induced EMT requires focal adhesion kinase (FAK) signaling.

Exp Cell Res 2008 Jan 18;314(1):143-52. Epub 2007 Sep 18.

Istituto Pasteur-Fondazione Cenci Bolognetti, Dipartimento di Biotecnologie Cellulari ed Ematologia, Università La Sapienza, Rome, Italy.

The epithelial-to-mesenchymal transition (EMT) is a crucial process, occurring both during development and tumor progression, by which an epithelial cell undergoes a conversion to a mesenchymal phenotype, dissociates from initial contacts and migrates to secondary sites. We recently reported that in hepatocytes the multifunctional cytokine TGFbeta induces a full EMT characterized by (i) Snail induction, (ii) E-cadherin delocalization and down-regulation, (iii) down-regulation of the hepatocyte transcriptional factor HNF4alpha and (iv) up-regulation of mesenchymal and invasiveness markers. In particular, we showed that Snail directly causes the transcriptional down-regulation of E-cadherin and HNF4, while it is not sufficient for the up-regulation of mesenchymal and invasiveness EMT markers. In this paper, we show that in hepatocytes TGFbeta induces a Src-dependent activation of the focal adhesion protein FAK. More relevantly, we gathered results indicating that FAK signaling is required for (i) transcriptional up-regulation of mesenchymal and invasiveness markers and (ii) delocalization of membrane-bound E-cadherin. Our results provide the first evidence of FAK functional role in TGFbeta-mediated EMT in hepatocytes.
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http://dx.doi.org/10.1016/j.yexcr.2007.09.005DOI Listing
January 2008

Proteomic analysis of human very low-density lipoprotein by two-dimensional gel electrophoresis and MALDI-TOF/TOF.

Proteomics 2007 Jan;7(1):143-54

National Institute for Infectious Diseases L. Spallanzani, IRCCS, Rome, Italy.

Biochemical studies of lipoproteins have shed light on their composition, highly contributing to the comprehension of their function. Due to the complexity of their structure, however, an in-depth structural analysis, in terms of components and PTMs, may still unravel important players in physiological and pathological processes of lipid metabolism. In this study, we performed a protein map of very low-density lipoprotein (VLDL) using a 2-DE MALDI-TOF/TOF proteomic approach. Several VLDL-associated apolipoproteins were identified, including five isoforms of apoE, three isoforms of apoC-IV, and one isoform each of apoC-III, apoM, apoA-I, and apoA-IV. Notably, we also identified seven isoforms of apoL-I and two isoforms of prenylcysteine lyase as new VLDL-associated proteins. Furthermore, we were able to identify PTM of apoE, which was found to be differently O-glycosylated at Thr212 residue, and PTM of apoL-I which we described, for the first time, to be phosphorylated at Ser296. While the physiological relevance of our finding remains to be assessed, we believe that our results will be useful as reference for future studies of VLDL structure in specific physiopathological conditions.
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http://dx.doi.org/10.1002/pmic.200600339DOI Listing
January 2007

Steatosis and intrahepatic lymphocyte recruitment in hepatitis C virus transgenic mice.

J Gen Virol 2004 Jun;85(Pt 6):1509-1520

Fondazione 'Istituto Pasteur Cenci-Bolognetti', Dipartimento di Biotecnologie Cellulari ed Ematologia, Università La Sapienza, Rome, Italy.

To assess the effects of constitutive hepatitis C virus (HCV) gene expression on liver, transgenic mice carrying the entire HCV open reading frame inserted in the alpha1 antitrypsin (A1AT) gene were generated. Expression of A1AT/HCV mRNA was found to be mainly limited to perivascular areas of the liver as indicated by in situ hybridization analysis. HCV core protein was detected in Western blots of liver extracts, whereas the expression of E2, NS3 and NS5 proteins was revealed by immunostaining of liver samples using HCV-specific antisera. Histological analysis of HCV transgenic mice showed that these animals develop extensive steatosis, but very little necrosis of liver tissue. Moreover, a consistent T cell infiltrate and a slight hepatocyte proliferation were observed. Phenotypic analysis of cells infiltrating the liver indicated that recruitment and/or expansion of residing CD8(+), NK, NKT and gammadelta T cells occurred in transgenic animals. Among these cells, a large fraction of CD8(+) T lymphocytes released mainly IL-10 and, to a lesser extent, IFN-gamma upon mitogenic stimulation in vitro. Furthermore, both intrahepatic lymphocytes and splenocytes did not produce cytokines in response to HCV antigens. Thus, these data indicate that constitutive expression of HCV proteins may be responsible for intrahepatic lymphocyte recruitment in absence of viral antigen recognition. This response is likely to be driven by virus-induced cellular factors and may play a significant role in the immunopathology of chronic HCV infection and liver disease.
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http://dx.doi.org/10.1099/vir.0.19724-0DOI Listing
June 2004

Cell-based assay for the detection of chemically induced cellular stress by immortalized untransformed transgenic hepatocytes.

BMC Biotechnol 2004 Mar 19;4. Epub 2004 Mar 19.

Human Genome Department, Istituto di Tecnologie Biomediche-National Research Council, Segrate, Milano, Italy.

Background: Primary hepatocytes, one of the most widely used cell types for toxicological studies, have a very limited life span and must be freshly derived from mice or even humans. Attempts to use stable cell lines maintaining the enzymatic pattern of liver cells have been so far unsatisfactory. Stress proteins (heat shock proteins, HSPs) have been proposed as general markers of cellular injury and their use for environmental monitoring has been suggested. The aim of this work is to develop a bi-transgenic hepatocyte cell line in order to evaluate the ability of various organic and inorganic chemicals to induce the expression of the HSP70 driven reporter gene. We previously described transgenic mice (Hsp70/hGH) secreting high levels of human Growth Hormone (hGH) following exposure to toxic compounds in vivo and in vitro in primary cultures derived from different organs. In addition, we also reported another transgenic model (AT/cytoMet) allowing the reproducible immortalization of untransformed hepatocytes retaining in vitro complex liver functions.

Results: The transgenic mouse line Hsp70/hGH was crossed with the AT/cytoMet transgenic strain permitting the reproducible immortalization of untransformed hepatocytes. From double transgenic animals we derived several stable hepatic cell lines (MMH-GH) which showed a highly-differentiated phenotype as judged from the retention of epithelial cell polarity and the profile of gene expression, including hepatocyte-enriched transcription factors and detoxifying enzymes. In these cell lines, stresses induced by exposure to inorganic [Sodium Arsenite (NaAsO2) and Cadmium Chloride (CdCl2)], and organic [Benzo(a)Pyrene (BaP), PentaChloroPhenol (PCP), TetraChloroHydroQuinone (TCHQ), 1-Chloro-2,4-DiNitro-Benzene (CDNB)] compounds, specifically induced hGH release in the culture medium.

Conclusions: MMH-GH, an innovative model to evaluate the toxic potential of chemical and physical xenobiotics, provides a simple biological system that may reduce the need for animal experimentation and/or continuously deriving fresh hepatocytes.
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http://dx.doi.org/10.1186/1472-6750-4-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC406386PMC
March 2004

Searching for DNA-protein interactions by lambda phage display.

J Mol Biol 2002 Sep;322(4):697-706

Dipartimento di Biotecnologie Cellulari ed Ematologia, Sezione di Genetica Molecolare, Fondazione Istituto Pasteur-Cenci Bolognetti, Università La Sapienza, 00161, Rome, Italy.

We applied phage display technology to DNA-protein interaction studies. A cDNA expression library displayed on the surface of bacteriophage lambda was generated from the highly differentiated MMH E14 murine hepatic cell line. Selection of this library using the promoter sequence of the liver-enriched transcription factor HNF1alpha gene as ligate identified DNA-binding domains specifically interacting with different regions of this regulatory sequence. One of the selected phage showed 100% identity to a DNA-binding domain shared by differentiation specific element-binding protein, vasoactive intestinal peptide receptor-repressor protein and replication factor C and was further investigated. Specific binding of the selected protein domain was confirmed in a phage-independent context. By combining ELISA and South-Western assays using the selected phage and a bacterially expressed glutathione-S-transferase protein fused to the encoded DNA-binding domain, an array of multiple adjacent DNA-binding sites sharing a common consensus motif was identified. The strategy described represents a powerful tool to identify proteins that bind to DNA regulatory elements.
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http://dx.doi.org/10.1016/s0022-2836(02)00851-3DOI Listing
September 2002

Synergy between truncated c-Met (cyto-Met) and c-Myc in liver oncogenesis: importance of TGF-beta signalling in the control of liver homeostasis and transformation.

Oncogene 2002 Feb;21(9):1335-45

Fondazione Istituto Pasteur-Cenci Bolognetti, Dipartimento di Biotecnologie Cellulari ed Ematologia, Sezione di Genetica Molecolare, Università La Sapienza, 00161, Rome, Italy.

The c-Met tyrosine kinase receptor and its ligand, Hepatocyte Growth Factor/ Scatter Factor, have been implicated in human cancer. We have previously described that the transgenic expression of a truncated form of human c-Met (cyto-Met) in the liver confers resistance to several apoptotic stimuli. Here we show the impact of cyto-Met expression on liver proliferation and transformation. Despite a sixfold increase of hepatocyte proliferation, adult transgenic livers displayed normal size and architecture. We present evidence showing that activation of TGF-beta1 signalling controls the liver mass in cyto-Met mice. The oncogenic potential of cyto-Met was further assessed in the context of c-Myc-induced hepatocarcinogenesis, using WHV/c-Myc transgenic mice. Co-expression of cyto-Met and c-Myc further enhanced hepatocyte proliferation and caused a dramatic acceleration of the Myc-induced tumorigenesis, leading to the emergence of hepatocarcinomas in 3-4-month-old animals. Importantly, the TGF-beta receptor type II expression was strongly downregulated in most tumours, indicating that impairment of TGF-beta1-mediated growth inhibition plays a major role in accelerated neoplastic development. The strong potential of cyto-Met for oncogenic cooperation without direct transforming activity designates cyto-Met mice as an ideal tool for studying the early steps of multistage hepatocarcinogenesis and for identification of prognostic markers of transformation.
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http://dx.doi.org/10.1038/sj.onc.1205199DOI Listing
February 2002