Christine Perret - Academia.edu (original) (raw)

Papers by Christine Perret

Journal of Clinical Investigation, Feb 1, 2012

Hepatocellular carcinoma (HCC) is the third leading cause of cancer-related death worldwide. Its ... more Hepatocellular carcinoma (HCC) is the third leading cause of cancer-related death worldwide. Its pathogenesis is frequently linked to liver inflammation. Gain-of-function mutations in the gene encoding β-catenin are frequent genetic modifications found in human HCCs. Thus, we investigated whether inflammation was a component of β-catenin-induced tumorigenesis using genetically modified mouse models that recapitulated the stages of initiation and progression of this tumoral process. Oncogenic β-catenin signaling was found to induce an inflammatory program in hepatocytes that involved direct transcriptional control by β-catenin and activation of the NF-κB pathway. This led to a specific inflammatory response, the intensity of which determined the degree of tumor aggressiveness. The chemokine-like chemotactic factor leukocyte cell-derived chemotaxin 2 (LECT2) and invariant NKT (iNKT) cells were identified as key interconnected effectors of liver β-catenin-induced inflammation. In genetic deletion models lacking the gene encoding LECT2 or iNKT cells, hepatic β-catenin signaling triggered the formation of highly malignant HCCs with lung metastasis. Thus, our results identify inflammation as a key player in β-catenin-induced liver tumorigenesis. We provide strong evidence that, by activating pro-and antiinflammatory mediators, β-catenin signaling produces an inflammatory microenvironment that has an impact on tumoral development. Our data are consistent with the fact that most β-catenin-activated HCCs are of better prognosis.

Background LKB1 is an evolutionary conserved kinase implicated in a wide range of cellular functi... more Background LKB1 is an evolutionary conserved kinase implicated in a wide range of cellular functions including inhibition of cell proliferation, regulation of cell polarity and metabolism. When Lkb1 is inactivated in the liver, glucose homeostasis is perturbed, cellular polarity is affected and cholestasis develops. Cholestasis occurs as a result from deficient bile duct develop-ment, yet how LKB1 impacts on biliary morphogenesis is unknown. Methodology/Principal Findings We characterized the phenotype of mice in which deletion of the Lkb1 gene has been spe-cifically targeted to the hepatoblasts. Our results confirmed that lack of LKB1 in the liver results in bile duct paucity leading to cholestasis. Immunostaining analysis at a prenatal stage showed that LKB1 is not required for differentiation of hepatoblasts to cholangiocyte precursors but promotes maturation of the primitive ductal structures to mature bile ducts. This phenotype is similar to that obtained upon inactivation of N...

(A) Total RNA was extracted from 96 samples (29 from HCC specimens with WT CTNN... more (A) Total RNA was extracted from 96 samples (29 from HCC specimens with WT CTNNB1, 38 from HCC specimens with mutant CTNNB1 and 29 from adjacent non tumor tissue that included 19 CTNNB1-mutated HCC and 10 non-mutated HCC). Notum mRNA was assayed by quantitative RT-PCR. (B) NOTUM in situ hybridization with mutantβ-catenin HCC specimens showed significantly stronger NOTUM labeling in tumor tissue than normal tissue. Seven HCC biopsies were analyzed and a representative result is shown. (C) Tamoxifen-inducible model of acute β-catenin activation in the liver. (D) Eight week-old mice were intraperitoneally injected with 0.3 mg tamoxifen and total RNA was extracted from WT liver (black rows) and from APCΔex14/Δex14 liver (grey rows) at the indicated times and Notum mRNA was assayed by quantitative RT-PCR. Results are normalized to those for 18S transcripts and the mean ± S.D. of triplicate samples is presented. (E) Genomic environment of the Notum gene (from mRNA-Seq and ChIP-Seq data described in [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0150997#pone.0150997.ref005" target="_blank">5</a>]. Upper blue: mRNA-seq signals. ChIP-Seq signals are shown below with the presence within peaks of WREs depicted first in red; then in black, ChIP-Seq in Apc-ko conditions with an antibody against Tcf4; in red, ChIP-Seq in Apc-ko conditions with an antibody against β-catenin; in green, ChIP-Seq in β-catenin-ko conditions with an antibody against Tcf4. Below in yellow, ENCODE data for DNase 1 HS performed with 8-week-old and in E14.5 embryonic mouse livers (DNaseI Hypersensitivity by Digital DNaseI from ENCODE/University of Washington), of H3K27Ac marks in 8-week-old and in E14.5 embryonic livers (Histone Mods by ChIP-seq from ENCODE/LICR).</p

Medecine sciences : M/S, 2021

Nature Communications, 2021

A Correction to this paper has been published: https://doi.org/10.1038/s41467-021-22104-4

Nature Communications, 2020

Excessive glucose production by the liver is a key factor in the hyperglycemia observed in type 2... more Excessive glucose production by the liver is a key factor in the hyperglycemia observed in type 2 diabetes mellitus (T2DM). Here, we highlight a novel role of liver kinase B1 (Lkb1) in this regulation. We show that mice with a hepatocyte-specific deletion of Lkb1 have higher levels of hepatic amino acid catabolism, driving gluconeogenesis. This effect is observed during both fasting and the postprandial period, identifying Lkb1 as a critical suppressor of postprandial hepatic gluconeogenesis. Hepatic Lkb1 deletion is associated with major changes in whole-body metabolism, leading to a lower lean body mass and, in the longer term, sarcopenia and cachexia, as a consequence of the diversion of amino acids to liver metabolism at the expense of muscle. Using genetic, proteomic and pharmacological approaches, we identify the aminotransferases and specifically Agxt as effectors of the suppressor function of Lkb1 in amino acid-driven gluconeogenesis.

Hepatology Communications, 2021

CTNNB1 (catenin beta 1)-mutated hepatocellular carcinomas (HCCs) account for a large proportion o... more CTNNB1 (catenin beta 1)-mutated hepatocellular carcinomas (HCCs) account for a large proportion of human HCCs. They display high levels of respiratory chain activity. As metabolism and redox balance are closely linked, tumor cells must maintain their redox status during these metabolic alterations. We investigated the redox balance of these HCCs and the feasibility of targeting this balance as an avenue for targeted therapy. We assessed the expression of the nuclear erythroid 2 p45-related factor 2 (NRF2) detoxification pathway in an annotated human HCC data set and reported an enrichment of the NRF2 program in human HCCs with CTNNB1 mutations, largely independent of NFE2L2 (nuclear factor, erythroid 2 like 2) or KEAP1 (Kelch-like ECH-associated protein 1) mutations. We then used mice with hepatocyte-specific oncogenic β-catenin activation to evaluate the redox status associated with β-catenin activation in preneoplastic livers and tumors. We challenged them with various oxidative stressors and observed that the β-catenin pathway activation increased transcription of Nfe2l2, which protects β-catenin-activated hepatocytes from oxidative damage and supports tumor development. Moreover, outside of its effects on reactive oxygen species scavenging, we found out that Nrf2 itself contributes to the metabolic activity of β-catenin-activated cells. We then challenged β-catenin activated tumors pharmacologically to create a redox imbalance and found that pharmacological inactivation of Nrf2 was sufficient to considerably decrease the progression of β-catenin-dependent HCC development. Conclusion: These results demonstrate cooperation between oncogenic β-catenin signaling and the NRF2 pathway in CTNNB1mediated HCC tumorigenesis, and we provide evidence for the relevance of redox balance targeting as a therapeutic strategy in CTNNB1-mutated HCC. (Hepatology Communications 2021;0:1-17). T umorigenesis is a complex process involving multiple modifications promoting proliferation and preventing cell death. The maintenance of neoplastic cell proliferation and growth requires a metabolic rewiring to provide essential macromolecules and energy. (1) Since the first observations that tumor cells displayed higher glucose consumption through a glycolytic pathway, it has been shown that there are numerous metabolic pathways, from enhanced glutaminolysis to increased fatty acid oxidation, that can be altered to favor tumor survival and progression. (2-4) Although altering their metabolic activity, tumor cells also have to maintain a redox status compatible with survival, as metabolism and redox balance are closely linked-mostly through the production

Journal of hepatology, 2018

The Wnt/β-catenin pathway is the most frequently deregulated pathway in hepatocellular carcinoma ... more The Wnt/β-catenin pathway is the most frequently deregulated pathway in hepatocellular carcinoma (HCC). Inactivating mutations of the gene encoding AXIN1, a known negative regulator of the Wnt/β-catenin signaling pathway, are observed in about 10% of HCCs. Whole-genome studies usually place HCC with AXIN1 mutations and CTNNB1 mutations in the group of tumors with Wnt/β-catenin activated program. However, it has been shown that HCCs with activating CTNNB1 mutations form a group of HCCs, with a different histology, prognosis and genomic signature to those with inactivating biallelic AXIN1 mutations. We aimed to elucidate the relationship between CTNNB1 mutations, AXIN1 mutations and the activation level of the Wnt/β-catenin program. We evaluated two independent human HCC datasets for the expression of a 23-β-catenin target genes program. We modeled Axin1 loss of function tumorigenesis in two engineered mouse models and performed gene expression profiling. Based on gene expression, we ...

Journal of Hepatology, 2016

The International Journal of Biochemistry & Cell Biology, 2016

Hepatocellular carcinoma (HCC) is the 3 rd cause of cancer-related death worldwide. Most cases ar... more Hepatocellular carcinoma (HCC) is the 3 rd cause of cancer-related death worldwide. Most cases arise in a background of chronic inflammation, extracellular matrix (ECM) remodeling, severe fibrosis and stem/progenitor cell amplification. Although HCCs are soft cellular tumors, they may contain fibrous nests within the tumor mass. Thus, Highlights  Fibrous nests contain myofibroblast activation and cancer stem/progenitor cell markers.  Cancers carrying fibrous nests express a minimal signature associated with advanced tumor stage and bad clinical outcome.

The Journal of Steroid Biochemistry and Molecular Biology, 1995

Antiestrogens have a large range of tissue- and promoter-specific actions, many of which still re... more Antiestrogens have a large range of tissue- and promoter-specific actions, many of which still remain unclear, particularly in the uterus. Thus, we have analyzed the effects of two antiestrogens, tamoxifen (TAM) and ICI 182 780 (ICI) on the uterine estrogen-responsive gene calbindin-D9k (CaBP9k), in the ovariectomized rat uterus, and in primary cultures of myometrial cells. In the ovariectomized rat uterus, estradiol (E2) or E2 plus TAM induced CaBP9k mRNA to the same levels in 6h. Rats given TAM alone had the same mRNA concentration, but maximal induction was obtained later, 12h after injection. ICI alone did not induce CaBP9k gene expression. Rats given E2 plus ICI had low uterine CaBP9k mRNA levels at 6-12h that became undetectable at 24h. Thus ICI has a full antagonistic effect on E2-induced CaBP9k gene. Estradiol receptor (ER) assays showed that TAM had a partial antagonist effect, while ICI had a full antagonist effect on the ER. We also analyzed the effect of TAM and ICI on CaBP9k gene expression in primary cultures of myometrial cells. The effects were similar to those observed in whole uterus. Thus, TAM has mixed effects, being an agonist for CaBP9k gene induction, and an antagonist for ER. ICI antagonizes the effects of E2 on the CaBP9k gene in myometrial cells and in the intact uterus, but in a way that does not involve a decrease in the cellular content of ER. Instead, it interferes with at least one of the events leading to transcriptional activation.

Oncogene, Jan 7, 2014

The LKB1 tumor suppressor gene encodes a master kinase that coordinates the regulation of energet... more The LKB1 tumor suppressor gene encodes a master kinase that coordinates the regulation of energetic metabolism and cell polarity. We now report the identification of a novel isoform of LKB1 (named ΔN-LKB1) that is generated through alternative transcription and internal initiation of translation of the LKB1 mRNA. The ΔN-LKB1 protein lacks the N-terminal region and a portion of the kinase domain. Although ΔN-LKB1 is catalytically inactive, it potentiates the stimulating effect of LKB1 on the AMP-activated protein kinase (AMPK) metabolic sensor through a direct interaction with the regulatory autoinhibitory domain of AMPK. In contrast, ΔN-LKB1 negatively interferes with the LKB1 polarizing activity. Finally, combining in vitro and in vivo approaches, we showed that ΔN-LKB1 has an intrinsic oncogenic property. ΔN-LKB1 is expressed solely in the lung cancer cell line, NCI-H460. Silencing of ΔN-LKB1 decreased the survival of NCI-H460 cells and inhibited their tumorigenicity when engrafte...

Journal of Hepatology, 2013

Journal of Clinical Investigation, 1996

Uterine leiomyomas are a major health problem for women of reproductive age. The molecular biolog... more Uterine leiomyomas are a major health problem for women of reproductive age. The molecular biology of these tumors is poorly understood partly because of the lack of relevant animal models. We have produced transgenic mice expressing the simian virus 40 T antigen driven by the promoter of the Calbindin-D9K (CaBP9K) gene and either Ϫ 1,000 or Ϫ 117 bp of regulatory sequences so as to establish in vivo, uterine smooth muscle tumor models. Six transgenic mouse lines were obtained. Leiomyomas developed in all of them, with an almost complete penetrance of the phenotype. The smooth muscle tumors arose in different parts of the female reproductive tract. Leiomyomas usually developed in the corpus of the uterus, but one mouse line developed leiomyomas in the horn of the uterus, and another in the vagina. The CaBP9K regulatory sequences directing the expression of the Tag gene possess an estradiol responsive element, and accordingly, development of the tumors was strictly under the control of estrogen. Expression of the Tag gene is not only necessary for the initiation of the tumor but also for its development and maintenance. These transgenic mouse models should be useful for studying the pathobiology of uterine leiomyomas and could be instrumental in designing new therapeutic approaches to this disease. (J. Clin. Invest. 1996. 98:777-784.) Key words: estrogens • Calbindin-D9K • uterine smooth muscle • tumor • SV40 T antigen Methods Construction of hybrid genes. Transgenes were constructed by recombinant technology. The construction of the 9K/ Ϫ 1011-Tag and 9K/ Ϫ 117-Tag constructs were prepared as follows. A fragment (from Ϫ 22 to ϩ 365 bp) containing the promoter region (beginning at the SacI site), the first exon, the first intron, and the beginning of the second exon (before the ATG initiation codon) was cloned by PCR. The resulting SacI-EcoRV fragment was then cloned, together with a fragment PstI-SacI containing 5 Ј regulatory sequences of the rat CaBP9K gene

Journal of Biological Chemistry, 1998

The calbindin-D9K gene encodes a vitamin D-induced calcium-binding protein that is expressed as a... more The calbindin-D9K gene encodes a vitamin D-induced calcium-binding protein that is expressed as a marker of small intestine differentiation. We have shown that 4580 base pairs of its 5 DNA regulatory region can target reporter transgene expression in the intestine and cause this transgene to respond like the endogenous gene to vitamin D active metabolite and that the homeoprotein Cdx2 is bound to the TATA box in the intestine. We now show that the 4580 base pairs construct confers a differentiated pattern of reporter transgene expression in the intestine and that cooperation between the proximal promoter and a distal element located in an opened chromatin structure is responsible for the intestinal expression and vitamin D responsiveness of the transgene. Gel shift and footprinting assays using duodenal nuclear extracts indicate that this distal element contains a Cdx2-binding site. Finally, a mutation in this distal Cdx2-binding site dramatically decreases intestinal expression in transgenic mice. This report, using an in vivo approach, demonstrates the crucial role of Cdx2 for the transcription of an intestinal gene. * This work was supported by the Association de Recherche contre le Cancer and the Ligue Nationale contre le Cancer. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. The nucleotide sequence(s) reported in this paper has been submitted to the GenBank TM /EBI Data Bank with accession number(s) X16635.

Journal of Biological Chemistry, 1996

The rat Calbindin-D9K (CaBP9K) gene is mainly expressed in intestine, uterus, and lung and is reg... more The rat Calbindin-D9K (CaBP9K) gene is mainly expressed in intestine, uterus, and lung and is regulated in a complex tissue-specific manner. To analyze the role of potential regulatory elements, previously defined by DNaseI hypersensivity, we made transgenic mice containing truncated rat CaBP9K fusion gene with simian virus 40 large T antigen and the chloramphenicol acetyltransferase as reporter genes. The transgenes contained CaBP9K promoter fragments with 5 end points at ؊4400, ؊1011, and ؊117 base pairs (bp), whereas the 3 end points was at ؉365 bp. Northern blot analysis of T antigen expression and chloramphenicol acetyltransferase enzyme-linked immunosorbent assay indicated that a positive element, probably the distal intestinespecific DNaseI HS, necessary to target the expression of the transgene in the intestine, is present between ؊4400 and ؊1011 bp. The cephalo-caudal gradient of expression of the transgene along the small intestine was similar to those of the endogenous gene, but an ectopic expression of the transgene was observed in the colon. The ؊1011 transgene was expressed in epithelial alveolar cells of the lung, in renal proximal tubule cells, and in uterine myometrium, as judged from immunocytochemical, histological, and Northern blot analyses. The shortest, ؊117 construct was only expressed in uterine myometrium, and it was under a strict estrogen dependence like the endogenous gene. Finally, responsiveness to vitamin D in the duodenum was observed with the largest, ؊4400 construct. Thus, different tissues utilize distinct cis-acting elements to direct and regulate the expression of the rat CaBP9K gene.

Laboratory Investigation, 2004

Murine models of familial adenomatous polyposis harbor a germinal heterozygous mutation on Apc tu... more Murine models of familial adenomatous polyposis harbor a germinal heterozygous mutation on Apc tumor suppressor gene. They are valuable tools for studying intestinal carcinogenesis, as most human sporadic cancers contain inactivating mutations of APC. However, Apc þ /À mice, such as the well-characterized Apc Min/ þ model, develop cancers principally in the small intestine, while humans develop mainly colorectal cancers. We used a Cre-loxP strategy to achieve a new model of germline Apc invalidation in which exon 14 is deleted. We compared the phenotype of these Apc D14/ þ mice to that of the classical Apc Min/ þ. The main phenotypic difference is the shift of the tumors in the distal colon and rectum, often associated with a rectal prolapse. Thus, the severity of the colorectal phenotype is partly due to the particular mutation D14, but also to environmental parameters, as mice raised in conventional conditions developed more colon cancers than those raised in pathogen-free conditions. All lesions, including early lesions, revealed Apc LOH and loss of Apc gene expression. They accumulated b-catenin, overexpressed the b-catenin target genes cyclin D1 and c-Myc, and the distribution pattern of glutamine synthetase, a b-catenin target gene recently identified in the liver, was mosaic in intestinal adenomas. The Apc D14/ þ model is thus a useful new tool for studies on the molecular mechanisms of colorectal tumorigenesis.

European Journal of Cancer Supplements, 2008