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Adjusting the molecular size, the valency and the pharmacokinetics of drug conjugates are as many leverages to improve their therapeutic window, notably by affecting tumor penetration, renal clearance, and short systemic exposure. In that regard, small tumor-targeting ligands are gaining attention. In this study, we demonstrate the benefits of the small Nanofitin alternative scaffolds (7 kDa) as selective tumor-targeting modules for the generation of drug conjugates, focusing on Nanofitins B10 and D8 directed against the EGFR. Owing to their small size and monovalent format, the two Nanofitins displayed a fast and deep tumor penetration in EGFR-positive A431 xenografts in BALB/c nude mice after intravenous administration, yielding to a targeting of respectively 67.9% ± 14.1 and 98.9% ± 0.7 of the tumor cells as demonstrated by IHC. Conjugation with the monomethyl auristatin E toxin provided homogeneous Nanofitin-drug conjugates, with an overall yield of ≥97%, for in vivo assessment in a curative xenograft model using bioluminescent, EGFR-positive, A431 cells in BALB/c nude mice. Internalization was found critical for efficient release of the toxin. Hence, the intravenous administration of the D8-based construct showed significant antitumor effect in vivo as determined by monitoring tumor volumes and bioluminescence levels over 2 months., SCOPUS: ar.j, info:eu-repo/semantics/published

Concerted alteration of immune and metabolic homeostasis underlies several inflammation-related pathologies, ranging from metabolic syndrome to infectious diseases. Here, we explored the coordination of nucleic acid-dependent inflammatory responses and metabolic homeostasis. We reveal that the STING (stimulator of interferon genes) protein regulates metabolic homeostasis through inhibition of the fatty acid desaturase 2 (FADS2) rate-limiting enzyme in polyunsaturated fatty acid (PUFA) desaturation. STING ablation and agonist-mediated degradation increased FADS2-associated desaturase activity and led to accumulation of PUFA derivatives that drive thermogenesis. STING agonists directly activated FADS2-dependent desaturation, promoting metabolic alterations. PUFAs in turn inhibited STING, thereby regulating antiviral responses and contributing to resolving STING-associated inflammation. Thus, we have unveiled a negative regulatory feedback loop between STING and FADS2 that fine-tunes inflammatory responses. Our results highlight the role of metabolic alterations in human pathologies associated with aberrant STING activation and STING-targeting therapies.

The thyroid gland captures iodide in order to synthesize hormones that act on almost all tissues and are essential for normal growth and metabolism. Low plasma levels of thyroid hormones lead to hypothyroidism, which is one of the most common disorder in humans and is not always satisfactorily treated by lifelong hormone replacement. Therefore, in addition to the lack of in vitro tractable models to study human thyroid development, differentiation and maturation, functional human thyroid organoids could pave the way to explore new therapeutic approaches. Here we report the generation of transplantable thyroid organoids derived from human embryonic stem cells capable of restoring plasma thyroid hormone in athyreotic mice as a proof of concept for future therapeutic development., SCOPUS: ar.j, info:eu-repo/semantics/published

Concerted alteration of immune and metabolic homeostasis underlies several inflammation-related pathologies, ranging from metabolic syndrome to infectious diseases. Here, we explored the coordination of nucleic acid-dependent inflammatory responses and metabolic homeostasis. We reveal that the STING (stimulator of interferon genes) protein regulates metabolic homeostasis through inhibition of the fatty acid desaturase 2 (FADS2) rate-limiting enzyme in polyunsaturated fatty acid (PUFA) desaturation. STING ablation and agonist-mediated degradation increased FADS2-associated desaturase activity and led to accumulation of PUFA derivatives that drive thermogenesis. STING agonists directly activated FADS2-dependent desaturation, promoting metabolic alterations. PUFAs in turn inhibited STING, thereby regulating antiviral responses and contributing to resolving STING-associated inflammation. Thus, we have unveiled a negative regulatory feedback loop between STING and FADS2 that fine-tunes inflammatory responses. Our results highlight the role of metabolic alterations in human pathologies associated with aberrant STING activation and STING-targeting therapies., SCOPUS: ar.j, info:eu-repo/semantics/published

Purpose This preclinical study aims to evaluate the extent to which a change in prostate-specific membrane antigen (PSMA) expression of castration-resistant prostate cancer (CRPC) following standard treatment is reflected in [18F]JK-PSMA-7 PET/CT. Methods Castrated mice supplemented with testosterone implant were xenografted with human LNCaP CRPC. After appropriate tumour growth, androgen deprivation therapy (ADT) was carried out by the removal of the implant followed by a single injection of docetaxel (400 μg/20-g mouse) 2 weeks later. [18F]JK-PSMA-7 PET/CT were performed before ADT, then before and at days 12, 26, 47 and 69 after docetaxel administration. The [18F]JK-PSMA-7 PET data were compared to corresponding unspecific metabolic [18F]FDG PET/CT and ex vivo quantification of PSMA expression estimated by flow cytometry on repeated tumour biopsies. Results ADT alone had no early effect on LNCaP tumours that pursued their progression. Until day 12 post-docetaxel, the [18F]JK- PSMA7 uptake was significantly higher than that of [18F]FDG, indicating the persistence of PSMA expression at those time points. From day 26 onwards when the tumours were rapidly expanding, both [18F]JK-PSMA7 and [18F]FDG uptake continuously decreased although the decrease in [18F]JK-PSMA uptake was markedly faster. The fraction of PSMA-positive cells in tumour biopsies decreased similarly over time to reach a non-specific level after the same time period.Conclusion Applying PSMA-based imaging for therapy monitoring in patients with CRPC should be considered with caution since a reduction in [18F]JK-PSMA-7 PET uptake after successive ADT and chemotherapy may be related to downregulation of PSMA expression in dedifferentiated and rapidly proliferating tumour cells., info:eu-repo/semantics/published

Colorectal cancer (CRC) cells are traditionally considered unresponsive to TGFβ due to mutations in the receptors and/or downstream signaling molecules. TGFβ influences CRC cells only indirectly via stromal cells, such as cancer-associated fibroblasts. However, CRC cell ability to directly respond to TGFβ currently remains unexplored. This represents a missed opportunity for diagnostic and therapeutic interventions. Methods: We examined whether cancer cells from primary CRC and liver metastases respond to TGFβ by inducing TGFβ-induced protein ig-h3 (TGFBI) expression, and the contribution of canonical and non-canonical TGFβ signaling pathways to this effect. We then investigated in vitro and in vivo TGFBI impact on metastasis formation and angiogenesis. Using patient serum samples and an orthotopic mouse model of CRC liver metastases we assessed the diagnostic/tumor targeting value of novel antibodies against TGFBI. Results: Metastatic CRC cells, such as circulating tumor cells, directly respond to TGFβ. These cells were characterized by the absence of TGFβ receptor mutations and the frequent presence of p53 mutations. The pro-tumorigenic program orchestrated by TGFβ in CRC cells was mediated through TGFBI, the expression of which was positively regulated by non-canonical TGFβ signaling cascades. TGFBI inhibition was sufficient to significantly reduce liver metastasis formation in vivo. Moreover, TGFBI pro-tumorigenic function was linked to its ability to stimulate angiogenesis. TGFBI levels were higher in serum samples from untreated patients with CRC than in patients who were receiving chemotherapy. A radiolabeled anti-TGFBI antibody selectively targeted metastatic lesions in vivo, underscoring its diagnostic and therapeutic potential. Conclusions: TGFβ signaling in CRC cells directly contributes to their metastatic potential and stromal cell-independence. Proteins downstream of activated TGFβ, such as TGFBI, represent novel diagnostic and therapeutic targets for, SCOPUS: ar.j, info:eu-repo/semantics/published

Introduction: Cabozantinib is a tyrosine kinase inhibitor (TKI) approved for the treatment of medullary thyroid cancer, renal cell carcinoma and hepatocellular carcinoma, and is currently in clinical trials for the treatment of prostate cancer and others. It exerts its therapeutic effect mainly through inhibition of the tyrosine kinases MET (hepatocyte growth factor receptor) and VEGFR2 (vascular endothelial growth factor receptor 2), in addition to several other kinases involved in cancer. PET imaging with TKIs such as [18F]cabozantinib could potentially aid in cancer diagnosis and guide treatment. This study aims to evaluate the utility of [18F]cabozantinib as a PET imaging probe in PC3 tumor xenografted mice. Methods: [18F]cabozantinib was evaluated in non-tumor and tumor bearing (PC3 xenografted) male mice by ex vivo biodistribution studies and in vivo μPET imaging. Pretreatment studies were performed in the tumor bearing mice with the MET inhibitor PF04217903. Mouse plasma was analyzed with HPLC to quantify radiometabolites. To further evaluate the binding specificity of [18F]cabozantinib, in vitro autoradiography studies on heart and PC3 tumor sections were performed in the presence of authentic cabozantinib or specific MET and VEGFR2 inhibitors. Results: Tissue distribution studies in non-tumor bearing mice revealed slow blood clearance, absence of brain uptake and a high myocardial uptake. In the tumor bearing mice, tumor uptake was low (0.58 ± 0.20% ID/g at 30 min post tracer injection), which was confirmed by μPET imaging. No differences in tissue distribution and kinetics were observed in both biodistributions and μPET studies after pretreatment with the MET inhibitor PF04217903. At 30 min post tracer injection, 60 ± 3% of the recovered radioactivity in plasma in non-tumor bearing mice was present as intact tracer. [18F]cabozantinib binding in vitro to heart and tumor tissues was partly blocked in the presence of selective MET and VEGFR2 inhibitors (up to, SCOPUS: ar.j, info:eu-repo/semantics/published

The function of the thyroid gland is to capture iodide in order to synthesize hormones that act on almost all tissues and are essential for normal growth and metabolism. Low plasma levels of thyroid hormones lead to hypothyroidism, which is one of the most common disorder in humans which is not always satisfactorily treated by lifelong hormone replacement. Therefore, in addition to the lack of in vitro tractable models to study human thyroid development, differentiation and maturation, there is a need for new therapeutic approaches that involve replacement of thyroid tissue responsive to changing demands for thyroid hormone. Here we report the first transplantable thyroid organoids derived from human embryonic stem cells capable of restoring plasma thyroid hormone to athyreotic mice as a proof of concept for future therapeutic development., info:eu-repo/semantics/published

Background: Idiopathic pulmonary fibrosis (IPF) is characterized by a progressive and irreversible respiratory failure. Non-invasive markers of disease activity are essential for prognosis and evaluation of early response to anti-fibrotic treatments. Objectives: The aims of this study were to determine whether fluorodeoxyglucose ([18F]-FDG) lung uptake is reduced after initiation of pirfenidone or nintedanib and to assess its possible use as a prognostic factor. Methods: [18F]-FDG PET/CT was performed in IPF patients and in a murine model of pulmonary fibrosis. PET/CTs were performed at day 8 and day 15 post-instillation of bleomycin in pirfenidone- or vehicule-treated mice. In IPF patients, PET-CT was performed before and 3 months after the initiation of pirfenidone or nintedanib. Results: In bleomycin-treated mice, pirfenidone significantly reduced the [18F]-FDG uptake compared to vehicule-treated mice at day 15 (p < 0.001), whereas no difference was observed at day 8 after bleomycin administration. In IPF patients, [18F]-FDG lung uptake before and after 3 months of treatment by nintedanib (n = 11) or pirfenidone (n = 14) showed no significant difference regardless the antifibrotic treatment. Moreover, no difference was noticed between patients with progressive or non-progressive disease at one year of follow up. Conclusions: Pirfenidone significantly reduces the lung [18F]-FDG uptake during the fibrotic phase in a mouse model of IPF. However, these preclinical data were not confirmed in IPF patients 3 months after the initiation of antifibrotic therapy. [18F]-FDG seems therefore not useful in clinical practice to assess the early response of IPF patients to nintedanib or pirfenidone., SCOPUS: ar.j, info:eu-repo/semantics/published

Cancer research is increasingly dependent of patient-derived xenograft model (PDX). However, a major point of concern regarding the PDX model remains the replacement of the human stroma with murine counterpart. In the present work we aimed at clarifying the significance of the human-to-murine stromal replacement for the fidelity of colorectal cancer (CRC) and liver metastasis (CRC-LM) PDX model. We have conducted a comparative metabolic analysis between 6 patient tumors and corresponding PDX across 4 generations. Metabolic signatures of cancer cells and stroma were measured separately by MALDI-imaging, while metabolite changes in entire tumors were quantified using mass spectrometry approach. Measurement of glucose metabolism was also conducted in vivo using [18F]-fluorodeoxyglucose (FDG) and positron emission tomography (PET). In CRC/CRC-LM PDX model, human stroma was entirely replaced at the second generation. Despite this change, MALDI-imaging demonstrated that the metabolic profiles of both stromal and cancer cells remained stable for at least four generations in comparison to the original patient material. On the tumor level, profiles of 86 water-soluble metabolites as well as 93 lipid mediators underlined the functional stability of the PDX model. In vivo PET measurement of glucose uptake (reflecting tumor glucose metabolism) supported the ex vivo observations. Our data show for the first time that CRC/CRC-LM PDX model maintains the functional stability at the metabolic level despite the early replacement of the human stroma by murine cells. The findings demonstrate that human cancer cells actively educate murine stromal cells during PDX development to adopt the human-like phenotype., SCOPUS: ar.j, info:eu-repo/semantics/published

Tristetraprolin (TTP, encoded by the Zfp36 gene) regulates the mRNA stability of several important cytokines. Due to the critical role of this RNA-binding protein in the control of inflammation, TTP deficiency leads to the spontaneous development of a complex inflammatory syndrome. So far, this phenotype has been largely attributed to dysregulated production of TNF and IL‑23 by myeloid cells, such as macrophages or DCs. Here, we generated mice with conditional deletion of TTP in keratinocytes (Zfp36fl/flK14-Cre mice, referred to herein as Zfp36ΔEP mice). Unlike DC-restricted (CD11c-Cre) or myeloid cell-restricted (LysM-Cre) TTP ablation, these mice developed exacerbated inflammation in the imiquimod-induced psoriasis model. Furthermore, Zfp36ΔEP mice progressively developed a spontaneous pathology with systemic inflammation, psoriatic-like skin lesions, and dactylitis. Finally, we provide evidence that keratinocyte-derived TNF production drives these different pathological features. In summary, these findings expand current views on the initiation of psoriasis and related arthritis by revealing the keratinocyte-intrinsic role of TTP., SCOPUS: ar.j, info:eu-repo/semantics/published

Trastuzumab remains an important drug in the management of human epidermal growth factor receptor 2 (HER2) overexpressing breast cancer (BC). Several studies reported resistance mechanisms to trastuzumab, including impaired HER2-accessibility caused by mucin 4 (MUC4). Previously, we demonstrated an increase of Zirconium- 89-radiolabeled-trastuzumab (89Zr-Trastuzumab) accumulation when MUC4- overexpressing BC-cells were challenged with the mucolytic drug N-Acetylcysteine (NAC). Hereby, using the same approach we investigated whether tumor exposure to NAC would also enhance trastuzumab-efficacy. Dual SKBr3 (HER2+/MUC4-, sensitive to trastuzumab) and JIMT1 (HER2+/ MUC4+, resistant to trastuzumab) HER2-BC-bearing-xenografts were treated with trastuzumab and NAC. Treatment was monitored by molecular imaging evaluating HER2-accessibility/activity (89Zr-Trastuzumab HER2-immunoPET) and glucose metabolism (18F-FDG-PET/CT), as well as tumor volume and the expression of key proteins. In the MUC4-positive JIMT1-tumors, the NAC-trastuzumab combination resulted in improved tumor-growth control compared to trastuzumab alone; with smaller tumor volume/weight, lower 18F-FDG uptake, lower %Ki67 and pAkt-expression. NAC reduced MUC4-expression, but did not affect HER2-expression or the trastuzumabsensitivity of the MUC4-negative SKBr3-tumors. These findings suggest that improving HER2-accessibility by reducing MUC4- masking with the mucolytic drug NAC, results in a higher anti-tumor effect of trastuzumab. This provides a rationale for the potential benefit of this approach to possibly treat a subset of HER2-positive BC overexpressing MUC4., SCOPUS: ar.j, info:eu-repo/semantics/published

Epidermal growth-factor receptor (EGFR) is involved in cell growth and proliferation and is over-expressed in malignant tissues. Although anti-EGFR-based immunotherapy became a standard of care for patients with EGFR-positive tumors, this strategy of addressing cancer tumors by targeting EGFR with monoclonal antibodies is less-developed for patient diagnostic and monitoring. Indeed, antibodies exhibit a slow blood clearance, which is detrimental for positron emission tomography (PET) imaging. New molecular probes are proposed to overcome such limitations for patient monitoring, making use of low-molecular-weight protein scaffolds as alternatives to antibodies, such as Nanofitins with better pharmacokinetic profiles. Anti-EGFR Nanofitin B10 was reformatted by genetic engineering to exhibit a unique cysteine moiety at its C-terminus, which allows the development of a fast and site-specific radiolabeling procedure with 18F-4-fluorobenzamido-N-ethylamino-maleimide (18F-FBEM). The in vivo tumor targeting and imaging profile of the anti-EGFR Cys-B10 Nanofitin was investigated in a double-tumor xenograft model by static small-animal PET at 2 h after tail-vein injection of the radiolabeled Nanofitin 18F-FBEM-Cys-B10. The image showed that the EGFR-positive tumor (A431) is clearly delineated in comparison to the EGFR-negative tumor (H520) with a significant tumor-to-background contrast. 18F-FBEM-Cys-B10 demonstrated a significantly higher retention in A431 tumors than in H520 tumors at 2.5 h post-injection with a A431-to-H520 uptake ratio of 2.53 ± 0.18 and a tumor-to-blood ratio of 4.55 ± 0.63. This study provides the first report of Nanofitin scaffold used as a targeted PET radiotracer for in vivo imaging of EGFR-positive tumor, with the anti-EGFR B10 Nanofitin used as proof-of-concept. The fast generation of specific Nanofitins via a fully in vitro selection process, together with the excellent imaging features of the Nanofitin scaffold, could facilitate the development o, SCOPUS: ar.j, info:eu-repo/semantics/published

Myoferlin is a multiple C2-domain-containing protein that regulates membrane repair, tyrosine kinase receptor function and endocytosis in myoblasts and endothelial cells. Recently it has been reported as overexpressed in several cancers and shown to contribute to proliferation, migration and invasion of cancer cells. We have previously demonstrated that myoferlin regulates epidermal growth factor receptor activity in breast cancer. In the current study, we report a consistent overexpression of myoferlin in triple-negative breast cancer cells (TNBC) over cells originating from other breast cancer subtypes. Using a combination of proteomics, metabolomics and electron microscopy, we demonstrate that myoferlin depletion results in marked alteration of endosomal system and metabolism. Mechanistically, myoferlin depletion caused impaired vesicle traffic that led to a misbalance of saturated/unsaturated fatty acids. This provoked mitochondrial dysfunction in TNBC cells. As a consequence of the major metabolic stress, TNBC cells rapidly triggered AMP activated protein kinase-mediated metabolic reprogramming to glycolysis. This reduced their ability to balance between oxidative phosphorylation and glycolysis, rendering TNBC cells metabolically inflexible, and more sensitive to metabolic drug targeting in vitro. In line with this, our in vivo findings demonstrated a significantly reduced capacity of myoferlin-deficient TNBC cells to metastasise to lungs. The significance of this observation was further supported by clinical data, showing that TNBC patients whose tumors overexpress myoferlin have worst distant metastasis-free and overall survivals. This novel insight into myoferlin function establishes an important link between vesicle traffic, cancer metabolism and progression, offering new diagnostic and therapeutic concepts to develop treatments for TNBC patients.Oncogene advance online publication, 24 October 2016; doi:10.1038/onc.2016.369., SCOPUS: ar.j, info:eu-repo/semantics/published

Small nucleolar RNAs (snoRNAs) are emerging as a novel class of proto-oncogenes and tumor suppressors; their involvement in tumorigenesis remains unclear. The box C/D snoRNAs U3 and U8 are upregulated in breast cancers. Here we characterize the function of human U3 and U8 in ribosome biogenesis, nucleolar structure, and tumorigenesis. We show in breast (MCF-7) and lung (H1944) cancer cells that U3 and U8 are required for pre-rRNA processing reactions leading, respectively, to synthesis of the small and large ribosomal subunits. U3 or U8 depletion triggers a remarkably potent p53-dependent anti-tumor stress response involving the ribosomal proteins uL5 (RPL11) and uL18 (RPL5). Interestingly, the nucleolar structure is more sensitive to perturbations in lung cancer than in breast cancer cells. We reveal in a mouse xenograft model that the tumorigenic potential of cancer cells is reduced in the case of U3 suppression and totally abolished upon U8 depletion. Tumors derived from U3- knockdown cells displayed markedly lower metabolic volume and activity than tumors derived from aggressive control cancer cells. Unexpectedly, metabolic tracer uptake by U3-suppressed tumors appeared more heterogeneous, indicating distinctive tumor growth properties that may reflect non-conventional regulatory functions of U3 (or fragments derived from it) in mRNA metabolism., SCOPUS: ar.j, info:eu-repo/semantics/published

Idiopathic pulmonary fibrosis is characterized by a progressive and irreversible respiratory failure. Validated noninvasive methods able to assess disease activity are essential for prognostic purposes as well as for the evaluation of emerging antifibrotic treatments.

Binding of trastuzumab to HER2 receptors can be impaired by steric hindrance caused by mucin MUC4. As mucolytic drugs can breakdown disulfide bonds of mucoproteins, we checked if this approach could positively affect zirconium-89-labeled trastuzumab ([(89)Zr]T) binding/uptake., SCOPUS: ar.j, info:eu-repo/semantics/published

Idiopathic pulmonary fibrosis is characterized by a progressive and irreversible respiratory failure. Validated noninvasive methods able to assess disease activity are essential for prognostic purposes as well as for the evaluation of emerging antifibrotic treatments., SCOPUS: ar.j, info:eu-repo/semantics/published

We used [(18)F]-4-fluorobenzamido-N-ethylamino-maleimide ([(18)F]-FBEM) to radiolabel cells ex vivo for in vivo positron emission tomography (PET) in order to assess cell trafficking in mice. In contrast to commonly used imaging agents, [(18)F]-FBEM forms a covalent bond with thiol groups present on the cells surface. The stability of the probe in aqueous medium was tested at different pH values and cross-experiment showed that thiol-labeling efficiency was retained (at least) up to pH 9. The labeling procedure did not affect significantly the cell viability. To illustrate the procedure, PET images of living mice injected intravenously with labeled T lymphocytes were obtained. They showed the expected cell homing in the spleen that was absent in mice injected with free label., Journal Article, Research Support, Non-U.S. Gov't, info:eu-repo/semantics/published

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The Mdm2 and Mdm4 oncoproteins are key negative regulators of the p53 tumor suppressor. However, their physiological contributions to the regulation of p53 stability and activity remain highly controversial. Here, we combined a p53 knock-in allele, in which p53 is silenced by a transcriptional stop element flanked by loxP sites, with the mdm2- and mdm4-null alleles. This approach allows Cre-mediated conditional p53 expression in tissues in vivo and cells in vitro lacking Mdm2, Mdm4, or both. Using this strategy, we show that Mdm2 and Mdm4 are essential in a nonredundant manner for preventing p53 activity in the same cell type, irrespective of the proliferation/differentiation status of the cells. Although Mdm2 prevents accumulation of the p53 protein, Mdm4 contributes to the overall inhibition of p53 activity independent of Mdm2. We propose a model in which Mdm2 is critical for the regulation of p53 levels and Mdm4 is critical for the fine-tuning of p53 transcriptional activity, both proteins acting synergistically to keep p53 in check., Journal Article, Research Support, Non-U.S. Gov't, SCOPUS: ar.j, info:eu-repo/semantics/published

The Mdm2 and Mdm4 oncoproteins are key negative regulators of the p53 tumor suppressor. However, their physiological contributions to the regulation of p53 stability and activity remain highly controversial. Here, we combined a p53 knock-in allele, in which p53 is silenced by a transcriptional stop element flanked by loxP sites, with the mdm2- and mdm4-null alleles. This approach allows Cre-mediated conditional p53 expression in tissues in vivo and cells in vitro lacking Mdm2, Mdm4, or both. Using this strategy, we show that Mdm2 and Mdm4 are essential in a nonredundant manner for preventing p53 activity in the same cell type, irrespective of the proliferation/differentiation status of the cells. Although Mdm2 prevents accumulation of the p53 protein, Mdm4 contributes to the overall inhibition of p53 activity independent of Mdm2. We propose a model in which Mdm2 is critical for the regulation of p53 levels and Mdm4 is critical for the fine-tuning of p53 transcriptional activity, both proteins acting synergistically to keep p53 in check., Journal Article, Research Support, Non-U.S. Gov't, SCOPUS: ar.j, info:eu-repo/semantics/published

Le suppresseur de tumeur p53 permet à la cellule de se défendre contre différentes formes de stress. Il joue un rôle de barrière s'opposant à la tumorigenèse: en effet la perte de p53 chez la souris prédispose grandement ces animaux à développer des tumeurs; de même le locus p53 est inactivé dans près de 50% des tumeurs humaines.p53 constitue un facteur de transcription qui se lie à des séquences particulières de l'ADN et active l'expression des gènes adjacents. L'expression orchestrée de ces gènes conduit, directement ou indirectement et suivant le contexte cellulaire, soit à la mort de la cellule soit à l'inhibition de la division cellulaire.Les mécanismes moléculaires médiant ces deux activités biologiques essentielles de p53, de même que les mécanismes influençant le choix de la réponse cellulaire, sont encore mal compris. L'importance de p53 dans ce choix reste également à démontrer.Afin de contribuer à la compréhension de ces mécanismes, le modèle murin déficient pour Mdm4, un régulateur négatif de l'activité de p53, a été choisi. L'inactivation de Mdm4 chez la souris conduit en effet à l'activation ectopique de p53 in vivo et l'induction de deux types de réponse: apoptose dans le neuroépithélium et arrêt de la prolifération cellulaire dans les tissus non neuronaux. Le profil d'expression des gènes dans les tissus neuronaux et non neuronaux a donc été comparé entre embryons de souris sauvage et mdm4-/- par la technique d'hybridation de biopuces à ADN. Les résultats obtenus suggèrent que le type de réponse dépend du type cellulaire et non de p53 lui-même. En effet les profils d'expression des gènes dans les tissus neuronaux (conditions d'apoptose) et non neuronaux (conditions d'arrêt de la prolifération cellulaire) chez l'embryon de souris mdm4-/- sont comparables.Nous nous sommes ensuite particulièrement intéressés à deux nouveaux gènes dont l'expression est augmentée dans les embryons mdm4-/-. Dans un premier temps, leur induction transcription, Doctorat en sciences, Spécialisation biologie moléculaire, info:eu-repo/semantics/nonPublished

The p53 tumour suppressor functions as a transcriptional activator, and several p53-inducible genes that play a critical proapoptotic role have been described. Moreover, p53 regulates the expression of various proteins participating in autoregulatory feedback loops, including proteins that negatively control p53 stability (Mdm2 and Pirh2) or modulate stress-induced phosphorylation of p53 on Ser-46 (p53DINP1 or Wip1), a key event for p53-induced apoptosis. Here, we describe a new systematic analysis of p53 targets using oligonucleotide chips, and report the identification of dapk1 as a novel p53 target. We demonstrate that dapk1 mRNA levels increase in a p53-dependent manner in various cellular settings. Both human and mouse dapk1 genomic loci contain DNA sequences that bind p53 in vitro and in vivo. Since dapk1 encodes a serine/threonine kinase previously shown to suppress oncogene-induced transformation by activating a p19ARF/p53-dependent apoptotic checkpoint, our results suggest that Dapk1 participates in a new positive feedback loop controlling p53 activation and apoptosis., Journal Article, Research Support, Non-U.S. Gov't, SCOPUS: ar.j, info:eu-repo/semantics/published

In response to DNA damage, p53 activates a G1 cell cycle checkpoint, in part through induction of the cyclin-dependent kinase inhibitor p21(Waf1/Cip1). Here we report the identification of a new direct p53 target, Ptprv (or ESP), encoding a transmembrane tyrosine phosphatase. Ptprv transcription is dramatically and preferentially increased in cultured cells undergoing p53-dependent cell cycle arrest, but not in cells undergoing p53-mediated apoptosis. This observation was further confirmed in vivo using a Ptprv null-reporter mouse line. A p53-responsive element is present in the Ptprv promoter and p53 is recruited to this site in vivo. Importantly, while p53-dependent apoptosis is intact in mice lacking Ptprv, Ptprv-null fibroblasts and epithelial cells of the small intestine are defective in G1 checkpoint control. Thus, Ptprv is a new direct p53 target and a key mediator of p53-induced cell cycle arrest. Finally, Ptprv loss enhances the formation of epidermal papillomas after exposure to chemical carcinogens, suggesting that Ptprv acts to suppress tumor formation in vivo., Journal Article, Research Support, Non-U.S. Gov't, SCOPUS: ar.j, FLWIN, info:eu-repo/semantics/published

The p53 tumor suppressor functions as a sequence-specific DNA-binding transcription factor that promotes antiproliferative responses, including cell cycle checkpoints, cellular senescence and apoptosis. The precise nature of the p53 transcriptional programs and the complex mechanisms that govern whether or not a cell dies in response to p53 activation remain elusive. We have recently reported the identification of a new direct p53 target, Ptprv, encoding a transmembrane tyrosine phosphatase. Ptprv expression is dramatically and preferentially increased in cells undergoing p53-dependent cell cycle exit, but not in cells undergoing p53-mediated apoptosis. Importantly, while p53-induced apoptosis is intact in mice lacking Ptprv, Ptprv-null cells are defective in G1 checkpoint control. In addition, we report herein that Ptprv is induced at high cell density and mediates contact inhibition of cell growth. Together, the data suggest that Ptprv is a potent inhibitor of cell proliferation and a critical mediator of p53-induced cell cycle exit., Journal Article, info:eu-repo/semantics/published

The p53 tumor suppressor functions as a sequence-specific DNA-binding transcription factor that promotes antiproliferative responses, including cell cycle checkpoints, cellular senescence and apoptosis. The precise nature of the p53 transcriptional programs and the complex mechanisms that govern whether or not a cell dies in response to p53 activation remain elusive. We have recently reported the identification of a new direct p53 target, Ptprv, encoding a transmembrane tyrosine phosphatase. Ptprv expression is dramatically and preferentially increased in cells undergoing p53-dependent cell cycle exit, but not in cells undergoing p53-mediated apoptosis. Importantly, while p53-induced apoptosis is intact in mice lacking Ptprv, Ptprv-null cells are defective in G1 checkpoint control. In addition, we report herein that Ptprv is induced at high cell density and mediates contact inhibition of cell growth. Together, the data suggest that Ptprv is a potent inhibitor of cell proliferation and a critical mediator of p53-induced cell cycle exit., Journal Article, info:eu-repo/semantics/published

Le suppresseur de tumeur p53 permet à la cellule de se défendre contre différentes formes de stress. Il joue un rôle de barrière s'opposant à la tumorigenèse: en effet la perte de p53 chez la souris prédispose grandement ces animaux à développer des tumeurs; de même le locus p53 est inactivé dans près de 50% des tumeurs humaines.p53 constitue un facteur de transcription qui se lie à des séquences particulières de l'ADN et active l'expression des gènes adjacents. L'expression orchestrée de ces gènes conduit, directement ou indirectement et suivant le contexte cellulaire, soit à la mort de la cellule soit à l'inhibition de la division cellulaire.Les mécanismes moléculaires médiant ces deux activités biologiques essentielles de p53, de même que les mécanismes influençant le choix de la réponse cellulaire, sont encore mal compris. L'importance de p53 dans ce choix reste également à démontrer.Afin de contribuer à la compréhension de ces mécanismes, le modèle murin déficient pour Mdm4, un régulateur négatif de l'activité de p53, a été choisi. L'inactivation de Mdm4 chez la souris conduit en effet à l'activation ectopique de p53 in vivo et l'induction de deux types de réponse: apoptose dans le neuroépithélium et arrêt de la prolifération cellulaire dans les tissus non neuronaux. Le profil d'expression des gènes dans les tissus neuronaux et non neuronaux a donc été comparé entre embryons de souris sauvage et mdm4-/- par la technique d'hybridation de biopuces à ADN. Les résultats obtenus suggèrent que le type de réponse dépend du type cellulaire et non de p53 lui-même. En effet les profils d'expression des gènes dans les tissus neuronaux (conditions d'apoptose) et non neuronaux (conditions d'arrêt de la prolifération cellulaire) chez l'embryon de souris mdm4-/- sont comparables.Nous nous sommes ensuite particulièrement intéressés à deux nouveaux gènes dont l'expression est augmentée dans les embryons mdm4-/-. Dans un premier temps, leur induction transcription, Doctorat en sciences, Spécialisation biologie moléculaire, info:eu-repo/semantics/nonPublished

The p53 tumour suppressor functions as a transcriptional activator, and several p53-inducible genes that play a critical proapoptotic role have been described. Moreover, p53 regulates the expression of various proteins participating in autoregulatory feedback loops, including proteins that negatively control p53 stability (Mdm2 and Pirh2) or modulate stress-induced phosphorylation of p53 on Ser-46 (p53DINP1 or Wip1), a key event for p53-induced apoptosis. Here, we describe a new systematic analysis of p53 targets using oligonucleotide chips, and report the identification of dapk1 as a novel p53 target. We demonstrate that dapk1 mRNA levels increase in a p53-dependent manner in various cellular settings. Both human and mouse dapk1 genomic loci contain DNA sequences that bind p53 in vitro and in vivo. Since dapk1 encodes a serine/threonine kinase previously shown to suppress oncogene-induced transformation by activating a p19ARF/p53-dependent apoptotic checkpoint, our results suggest that Dapk1 participates in a new positive feedback loop controlling p53 activation and apoptosis., Journal Article, Research Support, Non-U.S. Gov't, SCOPUS: ar.j, info:eu-repo/semantics/published

In response to DNA damage, p53 activates a G1 cell cycle checkpoint, in part through induction of the cyclin-dependent kinase inhibitor p21(Waf1/Cip1). Here we report the identification of a new direct p53 target, Ptprv (or ESP), encoding a transmembrane tyrosine phosphatase. Ptprv transcription is dramatically and preferentially increased in cultured cells undergoing p53-dependent cell cycle arrest, but not in cells undergoing p53-mediated apoptosis. This observation was further confirmed in vivo using a Ptprv null-reporter mouse line. A p53-responsive element is present in the Ptprv promoter and p53 is recruited to this site in vivo. Importantly, while p53-dependent apoptosis is intact in mice lacking Ptprv, Ptprv-null fibroblasts and epithelial cells of the small intestine are defective in G1 checkpoint control. Thus, Ptprv is a new direct p53 target and a key mediator of p53-induced cell cycle arrest. Finally, Ptprv loss enhances the formation of epidermal papillomas after exposure to chemical carcinogens, suggesting that Ptprv acts to suppress tumor formation in vivo., Journal Article, Research Support, Non-U.S. Gov't, SCOPUS: ar.j, FLWIN, info:eu-repo/semantics/published

info:eu-repo/semantics/nonPublished

info:eu-repo/semantics/nonPublished