Phase I trial of DNA-hsp65 immunotherapy for advanced squamous cell carcinoma of the head and neck

Considering that mycobacterial heat-shock protein 65 (hsp65) gene transfer can elicit a profound antitumoral effect, this study aimed to establish the safety, maximum-tolerated dose (MTD) and preliminary efficacy of DNA-hsp65 immunotherapy in patients with advanced head and neck squamous cell carcinoma (HNSCC). For this purpose, 21 patients with unresectable and recurrent HNSCC were studied. Each patient received three ultrasound-guided injections at 21-day intervals of: 150, 600 or 400 mu g of DNA-hsp65. Toxicity was graded according to CTCAE directions. Tumor volume was measured before and after treatment using computed tomography scan. The evaluation included tumor mass variation, delayed-type hypersensitivity response and spontaneous peripheral blood mononuclear cell proliferation before and after treatment. The MTD was 400 mg per dose. DNA-hsp65 immunotherapy was well tolerated with moderate pain, edema and infections as the most frequent adverse effects. None of the patients showed clinical or laboratory alterations compatible with autoimmune reactions. Partial response was observed in 4 out of 14 patients who completed treatment, 2 of which are still alive more than 3 years after the completion of the trial. Therefore, DNA-hsp65 immunotherapy is a feasible and safe approach at the dose of 400 mg per injection in patients with HNSCC refractory to standard treatment. Further studies in a larger number of patients are needed to confirm the efficacy of this novel strategy.

IL-4 regulates susceptibility to intestinal inflammation in murine food allergy

Cardoso CR, Provinciatto PR, Godoi DF, Ferreira BR, Teixeira G, Rossi MA, Cunha FQ, Silva JS. IL-4 regulates susceptibility to intestinal inflammation in murine food allergy. Am J Physiol Gastrointest Liver Physiol 296: G593-G600, 2009. First published January 8, 2009; doi:10.1152/ajpgi.90431.2008.-Allergies involve a state of immediate hypersensitivity to antigens, including food proteins. The mechanism underlying the initiation and development of allergic responses involves IL-4 that directly induces the differentiation of committed effector Th2 lymphocytes. Although it is clear that Th2 responses play a pivotal role in the development of allergic responses, it remains unclear which mechanisms are involved in the development of the intestinal damages observed in food allergy. Accordingly, this work aimed to study the role of Th2/IL-4-dependent responses in the development of food allergy and intestinal pathology. C57BL/6 wild-type (WT) and IL-4(-/-) mice were sensitized with peanut proteins, challenged with peanut seeds, and followed for the development of food allergy and intestinal inflammation. Results demonstrated that exposure to peanut seeds led to weight loss in WT but not in IL-4(-/-) mice that preserved gut integrity with no signs of mucosal inflammation. These animals presented increased levels of IgG2a in sera, suggesting a role for allergic antibodies in the pathogenesis of WT animals. Most importantly, results also showed that lack of IL-4 modulated gut mucosal response in food allergy through diminished expression of TNF-alpha mRNA, increased Th1 IFN-gamma, IL-12p40, regulatory cytokines, and Foxp3, demonstrating their relevance in the control of allergic inflammatory processes, especially in the intestine. Finally, this study highlighted some of the complex mechanisms involved in the pathogenesis of allergic responses to food antigens in the gut, thereby providing valuable tools for directing novel therapeutic or preventive strategies to the control of allergic enteropathy.

Modulation of mucosal immunity in a murine model of food-induced intestinal inflammation

Background Hypersensitivity or uncontrolled responses against dietary antigens can lead to inflammatory disorders like food allergy and current models reflect a variety of causes but do not reveal the detailed modulation of gut immunity in response to food antigens after breakdown in mucosal tolerance. Objective To develop and characterize a murine model for food-induced intestinal inflammation and to demonstrate the modulation of gut immune response by dietary allergenic antigens. Methods C57BL/6 mice were sensitized with peanut proteins, challenged with peanut seeds and their sera and gut segments were collected for subsequent analyses. Results Sensitization and challenged with peanut seeds led to alterations in gut architecture with inflammatory response characterized by oedema in lamina propria and cell infiltrate composed mainly by eosinophils, mast cells, phagocytes, natural killer and plasma cells, together with low percentage of gamma delta(+) and CD4(+)CD25(+)Foxp3(+) cells in Peyer`s patches. These animals also presented high levels of specific IgE and IgG1 in sera and modulation of mucosal immunity was mediated by increased expression of GATA-3, IL-4, IL-13 and TNF-alpha in contrast to low IFN-gamma in the gut. Conclusion A murine model for food-induced intestinal inflammation was characterized in which modulation of gut immunity occurs by peanut antigens in consequence of T-helper type 2 (Th2) allergic response and failure of regulatory mechanisms necessary for mucosa homeostasis, resembling food allergy. This work shed some light on the understanding of the pathogenesis of gastrointestinal disorders and intolerance in the gut and supports the development of therapies for food-related enteropathies like food allergy, focusing on gut-specific immune response.

Synergistic Effect of Porcine Follicular Fluid and Dibutyryl Cyclic Adenosine Monophosphate on Development of Parthenogenetically Activated Oocytes from Pre-Pubertal Gilts

This study investigated the effect of porcine follicular fluid (PFF) and dibutyryl cyclic adenosine monophosphate (dbcAMP) during in vitro maturation (IVM) of porcine oocytes on meiotic maturation, fertilization and embryo development, and compared the effect of supplementing the embryo culture media with PFF or foetal bovine serum (FBS) on embryo development. Oocytes from pre-pubertal gilts were IVM for 44 h, and parthenogenetically activated or in vitro-fertilized. Embryos were cultured in porcine zygote medium (PZM3) for 7 days. Cleavage and blastocyst rates were evaluated at 48 h and 7 days of culture. The supplementation of the IVM medium with 25% PFF and 1 mm dbcAMP for the first 22 h resulted in more (p < 0.05) embryos developing to the blastocyst stage as compared with the inclusion of dbcAMP alone. The dbcAMP + PFF combination increased (p < 0.05) the average number of nuclei per blastocyst as compared with either of these components alone or in its absence. A synergistic effect of dbcAMP + PFF during IVM was also reflected in the capacity of oocytes to regulate sperm penetration and prevent polyspermy, as twice as many oocytes from the control group were penetrated by more than one sperm as compared with those matured in the presence of both dbcAMP and PFF. The supplementation of PZM3 with 10% FBS from days 5 to 7 of culture significantly improved the total cell quantity in embryos derived either from control or dbcAMP + PFF matured oocytes. There was no effect on the total cell quantity when FBS was replaced by the same concentration of PFF. These studies showed that dbcAMP, PFF and FBS can improve both the quantity (57.3% vs 41.5%) and quality (74.8 vs 33.3 nuclei) of porcine blastocysts derived from oocytes recovered of pre-pubertal gilts.

Charting the course of ovarian development in vertebrates

The decision of the embryonic gonad to differentiate as either a testis or an ovary is a critical step in vertebrate development. The molecular basis of this decision has been the focus of much study, particularly over the past decade. Here we contrast the knowledge of early gonadal development and the switch to testis differentiation with the lack of molecular understanding of ovarian development at early stages. We review current knowledge regarding mechanisms of ovarian morphogenesis and propose a model for the hierarchical control of development of the fetal ovary, incorporating the few genes already known to be important and several signals or factors that are hypothesised to exist in the early ovary.

A low-cost method to test cytotoxic effects of Crotalus vegrandis (Serpentes: Viperidae) venom on kidney cell cultures

The pathogenesis of the renal lesion upon envenomation by snakebite has been related to myolysis, hemolysis, hypotension and/or direct venom nephrotoxicity caused by the venom. Both primary and continuous cell culture systems provide an in vitro alternative for quantitative evaluation of the toxicity of snake venoms. Crude Crotalus vegrandis venom was fractionated by molecular exclusion chromatography. The toxicity of C. vegrandis crude venom, hemorrhagic, and neurotoxic fractions were evaluated on mouse primary renal cells and a continuous cell line of Vero cells maintained in vitro. Cells were isolated from murine renal cortex and were grown in 96 well plates with Dulbecco's Modified Essential Medium (DMEM) and challenged with crude and venom fractions. The murine renal cortex cells exhibited epithelial morphology and the majority showed smooth muscle actin determined by immune-staining. The cytotoxicity was evaluated by the tetrazolium colorimetric method. Cell viability was less for crude venom, followed by the hemorrhagic and neurotoxic fractions with a CT50 of 4.93, 18.41 and 50.22 µg/mL, respectively. The Vero cell cultures seemed to be more sensitive with a CT50 of 2.9 and 1.4 µg/mL for crude venom and the hemorrhagic peak, respectively. The results of this study show the potential of using cell culture system to evaluate venom toxicity.

Analysis of the intranuclear life of nonsense transcripts

Dissertação para obtenção do Grau de Doutor em Biologia, Especialidade de Biologia Molecular

NF-kB pathway controls mitochondrial dynamics

The Optic atrophy 1 protein (OPA1) is a key element in the dynamics and morphology of mitochondria. We demonstrated that the absence of I?B kinase-a, which is a key element of the nonclassical NF-?B pathway, has an impact on the mitochondrial network morphology and OPA1 expression. In contrast, the absence of NF-?B essential modulator (NEMO) or I?B kinase-ß, both of which are essential for the canonical NF-?B pathway, has no impact on mitochondrial dynamics. Whereas Parkin has been reported to positively regulate the expression of OPA1 through NEMO, herein we found that PARK2 overexpression did not modify the expression of OPA1. PARK2 expression reduced the levels of Bax, and it prevented stress-induced cell death only in Bak-deficient mouse embryonic fibroblast cells. Collectively, our results point out a role of the nonclassical NF-?B pathway in the regulation of mitochondrial dynamics and OPA1 expression.

Characterisation of heteromers and oligomers in the TNF family of ligands and receptors

TNF family ligands and receptors fulfill a number of functions, mainly in the immune system. For example, the ligands BAFF and APRIL control growth and survival of mature Β cells at various stages of differentiation. TNF family ligands usually form homotrimers, but heteromers have also been described for lymphotoxin α1β2 and for BAFF and APRIL. Interestingly, twenty BAFF homotrimers can assemble into virus-like particles coined BAFF 60-mer, which are superior to BAFF 3-mer regarding their ability to signal in primary Β cells. A screen was performed in 293T cells, by co-transfecting differently tagged ligands, to identify six novel heteromers. The specificity of these novel heteromers, however, did not correspond to that of orphan receptors in the TNFR family. Little is known about heteromers of BAFF and APRIL, in particular their receptor-binding specificity and their ability to signal. A method to produce and purify heteromers of defined stoechiometry was developed, and the resulting reagents were used to demonstrate that BAFF2APRIL, like BAFF, binds to all BAFF receptors - namely BAFFR, TACI and Β CM A -, while APRIL2BAFF and APRIL only binds to TACI and BCMA. Heteromers could signal via their cognate receptors, sometimes as potently and sometimes less potently than homomers, depending on the receptors. A promising system to measure the activity of single-chain homo- and heteromers in vivo was set up: it measures mature Β cell rescue upon administration of single-chain ligands into BAFF-ko mice. To tackle the question of the physiological importance of BAFF 60-mer, a point mutation that prevents assembly of mouse BAFF into 60-mer while retaining its ability to form trimers was identified. This mutation (E247K) was introduced by homologous recombination into mouse embryonic stem cells that are now being used to generate knock-in mice. Results obtained in this work will help to better understand the role of various BAFF and APRIL forms that are elevated in a several autoimmune diseases. - Les ligands et récepteurs de la famille du TNF joue un rôle prédominant dans le système immunitaire. Par exemple, les ligands BAFF et APRIL contrôlent la croissance et la survie des cellules Β matures à différents stades de différenciation. Ces ligands existent souvent sous forme d'homotrimères (3-mer), bien que des héteromères aient été décrits pour la lymphotoxine α1β2 et pour BAFF et APRIL. Dans le cas de BAFF, vingt trimères peuvent, telle une particule virale, s'assembler en 60-mer qui surpasse le 3-mer pour signaler dans des cellules Β primaires. Un crible effectué dans des cellules 293T, par co-transfection de ligands différemment marqués, a permis d'identifier six nouveaux heteromères dont la spécificité n'a, hélas, pas correspondu à celle d'un récepteur orphelin de la famille du TNFR. Les connaissances sur la spécificité de liaison aux récepteurs et la capacité à signaler des heteromères de BAFF et d'APRIL sont fragmentaires. Une méthode pour produire et purifier des heteromères "simple chaîne" de stoechiométrie déterminée a été mise au point, et les réactifs ainsi obtenus utilisés pour démontrer que BAFF2APRIL, comme BAFF, lie tous les récepteurs de BAFF - c'est-à-dire BAFFR, TACI et BCMA -, alors qu'APRIL2BAFF et APRIL ne lient que TACI et BCMA. Les héteromères peuvent transmettre des signaux, parfois aussi bien et parfois plus faiblement que les homomères, selon les récepteurs. Un système prometteur pour mesurer l'activité des ligands simple chaîne in vivo a été mis au point. Il mesure la réapparition de cellules Β matures dans des souris déficientes pour BAFF après administration des ligands. Pour s'attaquer à la question de l'importance physiologique du 60-mer de BAFF, ime mutation empêchant l'assemblage en 60-mer sans affecter la capacité à former des trimères a été identifiée. Cette mutation (E247K) a été introduite par recombinaison homologue dans des cellules souches embryonnaires de souris qui sont utilisées pour obtenir des souris déficientes en BAFF 60-mer. Les résultats de ces travaux contribueront à mieux cerner le rôle des différentes formes de BAFF et d'APRIL produites en excès dans plusieurs maladies auto-immunes.

An Adenovirus Vector Containing the Suicide Gene Thymidine Kinase for a Broad Application in Cancer Gene Therapy

Treatment of cancer using gene therapy is based on adding a property to the cell leading to its elimination. One possibility is the use of suicide genes that code for enzymes that transform a pro-drug into a cytotoxic product. The most extensively used is the herpes simplex virus thymidine kinase (TK) gene, followed by administration of the antiviral drug ganciclovir (GCV). The choice of the promoter to drive the transcription of a transgene is one of the determinants of a given transfer vector usefulness, as different promoters show different efficiencies depending on the target cell type. In the experiments presented here, we report the construction of a recombinant adenovirus carrying TK gene (Ad-TK) driven by three strong promoters (P CMV IE, SV40 and EN1) and its effectiveness in two cell types. Human HeLa and mouse CCR2 tumor cells were transduced with Ad-TK and efficiently killed after addition of GCV. We could detect two sizes of transcripts of TK gene, one derived from the close together P CMV IE/SV40 promoters and the other from the 1.5 Kb downstream EN1 promoter. The relative amounts of these transcripts were different in each cell type thus indicating a higher flexibility of this system.

Analysis of angiotensin II- and ACTH-driven mineralocorticoid functions and omental adiposity in a non-genetic, hyperadipose female rat phenotype

The hypothalamic damage induced by neonatal treatment with monosodium l-glutamate (MSG) induces several metabolic abnormalities, resulting in a rat hyperleptinemic-hyperadipose phenotype. This study was conducted to explore the impact of the neonatal MSG treatment, in the adult (120 days old) female rat on: (a) the in vivo and in vitro mineralocorticoid responses to ACTH and angiotensin II (AII); (b) the effect of leptin on ACTH- and AII-stimulated mineralocorticoid secretions by isolated corticoadrenal cells; and (c) abdominal adiposity characteristics. Our data indicate that, compared with age-matched controls, MSG rats displayed: (1) enhanced and reduced mineralocorticoid responses to ACTH and AII treatments, respectively, effects observed in both in vivo and in vitro conditions; (2) adrenal refractoriness to the inhibitory effect of exogenous leptin on ACTH-stimulated aldosterone output by isolated adrenocortical cells; and (3) distorted omental adiposity morphology and function. This study supports that the adult hyperleptinemic MSG female rat is characterized by enhanced ACTH-driven mineralocorticoid function, impaired adrenal leptin sensitivity, and disrupted abdominal adiposity function. MSG rats could counteract undesirable effects of glucocorticoid excess, by developing a reduced AII-driven mineralocorticoid function. Thus, chronic hyperleptinemia could play a protective role against ACTH-mediated allostatic loads in the adrenal leptin resistant, MSG female rat phenotype.

The JNK binding domain of islet-brain 1 inhibits IL-1 induced JNK activity and apoptosis but not the transcription of key proapoptotic or protective genes in insulin-secreting cell lines.

The stress-activated protein kinase c-Jun NH2-terminal kinase (JNK) is a central signal for interleukin-1beta (IL-1beta)-induced apoptosis in insulin-producing beta-cells. The cell-permeable peptide inhibitor of JNK (JNKI1), that introduces the JNK binding domain (JBD) of the scaffold protein islet-brain 1 (IB1) inside cells, effectively prevents beta-cell death caused by this cytokine. To define the molecular targets of JNK involved in cytokine-induced beta-cell apoptosis we investigated whether JNKI1 or stable expression of JBD affected the expression of selected pro- and anti-apoptotic genes induced in rat (RIN-5AH-T2B) and mouse (betaTC3) insulinoma cells exposed to IL-1beta. Inhibition of JNK significantly reduced phosphorylation of the specific JNK substrate c-Jun (p&lt;0.05), IL-1beta-induced apoptosis (p&lt;0.001), and IL-1beta-mediated c-fos gene expression. However, neither JNKI1 nor JBD did influence IL-1beta-induced NO synthesis or iNOS expression or the transcription of the genes encoding mitochondrial manganese superoxide dismutase (MnSOD), catalase (CAT), glutathione peroxidase (GPx), glutathione-S-transferase rho (GSTrho), heat shock protein (HSP) 70, IL-1beta-converting enzyme (ICE), caspase-3, apoptosis-inducing factor (AIF), Bcl-2 or Bcl-xL. We suggest that the anti-apoptotic effect of JNK inhibition by JBD is independent of the transcription of major pro- and anti-apoptotic genes, but may be exerted at the translational or posttranslational level.

Leptin inhibits directly glucocorticoid secretion by normal human and rat adrenal gland.

Different interactions have been described between glucocorticoids and the product of the ob gene leptin. Leptin can inhibit the activation of the hypothalamo-pituitary-adrenal axis by stressful stimuli, whereas adrenal glucocorticoids stimulate leptin production by the adipocyte. The present study was designed to investigate the potential direct effects of leptin to modulate glucocorticoid production by the adrenal. Human adrenal glands from kidney transplant donors were dissociated, and isolated primary cells were studied in vitro. These cells were preincubated with recombinant leptin (10(-10)-10(-7) M) for 6 or 24 h, and basal or ACTH-stimulated cortisol secretion was subsequently measured. Basal cortisol secretion was unaffected by leptin, but a significant and dose-dependent inhibition of ACTH-stimulated cortisol secretion was observed [down by 29 +/- 0.1% of controls with the highest leptin dose, P &lt; 0.01 vs. CT (unrelated positive control)]. This effect of leptin was also observed in rat primary adrenocortical cells, where leptin inhibited stimulated corticosterone secretion in a dose-dependent manner (down by 46 +/- 0.1% of controls with the highest leptin dose, P &lt; 0.001 vs. CT). These effects of leptin in adrenal cells are likely mediated by the long isoform of the leptin receptor (OB-R), because its transcript was found to be expressed in the adrenal tissue and leptin had no inhibitory effect in adrenal glands obtained from db/db mice. Therefore, leptin inhibits directly stimulated cortisol secretion from human and rat adrenal glands, and this may represent an important mechanism to modulate glucocorticoid levels in various metabolic states.

Role of notch signalling in mammary gland

ÁBSTRACT : Mammary gland is composed of two main epithelial cell types, myoepithelial and luminal. The mechanisms involved in determination and maintenance of them remain poorly understood. Notch signaling is known to regulate cell fate determination in other tissues like skin and nervous system. It was also shown that it can act as tumor suppressor or oncogene depending on the tissue type. The mouse models overexpressing active Notch receptors indicated that Notch signaling is oncogenic in the mammary gland. This observation was followed by some descriptive and functional studies in human breast cancer and it was reported that Notch signaling activity or expression of its components are increased in some of the breast tumor samples compared to normal tissue. However, the physiological role of the Notch signaling and its downstream mechanisms in mammary gland is poorly defined. p63, a member of p53 family, has been implicated in the cell fate determination of keratinocytes. Knockout mouse models revealed that p63 is required for the formation of the mammary anlagen in embryo and its ΔN isoform is expressed exclusively in the myoepithelial layer of the adult breast. In order to understand its function in normal breast epithelial cells, I activated Notch signaling by expression of Notch1 intracellular domain (NICD) in normal primary human breast epithelial cells (HBECs). In this context, NICD reduced growth of HBECs and led to downmodulation of extracellular matrix-receptor interaction network (ECM) components as well as ΔNp63. Expression of ΔNp63 together with NICD partially rescued Notch induced growth reduction, which was correlated with an increase in ECM components. Moreover, silencing ΔNp63 in myoepithelial HBECs reduced growth similar to Notch activation and it led to downregulation of myoepithelial and upregulation of luminal markers. Complementing this observation, forced expression of ONp63 in luminal HBECs induced myoepithelial phenotype and decreased luminal markers. In vivo, by the analysis of a Notch reporter mouse strain, I showed that Notch is activated during puberty specifically at the sites of ductal morphogenesis, terminal end buds. FAGS analysis revealed that it can be detected in two different populations based on CD24 expression (low (lo) or high (high)): at lower levels in CD24lo, which includes stem/progenitor and myoepithelial cells and higher levels in CD24hi, which contains luminal cells. In parallel with in vitro results, the CD24lo mouse mammary epithelial cells displaying Notch activity have lower levels of p63 expression. Furthermore, deletion of RBPjk, the main mediator of Notch signaling, or the overexpression of ΔNp63 inhibited luminal cell lineage in vivo. Another important point revealed by Notch reporter mouse strain is the simultaneous activation of Notch with estrogen signaling during pubertal development. The expression of FOXA1, the mediator of estrogen receptor (ER) transcriptional activity, is correlated with Notch activation in vivo that it is lower in CD24lo than in CD24hi cells. Moreover, FOXA1 is regulated by NICD in vitro supporting the presence of a link between Notch and ER signaling. Taken together, I report that Notch signaling is involved in luminal cell fate determination and its effects are partially mediated through inhibition of ONp63. Besides, ΔNp63 is required for the maintenance and sufficient for the induction of myoepithelial phenotype in HBECs in vitro and is not compatible with luminal lineage in vivo. Based on these results, I propose a model for epithelial cell hierarchy in mammary gland, whereby there are two different types of luminal progenitors, early and late, displaying different levels of Notch activity. Notch signaling contributes to the determination of luminal cell lineage in these two progenitor steps: In "Early Luminal Progenitor" stage, it inhibits myoepithelial fate by decreasing p63 expression, and in "Late Luminal Progenitor" stage, Notch signaling is involved in induction of luminal lineage by acting on ER-FOXA1 axis. It has to be investigated further whether Notch signaling might behave as an oncogene or tumor suppressor depending on which cell type in the epithelial hierarchy it is modulated and which one is more likely to occur in different human breast cancer types. RÉSUMÉ : La glande mammaire est composée de deux types principaux de cellules: les cellules luminales, qui bordent le lumen et les cellules myoépithéliales, qui se trouvent entre la lame basale et les cellules luminales. Les mécanismes intervenant dans leur différenciation et leur maintenance demeurent encore mal compris. La protéine transmembranaire Notch est connue pour déterminer le destin des cellules dans plusieurs types de tissus comme la peau ou le système nerveux. Selon le type de tissu dans lequel se trouve Notch, il agira soit comme un suppresseur de tumeur soit comme un oncogène. A l'aide de modèles de souris surexprimant les récepteurs actifs de Notch, il a été démontré que la voie de signalisation de Notch est oncogénique au niveau de la glande mammaire. Des études descriptives et fonctionnelles dans le cadre du cancer du sein ont permis de mettre en évidence une augmentation de l'activité de Notch ou de l'expression de ces composants dans certains tissus cancéreux. Toutefois, le rôle physiologique de Notch et des mécanismes qu'il active restent méconnus. P63, une protéine membre de la famille p53, est impliquée dans la différenciation des kératinocytes. Le modèle issu de l'étude des souris p63 knockout a révélé que cette protéine est requise pour la formation des primordia mammaires chez l'embryon et que son isoforme ΔNp63 est exclusivement exprimée dans la couche myoépithéliale de la glande mammaire adulte. Dans le but de comprendre les fonctions physiologiques de Notch, je l'ai activé en exprimant le domaine intracellulaire de Notch 1 (NICD) dans des cellules épithéliales primaires de glande mammaire humaine (HBECs). Le NICD a alors réduit la croissance des HBECs et conduit à la régulation négative non seulement de p63 mais également des composants du réseau d'interaction des récepteurs de la matrice extracellulaire (ECM). En exprimant conjointement ΔNp63 et NICD, il est apparu que la réduction de croissance induite par Notch était partiellement compensée, et qu'il y avait également une augmentation des composants ECM. De plus, lorsque ΔNp63 a été inactivé dans les cellules HBECs myoépithéliales, une réduction de croissance cellulaire identique à celle provoquée par l'activation de Notch a pu être mise en évidence, de même qu'une régulation négative des marqueurs myoépithéliaux ainsi qu'une augmentation des marqueurs luminaux. Afin de compléter ces informations, l'expression de ΔNp63 a été forcée dans les HBECs luminales, ce qui a induit un phénotype myoépithélial et une diminution des marqueurs lumineux. In vivo, par l'analyse de souris ayant un gène rapporteur de l'activité de Notch, j'ai démontré que Notch est activé pendant la puberté au niveau des sites de la morphogenèse canalaire, à savoir les bourgeons terminaux. Les analyses par FACS (Fluorescence-activated cell sorting) basées sur l'expression de l'antigène CD24 ont révélé qu'il peut tre détecté dans deux populations différentes : une population qui l'exprime faiblement, qui regroupe les cellules souches/progéniteurs et les cellules myoépithéliales, et une population qui l'exprime fortement qui est composé des cellules luminales. Parallèlement aux résultats in vitro, j'ai mis en évidence un faible niveau d'expression de p63 dans les cellules épithéliales de la glande mammaire de souris, exprimant faiblement l'antigène CD24 et présentant une activité de Notch. De plus, la délétion de RBPjr~, médiateur principal de la signalisation de Notch, ainsi que la surexpression de ΔNp63 in vivo ont inhibé la lignée des cellules luminales. Un autre point important révélé par les souris rapporteur de l'activité de Notch a été l'activation simultanée de Notch et de la signalisation de l'oestrogène pendant le développement pubertaire. L'expression de FOXA1, médiateur de l'activité transcriptionnelle des récepteurs aux oestrogènes (ER), est en corrélation avec l'activation de Notch in vivo, plus basse dans les cellules avec une faible expression de l'antigène CD24 que dans celles avec une forte expression. De plus, FOXA1 est régulé par NICD in vitro confirmant la présence d'un lien entre Notch et la signalisation des ER. En résumé, la signalisation de Notch est impliquée dans la détermination du destin cellulaire des cellules luminales et ses effets sont partiellement modifiés par l'inhibition de ΔNp63. ΔNp63 est requis pour la maintenance et est suffisant pour l'induction du phénotype myoépithéliale dans les HBECs in vitro et ne peut donc pas se trouver dans les cellules luminales in vivo. Basé sur ces résultats, je propose un modèle de hiérarchisation des cellules épithéliales de la glande mammaire, dans lequel sont présents deux types de progéniteurs des cellules luminales exprimant des niveaux différents d'activité de Notch, les progéniteurs lumineux précoces et tardifs. La signalisation de Notch contribue à la différenciation de la lignée cellulaire luminale au niveau de ces deux progéniteurs : dans la forme précoce, il inhibe la différenciation des cellules myoépithéliales en réduisant l'expression de p63 et dans la forme tardive, Notch est impliqué dans l'induction de la lignée luminale en agissant sur l'axe ER-FOXA1. Il serait nécessaire d'investiguer plus loin si le fait que Notch agisse comme oncogène ou suppresseur de tumeur dépend du stade de différenciation de la cellule dans laquelle il est modulé et laquelle de ces deux fonctions il est le plus probable de rencontrer dans les différents types de cancer du sein.

Food-dependent Cushing's syndrome: possible involvement of leptin in cortisol hypersecretion.

Stimulation ofcortisol secretion by food intake has been implicated in the pathogenesis of some cases of ACTH-independent Cushing's syndrome, via an aberrant response of the adrenal glands to gastric inhibitory polypeptide (GIP). We report here a novel case of food-dependent Cushing's syndrome in a patient with bilateral macronodular adrenal hyperplasia. In this patient we were able to confirm a paradoxical stimulation of cortisol secretion by GIP in vivo as well as in vitro on dispersed tumor adrenal cells obtained at surgery. In addition to GIP, in vitro stimulation of these cultured tumor adrenal cells with leptin, the secreted product of the adipocyte, induced cortisol secretion. By comparison, no such stimulation was observed in vitro in adrenal cells obtained from another patient with bilateral macronodular adrenal hyperplasia and Cushing's syndrome that did not depend on food intake, in tumor cells obtained from a solitary cortisol-secreting adrenal adenoma, and in normal human adrenocortical cells. These results demonstrate that as in previously described cases of food-dependent Cushing's syndrome, GIP stimulated cortisol secretion from the adrenals of the patient reported here. Therefore, they indicate that such a paradoxical response probably represents the hallmark of this rare condition. In addition, they suggest that leptin, which normally inhibits stimulated cortisol secretion in humans, participated in cortisol hypersecretion in this case. Further studies in other cases of food-dependent Cushing's syndrome, however, will be necessary to better ascertain the pathophysiological significance of this finding.