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No description available.

A via RAS/RAF/MEK/ERK é frequentemente hiperativada em diversos tumores. Em leucemias sua ativação pode ocorrer, dentre outros mecanismos, a partir de mutações pontuais nos genes da família RAS, que são relevantes nas leucemias linfóide e mielóide agudas (LLA e LMA), ou a partir da atividade da tirosina-quinase BCR-ABL, que é responsável por promover a tumorigênese na leucemia mielóide crônica (LMC) e em alguns casos de LLA. A hiperativação dessa via estimula a proliferação celular e, consequentemente, a produção de espécies reativas de oxigênio (ROS), que é um dos principais mecanismos envolvidos com a indução de senescência celular em tumores. Assim sendo, as células tumorais que apresentam o gene RAS mutado são criticamente dependentes de mecanismos de feedback para regular a ativação da via. Jang et al. demonstraram que a ubiquitina-ligase HUWE1 atua em um mecanismo de feedback negativo que controla a ativação de ERK1/2 e apesar de amplamente estudada no contexto da tumorigênese, a atuação dessa molécula em eventos relacionados à leucemogênese ainda não foi descrita. No presente estudo, linhagens celulares leucêmicas e células tronco e progenitoras hematopoiéticas humanas (HSPCs) com mutação KRASG12V foram transduzidas com partículas lentivirais miR-E para o silenciamento gênico de HUWE1. Ensaios de proliferação celular, apoptose, análise do ciclo celular, produção de ROS e análise da expressão gênica e proteica foram realizados nas linhagens celulares; análise do crescimento cumulativo, área de formação de cobblestones, capacidade clonogênica e análise do perfil de diferenciação celular foram realizados nas HSPCs. Nas linhagens celulares observouse que o silenciamento de HUWE1 reduziu a capacidade proliferativa das linhagens Nalm-6, K562 e THP-1, porém não causou nenhum prejuízo à capacidade proliferativa da linhagem HL-60. Além disso, causou a redução da produção de ROS (p<0,05), associada à redução das taxas de apoptose (p<0,01), principalmente na linhagem K562, na qual também promoveu a ativação de ERK1/2 . Em HSPCs, observou-se a redução da capacidade proliferativa das culturas que expressavam o oncogene KRASG12V associado ao silenciamento de HUWE1. Nas mesmas condições foi observada uma drástica redução na capacidade clonogênica das HSPCs (p<0,001), em especial as do tipo BFU-E. O silenciamento de HUWE1 também alterou o perfil de diferenciação celular para a linhagem monocítica. Os resultados sugerem que HUWE1 pode participar do processo de leucemogênese e diferenciação de HSPCs humanas participando na modulação da via RAS/RAF/MEK/ERK. / The RAS/RAF/MEK/ERK pathway is frequently hyperactivated in several tumors. In leukemia, this activation can arise, among other mechanisms, from point mutations in the RAS genes, which are important in acute lymphoid leukemia (ALL) and acute myeloid leukemia (AML), or from chromosomal translocations such as the BCR-ABL gene, which is a driver mutation in chronic myeloid leukemia (CML) and some cases of ALL. The hyperactivation of this pathway stimulates cell proliferation and, consequently, the production of reactive oxygen species (ROS), which is one of the main mechanisms involved with induction of cellular senescence in tumors. Thus, tumor cells that harbor the mutated RAS gene are critically dependent on feedback mechanisms to regulate pathway activation. Jang et al. demonstrated that the ubiquitinligase HUWE1 acts on a negative feedback mechanism that controls the activation of ERK1/2. Although widely studied in the context of tumorigenesis, the role of this molecule in events related to leukemogenesis has not yet been described. In this study, leukemia cell lines and human hematopoietic stem and progenitors cells (HSPCs) with KRASG12V mutation were transduced with miR-E lentiviral particles for HUWE1 knockdown. Cell proliferation, apoptosis, cell cycle analysis, ROS production and analysis of gene and protein expression were performed in cell lines; cumulative growth analysis, cobblestones area formations, clonogenic capacity and differentiation profile analysis were performed in HSPCs. In cell lines, it was observed that HUWE1 knockdown reduced the proliferative capacity of Nalm-6, K562 and THP-1, but not of HL-60. Besides that, it caused a reduction in ROS production (p<0,05), associated with reduction of apoptosis rates (p<0,01), especially in K562 in which it also promoted activation of ERK1/2. In HSPCs, a reduction of the proliferative capacity was observed in cultures expressing KRASG12V in combination with HUWE1 knockdown. In the same conditions, a drastic reduction of clonogenic capacity (p<0,001), especially of BFU-E colonies, was observed. HUWE1 knockdown also changed differentiation profile to the monocytic lineage. Results suggest that HUWE1 might play a role in leukemogenesis process and differentiation of human HSPCs, acting in the modulation of RAS/RAF/MEK/ERK.

A via RAS/RAF/MEK/ERK é frequentemente hiperativada em diversos tumores. Em leucemias sua ativação pode ocorrer, dentre outros mecanismos, a partir de mutações pontuais nos genes da família RAS, que são relevantes nas leucemias linfóide e mielóide agudas (LLA e LMA), ou a partir da atividade da tirosina-quinase BCR-ABL, que é responsável por promover a tumorigênese na leucemia mielóide crônica (LMC) e em alguns casos de LLA. A hiperativação dessa via estimula a proliferação celular e, consequentemente, a produção de espécies reativas de oxigênio (ROS), que é um dos principais mecanismos envolvidos com a indução de senescência celular em tumores. Assim sendo, as células tumorais que apresentam o gene RAS mutado são criticamente dependentes de mecanismos de feedback para regular a ativação da via. Jang et al. demonstraram que a ubiquitina-ligase HUWE1 atua em um mecanismo de feedback negativo que controla a ativação de ERK1/2 e apesar de amplamente estudada no contexto da tumorigênese, a atuação dessa molécula em eventos relacionados à leucemogênese ainda não foi descrita. No presente estudo, linhagens celulares leucêmicas e células tronco e progenitoras hematopoiéticas humanas (HSPCs) com mutação KRASG12V foram transduzidas com partículas lentivirais miR-E para o silenciamento gênico de HUWE1. Ensaios de proliferação celular, apoptose, análise do ciclo celular, produção de ROS e análise da expressão gênica e proteica foram realizados nas linhagens celulares; análise do crescimento cumulativo, área de formação de cobblestones, capacidade clonogênica e análise do perfil de diferenciação celular foram realizados nas HSPCs. Nas linhagens celulares observouse que o silenciamento de HUWE1 reduziu a capacidade proliferativa das linhagens Nalm-6, K562 e THP-1, porém não causou nenhum prejuízo à capacidade proliferativa da linhagem HL-60. Além disso, causou a redução da produção de ROS (p<0,05), associada à redução das taxas de apoptose (p<0,01), principalmente na linhagem K562, na qual também promoveu a ativação de ERK1/2 . Em HSPCs, observou-se a redução da capacidade proliferativa das culturas que expressavam o oncogene KRASG12V associado ao silenciamento de HUWE1. Nas mesmas condições foi observada uma drástica redução na capacidade clonogênica das HSPCs (p<0,001), em especial as do tipo BFU-E. O silenciamento de HUWE1 também alterou o perfil de diferenciação celular para a linhagem monocítica. Os resultados sugerem que HUWE1 pode participar do processo de leucemogênese e diferenciação de HSPCs humanas participando na modulação da via RAS/RAF/MEK/ERK. / The RAS/RAF/MEK/ERK pathway is frequently hyperactivated in several tumors. In leukemia, this activation can arise, among other mechanisms, from point mutations in the RAS genes, which are important in acute lymphoid leukemia (ALL) and acute myeloid leukemia (AML), or from chromosomal translocations such as the BCR-ABL gene, which is a driver mutation in chronic myeloid leukemia (CML) and some cases of ALL. The hyperactivation of this pathway stimulates cell proliferation and, consequently, the production of reactive oxygen species (ROS), which is one of the main mechanisms involved with induction of cellular senescence in tumors. Thus, tumor cells that harbor the mutated RAS gene are critically dependent on feedback mechanisms to regulate pathway activation. Jang et al. demonstrated that the ubiquitinligase HUWE1 acts on a negative feedback mechanism that controls the activation of ERK1/2. Although widely studied in the context of tumorigenesis, the role of this molecule in events related to leukemogenesis has not yet been described. In this study, leukemia cell lines and human hematopoietic stem and progenitors cells (HSPCs) with KRASG12V mutation were transduced with miR-E lentiviral particles for HUWE1 knockdown. Cell proliferation, apoptosis, cell cycle analysis, ROS production and analysis of gene and protein expression were performed in cell lines; cumulative growth analysis, cobblestones area formations, clonogenic capacity and differentiation profile analysis were performed in HSPCs. In cell lines, it was observed that HUWE1 knockdown reduced the proliferative capacity of Nalm-6, K562 and THP-1, but not of HL-60. Besides that, it caused a reduction in ROS production (p<0,05), associated with reduction of apoptosis rates (p<0,01), especially in K562 in which it also promoted activation of ERK1/2. In HSPCs, a reduction of the proliferative capacity was observed in cultures expressing KRASG12V in combination with HUWE1 knockdown. In the same conditions, a drastic reduction of clonogenic capacity (p<0,001), especially of BFU-E colonies, was observed. HUWE1 knockdown also changed differentiation profile to the monocytic lineage. Results suggest that HUWE1 might play a role in leukemogenesis process and differentiation of human HSPCs, acting in the modulation of RAS/RAF/MEK/ERK.

Les cancers ovariens, se développant de façon silencieuse, diagnostiqués à des stades tardifs et de mauvais pronostiques, requièrent urgemment la mise au point de nouvelles options thérapeutiques. Ma thèse s'est attachée à caractériser les propriétés physiques et biologiques des cancers ovariens Séreux de Haut Grade (HGSOC), représentant 75% des tumeurs ovariennes.En premier lieu, nous avons démontré la valeur pronostique de la protéine MAP3K8 s'accumulant dans les HGSOC. Nous avons montré que MAP3K8 contrôle la prolifération et la migration des cellules cancéreuses via la transition G 1/S et les mécanismes d'adhésion dynamique. Aussi, nous avons mis en évidence que MAP3K8 active majoritairement la voie MEK, présentant ainsi un potentiel prédictif des inhibiteurs de MEK, les positionnant comme une stratégie thérapeutique prometteuse, en combinaison des thérapies conventionnelles, chez les HGSOC.Dans un second axe de ma thèse, nous avons montré que la rigidité augmente avec la taille tumorale, chez les HGSOC présentant une signature moléculaire « Fibrose ». Cette rigidification tumorale s'associe à une accumulation de stroma et un remodelage du réseau de collagène, mais aussi à une activation spécifique de la voie MEK. De façon intéressante, la rigidification tumorale accompagne un « switch » métabolique glycolytique, restreint au centre de la tumeur, la périphérie demeurant plus molle, et différant par une production élevée de collagène et un métabolisme OXPHOS. La rigidité pourrait donc être au carrefour de 3 processus majeurs, tels un remodelage de la matrice, l'activation de MEK et un switch métabolique stromal, expliquant, au moins en partie, la progression des HGSOC. / Ovarian cancers, which develop in a silent manner in the peritoneal cavity, resulting in a late diagnosis and a poor prognosis, urgently require new therapeutic strategies. In this context, my thesis aimed at better characterize the physical and biological properties of the High Grade Serous ovarian cancers (HGSOCs), accounting for 75% of the tumours.First, we found that the protein MAP3K8 accumulates in HGSOC and is a potential prognostic marker for these tumours. We demonstrated that MAP3K8 controls cancer cell proliferation and migration by regulating key players in Gl/S transition and adhesion dynamics. Importantly, we highlighted that MAP3K8 function is mainly mediated by the MEK pathway, and exhibits a predictive potential for MEK inhibitors, defining them as a promising therapeutic option, in combination with conventional therapy, for HGSOC patients.In a second part of my thesis, we showed that tumor stiffness is increased during tumor growth in HGSOC presenting a "Fibrosis" molecular signature. Moreover, tumor stiffening is associated with high stromal content and remodeling of the collagen network. Interestingly, the MEK kinase was specifically activated upon tumor stiffening. Furthermore, tumor stiffness accompanies a glycolytic metabolic switch, restricted to the central part of stiff tumors. Indeed, the periphery of stiff tumors remains softer than the central part with stromal cells secreting high levels of collagens and showing an OXPHOS metabolism. Thus, tumor stiffness could be at the crossroad of three major processes, i.e. matrix remodeling, MEK activation and stromal metabolic switch, that might explain, at least in part, the progression of HGSOC.

De plus en plus d’inhibiteurs de kinase (IKs) sont testés dans le cancer de la prostate qui représente chez l’homme un enjeu de santé publique majeur de par son incidence (1er cancer) et sa mortalité (4ème cancer). Les essais cliniques pour évaluer l'efficacité des IKs dans cette indication ont donné des résultats mitigés malgré la présence de leurs cibles pharmacologiques dans les tumeurs de prostate (VEGF, EGFR, CMET..), pouvant faire penser que l’inefficacité serait en partie liée à la molécule elle-même et à sa pharmacocinétique/pharmacodynamie. En effet, les IKs sont sujets à un métabolisme et un transport intense via des enzymes de phase I et II et des transporteurs contrôlés pour la majorité par le récepteur nucléaire PXR (Pregnane X Receptor, gène NR1I2). En plus d’être abondamment exprimé dans le foie et le long du tractus gastro-intestinal, PXR est également exprimé dans certaines tumeurs épithéliales et pourrait être impliqué dans la résistance aux chimiothérapies par augmentation du catabolisme et de l’efflux de ces agents anticancéreux. A ce jour une seule étude a révélé l’expression de PXR dans le cancer de la prostate sans en avoir évalué l’impact sur la réponse aux traitements utilisés dans cette indication. En collaboration avec le Pr G. Fromont, nous avons observé dans une cohorte de 449 patients que l’expression de PXR était plus fréquemment retrouvée dans les cancers résistants à la castration et les métastases, par rapport aux cancers cliniquement localisés dans lesquels l’expression de PXR était corrélée avec le stade TNM et le score ISUP. Ces résultats confirment donc l’intérêt d’étudier le rôle que peut jouer PXR et les gènes du métabolisme et du transport qu’il régule, dans la sensibilité aux IKs dans les cancers de la prostate.Nous avons mesuré l’expression de PXR et de ses gènes cibles dans les lignées de cancer de la prostate 22RV1, LnCap, PC3 et DU145. Les résultats montrent une expression significative des enzymes et transporteurs responsables de la détoxication des IKs mais une faible expression de PXR liée à des phénomènes d’hyperméthylation NR1I2 dans nos lignées Cela nous a conduit à établir des modèles de surexpression stable de PXR dans lesquels l’agoniste SR12813 est capable d’induire l’activité transcriptionnelle de ce xénorécepteur, indiquant la compétence métabolique de ces lignées. À l'aide de ces modèles, nous avons démontré que la surexpression de PXR module la réponse à l’erlotinib, le dasatinib, le dabrafénib et l’afatinib démontrant que PXR joue un rôle fonctionnel dans la sensibilité à ces IKs. Nous avons également démontré que certains inhibiteurs avaient des propriétés agonistes de PXR, notamment le dabrafénib qui montre un effet agoniste plus marqué que le composé de référence SR12813, ce qui n’a jamais été démontré. Cette découverte originale nous a conduit à engager une collaboration pour tenter de cristalliser le complexe PXR/dabrafénib et à tester l’hypothèse que l’induction de l’activité PXR pouvait entraîner une modification du métabolisme et/ou du transport d’autres médicaments co-administrés. Or, nous avons observé dans la lignée 22RV1 un effet additif entre le dabrafénib et le tramétinib, une combinaison approuvée dans le traitement du mélanome, qui devient antagoniste lorsque PXR est surexprimé, résultat qui va effectivement dans le sens de notre hypothèse même s’il reste à démontrer que cet effet est bien lié à une altération du métabolisme de ces IKs, ce que nous sommes en train d’évaluer en dosant les métabolites de ces IKs. L’ensemble de nos données pourraient servir de rationnel biologique dans le choix des IKs ou de leurs combinaisons à tester avec les hormonothérapies et chimiothérapies déjà utilisés dans le traitement du cancer de la prostate, afin de potentialiser la réponse tumorale. / More and more kinase inhibitors (KIs) are tested in prostate cancer that represents a major health issue in men with its incidence and mortality rates. Clinical trials to evaluate KIs efficacy in prostate cancer gave disapointing results depsite the presence of KIs pharmacological targets in prostate tumors (VEGF, EGFR, CMET..), suggesting that inefficiency of these drugs would be at least in part linked to the inhibitor itself or its pharmacodynamics/pharmacokinetics parameters. Indeed KIs are metabolized and transported via phase I and II enzymes that are mainly controlled by the xenoreceptor PXR (Pregnane X Receptor, gène NR1I2). It is mainly expressed in liver and gastro-intestinal tract but also in epithelial tumors. PXR is also involved in the resistance to chemotherapies by increasing the catabolism and the efflux of these anticancer agents. To date only one study evaluated PXR expression in prostate cancer without evaluating its impact on treatment efficacy. In collaboration with Pr G. Fromont we analyzed a cohort of 449 prostate tumors and observed that PXR was more frequently detected in castration resistant or metastatic tumors as compared to clinically localized forms in which PXR expression was significantly correlated with TNM and ISUP Score. These results confirmed the interest to study the potential role of PXR and its target genes in the sensitivity to kinase inhibitors in prostate cancer models.We measured the expression of PXR and its target genes in prostate cancer cell lines 22RV1, LnCap, PC3 and DU145. The results showed that enzymes and transporters involved in KI detoxification was significantly expressed in these cells whereasPXR was poorly expressed due to hypermethylation of NR1I2 in our cells. This lead us to develop specific prostate cancer cell models stably overexpressing PXR in which transcriptional activity of PXR can be induced by its known agonist SR12813 further indicating that prostate cancer cells are metabolically competent. Using these models we showed that PXR overexpression modulates the sensitivity of 22RV1 cells to erlotinib, dasatinib, dabrafenib and afatinib, demonstrating that PXR plays a functional role in the sensitivity to KIs. We also demonstrated that several KIs were PXR agonists, including dabrafenib that displayed enhanced agonistic properties as compared to SR12813, a result that was never published before. This original finding led us to engage the cristalization of PXR/dabrafenib complex and to test whether induction of PXR could lead to an alteration of metabolism and transport of other drugs that are co-administered. In this line we have observed that in 22RV1 cells the additive effect of the combination of dabrafenib with trametinib that is already approved in the treatment of melanomas, became antagonistic when PXR was overexpressed in these cells. This result is supporting our hypothesis though we still need to demonstrate that this effect is linked to a change in drugs metabolism, which is currently under investigation by the measurement of the known metabolites of these KIs.Altogether, our data could serve as rational basis for the choice of kinase inhibitors or their potential combinations that could be tested in further clinical trials alone or in association with hormone therapies or with chemotherapies that are currently prescribed in the treatment of advanced prostate cancers, in order to potentiate tumor response.

L'objectif de ce travail est de synthétiser des nanomatériaux de TiO2 pour la dégradation des COV et pour l'élimination des bactéries en surface. Tout d'abord, basé sur une synthèse des matériaux de TiO2 avec la présence d’un liquide ionique BmimPF6 par une voie sol-gel modifiée, les rôles de deux éléments constitutifs de BmimPF6 (P et F) ont été étudiés en faisant remplacer BmimPF6 par des additives contenant P et F. Par rapport à la référence P25 et aux matériaux de TiO2 synthétisés sans additif, le TiO2 synthétisé en présence de P a déjà montré une meilleure cristallinité en phase anatase avant la calcination, et une surface spécifique élevée et une petite taille moyenne des cristaux étaient maintenus même après calcination. Ces propriétés étaient similaires aux échantillons TiO2 synthétisés en présence de BmimPF6; Tandis que les cristaux de TiO2 en présence de F ont montré une forme anisotrope pendant le murissement de la synthèse. Les évaluations de l'activité photocatalytique des photocatalyseurs ont ensuite été réalisées. Par rapport au TiO2 synthétisé sans additif et au TiO2 P25, les matériaux de TiO2 à faible teneur en P et F ("PANaF") ont présenté une activité plus élevée sous irradiation UVA à la dégradation d'un COV modèle, Méthyléthylcétone (MEK) en phase gazeuse. Le même matériau a également montré une activité anti-bactérienne en surface plus élevée sous UVA contre plusieurs souches de différentes espèces bactériennes dans liquide par rapport à celles de P25. Une corrélation entre la performance photocatalytique élevée et les propriétés des matériaux pour TiO2 "PANaF" a été finalement proposée. Les influences de la présence de PO43- en bulk ou en surface de TiO2, de la concentration d’O2 dissous dans le milieu et de la topologie de surface des photocatalyseurs sur l'activité photocatalytique éteint également sujets de discussion. Le produit "PANaF" présente un intérêt pour l'élaboration industrielle à cause des réactifs pas cher et son performance élevée. / The objective of this work consists in synthesizing TiO2 nanomaterials designed for the degradation of VOCs and for the elimination of bacteria on surface. Firstly, based on a synthesis of a BmimPF6-ionic liquid-derived TiO2 material through a modified sol-gel route, the roles of two constituent elements of BmimPF6 (P and F) have been investigated by replacing BmimPF6 with P- and F- contained additives. Comparing to the reference P25 and additive-free-derived TiO2 materials, P-derived TiO2 showed already well crystallized anatase phase before calcination and a high surface area along with a small mean crystal size even after calcinations. Those properties were similar to that synthesized with the presence of BmimPF6; while F-derived TiO2 crystals showed anisotropic shape during the aging step of the synthesis. Evaluation of the photocatalytic activity of the photocatalysts has been performed then. Compared to additive-free derived TiO2 and the TiO2 P25, P- and F- derived TiO2 materials with low P and F content (“PANaF”) showed higher activity under UVA in terms of gas-phase degradation of a model VOC, Methl Ethyl Ketone (MEK). The same material also showed higher surface anti-bacterial activity under UVA in liquid against several strains of different bacterial species over that of P25. A correlation between the high photocatalytic performances with the material properties for “PANaF” TiO2 materials was finally proposed. The influences of the presence of bulk or surface PO43-, dissolved O2 concentration and surface topology on photocatalytic activity were also discussed. The cheap replacement additives used and the resulted high activity of “PANaF” TiO2 nanomaterials presents interest for industrial elaboration.

NF1 ist eine autosomal dominante Erbkrankheit, die durch inaktivierende Mutationen im Neurofibromin-Gen verursacht wird. NF1 manifestiert sich durch eine erhöhte Tumor-Inzidenz des neuralen Gewebes in der Haut (Neurofibroma). Neben diesen häufigeren klinischen Manifestationen haben rund 50% der NF1-Patienten Skelett-Anomalien. Häufiger sind Röhrenknochen betroffen, die klinischen Symptome reichen von Tibia-Krümmung über Spontanfrakturen bis hin zu Nonunions. Diese Studie analysiert den Heilungsverlauf von Femurfrakturen in Nf1Prx1- Mäusen. Der Frakturkallus von Mäusen wurde an den Tagen 7, 10, 14 und 21 durch µCT, Histologie und molekulare Analysen evaluiert. µCT und histologische Analysen haben eine beeinträchtigte Knochenheilung in Nf1Prx1-Mäusen gezeigt. Eine erhöhte periostale Knochenbildung in den frühen Stadien der Heilung war zu beobachten, sowie eine reduzierte, aber anhaltende Knorpelbildung und Bindegewebs-Akkumulation innerhalb der Fraktur. Wir konnten zeigen, dass der normalen Heilungsprozess durch dieses Bindegewebe behindert wird, welches durch alpha smooth muscle actin-positive Myofibroblasten gebildet wird, die ihrerseits aus einer bisher noch nicht identifizierten Muskelfaszie abgeleitet sind. Dieser Zusammenhang wird durch eine Microarray-Analyse der Kallus-Gewebe bestätigt, die ergab, dass durch den Knock-Out Gene reguliert wurden, die in Physiologie, Proliferation und Differenzierung von Muskelzellen involviert sind. Darüber hinaus waren extrazelluläre-Matrix-Gene in den Mutanten hoch regeuliert. Zusammenfassend konnten wir zeigen, dass eine Ähnlichkeit des Heilungsverlauf zwischen dem Nf1Prx1-Mausmodell und NF1-Patienten besteht. Folglich kann an diesem Mausmodell untersucht werden, durch welche Mechanismen die Mutationen im NF1 zu Knochenheilungsstörungen führen. Außerdem konnte in einer Pilotstudie der Effekt des Neurofibromin-Mangels auf die Knochenheilung durch Behandlung mit MEK-Inhibitoren in vitro und in vivo weitestgehend behoben werden / Neurofibromatosis type 1 (NF1) is an autosomal dominant genetic disease resulting from inactivating mutations in the gene encoding the protein neurofibromin. NF1 patients – around 50% – have abnormalities of the skeleton. Long bones are often affected, and the clinical signs range from tibial bowing to spontaneous fractures and even non-unions. Moreover, NF1 mice models could provide the understanding of the cell types involved in the resulting non-union and their behavior. This study analyzed the healing progress of femur fractures in a model of NF1 long bone dysplasia. Fracture callus was assessed at days 7, 10, 14, and 21 by µCT, histology, biomechanics, and molecular analyses. Bone healing was impaired in Nf1Prx1 mice femoral fracture. Results revealed increased periosteal bone deposition at the early stages of healing, decreased but persistent cartilage formation concomitant with fibrous tissue accumulation within the fracture site, decreased torsional stiffness, decreased bone mineral density, and increased fibrous tissue infiltration in the callus of mutant mice. This fibrous tissue accumulation hindered bone fracture healing, and was deposited by alpha smooth muscle actin-positive myofibroblasts, which were derived from a yet unidentified muscle fascia. This is further supported by the microarray analysis of callus tissues showing that genes crucial to muscle cells physiology, proliferation and differentiation were affected. In addition, extracellular matrix related genes were up-regulated in the mutants. In summary, this study shows a resemblance in the healing progression to the Nf1Prx1 mice model and NF1 patients, thereby, confirming the suitability of this mice model to explore the mechanism by which mutations in NF1 lead to non-unions. Moreover, in vitro and in vivo pilot assessments of MEK inhibitor treatment demonstrated a potential remedy for the lack of neurofibromin in bone healing.

In the present study, we designed a new chemical template that contains an oxindole moiety as potential dual-pathway inhibitors of the Raf/MEK/ERK and PI3K/Akt signaling pathways. The design hypothesis is to evaluate whether the oxindole ring system will approximately orient functional groups in a similar manner to the thiazolidinedione moiety, and thus maintain biological activity as dual-pathway inhibitors of the Raf/MEK/ERK and PI3K/Akt signaling pathways. Furthermore, the oxindole ring will provide the flexibility to allow the introduction of various substituents on the oxindole moiety, thereby facilitating comprehensive SAR studies to further explore the biological activity.

Glucocorticoids (GC) are common components of many chemotherapeutic regimens for lymphoid malignancies. GC-induced apoptosis involves an intrinsic BCL-2 family-regulated pathway. It has been shown that BIM (BCL-2 interacting mediator of cell death), a BH3-only pro-apoptotic protein, is up-regulated by dexamethasone (Dex) treatment in acute lymphoblastic leukemia (ALL) cells. Furthermore, BIM is inactivated by extracellular signal-regulated kinase (ERK)-mediated phosphorylation. We therefore hypothesized co-treatment with Dex and MEK/ERK inhibitors would promote apoptosis in ALL cells through BIM up-regulation and activation. We show here that a MEK inhibitor, PD184352 synergistically enhances Dex lethality in CCRF-CEM (T-ALL) cells. Co-treatment with Dex and PD184352 results in BIM accumulation. Down-regulation of BIM by short-hairpin RNA in CCRF-CEM cells suppressed apoptosis by Dex/PD184352 co-treatment. In contrast, another BH3-only protein, BAD is dispensable. Thus, BIM is a critical molecule in this regimen, and targeting BIM by drugs combination could be effective on ALL and possibly other malignancies.