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<p dir="ltr">Cancer is the second leading cause of death worldwide, and there is a continued need for effective treatments to combat the disease. A key challenge in cancer therapy persists in the form of therapeutic resistance. While kinase inhibitors (KIs) have shown promise in treating cancer patients with dysregulated protein kinases, treatment failures are common, highlighting the urgent need to address this issue. Despite the approval of 80 protein kinase inhibitors by the United States Food and Drug Administration (FDA), and numerous others in clinical trials, the chemical space explored for protein kinase inhibitors remains limited. Most FDA-approved kinase inhibitors share common core moieties, such as indazole, quinoline, pyrazole, and pyrimidine, indicating a lack of diversification in drug development in this area.</p><p dir="ltr">Efforts to expand the chemical space have led to the identification of a novel 3<i>H</i>-pyrazolo-[4,3-<i>f</i>]quinoline core by the Sintim group. This scaffold can be efficiently synthesized through the Doebner–Povarov multicomponent reaction using readily available ketones, heteroaromatic aldehydes, and 5-aminoindazole. This multicomponent chemistry affords small molecules which inhibit disease-associated protein kinases with sub-nanomolar IC₅₀ values. Additionally, the scaffold presents a unique opportunity to tune for selectivity via judicious substitution patterns, allowing us to target numerous disease-driving kinases, such as FLT3, haspin, and CLK, with the use of simple multi-component chemistry.</p><p dir="ltr">From this work emerged lead amide-containing compound HSK205, which potently inhibits FLT3 and haspin and shows impressive potencies against FLT3-driven acute myeloid leukemia cell lines, with GI₅₀ values between 2 and 20 nM. Western blot analyses indicate that HSK205 inhibits the phosphorylation of FLT3 and histone H3 (substrate of haspin) in Molm-14 AML cells. Further exploration led to the discovery of lead CLK inhibitors, such as HSK1132 and HSK3110, which inhibit the growth of multiple myeloma cell lines <i>in vitro</i> with GI₅₀ values as low as 17 nM. Additionally, these compounds are orally bioavailable and reduce the growth of multiple myeloma RPMI-8226 xenograft model in mice by 69%.</p>

Dans les cas de lymphopénie, les lymphocytes T résiduels prolifèrent exagérément dans un phénomène appelé «expansion homéostatique périphérique» (HPE), qui est efficace pour la régénération des T CD8+, mais inefficace pour les T CD4+. L’interleukine-7 (IL7) est une cytokine homéostatique utilisée afin d’augmenter les comptes lymphocytaires T des patients lymphopéniques. Toutefois, la raison de l’expansion préférentielle des lymphocytes T CD8+ par l’IL7 demeure toujours inconnue. Nous montrons que cette expansion est due au fait que l’IL7 induit une prolifération efficace des T CD8+ périphériques (CD8+PERI) ainsi que des émigrants thymiques CD8+ (CD8+RTEs). Par contre, l’effet prolifératif de l’IL7 est restreint presqu’uniquement aux CD4+RTEs même si les CD4+PERI survivent mieux que les CD4+RTEs. De plus faibles doses d’IL7 sont nécessaires aux CD4+RTEs afin de phosphoryler STAT5 ou de proliférer comparativement aux CD4+PERI et nous démontrons que les contacts TCR/CMHII sont nécessaires à la prolifération induite par l’IL7 des CD4+RTEs en périphérie. De fait, augmenter au Flt3 ligand le nombre de cellules dendritiques périphériques d’une souris donneuse, avant de transférer ses TPERI dans des souris receveuses traitées à l’IL7 induit une prolifération significative des CD4+PERI. Nos résultats indiquent donc que l’abondance des contacts TCR/CMHII reçus dans le thymus semble contrôler la sensibilité à l’IL7 des CD4+RTEs. Finalement, l’observation que les CD8+PERI et CD8+RTEs prolifèrent pareillement pendant la thérapie à l’IL7, alors que la prolifération des T CD4+ est largement restreinte aux RTEs expliquerait pourquoi, dans les cas de lymphopénie, la régénération des T CD4+ est aussi dépendante de la thymopoïèse. / In lymphopenic settings, residual T lymphocytes typically undergo exaggerated proliferation via homeostatic peripheral expansion (HPE). While HPE efficiently regenerates CD8+ T cells, it is unable to normalize CD4+ T-cell counts. Interleukin-7 (IL7) is a homeostatic cytokine, currently used in trials in order to increase T-cell counts in lymphopenic humans. Nowadays, it is still not known why IL7 therapy is more effective toward the expansion of CD8+ T cells rather than CD4+ T cells. Here we show that CD8+ T cells preferential expansion is due to IL7-induced efficient proliferation of peripheral CD8+ T cells (CD8+PERI) and CD8+ recent thymic emigrants (CD8+RTEs). In contrast, the proliferative action of IL7 is largely restricted to CD4+RTEs although CD4+PERI survive better than CD4+RTEs. Interestingly, CD4+RTEs require lower concentrations of IL7 in order to phosphorylate STAT5 or proliferate when compared to CD4+PERI, and we demonstrate the requirement for TCR/MHCII contacts to support the IL7-induced HPE of CD4+RTEs in the periphery. Furthermore, augmenting the number of MHCII expressing cells in the periphery of donor mice by treating them with Flt3 ligand (Flt3L) prior transferring their TPERI cells in IL7 therapy-treated recipients, significantly enhances the IL7-induced proliferation of CD4+PERI. Our results indicate so far that the abundance of TCR triggering occurring inside the thymus drives IL7 responsiveness of CD4+RTEs. Moreover, the observation that CD8+PERI and CD8+RTE proliferate similarly during IL7 therapy, while proliferation of CD4+ T cells is largely restricted to RTEs, may explain why CD4+ T cells regeneration in lymphopenic settings is highly dependent on thymopoiesis.

Dans les cas de lymphopénie, les lymphocytes T résiduels prolifèrent exagérément dans un phénomène appelé «expansion homéostatique périphérique» (HPE), qui est efficace pour la régénération des T CD8+, mais inefficace pour les T CD4+. L’interleukine-7 (IL7) est une cytokine homéostatique utilisée afin d’augmenter les comptes lymphocytaires T des patients lymphopéniques. Toutefois, la raison de l’expansion préférentielle des lymphocytes T CD8+ par l’IL7 demeure toujours inconnue. Nous montrons que cette expansion est due au fait que l’IL7 induit une prolifération efficace des T CD8+ périphériques (CD8+PERI) ainsi que des émigrants thymiques CD8+ (CD8+RTEs). Par contre, l’effet prolifératif de l’IL7 est restreint presqu’uniquement aux CD4+RTEs même si les CD4+PERI survivent mieux que les CD4+RTEs. De plus faibles doses d’IL7 sont nécessaires aux CD4+RTEs afin de phosphoryler STAT5 ou de proliférer comparativement aux CD4+PERI et nous démontrons que les contacts TCR/CMHII sont nécessaires à la prolifération induite par l’IL7 des CD4+RTEs en périphérie. De fait, augmenter au Flt3 ligand le nombre de cellules dendritiques périphériques d’une souris donneuse, avant de transférer ses TPERI dans des souris receveuses traitées à l’IL7 induit une prolifération significative des CD4+PERI. Nos résultats indiquent donc que l’abondance des contacts TCR/CMHII reçus dans le thymus semble contrôler la sensibilité à l’IL7 des CD4+RTEs. Finalement, l’observation que les CD8+PERI et CD8+RTEs prolifèrent pareillement pendant la thérapie à l’IL7, alors que la prolifération des T CD4+ est largement restreinte aux RTEs expliquerait pourquoi, dans les cas de lymphopénie, la régénération des T CD4+ est aussi dépendante de la thymopoïèse. / In lymphopenic settings, residual T lymphocytes typically undergo exaggerated proliferation via homeostatic peripheral expansion (HPE). While HPE efficiently regenerates CD8+ T cells, it is unable to normalize CD4+ T-cell counts. Interleukin-7 (IL7) is a homeostatic cytokine, currently used in trials in order to increase T-cell counts in lymphopenic humans. Nowadays, it is still not known why IL7 therapy is more effective toward the expansion of CD8+ T cells rather than CD4+ T cells. Here we show that CD8+ T cells preferential expansion is due to IL7-induced efficient proliferation of peripheral CD8+ T cells (CD8+PERI) and CD8+ recent thymic emigrants (CD8+RTEs). In contrast, the proliferative action of IL7 is largely restricted to CD4+RTEs although CD4+PERI survive better than CD4+RTEs. Interestingly, CD4+RTEs require lower concentrations of IL7 in order to phosphorylate STAT5 or proliferate when compared to CD4+PERI, and we demonstrate the requirement for TCR/MHCII contacts to support the IL7-induced HPE of CD4+RTEs in the periphery. Furthermore, augmenting the number of MHCII expressing cells in the periphery of donor mice by treating them with Flt3 ligand (Flt3L) prior transferring their TPERI cells in IL7 therapy-treated recipients, significantly enhances the IL7-induced proliferation of CD4+PERI. Our results indicate so far that the abundance of TCR triggering occurring inside the thymus drives IL7 responsiveness of CD4+RTEs. Moreover, the observation that CD8+PERI and CD8+RTE proliferate similarly during IL7 therapy, while proliferation of CD4+ T cells is largely restricted to RTEs, may explain why CD4+ T cells regeneration in lymphopenic settings is highly dependent on thymopoiesis.

Les leucémies aigues myéloïdes (LAM) sont des hémopathies malignes de mauvais pronostic dont les thérapies actuelles ne permettent d’obtenir des taux de survie à 5 ans chez les adultes que d’environ 40%. Par conséquent, il est nécessaire d’approfondir nos connaissances concernant les mécanismes d’oncogenèse pour développer de nouvelles approches thérapeutiques. Malgré leur hétérogénéité clinique et biologique, les LAM ont certaines caractéristiques communes comme l’activation de la voie de signalisation mTORCl qui est détectée dans la plupart des échantillons de LAM. MTORCl contrôle la survie, la croissance et la prolifération cellulaire, notamment via le contrôle de la traduction des ARNm et donc de la synthèse protéique. Au cours de ce travail, nous montrons qu’il existe, dans les LAM, une dérégulation de mTORCl qui explique les limites des effets anti-leucémiques observés avec la rapamycine (un inhibiteur allostérique de mTORCl) et qui est médiée en partie par l’activité de la sérine thréonine kinase Pim2, qui contrôle la phosphorylation de la cible de mTORCl, la protéine 4E-BP1. Cependant, cibler directement la traduction produit des effets anti-leucémiques importants, ce que nous avons montré en utilisant une molécule inhibant spécifiquement le complexe d’initiation de la traduction, le 4EGI-l. EIF4E est essentiel à l’initiation de la traduction et nous avons montré sa surexpression au niveau protéique dans la plupart des échantillons de LAM au diagnostic par comparaison à des cellules hématopoïétiques normales CD34+. Bien que son niveau d’expression n’ait pas de valeur pronostique intrinsèque, ce résultat suggère un potentiel important au blocage de la traduction dans la plupart des cas de LAM. Dans la perspective d’inhiber mTORCl, nous avons activé la voie LKBl/AMPK par la metformine, ce qui a induit des effets anti-leucémiques in vitro et in vivo via une modification du métabolisme cellulaire avec en particulier une inhibition de la synthèse de protéines oncogéniques. La metformine n’étant pas un candidat en thérapeutique dans les LAM du fait d’un index thérapeutique trop étroit, de nouvelles molécules modulant la voie LKBl/AMPK sont en cours de développement. Enfin, nous avons étudié le rôle de la sérine thréonine kinase Pim2, qui contrôle la traduction protéique et la survie dans les cellules de LAM Flt3-ITD+. Nous avons de plus montré que la sur-expression de Pim2 constitue un nouveau mécanisme de résistance aux inhibiteurs de Flt3 et représente donc une cible thérapeutique prometteuse dans cette catégorie de LAM. L’étude de la voie mTORCl et de la traduction permet donc d’envisager de multiples perspectives thérapeutiques dans les LAM dont certaines sont déjà en cours de développement clinique. / Acute myeloid leukemia (AML) are hematological malignancies with adverse prognosis in which therapies only gives 40% survival within 5 years in adults. Hence, it is important to increase our knowledge regarding oncogenesis to further develop new therapeutic approaches. Despite their clinical and biological heterogeneity, AML have in common the constitutive activation of mTORC1 signaling which is detected in most AML samples. MTORC1 controls cell survival, growth and proliferation, in particular through control of mRNA translation and protein synthesis. During this work, we show, in AML, that mTORC1 is deregulated which explain the poor effects observed with rapamycin (a mTORC1 allosteric inhibitor) and is partially mediated by the serine/threonine kinase Pim-2 which controls the mTORC1 target 4E-BP1. Nevertheless, directly targeting translation, using a specific translation initiation inhibitor named 4EGI-1, have important anti leukemic effects. EIF4E is described as essential in translation initiation and we show its protein overexpression in most AML samples at diagnosis compared with normal hematopoietic CD34+ cells. Whereas eIF4E level expression has no prognostic impact, this result suggests an important potential for treatment targeting translation initiation in AML. In our purpose of inhibiting mTORC1, we were able to activate LKB1/AMPK signaling pathway with metformin, which induces anti leukemic effects in vitro and in vivo through in particular oncogenic protein translation inhibition. Metformin is not a good AML therapeutic candidate because of a narrow therapeutic index, new compound targeting LKB1/AMPK are in development. Finally, we studied the role of the serine/threonine kinase Pim-2 and show that it controls protein translation and FLT3-ITD+ AML cells survival. Furthermore, we show that Pim-2 overexpression is a new mechanism of Flt3 inhibitors resistance and represent a new promising therapeutic target in this AML subtype. Overall, mTORC1 and protein translation study in AML show multiple therapeutics perspective, some of them are already in clinical development.

The hematopoietic stem cell (HSC) is characterized by its ability to self-renew and produce all mature blood cells throughout the life of an organism. This is tightly regulated to maintain a balance between survival, proliferation, and differentiation. The HSCs are located in specialized niches in the bone marrow thought to be low in oxygen, which is suggested to be involved in the regulation of HSC maintenance, proliferation, and migration. However, the importance of hypoxia in the stem cell niche and the molecular mechanisms involved remain fairly undefined. Another important regulator of human HSCs maintenance is the tyrosine kinase receptor FLT3, which triggers survival of HSCs and progenitor cells. Mutations in FLT3 cause constitutively active signaling. This leads to uncontrolled survival and proliferation, which can result in development of acute myeloid leukemia (AML). One of the purposes with this thesis is to investigate how survival, proliferation and self-renewal in normal HSCs are affected by hypoxia. To study this, we used both in vitro and in vivo models with isolated Lineage-Sca-1+Kit+ (LSK) and CD34-Flt3-LSK cells from mouse bone marrow. We found that hypoxia maintained an immature phenotype. In addition, hypoxia decreased proliferation and induced cell cycle arrest, which is the signature of HSCs with long term multipotential capacity. A dormant state of HSCs is suggested to be critical for protecting and preventing depletion of the stem cell pool. Furthermore, we observed that hypoxia rescues HSCs from oxidative stress-induced cell death, implicating that hypoxia is important in the bone marrow niche to limit reactive oxidative species (ROS) production and give life-long protection of HSCs. Another focus in this thesis is to investigate downstream pathways involved in tyrosine kinase inhibitor-induced cell death of primary AML cells and cell lines expressing mutated FLT3. Our results demonstrate an important role of the PI3K/AKT pathway to mediate survival signals from FLT3. We found FoxO3a and its target gene Bim to be key players of apoptosis in cells carrying oncogenic FLT3 after treatment with tyrosine kinase inhibitors. In conclusion, this thesis highlights hypoxic-mediated regulation of normal HSCs maintenance and critical effectors of apoptosis in leukemic cells expressing mutated FLT3. / <p>On the day of the defence date the title of article II was "Hypoxia, via hypoxia-inducible factor (HIF)-1, mediates low cell cycle activity and preserves the engraftment potential of mouse hematopoietic stem cells" and one of the authors is no longer included in the article.</p>

Dendritic cells (DC) are antigen-presenting cells that are critical for the initiation and regulation of the immune response. Several DC subtypes within mouse spleen have previously been characterised and these include the plasmacytoid (pDC), and conventional DC (cDC) of the CD8+ and CD8- subtypes. Each subtype appears to have a specialised role in the various arms of immunity and tolerance. Less clear is the process by which these DC develop from haematopoietic precursors, of the precursor stages and branch points from bone marrow (BM) stem cells to each of the peripheral DC subtypes. The research described herein had the aim of identifying and isolating some of the intermediate precursors of DC, downstream of stem cells, and determining whether these differed in the steady-state versus inflammation. Particular was given to DC of the spleen. Experiments that sought the identity of such precursors involved both i) transfer of cell fractions that contained DC precursors into steady-state or inflamed recipient mice to assess their in vivo development at later times, and ii) analysis of an in vitro culture system to question whether it reflected development of the steady-state DC subtypes.

Les cellules dendritiques sont des cellules du système immunitaire inné qui jouent un rôle important dans la reconnaissance immunitaire contre les agents pathogènes étrangers. Elles peuvent également prévenir les maladies auto-immunes à l'état basal. En raison de l'importance des cellules dendritiques dans la régulation immunitaire, il est important de comprendre comment le développement, l'état d'homéostasie et de quiescence des ces cellules sont contrôlées dans des conditions physiologiques et pathologiques. Cette étude permettra non seulement de mieux comprendre le contrôle de la régulation immunitaire, mais aussi de contribuer au développement de nouvelles approches pour traiter les maladies infectieuses et auto-immunes, ainsi que les cancers. Notre laboratoire a montré que C-CBL et CBL-B, deux membres de la famille CBL des ubiquitine ligases E3, jouent un rôle redondant dans la régulation négative du développement et de l'activation des cellules T et B. En l'absence de CBL dans les cellules T ou B, les souris développent des maladies auto-immunes sévères, indiquant que C-CBL et CBL-B jouent un rôle dans le système auto-immun. Partant de ces observations, nous proposons que CBL-B et C-CBL peuvent également jouer un rôle similaire dans le développement et la fonction des cellules dendritiques. Pour étudier cette possibilité, nous avons généré une souris knockout de Cbl spécifiques aux cellules dendritiques (dKO). Nous avons trouvé que cette mutation provoque une modification de l'homéostasie d'un sous-ensemble des cellules dendritiques (DC), y compris une augmentation marquée des CD8a+ cDCs et une réduction des pDC dans la rate. Cette modification est causée par la prolifération accrue des CD8a+ cDCs. Dans les CD8a+ cDCs mutantes, les voies de signalisation PKB et ERK sont constitutivement activées. Blocage de la signalisation de MTOR par la rapamycine atténue de manière significative l'hyperprolifération des CD8a+ cDCs in vitro et in vivo, indiquant que l'hyperactivation de MTOR est en partie responsable de l'augmentation CD8a+ cDCs. Les protéines CBL contrôlent l'ubiquitination et la dégradation du récepteur FLT3, suggérant que les protéines CBL contrôlent ainsi l'homéostasie de CD8a+ cDCs. Outre ces effets sur le développement des cellules dendritiques, nous avons trouvé que les souris Cbl dKO développent des inflammations sévères du foie et d'autres organes, caractérisées par une infiltration massive de leucocytes et une activation importante des cellules lymphocytes T périphériques. Les souris mutantes produisent des niveaux élevés de cytokines inflammatoires et de chimiokines, telles que le TNF-α, l'IL-6 et le CCL2. Les souris mutantes développent une maladie inflammatoire du foie. L'ensemble de ces observations montrent que les protéines CBL jouent un rôle essentiel dans le maintien de la quiescence immunitaire chez la souris. Puisque les souris dKO Cbl développent principalement une inflammation sévère du foie, il serait intéressant d'étudier si les voies contrôlées par les protéines CBL contribuent également au développement d'une inflammation du foie chez l'homme. / Dendritic cells (DCs) are innate immune cells that play an important role in immune recognition against foreign pathogens. They may also sense self-cues and prevent autoimmune diseases under the steady-state. Given the importance of DCs in immune regulation, it is conceivable that understanding how DCs development, homeostasis and functional quiescence are regulated under physiological and pathological conditions will not only bring insight into our knowledge how immune regulation is controlled but also some new approaches to treat infectious and autoimmune diseases and even cancers. Dr. Gu’s lab previously has shown that C-CBL and CBL-B, two members of the CBL family of E3 ubiquitin ligases, play a redundant negative regulatory role in both T cells and B cells development and activation. In the absence of CBL family of proteins in either T or B cells, mice develop severe autoimmune diseases, indicating that C-CBL and CBL-B restrain immune system against self. Based on these discoveries, we propose that C-CBL and CBL-B may also have a similar regulatory role in DC development and function. To study this possibility, we have generated DC-specific Cbl dKO mice. We have found that the Cbl dKO mutation results in an altered homeostasis of DC subsets, including a marked increase of CD8a+ cDCs and reduction of pDCs in the spleen (SP). This alteration is due to the enhanced proliferation of CD8a+ cDCs rather than the preferential lineage commitment to CD8a+ cDCs. In the mutant CD8a+ cDCs, both the PKB signaling pathway and ERK signaling pathways are constitutively activated. Blockage of MTOR signaling by Rapamycin significantly attenuates the hyperproliferation of CD8a+ cDCs both in vitro and in vivo, indicating that hyperactivation of MTOR is at least one of the reasons leading to CD8a+ cDC expansion. CBL proteins regulate ubiquitination and degradation of FLT3. Based on these results, we conclude that CBL proteins control CD8a+ cDC homeostasis through promoting FLT3 ubiquitination and degradation. In addition to the altered DC development, we have found that Cbl dKO mice develop severe liver and other organ inflammation characterized by massive leukocytes infiltration and profound peripheral T cell activation. Mutant mice produce high levels of inflammatory cytokines and chemokines including TNF-a, IL-6, CCL2, etc. Most strikingly, the mutant mice develop a similar liver inflammatory disease even in the absence of T and B cells. These findings together indicate that CBL proteins play an essential role in the maintenance of immune quiescence in mice. Since Cbl dKO mice mainly develop severe liver inflammation, it will be interesting to study whether the pathways controlled by CBL proteins also contribute to the development of liver inflammation in humans.

La protéine de fusion E2A-PBX1 induit une leucémie lymphoblastique aigüe des cellules B pédiatrique chez l’humain. E2A-PBX1 possède de puissantes propriétés de trans-activation et peut se lier à l’ADN ainsi qu’aux protéines homéotiques (HOX) via des domaines conservés dans sa portion PBX1, ce qui suggère qu’une dérégulation des gènes cibles de HOX/PBX1 contribue à la leucémogénèse. Précédemment, Bijl et al. (2008) ont démontré que certains gènes Hox collaborent de manière oncogénique avec E2A-PBX1, et que ces interactions sont cellules-spécifiques et varient en fonction du gène Hox impliqué. Une mutagénèse d’insertion provirale suggère et supporte la collaboration des gènes Hoxa et E2A-PBX1 lors de la leucémogénèse des cellules B. La présence de ces interactions dans les cellules B et leur implication dans l’induction des B-ALL est pertinente pour la compréhension de la maladie humaine, et reste encore mal comprise. Notre étude démontre qu’Hoxa9 confère un avantage prolifératif aux cellules B E2A-PBX1. Des expériences de transplantation à l’aide de cellules B E2A-PBX1/Hoxa9 positives isolées de chimères de moelle osseuse démontrent qu’Hoxa9 collabore avec E2A-PBX1 en contribuant à la transformation oncogénique des cellules, et qu’Hoxa9 seul n’induit aucune transformation. Une analyse par Q-RT-PCR nous a permis de démontrer une forte inhibition de gènes spécifiques aux cellules B dans les leucémies co-exprimant Hoxa9 et E2A-PBX1, en plus d’une activation de Flt3, suggérant une inhibition de la différenciation des cellules B accompagnée d’une augmentation de la prolifération. De plus, la surexpression de Hoxa9 dans des cellules leucémiques de souris transgéniques E2A-PBX1, confère aussi un avantage prolifératif aux cellules in vitro, qui semblent être influencé par une augmentation de l’expression de Flt3 et Pdgfδ. En conclusion, nous démontrons pour la première fois à l’aide d’un modèle murin qu’Hoxa9 collabore avec E2A-PBX1 lors de la transformation oncogénique des cellules B et que la signalisation via Flt3 est impliquée, ce qui est potentiellement pertinent pour la maladie humaine. / The fusion protein E2A-PBX1 induces pediatric B cell leukemia in human. It has strong transactivating properties and can bind to DNA and homeobox (HOX) proteins through conserved domains in the PBX1 portion, suggesting that deregulation of HOX/PBX target genes contribute to leukemogenesis. Previously, we reported oncogenic interactions between Hox genes and E2A-PBX1, which are dependent on cell type as well as on the particular Hox member. A proviral insertional mutagenesis screen provided support for collaboration between Hoxa genes and E2A-PBX1 in B cell leukemogenesis. Whether these interactions occur in B cells and lead to B-ALL, relevant for human disease is still not clear. Here we report that Hoxa9 confers a proliferative advantage to E2A-PBX1 B cells. Transplantation experiments with E2APBX1/Hoxa9 positive B cells isolated from bone marrow (BM) chimeras showed that Hoxa9 interacts with E2A-PBX1 contributing to the oncogenic transformation of B cells, but is unable to transform B cells alone. Q-RT-PCR analysis demonstrated a strong repression of B cell specific genes in leukemias co-overexpressing Hoxa9 and E2A-PBX1 in addition to Flt3 activation, indicating inhibition of B cell differentiation in combination with enhanced proliferation. Overexpression of Hoxa9 in E2A-PBX1 mouse leukemic B cells also resulted in a growth advantage in vitro, likely mediated by the enhanced expression of Flt3 and Pdgfδ. In conclusion we show for the first time that Hoxa9 collaborates with E2A-PBX1 in the oncogenic transformation of B cells in a mouse model that involves Flt3 signaling, which is potentially relevant to human disease.

Submitted by Amanda Silva (amanda.osilva2@ufpe.br) on 2015-03-13T15:29:17Z No. of bitstreams: 2 TESE Bethânia de Araújo Amaral.pdf: 4449052 bytes, checksum: f014da1c40afd7489d798e17efed3d13 (MD5) license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) / Made available in DSpace on 2015-03-13T15:29:17Z (GMT). No. of bitstreams: 2 TESE Bethânia de Araújo Amaral.pdf: 4449052 bytes, checksum: f014da1c40afd7489d798e17efed3d13 (MD5) license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Previous issue date: 2014 / UFPE; CAPES; FACEPE / A leucemia promielocítica aguda (LPA) requer uma atenção especial dentre as leucemias mielóides agudas devido às suas implicações prognósticas e terapêuticas. A taxa de sobrevida de no mínimo cinco anos na LPA chega a 80% dos pacientes com a terapia atual e a taxa de cura excede os 70%. No entanto, a real situação dos resultados do tratamento da LPA em países em desenvolvimento, como o Brasil, é desconhecida. Este trabalho visou contribuir na investigação dos casos de LPA infantil em pacientes na nossa população objetivando a identificação de marcadores que possam redirecionar o acompanhamento e tratamento destes pacientes. A investigação da ocorrência de mutações dos genes FLT3 e NPM1 é importante na determinação prognostica das LMAs, contribuindo para a estratificação de grupos de maior ou menor risco e auxiliando o direcionamento do tratamento. Dezesseis pacientes pediátricos com LPA, representando 29,09% dos casos de LMA infantil, foram atendidos no CEONHPE/HUOC/UPE de 2004 a 2013. A idade variou de 5 a 17 anos (média de 11,81 anos). Análises citogenética e molecular por FISH e RT-PCR foram realizadas para confirmação do diagnóstico genético, na identificação do rearranjo PML-RARα decorrente da t(15;17), além da pesquisa das mutações dos genes FLT3 e NPM1. A análise cariotípica com o bandeamento G revelou alterações cromossômicas em 10 pacientes. Três apresentaram cariótipos complexos com presença de cromossomos marcadores. A técnica de FISH para a t(15;17) confirmou o rearranjo em 14 pacientes. Divergência entre as análises moleculares foram observadas em cinco pacientes, sendo positiva a detecção da t(15;17) pela FISH e negativa pela RT-PCR. A mutação do FLT3/ITD foi detectada em dois pacientes (12,5%), enquanto a mutação FLT3/TKD foi detectada em apenas um paciente (6,25%). A pesquisa para a mutação no gene NPM1 foi negativa para todos os casos. Quanto ao status oito pacientes encontramse vivos ou na fase de manutenção do tratamento e oito foram a óbito, sendo que destes sete tiveram óbitos precoces ainda na fase de indução. Os motivos primários dos óbitos foram hemorragias, septicemia e manifestação da síndrome do ATRA. Este dado é alarmante uma vez que estas mortes são difíceis de prevenir e assinalam o alto risco de ocorrência destes eventos em nossa população. Destacamos a importância do uso de técnicas citogenéticas moleculares na confirmação genética do diagnóstico da LPA e a necessidade de uma melhor adaptação do regime terapêutico aos casos de LPA na infância em nossa população.