Le corps humain est composé de plus de 100 000 protéines qui interagissent entre elles afin d’assurer son bon fonctionnement. Néanmoins, il peut arriver que certaines de ces protéines subissent une mutation changeant l’équilibre de fonctions du corps telles que la réplication cellulaire. Ces mutations affectant la réplication cellulaire peuvent mener à des cancers, une maladie qui touche de plus en plus de gens à travers le monde. Afin de développer des médicaments efficaces contre cette maladie, il est nécessaire de bien comprendre les mécanismes biologiques impliqués pour établir une approche thérapeutique. Cette compréhension repose notamment sur l’utilisation d’outils moléculaires, de petites molécules possédant des fonctions chimiques versatiles pouvant donner des informations critiques dans le développement de médicaments. Ce présent mémoire se consacre sur le développement d’outils moléculaires à travers deux projets ayant des objectifs distincts. Le premier projet avait comme principal objectif d’approfondir les connaissances sur l’inhibition de la protéine RAS, une GTPase responsable de plus de 30% des cancers. À cet effet, l’approche privilégiée a été celle de la synthèse de macrocycles peptidiques se liant à la cystéine 118 de RAS d’après la structure du monobody NS1. Les structures cristallines et les données protéomiques obtenues ont permis d’identifier les interactions clés entre la protéine RAS et une série d’inhibiteurs cherchant à émuler les effets biologiques de NS1. Le second projet s’intéresse quant à lui aux effets du composé UM171 sur les cellules souches. En effet, cette petite molécule possède la capacité d’empêcher la différenciation des cellules souches hématopoïétiques et permet donc leur multiplication. Cette propriété est une source d’espoir dans le traitement des leucémies et des transplantions. Cependant, la cible biologique de ce composé reste un mystère à ce jour. Ainsi la seconde partie de ce mémoire mettra de l’avant la synthèse d’outils moléculaire à base de diazirines pour tenter de venir identifier la cible d’intérêt en utilisant la protéomique. / The human body is made up of more than 100 000 proteins which interact with each other to keep it functioning properly. However, it can happen that some of these proteins undergo a mutation which changes the balance of body functions such as cell proliferation. These mutations affecting cell proliferation can lead to cancer, a disease that is affecting more and more people around the world. To develop effective drugs against this disease, it is necessary to understand the biological mechanisms involved in order to establish a therapeutic approach. This understanding is particularly based on the use of molecular tools, small molecules with versatile chemical functions that can provide critical information for drug development. This thesis is devoted to the development of molecular tools through two projects with distinct objectives. The main objective of the first project was to deepen knowledge about the inhibition of the RAS protein, a GTPase responsible for more than 30% of cancers. To this end, the preferred approach has been the synthesis of peptide macrocycles binding to RAS cysteine 118 based on the structure of NS1 monobody. The crystal structures and proteomic data obtained have made it possible to identify key interactions between the RAS protein and a series of inhibitors seeking to emulate the biological effects of NS1. The second project focuses on the effects of compound UM171 on stem cells. Indeed, this small molecule can prevent the differentiation of hematopoietic stem cells and therefore allows their multiplication. This property is a source of hope in the treatment of leukemia and transplants. However, the biological target of this compound remains a mystery to this day. Thus, the second part of this thesis will focus on the synthesis of molecular tools based on diazirines in an attempt to identify the target of interest using proteomics.

Indiana University-Purdue University Indianapolis (IUPUI) / Internal tandem duplications in FMS-like receptor tyrosine kinase (FLT3-ITDs) are seen in approximately 25% of all acute myeloid leukemia (AML) patients. FLT3-ITDs induce FLT3 ligand (FL)-independent cellular hyperproliferation, promiscuous and aberrant activation of STAT5, and confer a poor prognosis in patients; however, the molecular mechanisms contributing to FLT3-ITD-induced malignancy remain largely unknown. The protein tyrosine phosphatase, Shp2, is important for normal hematopoiesis as well as hematopoietic stem cell (HSC) differentiation, engraftment, and self-renewal. Furthermore, FLT3-ITD- or constitutive active STAT5-expressing CD34+ cells demonstrate enhanced hematopoietic stem cell self-renewal. Together with the previous findings that Shp2 is critical for normal hematopoiesis, that dysregulated Shp2 function contributes to myeloid malignancies, and that Shp2 has been shown to interact with WT-FLT3 tyrosine 599, which is commonly duplicated in FLT3-ITDs, a positive role for Shp2 in FLT3-ITD-induced signaling and leukemogenesis is implied. I demonstrated that Shp2 is constitutively associated with the reported FLT3-ITDs, N51-FLT3 and N73-FLT3, compared to WT-FLT3; therefore, I hypothesized that increased Shp2 recruitment to N51-FLT3 or N73-FLT3 contributes to hyperproliferation and hyperactivation of STAT5. I also hypothesized that Shp2 cooperates with STAT5 to activate STAT5 transcriptional targets contributing to the up-regulation of pro-leukemic proteins. Finally, I hypothesized that reduction of Shp2 would result in diminished N51-FLT3-induced hyperproliferation and activation of STAT5 in vitro, and prevent FLT3-ITD-induced malignancy in vivo. I found that genetic disruption of Ptpn11, the gene encoding Shp2, or pharmacologic inhibition of Shp2 with the novel Shp2 inhibitor, II-B08, resulted in significantly reduced FLT3-ITD-induced hematopoietic cell hyperproliferation and STAT5 hyperphosphorylation. I also demonstrated a novel role of Shp2 in the nucleus of FLT3-ITD-expressing hematopoietic cells where Shp2 and STAT5 co-localized at the promoter region of STAT5-transcriptional target and pro-survival protein, Bcl-XL. Furthermore, using a Shp2flox/flox;Mx1Cre+ mouse model, I demonstrated that reduced Shp2 expression in hematopoietic cells resulted in an increased latency to and reduced severity of FLT3-ITD-induced malignancy. Collectively, these findings demonstrate that Shp2 plays an integral role in FLT3-ITD-induced malignancy and suggest that targeting Shp2 may be a future therapeutic option for treating FLT3-ITD-positive AML patients.

Animal models have greatly contributed to the understanding of different aspects of human biology, as well as a variety of human-related pathogens and diseases. In order to study them, humanized mice susceptible to pathogens that replicate in human immune cells have been developed (e.g., humanized Rag2-/-γc-/- mice). These animals are engrafted with human hematopoietic stem cells (HSCs), resulting in the de novo development and maturation of the major functional components of the human adaptive immune system and the production of a variety of human cell types. Primary and secondary lymphoid organs in the mouse are populated with human cells, and animals have long term engraftment. These features make humanized mice an excellent in vivo model to study pathogenesis of human-specific viruses in the context of a human antiviral immune response. In addition, humanized mice have been shown to be useful preclinical models for the development and validation of antiviral therapeutics. In the present study, we aimed to successfully re-establish the humanized Rag2-/-γc-/- mouse model using cord blood-derived HSCs in our laboratory. We have shown that these mice sustain long term engraftment and systemic expansion of human cells, including the major targets of Kaposi's sarcoma Herpesvirus (KSHV) and Human immunodeficiency virus type 1 (HIV-1), in peripheral blood and different lymphoid organs. Further, we have begun to evaluate the susceptibility of the humanized Rag2-/-γc-/- mouse model to infection with KSHV. We demonstrate that human lymphocytes differentiated in reconstituted Rag2-/-γc-/- mice are permissive to KSHV infection ex vivo. This finding was corroborated by detection of KSHV mRNA expression in the spleen of a humanized mouse at 6 months post infection. In a different study, we tested the in vivo antiviral efficacy of a novel HIV-1 fusion inhibitor (PIE-12-trimer) in humanized Rag2-/-γc-/- mice. We have determined the half life of PIE-12-trimer in mouse plasma. Furthermore, the administration of PIE-12-trimer to HIV-1 infected humanized Rag2-/-γc-/- mice prevents depletion of CD4+ T cells in blood, thus it may be useful to prevent AIDS in human patients.

<p dir="ltr">Hematopoietic stem cells (HSCs) originating from aorta-gonad-mesonephros (AGM) could self-renew and develop into various immune cells, such as T cells, neutrophil and natural killer (NK) cells, rendering them as a promising cell source for immunotherapy. NK cells belong to the family of the innate lymphoid cells, and are employed as one of immunotherapy to cure solid and hematological malignancies including leukemia. Neutrophils are one of the granulocytes, and they are emerging as a new therapeutic target in various cancers. Due to the lack of reliable sources for the amounts of HSCs and immune cells required for clinical infusions (~10⁹ cells/patient), it remains as a major challenge to realize their full potential in targeted cell and immunotherapy. While substantial efforts have been made to generate native cell-like HSPCs and immune cells from human pluripotent stem cells (hPSCs), intricate molecular process governing the differentiation of HSCs and immune cells remain elusive, preventing the development of robust strategies for HSC and immune cell productions.</p><p dir="ltr">In this study, we first demonstrated that critical role of temporally regulating Wnt signaling in initiating AGM-like hematopoiesis across 11 hPSC lines. By inhibiting TGFβ at the stage of aorta-like CD34+SOX17⁺ hemogenic endothelium, which led to the downregulation of Wnt signaling, we established a chemically defined, feeder-free culture system that efficiently produced robust AGM-like hematopoietic cells. Furthermore, we investigated how hypoxia affects the <i>in vitro</i> hPSC differentiation into HSPCs, which resulted in a hypoxia-enhanced HSPC differentiation platform.</p><p dir="ltr">Next, the temporal roles of transcription factors (TFs), including <i>NFIL3</i>, <i>ID2</i>,<i> </i>and <i>SPI1</i>, in regulating and promoting NK cell differentiation from hPSCs are determined. <i>NFIL3</i> and <i>SPI1</i> have been reported to influence the early stages of NK cell development, while <i>ID2</i> has an impact on the generation of NK cells throughout the early and intermediate stage. We genetically modified hPSCs with doxycycline-inducible expression of <i>NFIL3</i>, <i>ID2</i>,<i> </i>and <i>SPI1</i>, and investigated their roles in NK cell induction from hPSCs. Among these three TFs, forced expression of <i>ID2</i> yielded the highest percentage of NK cells under a chemically defined, feeder-free monolayer culture condition, demonstrating that forced expression of NK-specific TFs improves the efficiency of NK cell differentiation from hPSCs.</p><p dir="ltr">Chimeric antigen receptor (CAR) is an artificial cell receptor expressed on immune T or NK cells that has been engineered to allow T or NK cells to re-target cancer cells by exclusively binding to a cancer-specific protein. CAR engineering has significantly improved the anti-tumor efficacy of NK cell therapy, resulting in 6 FDA-approved CAR-T therapies and many other ongoing clinical trials. Recently, a chlorotoxin (CLTX)-based CAR was developed and shown to specifically bind to a variety of heterogenous glioblastoma (GBM) cell lines. To test whether CLTX-CAR could improve the anti-tumor cytotoxicity of hPSC-derived NK cells, hPSCs were engineered with CLTX-CAR for stable and homogenous CAR expression via Cas9-mediated homologous recombination. The expression of CLTX-CAR did not affect the pluripotency and NK cell differentiation potential of hPSCs, and CLTX-CAR significantly improved the cytotoxicity of hPSC-derived NK cells against GBM cells.</p><p dir="ltr">Finally, we implemented a GBM-on-a-chip microfluidic model to interrogate the tumor microenvironment (TME). Microfluidics are an emerging device for investigating cancer biology with spatiotemporal control over signaling modulators by using a small volume. The interaction between hPSC-drived neutrophils and GBM was explored in this microfluidic device. GBM TME is very complex and involves many cell types, including neurons, microglia, immune T and NK cells. In the future, microfluidic models with isogenic cell components will be designed and implemented to better model GBM TME.</p><p dir="ltr">In summary, these discoveries confirm the pivotal role of Wnt signaling in guiding hPSCs towards hematopoietic lineages, while also highlighting <i>ID2</i> as a potent enhancer of NK cell differentiation from hPSC-derived hematopoietic progenitor cells. Additionally, CAR engineering enhances the anti-tumor capabilities of hPSC-derived NK cells. Furthermore, microfluidic models are employed to interrogate GBM TME.</p>

[ES] Los síndromes mielodisplásicos (SMD) constituyen un grupo heterogéneo de enfermedades de naturaleza clonal caracterizadas por presentar una hematopoyesis ineficaz, citopenias y riesgo variable de evolución a leucemia mieloide aguda (LMA) secundaria. En la última década, las nuevas tecnologías de secuenciación masiva han revelado que más del 80 % de pacientes con SMD presenta mutaciones somáticas y que éstas pueden agruparse en diversas categorías en función de las rutas biológicas que se vean alteradas. Además, se ha visto que existen patrones de concurrencia y exclusión entre estas categorías de mutaciones. La adquisición secuencial y la concurrencia entre estas mutaciones desencadenan, en parte, el desarrollo de la enfermedad y genera la heterogeneidad clínica característica de los SMD. Las mutaciones en factores de splicing aparecen a menudo simultáneamente con mutaciones en reguladores epigenéticos como es el caso de los genes U2 Small Nuclear RNA Auxiliary Factor 1 (U2AF1) y Ten-eleven translocation 2 (TET2) que se encuentran co-mutados en un 13 % de los casos. A pesar de su prevalencia, los efectos de la concurrencia en las mutaciones en U2AF1 y TET2 no han sido estudiados. Por ello, en esta tesis nos propusimos estudiar esta cooperación cruzando, en primer lugar, dos líneas mutantes de ratón generadas mediante el sistema de edición genética CRISPR/Cas9. El efecto de estas alteraciones sobre la hematopoyesis de las tres líneas mutantes, U2af1mut/+, Tet2-/- y U2af1mut/+ Tet2-/-, fue examinado mediante el hemograma, citometría de flujo (CF), análisis morfológicos, ensayos de Unidades Formadoras de Colonias (CFU) y estudios funcionales como el trasplante hematopoyético. Para finalizar, se realizó un análisis transcriptómico mediante secuenciación de ARN (ARN-seq) para detectar los posibles cambios en el patrón de splicing entre las líneas mutantes y los controles. La línea mutante U2af1mut/+ no presentó ninguna alteración destacable de la hematopoyesis ni en ratones jóvenes (12-13 semanas) ni envejecidos (2 años). Sin embargo, sus células madre y progenitoras hematopoyéticas (HSPC) fueron incapaces de injertar en la médula ósea de ratones trasplantados. En el caso de los ratones mutantes Tet2-/-, observamos un incremento de células mieloides, esplenomegalia, aumento del compartimento LSK (HSPC con inmunofenotipo Linaje- Sca-1+ c-kit+) y, en los experimentos de trasplante, una capacidad de reconstitución hematopoyética superior a la de los controles. Por último, la cooperación de ambas alteraciones en la línea doble mutante U2af1mut/+ Tet2-/-, no mostró un efecto sinérgico entre ellas. Así pues, se detectaron variaciones en los progenitores mieloeritroides y un aumento significativo de células mieloides y LSK. No obstante, igual que ocurría con la línea U2af1mut/+, las HSPC no producían prendimiento en los ratones trasplantados. A pesar de las alteraciones observadas, ninguna de las tres líneas mutantes desarrollaba SMD ni fallecía antes que los controles. Respecto al análisis transcriptómico, el salto de exón fue el evento de splicing alternativo observado con mayor frecuencia en las líneas U2af1mut/+, Tet2-/- y U2af1mut/+ Tet2-/-. Únicamente un 6.6 % del total de genes que presentaba eventos de splicing alternativo fueron coincidentes en las tres líneas mutantes. A pesar de que en el análisis bioinformático se detectaron alteraciones en las rutas biológicas relacionadas con el ciclo celular, en los ratones U2af1mut/+, y el daño al ADN, en las líneas U2af1mut/+ y U2af1mut/+ Tet2-/-, en la validación mediante CF no se encontraron variaciones respecto a los controles. Para concluir, nuestros datos sugieren que, a pesar de producirse alteraciones en la hematopoyesis, la cooperación entre la mutación en U2af1 y la pérdida de Tet2 es insuficiente para iniciar SMD en ratón. / [CA] Les síndromes mielodisplàstiques (SMD) constituïxen un grup heterogeni de malalties de naturalesa clonal caracteritzades per presentar una hematopoesi ineficaç, citopènies i risc variable d'evolució a leucèmia mieloide aguda (LMA) secundària. En l'última dècada, les noves tecnologies de seqüenciació massiva han revelat que més del 80 % de pacients amb SMD presenta mutacions somàtiques i que aquestes poden agrupar-se en diverses categories en funció de les rutes biològiques que es vegen alterades. A més, s'ha vist que hi ha patrons de concurrència i exclusió entre aquestes categories de mutacions. L'adquisició seqüencial i la concurrència entre aquestes mutacions desencadenen, en part, el desenvolupament de la malaltia i genera l'heterogeneïtat clínica característica de les SMD. Les mutacions en factors de splicing apareixen sovint simultàniament amb mutacions en reguladors epigenètics com és el cas dels gens U2 Small Nuclear RNA Auxiliary Factor 1 (U2AF1) i Ten-eleven translocation 2 (TET2) que es troben co-mutats en un 13 % dels casos. A pesar de la seua prevalença, els efectes de la concurrència en les mutacions en U2AF1 i TET2 no han sigut estudiats. Per això, en aquesta tesi ens vam proposar estudiar aquesta cooperació creuant, en primer lloc, dos línies mutants de ratolí generades per mitjà del sistema d'edició genètica CRISPR/Cas9. L'efecte d'aquestes alteracions sobre l'hematopoesi de les tres línies mutants, U2af1mut/+, Tet2-/- i U2af1mut/+ Tet2-/-, va ser examinat per mitjà de l'hemograma, citometría de flux (CF), anàlisis morfològiques, assajos d'Unitats Formadores de Colònies (CFU) i estudis funcionals com el trasplantament hematopoètic. Per últim, es va realitzar l'anàlisi transcriptòmic per mitjà de seqüenciació d'ARN (ARN-seq) per a detectar els possibles canvis en el patró de splicing entre les línies mutants i els controls. La línia mutant U2af1mut/+ no va presentar cap alteració destacable de l'hematopoesi ni en ratolins jóvens (12-13 setmanes) ni envellits (2 anys). No obstant això, les seues cèl·lules mare i progenitores hematopoetiques (HSPC) van ser incapaços d'empeltar en la medul·la òssia de ratolins trasplantats. En el cas dels ratolins mutants Tet2-/-, observarem un increment de cèl·lules mieloides, esplenomegàlia, augment del compartiment LSK (cèl·lules mare amb inmunofenotip Llinatge- Sca-1+ c-kit+) i, en els experiments de trasplantament, una capacitat de reconstitució hematopoética superior a la dels controls. Finalment, la cooperació d'ambdues alteracions en la línia doble mutant U2af1mut/+ Tet2-/-, no va mostrar un efecte sinèrgic entre elles. Així, doncs, es van detectar variacions en els progenitors mieloeritroids i un augment significatiu de cèl·lules mieloides i LSK. No obstant això, igual que ocorria amb la línia U2af1mut/+, les HSPC no produïen empelt en els ratolins trasplantats. A pesar de les alteracions observades, cap de les tres línies mutants desenvolupava SMD ni moria abans que els controls. Respecte a l'anàlisi transcriptòmic, el salt d'exó va ser l'esdeveniment de splicing alternatiu observat amb major freqüència en les línies U2af1mut/+, Tet2-/- i U2af1mut/+ Tet2-/-. Únicament un 6.6 % del total de gens que presentava esdeveniments de splicing alternatiu van ser coincidents en les tres línies mutants. Encara que en l'anàlisi bioinformàtica es van detectar alteracions en les rutes biològiques relacionades amb el cicle cel·lular, en els ratolins U2af1mut/+, i el dany a l'ADN, en les línies U2af1mut/+ i U2af1mut/+ Tet2-/-, en la validació per mitjà de CF no es van trobar variacions respecte als controls. Per a concloure, les nostres dades suggerixen que, a pesar de produir-se alteracions en l'hematopoesi, la cooperació entre la mutació en U2af1 i la pèrdua de Tet2 és insuficient per a iniciar SMD en ratolí. / [EN] Myelodysplastic syndromes (MDS) comprise a heterogeneous group of clonal malignancies characterized by ineffective hematopoiesis, cytopenia and a variable risk of progression to secondary acute myeloid leukemia (AML). In the last decade, next-generation sequencing technologies have deciphered that more than 80 % of MDS patients have somatic mutations and that those can be grouped into several categories depending on which biological routes have been altered. Furthermore, it has been observed that there are concurrency and exclusion patterns among these mutation categories. The sequential acquisition and the concurrency between these driver mutations trigger, in part, the development of the disease and generate the clinical heterogeneity characteristic of MDS. The splicing factor mutations often occur simultaneously with mutations in epigenetic regulators such as the U2 Small Nuclear RNA Auxiliary Factor 1 (U2AF1) and Ten-eleven translocation 2 (TET2) genes, which are found co-mutated in 13 % of cases. Despite their prevalence, the effects of concurrence in mutations in U2AF1 and TET2 have not been studied. Consequently, in this thesis we aim to study this cooperation. Firstly, we crossed two mutant mouse lines that were previously generated using the CRISPR/Cas9 gene editing system. The effects of these alterations on hematopoiesis in the three mutant lines, U2af1mut/+, Tet2-/- y U2af1mut/+ Tet2-/-, was examinated by the blood counts, flow cytometry (FC), morphological analysis, Colony Forming Units assays (CFU) and functional studies such as the hematopoietic transplantation. Finally, transcriptomic analysis was peformed by RNA sequencing (RNA-seq) to detect possible splicing pattern changes between mutant lines and control samples. U2af1mut/+ mutant line did not present any remarkable alteration of hematopoiesis in either in young (12-13 weeks) or aged (2 years) mice. However, their hematopoietic stem and progenitor cells (HSPC) were unable to engraft into the bone marrow of transplanted mice. In the case of Tet2-/- mutant mice, we observed an increase of myeloid cells, splenomegaly, an increased LSK compartment (HSPC: Lineage- Sca-1+ c-kit+) and an enhanced ability, relative to wild-type, to reconstitute hematopoiesis in transplantation assays. Finally, the cooperation of both alterations in U2af1mut/+ Tet2-/- double mutant line did not show a synergistic effect between them. Nonetheless, the myeloerythroid progenitors were altered and also myeloid and LSK cells were increased. However, as in the U2af1mut/+ line, HSPC did not produce any engraftment in transplanted mice. Despite the observed alterations, none of the three mutant lines developed MDS or die earlier than control mice. Regarding the transcriptomic analysis, exon skipping was the most frequently observed alternative splicing event in the U2af1mut/+, Tet2-/- y U2af1mut/+ Tet2-/- lines. Only 6.6 % of the total number of genes showing alternative splicing events were coincident in the three mutant lines. Although the bioinformatic analysis revealed alterations in biological pathways related to the cell cycle in the U2af1mut/+ mice and DNA damage in the U2af1mut/+ and U2af1mut/+ Tet2-/- lines, the validation by CF found no variations with respect to the controls. In conclusion, our data suggest that, despite alterations in hematopoiesis, the cooperation between U2af1 mutation and Tet2 loss is insufficient to initiate MDS in mice. / Martínez Valiente, C. (2022). Desarrollo y caracterización de un modelo de ratón doble mutante en U2af1 y Tet2 para el estudio de los Síndromes Mielodisplásicos [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/187749

Die Gentherapie hämatopoetischer Stammzellen (HSCs) besitzt das Potenzial, verschiedene erbliche, nur symptomatisch behandelbare, Erkrankungen dauerhaft zu heilen. Die Mehrheit der aktuell angewandten Verfahren dazu, basiert auf der Isolation von hämatopoetischen Stammzellen, der ex vivo Modifikation dieser Zellen durch retrovirale Vektoren und der Reinfusion der modifizierten Zellen in den immunsupprimierten Patienten. Dieser Ansatz ist mit einer Reihe von Nachteilen verbunden, unter anderem einem teilweisen Verlust des Rekonstitutionsvermögens der Stammzellen nach ex vivo Kultur oder der Gefahr der Transformation durch Integration des retroviralen Vektorgenoms. Darüber hinaus sind aktuelle Gentherapieansätze mit hohen Kosten und großem logistischem Aufwand verbunden, was den Zugang zu diesen Behandlungen für potentielle Patienten stark einschränkt. Die vorliegende Arbeit verfolgt einen neuen Ansatz zur Gentherapie von HSCs, der auf der Mobilisierung von Stammzellen aus dem Knochenmark in den peripheren Blutstrom und der Transduktion dieser Stammzellen mit adenoviralen Vektoren basiert. Hierbei codieren die Vektoren sowohl ein Transgen als auch eine Integrationsmaschinerie. Der erste Teil der Arbeit belegt in einem humanen CD46-transgenen Mausmodell, dass adenovirale Vektoren der ersten Generation in der Lage sind, mobilisierte HSCs im Blut zu transduzieren und dass es den so transduzierten Stammzellen möglich ist, zurück ins Knochenmark zu migrieren und dort das Transgen zu exprimieren. Allerdings wurde im Verlauf von zwei Wochen ein Rückgang der Transgenexpression beobachtet. Um dies zu umgehen, wurde ein adenovirales Vektorsystem der dritten Generation genutzt, das eine hochaktive Sleeping Beauty Transposase, zum Zweck der Transgenintegration, codiert. Dieses System ermöglichte die stabile Genmodifikation mobilisierter hämatopoetischer Stammzellen nach intravenöser Injektion. Die Expression des Transgens konnte über längere Zeitspannen (bis 12 Wochen) beobachtet werden. Die modifizeirten Stammzellen waren darüber hinaus in der Lage, genmodifizierte Kolonien in vitro zu bilden und das hämatopoetische System letal bestrahlter Mäuse nach Knochenmarkstransplantation zu rekonstituieren. Es wurde somit gezeigt, dass HSCs nach in vivo Modifikation weiterhin funktional waren. / The gene therapy of hematopoietic stem cells holds the potential for curative treatment of several otherwise incurable inherited diseases. The majority of current gene therapy treatments relies on the collection of hematopoietic stem cells, their ex vivo modification with retroviral vectors and their transplantation into a myeloconditioned patient. This approach entails several disadvantages, including a reduction of stem cell engraftment potential after ex vivo culture and the potential danger of integrational mutagenesis. In addition, the high costs and complex logistics of this approach limit the access of patients to gene therapeutic regimens. This work explores an alternative approach to hematopoietic stem cell (HSC) gene therapy, termed stem cell in vivo transduction. This approach is based on the mobilization of HSCs from the bone marrow into the peripheral blood and the transduction of the stem cells with adenoviral vectors delivering a transgene as well as a transgene integration machinery. In the first part of this work, it was shown that first-generation adenoviral vectors could be used for the transduction of mobilized HSCs in the periphery of human CD46-transgenic mice. Further, the transduced HSCs were able to home back to the bone marrow and express the transgene. However, over the course of 14 days, a loss of transgene expression in HSCs was observed. To ameliorate these shortcomings, helper-dependent adenoviral vectors encoding a hyperactive Sleeping Beauty transposase for transgene integration were used for stable gene modification of hematopoietic stem cells following intravenous vector administration in mobilized human CD46-transgenic mice. Using this improved vector platform, gene marking of bone marrow HSCs could be observed for extended periods of time (up to 12 weeks). Further, the functionality of the modified HSCs was demonstrated both in colony-forming progenitor assays as well as through the transplantation of gene-modified HSCs into lethally irradiated recipients. Transplantation of modified HSCsled to long-term multi-lineage reconstitution showing that gene-modified stem cells were fully functional. Subsequently the safety of systemic vector administration in mobilized hosts as well as of the Sleeping Beauty-mediated transgene integration was assessed in human CD46- transgenic mice. Lastly, the stem cell in vivo transduction approach was employed in NOG mice transplanted with human CD34+ cells, as well as in Macaca nemestrina non-human primates.

Indiana University-Purdue University Indianapolis (IUPUI) / The hematopoietic system is highly proliferative, making hematopoietic stem and progenitor cells (HSPC) sensitive to radiation damage. Total body irradiation and chemotherapy, as well as the risk of radiation accident, create a need for countermeasures that promote recovery of hematopoiesis. Substantive damage to the bone marrow from radiation exposure results in the hematopoietic syndrome of the acute radiation syndrome (HS-ARS), which includes life-threatening neutropenia, lymphocytopenia, thrombocytopenia, and possible death due to infection and/or hemorrhage. Given adequate time to recover, expand, and appropriately differentiate, bone marrow HSPC may overcome HS-ARS and restore homeostasis of the hematopoietic system. Prostaglandin E2 (PGE2) is known to have pleiotropic effects on hematopoiesis, inhibiting apoptosis and promoting self-renewal of hematopoietic stem cells (HSC), while inhibiting hematopoietic progenitor cell (HPC) proliferation. We assessed the radiomitigation potential of modulating PGE2 signaling in a mouse model of HS-ARS. Treatment with the PGE2 analog 16,16 dimethyl PGE2 (dmPGE2) at 24 hours post-irradiation resulted in increased survival of irradiated mice compared to vehicle control, with greater recovery in HPC number and colony-forming potential measured at 30 days post-irradiation. In a sublethal mouse model of irradiation, dmPGE2-treatment at 24 hours post-irradiation is associated with enhanced recovery of HSPC populations compared to vehicle-treated mice. Furthermore, dmPGE2-treatment may also act to promote recovery of the HSC niche through enhancement of osteoblast-supporting megakaryocyte (MK) migration to the endosteal surface of bone. A 2-fold increase in MKs within 40 um of the endosteum of cortical bone was seen at 48 hours post-irradiation in mice treated with dmPGE2 compared to mice treated with vehicle control. Treatment with the non-steroidal anti-inflammatory drug (NSAID) meloxicam abrogated this effect, suggesting an important role for PGE2 signaling in MK migration. In vitro assays support this data, showing that treatment with dmPGE2 increases MK expression of the chemokine receptor CXCR4 and enhances migration to its ligand SDF-1, which is produced by osteoblasts. Our results demonstrate the ability of dmPGE2 to act as an effective radiomitigative agent, promoting recovery of HSPC number and enhancing migration of MKs to the endosteum where they play a valuable role in niche restoration.

Indiana University-Purdue University Indianapolis (IUPUI) / The potential of hematopoietic stem cells (HSC) to home and to anchor within the bone marrow (BM) microenvironment controls the ability of transplanted HSCs to establish normal hematopoiesis. Activated Leukocyte Cell Adhesion Molecule (ALCAM; also identified as CD166), which participates in homophilic interactions, is expressed on a group of osteoblasts in the hematopoietic niche capable of sustaining functional HSC in vitro. Since we could also detect ALCAM expression on HSC, we suspect that ALCAM may play a role in anchoring primitive hematopoietic cells to ALCAM expressing components of the hematopoietic niche via dimerization. We investigated the role of ALCAM on the homing abilities of hematopoietic stem and progenitor cells (HSPC) by calculating recovery frequency of Sca-1+ALCAM+ cells in an in vivo murine bone marrow transplantation model. Our data supports the notion that ALCAM promotes improved homing potential of hematopoietic Sca-1+ cells. Recovery of BM-homed Sca-1+ cells from the endosteal region was 1.8-fold higher than that of total donor cells. However, a 3.0-fold higher number of Sca-1+ALCAM+ cells homed to the endosteal region compared to total donor cells. Similarly, homed Sca-1+ALCAM+ cells were recovered from the vascular region at 2.1-fold greater frequency than total homed donor cells from that region, compared to only a 1.3-fold increase in the recovery frequency of Sca-1+ cells. In vitro quantitation of clonogenic BM-homed hematopoietic progenitors corroborate the results from the homing assay. The frequency of in vitro clonogenic progenitors was significantly higher among endosteal-homed Sca-1+ALCAM+ cells compared to other fractions of donor cells. Collectively, these data demonstrate that engrafting HSC expressing ALCAM home more efficiently to the BM and within the BM microenvironment, these cells preferentially seed the endosteal niche.

Indiana University-Purdue University Indianapolis (IUPUI) / Immunotherapy for cancer has held much promise as a potent modality of cancer treatment. The ability to selectively destroy diseased cells and leave healthy cells unharmed has been the goal of cancer immunotherapy for the past thirty years. However, the full capabilities of cancer immunotherapies have been elusive. Cancer immunotherapies have been consistently hampered by limited immune reactivity, a diminishing immune response over time, and a failure to overcome self-tolerance. Many of these deficiencies have been borne-out by immunotherapies that have focused on the adoptive transfer of activated or genetically modified mature CD8+ T cells. The limitations inherent in therapies involving terminally differentiated mature lymphocytes include limited duration, lack of involvement of other components of the immune system, and limited clinical efficacy. We sought to overcome these limitations by altering and enhancing long-term host immunity by genetically modifying then transplanting HSCs. To study these questions and test the efficiency of gene transfer, we cloned a tumor reactive HLA-DR4-restricted CD4+ TCR specific for the melanocyte differentiation antigen TRP-1, then constructed both a high expression lentiviral delivery system and a TCR Tg expressing the same TCR genes. We demonstrate with both mouse and human HSCs durable, high-efficiency TCR gene transfer, following long-term transplantation. We demonstrate the induction of spontaneous autoimmune vitiligo and a TCR-specific TH1 polarized memory effector CD4+ T cell population. Most importantly, we demonstrate the destruction of subcutaneous melanoma without the aid of vaccination, immune modulation, or cytokine administration. Overall, these results demonstrate the creation of a novel translational model of durable lentiviral gene transfer, the induction of spontaneous CD4+ T cell immunity, the breaking of self-tolerance, and the induction of anti-tumor immunity.

L’importance des modificateurs de la chromatine dans la régulation de l’hématopoïèse et des hémopathies malignes est illustrée par l’histone méthyltransférase Mixed-Lineage Leukemia (MLL) qui est essentielle au maintien des cellules souches hématopoïétiques (CSH) et dont le gène correspondant, MLL, est réarrangé dans plus de 70% des leucémies du nourrisson. Les histones déméthylases (HDM), récemment découvertes, sont aussi impliquées dans le destin des CSH et des hémopathies malignes. Le but de ce projet est d’étudier l’expression des HDM dans les cellules hématopoïétiques normales et leucémiques afin d’identifier de potentiels régulateurs de leur destin. Nous avons réalisé un profil d'expression génique des HDM par qRT-PCR et par séquençage du transcriptome (RNA-seq) dans des cellules de sang de cordon (cellules CD34+ enrichies en CSH et cellules différenciées) et des cellules de leucémie aiguë myéloïde (LAM) avec réarrangement MLL. Les deux techniques montrent une expression différentielle des HDM entre les populations cellulaires. KDM5B et KDM1A sont surexprimés dans les cellules CD34+ par rapport aux cellules différenciées. De plus, KDM4A et PADI2 sont surexprimés dans les cellules leucémiques par rapport aux cellules normales. Des études fonctionnelles permettront de déterminer si la modulation de ces candidats peut être utilisée dans des stratégies d’expansion des CSH, ou comme cible thérapeutique anti-leucémique. Nous avons aussi développé et validé un nouveau test diagnostique pour détecter les mutations de GATA2 qui code pour un facteur de transcription clé de l’hématopoïèse impliqué dans les LAM. Ces travaux soulignent l’importance des facteurs nucléaires dans la régulation de l’hématopoïèse normale et leucémique. / The importance of chromatin modifiers in regulation of hematopoiesis and hematologic malignancies is illustrated by the Mixed-Lineage Leukemia (MLL) histone methyltransferase, which is essential to maintain hematopoietic stem cells (HSC) and whose corresponding gene, MLL, is rearranged in over 70% of infant leukemia. The recently discovered histone demethylases (HDM) are also involved in HSC fate and in hematologic malignancies. The purpose of this project is to study the expression of HDM in normal and leukemic hematopoietic cells to identify potential regulators of their fate. We performed a comprehensive gene expression profile of HDM by qRTPCR and transcriptome sequencing (RNA-seq) in cord blood cells (CD34+ cells enriched in HSC and differentiated cells) and in acute myeloid leukemia (AML) cells with MLL rearrangement. Both techniques revealed differential expression of HDM between these cell populations. KDM5B and KDM1A are overexpressed in CD34+ cells compared to differentiated cells. Moreover, KDM4A and PADI2 are overexpressed in leukemic cells compared to normal cells. Functional studies will determine whether modulation of these candidates can be used in HSC expansion strategies or as anti-leukemic drug target. We have also developed and validated a new diagnostic test to detect mutations of GATA2, a gene encoding a key transcription factor involved in hematopoiesis and in AML. This work highlights the importance of nuclear factors in the regulation of normal and leukemic hematopoiesis.