Academic literature on the topic 'Initiation et transformation leucémique'

Nelson Paillou can be considered a major sports leader of the second half of 20th century France. He was president of the French Handball Federation from 1964 to 1982, vice-president and eventually president of the French National Olympic and Sports Committee (CNOSF) from 1971 to 1993, and a key person in the foundation of the French association for violence-free sport and fair play. Based on printed sources and on personal as well as institutional archives, this article questions the role Paillou played in the development of French sport. First, Paillou worked to introduce and disseminate handball in France, and he developed a policy to enable masses of people to learn to play handball across the country. As such, he targeted the French youth and founded a national executive for handball technique in order to structure the supervision of players of all levels, from initiation up to the elite level. Second, Nelson Paillou also contributed to the recognition and visibility of handball in France and at European and international levels. He developed a significant communication policy and assured a remarkable presence at all handball events in order to reinforce his choices in terms of management and diffusion of the game. Finally, it appears that during the second half of the 20th century, Paillou, who strongly supported the ideals of Pierre de Coubertin, emerged as a promotor of humanist values in sport and in handball. His position against sponsors and some kind of professionalism was overcome with difficulties but it was necessary to open French handball to the international field. Paillou presented himself as an ambiguous French sports leader who sometimes took contradictory decisions. However, Paillou’s resolutions reflected the choices of an opportunistic leader in front of the transformation of sport in a period marked by the arrival of show business and professionalism.

Chronic inflammation drives initiation and progression of many malignancies, including pancreatic cancer. In this issue, Liou et al. (2013. J. Cell Biol. http://dx.doi.org/10.1083/jcb.201301001) report that inflammatory macrophages are major players in the earliest stages of pancreatic cancer. They show that paracrine signals from the macrophages activate the nuclear factor κB transcriptional program in normal pancreatic acinar cells, resulting in acinar–ductal metaplasia, a dedifferentiated state that is poised for oncogenic transformation.

The introduction of foreign genes into most of the Phoenix spp using recombinant DNA technology is not a straight forward task. In Phoenix spp application of this technology towards successful transformation proved to be a more difficult one – so far no report on the successful regeneration of transgenic date palm plants has been published. We developed an efficient and reproducible variety-independent method for producing transgenic date palm (Phoenix spp) via Agrobacterium-mediated transformation. Agrobacterium rhizogenes strains LBA 9402 were used and for cotransformation experiments the strain LBA 9402 with the binary vector pBIN19 with the p35S GUS INT gene was used. Off-shoot segments from different Phoenix spp cultivars were infected with Agrobacterium rhizogenes. The development of ‘hairy roots’ at a high frequency only on infected tissue pieces showed that transformation is possible. Various parameters like, effect of different genotypes on root initiation, root number and root length have been studied. Regeneration of transformed root cultures to plantlets was also attempted. Histochemical GUS assay and polymerase chain reaction analysis of hairy roots confirmed the presence of GUS gene. Agrobacterium tumifaciensmediated transformation was also performed using the leaves of off-shoot explants. Agrobacterium tumefaciens strains: I) GV3101 with the vir plasmid pMP90 the strain C58C1 ATHV with the vir-plasmid pTiBo542 (=pEHA101; Hood et al. 1986) was used. The nptII gene (neomycin phosphotransferase) was used as a selectable marker gene. The ?-Glucuronidase-gene (GUS-Gene: Jefferson et al. 1987) under control of the Ubi- and 35S-Promotors, with an Intron (Vancanneyt et al. 1990), was used as the reporter gene. We also used the genetically engineered Agrobacterium tumefaciens strain LBA4404 as a vector for infection in the transformation experiment, which contains plasmid pBI121 of 14 KDa (binary vector). This binary vector contains following genes within the right border (RB) and left border (LB) region of the construct: The udiA gene (Jefferson, 1986) predetermining GUS (?-glucuronidase), driven by CaMV promoter and NOS terminator. This reporter gene can be used to assess the efficiency of transformation. The nptII gene (Herrera-Estrella et al., 1983) encoding neomycin phosphotransferase II (nptII) conferring kanamycin resistance, driven by NOS promoter and NOS terminator. The bacterium also contains plasmid pAL4404 which is a disarmed Ti plasmid (132 KDa) containing the virulence genes. For the confirmation of transgenes, calli were taken from the growing callus mass for DNA isolation. PCR- and Southern analysis was performed to determine the integration and the copy number of the transgene. The GUS-test was performed to demonstrate ß-glucuronidase expression. The transgenic plantlets were kept in a hardening room for four weeks and they will be transferred to a growth chamber with controlled environment for further establishment. DOI: http://dx.doi.org/10.3329/jbau.v11i2.19841 J. Bangladesh Agril. Univ. 11(2): 171-176, 2013

Abstract Runx1, a DNA binding subunit of core binding factors, is found frequently mutated in hematological malignancies. Runx1 mutation can be an early event in leukemogenesis endowing pre-leukemic stem cells with a selective advantage in the bone marrow, and is associated with an unfavorable outcome. In mouse models, loss of function (LOF) Runx1 mutations cause a broad decrease of ribosome biogenesis in hematopoietic stem and progenitor cells (HSPCs) by directly binding to ribosomal related genes essential for protein synthesis, and confers resistance to genotoxic stress (Cai et al. 2015 Cell Stem Cell 17(2):165-77). Paradoxially, leukemia cells generally require higher biosynthetic activity, and AML patients with LOF Runx1 mutations show upregulated ribosome signatures compared with those without Runx1 mutations (Silva et al., 2009 Blood 114:3001-3007). It remains unclear whether RUNX1 plays a role in regulating protein synthesis in leukemogenesis as in normal HSPCs, and if LOF Runx1 mutations are important for leukemia initiation, transformation and/or maintenance. To examine such mechanistic roles of RUNX1 in AML progression, we have used a previously reported MLL-PTD; Mx Cre; Runx1 Flox/Flox (Double mutant -DM) mouse model (Hayashi et al., 2015 Blood 126:303 ) that allows experimental tracking of the step-wise transition of HSPCs from pre-disease stage to a MDS-like stage, prior to full blown AML. Various subpopulations of the HSPCs, including genotypic HSCs, MPP, GMP, CMP, MEP, were isolated from the mice at pre-disease, MDS-like, and AML full-blown stages, and were assayed for protein synthesis rates by O-propargyl puromycin incorporation, DNA synthesis rates by BrdU labeling, and FACS analysis. At the pre-disease state, DM HSCs, as well as all the progenitor populations, had lower protein biosynthesis activity compared with similar populations of wild-type control or MLL-PTD mutant mice, consistent with LOF Runx1 mutations providing stress-resistance and survival advantage. As disease progressed, the DM mice developed MDS-like phenotypes including severe anemia and bone marrow fibrosis, with the HSCs (LSK CD34-Flt3- cells) showing increased protein synthesis rate compared with the pre-disease DM mice. Upon the onset of full-blown leukemia, the protein translation rates in all subpopulations of DM HSPCs were significantly faster than the control non-leukemic cells, regardless of the Runx1 mutant status. Importantly, preliminary analyses of two human AML samples found that CD34+ cells with LOF Runx1 mutations displayed a similarly enhanced protein synthesis rates than CD34+ leukemia bone marrow cells carrying wild type Runx1, as seen in the mouse model. Our results show that at early initiation, LOF Runx1 mutation supresses protein biosynthesis; during transition to MDS, the inhibitory regulation was bypassed in LT-HSCs (LSK CD34-Flt3-), suggesting that Runx1-controlled protein translation is involved in the early clonal selection of disease progression. In full-blown leukemia cells including the primitive subpopulations, however the protein synthesis rate appears to become uncoupled from Runx1 regulation possibly due to an activation of compensatory machineries. This study of the role of Runx1 mutation in pre-leukemia cell progression to full blown leukemia raises the question that while some tumor initiating mutations such as LOF Runx1 mutations contribute to the tumor initiation and transformation process, they may not be essential for maintaining certain crucial leukemia cell phenotypes such as protein biosynthesis. Disclosures No relevant conflicts of interest to declare.

Abstract Background & Hypothesis: The transcriptional repressor and proto-oncogene BCL6 has recently been identified as a therapeutic target in subtypes of diffuse large B cell lymphoma (DLBCL) and as mediator of a novel for of drug-resistance in Ph+ acute lymphoblastic leukemia (ALL; Duy et al., Nature 2011). A previous senescence rescue screen identified BCL6 as a key factor that bypassed senescence and thereby enabled RAS-mediated transformation of mouse embryonic fibroblasts (Shvarts et al., Genes Dev 2002). Since ~50% of pediatric cases of ALL carry genetic lesions that result in hyperactivation of the Ras-Erk pathway (Zhang et al., Blood 2012), we tested the role of Bcl6 in this large subgroup of childhood leukemia. Results: Mutations leading to hyperactivation of the Ras-Erk pathway are found in about 50% of childhood ALL cases (Zhang et al., 2012). Among 26 ALL xenografts, we found 9 cases with constitutive Erk-T202/Y204 phosphorylation, which was paralleled by elevated expression levels of BCL6 in these cases. Studying mouse pre-B cells that were engineered with a doxycycline-inducible NRASG12D mutant, we were able to directly measure the consequences of acute activation of the Ras-Erk pathway on BCL6 expression levels. First we incubated the cells with doxycycline to induce the expression of NRASG12D and then harvested the cells at different times point to test for BCL6 protein and mRNA expression levels. Interestingly, after 24h NRASG12D-TetO pre-B cells cells showed strong upregulation of BCL6 at the mRNA (352-fold) and protein level (15-fold). Upregulation of BCL6 in response to NRASG12D-activation was sensitive to treatment with the MEK kinase inhibitor PD325901, upstream of Erk, suggesting that BCL6 expression is a consequence of Erk activation in pre-B cells. Likewise, treatment of patient-derived pre-B ALL cells with the MEK inhibitor PD325901 reversed BCL6 expression, as demonstrated by quantitative RT-PCR and Western blot. From one patient, a diagnostic (KRAS wildtype) and a relapse sample with an acquired KRASG12V mutation were available. Consistent with specific expression of BCL6 in the KRASG12V relapse ALL sample, only KRASG12V ALL cells from the relapse but not wildtype cells from the diagnostic sample were sensitive to a retro inversoBCL6 peptide inhibitor (RI-BPI; Cerchietti et al., 2009). Development of a genetic mouse model for inducible ablation of Bcl6. These findings suggest an important role of BCL6 as a cofactor of RAS-driven pre-B cell transformation, comparable to previous findings in mouse embryonic fibroblasts. To directly test a mechanistic role of Bcl6 in RAS-mediated pre-B cell transformation, we generated a novel mouse model for inducible Cre-mediated deletion of Bcl6 exons 5-10, flanked by loxP sites. For lineage-specific deletion in vivo, we crossed these mice with an Mb1-Cre deleter strain, in which Bcl6 was deleted in pro-B cells, resulting in a differentiation block at the pre-B cell stage. Interestingly, Mb1-Cre x Bcl6fl/fl B cell lineage cells could be transduced with NRASG12D retroviral vectors, however these cells did not give rise to leukemia when injected into congenic recipients, whereas NRASG12D-transduced Bcl6fl/fl pro-B cells that retained Bcl6 function developed B cell lineage leukemia in all transplant recipients. In a second experiment, we transformed Bcl6fl/fl pro-B cells with NRASG12D and induced Cre with a second, tamoxifen-inducible vector in full-blown leukemia cells. Acute ablation of Bcl6 in NRASG12D ALL cells completely abrogated the ability of NRASG12DALL cells to form colonies in methylcellulose and resulted in rapid apoptosis and depletion from the cell culture. We conclude that BCL6 is not only required for the initiation of RAS-driven ALL in vivo but also for the maintenance of fully established RAS-driven leukemia. Conclusion: These findings provide genetic evidence for BCL6 function as a critical cofactor of RAS-mediated transformation in childhood ALL. Inhibition of BCL6 in RAS-driven ALL may be useful to prevent leukemia relapse after initial remission (Bcl6-dependent leukemia-initiation) and also to achieve profound remission by combining conventional cytotoxic therapies with BCL6 inhibition (e.g. RI-BPI). Disclosures No relevant conflicts of interest to declare.

Acute myeloid leukemia (AML) is the most frequent leukemia in elderly individuals with a median age at diagnosis of 67 years (Juliusson et al., Blood 2009). It arises in a step-wise process and originates from hematopoietic stem cells (HSC) (Jan et al.,Sci Transl Med. 2012). Genetic and epigenetic alterations drive the formation of pre-leukemic HSC clones with altered function, which can gain dominance and eventually give rise to AML upon the acquisition of cooperating lesions (Jan et al.,Sci Transl Med. 2012). However, it is currently impossible to predict which healthy elderly individuals with clonal hematopoiesis will eventually develop myeloid malignancies, as the pathways to leukemia are unknown. Heterozygous inactivating mutations of the epigenetic regulator Ten-Eleven Translocation-2 (TET2) are commonly found in patients with AML, yet also in a remarkable fraction of healthy elderly individuals in whom it is associated with clonal hematopoiesis (Busque, et al Nat Genet. 2012). These observations and studies in Tet2-deficient mice strongly suggest that TET2 inactivation is an early event in the pathogenesis of myeloid malignancies, but is not sufficient to fully transform HSC (Moran-Crusio et al., Cancel Cell 2011). TET2 cooperates with several transcription factors to regulate hematopoiesis (Rasmussen et al., Genome Res 2019), one of which is PU.1 (de la Rica et al., Genome Biol. 2013), an essential transcription factor governing normal hematopoiesis (Iwasaki et al., Blood 2005). In humans, PU.1 activity or expression is only moderately impaired in the majority of AML patients, and remarkably, also in aged HSC (Will et al., Nat Med. 2015), underscoring the essentiality of PU.1. Importantly, PU.1 target genes are frequently found hypermethylated in AML (Sonnet et al., Genome Med. 2014, Kaasinen et al., Nat Commun. 2019), suggesting a profound epigenetic inactivation of the PU.1 network. We hypothesized that moderate impairment of PU.1 abundance, as found in AML, can cooperate with loss-of-function mutations of Tet2 to initiate malignancy. We developed a novel tissue-specific compound mutant mouse model carrying heterozygous deletion of an upstream regulatory element (URE) of Pu.1 along with Tet2 deletion (Vav-iCre+ PU.1URΕ∆/+Tet2+/flox; Vav-iCre+ PU.1URΕ∆/+Tet2flox/flox). While none of the single mutant mice developed AML, compound mutant mice developed aggressive myeloid leukemia whose penetrance and latency exhibited Tet2 dose dependency. The disease presented with leukocytosis, anemia and splenomegaly. By cell morphology analysis of the peripheral blood, bone marrow and spleen, the leukemic mice exhibited accumulation of differentiation-blocked myeloblasts, myelocytes and/or metamyelocytes, that was confirmed using detailed myeloid differentiation markers, distinguishing the disease in immature or mature AML. Furthermore, gold standard in vitro and in vivo assays, assessing both self-renewal and differentiation capacity of double mutant mice-derived cells, revealed that the expanded differentiation-blocked stem and progenitor cells bear aberrant self-renewal and disease-initiating capacities. Comprehensive molecular profiling by next generation sequencing of disease-initiating cells uncovered a substantial overlap with human AML, such as functional GF1b loss with concomitant overexpression of CD90/Thy1 (Thivakaran et al., Haematologica 2018). Importantly, our analyses also revealed transcriptional dysregulation, hypermethylation of PU.1 regulated enhancers with concomitant loss of enhancer activity and alterations in chromatin accessibility of particularly genes co-bound by PU.1 and TET2. Current efforts focus on identifying key effectors of the dysregulated PU.1/TET2 sub-network driving malignant transformation in clonal hematopoiesis. Our collected data provide proof of concept that moderate PU.1 dose impairment can functionally cooperate with the inactivation of Tet2 in the initiation of myeloid leukemia and uncovers a likely unifying AML pathomechansim. Disclosures Will: Novartis Pharmaceuticals: Other: Service on advisory boards, Research Funding.

Contexte : À l’Université de Montpellier, l’enseignement de la physiologie passe par une initiation à la démarche expérimentale, effectuée sous forme d’un apprentissage par problème (APP) au cours d’enseignements dirigés (ED) ou travaux pratiques (TP). Actuellement, les ED/TP de physiologie en 2e année de Diplôme de formation générale en sciences médicales (DFGSM2) posent un problème de faisabilité. But(s) : Nous avons évalué la faisabilité d’un dispositif hybride « Laboratoire numérique de physiologie (e-ϕsioLab) » combinant ED présentiels (EDP) au tableau blanc interactif (TBI) + supports multimédias, et ED dématérialisés (EDD) sur plate-forme pédagogique Moodle, pour la résolution de problèmes de physiologie en DFGSM2. Méthodes : Pour les EDP, nous avons évalué les travaux des étudiants et comparé la participation des étudiants ayant bénéficié de ces ED e-ϕsioLab vs. ED classique. Pour les EDD, nous avons évalué les travaux et la participation des étudiants. Résultats : Les travaux ont révélé que les étudiants avaient effectué les tâches d’apprentissage visées pour l’APP (élaboration d’hypothèses, manipulation de paramètres, interprétation, retour sur problème) à l’aide du dispositif hybride. Durant les EDP, la participation et les échanges entre les étudiants étaient supérieurs aux ED classiques. Etudiants et enseignants ont utilisé les fonctionnalités de l’e-ϕsioLab, permettant la production de travaux originaux et en phase avec les objectifs pédagogiques. Conclusion : Notre dispositif hybride e-ϕsioLab à forte hybridation présentiel/à distance apparaît faisable pour l’APP en physiologie. Son utilisation a révélé une forte participation des étudiants, et poussé à la transformation de l’enseignement de physiologie vers les pédagogies actives.

Abstract Abstract 121 Version:1.0 StartHTML:0000000207 EndHTML:0000006199 StartFragment:0000002599 EndFragment:0000006163 SourceURL:file://localhost/Users/mohim/Desktop/ASH%202011/Dongqing%20Yan%202011%20ASH%20Abstract.doc The JAK2V617F mutation has been identified in most cases of Ph-negative myeloproliferative neoplasms (MPNs) including polycythemia vera (PV), essential thrombocythemia (ET) and primary myelofibrosis (PMF). Expression of JAK2V617F results in constitutive activation of multiple signaling molecules/pathways. However, the key signaling downstream of JAK2V617F required for transformation, induction and maintenance of MPNs remains elusive. Using a mouse genetic strategy, we found that Stat5 is absolutely required for the pathogenesis of PV induced by Jak2V617F. Whereas inducible expression of Jak2V617F in mice resulted in all the features of human PV, including increase in red blood cells, hemoglobin, hematocrit, white blood cells, platelets, and splenomegaly, deletion of Stat5 in the Jak2V617F knock-in mice normalized all the blood parameters and the spleen size. Histopathologic analyses revealed that Stat5 deficiency blocked the development of PV in mice expressing Jak2V617F. In addition, deletion of Stat5 completely abrogated erythropoietin (Epo)-independent erythroid colony formation evoked by Jak2V617F, a hallmark feature of PV. Flow cytometric analysis revealed that concomitant deletion of Stat5 reduced the Jak2V617F-induced expansion of LSK (lin−Sca-1+c-kit+) and MEP (megakaryocyte-erythroid progenitors) as well as CD71+Ter119+ and Gr-1+Mac-1+ populations to normal levels. Unlike Jak2V617F knock-in mice, which developed myelofibrosis at old age, Stat5-deficient Jak2V617F-expressing mice failed to develop myelofibrosis. Re-expression of Stat5 in Stat5-deficient Jak2V617F knock-in mice bone marrow by retroviral transduction completely rescued the defects in transformation of hematopoietic progenitors and the PV phenotype. Furthermore, deletion of Stat5 after establishment of PV disease in the transplanted animals expressing Jak2V617F by injection with polyinosine:polycytosine (pI:pC) normalized the blood parameters and inhibited the progression of the disease. Together, these results indicate a critical function for Stat5 in the induction and maintenance of PV. Biochemical analyses revealed that Stat5 deficiency significantly inhibited constitutive phosphorylation of p70S6 kinase and markedly reduced expression of Bcl-xL, Cyclin-D2 and Pim-1 mediated by Jak2V617F. These suggest that p70S6 kinase, Bcl-xL, Cyclin-D2 and Pim-1 are downstream targets of Jak2V617F-Stat5 signaling, and they may play a role in hematopoietic transformation induced by Jak2V617F. These findings provide strong support for the development of Stat5 inhibitors as targeted therapies for the treatment of PV and other JAK2V617F-positive MPNs. Disclosures: No relevant conflicts of interest to declare.

Introduction: MDS/MPN represent a distinct category of Philadelphia chromosome negative myeloid neoplasms that share pathological and morphological characteristics with both MDS and MPN. Very few prospective studies have been conducted in pts with MDS/MPN, with currently available data showing a median overall survival (OS) of less than two years in this challenging subset. We conducted a phase 2 clinical trial evaluating the combination of JAK-inhibitor RUX with demethylating agent AZA in pts with MDS/MPN. The interim analyses (Assi et al, AJH 2018) showed objective responses in 57% pts and a median duration of response (DOR) of 8 months (mos). Herein we report the long-term follow up of a larger cohort of pts treated on this prospective ongoing clinical trial. Methods: We conducted an open label single-arm phase 2 clinical trial (NCT01787487) at the MD Anderson Cancer Center, Houston, evaluating the use of RUX-AZA in newly diagnosed or previously treated MDS/ MPN. Adults aged ≥ 18 years with MDS/MPN categorized as Intermediate 1-2 or High-risk by Dynamic International Prognosis Scoring System (DIPSS) (Passamonti et al, Blood 2010) were included. Pts previously exposed to RUX and/or AZA were excluded. RUX 5-20mg twice daily (per RUX label depending upon platelet counts at initiation) was given in 28-day cycles, and AZA 25mg/m2 (SQ or IV) Days 1- 5 was added starting cycle 4. Cycles were repeated every 4-6 weeks depending on count recovery. Response assessment was carried out using the 2015 International Consortium Proposal of response MDS/MPN criteria (Savona M et al, Blood 2015) and best objective response was tabulated. Progression free survival (PFS) included treatment change because of disease progression or inadequate response, transformation to acute myeloid leukemia (AML) or death and calculated from the time of therapy initiation. Results: From May 2013 to August 2022, 52 pts with a median age of 68 years (range, 39-82 years) were treated on trial. The data cutoff was July 15, 2023 ( Table 1). 32 pts (61%) were males, and 9 (75%) pts were white. 50 pts (96%) had ECOG PS<2. Baseline median bone marrow (BM) blasts were 4.5% (range 0-19%), with 19 (37%) carrying JAK2 mutations, and 16 (31%) with an abnormal karyotype. Intermideate-2 DIPSS was the most prevalent risk category, seen in 23 (44%) pts. At least one cytopenia was present in 32 (61%) pts, and three (6%) pts had bicytopenia. 24 of 49 (49%) had palpable splenomegaly, and 3 pts had undergone prior splenectomy. After a median follow up of 60 months (mos) (95% CI: 50.0-71.3) from therapy initiation, 18 (35%) pts are alive, and 1 pt is on active trial therapy. Objective responses per the MDS/MPN international consensus response criteria were observed in 28 (54%) pts and included clinical improvement in 14 (50%) pts, partial marrow response in 12 (43%) pts, optimal marrow response and cytogenetic complete remission in 1 (4%) pt each. The DOR in the 28 pts with objective response to therapy (censored for death in pts who died without evidence of progression) was 35 mos (95% CI: NE-73.5). The median OS in this group of responders was 36.4 mos (95% CI: NE-77.2). Five of these pts died without confirmed disease progression at the time of death. For the full cohort the median PFS was 13.4 mos (95% CI: 7.9-18.8) and median OS was 31.8 mos (95% CI: 18.5-44.9 ) (Figure 1). Transformation to AML occurred in 12 (23%) pts, with the median time to transformation being 13.2 mos (range 2.9-71.3) and all of them have died at the time of last follow-up. 8 (15%) pts underwent allogenic stem cell transplant (ASCT) as subsequent therapy following treatment with AZA-RUX amongst whom 6 (75%) had shown objective responses prior to transplant. For the pts who underwent ASCT, median PFS from the initiation of AZA-RUX was 40.8 months and median OS was not reached. Conclusion: Long term follow up from this phase II prospective clinical trial demonstrates durable disease responses with the RUX-AZA combination in MDS/MPN, with the responses translating into improved survival outcomes.

L'équipe s'intéresse aux altérations de facteurs de transcription impliquées dans les leucémies aiguës, dont PAX5 qui est essentiel pour le développement des cellules B. C'est pourquoi le modèle murin transgénique PAX5-ELN a été généré, qui exprime la protéine de fusion oncogénique durant le développement des lymphocytes B, et récapitule le processus multi-étapes des LAL-B (Jamrog L et al., PNAS, 2018). J'ai participé à l'identification des cellules à l'origine de la LAL-B et à la caractérisation de leur propriétés fonctionnelles et moléculaires. Nos travaux indiquent qu'au stade pré-leucémique, PAX5-ELN induit l'émergence d'une population aberrante de progéniteurs B avec une propriété anormale d'auto-renouvellement. Cette population est enrichie en cellules quiescentes résistantes aux agents de chimiothérapie, activent un programme moléculaire de cellule souche, et sont le support de l'initiation leucémique à long terme. Ce travail fait l'objet d'une publication récente que je signe en deuxième auteure (Fregona V, Bayet M et al., J Exp Med, in press). En parallèle, ma thèse s'est tournée vers la modélisation de l'initiation et de la transformation leucémique induite par la mutation PAX5P80R, une altération initiatrice fréquente chez les patients. J'ai donc utilisé des cellules de foie fœtal issus d'embryon de souris Pax5-/- pour sélectionner les progéniteurs lymphoïdes non engagés dans le lignage B. Après transduction avec des rétrovirus CTL, PAX5 Wt ou PAX5P80R, j'ai montré que PAX5P80R ne restaure pas efficacement l'engagement définitif des cellules vers le lignage B. Les études de transplantation ont permis de montrer que PAX5P80R induit un potentiel de prise de greffe aberrant suivi du développement de la LAL-B. Cette transformation leucémique est associée à la sélection de clones porteurs de mutations additionnelles affectant la voie JAK/STAT. Nos analyses ont permis d'identifier Hif2 comme un candidat potentiel dans la leucémogenèse. Enfin, un criblage pharmacologique d'inhibiteurs de Hif révèle l'Acriflavine comme un composé intéressant ciblant les cellules leucémiques. Ainsi, la modélisation de la LAL-B par la mutation PAX5P80R fournit à l'équipe un nouvel outil mimant le processus multi-étapes de la LAL-B, et permet de déchiffrer les mécanismes biologiques par lesquels la mutation mène à la transformation tumorale. Ce travail fait l'objet d'un manuscrit en préparation que je signe en première auteure (Bayet M, Fregona V, et al., in preparation). Les modèles PAX5-ELN et PAX5P80R permettent non seulement d'étudier les différentes étapes de la leucémogenèse B, mais servent aussi de support pour le développement de criblage de petites molécules sur cellules primaires. J'ai donc mis en place un protocole miniaturisé et robuste par FACS pour cribler des composés chimiques ciblant les cellules pré-leucémiques. Notre approche multiparamétrique permet d'évaluer simultanément l'effet des composés sur les cellules pré-leucémiques et les sous-populations B normales. J'ai donc criblé une banque de 1040 composés synthétiques et naturels (chimiothèque essentielle) reflétant la diversité chimique de la chimiothèque nationale française. Ce criblage, associé à des contre-criblages en dose-réponse, m'a permis d'identifier 5 molécules d'intérêt. Dans l'ensemble, mon travail montre la faisabilité d'un criblage de petites molécules sur une population enrichie en cellules initiatrice de la leucémie et prenant en compte la complexité intrinsèque des cellules primaires du lignage B. Enfin, j'ai procédé à la rédaction et la publication d'une revue dans le journal Cancers qui expose les concepts d'hétérogénéité tumorales des cellules leucémiques des patients, l'utilité des modèles de souris transgéniques pour explorer le compartiment des cellules initiatrices de la leucémie, et les efforts actuels visant à découvrir de nouvelles thérapies ciblées (Fregona V*, Bayet M* et al, Cancers (Basel), 2021), que je signe en co-première auteure
The team is interested in alterations in transcription factors involved in acute leukemia, including PAX5, which is essential for B-cell development. This is why the PAX5-ELN transgenic mouse model was generated, which expresses the oncogenic fusion protein during B-cell development, and recapitulates the multi-step process of B-ALL (Jamrog L et al., PNAS, 2018). I was involved in identifying the cells at the origin of-B-ALL and characterizing their functional and molecular properties. Our work indicates that at pre-leukemic stage, PAX5-ELN induces the emergence of an aberrant population of B-progenitors with an abnormal self-renewal property. This population is enriched in quiescent cells resistant to chemotherapeutic agents, activating a molecular stem cell program and supporting long-term leukemic initiation. This work is the subject of a recent publication signed by myself as second author (Fregona V, Bayet M et al., J Exp Med, in press). In parallel, my thesis focused on modeling the initiation and leukemic transformation induced by the PAX5P80R mutation, a frequent initiating alteration in patients. I used fetal liver cells derived from Pax5-/- mouse embryos to select lymphoid progenitors not committed to the B lineage. After transduction with CTL, PAX5 Wt or PAX5P80R retroviruses, I showed that PAX5P80R does not restore efficiently definitive commitment of cells to the B lineage. Transplantation experiments have shown that PAX5P80R induces aberrant engraftment potential followed by the development of B-ALL. This leukemic transformation is associated with the selection of clones carrying additional mutations affecting the JAK/STAT signaling pathway. Our analyses identified Hif2 as a potential candidate for leukemogenesis. Finally, pharmalogical screening of Hif inhibitors revealed Acriflavine as an interesting compound targeting leukemic cells. Thus, the modeling of B-ALL by the PAX5P80R mutation provides the team with a new tool to mimic the multi-step process of B-ALL, and to decipher the biological mechanisms by which the mutation leads to tumor transformation. This work is the subject of a manuscript in preparation which I have signed as first author (Bayet M, Fregona V, et al., in preparation). The PAX5-ELN and PAX5P80R models not only make it possible to study the various stages of B leukemogeneis, but also serve as a basis for the development of small molecule screening on primary cells. I therefore set up a miniaturized and robust protocol by FACS to screen chemical compounds targeting pre-leukemic cells. Our multiparametric approach enables us to simultaneously assess the effect of compounds on pre-leukeic cells and normal B subpopulations. I screened a bank of 1040 synthetic and natural compounds (essential chemical library) reflecting the chemical diversity of the French national chemical library. This screening, combined with dose-response counter-screening, enabled me to identify 5 molecules of interest. Overall, my work demonstrates the feasibility of small-molecule screening on a population enriched in leukemia-initiating cells, taking into account the intrinsic complexity of primary B-cells. Finally, I edited and published a review in the journal Cancers outlining the concepts of tumor heterogeneity in patients' leukemic cells, the utility of transgenic mouse models to explore the leukemia initiating cell compartment, and current efforts to discover new targeted therapies (Fregona V*, Bayet M* et al, Cancers (Basel), 2021), wich I co-authored

But : comparer le processus de transformation intérieure au cours de la psychothérapie par le Jeu de Sable avec la transformation du néophyte au cours des rites d'initiation chez les Chamans, dans l'Alchimie et dans les cultes à mystères en Egypte et en Grèce. Méthodologie : Analyse de 856 photos des jeux de sable construits par 28 enfants de 4 à 12 ans. Conclusion : Il existe une similitude entre le processus de transformation vécu en psychothérapie et la première des trois étapes de l'initiation vécue par le néophyte. On retrouve dans les jeux de sable des scénarios archétypiques qui peuvent être classés dans des catégories spécifiques associées aux différentes étapes de la transformation intérieure décrites dans les mythes initiatiques.

La recherche en paysage habite le dehors mentalement. Le paysage, celui qui nous émeut ou nous dégoûte, sensoriel, est envisagé ici comme une fiction concrète du corps en voyage. Éprouvée, par les voies multiples qui escortent le paysage à chaque traversée, j’interroge la validité de cet objet d’étude. Et si le paysage échappait aussitôt à chaque essai de capture ? Et comment ses multiples formes se resserrent-elles autour de soi pour nicher une complétude de l’être ? C’est ici que peut se formuler une conception du paysage comme celle d’un tissu, non plus seulement déployé sur le fond géographique mais emprisonnant dans sa fibre les corps et âme de chaque être. Le dehors, comme habitat de chaque créature, n’est plus purement un environnement, il devient un paysage. Proposer des exercices d’accès au dehors, pour pouvoir adresser le paysage de manière collective, est l’objectif de ce travail de thèse. C’est dans le contexte où habiter n’est plus proclamé par un paysage d’accueil que mon travail cherche à remettre le corps en exercice, puis en capacité d’évaluer un paysage. Un paysage se dé- clare à la fois par des représentations et des façons. Les unes traitent des expressions, les autres des matières. Entre la locution et la substance, qu’est-ce qui fait motif ? Le corps est-il susceptible de s’avancer vers le paysage et celui-ci a-t-il des ressources pour le recevoir ? Dans une première partie, plutôt que le texte déployé et discuté par des voix dissidentes, je mets en jeu des mots clefs proposés par l’enseignement pour l’élaboration d’un discours. A l’angle de la recherche et de la pratique, je construis ma thèse depuis ma place de paysagiste praticienne et enseignante du projet de paysage à L’ENSP de Versailles. Je m’appuie sur une critique de « Mouvance, 50 mots pour le paysage » proposée en 1999 par six chercheurs en paysage qui ont construit une première proposition théorique. Après un exposé, ils sont mis en débat avec un lexique construit lors des quatre années de la préparation de cette thèse. J’éprouve enfin, avec mes étudiants, la vitalité de ces mots dans des lieux de paysage ou des situations de pratiques professionnelles afin de construire sur une base vivifiée, le corpus même de ce qui peut s’exprimer en paysage. Ces termes sont la base abstraite de travaux pédagogiques conduits sur le terrain présenté dans une seconde partie. Le Parc des Lilas, à Vitry-sur-Seine est le cadre d’étude des exercices donnés dans des ateliers de projets de paysage sur lesquels travaillent mes étudiants. Ce parc, amorcé en 1980, est en cours d’agencement. Sans effet de signature, il ne trouve pas son nom, est qualifié d’inattendu, d’alias, de tempo. Des qualités lui confèrent sa substance : il devient un produit allochtone en son propre lieu. Sa chronique permet de mettre au jour une façon mobile d’accréditer le paysage d’un lieu. Le parc des Lilas sert d’appui à l’épreuve de définition des termes du lexique et se mesure à la pensée du Parc, en tant qu’objet de paysage produit. La proposition, développée en troisième partie, place le corps dans un acte de perception pour expertiser le paysage. Le protocole de recherche, immédiat, se définit à partir des produits successifs du geste, du discours oral, puis de la production écrite. La production est celle de la recherche en marche, arrêtée, glosée ; elle même projetant plus loin l’énoncé. Je présente ici une notice pour l’usage du commentaire composé de paysage (CCP), un avatar vers le projet en pédagogie appliquée. Proposition d’innovation pédagogique où protocoles et préalables participent à la remise de l’énoncé. Niveaux de langue et niveaux d’abstraction ne sont plus des obstacles à un entendement du paysage. Le CCP tient le cadre d’un don du paysage à une population entière. Réel et imaginaire revigorés sont redistribués par le jeu de leur apparition. Corps et paysage s’alimentent en une « physiologie du paysage » qui s’enseigne par fréquentation
The research in landscape mentally inhabits the outside. The landscape, the one which moves us or disgusts us, sensory, is here envisaged as a realistic fction of the traveling body. Experienced with the multiple paths which go alongside the landscape with each crossing, I question the validity of this research topic. What if the landscape escaped straight away at each attempt to capture it? How do its multiple shapes gather around themselves to nest the wholeness of one being? Here, we can try to phrase a conception of the landscape as a fabric, not only spread at a geographical level but also imprisoning in its fbers the body and the soul of each being. The outside, as the habitat of each creature, is no longer just an environment, but becomes a landscape. Suggesting exercises to access the outside to address the landscape collectively is the aim of this Ph.D. research. It is in this context where living is no longer claimed by a welcoming landscape that my work attempts to put the body back in movement and then to render it able to assess a landscape. A landscape is expressed both through representations and ways. The former are about expressions and the latter are about materials. Between the locution and the substance, what is the pattern? Is the body susceptible to move towards the landscape and does the landscape have the resources to receive it? In the frst part, rather than a text displayed and discussed by dissident voices, I involve the keywords offered by education to develop a discourse. At a crossroad between research and practice, I build my thesis from my position as a practicing landscaper and as a landscape project teacher at the ENSP in Versailles. My work relies on a criticism of Mouvance, 50 mots pour le paysage, written in 1999 by six landscape researchers, who built a frst theoretical approach. After a presentation, their views are debated with a lexicon elaborated during the four years spent working on this thesis. At last, I test with my students the vitality of these words in different landscape places or professional practice situations, in order to build on a freshened basis the very corpus of what can be expressed in the landscape. These words are the abstract basis of feldwork teaching sessions detailed in the second part. The Parc des Lilas, in Vitry-sur-Seine is the study framework of exercises done with my students in a landscape project. This park, started in 1980, is still under arrangement. Without a signature, it has no name and is defned as unexpected, an alias, a tempo. Its qualitiesualities give it its substance: it has become allochtonous, an alien product in its own place. Its chronicles enables one to unearth a changing way to ascertain the landscape of a place. The Parc des Lilas is used as a basis for the lexicon’s defnition and evaluation of the Parc’s conception as a produced landscape. In the third part, the proposition is to place the body in a landscape in order to assess it. The research protocol is immediate and is defned from successive products of movements, of speech and then of written production. The production is that of a research in action, stopped and commented, the research itself going further than its formulation. I offer here a guide for the commentaire composé de paysage (CCP), the composed commentary of the landscape, an avatar towards educational applied project, a proposition of educational innovation, where protocols and prerequisites are part of the formulation. Linguistic and abstraction levels are no longer obstacles to understanding the landscape. The CCP is the frame of a landscape offered to everyone. The real and the imaginary are redistributed as they appear. Body and landscape feed into a «landscape physiology», which is taught through attendance