Study of variables determining the engraftment and homing of human acute myeloid leukemia samples in the NSG mouse model

Acute myeloid leukemia (AML) is the most frequent hematopoietic malignancy in adults, causing death of about 90% of elderly patients. Cytogenetic and molecular abnormalities are used to categorize AML in favorable, intermediate and adverse risk groups. The classification in one of these groups will directly affect clinical decisionmaking. Although molecular criteria have significantly improved prognostication and thus AML patient stratification and treatments, they still do not allow full risk prediction. AML is a complex disease with a very high heterogeneity which makes it challenging to accurately reproduce patient phenotypes in murine models. Patient-derived xenografts can reproduce this heterogeneity but display inherent limitations including the long-latency until AML develops in those models. In this thesis, we aimed to study the variables that determine the in vivo leukemogenesis in a xenotransplantation model of human AML samples into NOD/SCID/IL2Rgnull (NSG) mice. We aimed to better understand the impact of the characteristics of the human AML cells, as well as the effect of modulation of the bone marrow (BM) microenvironment of the recipient mice on the homing and engraftment of human AML cells. Firstly, we could show that the latency of symptomatic AML induction in mice as well as the homing of transplanted AML cells into the murine BM depends on the molecular risk group established in patients. We also gained insights in the kinetics of disease induction by screening for human AML cells in the mice with regular BM biopsies. Moreover, correlation between some AML patient characteristics (expression of some particular surface markers, remission status and Flt3 (Fms-like tyrosine kinase 3) mutational status) and the behavior of the corresponding transplanted AML was observed. This suggests that this mouse model accurately depicts the clinical course of the disease and reproduces important features of human AML. Furthermore, we observed that xenotransplantation performed at night, together with disturbance of the circadian rhythm in NSG mice, accelerated engraftment and enhanced homing of transplanted human and murine AML cells compared to corresponding procedures performed in the late afternoon. Our work suggests that observed pro-oncogenic effects are mediated by catecholamines and we could prevent them by beta-blocker treatment. Therefore, varying the transplantation time17 point or inducing a stress response may optimize AML xenograft models and these observations might be important for the knowledge about the tumor-initiation processes in murine models and could possibliy be transferred to humans

Stress and catecholamines modulate the bone marrow microenvironment to promote tumorigenesis

High vascularization and locally secreted factors make the bone marrow (BM) microenvironment particularly hospitable for tumor cells and bones to a preferred metastatic site for disseminated cancer cells of different origins. Cancer cell homing and proliferation in the BM are amongst other regulated by complex interactions with BM niche cells (e.g. osteoblasts, endothelial cells and mesenchymal stromal cells (MSCs)), resident hematopoietic stem and progenitor cells (HSPCs) and pro-angiogenic cytokines leading to enhanced BM microvessel densities during malignant progression. Stress and catecholamine neurotransmitters released in response to activation of the sympathetic nervous system (SNS) reportedly modulate various BM cells and may thereby influence cancer progression. Here we review the role of catecholamines during tumorigenesis with particular focus on pro-tumorigenic effects mediated by the BM niche

Modeling hematopoietic disorders in zebrafish

Zebrafish offer a powerful vertebrate model for studies of development and disease. The major advantages of this model include the possibilities of conducting reverse and forward genetic screens and of observing cellular processes by; in vivo; imaging of single cells. Moreover, pathways regulating blood development are highly conserved between zebrafish and mammals, and several discoveries made in fish were later translated to murine and human models. This review and accompanying poster provide an overview of zebrafish hematopoiesis and discuss the existing zebrafish models of blood disorders, such as myeloid and lymphoid malignancies, bone marrow failure syndromes and immunodeficiencies, with a focus on how these models were generated and how they can be applied for translational research

Acute Myeloid Leukemia Stem Cells: The Challenges of Phenotypic Heterogeneity

Patients suffering from acute myeloid leukemia (AML) show highly heterogeneous clinical outcomes. Next to variabilities in patient-specific parameters influencing treatment decisions and outcome, this is due to differences in AML biology. In fact, different genetic drivers may transform variable cells of origin and co-exist with additional genetic lesions (e.g., as observed in clonal hematopoiesis) in a variety of leukemic (sub)clones. Moreover, AML cells are hierarchically organized and contain subpopulations of more immature cells called leukemic stem cells (LSC), which on the cellular level constitute the driver of the disease and may evolve during therapy. This genetic and hierarchical complexity results in a pronounced phenotypic variability, which is observed among AML cells of different patients as well as among the leukemic blasts of individual patients, at diagnosis and during the course of the disease. Here, we review the current knowledge on the heterogeneous landscape of AML surface markers with particular focus on those identifying LSC, and discuss why identification and targeting of this important cellular subpopulation in AML remains challenging

Improving the informed consent process in international collaborative rare disease research : effective consent for effective research

The increased international sharing of data in research consortia and the introduction of new technologies for sequencing challenge the informed consent (IC) process, adding complexities that require coordination between research centres worldwide. Rare disease consortia present special challenges since available data and samples may be very limited. Thus, it is especially relevant to ensure the best use of available resources but at the same time protect patients' right to integrity. To achieve this aim, there is an ethical duty to plan in advance the best possible consent procedure in order to address possible ethical and legal hurdles that could hamper research in the future. Therefore, it is especially important to identify key core elements (CEs) to be addressed in the IC documents for international collaborative research in two different situations: (1) new research collections (biobanks and registries) for which information documents can be created according to current guidelines and (2) established collections obtained without IC or with a previous consent that does not cover all CEs. We propose here a strategy to deal with consent in these situations. The principles have been applied and are in current practice within the RD-Connect consortia - a global research infrastructure funded by the European Commission Seventh Framework program but forward looking in terms of issues addressed. However, the principles established, the lessons learned and the implications for future research are of direct relevance to all internationally collaborative rare-disease projects

Improving the informed consent process in international collaborative rare disease research: effective consent for effective research

The increased international sharing of data in research consortia and the introduction of new technologies for sequencing challenge the informed consent (IC) process, adding complexities that require coordination between research centres worldwide. Rare disease consortia present special challenges since available data and samples may be very limited. Thus, it is especially relevant to ensure the best use of available resources but at the same time protect patients' right to integrity. To achieve this aim, there is an ethical duty to plan in advance the best possible consent procedure in order to address possible ethical and legal hurdles that could hamper research in the future. Therefore, it is especially important to identify key core elements (CEs) to be addressed in the IC documents for international collaborative research in two different situations: (1) new research collections (biobanks and registries) for which information documents can be created according to current guidelines and (2) established collections obtained without IC or with a previous consent that does not cover all CEs. We propose here a strategy to deal with consent in these situations. The principles have been applied and are in current practice within the RD-Connect consortia - a global research infrastructure funded by the European Commission Seventh Framework program but forward looking in terms of issues addressed. However, the principles established, the lessons learned and the implications for future research are of direct relevance to all internationally collaborative rare-disease projects.This work has been supported by the European Union Seventh Framework Programme (FP7/2007–2013) under grant agreements no. 305444 (RD-Connect), 305121 (Neuromics), and no. 305608 (EURenOmics) and RD-Connect from the Australian National Health and Medical Research Council APP1055319 under the NHMRC-European Union Collaborative Research Grants scheme’ as well as the IMI project BTCure (grant agreement number 115142-1), the BioBanking and Molecular Resource Infrastructure of Sweden project, Biobanking and Biomolecular Resources Research Infrastructure (BBMRI)LPC.S

SRP54 mutations induce Congenital Neutropenia via dominant-negative effects on XBP1 splicing

Heterozygous de novo missense variants of SRP54 were recently identified in patients with congenital neutropenia (CN), displaying symptoms overlapping with Shwachman-Diamond-Syndrome (SDS).1 Here, we investigate srp54 KO zebrafish as the first in vivo model of SRP54 deficiency. srp54-/- zebrafish are embryonically lethal and display, next to severe neutropenia, multi-systemic developmental defects. In contrast, srp54+/- zebrafish are viable, fertile and only show mild neutropenia. Interestingly, injection of human SRP54 mRNAs carrying mutations observed in patients (T115A, T117Δ and G226E) aggravated neutropenia and induced pancreatic defects in srp54+/- fish, mimicking the corresponding human clinical phenotypes. These data suggest that the variable phenotypes observed in patients may be due to mutation-specific dominant negative effects on the functionality of the residual wildtype SRP54 protein. Consistently, overexpression of mutated SRP54 also induced neutropenia in wildtype fish and impaired granulocytic maturation of human promyelocytic HL-60 cells as well as of healthy cord-blood derived CD34+ HSPCs. Mechanistically, srp54 mutant fish and human cells show impaired unconventional splicing of the transcription factor X-box binding protein 1 (Xbp1). Vice-versa, xbp1 morphants recapitulate phenotypes observed in srp54 deficiency and, importantly, injection of spliced, but not unspliced xbp1 mRNA rescues neutropenia in srp54+/- zebrafish. Together, these data indicate that SRP54 is critical for the development of various tissues, with neutrophils reacting most sensitively to SRP54 loss. The heterogenic phenotypes observed in patients, ranging from mild CN to SDS-like disease, may be due to different dominant negative effects of mutated SRP54 proteins on downstream XBP1 splicing, which represents a potential therapeutic target