bluuebunny/crossref_metadata_2025_split huggingface dataset:
Genetics in Inherited Bone Marrow Failure Disorders
Authors: Keel Sioban 
Published: October 2019

The classical Inherited Bone Marrow Failure Syndromes (IBMFS) such as Fanconi anemia, Dyskeratosis Congenita, Shwachman-Diamond syndrome, and Diamond-Blackfan anemia are a heterogeneous group of disorders, all of which are characterized by impaired hematopoiesis, varying degrees of peripheral cytopenias and marrow hypoplasia and dysplasia. Many of these are associated with an increased risk of clonal dominance and evolution to myelodyplastic syndrome (MDS) and acute myeloid leukemia (AML). For the purposes of this talk, the familial MDS and acute leukemia predisposition syndromes are also included in the broad term IBMFS. The genes responsible for a subset of IBMFS have been identified and will be reviewed. However, the causative mutations in many patients presenting with seemingly inherited marrow failure remain unknown. Gene discovery in IBMFS has been difficult in large part due to the phenotypic heterogeneity of these syndromes. Some patients with IBMFS display a distinct clinical phenotype with associated syndromic abnormalities, others are variable and overlap with one another or with acquired MDS or idiopathic acquired aplastic anemia, and additional cases are more obscure and have evaded classification altogether. Accurate diagnosis of IBMFS inform patient care as it allows appropriate screening of siblings to avoid choosing an affected donor if marrow transplant is indicated and the selection of an appropriate transplant conditioning regiment to avoid undue toxicity. Additionally, accurate diagnosis allows appropriate medical monitoring and early intervention to successfully treat disease-specific non-hematologic medical complications. The application of next generation sequencing approaches for comprehensive genetic screening of IBMFS, including these cryptic or atypical presentations will be reviewed. In addition to providing accurate diagnoses in a subset of patients, genetic characterization in small family kindreds or even in single individuals presents unique opportunities to discover new genes and pathways contributing to dysfunctional hematopoiesis and clonal progression. The frequency of inherited mutations in known IBMFS genes among seemingly idiopathic acquired aplastic anemia patients or pediatric and younger adults with MDS referred for hematopoietic stem cell transplant will be reviewed. Future genetic studies are needed to characterize the secondary genetic events that lead to disease progression in IBMFS.

Disclosures
No relevant conflicts of interest to declare.
Platelet Activation Gradients During Thrombus Formation
Authors: Stalker Timothy J. 
Published: October 2019

The hemostatic response requires the tightly regulated interaction of the coagulation system, platelets, other blood cells and components of the vessel wall at a site of vascular injury. The dysregulation of this response may result in excessive bleeding if the response is impaired, and pathologic thrombosis with vessel occlusion and tissue ischemia if the response is overly robust. Extensive studies over the past decades have sought to unravel the regulatory mechanisms that coordinate the multiple biochemical and cellular responses in time and space to ensure that an optimal response to vascular damage is achieved. We and others have observed that platelet activation at a site of injury in vivo is heterogeneous, with a gradient of platelet activation extending from the site of injury. Platelets immediately adjacent to the injured vessel wall are densely packed and fully activated forming a stably adherent core region. This stable core is overlaid by a shell of less activated platelets that are more loosely packed. Genetic and pharmacologic studies have shown that the formation of these regions is dependent on partially overlapping gradients of distinct platelet agonists, with ADP serving as a mediator of platelet recruitment and retention in the shell region, and thrombin necessary for full platelet activation in the core region. The distribution of platelet agonists and other plasma solutes in time and space is in turn determined in part by their transport in the plasma microenvironments that evolve as platelets accumulate. Platelet mass consolidation and the subsequent narrowing of the gaps between platelets are important mechanisms by which plasma solutes are retained within the platelet mass to promote platelet activation. Consolidation also regulates the escape of plasma and platelet-derived bioactive molecules into the extravascular space. These studies and others examining how cellular, biochemical and physical factors are integrated to shape the optimal response to vascular injury in vivo will be discussed.

Disclosures
No relevant conflicts of interest to declare.
Megakaryocytic Fate Specification and Maturation
Authors: Krause Diane S 
Published: October 2019

Megakaryocyte maturation and polyploidization are essential for effective platelet formation. In a tightly controlled process, bipotent megakaryocyte-erythroid progenitors (MEP) differentiate into diploid megakaryoblasts; undergo a progressive increase in ploidy, resulting in very large cells with multilobated polyploid nuclei; and undergo extensive cytoplasmic maturation in preparation for proplatelet release. Recent studies have begun to unravel the complex genetic and epigenetic changes that promote megakaryocyte specification from hematopoietic stem and progenitor cells, and that control subsequent megakaryocyte polyploidization and maturation. The transcriptional regulatory network underlying specification from MEP is emerging, with data revealing that many of the same factors that regulate specification also play critical roles in the final stages of megakaryocyte maturation, whereas other factors are critical for specification, but must be then inactivated in order for cell maturation to occur. Megakaryopoiesis is disrupted in several malignant and non-malignant disorders that result in significant morbidity and mortality. Mutations are inherited or acquired, and affect megakaryocyte specification, maturation and subsequent platelet formation, or both. Novel, findings will be covered in the context of normal transcriptional regulation, potential mechanisms of megakaryocyte dysplasia in MDS, and transformation to acute megakaryoblastic leukemia. These studies build the basis for our understanding of inherited and acquired megakaryocytic abnormalities and thrombocytopenias.

Disclosures
No relevant conflicts of interest to declare.
Impact of Genetic Predispositions, Diet, and Environment on Storage of Red Blood Cells
Authors: Spitalnik Steven L 
Published: October 2019

It remains controversial whether or not transfusions of human red blood cells (RBCs), which have been refrigerator-stored for extended time intervals, induce or exacerbate clinically-relevant adverse effects in recipients. The described effects include infection, inflammation, renal dysfunction, thrombosis, and even death. It is also controversial whether such effects are seen in particular patient populations predisposed to these types of complications, or whether they are universal. To this end, multiple bench research studies, clinical/translational studies, and prospective randomized controlled trials are currently investigating these issues. What is not controversial is that refrigerated storage produces the "RBC storage lesion" and that this worsens in proportion to increasing storage time, such that, at the FDA-mandated 42-day outdate, on average, only 75% of transfused donor RBCs are still circulating in the recipient at 24-hours post-transfusion. It is also not controversial that RBCs obtained from some healthy volunteer donors do not store well and, at outdate, have a 24-hour post-transfusion recovery (PTR) of significantly less than 75% (i.e., "poor storers"). Analogously, RBCs from some donors store extremely well and may exhibit virtually 100% 24-hour PTR at outdate (i.e., "super storers"). Understanding the underlying mechanisms for these phenomena would allow implementation of various approaches to improve the blood supply, with an ultimate goal of virtually 100% 24-hour PTR and normal long-term circulatory lifespan of transfused RBCs. This goal is especially relevant in the chronic transfusion setting (e.g., patients with sickle cell anemia or beta-thalassemia). Similar observations have been made about hemolysis ex vivo (i.e., "in the bag") during refrigerated storage, which influences the amount of free hemoglobin infused during the transfusion procedure. There is also evidence that these RBC storage characteristics are stable in "poor" and "super" donors, suggesting that genetic, dietary, and/or environmental factors are involved. Indeed, using inbred strains of mice, there is clear evidence that genetic and dietary factors can significantly influence donor RBC storage quality, when measured as 24-hour PTR and/or ex vivo hemolysis. In addition, human genetic polymorphisms, particularly in racial/ethnic groups enriched for malaria-induced traits, result in abnormal expression or abnormal function of various RBC proteins, including hemoglobin and cytosolic enzymes, such as glucose-6-phosphate dehydrogenase. There is increasing evidence that these polymorphisms can influence the ability of human RBCs to tolerate standard conditions of refrigerated storage. Harnessing this information will result in new methods for improving the quality of the blood supply and, consequently, improving patient responses to transfusion therapy.

Disclosures
No relevant conflicts of interest to declare.
Re-educating the Tumor Microenvironment in the Clinic
Authors: Ansell Stephen 
Published: October 2019

The tumor microenvironment plays a central role in lymphoproliferative disorders and constitution of the microenvironment is associated with patient outcome. Although malignant lymphocytes predominate, cells other than tumor cells are commonly present in malignant lymph nodes. These cells include T lymphocytes, NK cells, dendritic cells and monocytes that seem to be more than simple residual elements from the normal lymph node structure. It is thought that these infiltrating immune cells are part of an antitumor immune response, yet they appear unable to eradicate the malignant clone.
Previous studies have shown however that multiple factors present in the tumor microenvironment oppose an effective antitumor immune response. Cells with suppressive function, including T regulatory cells, myeloid derived suppressor cells and suppressive monocytes, are abundant in lymphoma tissue. Suppressive cytokines such as TGFβ and IL-10 are highly expressed in tumors. Furthermore, intratumoral T-cell exhibit an exhausted phenotype with limited proliferation, cytokine production or cytolytic function. Recent therapeutic approaches have focused on overcoming T-cell suppression by activating T-cells or blocking inhibitory signals, thereby re-educating the suppressive tumor microenvironment.
Clinical trial results with PD-1 and CTLA-4 directed antibodies in both non-Hodgkin lymphoma and Hodgkin lymphoma have been very promising. Overall response rates particularly in Hodgkin lymphoma patients treated with anti-PD-1 antibodies have been remarkable, although complete responses have been uncommon. Current studies are in progress to confirm the initial results, and further trials will assess the efficacy of immune checkpoint blockade in combination with standard therapies.

Disclosures
Ansell: Bristol-Myers Squibb: Research Funding; Celldex: Research Funding.
Mechanisms Governing Disruption of Telomere Maintenance in Dyskeratosis Congenita
Authors: Artandi Steven 
Published: October 2019

Abstract
Dyskeratosis congenita (DC) is a bone marrow failure syndrome characterized by widespread defects in diverse tissues and a strong predisposition to cancer. DC is caused by germline mutations in genes controlling maintenance of telomeres, nucleoprotein caps that protect chromosome ends. DC is part of a larger collection of telomere disorders whose manifestations include pulmonary fibrosis, liver cirrhosis and defects in many other tissues. Mutations in components of the telomerase enzyme comprise a large share of cases, including in TERT, TERC, dyskerin, TCAB1, NOP10 and NHP2. These mutations compromise telomerase function leading to telomere shortening, which in turn impairs stem cell function. The telomerase holoenzyme operates according to a complex cycle of assembly, nuclear trafficking, recruitment to telomeres and catalytic action to elongate telomeres. In patients with telomere disease states, each of these steps can be impaired leading to a common set of disease phenotypes. We previously created patient-derived iPS cells from patients with mutations in TERT, dyskerin or TCAB1 and analyzed these cells to understand the biochemical defects in the telomerase pathway. Molecular defects in these patients operate according to diverse mechanisms including: reduced catalytic function, impaired telomerase assembly, mislocalization of the enzyme to nucleoli and defective recruitment to telomeres. The development of therapeutics to treat these disease states will require approaches targeted to the underlying molecular defects in each form of the disease.

Disclosures
No relevant conflicts of interest to declare.
Extrahematopoietic Manifestations of Telomere Syndromes
Authors: Armanios Mary 
Published: October 2019

Abnormally short telomeres give rise to a group of premature aging, cancer-prone disorders known as the telomere syndromes. They are caused by germline mutations in telomerase and telomere genes. Although bone marrow failure was one of the first complications to be described in dyskeratosis congenita, there is increasing appreciation that this classic presentation is rare. Extra-hematopoietic telomere-mediated disease is frequently the first and predominant presentation in adults and leads to significant morbidity and mortality in patients with bone marrow failure (BMF), especially after bone marrow transplantation. It shows stereotypic manifestations that are age-dependent. Enterocolitis can precede the onset of BMF in infants with Hoyeraal-Hreidarsson syndrome, and it represents an intestinal epithelial defect that progresses in the setting of immunodeficiency. In adults with familial lung disease, idiopathic pulmonary fibrosis and emphysema are the predominant manifestations. These patients show variable degrees of BMF and are at risk for clonal abnormalities. In the lung transplant setting, adult telomere syndrome patients have an increased risk of complications due to immunosuppressive medications which challenge their reserves in the bone marrow, intestinal tract and elsewhere. Liver disease, often manifesting as hepatopulmonary syndrome, causes organ failure in approximately 10% of cases. The molecular mechanisms underlying telomere-mediated disease outside the bone marrow likely involve stem cell failure. For example, in the lung, alveolar stem cell senescence is sufficient to drive remodeling, inflammation, and susceptibility to injury, which are hallmark features of pulmonary fibrosis and emphysema. The stem cell failure mechanism has implications for approaching treatment in these lung disorders which have heretofore been considered mediated by inflammation. This session will present evolving scientific evidence that sheds light on the mechanisms and natural history of telomere syndromes. Considerations in the diagnostic work-up of suspected cases and the implications for patient care will be reviewed.

Disclosures
No relevant conflicts of interest to declare.
Mathematical Models of Cancer Evolution and Cure
Authors: Michor Franziska 
Published: October 2019

Abstract
Since the pioneering work of Salmon and Durie, the availability of a quantitative measure of malignant cell burden in multiple myeloma has been used to make clinical predictions and to model tumor cell growth. Here, we analyzed a large set of tumor response data from three randomized controlled clinical trials (total sample size n=1,469 evaluable patients) to establish and validate a novel mathematical model of MM cell dynamics based on responses to bortezomib-based chemotherapy regimens. Dynamics of treatment response in newly diagnosed patients were most consistent with a mathematical model postulating the existence of two tumor cell subpopulations, "myeloma progenitor cells" and "myeloma differentiated cells". Differential treatment responses were observed with significant tumoricidal effects on myeloma differentiated cells and less clear effects on myeloma progenitor cells. We validated this model using a second trial of newly diagnosed MM patients and a third trial of refractory patients. When applying our model to data of relapsed MM patients, we found that a hybrid mathematical model incorporating both a MM differentiation hierarchy and clonal evolution best explains the tumor response patterns in all patients. The clinical data, together with mathematical modeling, suggest that bortezomib-based therapy exerts a selection pressure on myeloma cells that can shape the disease phenotype, thereby generating further inter-patient variability. This model may be a useful tool for improving the rational design of chemotherapy regimens in multiple myeloma.

Disclosures
No relevant conflicts of interest to declare.
Transforming Growth Factor- β1 Signaling in Vascular Endothelial Cells Inhibits Hematopoietic Stem Cell Regeneration
Authors: Zachman Derek , Goldman Devorah C , Guha Chandan , Wilmot Beth , Fleming William H. 
Published: October 2019

Abstract
Endothelial cells (EC) are known to be essential for hematopoietic regeneration; however, little is known about the pathways that regulate this activity. By modeling endothelial-dependent HSC interactions in vitro, we found that human umbilical vein endothelial cells (HUVEC) had a markedly reduced capacity to regenerate functional CD150+LSK cells (HSC) compared to other sources of arterial and venous EC. Transcriptional profiling revealed the overexpression of transforming growth factor- β1 (TGF-β1) in HUVEC and indicated that TGF-β1 driven transcriptional programs are highly active in these cells, a finding consistent with autocrine TGF-β1 signaling. Functional studies demonstrated that HSC regeneration by EC was potently inhibited by TGF-β1 and augmented by the ALK5 inhibitor SB431542, in a dose-dependent manner. Importantly, exposure of EC alone to TGF- β1 was sufficient to attenuate subsequent HSC self-renewal. Transcriptome analysis also identified hepatocyte growth factor (HGF) as a candidate EC-derived factor with the potential to enhance hematopoietic regeneration. HGF treatment of HUVEC activated endothelial Akt signaling and led to a >10-fold increase in HSC regeneration that could be blocked by the c-Met inhibitor PF04217903. HGF treatment also dramatically increased long-term multi-lineage hematopoiesis from HUVEC regenerated HSC. Our findings reveal a novel suppressive role for TGF-β1 in the vascular niche and demonstrate that EC-derived growth factors such as HGF have the potential to attenuate this suppression and significantly enhance HSC regeneration.

Disclosures
No relevant conflicts of interest to declare.
PSC-Derived Hematopoietic System to Elucidate the Cooperation Between Gene Alterations and Cell Lineages in Leukemogenesis
Authors: Niwa Akira , Saito Megumu K , Nakahata Tatsutoshi 
Published: October 2019

Abstract
Onset of acute myeloid leukemia (AML) has been accounted for by accumulated genetic mutations including chromosomal abnormalities. For example, MLL fusion genes, which have been proven to impair cell differentiation, proliferation and epigenetic regulations, are among the common causes of pediatric AML. However, although those alterations are thought to occur in very immature stages, leukemia cells often show phenotypes similar to specific later-stage progenitors such as myeloid and monocytic cells. Until today, it remains unclear how those lineage specifications and mutations are cooperatively involved in disease pathogenesis. To address this issue in reproducible manner, we generated the lines of human pluripotent stem cells (hPSCs) harbouring doxycycline (Dox)-inducible leukemic gene cassettes, applied them for hematopoietic differentiations in a step-wise manner, and sought to identify the mechanisms behind the phenomena.
Using our system, we first evaluated the in vitro and in vivo phenotypes compatible with AML symptoms. When MLL-AF9 (MF9) transgene expression was induced in combination with cKIT (822K) or FLT3-ITD mutations, PSC-derived hematopoietic cells showed reinforced growth in liquid culture and prolonged colony forming efficacies in serial replanting assays in methylcellulose-containing semisolid media. In addition to in vitro assays, in vivo transplantations also showed the prolonged detection of graft cells as long as eight months, while those sets of "leukemia-like" phenotypes were not observed under the condition of any single transgene induction. In order to find what lineages were most responsible for those phenomena, we next induced the combination of MF9 and FLT3-ITD in various sorted subpopulations of cells. As a result, CD34+/-CD43+CD13+ myeloid precursors showed the strongest tendencies to emerge highly proliferative clones followed by CD34+CD43+CD13- immature progenitors. In the contrast, CD34-CD71+CD41+ erythro-megakaryocytic cells hardly emerged those kinds of long-term expanding clones. Those results together indicated the bias of cell lineages and stages in our disease model, and encouraged us to explore a key pathway. Interestingly, we found that a set of NFkB pathway-associating genes were significantly activated when the transgenes were induced not in erythroid but in myeloid cells, which indicated the myeloid specific mechanisms forming a bridge between this pathway and leukemic gene alterations.
In conclusion, we succeeded in establishing the way to dissect the leukemogenesis from the view of relationships between cell stages and gene alterations using PSCs. We believe that our model will enable us to better understand the pathogenesis of leukemia.

Disclosures
No relevant conflicts of interest to declare.