scholarly journals Activation of ULK1 Kinase Mediates Clearance of Free Alpha-Globin in Human Beta-Thalassemic Erythroblasts

Blood ◽  
2018 ◽  
Vol 132 (Supplement 1) ◽  
pp. 411-411
Author(s):  
Christophe Lechauve ◽  
Julia Keith ◽  
Eugene Khandros ◽  
Stephanie Fowler ◽  
Kalin Mayberry ◽  
...  
Keyword(s):  
Board Of Directors ◽  
Protein Quality ◽  
Therapeutic Potential ◽  
Dependent Manner ◽  
Ineffective Erythropoiesis ◽  
Advisory Committees ◽  
Mtor Inhibition ◽  
Hematopoietic Stem ◽  
Rapamycin Treatment ◽  
Α Chain

Abstract β-Thalassemia is a common, frequently debilitating, inherited anemia caused by HBB gene mutations that reduce or eliminate the expression of the β-globin subunit of adult hemoglobin (HbA, α2β2). Consequently, excess free α-globin forms toxic precipitates in red blood cells (RBCs) and their precursors, leading to ineffective erythropoiesis and hemolytic anemia. Previously, we showed that free α-globin is eliminated by protein quality-control pathways, including the ubiquitin-proteasome system and autophagy (Khandros et al., Blood 2012;119:5265). In β-thalassemic mice, disruption of the Unc-51-like autophagy activating kinase gene (Ulk1) increased α-globin precipitates and worsened the pathologies of β-thalassemia. Treatment of β-thalassemic mice with rapamycin to inhibit mTOR (an ULK1 inhibitor) reduced α-globin precipitates, lessened ineffective erythropoiesis, and increased the lifespan of circulating RBCs in an Ulk1-dependent fashion. To investigate the therapeutic potential of rapamycin in human β-thalassemia, we treated erythroid precursors generated by in vitro differentiation of patient-derived CD34+ hematopoietic stem and progenitor cells. Reverse-phase high-performance liquid chromatography (HPLC) analysis of hemoglobinized erythroblasts generated from transfusion-dependent (TD, n = 5) or non-transfusion-dependent (NTD, n = 5) β-thalassemia patients revealed α-chain excesses (α-chain/β-like [β + γ + δ] chain) of approximately 40% and 15%, respectively (compared to 7 normal donors; P < 0.001). Rapamycin (10µM or 20µM) or the proteasome inhibitor MG132 (2.5µM) was added to day 13 cultures, which contained mid- to late-stage erythroblasts, and α-globin accumulation was determined by HPLC 2 days later. As expected, proteasome inhibition by MG132 raised free α-globin levels in thalassemic erythroblasts (P < 0.01) and induced cell death (P < 0.01). In contrast, rapamycin reduced free α-globin in a dose-dependent manner by 40% and 85% in TD (P < 0.0001) and NTD β-thalassemia (P < 0.001), respectively, but had no effect on erythroblasts derived from normal CD34+ cells (figure). We also observed decreases in the accumulation of autophagic markers, such as SQSTM1/p62 protein, by Western blotting. We observed no negative effects of rapamycin on the survival of patient-derived erythroblasts. Also of note, under our experimental conditions, rapamycin treatment of erythroblasts did not induce fetal hemoglobin production, as has been previously reported, thereby excluding this potential mechanism for reducing globin chain imbalances. Overall, rapamycin treatment significantly reduced the accumulation of free α-globin in TD β-thalassemia and almost fully corrected the imbalance in NTD β-thalassemia cells. Our findings identify a new drug-regulatable pathway for ameliorating β-thalassemia. Rapamycin is approved and well studied, and it has a generally manageable toxicity profile. Moreover, there are additional pharmacologic approaches to activating ULK via mTOR inhibition or other pathways. These approaches may lead to effective drug therapies for β-thalassemia, particularly NTD or intermittently TD forms of the disease. Disclosures Cappellini: Celgene Corporation: Membership on an entity's Board of Directors or advisory committees; Vifor: Membership on an entity's Board of Directors or advisory committees; Sanofi/Genzyme: Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria.

scholarly journals AVID200, a Potent Trap for TGF-β Ligands Inhibits TGF-β1 Signaling in Human Myelofibrosis

Blood ◽  
2018 ◽  
Vol 132 (Supplement 1) ◽  
pp. 1791-1791 ◽  
Author(s):  
Lilian Varricchio ◽  
John Mascarenhas ◽  
Anna Rita Migliaccio ◽  
Maureen O'Connor-McCourt ◽  
Gilles Tremblay ◽  
...  
Keyword(s):  
Stem Cell ◽  
Board Of Directors ◽  
Research Funding ◽  
Type I Collagen ◽  
Normal Donor ◽  
Type I ◽  
Cell Transplant ◽  
Dependent Manner ◽  
Advisory Committees ◽  
Hematopoietic Stem

Abstract Myelofibrosis (MF) is caused by driver mutations which upregulate JAK/STAT signaling. The only curative treatment for MF is hematopoietic stem cell transplant. Ruxolitinib alleviates many of the symptoms in MF but does not significantly alter survival. There is, therefore, an urgent need for additional rational therapies for MF. Bone marrow fibrosis and collagen deposition are hallmarks of MF which have been attributed to megakaryocyte (MK) derived TGFβ, which also plays a role in myelo-proliferation. There are three isoforms of TGFβ (TGFβ1, β2, and β3). AVID200, which was constructed by fusing TGFβR ectodomains to IgG Fc regions, is a potent TGFβ trap with pM potency against two of the three TGFβ ligands, TGFβ1 and β3 (IC50 values of ~ 3 pM ). AVID200's IC50 for TGFβ2 is ~4,000-fold higher indicating that it has minimal activity against TGFβ2, which is desirable since TGFβ2 is a positive regulator of hematopoiesis. We explored the therapeutic potential of AVID200 by culturing MF or normal donor (ND) mononuclear cells (MNCs) first in the presence of stem cell factor and thrombopoietin (TPO) and then TPO alone in order to generate MK-enriched populations. Although the percentage of mature MKs from ND and MF MNCs was similar, the absolute number of CD41+/CD42+ MKs generated from MF MNCs was two-fold greater than ND MNCs. To determine the levels of TGFβ secreted by the MKs we screened MF and ND MNC conditioned media (CM). We observed significantly higher levels of TGFβ1 but not TGFβ2 and TGFβ3 in MF MK CM. The effects of AVID200 on MKs were then evaluated by measuring the levels of phosphorylated SMAD2. Treatment with 0.001 - 0.1 nM AVID200 decreased phosphorylation of SMAD2, suggesting that AVID200 blocks autocrine MK TGFβ signaling. The increased levels of TGFβ in MF patients promote the proliferation and deposition of collagen by mesenchymal stem cells (MSCs). Cellular proliferation of MSCs was evaluated following treatment with either recombinant TGFβ1 or ND/MF CM in the presence or absence of AVID200. In the absence of AVID200, both recombinant TGFβ1 and MK-derived CM increased the proliferation of MSCs by 1.4- and 1.6-fold respectively, which returned to basal levels with the addition of increasing concentrations of AVID200. These data indicate that AVID200 directly blocks the effect of TGFβ1 on MSCs. MF stroma is characterized by an increase in Type I collagen. We therefore examined if treatment with AVID200 interferes with the ability of TGFβ1 to induce collagen expression by MSCs. MSCs were cultured in presence of recombinant TGFβ1 alone or in combination with varying concentrations of AVID200 for 72 hours. Recombinant TGFβ1 alone induced an increase in COL1A1 mRNA expression as compared to untreated controls (p<0.01). Addition of AVID200 eliminated the TGFβ-mediated increase in COL1A1 expression in a dose dependent manner. ND and MF MK-derived CM also increased COL1A1 expression by MSCs as compared to un-treated controls (p<0.01) and that effect was eliminated by AVID200 treatment (p<0.01). We next demonstrated that TGFβ1 activated pSMAD2 in MSCs without affecting total SMAD2/3 expression and that SMAD2 phosphorylation was reduced by adding AVID200. Furthermore, AVID200 treatment decreased pSTAT3 which is associated with the ability of TGFβ to induce fibrosis. We next investigated the effect of AVID200 on MF hematopoiesis. Briefly, MNCs (which produce TGFβ) from two JAK2V617F+ MF patients were incubated with or without 50 nM of AVID200 and plated in semi-solid media. Treatment with AVID200 did not affect the overall number of colonies generated, but reduced the numbers of JAKV617F+ colonies while increasing the numbers of WT colonies: for PT1, there were 32% JAKV617F+ CFUs in untreated cultures (11 JAKV617F+/34 total colonies) versus 16% JAKV617F+ CFUs (7 JAKV617F+/42 total CFUs) in AVID200 treated cultures; for PT2 there were 100% JAKV617F+ CFUs in untreated cultures (37 JAKV617F+/37 total CFUs) versus 94% JAKV617F+ CFUs (49 JAK2V617F+/52 total CFUs) in AVID200 treated cultures. The in vivo effects of AVID200 on the development of MF in GATA1 low mice will be presented at the meeting. These data indicate that AVID200 selectively suppresses TGFβ1 signaling associated with the proliferation of MSCs and type I collagen synthesis, and depletes MF MNCs of JAK2V617F+progenitor cells. We conclude that AVID200 is a promising agent for treating MF patients which will be evaluated in a phase 1 clinical trial. Disclosures Mascarenhas: Novartis: Research Funding; CTI Biopharma: Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Membership on an entity's Board of Directors or advisory committees; Roche: Research Funding; Janssen: Research Funding; Promedior: Research Funding; Merck: Research Funding; Incyte: Membership on an entity's Board of Directors or advisory committees, Research Funding. Iancu-Rubin:Incyte: Research Funding; Merck: Research Funding; Summer Road, LLC: Research Funding; Formation Biologics: Research Funding. Hoffman:Incyte: Research Funding; Summer Road: Research Funding; Merus: Research Funding; Janssen: Research Funding; Formation Biologics: Research Funding.

scholarly journals Eltrombopag Creates a Transient Chemical Phenocopy of TET2 Loss of Function That Contributes to Hematopoietic Precursor Expansion

Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 453-453
Author(s):  
Yihong Guan ◽  
Bhumika J. Patel ◽  
Metis Hasipek ◽  
Dale Grabowski ◽  
Hassan Awada ◽  
...  
Keyword(s):  
Board Of Directors ◽  
In Silico ◽  
Structural Model ◽  
Data Monitoring Committee ◽  
Dependent Manner ◽  
Loss Of Function ◽  
Advisory Committees ◽  
Hematopoietic Stem ◽  
Free System ◽  
Dose Dependent

Eltrombopag (Epag) is FDA approved for immune thrombocytopenic purpura (ITP) and aplastic anemia (AA), in which it induces tri-lineage responses in primary and refractory settings. These biologic effects suggest that Epag helps to regenerate not only committed megakaryocytic progenitors, but also hematopoietic stem and progenitor cells (HSPCs). Epag is a small molecule thrombopoietin receptor (TpoR) agonist that activates the JAK-STAT pathway to increase platelet counts similar to the polypeptide based TpoR agonist Nplate. In addition, some of Epag's activity may, unlike that of Nplate, be independent of TpoR. Epag increases HSC self-renewal in mice despite the lack of binding to murine TpoR and showed efficacy in a TpoR-deficient strain. Here we show that Epag binds and inhibits TET2 in an iron-chelation independent manner, to in this way increase precursor expansion. Since iron is a key prosthetic component of the TET2 enzyme, we determined if Epag sequestration of iron in HSPCs inhibits TET2 function. In silico modeling indicated that Epag can form a tripartate complex with Fe2+, αKG and TET2 (Fig.A). Epag interacted with TET2 via N1387 and H1984 forming a two-way H-bond and also coordinating Fe2+ sandwiched between N-Oxalylglycine a surrogate for aKG and H1381 residues of TET2 (Fig.A). To experimentally confirm the computational structural model and study the effect of Epag on TET2, we used an ELISA-based TET2 activity assay in a cell-free system. We found that Epag inhibits TET2 in a dose-dependent manner with an IC50 of 1.6±0.1 µM in the presence of 25 µM each of aKG and Fe2+ (Fig.B). Interestingly, this observed IC50 of Epag for TET2 inhibition is 10-fold lower than the plasma Cmax of Epag that is produced in humans at standard clinical doses. Therefore, we performed a dose dependent TET2 rescue experiment by increasing aKG and Fe2+. There was no proportional effect on the TET2 inhibitory IC50 of Epag upon increasing either Fe2+ or αKG suggesting the inhibition of TET2 is independent of both these co-factors (Fig.B). This was consistent with in silico structural model data indicating that Epag specifically binds and traps TET2 in an inactive state, explaining why increasing concentration of Fe2+ or Fe3+ failed to rescue TET2 activity (Fig.C). Also consistent with this model of how Epag inhibits TET2, we did not experimentally observe any significant effect of ascorbic acid (100 µM), known to activate TET2 through maintenance of Fe3+↔Fe2+ homeostasis during TET2 catalysis. Underscoring likely relevance of TpoR independent actions of Epag, Epag treatment of K562 cells displaying undetectable levels of TpoR mRNA as well as protein, significantly reduced levels of 5hmC, while Tpo had no effects on 5hmC (Fig.D). We are currently measuring, after written informed consent on an IRB approved protocol, 5hmc levels serially in patients who are receiving Epag. In summary, we demonstrate TpoR-independent actions of Epag, its direct inhibition of TET2 activity, most likely by locking TET2 in an inactive configuration. Given the fundamental role of TET2 in promoting differentiation, this mechanism-of-action of Epag could be one pathway by which it expands HSPCs, independent of TpoR. In short, Epag creates a transient chemical phenocopy of TET2 loss of function, simultaneously having the capacity to activate JAK-STAT signaling via TpoR. These actions together can explain the clinical potency of Epag. Figure Disclosures Nazha: Abbvie: Consultancy; Tolero, Karyopharma: Honoraria; Daiichi Sankyo: Consultancy; Incyte: Speakers Bureau; MEI: Other: Data monitoring Committee; Novartis: Speakers Bureau; Jazz Pharmacutical: Research Funding. Saunthararajah:Novo Nordisk: Consultancy; EpiDestiny: Consultancy, Equity Ownership, Patents & Royalties. Sekeres:Celgene: Membership on an entity's Board of Directors or advisory committees; Millenium: Membership on an entity's Board of Directors or advisory committees; Syros: Membership on an entity's Board of Directors or advisory committees. Maciejewski:Novartis: Consultancy; Alexion: Consultancy.

scholarly journals A Severe Mouse Model of Alpha-Thalassemia to Study Abnormal Iron Metabolism and Erythropoiesis, Hematopoietic Stem Cell Behavior and Development of a Gene Therapy Approach for Its Treatment

Blood ◽  
2021 ◽  
Vol 138 (Supplement 1) ◽  
pp. 2012-2012
Author(s):  
Maxwell Chappell ◽  
Danuta Jadwiga Jarocha ◽  
Laura Breda ◽  
Valentina Ghiaccio ◽  
Michael Triebwasser ◽  
...  
Keyword(s):  
Gene Therapy ◽  
Mouse Model ◽  
Board Of Directors ◽  
Globin Gene ◽  
Dependent Manner ◽  
Globin Genes ◽  
Advisory Committees ◽  
Hematopoietic Stem ◽  
Gene Therapy Approach ◽  
Globin Chains

Abstract Alpha thalassemia (α-thal) is caused by insufficient production of the α-globin protein because of either deletional or non-deletional inactivation of endogenous α-globin genes. Clinical presentation of deletional α-thal varies from an asymptomatic condition (one inactivated α-globin gene) to a complete knockout (Hb Bart's Hydrops Fetalis). In patients with severe α-thal, a blood transfusion independent state is achievable through allogeneic bone marrow transplantation. The aims of this study are to develop a novel adult mouse model of α-thal and a gene therapy approach for this disease. We generated adult animals that do not produce α-globin chains (α-KO) through transplantation of homozygous B6.129S7-Hbatm1Paz/J fetal liver cells (FLC; isolated at E14.5) into WT recipient mice. These animals demonstrate a worsening phenotype, paradoxically showing elevated hematocrit, high reticulocyte count and a high number of red blood cells (RBC) which expressed only β-globin chains (HbH). RBC show aberrant morphology and aggregation of α- globin tetramers on RBC membranes. Due to severe inability of these RBC to deliver oxygen, the mice eventually succumb to anemia, showing splenomegaly and other organ pathologies, including vaso-occlusive events. These animals show iron deposition in the liver and kidney, in agreement with very low levels of hepcidin expression in the liver, and elevated erythropoietin (EPO) in the kidney. Interestingly, α-KO embryos show lower numbers of FLC compared to WT embryos, lower frequency of engraftable hematopoietic stem cells (HSC; Lin-Sca-1+c-kit+CD48-), decreased clonogenic potential (fewer class 4 CFUs) and elevated erythroferrone. Lethally irradiated mice transplanted with FLC-KO require 5-6x as many cells as those transplanted with FLC-WT for recovery, further suggesting some level of engraftment impairment. Our current hypothesis is that excessive hypoxia in the embryos impairs HSC function and stem cell fitness. Additional assays are in progress to assess the nature of this impairment. To generate a gene therapy tool to rescue these animals and eventually cure severe human α-thal patients, we screened multiple lentiviral vectors to identify the variant capable of producing the highest human α-globin protein per copy. The selection was conducted in murine erythroleukemia cells and human umbilical cord derived erythroid progenitor (HUDEP) cells, modified by knocking out all the human α-globin genes. We identified ALS20α, a vector where α-globin is under control of the β-globin promoter and its locus control region, as the most efficient vector. One copy of ALS20α produces exogenous α-globin at a level comparable to that produced by one endogenous α-globin gene. These results suggest that a relatively low VCN could result in dramatic therapeutic benefits. Transplantation of ALS20α transduced murine BM-KO results in correction of the disease phenotype in a dose-dependent manner. At VCN&lt;1 we observe a delay in death proportional to the VCN value, while at VCN&gt;1 we observe phenotypic normalization, including Hb, hepcidin and EPO levels. We tested ALS20α in CD34 cells isolated from four patients with both deletional and non- deletional HbH disease. We measured the change of β/α-globin mRNA ratio (β/αR) and protein level by HPLC in erythroblasts derived from these cultures. For the specimen with mutational HbH, the initial β/αR matches that of healthy controls, as the mutations do not eliminate the ability for the gene to produce aberrant mRNA transcripts, and decreased with increasing VCN. Erythroblasts with deletional HbH have a β/αR approximately 3x higher than normal cells, decreasing in a dose dependent manner with increasing VCN. HPLC detection of HbH (β4), a hallmark of HbH disease, is observed in hemolysis products from all non-transduced α−thal erythroblasts. A ~50% reduction of HbH is detected in the very same specimens upon integration of ALS20α (VCN between 1 and 2). In conclusion, we generated an adult mouse model of lethal α-thal and, in preliminary experiments, we rescue it with ALS20α. Furthermore, ALS20α successfully improves α-globin levels in patient cells. Further experiments are in progress to establish the consistency of our vector's expression in vivo, as well as to demonstrate its ability to transduce bona fide long-term HSCs. Disclosures Kattamis: Agios Pharmaceuticals: Consultancy; IONIS: Consultancy; VIFOR: Consultancy; CRISPR/Vertex: Consultancy, Honoraria; BMS/Celgene: Consultancy, Honoraria, Research Funding; Chiesi: Honoraria; Novartis: Consultancy, Honoraria, Research Funding; Amgen: Consultancy. Rivella: Celgene Corporation: Consultancy; Keros Therapeutics: Consultancy, Membership on an entity's Board of Directors or advisory committees; Disc Medicine: Consultancy, Membership on an entity's Board of Directors or advisory committees; MeiraGTx: Consultancy, Membership on an entity's Board of Directors or advisory committees; Forma Theraputics: Consultancy; Incyte: Consultancy; Ionis Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees.

scholarly journals Maintenance of Hematopoietic Stem Cells Through Regulation of Wnt and mTOR Pathways.

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 2309-2309
Author(s):  
Jian Huang ◽  
Peter S. Klein
Keyword(s):  
Stem Cells ◽  
Hematopoietic Stem Cells ◽  
Signaling Pathways ◽  
Glycogen Synthase ◽  
Dependent Manner ◽  
Mtor Inhibition ◽  
Self Renewal ◽  
Hematopoietic Stem

Abstract Abstract 2309 Hematopoietic stem cells (HSCs) maintain the ability to self-renew and to differentiate into all lineages of the blood. The signaling pathways regulating hematopoietic stem cell (HSCs) self-renewal and differentiation are not well understood. We are very interested in understanding the roles of glycogen synthase kinase-3 (Gsk3) and the signaling pathways regulated by Gsk3 in HSCs. In our previous study (Journal of Clinical Investigation, December 2009) using loss of function approaches (inhibitors, RNAi, and knockout) in mice, we found that Gsk3 plays a pivotal role in controlling the decision between self-renewal and differentiation of HSCs. Disruption of Gsk3 in bone marrow transiently expands HSCs in a b-catenin dependent manner, consistent with a role for Wnt signaling. However, in long-term repopulation assays, disruption of Gsk3 progressively depletes HSCs through activation of mTOR. This long-term HSC depletion is prevented by mTOR inhibition and exacerbated by b-catenin knockout. Thus GSK3 regulates both Wnt and mTOR signaling in HSCs, with opposing effects on HSC self-renewal such that inhibition of Gsk3 in the presence of rapamycin expands the HSC pool in vivo. In the current study, we found that suppression of the mammalian target of rapamycin (mTOR) pathway, an established nutrient sensor, combined with activation of canonical Wnt/ß-catenin signaling, allows the ex vivo maintenance of human and mouse long-term HSCs under cytokine-free conditions. We also show that combining two clinically approved medications that activate Wnt/ß-catenin signaling and inhibit mTOR increases the number of long-term HSCs in vivo. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Long-Term Experience with Large Granular Lymphocytic Leukemia Evolving after Solid Organ and Hematopoietic Stem Cell Transplantation

Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 1226-1226
Author(s):  
Hassan Awada ◽  
Reda Z. Mahfouz ◽  
Jibran Durrani ◽  
Ashwin Kishtagari ◽  
Deepa Jagadeesh ◽  
...  
Keyword(s):  
Board Of Directors ◽  
Research Funding ◽  
Viral Infections ◽  
De Novo ◽  
Post Transplantation ◽  
Advisory Committees ◽  
Hematopoietic Stem ◽  
Post Transplant ◽  
Stat3 Mutations

T-cell large granular lymphocyte leukemia (T-LGLL) is a clonal proliferation of cytotoxic T lymphocytes (CTL). T-LGLL mainly manifest in elderly and is associated with autoimmune diseases including rheumatoid arthritis (RA), B cell dyscrasias, non-hematologic cancers and immunodeficiency (e.g., hypogammaglobulinemia). LGL manifestations often resemble reactive immune processes leading to the dilemmas that LGLs act like CTL expansion during viral infections (for example EBV associated infectious mononucleosis). While studying a cohort of 246 adult patients with T-LGLL seen at Cleveland Clinic over the past 10 years, we encountered 15 cases of overt T-LGLL following transplantation of solid organs (SOT; n=8) and hematopoietic stem cell transplantation (HSCT; n=7). Although early studies reported on the occurrence of LGL post-transplant, these studies focused on the analysis of oligoclonality skewed reactive CTL responses rather than frank T-LGLL. We aimed to characterize post-transplantation T-LGLL in SOT and HSCT simultaneously and compare them to a control group of 231 de novo T-LGLL (cases with no history of SOT or HSCT). To characterize an unambiguous "WHO-defined T-LGLL" we applied stringent and uniform criteria. All cases were diagnosed if 3 out of 4 criteria were fulfilled, including: 1) LGL count >500/µL in blood for more than 6 months; 2) abnormal CTLs expressing CD3, CD8 and CD57 by flow cytometry; 3) preferential usage of a TCR Vβ family by flow cytometry; 4) TCR gene rearrangement by PCR. In addition, targeted deep sequencing for STAT3 mutations was performed and charts of bone marrow biopsies were reviewed to exclude other possible conditions. Diagnosis was made 0.2-27 yrs post-transplantation (median: 4 yrs). At the time of T-LGLL diagnosis, relative lymphocytosis (15-91%), T lymphocytosis (49-99%) and elevated absolute LGL counts (>500 /µL; 93%) were also seen. Post-transplantation T-LGLL were significantly younger than de novo T-LGLL, (median age: 48 vs. 61 yr; P<.0001). Sixty% of post-transplantation T-LGLL patients were males. Fifteen% of patients had more cytogenetic abnormalities compared to de novo T-LGLL, had a lower absolute LGL count (median: 4.5 vs. 8.5 k/µL) and had less frequent neutropenia, thrombocytopenia and anemia (27 vs. 43%, 33 vs. 35% and 20% vs. 55%; P=.01). TCR Vb analysis identified clonal expansion of ≥1 of the Vb proteins in 60% (n=9) of the patients; the remaining 40% (n=6) of the cases had either a clonal process involving a Vb protein not tested in the panel (20%; n=3) or no clear expansion (20%; n=3). Signs of rejection were observed in 20% (n=3/15) and GvHD in 13% (n=2/15) of the patients. Post-transplantation, 27% of cases presented with neutropenia (absolute neutrophil count <1.5 x109/L; n=4), 33% with thrombocytopenia (platelet count <150 x109/L; n=5) and 25% with anemia (hemoglobin <10 g/dL; n=3). T-LGLL evolved in 10 patients (67%; 10/15) despite IST including cyclosporine (n=5), tacrolimus (n=4), mycophenolate mofetil (n=5), cyclophosphamide (n=1), anti-thymocyte globulin (n=1), and corticosteroids (n=6). Lymphadenopathy and splenomegaly were seen in 13% (n=2) and 33% (n=5) of the patients. Other conditions observed were MGUS (20%; n=3) and RA (7%; n=1). Conventional cytogenetic showed normal karyotype in 89% (n=11, tested individuals 13/15). Somatic STAT3 mutations were identified in 2 patients. Sixty% of cases (n=9) were seropositive for EBV when tested at different time points after transplant. Similarly, 53% (n=8) were seropositive for CMV, of which, 5 were positive post-transplantation and 3 pre-/post-transplantation. The complexity of T-LGLL expansion post-transplantation might be due to several mechanisms including active viral infections, latent oncogenic viral reactivation and graft allo-antigenic stimulation. However, in our cohort graft rejection or GvHD was encountered in a few patients (2 allo-HSCT recipients). Autoimmune conditions were present in 50% of SOT recipients (n=4/ 8, including RA, ulcerative colitis, systemic lupus erythematosus). Some of our patients also had low immunoglobulin levels. Overt EBV (post-transplant lymphoproliferative disorder) and CMV reactivation was diagnosed in only 27% (4/15) of the patients. In sum we report the long term follow up of a cohort of T-LGLL and emphasize the expansion of T-LGLL post-transplant highlighting the difficulty in assigning one unique origin of LGLL. Disclosures Hill: Genentech: Consultancy, Research Funding; Takeda: Research Funding; Celegene: Consultancy, Honoraria, Research Funding; Kite: Consultancy, Honoraria; Abbvie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Seattle Genetics: Consultancy, Honoraria; Amgen: Research Funding; Pharmacyclics: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Gilead: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; TG therapeutics: Research Funding; AstraZeneca: Consultancy, Honoraria. Majhail:Atara Bio: Consultancy; Mallinckrodt: Honoraria; Nkarta: Consultancy; Anthem, Inc.: Consultancy; Incyte: Consultancy. Sekeres:Syros: Membership on an entity's Board of Directors or advisory committees; Millenium: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees. Maciejewski:Alexion: Consultancy; Novartis: Consultancy.

scholarly journals A Phase 1 Dose Escalation Study of Dual PI3K and DNA PK Inhibitor, BR101801 in Adult Patients with Advanced Hematologic Malignancies

Blood ◽  
2021 ◽  
Vol 138 (Supplement 1) ◽  
pp. 3562-3562
Author(s):  
Tae Min Kim ◽  
Dok Hyun Yoon ◽  
Ahmad H. Mattour ◽  
Jorge M. Chaves ◽  
Emily Curran ◽  
...  
Keyword(s):  
Phase I ◽  
Disease Progression ◽  
Board Of Directors ◽  
Dose Escalation ◽  
Dose Range ◽  
Human Study ◽  
Hematologic Malignancies ◽  
Dose Titration ◽  
Dependent Manner ◽  
Advisory Committees

Abstract Background: BR101801 not only blocks the signaling responsible for cell growth caused by PI3K, but also efficiently induces cell cycle arrest and apoptosis through inhibition of DNA-PK activation and stimulates decreasing stability of the oncogenic protein, c-Myc(AACR2020 abstract #655). This phase I study evaluated safety, tolerability, pharmacokinetics and preliminary activity of the BR101801 (PI3Kγ/δ and DNA PK inhibitor) in patients with advanced hematologic malignancies. Method: This is a Phase I, multi-center, open-label, first-in-human study. The Phase Ia (dose escalation) part of the study was designed to determine the maximum tolerated dose (MTD)/recommended dose for expansion (RDE) of BR101801. BR101801 was administered orally once daily in 28-day cycles. The dose escalation part was initiated with a dose titration in the initial cohort, followed by a 3 + 3 design. Results: 11 patients were enrolled and have been treated at 4 dose levels: 50mg, 100mg, 200mg, 325mg and expanded 200mg through fifth cohort escalation. Pathological subtypes include 7 PTCL, 2 DLBCL, 1 MZBL and 1 composite CTCL/MF. 3 females and 8 males have been treated to date. Median age is 58 (range 30-71) and ECOG PS is in the range of 0-1. All patients had taken at least one prior chemotherapy. 10 of total patients have completed at least one cycle except 1 premature drop-out case due to disease progression. First interim analysis after completion of cycle 3 of the last patient of 200mg QD cohort had been conducted, which was to include 5 patients (1 DLBCL and 4 PTCLs). No DLT had been identified in Cohorts 1-3, and 2 patients discontinued the study treatment due to adverse event (G4 thrombocytopenia, not related to IP) and disease progression, respectively. The PK values from multiple dosing range of 50mg to 200mg cohort resulted in an approximate 2.92-fold and 4.97 fold increase in exposure based on Cmax and AUCtau, respectively. BR101801 PK profile showed that the exposure of concentration increased in a dose dependent manner and there was no accumulation observed in the dose range of 50mg to 200mg. 2 DLTs was observed at 325mg QD cohort. The dose was de-escalated to the previous lower dose level (200mg QD) and was expanded to 3 additional patients. The expansion cohort is ongoing at present. 2 of 11 patients had G3 skin reaction and 3 had G3 hepatotoxicites. All adverse effects were manageable and recovered to grade 0-1 upon BR1010801 discontinuation. Total 5 patients have been currently ongoing. For overall tumor response assessment, 4 SDs and 2 PRs have been obsereved. Summary/Conclusion: 200 mg QD of BR101801 was shown to provide target exposure for clinical efficacy with the tolerable and safe profiles. BR101801 was well tolerated and showed preliminary signs of activity in patients with relapsed or refractory hematologic malignancies. The phase Ib/II study of BR101801 is warranted in relapsed/refractory NHL. This study is registered at clinicaltrials.gov identifier NCT04018248. Disclosures Kim: AstraZeneca-KHIDI: Research Funding; Takeda: Consultancy, Membership on an entity's Board of Directors or advisory committees; Sanofi: Consultancy, Membership on an entity's Board of Directors or advisory committees; Roche/Genentech: Consultancy, Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; GI CELL: Consultancy, Membership on an entity's Board of Directors or advisory committees; Hanmi: Consultancy, Membership on an entity's Board of Directors or advisory committees; Boryung: Consultancy, Membership on an entity's Board of Directors or advisory committees; BeyondBIO: Consultancy, Membership on an entity's Board of Directors or advisory committees; Bayer: Consultancy, Membership on an entity's Board of Directors or advisory committees; AstraZeneca/MedImmune: Consultancy, Membership on an entity's Board of Directors or advisory committees. Curran: Servier pharmaceuticals and Amgen: Consultancy. Kim: Boryung pharmaceuticals: Current Employment.

scholarly journals Pegaspargase Can Safely be Administered in Adults Age 40 and Older with Acute Lymphoblastic Leukemia

Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 3816-3816 ◽  
Author(s):  
Ryan J. Daley ◽  
Sridevi Rajeeve ◽  
Charlene C. Kabel ◽  
Jeremy J. Pappacena ◽  
Sarah E. Stump ◽  
...  
Keyword(s):  
Acute Lymphoblastic Leukemia ◽  
Board Of Directors ◽  
Research Funding ◽  
Lymphoblastic Leukemia ◽  
Philadelphia Chromosome ◽  
Hypersensitivity Reactions ◽  
Newly Diagnosed ◽  
Advisory Committees ◽  
Hematopoietic Stem ◽  
Frontline Treatment

Introduction: Asparaginase (ASP) has demonstrated a survival benefit in pediatric patients (pts) with acute lymphoblastic leukemia (ALL) and is now part of standard-of-care frontline treatment. As a result, asparaginase preparations have been incorporated into the treatment of adult ALL to improve outcomes. Pegaspargase (PEG-ASP), a modified version of asparaginase with prolonged asparagine depletion, appears to be safe in adults up to age 40 (Stock, et al., Blood, 2019), but is associated with a unique spectrum of toxicities, the risks of which appear to increase with age. Therefore, the safety of PEG-ASP remains a significant concern in older adults w/ ALL. Methods: We conducted a single center retrospective chart review of pts age ≥40 years who received PEG-ASP as part of frontline induction/consolidation or reinduction, between March 2008 and June 2018 at Memorial Sloan Kettering Cancer Center. The primary objective was to evaluate the tolerability and toxicity of PEG-ASP based on the incidence and severity of ASP-related toxicities (hypersensitivity reactions, hypertriglyceridemia, hyperbilirubinemia, transaminitis, pancreatitis, hypofibrinogenemia, etc) according to the Common Terminology Criteria for Adverse Events, version 4.03. Laboratory values recorded were either the peak or the nadir, the more appropriate for toxicity assessment, within a 4-week period following PEG-ASP administration. Secondary objectives were to determine the total number of doses of PEG-ASP administered in comparison to the number of doses intended, and to characterize the rationale for PEG-ASP discontinuation when applicable. Fisher's exact test was used to compare the incidence of PEG-ASP toxicities with respect to pt and treatment characteristics (regimen, age, BMI, gender, Philadelphia chromosome positive (Ph+) vs. Ph-, presence of extramedullary disease, PEG-ASP dose). P values were not adjusted for multiple comparisons. Results: We identified 60 pts with ALL (40 B-ALL and 20 T-ALL) who received at least one dose of PEG-ASP. Nine pts were Ph+. The median pt age at initiation of the treatment was 53, (range, 40 to 80), and 19 pts had a BMI ≥30 kg/m2. Forty-four pts received treatment for newly diagnosed ALL, and 16 pts for relapsed disease. Table 1 lists pt baseline characteristics. Among the 44 pts with newly diagnosed ALL, 27 pts received PEG-ASP as part of pediatric or pediatric-inspired regimens at doses of 2000 - 2500 units/m2, and 1 pt received a modified dose of 1000 units/m2 due to age. The remaining 16 pts received PEG-ASP at doses of 1000 - 2000 units/m2 for consolidation, per established adult regimens (ALL-2 and L-20; Lamanna, et al., Cancer, 2013). Grade 3/4 ASP-related toxicities with a >10% incidence included: hyperbilirubinemia, transaminitis, hypoalbuminemia, hyperglycemia, hypofibrinogenemia, and hypertriglyceridemia. Frontline treatment regimens in which PEG-ASP was used in consolidation cycles only (ALL-2, L-20) were associated w/ a lower incidence of hyperbilirubinemia (p=0.009) and hypertriglyceridemia (p<0.001) compared to those regimens that included PEG-ASP during induction (pediatric/pediatric-inspired regimens) (Table 2). Younger age (40-59 vs. ≥60 years) was associated with a greater risk of hypertriglyceridemia (p<0.001) and higher PEG-ASP dose (≥2000 vs. <2000 units/m2) was associated with a greater risk of hypertriglyceridemia and hypofibrinogenemia (p=0.002 and p=0.025, respectively). Thirty-eight pts (63%) received all intended doses of PEG-ASP. Six pts stopped PEG-ASP to proceed to allogeneic hematopoietic stem cell transplantation (5 in CR1, 1 in CR2), and 7 pts stopped for hypersensitivity reactions. Hepatotoxicity was the only ASP-related toxicity that led to PEG-ASP discontinuation occurring in 5 pts (hyperbilirubinemia, N=4; transaminitis, N=1). The total number of intended doses of PEG-ASP based on regimens used was 186, and 112 were administered. Conclusion: PEG-ASP was incorporated into the treatment of 60 adult ALL pts age ≥40, with manageable toxicity. Seven pts discontinued PEG-ASP due to hypersensitivity reactions and 5 discontinued due to hepatotoxicity, but other reported toxicities did not lead to PEG-ASP discontinuation and the majority of the pts completed all intended doses of PEG-ASP. This study suggests that with careful monitoring, PEG-ASP can safely be administered in adults ≥40 years of age. Disclosures Rajeeve: ASH-HONORS Grant: Research Funding. Tallman:UpToDate: Patents & Royalties; Oncolyze: Consultancy, Membership on an entity's Board of Directors or advisory committees; Delta Fly Pharma: Consultancy, Membership on an entity's Board of Directors or advisory committees; Abbvie: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Rigel: Consultancy, Membership on an entity's Board of Directors or advisory committees; Cellerant: Research Funding; Tetraphase: Consultancy, Membership on an entity's Board of Directors or advisory committees; Nohla: Consultancy, Membership on an entity's Board of Directors or advisory committees; BioLineRx: Consultancy, Membership on an entity's Board of Directors or advisory committees; Orsenix: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; ADC Therapeutics: Research Funding; Biosight: Research Funding; Jazz Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees; KAHR: Consultancy, Membership on an entity's Board of Directors or advisory committees; Daiichi-Sankyo: Consultancy, Membership on an entity's Board of Directors or advisory committees. Geyer:Dava Oncology: Honoraria; Amgen: Research Funding. Park:Takeda: Consultancy; Allogene: Consultancy; Amgen: Consultancy; AstraZeneca: Consultancy; Autolus: Consultancy; GSK: Consultancy; Incyte: Consultancy; Kite Pharma: Consultancy; Novartis: Consultancy.

scholarly journals Lower Hematopoietic Progenitor Cell Counts and Yields at Subsequent Donations Is Influenced By a Shorter Inter-Donation Interval between the First and Subsequent Mobilizations

Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 1962-1962
Author(s):  
Sandhya R. Panch ◽  
Brent R. Logan ◽  
Jennifer A. Sees ◽  
Bipin N. Savani ◽  
Nirali N. Shah ◽  
...  
Keyword(s):  
Stem Cell ◽  
Board Of Directors ◽  
Peripheral Blood ◽  
Research Funding ◽  
Time Interval ◽  
Advisory Committees ◽  
Hematopoietic Stem ◽  
Peripheral Blood Cd34 ◽  
Cell Counts ◽  
Cd34 Cells

Introduction: Approximately 7% of unrelated hematopoietic stem cell (HSC) donors are asked to donate a subsequent time to the same or different recipient. In a recent large CIBMTR study of second time donors, Stroncek et al. incidentally found that second peripheral blood stem cell (PBSC) collections had lower total CD34+ cells, CD34+ cells per liter of whole blood processed, and CD34+ cells per kg donor weight. Based on smaller studies, the time between the two independent PBSC donations (inter-donation interval) as well as donor sex, race and baseline lymphocyte counts appear to influence CD34+ cell yields at subsequent donations. Our objective was to retrospectively evaluate factors contributory to CD34+ cell yields at subsequent PBSC donation amongst NMDP donors. Methods. The study population consisted of filgrastim (G-CSF) mobilized PBSC donors through the NMDP/CIBMTR between 2006 and 2017, with a subsequent donation of the same product. evaluated the impact of inter-donation interval, donor demographics (age, BMI, race, sex, G-CSF dose, year of procedure, need for central line) and changes in complete blood counts (CBC), on the CD34+ cell yields/liter (x106/L) of blood processed at second donation and pre-apheresis (Day 5) peripheral blood CD34+ cell counts/liter (x106/L) at second donation. Linear regression was used to model log cell yields as a function of donor and collection related variables, time between donations, and changes in baseline values from first to second donation. Stepwise model building, along with interactions among significant variables were assessed. The Pearson chi-square test or the Kruskal-Wallis test compared discrete variables or continuous variables, respectively. For multivariate analysis, a significance level of 0.01 was used due to the large number of variables considered. Results: Among 513 PBSC donors who subsequently donated a second PBSC product, clinically relevant decreases in values at the second donation were observed in pre-apheresis CD34+ cells (73.9 vs. 68.6; p=0.03), CD34+cells/L blood processed (32.2 vs. 30.1; p=0.06), and total final CD34+ cell count (x106) (608 vs. 556; p=0.02). Median time interval between first and second PBSC donations was 11.7 months (range: 0.3-128.1). Using the median pre-apheresis peripheral blood CD34+ cell counts from donation 1 as the cut-off for high versus low mobilizers, we found that individuals who were likely to be high or low mobilizers at first donation were also likely to be high or low mobilizers at second donation, respectively (Table 1). This was independent of the inter-donation interval. In multivariate analyses, those with an inter-donation interval of >12 months, demonstrated higher CD34+cells/L blood processed compared to donors donating within a year (mean ratio 1.15, p<0.0001). Change in donor BMI was also a predictor for PBSC yields. If donor BMI decreased at second donation, so did the CD34+cells/L blood processed (0.74, p <0.0001). An average G-CSF dose above 960mcg was also associated with an increase in CD34+cells/L blood processed compared to donors who received less than 960mcg (1.04, p=0.005). (Table 2A). Pre-apheresis peripheral blood CD34+ cells on Day 5 of second donation were also affected by the inter-donation interval, with higher cell counts associated with a longer time interval (>12 months) between donations (1.23, p<0.0001). Further, independent of the inter-donation interval, GCSF doses greater than 960mcg per day associated with higher pre-apheresis CD34+ cells at second donation (1.26, p<0.0001); as was a higher baseline WBC count (>6.9) (1.3, p<0.0001) (Table 2B). Conclusions: In this large retrospective study of second time unrelated PBSC donors, a longer inter-donation interval was confirmed to be associated with better PBSC mobilization and collection. Given hematopoietic stem cell cycling times of 9-12 months in humans, where possible, repeat donors may be chosen based on these intervals to optimize PBSC yields. Changes in BMI are also to be considered while recruiting repeat donors. Some of these parameters may be improved marginally by increasing G-CSF dose within permissible limits. In most instances, however, sub-optimal mobilizers at first donation appear to donate suboptimal numbers of HSC at their subsequent donation. Disclosures Pulsipher: CSL Behring: Membership on an entity's Board of Directors or advisory committees; Miltenyi: Research Funding; Bellicum: Consultancy; Amgen: Other: Lecture; Jazz: Other: Education for employees; Adaptive: Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Medac: Honoraria. Shaw:Therakos: Other: Speaker Engagement.

scholarly journals Epigenetic Activation of the pH Regulator MCT4 in Acute Myeloid Leukemia Exploits a Fundamental Metabolic Process of Enhancing Cell Growth through Proton Shifting

Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 3765-3765
Author(s):  
Cheuk-Him Man ◽  
David T. Scadden ◽  
Francois Mercier ◽  
Nian Liu ◽  
Wentao Dong ◽  
...  
Keyword(s):  
Acute Myeloid Leukemia ◽  
Cell Growth ◽  
Board Of Directors ◽  
Myeloid Leukemia ◽  
Monocarboxylate Transporter ◽  
Advisory Committees ◽  
Hematopoietic Stem ◽  
Equity Ownership ◽  
Acute Myeloid

Acute myeloid leukemia (AML) cells exhibit metabolic alterations that may provide therapeutic targets not necessarily evident in the cancer cell genome. Among the metabolic features we noted in AML compared with normal hematopoietic stem and progenitors (HSPC) was a strikingly consistent alkaline intracellular pH (pHi). Among candidate proton regulators, monocarboxylate transporter 4 (MCT4) mRNA and protein were differentially increased in multiple human and mouse AML cell lines and primary AML cells. MCT4 is a plasma membrane H+and lactate co-transporter whose activity necessarily shifts protons extracellularly as intracellular lactate is extruded. MCT4 activity is increased when overexpressed or with increased intracellular lactate generated by glycolysis in the setting of nutrient abundance. With increased MCT4 activity, extracellular lactate and protons will increase causing extracellular acidification while alkalinizing the intracellular compartment. MCT4-knockout (MCT4-KO) of mouse and human AMLdid not induce compensatory MCT1 expression, reduced pHi, suppressed proliferation and improved animal survival. Growth reduction was experimentally defined to be due to intracellular acidification rather than lactate accumulation by independent modulation of those parameters. MCT4-KOmetabolic profiling demonstrated decreased ATP/ADP and increased NADP+/NADPH suggesting suppression of glycolysis and the pentose phosphate pathway (PPP) that was confirmed by stable isotopic carbon flux analyses. Notably,the enzymatic activity of purified gatekeeper enzymes, hexokinase 1 (HK1), pyruvate kinase M2 isoform (PKM2) and glucose-6-phosphate dehydrogenase (G6PDH) was sensitive to pH with increased activity at the leukemic pHi (pH 7.6) compared to normal pHi (pH 7.3). Evaluating MCT4 transcriptional regulation, we defined that activating histonemarks, H3K27ac and H3K4me3, were enriched at the MCT4 promoter region as were transcriptional regulators MLL1 and Brd4 by ChIP in AML compared with normal cells. Pharmacologic inhibition of Brd4 suppressed Brd4 and H3K27ac enrichment and MCT4 expression in AML and reduced leukemic cell growth. To determine whether MCT4 based pHi changes were sufficient to increase cell proliferation, we overexpressed MCT4 in normal HSPC and demonstrated in vivo increases in growth in conjunction with pHi alkalization. Some other cell types also were increased in their growth kinetics by MCT4 overexpression and pHi increase. Therefore, proton shifting may be a means by which cells respond to nutrient abundance, co-transporting lactate and protons out of the cell, increasing the activity of enzymes that enhance PPP and glycolysis for biomass generation. Epigenetic changes in AML appear to exploit that process by increasing MCT4 expression to enforce proton exclusion thereby gaining a growth advantage without dependence on signaling pathways. Inhibiting MCT4 and intracellular alkalization may diminish the ability of AML to outcompete normal hematopoiesis. Figure Disclosures Scadden: Clear Creek Bio: Consultancy, Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Novartis: Other: Sponsored research; Editas Medicine: Consultancy, Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Bone Therapeutics: Consultancy; Fog Pharma: Consultancy; Red Oak Medicines: Consultancy, Equity Ownership, Membership on an entity's Board of Directors or advisory committees; LifeVaultBio: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Magenta Therapeutics: Consultancy, Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Agios Pharmaceuticals: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Fate Therapeutics: Consultancy, Equity Ownership.

scholarly journals Inducible SBDS Deficiency Impairs Bone Marrow Niche Function to Engraft Donor Hematopoietic Stem Cell after Transplantation

Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 3199-3199
Author(s):  
Ji Zha ◽  
Lori Kunselman ◽  
Hongbo Michael Xie ◽  
Brian Ennis ◽  
Jian-Meng Fan ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Stem Cell ◽  
Mouse Model ◽  
Board Of Directors ◽  
Hematopoietic Stem Cell ◽  
Graft Failure ◽  
Advisory Committees ◽  
Hematopoietic Stem ◽  
Bm Niche ◽  
Deficient Mice

Hematopoietic stem cell (HSC) transplantation (HSCT) is required for curative therapy for patients with high-risk hematologic malignancies, and a number of non-malignant disorders including inherited bone marrow failure syndromes (iBMFS). Strategies to enhance bone marrow (BM) niche capacity to engraft donor HSC have the potential to improve HSCT outcome by decreasing graft failure rates and enabling reduction in conditioning intensity and regimen-associated complications. Several studies in animal models of iBMFS have demonstrated that BM niche dysfunction contributes to both the pathogenesis of iBMFS, as well as impaired graft function after HSCT. We hypothesize that such iBMFS mouse models are useful tools for discovering targetable niche elements critical for donor engraftment after HSCT. Here, we report the development of a novel mouse model of Shwachman-Diamond Syndrome (SDS) driven by conditional Sbds deletion, which demonstrates profound impairment of healthy donor hematopoietic engraftment after HSCT due to pathway-specific dysfunctional signaling within SBDS-deficient recipient niches. We first attempted to delete Sbds specifically in mature osteoblasts by crossing Sbdsfl/flmice with Col1a1Cre+mice. However, the Col1a1CreSbdsExc progenies are embryonic lethal at E12-E15 stage due to developmental musculoskeletal abnormalities. Alternatively, we generated an inducible SDS mouse model by crossing Sbdsfl/flmice with Mx1Cre+ mice, and inducing Sbds deletion in Mx1-inducible BM hematopoietic and osteolineage niche cells by polyinosinic-polycytidilic acid (pIpC) administration. Compared with Sbdsfl/flcontrols, Mx1CreSbdsExc mice develop significantly decreased platelet counts, an inverted peripheral blood myeloid/lymphoid cell ratio, and reduced long-term HSC within BM, consistent with stress hematopoiesis seen in BMF and myelodysplastic syndromes. To assess whether inducible SBDS deficiency impacts niche function to engraft donor HSC, we transplanted GFP+ wildtype donor BM into pIpC-treated Mx1CreSbdsExc mice and Sbdsfl/flcontrols after 1100 cGy of total body irradiation (TBI). Following transplantation, Mx1CreSbdsExc recipient mice exhibit significantly higher mortality than controls (Figure 1). The decreased survival was related to primary graft failure, as Mx1CreSbdsExc mice exhibit persistent BM aplasia after HSCT and decreased GFP+ reconstitution in competitive secondary transplantation assays. We next sought to identify the molecular and cellular defects within BM niche cells that contribute to the engraftment deficits in SBDS-deficient mice. We performed RNA-seq analysis on the BM stromal cells from irradiated Mx1CreSbdsExc mice versus controls, and the results revealed that SBDS deficiency in BM niche cells caused disrupted gene expression within osteoclast differentiation, FcγR-mediated phagocytosis, and VEGF signaling pathways. Multiplex ELISA assays showed that the BM niche of irradiated Mx1CreSbdsExc mice expresses lower levels of CXCL12, P-selectin and IGF-1, along with higher levels of G-CSF, CCL3, osteopontin and CCL9 than controls. Together, these results suggest that poor donor HSC engraftment in SBDS-deficient mice is likely caused by alterations in niche-mediated donor HSC homing/retention, bone metabolism, host monocyte survival, signaling within IGF-1 and VEGF pathways, and an increased inflammatory state within BM niches. Moreover, flow cytometry analysis showed that compared to controls, the BM niche of irradiated Mx1CreSbdsExc mice contained far fewer megakaryocytes, a hematopoietic cell component of BM niches that we previously demonstrated to be critical in promoting osteoblastic niche expansion and donor HSC engraftment. Taken together, our data demonstrated that SBDS deficiency in BM niches results in reduced capacity to engraft donor HSC. We have identified multiple molecular and cellular defects in the SBDS-deficient niche contributing to this phenotype. Such niche signaling pathway-specific deficits implicate these pathways as critical for donor engraftment during HSCT, and suggest their potential role as targets of therapeutic approaches to enhance donor engraftment and improve HSCT outcome in any condition for which HSCT is required for cure. Disclosures Olson: Merck: Membership on an entity's Board of Directors or advisory committees; Bluebird Bio: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Miltenyi: Honoraria.

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