scholarly journals Alpha 4 beta 1 and alpha 5 beta 1 are differentially expressed during myelopoiesis and mediate the adherence of human CD34+ cells to fibronectin in an activation-dependent way

Blood ◽  
1993 ◽  
Vol 81 (2) ◽  
pp. 344-351 ◽  
Author(s):  
JM Kerst ◽  
JB Sanders ◽  
IC Slaper-Cortenbach ◽  
MC Doorakkers ◽  
B Hooibrink ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Progenitor Cells ◽  
Bone Marrow Cells ◽  
Binding Capacity ◽  
Differentially Expressed ◽  
Myeloid Differentiation ◽  
Erythroid Progenitor ◽  
Fibronectin Binding ◽  
Marrow Cells

To study the receptors involved in the interaction between extracellular matrix proteins and hematopoietic progenitor cells, we analyzed the expression of beta 1 integrins on CD34+ bone marrow cells by means of immunoflowcytometry. Alpha 4 beta 1 and alpha 5 beta 1 were expressed, whereas alpha 1 beta 1, alpha 2 beta 1, alpha 3 beta 1, alpha 6 beta 1, and alpha v beta 1 were virtually absent. Furthermore, we assessed the alpha 4 and alpha 5 expression on committed myeloid progenitor cells. These colony-forming cells were detected in the alpha 4 dull fraction and the alpha 5 dull fraction. During myeloid differentiation, both in vivo and in vitro, a differential expression of alpha 4 beta 1 and alpha 5 beta 1 was observed. alpha 5 beta 1 was found to be lost at the myelocytic-metamyelocytic stage, before the loss of alpha 4 beta 1, at the band stage. Functional studies showed no binding of erythroid progenitor-depleted, CD34+ bone marrow cells to fibronectin. However, protein kinase C activation strongly induced fibronectin binding (68% of the cells). Inhibition experiments with specific antibodies and peptides showed the binding to be mediated by both alpha 4 beta 1 and alpha 5 beta 1. Also, colony-forming cells of granulocytes and macrophages were demonstrated to adhere to fibronectin in an activation-dependent way. During granulocyte colony-stimulating factor-induced in vitro maturation, the activation-dependent fibronectin binding capacity is gradually lost. We conclude that: (1) CD34+ bone marrow cells express alpha 4 beta 1 and alpha 5 beta 1; (2) the expression of alpha 4 beta 1 and alpha 5 beta 1 is differentially expressed during myeloid differentiation; and (3) binding of CD34+ bone marrow cells to fibronectin is activation dependent.

scholarly journals Alpha 4 beta 1 and alpha 5 beta 1 are differentially expressed during myelopoiesis and mediate the adherence of human CD34+ cells to fibronectin in an activation-dependent way

Blood ◽  
1993 ◽  
Vol 81 (2) ◽  
pp. 344-351 ◽  
Author(s):  
JM Kerst ◽  
JB Sanders ◽  
IC Slaper-Cortenbach ◽  
MC Doorakkers ◽  
B Hooibrink ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Progenitor Cells ◽  
Bone Marrow Cells ◽  
Binding Capacity ◽  
Differentially Expressed ◽  
Myeloid Differentiation ◽  
Erythroid Progenitor ◽  
Fibronectin Binding ◽  
Marrow Cells

Abstract To study the receptors involved in the interaction between extracellular matrix proteins and hematopoietic progenitor cells, we analyzed the expression of beta 1 integrins on CD34+ bone marrow cells by means of immunoflowcytometry. Alpha 4 beta 1 and alpha 5 beta 1 were expressed, whereas alpha 1 beta 1, alpha 2 beta 1, alpha 3 beta 1, alpha 6 beta 1, and alpha v beta 1 were virtually absent. Furthermore, we assessed the alpha 4 and alpha 5 expression on committed myeloid progenitor cells. These colony-forming cells were detected in the alpha 4 dull fraction and the alpha 5 dull fraction. During myeloid differentiation, both in vivo and in vitro, a differential expression of alpha 4 beta 1 and alpha 5 beta 1 was observed. alpha 5 beta 1 was found to be lost at the myelocytic-metamyelocytic stage, before the loss of alpha 4 beta 1, at the band stage. Functional studies showed no binding of erythroid progenitor-depleted, CD34+ bone marrow cells to fibronectin. However, protein kinase C activation strongly induced fibronectin binding (68% of the cells). Inhibition experiments with specific antibodies and peptides showed the binding to be mediated by both alpha 4 beta 1 and alpha 5 beta 1. Also, colony-forming cells of granulocytes and macrophages were demonstrated to adhere to fibronectin in an activation-dependent way. During granulocyte colony-stimulating factor-induced in vitro maturation, the activation-dependent fibronectin binding capacity is gradually lost. We conclude that: (1) CD34+ bone marrow cells express alpha 4 beta 1 and alpha 5 beta 1; (2) the expression of alpha 4 beta 1 and alpha 5 beta 1 is differentially expressed during myeloid differentiation; and (3) binding of CD34+ bone marrow cells to fibronectin is activation dependent.

scholarly journals Association of cell cycle expression of Ia-like antigenic determinations on normal human multipotential (CFU-GEMM) and erythroid (BFU-E) progenitor cells with regulation in vitro by acidic isoferritins

Blood ◽  
1983 ◽  
Vol 61 (2) ◽  
pp. 250-256 ◽  
Author(s):  
L Lu ◽  
HE Broxmeyer ◽  
PA Meyers ◽  
MA Moore ◽  
HT Thaler
Keyword(s):  
Bone Marrow ◽  
Progenitor Cells ◽  
Colony Formation ◽  
Bone Marrow Cells ◽  
Tritiated Thymidine ◽  
Antigenic Determinants ◽  
Erythroid Progenitor ◽  
Ia Antigen ◽  
Marrow Cells

Abstract An association has been established between human Ia-like antigenic determinants, expression during DNA synthesis on multipotential (CFU- GEMM) and erythroid (BFU-E) progenitor cells, and the regulatory action of acidic isoferritins in vitro. Treatment of human bone marrow cells with monoclonal anti-Ia (NE1–011) plus complement inhibited colony formation of CFU-GEMM) and BFU-E by 50%-70%. Reduction of colonies was similar whether bone marrow cells were exposed to anti-Ia plus complement, high specific tritiated thymidine (3HTdr), or acidic isoferritins. No further decrease was apparent with 3HTdr or acidic isoferritins after Ia-antigen+ CFU-GEMM or BFU-E were removed, or with anti-Ia plus complement or acidic isoferritins after S-phase CFU-GEMM or BFU-E were removed. Anti-Ia, in the absence of complement, had no effect on colony formation but blocked the inhibition of CFU-GEMM and BFU-E by acidic isoferritins. Demonstration of Ia-antigens on BFU-E and inhibition of BFU-E by acidic isoferritins appeared to require the presence of phytohemmagglutinin leukocyte conditioned medium (PHA-LCM) in the culture medium during the 14-day incubation period. these results implicate Ia-antigen+ cells, acidic isoferritins, and PHA-LCM in the regulation of multipotential and erythroid progenitor cells in vitro.

scholarly journals Association of cell cycle expression of Ia-like antigenic determinations on normal human multipotential (CFU-GEMM) and erythroid (BFU-E) progenitor cells with regulation in vitro by acidic isoferritins

Blood ◽  
1983 ◽  
Vol 61 (2) ◽  
pp. 250-256
Author(s):  
L Lu ◽  
HE Broxmeyer ◽  
PA Meyers ◽  
MA Moore ◽  
HT Thaler
Keyword(s):  
Bone Marrow ◽  
Progenitor Cells ◽  
Colony Formation ◽  
Bone Marrow Cells ◽  
Tritiated Thymidine ◽  
Antigenic Determinants ◽  
Erythroid Progenitor ◽  
Ia Antigen ◽  
Marrow Cells

An association has been established between human Ia-like antigenic determinants, expression during DNA synthesis on multipotential (CFU- GEMM) and erythroid (BFU-E) progenitor cells, and the regulatory action of acidic isoferritins in vitro. Treatment of human bone marrow cells with monoclonal anti-Ia (NE1–011) plus complement inhibited colony formation of CFU-GEMM) and BFU-E by 50%-70%. Reduction of colonies was similar whether bone marrow cells were exposed to anti-Ia plus complement, high specific tritiated thymidine (3HTdr), or acidic isoferritins. No further decrease was apparent with 3HTdr or acidic isoferritins after Ia-antigen+ CFU-GEMM or BFU-E were removed, or with anti-Ia plus complement or acidic isoferritins after S-phase CFU-GEMM or BFU-E were removed. Anti-Ia, in the absence of complement, had no effect on colony formation but blocked the inhibition of CFU-GEMM and BFU-E by acidic isoferritins. Demonstration of Ia-antigens on BFU-E and inhibition of BFU-E by acidic isoferritins appeared to require the presence of phytohemmagglutinin leukocyte conditioned medium (PHA-LCM) in the culture medium during the 14-day incubation period. these results implicate Ia-antigen+ cells, acidic isoferritins, and PHA-LCM in the regulation of multipotential and erythroid progenitor cells in vitro.

Enhanced endothelialization and microvessel formation in polyester grafts seeded with CD34+ bone marrow cells

Blood ◽  
2000 ◽  
Vol 95 (2) ◽  
pp. 581-585 ◽  
Author(s):  
Vishwanath Bhattacharya ◽  
Peter A. McSweeney ◽  
Qun Shi ◽  
Benedetto Bruno ◽  
Atsushi Ishida ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Progenitor Cells ◽  
Vascular Graft ◽  
Bone Marrow Cells ◽  
Venous Blood ◽  
Immunomagnetic Bead ◽  
Composite Grafts ◽  
Cd34 Cells ◽  
Marrow Cells

The authors have shown accelerated endothelialization on polyethylene terephthalate (PET) grafts preclotted with autologous bone marrow. Bone marrow cells have a subset of early progenitor cells that express the CD34 antigen on their surfaces. A recent in vitro study has shown that CD34+ cells can differentiate into endothelial cells. The current study was designed to determine whether CD34+ progenitor cells would enhance vascular graft healing in a canine model. The authors used composite grafts implanted in the dog's descending thoracic aorta (DTA) for 4 weeks. The 8-mm × 12-cm composite grafts had a 4-cm PET graft in the center and 4-cm standard ePTFE grafts at each end. The entire composite was coated with silicone rubber to make it impervious; thus, the PET segment was shielded from perigraft and pannus ingrowth. There were 5 study grafts and 5 control grafts. On the day before surgery, 120 mL bone marrow was aspirated, and CD34+ cells were enriched using an immunomagnetic bead technique, yielding an average of 11.4 ± 5.3 × 106. During surgery, these cells were mixed with venous blood and seeded onto the PET segment of composite study grafts; the control grafts were treated with venous blood only. Hematoxylin and eosin, immunocytochemical, and AgNO3staining demonstrated significant increases of surface endothelialization on the seeded grafts (92% ± 3.4% vs 26.6% ± 7.6%; P = .0001) with markedly increased microvessels in the neointima, graft wall, and external area compared with controls. In dogs, CD34+ cell seeding enhances vascular graft endothelialization; this suggests practical therapeutic applications.

Requirement for p85α Regulatory Subunit of Class IA PI3Kinase and Rac2 GTPase in Myeloproliferative Disease Driven by Activation Loop Mutant of KIT.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 89-89
Author(s):  
Veerendra Munugalavadla ◽  
Emily C. Sims ◽  
Stephen D. Lenz ◽  
Reuben Kapur
Keyword(s):  
Bone Marrow ◽  
Mast Cells ◽  
Progenitor Cells ◽  
Bone Marrow Cells ◽  
Regulatory Subunit ◽  
Activation Loop ◽  
Myeloproliferative Disease ◽  
Hematopoietic Stem ◽  
Marrow Cells

Abstract Oncogenic activation-loop mutants of KIT, the receptor for stem cell factor (SCF), are commonly observed in acute myeloid leukemia (AML) and systemic mastocytosis (SM); however, unlike the KIT juxtamembrane mutants (found in patients with gastrointestinal stromal tumors [GISTs]), the activation-loop mutants are commonly insensitive to inhibition by tyrosine kinase inhibitors. Furthermore, little is known about the signaling pathways that contribute to oncogenic KIT-induced transformation in SM or AML. We demonstrate that expression of KITD814V (KIT activation-loop mutant) in primary hematopoietic stem and progenitor cells induces constitutive KIT autophosphorylation, promotes ligand-independent hyperproliferation, skews myeloid differentiation towards the granulocytic lineage, and promotes promiscuous cooperation with multiple cytokines, including G-CSF, M-CSF and IL-3. KITD814V expressing primary mast cells also demonstrated hyperproliferation in response to SCF, IL-3, IL-4 and IL-10. Biochemical analyses of KITD814V expressing cells revealed constitutively elevated levels of phosphatidylinositol-3-kinase (PI3K) and its downstream substrate, the Rho family GTPase Rac. Genetic disruption of p85a, the regulatory subunit of class IA PI-3Kinase, but not of p85β, or genetic disruption of the hematopoietic cell-specific Rho GTPase, Rac2, normalized KITD814V-induced ligand independent hyperproliferation in vitro. Additionally, deficiency of p85α or Rac2 corrected the promiscuous hyperproliferation observed in response to multiple cytokines in both KITD814V expressing stem/progenitor cells as well as mast cells in vitro. Although p85α is hyperphosphorylated and constitutively bound to KITD814V in bone marrow cells in vitro; its physiologic role in transformation in vivo is not known. To address this, we generated a new mouse model to study KITD814V induced transformation in myeloid cells as opposed to previously described models that primarily result in the generation of phenotypes resembling acute lymphocytic leukemia via this mutation. Our results show that transplantation of KITD814V expressing bone marrow cells from C57/BL6 strain of mice into syngeneic recipients results in a fatal myeloproliferative disease (MPD) characterized by leukocytosis, splenomegaly, disruption of the splenic architecture as well as myeloid cell infiltration in the lung and liver. Importantly, in this model, transplantation of KITD814V expressing p85α deficient bone marrow cells rescued the MPD phenotype, including splenomegaly, peripheral blood leukocytosis and the reduced life span associated with the transplantation of KITD814V expressing wildtype bone marrow cells. Treatment of KITD814V-expressing hematopoietic progenitors with either a Rac inhibitor (NC23766) or rapamycin showed a dose-dependent suppression in KITD814V induced growth. Taken together, our results describe the generation of a new murine transplant model to study KITD814V induced transformation and identify p85a and Rac2 as potential novel therapeutic target for the treatment of KITD814V-bearing diseases including SM and AML.

Functional Role of BAALC In Leukemogenesis

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 4194-4194
Author(s):  
Tobias Berg ◽  
Michael Heuser ◽  
Florian Kuchenbauer ◽  
Gyeongsin Park ◽  
Stephen Fung ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Bone Marrow Cells ◽  
Myeloid Differentiation ◽  
Self Renewal ◽  
Murine Bone Marrow ◽  
Trans Retinoic Acid ◽  
All Trans Retinoic Acid ◽  
Marrow Cells

Abstract Abstract 4194 Cytogenetically normal acute myeloid leukemia (CN-AML) patients with high BAALC or MN1 expression have a poor prognosis. Whereas the oncogenic function of MN1 is well established, the functional role of BAALC in hematopoiesis is not known. We therefore compared the expression of BAALC and MN1 in 140 CN-AML patients by quantitative PCR. To further assess the impact of BAALC on leukemogenesis we used retroviral gene transfer into primary murine bone marrow cells and cells immortalized with NUP98-HOXD13 (ND13) and HOXA9. Transduced cells were assessed in vitro by colony forming assays and for their sensitivity to treatment with all-trans retinoic acid (ATRA). They were also evaluated by in vivo transplantation into lethally-irradiated mice. In the 140 CN-AML patients analyzed, the expression of BAALC and MN1 was highly correlated (R=0.71). Retroviral overexpression of MN1 or BAALC in the Hox gene-immortalized bone marrow cells did not cause upregulation of the other gene, suggesting that these genes do not regulate each other. In murine bone marrow cells BAALC did not immortalize the cells in vitro as assessed by serial replating of transduced cells in methylcellulose assays. Transplantation of transduced cells resulted in negligible engraftment of approximately 1 percent at 4 weeks after transplantation. However, co-transduction of BAALC into NUP98-HOXD13 cells (which are very sensitive to the treatment with all-trans retinoic acid) increased the 50 percent inhibitory concentration (IC50) of ATRA by 4.3-fold, suggesting a negative impact of BAALC on myeloid differentiation. We next evaluated whether the differentiation inhibiting effects of BAALC may cooperate with the self renewal-promoting effects of HOXA9 to induce leukemia in mice. Mice receiving transplants of murine bone marrow cells transduced with BAALC and HOXA9 developed myeloid leukemias with a median latency of 139.5 days that were characterized by leukocytosis, massively enlarged spleens (up to 1.02 g), anemia and thrombocytopenia. Infiltrations of myeloid cells were also found in liver, spleen, and kidney. The disease was transplantable into secondary animals. By Southern blot analysis we found one to two BAALC viral integrations per mouse, suggesting that clonal disease had developed from BAALC-transduced cells. We demonstrate for the first time that BAALC blocks myeloid differentiation and promotes leukemogenesis when combined with the self-renewal promoting oncogene HOXA9. Due to its prognostic and functional effects BAALC may become a valuable therapeutic target in leukemia patients. Disclosures: No relevant conflicts of interest to declare.

scholarly journals NR2F6 (EAR-2) Is a Novel Leukemia Oncogene Whose Cellular Function Is to Regulate Terminal Differentiation of Erythrocytes at the Proerythroblast Stage

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 1337-1337
Author(s):  
Christine Victoria Ichim ◽  
Dzana Dervovic ◽  
David Koos ◽  
Marciano D. Reis ◽  
Alden Chesney ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Stem Cell ◽  
Cell Differentiation ◽  
Bone Marrow Cells ◽  
Erythroid Differentiation ◽  
Erythroid Progenitor ◽  
Over Expression ◽  
Marrow Cells

Abstract The leukemia stem cell model suggests that elucidation of the genes that regulate growth ability within the leukemia cell hierarchy will have important clinical relevance. We showed that the expression of NR2F6 (EAR-2), is greater in clonogenic leukemia single cells than in leukemia cells that do not divide, and that this gene is over-expressed in patients with acute myeloid leukemia and myelodysplastic syndrome. In vivo, overexpression of EAR-2 using a retroviral vector in a chimeric mouse model leads to a condition that resembles myelodysplastic syndrome with hypercellular bone marrow, increased blasts, abnormal localization of immature progenitors, morphological dysplasia of the erythroid lineage and a competitive advantage over wild-type cells, that eventually leads to AML in a subset of the mice, or after secondary-transplantation. Interestingly, animals transplanted with bone marrow that over-expresses EAR-2 develop leukemia that is preceded by expansion of the stem cell compartment in the transplanted mice—suggesting that EAR-2 is an important regulator of hematopoietic stem cell differentiation. Here we report that over-expression of EAR-2 also has a profound effect on the differentiation of erythroid progenitor cells both in vitro and in vivo. Studies of the roles of EAR-2 in normal primary bone marrow cells in vitro showed that overexpression of EAR-2 profoundly impaired differentiation along the erythroid lineage. EAR-2 over-expressing bone marrow cells formed 40% fewer BFU-E colonies, but had greatly extended replating capacity in colony assays. While knockdown of EAR-2 increased the number of cells produced per BFU-E colony 300%. Normal mice transplanted with grafts of purified bone marrow cells that over-expressed EAR-2 developed a rapidly fatal leukemia characterized by pancytopenia, enlargement of the spleen, and infiltration of blasts into the spleen, liver and peripheral blood. Sick animals had profound reduction of peripheral blood cell counts, particularly anemia with a 55% reduction in hemoglobin levels. Anemia was evident even on gross inspection of the blood and the liver in EAR-2 overexpressing animals. Analysis of the leukemic cells revealed an erythroblastic morphology, with the immunophenotype lineageneg, CD71high, TER119med. Hence, we wondered weather EAR-2 caused leukemia by arresting erythroid progenitor cell differentiation. Examination of the bone marrow of pre-leukemic animals showed a four-fold increase in cells with a pro-erythroblastic immunophenotype (CD71highTER119med , region I), and a four-fold decrease in orthochromatophilic erythroblasts (CD71lowTER119high , region IV). We observed no change in the numbers of basophilic erythroblasts (CD71highTER119high , region II) or late basophilic and polychromatophilic erythroblasts (CD71medTER119high, region III). These data suggests that over-expression of EAR-2 blocks erythroid cell differentiation at the pro-erythroblastic stage. Since EAR-2 over-expressing recipients died within 4 week, we wanted to definitively test whether animals had compromised radioprotection. We showed that decreasing the size of the bone marrow graft, reduced survival of the EAR-2 over-expressing cohort by a week, but had no effect on control animals proving that EAR-2 over-expression has a profound effect on erythropoietic reconstitution in vivo. Mechanistically, we show that DNA binding is necessary for EAR-2 function, and that EAR-2 functions in an HDAC-dependent manner, regulating expression of several genes. Pre-leukemic pro-erythroblastic cells (CD71highTER119med) that over-expressed EAR-2 had lower expression of genes involved in erythroid differentiation such as GATA1, EBF1, inhibitor of NFKB (NFKBia), ETV6, CEBP/a, LMO2, and Nfe2, and increased expression of GATA2, GLI1, ID1 and PU.1 than GFP control pro-erythroblasts. These data establish that EAR-2 is a novel oncogene whose cellular function is to regulate terminal differentiation of erythroid cells at the proerythroblastic (CD71highTER119med) stage by deregulating gene expression necessary for erythroid differentiation. Disclosures Ichim: Entest BioMedical: Employment, Equity Ownership, Patents & Royalties, Research Funding. Koos:Entest BioMedical: Employment, Equity Ownership, Patents & Royalties, Research Funding.

scholarly journals Inhibition of Immature Erythroid Progenitor Cell Proliferation by Macrophage Inflammatory Protein-1α by Interacting Mainly With a C-C Chemokine Receptor, CCR1

Blood ◽  
1997 ◽  
Vol 90 (2) ◽  
pp. 605-611 ◽  
Author(s):  
Shao-bo Su ◽  
Naofumi Mukaida ◽  
Jian-bin Wang ◽  
Yi Zhang ◽  
Akiyoshi Takami ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Cell Proliferation ◽  
Progenitor Cells ◽  
Bone Marrow Cells ◽  
Erythroid Progenitor ◽  
Erythroid Progenitor Cells ◽  
Inflammatory Protein ◽  
Cd34 Cells ◽  
Macrophage Inflammatory Protein ◽  
Marrow Cells

Abstract Several lines of evidence indicate that macrophage inflammatory protein-1α (MIP-1α) modulates the proliferation of hematopoietic progenitor cells, depending on their maturational stages. To clarify the mechanisms for the modulation of hematopoiesis by this chemokine, we examined the expression of a receptor for MIP-1α, CCR1, on bone marrow cells of normal individuals using a specific antibody and explored the effects of MIP-1α on in vitro erythropoiesis driven by stem cell factor (SCF) and erythropoietin (Epo). CCR1 was expressed on glycophorin A-positive erythroblasts in addition to lymphocytes and granulocytes. CCR1+ cells, isolated from bone marrow mononuclear cells (BMMNCs) using a cell sorter, comprised virtually all erythroid progenitor cells in the BMMNCs. Moreover, MIP-1α inhibited, in a dose-dependent manner, colony formation by burst-forming unit-erythroid (BFU-E), but not by colony forming unit-erythroid (CFU-E), in a methylcellulose culture of purified human CD34+ bone marrow cells. Although reverse-transcription polymerase chain reaction (RT-PCR) showed the presence of CCR1, CCR4, and CCR5 transcripts in CD34+ cells in BM, anti-CCR1 antibodies significantly abrogated the inhibitory effects of MIP-1α on BFU-E formation both in a methylcellulose culture and in a single cell proliferation assay of purified CD34+ cells. Although the contribution of CCR4 or CCR5 cannot be completely excluded, these results suggest that MIP-1α–mediated suppression of the proliferation of immature, but not mature erythroid progenitor cells, is largely mediated by CCR1 expressed on these progenitor cells.

MN1 Inhibits Myeloid Differentiation by Transcriptional Repression of EGR2

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 229-229
Author(s):  
Michael Heuser ◽  
Eric Yung ◽  
Courteney Lai ◽  
Bob Argiropoulos ◽  
Florian Kuchenbauer ◽  
...  
Keyword(s):  
Gene Expression ◽  
Bone Marrow ◽  
Transcriptional Activation ◽  
Transcriptional Repression ◽  
Target Genes ◽  
Bone Marrow Cells ◽  
Function Analysis ◽  
Myeloid Differentiation ◽  
Marrow Cells

Abstract Abstract 229 Overexpression of MN1 (meningioma 1) is a negative prognostic factor in acute myeloid leukemia (AML) patients with normal cytogenetics, and induces a rapidly lethal AML in mice. We have shown previously that MN1, a transcription cofactor of retinoic acid receptor alpha (RARA), increases resistance to all-trans retinoic acid (ATRA) by greater than 3000-fold in an in-vitro differentiation model. We investigated the molecular mechanisms involved in the MN1-induced myeloid differentiation block by fusing potent transcriptional activation or repression domains to MN1, conducting a structure-function analysis of MN1, gene expression profiling, ChIP-on chip experiments, and functional validation of MN1 target genes. We found that (1) MN1 inhibits myeloid differentiation through transcriptional repression; (2) the C-terminal domain of MN1 is critical for induction of resistance to ATRA; (3) EGR2 is a putative direct target of MN1 and RARA that is repressed in MN1 leukemias; and (4) that constitutive upregulation of EGR2 in MN1 leukemias permits differentiation and prevents engraftment of transplanted cells. To investigate whether MN1 impacts on myeloid differentiation through transcriptional activation or repression we fused a strong transcriptional activation domain (VP16) or repression domain (M33) to MN1. MN1VP16 immortalized murine bone marrow cells, however, these cells could differentiate to mature granulocytes, and succumbed to cell cycle arrest upon treatment with ATRA. Mice receiving transplants of MN1VP16 cells had a median survival of 143 days (n=16) compared to 35 days in mice receiving MN1-transduced cells (n=18; p<.001). Morphologic analysis of bone marrow mostly showed mature granulocytes with less than 20 percent immature forms consistent with a diagnosis of myeloproliferative-like disease. Conversely, mice receiving transplants with cells transduced with the fusion of MN1 to the transcriptional repression domain of M33 (n=7) developed leukemia with a similar latency and phenotype as mice receiving transplants from MN1-transduced cells (survival, P=.6). These data suggest that MN1 inhibits myeloid differentiation by transcriptional repression rather than activation of its target genes. A structure-function analysis was performed to identify the domain(s) of MN1 required to inhibit myeloid differentiation. Consecutive stretches of 200 amino acids of MN1 were interrogated The deletion constructs were subsequently transduced into bone marrow cells immortalized by NUP98-HOXD13 (ND13). ND13 cells are very sensitive to ATRA-induced differentiation and cell cycle arrest with an IC50 of 0.1 μ M, whereas overexpression of MN1 increases resistance greater than 3000-fold. Interestingly, deletion of the 200 C-terminal amino acids of MN1 restored ATRA sensitivity of ND13 cells compared to full-length MN1, suggesting that the C-terminus of MN1 is required for inhibition of myeloid differentiation. To identify MN1-regulated genes important for the myeloid differentiation block we performed gene expression profiling of MN1- and MN1VP16-transduced bone marrow cells. To further identify genes that might be directly regulated by MN1 we performed ChIP-on-chip using anti-MN1 and anti-RARA antibodies. EGR2, CCL5, CMAH, among others, were identified as targets of both MN1 and RARA whose gene expression was low in MN1 but high in MN1VP16 cells. Overexpression of these genes in MN1-transduced leukemic cells was used to validate their function. Blast percentage of in vitro cultured bone marrow cells was 93, 58, 83, and 41 percent in MN1+CTL cells, MN1+EGR2, MN1+CCL5, and MN1+CMAH cells, respectively. MN1+EGR2 cell engraftment in peripheral blood of mice declined from 2.2 percent at 4 weeks to undetectable levels at 8 weeks (n=4), whereas MN1+CCL5 and MN1+CMAH cell engraftment was 23 (n=4) and 26 (n=4) percent at 4 weeks, and 14 and 30 percent at 8 weeks, respectively. At time of death, EGR2 was not detectable in mice whereas leukemias of mice receiving MN1+CCL5 or MN1+CMAH- transduced cells were positive for CCL5 or CMAH, respectively. In conclusion, our data suggest that MN1 inhibits myeloid differentiation by transcriptional repression of a subset of its target genes, and that re-expression of EGR2, a zinc-finger transcription factor, may prevent outgrowth of MN1 leukemias in mice. Pharmacologic activation of EGR2 may become a novel antileukemic strategy. Disclosures: No relevant conflicts of interest to declare.

Sign in / Sign up

Export Citation Format

Share Document