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- Karlsson, Göran, et al.
(author)
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The Tetraspanin CD9 Affords High-Purity Capture of All Murine Hematopoietic Stem Cells
- 2013
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In: Cell Reports. - : Elsevier BV. - 2211-1247. ; 4:4, s. 642-648
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Journal article (peer-reviewed)abstract
- Prospective isolation is critical for understanding the cellular and molecular aspects of stem cell heterogeneity. Here, we identify the cell surface antigen CD9 as a positive marker that provides a simple alternative for hematopoietic stem cell isolation at high purity. Crucially, CD9 affords the capture of all hematopoietic stem cells in murine bone marrow in the absence of contaminating populations that lack authentic stem cell function. Using CD9 as a tool to subdivide hematopoietic stem-cell-containing populations, we provide evidence for heterogeneity at the cellular, functional, and molecular levels.
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- Kharazi, Shabnam, et al.
(author)
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Impact of gene dosage, loss of wild-type allele, and FLT3 ligand on Flt3-ITD-induced myeloproliferation
- 2011
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In: Blood. - : American Society of Hematology. - 1528-0020 .- 0006-4971. ; 118:13, s. 3613-3621
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Journal article (peer-reviewed)abstract
- Acquisition of homozygous activating growth factor receptor mutations might accelerate cancer progression through a simple gene-dosage effect. Internal tandem duplications (ITDs) of FLT3 occur in approximately 25% cases of acute myeloid leukemia and induce ligand-independent constitutive signaling. Homozygous FLT3-ITDs confer an adverse prognosis and are frequently detected at relapse. Using a mouse knockin model of Flt3-internal tandem duplication (Flt3-ITD)-induced myeloproliferation, we herein demonstrate that the enhanced myeloid phenotype and expansion of granulocyte-monocyte and primitive Lin(-)Sca1(+)c-Kit(+) progenitors in Flt3-ITD homozygous mice can in part be mediated through the loss of the second wild-type allele. Further, whereas autocrine FLT3 ligand production has been implicated in FLT3-ITD myeloid malignancies and resistance to FLT3 inhibitors, we demonstrate here that the mouse Flt3(ITD/ITD) myeloid phenotype is FLT3 ligand-independent. (Blood. 2011; 118(13):3613-3621)
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- Reckzeh, Kristian
(author)
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Deciphering the Pathogenesis of Acute Myeloid Leukemia
- 2012
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Doctoral thesis (other academic/artistic)abstract
- Acute myeloid leukemia (AML) is a malignant disorder of the blood system. Hematopoietic stem cells (HSCs) supply and maintain this system by differentiating via intermediates into lineage-restricted progenitors that strongly proliferate to keep up with the high turn-over of mature blood cells. In AML, the mechanisms controlling differentiation and proliferation of myeloid cells are disturbed leading to the accumulation of undifferentiated cells that interfere with the production of normal blood cells. Mutations of the transcription factor C/EBPα have been observed in 10 percent in AML with normal cytogenetics. In addition, internal tandem duplications (ITD) of FLT3 are frequently observed alterations in AML and coincide with mutations of C/EBPα. The effects of FLT3-ITD cooperation with C/EBPα mutations in AML are not fully understood. To address this, knockin mouse strains harboring different Cebpa mutations and Flt3-ITD were used to generate an AML mouse model. This model demonstrated a block at the transition from pGMP to GMP due to disrupted C/EBPα function. The cooperative effect of FLT3-ITD is composed of enhancing the generation of leukemia-initiating GMPs and activation of STAT5 targets. In in vitro studies it was demonstrated that FLT3-ITD reduces the cytokine-requirements for cell growth and that leukemic cells harboring FLT3-ITD are more sensitive to inhibition of the FLT3 pathway in vitro. To address the impact of FLT3-ITD gene dosage and loss of Flt3 wild type allele in vivo the Flt3-ITD knockin mouse was crossed to the Flt3 receptor knockout mouse. These studies demonstrated that the myeloproliferative phenotype was FLT3-ITD dosage-dependent and independent of FL. In summary, the data presented provide deeper insights into oncogene cooperation and FLT3-ITD dosage in AML.
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- Reckzeh, Kristian, et al.
(author)
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Molecular and cellular effects of oncogene cooperation in a genetically accurate AML mouse model.
- 2012
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In: Leukemia. - : Springer Science and Business Media LLC. - 1476-5551 .- 0887-6924. ; 26:7, s. 1527-1536
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Journal article (peer-reviewed)abstract
- Biallelic CEBPA mutations and FLT3 length mutations are frequently identified in human acute myeloid leukemia (AML) with normal cytogenetics. However, the molecular and cellular mechanisms of oncogene cooperation remain unclear due to a lack of disease models. We have generated an AML mouse model using knockin mouse strains to study cooperation of internal tandem duplication (ITD) mutation in the Flt3 gene with commonly observed C/EBPα mutations. This study provides evidence that FLT3 ITD cooperates in leukemogenesis by enhancing the generation of leukemia-initiating granulocyte-monocyte progenitors (GMP) otherwise prevented by a block in differentiation and skewed lineage priming induced by biallelic C/EBPα mutations. These cellular changes are accompanied by an upregulation of hematopoietic stem cell and STAT5 target genes. By gene expression analysis in premalignant populations we further show a role of FLT3 ITD in activating genes involved in survival/transformation and chemoresistance. Both multipotent progenitors (MPP) and GMP cells contain the potential to induce AML similar to corresponding cells in human AML samples showing that this model resembles human disease.Leukemia accepted article preview online, 9 February 2012; doi:10.1038/leu.2012.37.
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- Reckzeh, Kristian, et al.
(author)
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Molecular mechanisms underlying deregulation of C/EBP alpha in acute myeloid leukemia
- 2010
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In: International Journal of Hematology. - : Springer Science and Business Media LLC. - 0925-5710 .- 1865-3774. ; 91:4, s. 557-568
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Research review (peer-reviewed)abstract
- The CEBPA gene encodes a transcription factor protein that is crucial for granulocytic differentiation, regulation of myeloid gene expression and growth arrest. Mutations in one or both alleles of CEBPA are observed in about 10% of patients with acute myeloid leukemia (AML). Moreover, other genetic events associated with AML have been identified to deregulate C/EBP alpha expression and function at various levels. Recently developed mouse models that accurately mimic the genetic C/EBP alpha alterations in human AML demonstrate C/EBP alpha's gatekeeper function in the control of self-renewal and lineage commitment of hematopoietic stem cells (HSCs). Moreover, these studies indicate that CEBPA mutations affect HSCs in early leukemia development by inducing proliferation and limiting their lineage potential. However, the exact relationship between 'pre-leukemic' HCSs and those cells that finally initiate leukemia (leukemia-initiating cells) with disturbed differentiation and aberrant proliferation remains elusive. More research is needed to identify and characterize these functionally distinct populations and the exact role of the different genetic alterations in the process of leukemia initiation and maintenance.
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