title: The AML1-ETO fusion gene promotes extensive self-renewal of human primary erythroid cells.
abstract: The t(8;21) translocation, which encodes the AML1-ETO fusion protein (now known as RUNX1-CBF2T1), is one of the most frequent translocations in acute myeloid leukemia, although its role in leukemogenesis is unclear. Here, we report that exogenous expression of AML1-ETO in human CD34(+) cells severely disrupts normal erythropoiesis, resulting in virtual abrogation of erythroid colony formation. In contrast, in bulk liquid culture of purified erythroid cells, we found that while AML1-ETO initially inhibited proliferation during early (erythropoietin [EPO]-independent) erythropoiesis, growth inhibition gave way to a sustained EPO-independent expansion of early erythroid cells that continued for more than 60 days, whereas control cultures became growth arrested after 10 to 13 days (at the EPO-dependent stage of development). Phenotypic analysis showed that although these cells were CD13(-) and CD34(-), unlike control cultures, these cells failed to up-regulate CD36 or to down-regulate CD33, suggesting that expression of AML1-ETO suppressed the differentiation of these cells and allowed extensive self-renewal to occur. In the early stages of this expansion, addition of EPO was able to promote both phenotypic (CD36(+), CD33(-), glycophorin A(+)) and morphologic differentiation of these cells, almost as effectively as in control cultures. However, with extended culture, cells expressing AML1-ETO became refractory to addition of this cytokine, suggesting that a block in differentiation had been established. These data demonstrate the capacity of AML1-ETO to promote the self-renewal of human hematopoietic cells and therefore support a causal role for t(8;21) translocations in leukemogenesis.
authors.affiliation: Department of Haematology, University of Wales College of Medicine, Cardiff, United Kingdom. tonksa@cf.ac.uk
authors.forename: Alex
authors.initials: A
authors.lastname: Tonks
authors.forename: Lorna
authors.initials: L
authors.lastname: Pearn
authors.forename: Amanda J
authors.initials: AJ
authors.lastname: Tonks
authors.forename: Laurence
authors.initials: L
authors.lastname: Pearce
authors.forename: Terry
authors.initials: T
authors.lastname: Hoy
authors.forename: Sarah
authors.initials: S
authors.lastname: Phillips
authors.forename: Janet
authors.initials: J
authors.lastname: Fisher
authors.forename: James R
authors.initials: JR
authors.lastname: Downing
authors.forename: Alan K
authors.initials: AK
authors.lastname: Burnett
authors.forename: Richard L
authors.initials: RL
authors.lastname: Darley
mesh_terms: D018952:Antigens, CD34; D018929:Cell Culture Techniques; D002453:Cell Cycle / Q000187:drug effects; D002454:Cell Differentiation / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D050676:Core Binding Factor Alpha 2 Subunit; D004900:Erythroblasts / Q000166:cytology / Q000187:drug effects; D015672:Erythroid Precursor Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D004920:Erythropoiesis / Q000187:drug effects; D005312:Fetal Blood; D006801:Humans; D007938:Leukemia / Q000209:etiology; D015514:Oncogene Proteins, Fusion / Q000235:genetics / Q000494:pharmacology*; D000075142:RUNX1 Translocation Partner 1 Protein; D014157:Transcription Factors / Q000235:genetics / Q000494:pharmacology*; D014161:Transduction, Genetic
chemical_list: C107844:AML1-ETO fusion protein, human; D018952:Antigens, CD34; D050676:Core Binding Factor Alpha 2 Subunit; D015514:Oncogene Proteins, Fusion; D000075142:RUNX1 Translocation Partner 1 Protein; D014157:Transcription Factors