title: Effect of flt3 ligand on the ex vivo expansion of human CD34+ hematopoietic progenitor cells.
abstract: A ligand for the tyrosine kinase receptor flt3/flk-2, referred to here as flt3 ligand (flt3L), was recently cloned. The effect of flt3L on purified human CD34+ progenitor cells was examined. flt3 receptor (flt3R) was detected on the surface of human bone marrow cells that were enriched for CD34 expression. The effects of flt3L and the c-kit ligand Steel factor (SLF) on hematopoietic progenitors were compared in clonal colony assays. Both factors synergized with Pixy321 (interleukin-3 [IL-3]-granulocyte-macrophage colony-stimulating factor fusion protein) to induce granulocytic-monocytic (GM) and high proliferative potential (HPP) colonies and synergized with Pixy321 + erythropoietin (EPO) to induce multipotent granulocytic-erythroid-monocytic-megakaryocytic colonies. Although SLF had a potent effect on colony formation of erythroid restricted progenitor cells (burst-forming unit-erythroid), no effect by flt3L was observed. The addition of flt3L to irradiated long-term marrow cultures seeded with CD34+ cells augmented both total and progenitor cell production. Ex vivo expansion studies with isolated CD34+ bone marrow cells from normal donors showed that flt3L alone supported maintenance of both GM and HPP progenitors for 3 to 4 weeks in vitro. The addition of flt3L to a growth factor combination of IL-1 alpha + IL-3 + IL-6 + EPO resulted in a synergistic effect on progenitor cell expansion comparable to that observed with the addition of SLF to IL-1 alpha + IL-3 + IL-6 + EPO. These data show a function for flt3L in the regulation of both primitive multipotent and lineage-committed hematopoietic progenitor cells.
authors.affiliation: Immunex Corp, Seattle, WA 98101, USA.
authors.forename: H J
authors.initials: HJ
authors.lastname: McKenna
authors.forename: P
authors.initials: P
authors.lastname: de Vries
authors.forename: K
authors.initials: K
authors.lastname: Brasel
authors.forename: S D
authors.initials: SD
authors.lastname: Lyman
authors.forename: D E
authors.initials: DE
authors.lastname: Williams
mesh_terms: D018952:Antigens, CD34; D001854:Bone Marrow Cells; D002455:Cell Division / Q000187:drug effects; D003114:Colony-Forming Units Assay; D004357:Drug Synergism; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000494:pharmacology; D016298:Hematopoietic Cell Growth Factors / Q000494:pharmacology; D006412:Hematopoietic Stem Cells / Q000187:drug effects*; D006801:Humans; D007377:Interleukin-3 / Q000494:pharmacology; D008565:Membrane Proteins / Q000494:pharmacology*; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational; D011518:Proto-Oncogene Proteins / Q000502:physiology; D020794:Receptor Protein-Tyrosine Kinases / Q000502:physiology; D011993:Recombinant Fusion Proteins / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects*; D019089:Stem Cell Factor / Q000494:pharmacology; D051941:fms-Like Tyrosine Kinase 3
chemical_list: D018952:Antigens, CD34; D016298:Hematopoietic Cell Growth Factors; D007377:Interleukin-3; D008565:Membrane Proteins; C078524:PIXY321 fusion protein, recombinant; D011518:Proto-Oncogene Proteins; D011993:Recombinant Fusion Proteins; D019089:Stem Cell Factor; C084881:flt3 ligand protein; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; C497970:FLT3 protein, human; D020794:Receptor Protein-Tyrosine Kinases; D051941:fms-Like Tyrosine Kinase 3