title: The effects of human FLT3 ligand on in vitro human megakaryocytopoiesis.
abstract: The human homolog of the murine flt3/flk2 gene product is a tyrosine kinase receptor that plays a role in regulating the proliferation and differentiation of cells in the hematopoietic system. Using a plasma-clot clonal assay and a long-term bone marrow culture (LTBMC) system, we studied the effects of the recently cloned human flt3 ligand (FL) alone and in combination with granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin-3 (IL-3), or stem cell factor (c-kit ligand [KL]) on human megakaryocytopoiesis. The effects of FL on the primitive megakaryocyte (MK) progenitor cell, the burst-forming unit-megakaryocyte (BFU-MK), and the more differentiated colony-forming unit-megakaryocyte (CFU-MK) were determined. FL alone had no megakaryocytic colony-stimulating activity (MK-CSA), but was capable of augmenting the MK-CSA of both GM-CSF and IL-3. FL synergized with IL-3 at the level of both CFU-MK and BFU-MK and with GM-CSF and KL at the level of CFU-MK. Although FL alone exhibited a limited potential in sustaining long-term megakaryocytopoiesis in vitro, it synergistically augmented the ability of IL-3 and KL, alone or in association, to promote long-term megakaryocytopoiesis. These data indicate that multiple cytokines are necessary to optimally stimulate the proliferation of both classes of MK progenitor cells and that FL plays a significant role in this process by amplifying the MK-CSA of GM-CSF, IL-3, and KL.
authors.affiliation: Department of Biomedical Sciences and Human Oncology, Medical School of Torino, Italy.
authors.forename: W
authors.initials: W
authors.lastname: Piacibello
authors.forename: L
authors.initials: L
authors.lastname: Garetto
authors.forename: F
authors.initials: F
authors.lastname: Sanavio
authors.forename: A
authors.initials: A
authors.lastname: Severino
authors.forename: L
authors.initials: L
authors.lastname: Fubini
authors.forename: A
authors.initials: A
authors.lastname: Stacchini
authors.forename: G
authors.initials: G
authors.lastname: Dragonetti
authors.forename: M
authors.initials: M
authors.lastname: Aglietta
mesh_terms: D001854:Bone Marrow Cells; D002454:Cell Differentiation / Q000187:drug effects; D002478:Cells, Cultured; D004357:Drug Synergism; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000494:pharmacology; D006410:Hematopoiesis / Q000187:drug effects*; D006801:Humans; D007377:Interleukin-3 / Q000494:pharmacology; D008533:Megakaryocytes / Q000187:drug effects*; D008565:Membrane Proteins / Q000494:pharmacology*; D011518:Proto-Oncogene Proteins / Q000187:drug effects* / Q000502:physiology; D020794:Receptor Protein-Tyrosine Kinases / Q000187:drug effects* / Q000502:physiology; D019089:Stem Cell Factor / Q000494:pharmacology; D051941:fms-Like Tyrosine Kinase 3
chemical_list: D007377:Interleukin-3; D008565:Membrane Proteins; D011518:Proto-Oncogene 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