title: Regulation of colony forming cell generation by flt-3 ligand.
abstract: The recently cloned ligand for the flt-3/flk-2 receptor was examined for its effect on colony formation by subpopulations of CD34+ cells including the least mature CD34+lin-CD38- small-medium lymphocyte-sized cell population. Flt-3 ligand (flt-3l) had little or no effect when added alone to cells. Isolated CD34+lin+ cells formed increased numbers of colony-forming cells (CFC) when flt-3l was added together with IL-3, IL-6, G-CSF, GM-CSF or c-kit ligand (KL), or with the combination of IL-3 and KL. Significant increases in CFC formation from CD34+lin- cells were consistently seen when flt-3l was added to the IL-3 and KL combination, with variable effects observed when it was added to individual growth factors. Studies of the generation of CFC from CD34+lin- cells in liquid cultures showed that cultures containing IL-3 and KL continued to produce CFC after 3 weeks of culture, whereas cultures with IL-3, KL and flt-3l produced few CFC past 2 weeks of culture. Flt-3l alone or the combination of IL-3 and KL did not stimulate significant growth of CD34+lin-CD38- small-medium lymphocyte-sized cells, although these cells reproducibly generated CFC when grown in the combination of IL-1 beta, IL-3, IL-6, G-CSF, GM-CSF and KL. Addition of flt-3l to either IL-3 and KL or to a combination of growth factors induced increased CFC in three of four experiments. These data therefore demonstrate a role for flt-3l in the induction of myelopoiesis by haemopoietic precursors, including the least mature subpopulation population of CD34+ cells.
authors: Division of Pediatric Oncology, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA.
authors: C
authors: C
authors: Brashem-Stein
authors: D A
authors: DA
authors: Flowers
authors: I D
authors: ID
authors: Bernstein
mesh_terms: D018952:Antigens, CD34; D002455:Cell Division; D003114:Colony-Forming Units Assay; D016179:Granulocyte Colony-Stimulating Factor / Q000494:pharmacology; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000494:pharmacology; D006412:Hematopoietic Stem Cells / Q000166:cytology* / Q000502:physiology; D006801:Humans; D007375:Interleukin-1 / Q000494:pharmacology; D007377:Interleukin-3 / Q000494:pharmacology; D015850:Interleukin-6 / Q000494:pharmacology; D008214:Lymphocytes / Q000166:cytology*; D008565:Membrane Proteins / Q000494:pharmacology*; D019089:Stem Cell Factor / Q000494:pharmacology
chemical_list: D018952:Antigens, CD34; D007375:Interleukin-1; D007377:Interleukin-3; D015850:Interleukin-6; D008565:Membrane Proteins; D019089:Stem Cell Factor; C084881:flt3 ligand protein; D016179:Granulocyte Colony-Stimulating Factor; D016178:Granulocyte-Macrophage Colony-Stimulating Factor