title: Differential cytokine effects on primitive (CD34+CD38-) human hematopoietic cells: novel responses to Flt3-ligand and thrombopoietin.
abstract: A high proportion of the CD34+CD38- cells in normal human marrow are defined as long-term culture-initiating cells (LTC-IC) because they can proliferate and differentiate when co-cultured with cytokine-producing stromal feeder layers. In contrast, very few CD34+CD38- cells will divide in cytokine-containing methylcellulose and thus are not classifiable as direct colony-forming cells (CFC), although most can proliferate in serum-free liquid cultures containing certain soluble cytokines. Analysis of the effects of 16 cytokines on CD34+CD38- cells in the latter type of culture showed that Flt3-ligand (FL), Steel factor (SF), and interleukin (IL)-3 were both necessary and sufficient to obtain an approximately 30-fold amplification of the input LTC-IC population within 10 d. As single factors, only FL and thrombopoietin (TPO) stimulated a net increase in LTC-IC within 10 d. Interestingly, a significantly increased proportion of the CFC produced from the TPO-amplified LTC-IC were erythroid. Increases in the number of directly detectable CFC of > 500-fold were also obtainable within 10 d in serum-free cultures of CD34+CD38- cells. However, this required the presence of IL-6 and/or granulocyte/colony-stimulating factor and/or nerve growth factor beta in addition to FL, SF, and IL-3. Also, for this response, the most potent single-acting factor tested was IL-3, not FL. Identification of cytokine combinations that differentially stimulate primitive human hematopoietic cell self-renewal and lineage determination should facilitate analysis of the intracellular pathways that regulate these decisions as well as the development of improved ex vivo expansion and gene transfer protocols.
authors.affiliation: Terry Fox Laboratory, British Columbia Cancer Agency, Vancouver, Canada.
authors.forename: A L
authors.initials: AL
authors.lastname: Petzer
authors.forename: P W
authors.initials: PW
authors.lastname: Zandstra
authors.forename: J M
authors.initials: JM
authors.lastname: Piret
authors.forename: C J
authors.initials: CJ
authors.lastname: Eaves
mesh_terms: D036541:ADP-ribosyl Cyclase; D051997:ADP-ribosyl Cyclase 1; D015703:Antigens, CD; D018952:Antigens, CD34 / Q000276:immunology*; D000943:Antigens, Differentiation / Q000276:immunology*; D001854:Bone Marrow Cells; D002455:Cell Division; D002478:Cells, Cultured; D003114:Colony-Forming Units Assay; D016207:Cytokines / Q000494:pharmacology*; D006410:Hematopoiesis; D006412:Hematopoietic Stem Cells / Q000187:drug effects / Q000276:immunology*; D006801:Humans; D007377:Interleukin-3 / Q000494:pharmacology; D007700:Kinetics; D008213:Lymphocyte Activation; D008214:Lymphocytes / Q000187:drug effects / Q000276:immunology*; D008562:Membrane Glycoproteins; D008565:Membrane Proteins / Q000494:pharmacology*; D009699:N-Glycosyl Hydrolases / Q000276:immunology*; D019089:Stem Cell Factor / Q000494:pharmacology; D013926:Thrombopoietin / Q000494:pharmacology*
chemical_list: D015703:Antigens, CD; D018952:Antigens, CD34; D000943:Antigens, Differentiation; D016207:Cytokines; D007377:Interleukin-3; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D019089:Stem Cell Factor; C084881:flt3 ligand protein; D013926:Thrombopoietin; D009699:N-Glycosyl Hydrolases; D036541:ADP-ribosyl Cyclase; C498154:CD38 protein, human; D051997:ADP-ribosyl Cyclase 1