title: In vivo synergy between recombinant human stem cell factor and recombinant human granulocyte colony-stimulating factor in baboons enhanced circulation of progenitor cells.
abstract: Recombinant human stem cell factor (rhSCF) and recombinant human granulocyte colony-stimulating factor (rhG-CSF) are synergistic in vitro in stimulating the proliferation of hematopoietic progenitor cells and their precursors. We examined the in vivo synergy of rhSCF with rhG-CSF for stimulating hematopoiesis in vivo in baboons. Administration of low-dose (LD) rhSCF (25 micrograms/kg) alone did not stimulate changes in circulating WBCs. In comparison, administration of LD rhSCF in combination with rhG-CSF at 10 micrograms/kg or 100 micrograms/kg stimulated increases in circulating WBCs of multiple types up to twofold higher than was stimulated by administration of the same dose of rhG-CSF alone. When the dose of rhG-CSF is increased to 250 micrograms/kg, the administration of LD rhSCF does not further increase the circulating WBC counts. Administration of LD rhSCF in combination with rhG-CSF also stimulated increased circulation of hematopoietic progenitors. LD rhSCF alone stimulated less of an increase in circulating progenitors, per milliliter of blood, than did administration of rhG-CSF alone at 100 micrograms/kg. Baboons administered LD rhSCF together with rhG-CSF at 10, 100, or 250 micrograms/kg had 3.5- to 16-fold higher numbers per milliliter of blood of progenitors cells of multiple types, including colony-forming units granulocyte/macrophage (CFU-GM), burst-forming unit-erythroid (BFU-E), and colony-forming and burst-forming units-megakaryocyte (CFU-MK and BFU-MK) compared with animals given the same dose of rhG-CSF without rhSCF, regardless of the rhG-CSF dose. The increased circulation of progenitor cells stimulated by the combination of rhSCF plus rhG-CSF was not necessarily directly related to the increase in WBCs, as this effect on peripheral blood progenitors was observed even at an rhG-CSF dose of 250 micrograms/kg, where coadministration of LD rhSCF did not further increase WBC counts. Administration of very-low-dose rhSCF (2.5 micrograms/kg) with rhG-CSF, 10 micrograms/kg, did not stimulate increases in circulating WBCs, but did increase the number of megakaryocyte progenitor cells in blood compared with rhG-CSF alone. LD rhSCF administered alone for 7 days before rhG-CSF did not result in increased levels of circulating WBCs or progenitors compared with rhG-CSF alone. Thus, the synergistic effects of rhSCF with rhG-CSF were both dose- and time-dependent. The doses of rhSCF used in these studies have been tolerated in vivo in humans.(ABSTRACT TRUNCATED AT 400 WORDS)
authors.affiliation: Clinical Research Division, Fred Hutchinson Cancer Research Center, Seattle, WA 98104.
authors.forename: R G
authors.initials: RG
authors.lastname: Andrews
authors.forename: R A
authors.initials: RA
authors.lastname: Briddell
authors.forename: G H
authors.initials: GH
authors.lastname: Knitter
authors.forename: T
authors.initials: T
authors.lastname: Opie
authors.forename: M
authors.initials: M
authors.lastname: Bronsden
authors.forename: D
authors.initials: D
authors.lastname: Myerson
authors.forename: F R
authors.initials: FR
authors.lastname: Appelbaum
authors.forename: I K
authors.initials: IK
authors.lastname: McNiece
mesh_terms: D000818:Animals; D015703:Antigens, CD / Q000032:analysis; D018952:Antigens, CD34; D004357:Drug Synergism; D016179:Granulocyte Colony-Stimulating Factor / Q000008:administration & dosage*; D006400:Hematocrit; D006410:Hematopoiesis / Q000187:drug effects*; D016298:Hematopoietic Cell Growth Factors / Q000008:administration & dosage*; D006412:Hematopoietic Stem Cells / Q000378:metabolism; D007958:Leukocyte Count / Q000187:drug effects; D010215:Papio; D010976:Platelet Count / Q000187:drug effects; D011994:Recombinant Proteins; D019089:Stem Cell Factor
chemical_list: D015703:Antigens, CD; D018952:Antigens, CD34; D016298:Hematopoietic Cell Growth Factors; D011994:Recombinant Proteins; D019089:Stem Cell Factor; D016179:Granulocyte Colony-Stimulating Factor