title: Effect of a structurally modified human granulocyte colony stimulating factor, G-CSFa, on leukopenia in mice and monkeys.
abstract: BACKGROUND
  Granulocyte colony stimulating factor (G-CSF) regulates survival, proliferation, and differentiation of neutrophilic granulocyte precursors, Recombinant G-CSF has been used for the treatment of congenital and therapy-induced neutropenia and stem cell mobilization. Due to its intrinsic instability, recombinant G-CSF needs to be excessively and/or frequently administered to patients in order to maintain a plasma concentration high enough to achieve therapeutic effects. Therefore, there is a need for the development of G-CSF derivatives that are more stable and active in vivo.
  
  
  METHODS
  Using site-direct mutagenesis and recombinant DNA technology, a structurally modified derivative of human G-CSF termed G-CSFa was obtained. G-CSFa contains alanine 17 (instead of cysteine 17 as in wild-type G-CSF) as well as four additional amino acids including methionine, arginine, glycine, and serine at the amino-terminus. Purified recombinant G-CSFa was tested for its in vitro activity using cell-based assays and in vivo activity using both murine and primate animal models.
  
  
  RESULTS
  In vitro studies demonstrated that G-CSFa, expressed in and purified from E. coli, induced a much higher proliferation rate than that of wild-type G-CSF at the same concentrations. In vivo studies showed that G-CSFa significantly increased the number of peripheral blood leukocytes in cesium-137 irradiated mice or monkeys with neutropenia after administration of cyclophosphamide. In addition, G-CSFa increased neutrophil counts to a higher level in monkeys with a concomitant slower declining rate than that of G-CSF, indicating a longer half-life of G-CSFa. Bone marrow smear analysis also confirmed that G-CSFa was more potent than G-CSF in the induction of granulopoiesis in bone marrows of myelo-suppressed monkeys.
  
  
  CONCLUSIONS
  G-CSFa, a structurally modified form of G-CSF, is more potent in stimulating proliferation and differentiation of myeloid cells of the granulocytic lineage than the wild-type counterpart both in vitro and in vivo. G-CSFa can be explored for the development of a new generation of recombinant therapeutic drug for leukopenia.
authors.affiliation: Fanzhou Biopharmagen Corporation, Suzhou, China.
authors.forename: Yongping
authors.initials: Y
authors.lastname: Jiang
authors.forename: Wenhong
authors.initials: W
authors.lastname: Jiang
authors.forename: Yuchang
authors.initials: Y
authors.lastname: Qiu
authors.forename: Wei
authors.initials: W
authors.lastname: Dai
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D016179:Granulocyte Colony-Stimulating Factor / Q000097:blood / Q000235:genetics / Q000494:pharmacology*; D000882:Haplorhini; D019650:Hematopoietic Stem Cell Mobilization; D006801:Humans; D007970:Leukopenia / Q000097:blood / Q000188:drug therapy*; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008813:Mice, Inbred ICR; D016297:Mutagenesis, Site-Directed; D009503:Neutropenia / Q000097:blood / Q000188:drug therapy; D011994:Recombinant Proteins / Q000097:blood / Q000235:genetics / Q000494:pharmacology
chemical_list: D011994:Recombinant Proteins; D016179:Granulocyte Colony-Stimulating Factor