title: Modulation of the activity of a human granulocyte-macrophage colony-stimulating factor/interleukin-3 fusion protein (pIXY 321) by the macrocyclic lactone protein kinase C activator bryostatin 1.
abstract: We have examined the effect of the macrocyclic lactone protein kinase C (PK-C) activator bryostatin 1 on the proliferative capacity and lineage commitment of CD34+ human bone marrow cells exposed to the granulocyte-macrophage colony-stimulating factor/interleukin-3 (GM-CSF/IL-3) fusion protein pIXY 321. pIXY 321 administered at a dose of 10 ng/mL was as effective as the combination of plateau concentrations of recombinant (r) IL-3 and rGM-CSF (e.g., 50 ng/mL) in stimulating the growth of day-14 committed myeloid progenitors (colony-forming units granulocyte/macrophage [CFU-GM]). In the large majority of samples tested, coadministration of 0.5 to 100 nM bryostatin 1 with either pIXY 321 or the combination of rIL-3 plus rGM-CSF led to modest but significant increases (e.g., 30 to 75%) in the number of CFU-GM, compared to administration of growth factors alone. The degree of bryostatin 1-induced potentiation, however, was considerably less than that previously observed in the case of cells exposed to either rIL-3 or rGM-CSF, where increases of 100 to 150% were regularly noted. While at least 50% of day-14 CFU-GM stimulated by either pIXY 321 or the combination of rIL-3 plus rGM-CSF were of the pure or mixed eosinophilic variety, coadministration of bryostatin 1 resulted in a dramatic inhibition of eosinophilic colonies and a corresponding increase in pure and mixed neutrophil and macrophage colonies. Although coadministration of recombinant granulocyte colony-stimulating factor (rG-CSF) or recombinant colony-stimulating factor-1 (rCSF-1) mimicked the capacity of bryostatin 1 to increase the total number of pIXY 321-induced day-14 CFU-GM, these growth factors, unlike bryostatin 1, were not capable of inhibiting eosinophilic colony formation. Furthermore, whereas addition of neutralizing antibodies to G-CSF or CSF-1 blocked the capacity of these growth factors to potentiate colony formation in the presence of pIXY 321, it did not abrogate the effect of bryostatin 1 on progenitor cell growth or lineage commitment. Finally, in contrast to its effects on committed myeloid progenitors, bryostatin 1 did not increase the growth of erythroid (burst-forming units-erythroid [BFU-E]) and multipotent (multipotent colony-forming units [CFU-GEMM]) progenitors stimulated by pIXY 321, but instead inhibited colony formation at higher concentrations (e.g., 10 to 100 nM).(ABSTRACT TRUNCATED AT 400 WORDS)
authors.affiliation: Department of Medicine, Medical College of Virginia, Richmond.
authors.forename: C W
authors.initials: CW
authors.lastname: McCrady
authors.forename: F
authors.initials: F
authors.lastname: Li
authors.forename: G R
authors.initials: GR
authors.lastname: Pettit
authors.forename: S
authors.initials: S
authors.lastname: Grant
mesh_terms: D000906:Antibodies; D001854:Bone Marrow Cells; D054713:Bryostatins; D002455:Cell Division / Q000187:drug effects; D003114:Colony-Forming Units Assay; D004789:Enzyme Activation / Q000187:drug effects; D016179:Granulocyte Colony-Stimulating Factor / Q000276:immunology / Q000494:pharmacology; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000494:pharmacology*; D006098:Granulocytes / Q000166:cytology; D006412:Hematopoietic Stem Cells / Q000166:cytology* / Q000187:drug effects; D006801:Humans; D007377:Interleukin-3 / Q000494:pharmacology*; D007783:Lactones / Q000494:pharmacology*; D018942:Macrolides; D016173:Macrophage Colony-Stimulating Factor / Q000276:immunology / Q000494:pharmacology; D008264:Macrophages / Q000166:cytology; D011493:Protein Kinase C / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000494:pharmacology*
chemical_list: D000906:Antibodies; D054713:Bryostatins; D007377:Interleukin-3; D007783:Lactones; D018942:Macrolides; C078524:PIXY321 fusion protein, recombinant; D011993:Recombinant Fusion Proteins; D016179:Granulocyte Colony-Stimulating Factor; C046785:bryostatin 1; D016173:Macrophage Colony-Stimulating Factor; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D011493:Protein Kinase C