title: Responses of the murine myeloid cell line FDC-P1 to soluble and membrane-bound forms of steel factor (SLF).
abstract: Cells of the murine interleukin-3 (IL-3) or granulocyte-macrophage colony-stimulating factor (GM-CSF) factor-dependent line, FDC-P1, express the tyrosine kinase receptor, c-kit. The ligand for c-kit, steel factor (SLF), encoded by the steel (Sl) locus, is produced as both membrane-bound and soluble forms by fibroblastoid cells. Fibroblasts derived from normal (+/+) WCB6F1 mice are known to produce both forms of SLF and were able to support FDC-P1 cells in a contact-dependent manner in the presence of neutralizing anti-GM-CSF antiserum. In contrast, Sl/Sld mutant fibroblasts, which produce only a soluble form of SLF, were incapable of supporting FDC-P1 cells in the presence of GM-CSF antiserum. These results suggested that FDC-P1 cells were being supported on fibroblast layers by membrane-bound SLF. Attempts to grow FDC-P1 cells in high levels of soluble recombinant SLF to mimic the SLF-dependent response seen in co-culture experiments showed that cells which had been previously grown in GM-CSF or IL-3 were minimally responsive to SLF at concentrations up to 100 ng/mL. Although these cultures were not supported by SLF alone, the cells showed synergistic proliferative responses to SLF combined with suboptimal levels of GM-CSF or IL-3. FDC-P1 cells could, however, be adapted to grow in SLF alone by gradual substitution of SLF for GM-CSF over a period of 3 weeks. These cells showed 5.6- to 8.4-fold and 2.5-fold higher levels of c-kit mRNA than cells grown in GM-CSF or IL-3, respectively. Downregulation of surface c-kit protein was also seen in FDC-P1 cells grown in GM-CSF or IL-3 compared with cells grown in SLF. Although FDC-P1 cells propagated in SLF were more responsive to SLF, they were still able to proliferate as well in GM-CSF and IL-3 as the cells originally grown in the latter factors. Thus, functional downregulation of c-kit by GM-CSF and IL-3 was unidirectional.
authors.affiliation: Leukaemia Research Unit, Hanson Centre for Cancer Research, Adelaide, South Australia.
authors.forename: G
authors.initials: G
authors.lastname: Caruana
authors.forename: L K
authors.initials: LK
authors.lastname: Ashman
authors.forename: J
authors.initials: J
authors.lastname: Fujita
authors.forename: T J
authors.initials: TJ
authors.lastname: Gonda
mesh_terms: D000818:Animals; D001853:Bone Marrow / Q000187:drug effects / Q000378:metabolism; D001854:Bone Marrow Cells; D002450:Cell Communication / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation; D004357:Drug Synergism; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects; D005786:Gene Expression Regulation / Q000235:genetics; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000494:pharmacology; D016298:Hematopoietic Cell Growth Factors / Q000378:metabolism / Q000494:pharmacology*; D007377:Interleukin-3 / Q000494:pharmacology; D008024:Ligands; D051379:Mice; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism; D019009:Proto-Oncogene Proteins c-kit; D012333:RNA, Messenger / Q000032:analysis / Q000235:genetics; D019089:Stem Cell Factor
chemical_list: D016298:Hematopoietic Cell Growth Factors; D007377:Interleukin-3; D008024:Ligands; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D019089:Stem Cell Factor; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D019009:Proto-Oncogene Proteins c-kit