Caruana G, Ashman L K, Fujita J, Gonda T J
Leukaemia Research Unit, Hanson Centre for Cancer Research, Adelaide, South Australia.
Exp Hematol. 1993 Jun;21(6):761-8.
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.
小鼠白细胞介素3（IL-3）或粒细胞-巨噬细胞集落刺激因子（GM-CSF）依赖性细胞系FDC-P1的细胞表达酪氨酸激酶受体c-kit。c-kit的配体——由Steel（Sl）基因座编码的Steel因子（SLF），由成纤维样细胞产生膜结合形式和可溶性形式。已知源自正常（+/+）WCB6F1小鼠的成纤维细胞能产生两种形式的SLF，并且在存在中和抗GM-CSF抗血清的情况下能够以接触依赖的方式支持FDC-P1细胞。相比之下，仅产生可溶性形式SLF的Sl/Sld突变成纤维细胞在存在GM-CSF抗血清的情况下无法支持FDC-P1细胞。这些结果表明，FDC-P1细胞在成纤维细胞层上由膜结合的SLF支持。尝试在高水平的可溶性重组SLF中培养FDC-P1细胞以模拟共培养实验中观察到的SLF依赖性反应，结果显示，先前在GM-CSF或IL-3中培养的细胞在浓度高达100 ng/mL的SLF作用下反应极小。尽管这些培养物不能仅由SLF支持，但细胞对SLF与次优水平的GM-CSF或IL-3联合使用表现出协同增殖反应。然而，通过在3周的时间内逐渐用SLF替代GM-CSF，FDC-P1细胞能够适应仅在SLF中生长。这些细胞的c-kit mRNA水平分别比在GM-CSF或IL-3中生长的细胞高5.6至8.4倍和2.5倍。与在SLF中生长的细胞相比，在GM-CSF或IL-3中生长的FDC-P1细胞中也观察到表面c-kit蛋白的下调。尽管在SLF中增殖的FDC-P1细胞对SLF反应更强，但它们在GM-CSF和IL-3中的增殖能力与最初在这些因子中生长的细胞一样好。因此，GM-CSF和IL-3对c-kit的功能下调是单向的。
