Szczylik C, Skorski T, Ku D H, Nicolaides N C, Wen S C, Rudnicka L, Bonati A, Malaguarnera L, Calabretta B
Department of Microbiology and Immunology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107.
J Exp Med. 1993 Sep 1;178(3):997-1005. doi: 10.1084/jem.178.3.997.
The c-myb protooncogene plays a major role in regulating the process of in vitro and in vivo hematopoiesis via its activity as transcriptional regulator in hematopoietic progenitor cells. Since the bone marrow microenvironment appears to regulate in vivo hematopoiesis by maintaining the growth of multipotent progenitors via secretion of specific cytokines, we asked whether c-myb is also required for the proliferation of and/or cytokine production by stromal cells that generate fibroblast-like colonies (fibroblast colony-forming units [CFU-F]). Using the reverse transcriptase polymerase chain reaction technique, we detected low levels of c-myb mRNA transcripts in human normal bone marrow fibroblasts. Treatment of these cells with c-myb antisense oligodeoxynucleotides caused downregulation of c-myb expression, decreased in the number of marrow CFU-F colonies (approximately 54% inhibition) and in the cell number within residual colonies (approximately 80%), and downregulation of granulocyte/macrophage colony-stimulating factor (GM-CSF) and stem cell factor (SCF) mRNA expression. Transfection of T98G glioblastoma cells, in which expression of c-myb, GM-CSF, and SCF mRNAs is undetectable or barely detectable, with a plasmid containing a full-length c-myb cDNA under the control of the SV40 promoter induced the expression of biologically active SCF and GM-CSF in these cells. Regulation of GM-CSF expression by c-myb was due in part to transactivation of the GM-CSF promoter. These results indicate that, in addition to regulating hematopoietic cell proliferation, c-myb is also required for proliferation of and cytokines synthesis by bone marrow fibroblasts.
c-myb原癌基因通过其作为造血祖细胞转录调节因子的活性，在体外和体内造血过程的调节中发挥主要作用。由于骨髓微环境似乎通过分泌特定细胞因子维持多能祖细胞的生长来调节体内造血，我们询问c-myb对于产生成纤维细胞样集落（成纤维细胞集落形成单位[CFU-F]）的基质细胞的增殖和/或细胞因子产生是否也是必需的。使用逆转录酶聚合酶链反应技术，我们在人正常骨髓成纤维细胞中检测到低水平的c-myb mRNA转录本。用c-myb反义寡脱氧核苷酸处理这些细胞导致c-myb表达下调，骨髓CFU-F集落数量减少（约54%抑制）以及残留集落内细胞数量减少（约80%），并且粒细胞/巨噬细胞集落刺激因子（GM-CSF）和干细胞因子（SCF）mRNA表达下调。用含有在SV40启动子控制下的全长c-myb cDNA的质粒转染T98G胶质母细胞瘤细胞（其中c-myb、GM-CSF和SCF mRNA的表达不可检测或几乎不可检测），诱导了这些细胞中具有生物活性的SCF和GM-CSF的表达。c-myb对GM-CSF表达的调节部分归因于GM-CSF启动子的反式激活。这些结果表明，除了调节造血细胞增殖外，c-myb对于骨髓成纤维细胞的增殖和细胞因子合成也是必需的。
