The transcriptional factor involved in the constitutive expression of interleukin-6 in multiple myeloma

本研究的目的是通过阐明多发性骨髓瘤自分泌生长因子白介素6(IL-6)的结构性产生机制来了解多发性骨髓瘤的发病机制。已有研究表明，在人胶质母细胞瘤细胞系SK-MG-4中，IL-1诱导的IL-6基因的转录激活是由转录因子NF-ILF6介导的，它与IL-6基因启动子区域的特定DNA序列结合。为了探讨核因子-IL-6是否也参与骨髓瘤细胞IL-6的结构性表达，我们采用RT-PCR方法分析了骨髓瘤细胞中IL-6和核因子-IL-6的表达。在所有受试的骨髓瘤细胞中，包括人骨髓瘤细胞系KMS-5、U266以及原代培养的骨髓瘤细胞，我们都能检测到IL-6和NF-IL6mRNA的表达，其表达强度与PHA和TPA刺激的人外周血单核细胞相当，甚至更强。此外，我们还可以通过凝胶漂移实验检测到这些骨髓瘤细胞核提取液中作为序列特异性DNA结合蛋白的NF-IL6活性。在正常组织中，NF-IL6mRNA不正常表达，但在内毒素或包括IL-1在内的几种细胞因子刺激下瞬时表达。我们的数据显示，在骨髓瘤细胞中，在没有任何刺激的情况下，NF-IL6的结构性表达和活性可能是导致骨髓瘤细胞中IL-6的结构性和非调节性产生的原因。

The purpose of this research project is to understand the pathogenesis of multiple myeloma by clarifying the mechanism of constitutive production of its autocrine growth factor, interleukin-6 (IL-6). It has been shown that, in human glioblastoma cell line SK-MG-4, IL-1 induced transcriptional activation of the IL-6 gene is mediated by a transcriptional factor NF-ILF6, which binds to a specific DNA sequence in the promoter region of the IL-6 gene. In order to test the possibility that NF-IL6 might be involved also in the constitutive expression of IL-6 in myeloma cells, we analyzed expression of both IL-6 and NF-IL6 mRNA in myeloma cells using the RT-PCR method. In all of the tested myeloma cells, including human myeloma cell lines, KMS-5 and U266 as well as primarily cultured myeloma cells, we could detect expression of both IL-6 and NF-IL6 mRNA, whose intensities were comparable to or even stronger than those of the human peripheral mononuclear cells stimulated with PHA and TPA. Moreover, we could detect NF-IL6 activity as a sequence specific DNA binding protein in nuclear extracts of those myeloma cells by gel shift assay probed with a synthetic oligonucleotide corresponding to a NF-IL6 binding sequence. In normal tissues, NF-IL6 mRNA is not expressed ordinarily, but expressed transiently upon stimulation with LPS or several cytokines, including IL-1. Our data showing the constitutive expression of NF-IL6 mRNA and activity in myeloma cells without any stimulation suggest the possibility that the constitutive expression of NF-IL6 may be responsible for the constitutive and deregulated production of IL-6 in myeloma cells.