Hall B M, Fortney J E, Gibson L F
Department of Pediatrics, Robert C. Byrd Health Sciences Center, P.O. Box 9214, West Virginia University, 26506, Morgantown, WV, USA.
Biochem Pharmacol. 2001 May 15;61(10):1243-52. doi: 10.1016/s0006-2952(01)00602-5.
Bone marrow stromal cells are an essential regulatory component in the hematopoietic microenvironment. Regulation of hematopoietic cell development is mediated, in part, through interaction of progenitor cells with stromal cell vascular cell adhesion molecule-1 (VCAM-1). VCAM-1 expression has been shown to be driven primarily by binding of nuclear factor-kappaB (NF-kappaB) to two consensus binding sites in the promoter region. In this study, we show that down-regulation of VCAM-1 by the chemotherapeutic agent etoposide (VP-16) is associated with altered cellular localization of NF-kappaB. We demonstrated that VCAM-1 was diminished at the transcriptional level following treatment of stromal cells with VP-16, without alteration of VCAM-1 stability. Culture of bone marrow stromal cells in VP-16 resulted in reduced nuclear RelA (p65), a modest increase in nuclear NF-kappaB1 (p50), and reduced NF-kappaB binding to its DNA consensus sequence. Total levels of the NF-kappaB inhibitor Ikappa-Balpha were reduced during exposure to VP-16. Following removal of VP-16 from the culture, p65 and p50 nuclear profiles approximated those of untreated stromal cells, and VCAM-1 protein expression was restored. The current study indicates that NF-kappaB is a target molecule that is responsive to VP-16-induced damage in bone marrow stromal cells. As the primary transcription factor that promotes VCAM-1 expression, the observed changes in p65 and p50 cellular localization during treatment have a direct consequence for stromal cell function. The myriad of genes regulated by NF-kappaB, including both adhesion molecules and cytokines that contribute to stromal cell function, make chemotherapy-induced disruption of NF-kappaB biologically significant. Alterations in NF-kappaB activity may provide one measure by which the effects of aggressive treatment strategies on the bone marrow microenvironment can be evaluated.
骨髓基质细胞是造血微环境中重要的调节成分。造血细胞发育的调节部分是通过祖细胞与基质细胞血管细胞黏附分子-1（VCAM-1）的相互作用介导的。已表明VCAM-1的表达主要由核因子-κB（NF-κB）与启动子区域的两个共有结合位点结合驱动。在本研究中，我们表明化疗药物依托泊苷（VP-16）对VCAM-1的下调与NF-κB细胞定位的改变有关。我们证明，用VP-16处理基质细胞后，VCAM-1在转录水平降低，而VCAM-1稳定性未改变。在VP-16中培养骨髓基质细胞导致核RelA（p65）减少，核NF-κB1（p50）适度增加，且NF-κB与其DNA共有序列的结合减少。在暴露于VP-16期间，NF-κB抑制剂IκBα的总水平降低。从培养物中去除VP-16后，p65和p50的核分布接近未处理的基质细胞，并且VCAM-1蛋白表达得以恢复。当前研究表明NF-κB是对骨髓基质细胞中VP-16诱导的损伤有反应的靶分子。作为促进VCAM-1表达的主要转录因子，治疗期间观察到的p65和p50细胞定位变化对基质细胞功能有直接影响。由NF-κB调节的众多基因，包括有助于基质细胞功能的黏附分子和细胞因子，使得化疗诱导的NF-κB破坏具有生物学意义。NF-κB活性的改变可能提供一种评估积极治疗策略对骨髓微环境影响的方法。
