Helbig Gregory, Christopherson Kent W, Bhat-Nakshatri Poornima, Kumar Suresh, Kishimoto Hiromitsu, Miller Kathy D, Broxmeyer Hal E, Nakshatri Harikrishna
Department of Surgery, Indiana University School of Medicine, Indianapolis, IN 46202, USA.
J Biol Chem. 2003 Jun 13;278(24):21631-8. doi: 10.1074/jbc.M300609200. Epub 2003 Apr 9.
Metastasis of cancer cells is a complex process involving multiple steps including invasion, angiogenesis, and trafficking of cancer cells through blood vessels, extravasations, organ-specific homing, and growth. While matrix metalloproteinases, urokinase-type plasminogen activator, and cytokines play a major role in invasion and angiogenesis, chemokines such as stromal derived factor-1alpha (SDF-1alpha) and their receptors such as CXCR4 are thought to play a critical role in motility, homing, and proliferation of cancer cells at specific metastatic sites. We and others have previously reported that the extracellular signal-activated transcription factor NF-kappaB up-regulates the expression of matrix metalloproteinases, urokinase-type plasminogen activator, and cytokines in highly metastatic breast cancer cell lines. In this report, we demonstrate that NF-kappaB regulates the motility of breast cancer cells by directly up-regulating the expression of CXCR4. Overexpression of the inhibitor of kappaB (IkappaB) in breast cancer cells with constitutive NF-kappaB activity resulted in reduced expression of CXCR4 and a corresponding loss of SDF-1alpha-mediated migration in vitro. Introduction of CXCR4 cDNA into IkappaB-expressing cells restored SDF-1alpha-mediated migration. Electrophoretic mobility shift assays and transient transfection assays revealed that the NF-kappaB subunits p65 and p50 bind directly to sequences within the -66 to +7 region of the CXCR4 promoter and activate transcription. We also show that the cell surface expression of CXCR4 and the SDF-1alpha-mediated migration are enhanced in breast cancer cells isolated from mammary fat pad xenografts compared with parental cells grown in culture. A further increase in CXCR4 cell surface expression and SDF-1alpha-mediated migration was observed with cancer cells that metastasized to the lungs. Taken together, these results implicate NF-kappaB in the migration and the organ-specific homing of metastatic breast cancer cells.
癌细胞转移是一个复杂的过程，涉及多个步骤，包括侵袭、血管生成以及癌细胞通过血管的运输、外渗、器官特异性归巢和生长。虽然基质金属蛋白酶、尿激酶型纤溶酶原激活剂和细胞因子在侵袭和血管生成中起主要作用，但趋化因子如基质衍生因子-1α（SDF-1α）及其受体如CXCR4被认为在特定转移部位癌细胞的运动、归巢和增殖中起关键作用。我们和其他人之前曾报道，细胞外信号激活的转录因子NF-κB在高转移性乳腺癌细胞系中上调基质金属蛋白酶、尿激酶型纤溶酶原激活剂和细胞因子的表达。在本报告中，我们证明NF-κB通过直接上调CXCR4的表达来调节乳腺癌细胞的运动。在具有组成型NF-κB活性的乳腺癌细胞中过表达κB抑制剂（IkappaB）导致CXCR4表达降低以及体外SDF-1α介导的迁移相应丧失。将CXCR4 cDNA导入表达IkappaB的细胞可恢复SDF-1α介导的迁移。电泳迁移率变动分析和瞬时转染分析表明，NF-κB亚基p65和p50直接结合到CXCR4启动子-66至+7区域内的序列并激活转录。我们还表明，与培养的亲本细胞相比，从乳腺脂肪垫异种移植瘤中分离出的乳腺癌细胞中CXCR4的细胞表面表达和SDF-1α介导的迁移增强。在转移至肺部的癌细胞中观察到CXCR4细胞表面表达和SDF-1α介导的迁移进一步增加。综上所述，这些结果表明NF-κB参与转移性乳腺癌细胞的迁移和器官特异性归巢。
