Zagzag David, Lukyanov Yevgeniy, Lan Li, Ali M Aktar, Esencay Mine, Mendez Olga, Yee Herman, Voura Evelyn B, Newcomb Elizabeth W
Microvascular and Molecular Neuro-Oncology Laboratory, New York University School of Medicine, New York, NY 10016, USA.
Lab Invest. 2006 Dec;86(12):1221-32. doi: 10.1038/labinvest.3700482. Epub 2006 Oct 30.
Hypoxia and hypoxia-inducible factor-1 (HIF-1) play a critical role in glioblastoma multiforme (GBMs). CXCR4 is involved in angiogenesis and is upregulated by HIF-1alpha. CXCR4 is a chemokine receptor for stromal cell-derived factor-1 (SDF-1)alpha, also known as CXCL12. We hypothesized that CXCR4 would be upregulated by hypoxia in GBMs. First, we investigated the expression of HIF-1alpha and CXCR4 in GBMs. CXCR4 was consistently found colocalized with HIF-1alpha expression in pseudopalisading glioma cells around areas of necrosis. In addition, angiogenic tumor vessels were strongly positive for CXCR4. Next, we tested the in vitro effect of hypoxia and vascular endothelial growth factor (VEGF) on the expression of CXCR4 in glioma cell lines and in human brain microvascular endothelial cells (HBMECs). Exposure to hypoxia induced significant expression of CXCR4 and HIF-1alpha in glioma cells, whereas treatment with exogenous VEGF increased CXCR4 expression in HBMECs. We also transfected U87MG glioma cells with an HIF-1alpha construct and observed that CXCR4 was upregulated in these cells even in normoxic conditions. We then used a lentivirus-mediated shRNA expression vector directed against HIF-1alpha. When exposed to hypoxia, infected cells failed to show HIF-1alpha and CXCR4 upregulation. We performed migration assays under normoxic and hypoxic conditions in the presence or absence of AMD3100, a CXCR4 inhibitor. There was a significant increase in the migration of U87MG and LN308 glioma cells in hypoxic conditions, which was inhibited in the presence of AMD3100. These studies demonstrate the critical role played by hypoxia and CXCR4 in glioma cell migration. Based on these studies, we suggest that hypoxia regulates CXCR4 in GBMs at two levels. First, through HIF-1alpha in the pseudopalisading tumor cells themselves and, secondly, by the VEGF-stimulated angiogenic response in HBMECs. We believe this knowledge may lead to a potentially important two-pronged therapy against GBM progression using chemotherapy targeting CXCR4.
缺氧和缺氧诱导因子-1（HIF-1）在多形性胶质母细胞瘤（GBM）中起关键作用。CXCR4参与血管生成，并被HIF-1α上调。CXCR4是基质细胞衍生因子-1（SDF-1）α的趋化因子受体，SDF-1α也被称为CXCL12。我们推测CXCR4在GBM中会被缺氧上调。首先，我们研究了GBM中HIF-1α和CXCR4的表达。在坏死区域周围的假栅栏状胶质瘤细胞中，始终发现CXCR4与HIF-1α表达共定位。此外，肿瘤血管生成血管对CXCR4呈强阳性。接下来，我们测试了缺氧和血管内皮生长因子（VEGF）对胶质瘤细胞系和人脑微血管内皮细胞（HBMECs）中CXCR4表达的体外影响。暴露于缺氧环境会诱导胶质瘤细胞中CXCR4和HIF-1α的显著表达，而用外源性VEGF处理会增加HBMECs中CXCR4的表达。我们还用HIF-1α构建体转染了U87MG胶质瘤细胞，观察到即使在常氧条件下这些细胞中的CXCR4也会上调。然后我们使用了针对HIF-1α的慢病毒介导的shRNA表达载体。当暴露于缺氧环境时，被感染的细胞未能显示HIF-1α和CXCR4上调。我们在常氧和缺氧条件下，在有或没有CXCR4抑制剂AMD3100的情况下进行了迁移试验。在缺氧条件下，U87MG和LN308胶质瘤细胞的迁移显著增加，而在有AMD3100的情况下则受到抑制。这些研究证明了缺氧和CXCR4在胶质瘤细胞迁移中所起的关键作用。基于这些研究，我们认为缺氧在两个水平上调节GBM中的CXCR4。首先，通过假栅栏状肿瘤细胞自身中的HIF-1α，其次，通过HBMECs中VEGF刺激的血管生成反应。我们相信这一知识可能会导致一种潜在的重要双管齐下的疗法，即使用针对CXCR4的化疗来对抗GBM的进展。
