Hypoxic regulation of vascular endothelial growth factor through the induction of phosphatidylinositol 3-kinase/Rho/ROCK and c-Myc
Hypoxic regulation of vascular endothelial growth factor through the induction of phosphatidylinositol 3-kinase/Rho/ROCK and c-Myc
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DOI：
10.1074/jbc.m511763200
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发表时间：
2006-05-19
影响因子：
4.8
通讯作者：
Chung, Daniel C.
中科院分区：
文献类型：
--
作者：
Mizukami, Yusuke;Fujiki, Kotoyo;Chung, Daniel C.
血管内皮生长因子（VEGF）的诱导是肿瘤血管生成的基本特征。缺氧是VEGF表达的有效刺激物，并且缺氧诱导因子-1（HIF-1）被认为是这种诱导的关键。然而，我们先前已经证明，当HIF-1 α沉默时，缺氧诱导的VEGF被保留。我们试图更好地定义这种HIF-1非依赖性调节的分子基础。在结肠癌细胞中，缺氧刺激多种K-ras效应通路，包括磷脂酰肌醇3-激酶。VEGF启动子缺失研究鉴定了-418和-223 bp之间的新启动子区域，其以PI 3 K/Rho/ROCK依赖性方式响应缺氧。电泳迁移率变动分析鉴定了-300和-251 bp之间的片段，其仅在缺氧条件下表现出独特的变动。抑制PI 3 K或ROCK可阻断该复合物的形成。在~ 271 bp处鉴定了ROCK的靶标c-Myc的结合位点。通过VEGF启动子的定点突变和小干扰RNA沉默c-Myc证实了c-Myc在VEGF缺氧诱导中的作用。总的来说，这些发现表明结肠癌中VEGF的低氧诱导的替代机制不依赖于HIF-1 α，而是需要PI 3 K/Rho/ROCK和c-Myc的激活。
The induction of vascular endothelial growth factor (VEGF) is an essential feature of tumor angiogenesis. Hypoxia is a potent stimulator of VEGF expression, and hypoxia-inducible factor-1 (HIF-1) is considered to be critical for this induction. However, we have previously demonstrated that induction of VEGF by hypoxia was preserved when HIF-1 alpha was silenced. We sought to better define the molecular basis of this HIF-1-independent regulation. In colon cancer cells, hypoxia stimulated multiple K-ras effector pathways including phosphatidylinositol 3-kinase. VEGF promoter deletion studies identified a novel promoter region between -418 and -223 bp that was responsive to hypoxia in a PI3K/Rho/ROCK-dependent manner. Electrophoretic mobility shift assays identified a fragment between -300 and -251 bp that demonstrated a unique shift only in hypoxic conditions. Inhibition of PI3K or ROCK blocked the formation of this complex. A binding site for c-Myc, a target of ROCK, was identified at -271 bp. A role for c-Myc in the hypoxic induction of VEGF was demonstrated by site-directed mutagenesis of the VEGF promoter and silencing of c-Myc by small interfering RNA. Collectively, these findings suggest an alternative mechanism for the hypoxic induction of VEGF in colon cancer that does not depend upon HIF-1 alpha but instead requires the activation of PI3K/Rho/ROCK and c-Myc.