Sp-1 and c-Myc mediate lysophosphatidic acid-induced expression of vascular endothelial growth factor in ovarian cancer cells via a hypoxia-inducible factor-1-independent mechanism.
Sp-1 and c-Myc mediate lysophosphatidic acid-induced expression of vascular endothelial growth factor in ovarian cancer cells via a hypoxia-inducible factor-1-independent mechanism.
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DOI：
10.1158/1078-0432.ccr-08-1945
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发表时间：
2009-01-15
期刊：
影响因子：
--
通讯作者：
Fang X
中科院分区：
文献类型：
--
作者：
Song Y;Wu J;Oyesanya RA;Lee Z;Mukherjee A;Fang X
溶血磷脂酸（LPA）存在于卵巢癌患者的腹水中，其刺激血管内皮生长因子（VEGF）的表达。VEGF在卵巢癌的发生和腹腔转移中起重要作用。我们研究了LPA如何驱动VEGF表达，以更好地了解常氧条件下的肿瘤血管生成。ELISA、北方印迹、免疫印迹、定量PCR和启动子报告基因分析结合小干扰RNA和药理学抑制剂被用于检查LPA诱导的VEGF表达和潜在机制。LPA刺激多种VEGF变体的表达。在转录起始位点附近有一个123 bp的片段被鉴定为负责对LPA应答的功能性启动子区域。该片段含有包括c-Myc和Sp-1但不是低氧诱导因子-1在内的几种转录因子的共有位点。Rho、ROCK或c-Myc的阻断降低了LPA依赖性VEGF的产生和启动子活化，表明G12/13-Rho-ROCK-c-Myc级联部分有助于LPA诱导VEGF。更重要的是，多个Sp-1网站内的响应区域的VEGF启动子是必不可少的LPA介导的转录。LPA诱导Sp-1磷酸化和DNA结合和转录活性。用小干扰RNA沉默Sp-1表达或用药物抑制剂抑制Sp-1可阻断LPA诱导的VEGF产生。LPA通过激活c-Myc和Sp-1转录因子，刺激缺氧诱导因子-1非依赖性VEGF表达，促进肿瘤血管生成。
Lysophosphatidic acid (LPA), which is present in ascites of ovarian cancer patients, stimulates expression of vascular endothelial growth factor (VEGF). VEGF is essential for the development and abdominal dissemination of ovarian cancer. We examined how LPA drives VEGF expression to gain a better understanding of tumor angiogenesis under normoxic conditions. ELISA, Northern blotting, immunoblotting, quantitative PCR, and promoter reporter analysis in combination with small interfering RNA and pharmacologic inhibitors were used to examine LPA-induced VEGF expression and the underlying mechanisms. LPA stimulated expression of multiple VEGF variants. A 123-bp fragment proximal to the transcriptional initiation site was identified to be functional promoter region responsible for the response to LPA. The fragment harbors consensus sites for several transcription factors including c-Myc and Sp-1 but not hypoxia-inducible factor-1. Blockade of Rho, ROCK, or c-Myc reduced LPA-dependent VEGF production and promoter activation, suggesting that the G12/13-Rho-ROCK-c-Myc cascade partially contributes to VEGF induction by LPA. More significantly, the multiple Sp-1 sites within the responsive region of the VEGF promoter were essential for LPA-mediated transcription. LPA induced Sp-1 phosphorylation and DNA-binding and transcriptional activities. The silencing of Sp-1 expression with small interfering RNA or inhibition of Sp-1 with pharmacologic inhibitors blocked VEGF production induced by LPA. LPA stimulates hypoxia-inducible factor-1-independent VEGF expression to promote tumor angiogenesis through activation of the c-Myc and Sp-1 transcription factors.