Regulation of VEGF in Tumors by Ras, EGF and PTEN

Ras、EGF 和 PTEN 对肿瘤中 VEGF 的调节

• 批准号: 6760221
• 负责人: Amit Maity
• 金额: $ 26.35万
• 依托单位: UNIVERSITY OF PENNSYLVANIA
• 依托单位国家: 美国
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-07-01 至 2006-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6760221
• 关键词: SDS polyacrylamide gel electrophoresis; angiogenesis; biological signal transduction; cell line; enzyme activity; epidermal growth factor; gene expression; gene mutation; genetic regulation; growth factor receptors; guanine nucleotide binding protein; hypoxia; hypoxia inducible factor 1; messenger RNA; neoplastic process; northern blottings; oncogenes; phosphatidylinositol 3 kinase; point mutation; protein kinase; site directed mutagenesis; transfection /expression vector; tumor suppressor proteins; vascular endothelial growth factors; western blottings

DESCRIPTION (provided by applicant): Vascular endothelial growth factor (VEGF), a key mediator of angiogenesis, is often overexpressed in cancers. In many in vivo models, inhibition of VBGF function arrests tumor growth. While hypoxia has long been recognized to be a potent inducer of VEGF, VEGF can also be expressed in normoxia. Recent evidence indicates that angiogenesis can develop in tumor masses before they have grown to a size large enough to contain hypoxic regions, suggesting that angiogenic factors may be expressed by these tumors under normoxic conditions. In contrast to the induction of VEGF rnRNA under hypoxia whose mechanism is known to involve the hypoxia-inducible factor-1 (HIF-1), the upregulation of VEGF in normoxia is much less well understood. The overall aim of this grant is to study mechanisms of VEGF upregulation in normoxia by alterations commonly found in cancers: specifically, epidermal growth factor receptor (EGFR) activation and mutations in Ras and PTEN. VEGF mRNA levels and promoter activity in U87 human glioblastoma cells are increased by EGFR stimulation. Introduction of wild type PTEN into U87 cells, in which PTEN is inactivated, decreases VEGF mRNA levels and promoter activity. Specific Aim 1 will focus on defining the elements in this pathway, which appears to be PI(3) kinase dependent but independent of HIF- 1. H-ras transformation of Rat 1 fibroblasts leads to a six-fold increase in VEGF mRNA expression in normoxia. Furthermore, the level of HIF-1alpha protein is increased in normoxic Rat1-ras cells, an unexpected finding given that HIF-1alpha has traditionally been thought to only be induce under hypoxic conditions. The focus of Specific Aim 2 is to determine whether this increase in HIF- 1 alpha causes the increase in VEGF expression under normoxia. Aim 2 will also examine the signaling pathways that link Ras activation, HIF-1alpha and VEGF expression. These experiments will lead to a better understanding of HIF-1 alpha regulation, mechanisms of VEGF overexpression in cancers, and the effects of EGFR activation and Ras and PTEN mutations on gene expression.

描述（由申请人提供）：血管内皮生长因子（VEGF）是血管生成的关键介质，通常在癌症中过度表达。在许多体内模型中，抑制 VBGF 功能可阻止肿瘤生长。虽然缺氧长期以来被认为是 VEGF 的有效诱导剂，但 VEGF 也可以在常氧条件下表达。最近的证据表明，在肿瘤块长到足以容纳缺氧区域的尺寸之前，血管生成就可以在肿瘤块中发育，这表明这些肿瘤在常氧条件下可能表达血管生成因子。缺氧条件下 VEGF rnRNA 的诱导机制已知涉及缺氧诱导因子 1 (HIF-1)，与之相反，常氧条件下 VEGF 的上调却知之甚少。该资助的总体目标是研究常氧条件下 VEGF 通过癌症中常见的改变而上调的机制：具体来说，表皮生长因子受体 (EGFR) 激活以及 Ras 和 PTEN 突变。 EGFR 刺激可增加 U87 人胶质母细胞瘤细胞中的 VEGF mRNA 水平和启动子活性。将野生型 PTEN 引入 U87 细胞（其中 PTEN 失活）会降低 VEGF mRNA 水平和启动子活性。具体目标 1 将重点定义该途径中的元素，该途径似乎依赖于 PI(3) 激酶，但独立于 HIF-1。Rat 1 成纤维细胞的 H-ras 转化导致 VEGF mRNA 表达增加六倍含氧量正常。此外，在常氧 Rat1-ras 细胞中 HIF-1α 蛋白的水平增加，这是一个意外的发现，因为传统上认为 HIF-1α 只在缺氧条件下诱导。具体目标 2 的重点是确定 HIF-1 α 的增加是否会导致常氧条件下 VEGF 表达的增加。目标 2 还将检查连接 Ras 激活、HIF-1α 和 VEGF 表达的信号通路。这些实验将有助于更好地了解 HIF-1 α 调节、癌症中 VEGF 过度表达的机制，以及 EGFR 激活以及 Ras 和 PTEN 突变对基因表达的影响。