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: 6605674
• 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/6605674
• 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，通常在癌症中过表达。在许多体内模型中，VBGF功能的抑制阻止了肿瘤生长。虽然低氧长期以来被认为是VEGF的有效诱导剂，但VEGF也可以在常氧下表达。最近的证据表明，血管生成可以在肿瘤块生长到足够大的尺寸，以包含缺氧区域之前，这些肿瘤中发展，这表明，血管生成因子可能在常氧条件下表达。与缺氧下VEGF mRNA的诱导相反，其机制已知涉及缺氧诱导因子-1（HIF-1），常氧下VEGF的上调知之甚少。这项资助的总体目标是通过癌症中常见的改变来研究常氧条件下VEGF上调的机制：特别是表皮生长因子受体（EGFR）激活和Ras和PTEN突变。U87人胶质母细胞瘤细胞中VEGF mRNA水平和启动子活性通过EGFR刺激而增加。将野生型PTEN引入U87细胞中，其中PTEN失活，降低VEGF mRNA水平和启动子活性。具体目标1将集中于定义这一途径中的元件，这似乎是PI（3）激酶依赖性的，但不依赖于HIF- 1。大鼠1成纤维细胞的H-ras转化导致常氧条件下VEGF mRNA表达增加6倍。此外，HIF-1 α蛋白的水平在常氧Rat 1-ras细胞中增加，这是一个意想不到的发现，因为HIF-1 α传统上被认为仅在缺氧条件下被诱导。具体目标2的重点是确定在常氧下HIF- 1 α的增加是否导致VEGF表达的增加。目的2还将研究连接Ras激活、HIF-1 α和VEGF表达的信号通路。这些实验将使我们更好地理解HIF-1 α的调节、VEGF在癌症中过度表达的机制，以及EGFR激活和Ras和PTEN突变对基因表达的影响。