Hypoxia VHL nad HIF in Renal Tumor Development

描述（由申请人提供）：肾透明细胞癌（RCC）是最常见的肾癌形式，与von HippeI-Lindau （VHL）肿瘤抑制因子失活有关。大约70%的散发性rcc患者存在VHL基因突变。VHL基因产物pVHL的主要功能之一是靶向缺氧诱导因子（HIF）的氧敏感α亚基，用于泛素化和随后的蛋白酶体降解。VHL失活被认为是RCC肿瘤发生过程中的早期事件，并导致两种主要HIF亚型HIF-1和HIF-2的组成性表达。这导致调节糖酵解、血管生成和红细胞生成的基因转录增加。HIF-1进一步被证明可以上调促进生长停滞和细胞凋亡的因子。HIF表达增加在VHL相关肿瘤发生中的作用仍有争议。HIF-1与HIF-2水平的比值对VHL相关肾肿瘤的发展很重要的假设将被研究。基于Cre-loxP介导重组和靶向转基因的条件基因靶向技术将用于调控pVHL和HIF在体内和体外的表达水平。该系统能够研究VHL缺乏和HIF激活在不同组织发生来源的原代肾上皮细胞中对肾细胞生长和活力的功能关系。具体来说，拟议的研究将检查在VHL缺陷和野生型背景下HIF-1表达增加或缺失以及HIF-2表达增加的影响。研究将在原代细胞培养和肾脏特异性条件敲除小鼠体内进行。基因表达研究将提供有关HIF-1和HIF-2靶基因在不同肾细胞段表达差异的信息，并特别强调参与细胞存活调控的基因。综上所述，体内和体外研究不仅将为肾癌发生的早期事件和肾细胞癌的组织遗传学起源提供新的见解，而且还将研究HIF-1和HIF-2在不同肾单元段中功能的基本方面。最终，他们有可能创建VHL相关肾肿瘤的小鼠模型。

DESCRIPTION (provided by applicant): Clear cell carcinoma of the kidney (RCC), the most common form of kidney cancer, is associated with the inactivation of the von HippeI-Lindau (VHL) tumor suppressor. Mutations in the VHL gene can be found in approximately 70% of sporadic RCCs. One of the major functions of the VHL gene product, pVHL, is the targeting of the oxygen sensitive alpha-subunit of hypoxia-inducible factor (HIF) for ubiquitination and subsequent proteasomal degradation. Inactivation of VHL is felt to be an early event during RCC tumorigenesis and results in constitutive expression of two major HIF isoforms, HIF-1 and HIF-2. This results in increased transcription of genes that regulate glycolysis, angiogenesis and erythropoiesis. HIF-1 has furthermore been shown to up-regulate factors that promote growth arrest and apoptosis. The role of increased HIF expression in VHL associated tumorigenesis remains controversial. The hypothesis that the ratio of HIF-1 to HIF-2 levels is important for VHL associated renal tumor development will be investigated. Conditional gene targeting technology based on Cre-loxP mediated recombination as well as targeted transgenesis will be used to manipulate the expression levels of both pVHL and HIF in vivo and in vitro. This system enables the study of the functional relationship between VHL deficiency and HIF activation in regard to renal cell growth and viability in primary renal epithelial cells of different histogenetic origin. Specifically, the proposed investigations will examine the effects of increased or absent HIF-1 and increased HIF-2 expression in VHL deficient and wild type backgrounds. Studies will be performed in primary cell culture and in vivo with kidney specific conditional knock out mice. Gene expression studies will provide information regarding differential HIF-1 and HIF-2 target gene expression in different nephron segments with a special emphasis on genes involved in the regulation of cell survival. Taken all together, the proposed in vivo and in vitro studies will not only provide novel insights into the early events of renal oncogenesis and the histogenetic origin of RCC, but also examine fundamental aspects of HIF-1 and HIF-2 function in different nephron segments. Ultimately they have the potential to create a murine model of VHL associated renal tumors.