Hypoxia VHL nad HIF in Renal Tumor Development

描述(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)肿瘤抑制因子的失活有关。在大约70%的散发性肾癌中可以发现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，以实现泛素化和随后的蛋白酶体降解。VHL的失活被认为是肾细胞癌发生过程中的早期事件，并导致两种主要的HIF亚型HIF-1和HIF-2的结构性表达。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存在争议。假设HIF-1/HIF-2水平在VHL相关肾肿瘤的发生发展中起重要作用的假说将被研究。基于Cre-loxP介导的重组和靶向转基因的条件性基因打靶技术将被用于在体内和体外调控pVHL和HIF的表达水平。该系统能够研究VHL缺陷和HIF激活在不同组织起源的原代肾上皮细胞中对肾细胞生长和活力的功能关系。具体地说，拟议的研究将检验在VHL缺乏和野生型背景下HIF-1和HIF-2表达增加或缺失的影响。研究将在原代细胞培养和体内肾脏特异性条件性基因敲除小鼠中进行。基因表达研究将提供有关HIF-1和HIF-2靶基因在不同肾单位节段的差异表达的信息，重点是参与细胞生存调节的基因。综上所述，拟议的体内和体外研究不仅将为肾肿瘤发生的早期事件和肾癌的组织起源提供新的见解，还将研究不同肾单位节段中HIF-1和HIF-2功能的基本方面。最终，他们有可能建立与VHL相关的肾脏肿瘤的小鼠模型。

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.