Transcriptional Response to Hypoxia in Transformed Cells

描述（由申请人提供）：在本资助的前一个资助期，我们专注于缺氧反应和缺氧反应转录因子hif -1 α在肿瘤发生中的作用。在这次更新中，我们建议现在集中在一个特定的组织，乳腺，和这种反应在致瘤性扩张和血管化的要求。在之前的资助期内，我们实验室的工作已经确定HIF-1alpha的表达是小鼠胚胎发育所必需的，并且参与了HIF-1alpha缺失细胞衍生的肿瘤的血管化和生长。最近hif -1 α蛋白被证实在多种人类实体肿瘤中上调，特别是在具有高增殖率的乳腺肿瘤中。假设：低氧反应，通过hif -1 α，是肿瘤发生过程中乳腺上皮细胞快速增殖和去分化过程中生理适应的一个关键方面。目的：确定缺氧反应在化学致癌物诱导的乳腺上皮转化和肿瘤形成中的作用，以及在乳腺癌转基因小鼠模型中的作用。2)转化乳腺上皮的扩张和对缺氧的代谢适应。3)乳腺肿瘤新生血管形成。为了验证通过HIF-1的缺氧反应对乳腺肿瘤发生至关重要的假设，我们专门从乳腺上皮中去除了两种调节缺氧反应的蛋白：1)hif1 - α和2)在常氧条件下与HIF-1 - α蛋白相互作用并靶向其泛素化的蛋白，即von Hippel-Lindau （VHL）因子。在这两种情况下，这都是通过使用有条件靶向的小鼠菌株来实现的。我们最近在这些模型中描述了正常的乳腺发育，并且这两种动物，即那些在乳腺上皮中缺乏hif -1 α或VHL的动物，在乳腺发育和泌乳方面都表现出明显的缺陷。由于HIF-1alpha过表达在乳腺肿瘤中已有报道，本研究的目的是确定HIF-1alpha或VHL的缺失导致HIF-1alpha过表达，是否会影响转基因乳腺肿瘤模型或化学致癌物DMBA治疗小鼠乳腺的转化、扩张和新血管形成。我们期望在本提案中开展的工作将极大地有助于评估针对乳腺癌缺氧反应的潜力。

DESCRIPTION (provided by applicant): In the previous funding period of this grant, we focused on the role of hypoxic response and the hypoxia-responsive transcription factor HIF-1alpha in tumorigenesis. In this renewal, we propose to now concentrate on one specific tissue, the mammary gland, and the requirement for this response in tumorigenic expansion and vascularization. Work from our laboratory in the previous funding period has established that HIF-1alpha expression is required for mouse embryonic development, and is involved in the vascularization and growth of tumors derived from HIF-1alpha null cells. Recently HIF-1alpha protein has been demonstrated to be up-regulated in a variety of human solid tumors, in particular breast tumors that exhibit high rates of proliferation. Hypothesis: Hypoxic response, via HIF-1alpha, is a critical aspect of physiological adaptation during the rapid proliferation and de-differentiation of mammary epithelial cells during tumorigenesis. Objectives/Aims: To determine the role of hypoxic response: 1) In mammary epithelial transformation and tumor formation induced by chemical carcinogens, and in transgenic mouse models of breast cancer. 2) In expansion and metabolic adaptation to hypoxia of transformed mammary epithelium. 3) In neo-vascularization of mammary tumors. In order to test the hypothesis that hypoxic response through HIF-1 is critically important for mammary tumorigenesis, we have specifically removed from the mammary epithelium two proteins that regulate the hypoxic response: 1) HIF1-alpha and 2) the protein that interacts with and targets HIF-1alpha protein for ubiquitination under normoxic conditions, the von Hippel-Lindau (VHL) factor. In both cases, this has been done through the use of conditionally targeted mouse strains. We have recently characterized normal mammary gland development in each of these models, and both animals, i.e., those lacking HIF-1alpha or VHL in mammary epithelium, exhibit striking defects in mammary gland development and lactation. Since HIF-1alpha overexpression has been reported in breast tumors, the goals of this proposal are to determine if deletion of either HIF-1alpha or VHL, which results in HIF-1alpha overexpression, affects transformation, expansion and neo-vascularization of the murine mammary gland in transgenic breast tumor models, or in mice treated with the chemical carcinogen DMBA. We anticipate that the work carried out in this proposal will aid greatly in evaluating the potential for targeting hypoxia-response in breast cancer.