Mechanism of angiogenesis inhibition by a homeobox gene

描述（由申请人提供）：恶性肿瘤依赖于诱导宿主新生血管的生长来满足其氧气和营养需求，肿瘤血管生成在过去十年中已经成为抗肿瘤治疗的一个有希望的新靶点。肿瘤分泌的促血管生成因子和抗血管生成因子的主要靶点是血管内皮细胞。我们的长期目标是明确内皮细胞血管生成的转录调控，并利用这些信息开发新的抗血管生成疗法。Gax是一种生长抑制特异性同源盒转录因子。在体外和体内血管平滑肌中，生长因子会迅速下调Gax，而生长抑制刺激则会缓慢上调Gax。其活性包括通过上调p21表达来阻滞细胞周期，并抑制迁移。在血管内皮细胞中，它也抑制管的形成。此外，Gax的表达诱导了全局基因表达的变化，这与静止表型和NF-kappaB信号的下调一致。这些活性提示我们假设Gax是内皮细胞血管生成表型的重要转录抑制剂。因此，Gax或其下游靶点可能是抗血管生成治疗的一个有希望的靶点。因此，我们提出以下具体目标：

DESCRIPTION (provided by applicant): Malignancies are dependent upon inducing the ingrowth of new blood vessels from the host to supply their oxygen and nutrient needs, and tumor angiogenesis has emerged over the last decade as a promising new target for antitumor therapy. The primary target of tumor-secreted pro- and antiangiogenic factors is the vascular endothelial cell. Our long-term goal is to define the transcriptional regulation of angiogenesis in ECs and use that information to develop new antiangiogenic therapies. Gax is a growth arrest-specific homeobox transcription factor. In vascular smooth muscle in vitro and in vivo, Gax is rapidly downregulated by growth factors and more slowly upregulated by growth arrest stimuli. Its activities include cell cycle arrest via upregulation of p21 expression, and inhibition of migration. In vascular endothelial cells, it also inhibits tube formation. Moreover, Gax expression induces changes in global gene expression consistent with a quiescent phenotype and downregulation of NF-kappaB signaling. These activities suggested to us the hypothesis that Gax is an important transcriptional inhibitor of the angiogenic phenotype in endothelial cells. Consequently, Gax or its downstream targets may represent a promising target for antiangiogenic therapy. We therefore propose these Specific Aims: 1. Identify mechanisms by which Gax regulates EC phenotype by (a) identifying mechanisms that regulate Gax expression in ECs and (b) determining changes in phenotype and global gene expression in ECs that result from modulation of Gax expression. We will examine the effect of both expressing and inhibiting Gax activity in endothelial cells. 2. Determine the mechanism of interaction between Gax expression and the downregulation of NF-kappaB targets in ECs. We will use adenoviral vectors to express Gax in ECs and identify at what point in the NF-kappaB pathway Gax interferes with the activation of NF-kappaB-dependent genes. 3. Determine the function of Gax during in vivo angiogenesis. Gax regulation will be studied during in vivo angiogenesis, and the effect of Gax expression and its inhibition on in vivo angiogenesis will be determined. The results of these studies will significantly enhance our understanding of the transcriptional regulation of endothelial cell phenotypic changes during angiogenesis, characterize a novel interaction between a homeobox gene and NF-kappaB, and provide a basis for designing antiangiogenic therapies that target Gax.