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血管向内生长来满足其氧气和营养需求，并且肿瘤血管生成在过去十年中已成为抗肿瘤治疗的有前景的新靶点。 肿瘤分泌的促血管生成因子和抗血管生成因子的主要靶标是血管内皮细胞。 我们的长期目标是确定内皮细胞中血管生成的转录调控，并利用该信息开发新的抗血管生成疗法。 Gax 是一种生长停滞特异性同源盒转录因子。 在体外和体内的血管平滑肌中，Gax 被生长因子快速下调，并被生长停滞刺激更缓慢地上调。 其活性包括通过上调 p21 表达来抑制细胞周期以及抑制迁移。 在血管内皮细胞中，它还抑制管形成。 此外，Gax 表达诱导与静止表型一致的全局基因表达变化和 NF-kappaB 信号传导下调。 这些活动向我们提出了这样的假设：Gax 是内皮细胞中血管生成表型的重要转录抑制剂。 因此，Gax 或其下游靶标可能代表抗血管生成治疗的有希望的靶标。 因此，我们提出以下具体目标： 1. 通过以下方式确定 Gax 调节 EC 表型的机制：(a) 确定调节 EC 中 Gax 表达的机制；(b) 确定 EC 中由 Gax 表达调节引起的表型和全局基因表达的变化。 我们将检查内皮细胞中表达和抑制 Gax 活性的效果。 2. 确定 EC 中 Gax 表达与 NF-kappaB 靶标下调之间的相互作用机制。 我们将使用腺病毒载体在 EC 中表达 Gax，并确定 Gax 在 NF-kappaB 途径中的哪个点干扰 NF-kappaB 依赖性基因的激活。 3.确定Gax在体内血管生成过程中的功能。 研究体内血管生成过程中Gax的调控，确定Gax表达及其对体内血管生成的抑制作用。 这些研究的结果将显着增强我们对血管生成过程中内皮细胞表型变化的转录调控的理解，表征同源盒基因和 NF-κB 之间的新型相互作用，并为设计针对 Gax 的抗血管生成疗法提供基础。

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.