Mechanism of angiogenesis inhibition by a homeobox gene

描述(申请人提供)：恶性肿瘤依赖于诱导新血管从宿主体内生长来供应他们的氧气和营养需要，在过去的十年中，肿瘤血管生成已经成为抗肿瘤治疗的一个有前途的新靶点。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。我们的长期目标是定义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是一种生长停滞的同源框转录因子。在体外和体内的血管平滑肌中，Gax被生长因子迅速下调，而在生长停滞刺激下则缓慢上调。它的活性包括通过上调p21的表达而使细胞周期停滞，以及抑制迁移。在血管内皮细胞中，它也抑制管子的形成。此外，Gax的表达诱导了全球基因表达的变化，这与停滞的表型和下调的NF-kappaB信号一致。这些活性向我们提出了Gax是内皮细胞血管生成表型的重要转录抑制因子的假设。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： 1.确定Gax调控EC表型的机制：(A)确定调控ECs中Gax表达的机制；(B)确定由Gax表达调控导致的ECs表型和整体基因表达的变化。我们将研究在内皮细胞中表达和抑制Gax活性的效果。 2.明确内皮细胞Gax表达与NF-kappaB靶标下调的相互作用机制。我们将使用腺病毒载体在内皮细胞中表达Gax，并确定Gax在NF-kappaB途径的哪个点干扰依赖于NF-kappaB的基因的激活。 3.确定Gax在体内血管生成中的作用。将研究Gax在体内血管生成过程中的调控，并确定Gax表达及其对体内血管生成的抑制作用。这些研究的结果将大大加深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，表征同源盒基因与核因子-kappaB之间的一种新的相互作用，并为设计针对Gax的抗血管生成治疗提供基础。

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.