KLF4 and Transcriptional Control of Neovascularization

描述(申请人提供)：调节血管生长，使正常组织在发育、动态平衡和伤口修复期间获得足够的氧气和营养，同时也是内皮的中心功能之一。在肿瘤生长过程中，血管生长的正常调节机制被改变，新血管的形成，通过萌芽的血管生成，允许恶性组织的侵袭性生长。在美国，缺血性血管疾病和癌症分别是导致死亡的第一和第二大原因。由于我们对这些疾病状态的治疗还不够充分，更好地了解控制它们的细胞信号通路具有相当大的科学和治疗兴趣。Kruppel样因子(KLFs)是一个锌指蛋白家族，调节转录，参与广泛的生物过程。然而，KLF家族在血管生长中的作用尚不清楚。根据我们的初步研究，我们发现该家族的第四个成员(KLF4)调节肿瘤的血管生成和动脉生成。功能获得和功能丧失的研究表明，KLF4调节几个关键的血管生成因子，包括Notch信号通路的成员。内皮特异性过表达KLF4的小鼠肿瘤血管密度增加，但肿瘤体积较小。对肿瘤血管的评估表明，KLF4的过度表达导致无效的多血管生成-血管生成增强，但新的血管低灌流，限制了肿瘤的生长。在肢体缺血研究中，内皮细胞KLF4过表达导致股动脉结扎后即刻血流量减少(天然侧支功能降低)，但在恢复期促进侧支重构，血流量迅速变得与WT动物相等。对脑软脑膜侧支血管的评估显示侧支血管密度降低，这与骨骼肌侧支减少的推测一致，这是导致结扎后即刻远端血流受限的原因。脑微血管和气管粘膜毛细血管密度增加；其原因尚不清楚，将成为未来研究的主题。KLF4过表达所见的新生血管表型与Notch信号改变的动物所描述的表型相似。Notch激活在几种新生血管模式中具有公认的核心作用，Notch调节疗法正在考虑临床应用。这些观察结果为中心假说提供了基础，KLF4是一种新的新生血管调节因子，并且作为Notch的上游调节因子发挥作用。为了更好地理解KLF4在这一过程中的确切作用，提出了三个目标。在目标1中，我们将确定KLF4在萌芽血管生成和血管模式形成中的作用。在目标2中，我们将确定EC KLF4的过度表达和缺失在侧化中的作用。在目标3中，我们将确定KLF4和Notch之间的精确分子关系。总而言之，这些研究将定义一种新的途径，从细胞核到血管网络，调节血管生长。这些研究的结果可能为治疗肿瘤生长或动脉粥样硬化性血管疾病提供有益的新疗法。

DESCRIPTION (provided by applicant): Regulation of blood vessel growth so that normal tissues receive sufficient oxygen and nutrients during development, homeostasis, and wound repair while is one of the central functions of the endothelium. During tumor growth, normal regulatory mechanisms of vessel growth are altered, and new vessels formation, via sprouting angiogenesis, occur allowing aggressive growth of the malignant tissue. Ischemic vascular disease and cancer are the first and second, respectively, leading cause of mortality in the United States. As our treatments for these disease states are insufficient, a better understanding of the cellular signaling pathways that control them is of considerable scientific and therapeutic interest. Kruppel-like Factors (KLFs) are a family of zinc finger proteins that regulate transcription and are implicated in a wide spectrum of biologic processes. However, a role for the KLF family in blood vessel growth is unknown. Based on our preliminary studies, we find that the 4th member of this family (KLF4) regulates tumor angiogenesis and arteriogenesis. Gain- and loss-of-function studies reveal that KLF4 regulates several critical angiogenic factors including members of the Notch signaling pathway. Mice with endothelial-specific overexpression of KLF4 have increased tumor blood vessel density, but smaller tumor size. Assessment of the tumor vasculature suggests that KLF4 overexpression leads to ineffective hypervascularity- angiogenesis is enhanced , but the new vessels are hypoperfused, limiting tumor growth. In hindlimb ischemia studies endothelial KLF4 overexpression leads to poor blood flow immediately post femoral artery ligation (decreased function of native collaterals), but enhanced collateral remodeling during the recovery period, with blood flow quickly becoming equal to WT animals. Assessment of cerebral pial collateral vessels shows decreased collateral density, consistent with the presumed decrease in skeletal muscle collaterals that cause the limited distal flow immediately post ligation. Cerebral microvessels and tracheal mucosal capillaries are increased in density; the cause of this is yet unknown and will be a topic for futue studies. The neovascularization phenotypes seen with KLF4 overexpression are reminiscent of those described in animals with altered Notch signaling. Notch activation has a well-established central role in several modes of neovascularization, and Notch-modulating therapies are under consideration for clinical use. These observations provide the foundation for the central hypothesis the KLF4 is a novel regulator of neovascularization, and functions as an upstream regulator of Notch. To better understand the precise role of KLF4 in this process, three aims are proposed. In Aim 1, we will define the role of KLF4 in sprouting angiogenesis and vascular patterning. In Aim 2 we will determine the role of EC KLF4 overexpression and deficiency on collateralization. In Aim 3, we will determine the precise molecular relationship between KLF4 and Notch. Collectively, these studies will define a novel pathway, from nucleus to vascular network, that regulates blood vessel growth. The results of these studies may provide new therapies beneficial in the treatment of tumor growth or atherosclerotic vascular disease.