Regulation of Vascular Stabilization by Connexin 43

描述（由申请人提供）：正常血管由与壁细胞（周细胞或平滑肌细胞）支持层接触的内皮细胞小管组成，壁细胞支持层稳定血管并使血管静止。 相比之下，由肿瘤形成的脉管系统是高度紊乱的，并且表现出与壁细胞的减少和异常的关联。 肿瘤脉管系统中的这种缺陷在肿瘤控制中引起几个挑战：i）虽然在正常组织中，壁细胞阻止内皮增殖，但功能性壁细胞缔合的缺乏允许肿瘤刺激内皮增殖并产生新血管以供给肿瘤; ii）壁细胞的缺乏使血管更容易受到肿瘤内渗，导致转移;和iii）缺陷肿瘤血管的渗漏减少治疗药物的递送。 我们试图了解治疗克服这些缺陷。 我们的初步数据表明，连接分子连接蛋白43（Cx43）发挥了以前未确定的作用，在稳定正常血管。 此外，乳腺癌和脑肿瘤细胞下调或破坏壁细胞Cx43以破坏其与内皮细胞的相互作用。 基于这些新的发现，我们将调查的假设，肿瘤诱导的抑制Cx43发挥了重要作用，在肿瘤血管的不稳定和血管Cx43的恢复将扭转有害的影响。 为了研究这一假设，我们提出了三个具体的目标：1）确定Cx43在肿瘤暴露的血管细胞中的活性调节因子; 2）确定改变的宿主Cx43是否影响同基因乳腺肿瘤的生长、血管生成或转移; 3）确定改变的宿主Cx43是否影响血管完整性和通透性。 在目标1中，我们将使用药理学抑制剂，位点特异性Cx43磷酸化突变体和间隙连接缺陷型Cx43突变体来定义肿瘤改变Cx43表达和功能的机制。 我们还将测试所报道的上调Cx43和/或增强血管稳定性的化合物克服血管细胞中肿瘤诱导的功能性Cx43丧失的能力。 在目标2和3中，我们将使用同基因小鼠乳腺肿瘤模型来研究肿瘤血管生成、转移、血管通透性和间质液压力是否在Cx43宿主缺陷背景下增强，以及Cx43过表达是否会通过血管稳定来预防或延迟这些事件。 总之，这些研究将确定Cx43在血管稳定性中的作用，并阐明其功能在病理性血管系统中丧失的机制。 所提出的研究的成功将确定Cx43作为使肿瘤血管正常化的新靶点，从而抑制血管生成，并可能减少转移和增强药物递送，最终导致更好的癌症控制。 公共卫生相关性：在肿瘤中发现的渗漏、不稳定的血管促进肿瘤生长，损害药物递送，并促进转移。 拟议研究的成功将确定血管连接蛋白43作为使肿瘤血管正常化的新靶点，从而抑制血管生成，减少转移，增强药物递送，最终导致更好的癌症控制。

DESCRIPTION (provided by applicant): A normal blood vessel is composed of a tubule of endothelial cells in contact with a supporting layer of mural cells (pericytes or smooth muscle cells) that stabilize the vessel and render the vessel quiescent. In contrast, the vasculature formed by a tumor is highly disorganized and exhibits decreased and abnormal association with mural cells. This defect in tumor vasculature causes several challenges in tumor control: i) while in normal tissues, mural cells prevent the endothelium from proliferating, lack of functional mural cell association allows tumor to stimulate endothelial proliferation and generate new vessels to feed the tumors; ii) the lack of mural cells makes vessels more susceptible to tumor intravasation, leading to metastasis; and iii) the leakiness of defective tumor vessels decreases delivery of therapeutic drugs. We seek to understand therapeutically overcome these defects. Our preliminary data demonstrate that the junctional molecule Connexin 43 (Cx43) plays a previously unidentified role in stabilization of normal blood vessels. Moreover, breast and brain tumor cells downregulate or inactivate mural cell Cx43 to disrupt their interaction with endothelial cell. Based on these novel findings we will investigate the hypothesis that tumor-induced inhibition of Cx43 plays a major role in destabilization of tumor blood vessels and that restoration of vascular Cx43 will reverse the deleterious effects. To investigate this hypothesis, we propose three specific aims: 1) To identify regulators of Cx43 activity in tumor-exposed vascular cells; 2) To determine whether altered host Cx43 affects the growth, angiogenesis, or metastasis of syngeneic mammary tumors; and 3) To determine whether altered host Cx43 affects vessel integrity and permeability. In Aim 1 we will use pharmacological inhibitors, site-specific Cx43 phosphorylation mutants, and gap junction-deficient Cx43 mutants to define the mechanism(s) by which tumor alters Cx43 expression and function. We will also test the ability of compounds reported to upregulate Cx43 and/or enhance vessel stability to override tumor-induced loss of functional Cx43 in vascular cells. In Aims 2 and 3, we will use a syngeneic mouse mammary tumor model to address whether tumor angiogenesis, metastasis, vascular permeability and interstitial fluid pressure are enhanced on a Cx43 host-deficient background, and whether Cx43 overexpression will prevent or delay these events via vascular stabilization. Together, these studies will define the role of Cx43 in blood vessel stability and elucidate the mechanism by which its function is lost in a pathological vasculature. Success of the proposed studies will identify Cx43 as a novel target to normalize tumor vasculature, thereby inhibiting angiogenesis, and potentially decreasing metastasis and enhancing drug delivery, ultimately leading to better cancer control. PUBLIC HEALTH RELEVANCE: The leaky, unstable blood vessels found in tumors facilitate tumor growth, impair drug delivery, and facilitate metastasis. Success of the proposed studies will identify vascular Connexin 43 as a novel target to normalize the tumor vasculature and thereby inhibit angiogenesis, decrease metastasis, and enhance drug delivery, ultimately leading to better cancer control.