Regulation of Vascular Stabilization by Connexin 43

描述（由申请人提供）：正常血管由内皮细胞小管组成，其与壁细胞（周细胞或平滑肌细胞）支撑层接触，稳定血管并使血管静止。 相反，肿瘤形成的脉管系统高度混乱，并表现出与壁细胞的减少和异常关联。 肿瘤血管系统的这种缺陷给肿瘤控制带来了一些挑战：i）在正常组织中，壁细胞阻止内皮增殖，缺乏功能性壁细胞关联使肿瘤刺激内皮增殖并产生新血管来喂养肿瘤； ii) 壁细胞的缺乏使血管更容易受到肿瘤内渗的影响，导致转移； iii) 有缺陷的肿瘤血管的渗漏减少了治疗药物的输送。 我们寻求通过治疗来克服这些缺陷。 我们的初步数据表明，连接分子 Connexin 43 (Cx43) 在稳定正常血管方面发挥着先前未知的作用。 此外，乳腺和脑肿瘤细胞下调壁细胞 Cx43 或使其失活，以破坏它们与内皮细胞的相互作用。 基于这些新发现，我们将研究以下假设：肿瘤诱导的 Cx43 抑制在肿瘤血管不稳定中发挥重要作用，而血管 Cx43 的恢复将逆转有害影响。 为了研究这一假设，我们提出了三个具体目标：1）确定肿瘤暴露血管细胞中 Cx43 活性的调节因子； 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渗透性。 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的 Cx43 突变体来定义肿瘤改变 Cx43 表达和功能的机制。 我们还将测试据报道上调 Cx43 和/或增强血管稳定性的化合物的能力，以克服肿瘤诱导的血管细胞中功能性 Cx43 的丧失。 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是否在 Cx43 宿主缺陷背景下增强，以及 Cx43 过度表达是否会通过血管稳定来预防或延迟这些事件。 这些研究将共同​​确定 Cx43 在血管稳定性中的作用，并阐明其功能在病理性脉管系统中丧失的机制。 拟议研究的成功将确定 Cx43 是使肿瘤脉管系统正常化的新靶点，从而抑制血管生成，并有可能减少转移并增强药物输送，最终实现更好的癌症控制。

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.