Nitric Oxide in Tumor Angiogenesis, Microcirculation and Radiation Therapy

描述(由申请人提供)：对肿瘤血流的可重复控制，这是将药物和氧气最佳输送到实体肿瘤所必需的，仍然是一个难以实现的目标。一氧化氮(NO)是一系列生理和病理过程的多功能介体。已有研究表明，血管内皮细胞来源的一氧化氮合酶可诱导血管生成，维持肿瘤血流量。最近的研究结果表明，血管NO参与了血管周围细胞向新生血管的募集，以及血管的分枝、纵向伸展和随后的稳定。然而，初步研究表明，血管区域外的肿瘤和间质细胞产生的NO可能与血管成熟过程竞争。该项目的中心假设是，选择性地将NO定位在血管周围，可以改善肿瘤血管的形态和功能，改善药物和氧气的输送，从而提高伴随的细胞毒治疗的疗效。 将研究在透明窗模型中生长的小鼠原位胶质瘤和乳腺肿瘤。在目标1中，通过遗传和药物修饰的手段，阻断非血管来源的NO产生，增加血管NO的产生。这些修饰对肿瘤血管功能和组织氧合的影响将通过高分辨率活体显微镜技术和免疫组织化学来确定。将使用荧光报告转基因小鼠在体内监测血管周围细胞。最后，将确定在不修改的情况下肿瘤对分割辐射的反应。 血管生成素(Ang)-Tie2途径已被证明通过血管周围细胞募集来调节血管成熟。在目标2中，将利用最近建立的体外迁移分析和组织工程血管模型以及肿瘤模型来确定血管NO参与Ang-Tiie2诱导的血管周围细胞募集以及NO依赖的血管周围细胞募集的下游信号转导。 最近的研究结果表明，阻断血管内皮生长因子受体2(VEGFR2)可通过Tie2受体信号转导，短暂改善肿瘤血管周围细胞覆盖率、组织氧合和放射治疗反应。在目标3中，将使用目标1的模型和方法来确定血管NO在抗VEGFR2治疗诱导的血管效应中的作用以及血管选择性定位NO对联合抗VEGFR2和放射治疗的疗效的影响。 为了支持中心假说，初步研究表明，消除非血管来源的NO可以改善肿瘤血管的结构和功能，并增强肿瘤对分割放射治疗的反应。该项目将促进对NO介导的血管成熟的基本理解，并有助于开发新的策略来改善药物和氧气向肿瘤的输送。

DESCRIPTION (provided by applicant): The reproducible control of tumor blood flow, which is required for the optimal delivery of drugs and oxygen to solid tumors, remains an elusive goal. Nitric oxide (NO) is a multifunctional mediator of an array of physiological and pathological processes. It has been shown that NO derived from vascular endothelial NO synthase induces angiogenesis and maintains tumor blood flow. Recent results show that vascular NO mediates the recruitment of perivascular cells to angiogenic vessels, as well as the branching, longitudinal extension and subsequent stabilization of the vessels. However, preliminary studies suggest that NO produced by tumor and stromal cells outside the vascular area may compete with the process of vessel maturation. The central hypothesis of this project is that selective localization of NO around blood vessels improves tumor vascular morphology and function, the delivery of drugs and oxygen, and thus the efficacy of concomitant cytotoxic therapy. Orthotopic glioma and breast tumors grown in transparent window models in mice will be studied. In Aim 1, non-vascular sources of NO production will be blocked and vascular NO will be increased by means of genetic and pharmacological modifications. The effect of these modifications on tumor vascular function and tissue oxygenation will be determined by high-resolution intravital microscopy techniques and immunohistochemistry. Perivascular cells will be monitored in vivo using fluorescence-reporter transgenic mice. Finally, the tumor response to fractionated radiation during NO modifications will be determined. The angiopoietin (Ang)-Tie2 pathway has been shown to mediate vessel maturation via perivascular cell recruitment. In Aim 2, involvement of vascular NO in Ang-Tie2-induced perivascular cell recruitment as well as in downstream signaling of NO-dependent perivascular cell recruitment will be determined using recently established in vitro migration assays and a tissue-engineered blood vessel model as well as tumor models. Recent results show that blockade of vascular endothelial growth factor receptor 2 (VEGFR2) transiently improves perivascular cell coverage, tissue oxygenation and response to radiation therapy in tumors via Tie2 receptor signaling. In Aim 3, the role of vascular NO in anti-VEGFR2 treatment-induced vascular effects and the impact of vessel-selective localization of NO on the efficacy of combined anti-VEGFR2 and radiation treatments will be determined using the models and methods of Aim 1. In support of the central hypothesis, preliminary studies show that elimination of non-vascular sources of NO improves the structure and function of tumor vessels and enhances tumor response to fractionated radiation therapy. This project will advance the basic understanding of NO-mediated vessel maturation and help develop novel strategies to improve the delivery of drugs and oxygen to tumors.