Radiation-induced vascular reprogramming in glioblastoma

摘要 胶质母细胞瘤(GBM)是最常见的原发脑肿瘤，几乎总是致命的。的主要模式 治疗--手术、放疗和替莫唑胺化疗--只带来了轻微的改善 生死存亡。肾小球基底膜的一个特点是血管密度高。基底膜内的血管，主要由 内皮细胞和周细胞不仅为肿瘤提供营养和氧气， 而且还为肿瘤细胞提供直接的营养支持，并充当肿瘤外迁移的管道。 然而，针对肿瘤血管的抗血管生成治疗并不成功。一批 研究表明，肿瘤周细胞和血管内皮细胞可以直接来源于肿瘤细胞， 尽管肿瘤来源的内皮细胞在未经治疗的肿瘤中相对罕见。数量 肿瘤来源的内皮细胞在复发肿瘤中显著增加，提示胶质瘤治疗，如 作为辐射，可以影响这一过程。我们的初步研究表明，辐射可以诱导 在体外和体内动物模型中产生内皮样细胞和周细胞样细胞。这些重新编程 细胞对体内放射后肿瘤的生长很重要，我们已经开始定义 重新编程的血管细胞产生的支持剩余肿瘤细胞生长的因子 辐射。我们的初步数据表明，辐射会引起染色质状态的改变，从而允许 重新编程发生；一个潜在的治疗目标的过程，通过抑制 组蛋白乙酰转移酶(HAT)，P300。当前研究的目标是了解 血管重编程(RIR)及其对脑肿瘤生物学的影响。我们的假设是 血管重编程细胞在严酷的环境下为残留的肿瘤细胞提供关键的营养支持 辐射后发生的状况。首先，在目标1中，我们将确定在治疗上是否相关 辐射剂量可促进血管RIR。然后我们将使用细胞消融策略来验证我们初步的 数据表明，辐射诱导的重编程对肿瘤的后续生长很重要 在使用异种移植和免疫活性同基因小鼠模型进行放射治疗后。 接下来，我们将探索辐射对内皮样细胞和周细胞样细胞重新编程的机制 促进剩余肿瘤的生长，确定它们阐述的具体因素，以及 这些因素与肿瘤在放射治疗后的存活和生长有关。然后我们将检验这一假设 辐射通过改变染色质的可及性来诱导血管样细胞的形成 通过P300组蛋白乙酰转移酶增强组蛋白乙酰化，允许进入 血管特异性转录因子。最后，我们将使用药理药物来治疗 通过抑制P300 HAT对RIR的作用。这些实验可以使我们对 放射治疗抵抗的潜在机制，并为新的治疗方法打开大门。

Summary Glioblastoma (GBM), the most common primary brain tumor is virtually always fatal. The primary modes of therapy—surgery, radiation and chemotherapy with temozolomide—have led to only marginal improvements in survival. A hallmark of GBM is their high vascularity. Blood vessels within GBM, consisting of mostly endothelial cells and pericytes, not only play the important role of providing nutrients and oxygen to the tumor, but also provide direct trophic support to the tumor cells and serve as conduits for migration out of the tumor. However, anti-angiogenic therapies directed against tumor vasculature have not been successful. A number of studies have revealed that tumor pericytes and endothelial cells can be derived directly from tumor cells, although tumor-derived endothelial cells are relatively rare occurrences in untreated tumors. The number of tumor-derived endothelial cells is greatly increased in recurrent tumors, suggesting that glioma therapy, such as radiation, could influence this process. Our preliminary studies show that radiation can induce the production of endothelial-like and pericyte-like cells in vitro and in animal models in vivo. These reprogrammed cells are important for the growth of the tumor following radiation in vivo and we have begun to define what factors the reprogrammed vascular cells produce to support the growth of the remaining tumor cells following radiation. Our preliminary data indicate that radiation induces altered chromatin states that allow for reprogramming to occur; a process that is potentially therapeutically targetable through the inhibition of the histone acetyltransferase (HAT), P300. The goals of the current studies are to understand the process of vascular reprogramming (RIR) and to determine how it influences brain tumor biology. Our hypothesis is that vascular reprogrammed cells provide critical trophic support to the remaining tumor cells under the harsh conditions that occur following radiation. First, in Aim 1 we will determine whether therapeutically relevant doses of radiation promote vascular RIR. We will then use cell ablation strategies to validate our preliminary data indicating that radiation-induced reprogramming is important for the subsequent growth of the tumor following radiation treatment using both xenotransplantation and immunocompetent syngeneic mouse models. Next, we will explore the mechanisms by which radiation reprogrammed endothelial-like and pericyte-like cells promote the growth of the remaining tumor, determining what specific factors they elaborate, and whether these factors are responsible for tumor survival and growth following radiation. We will then test the hypothesis that radiation induces the formation of vascular-like cells through modification of chromatin accessibility via augmentation of histone acetylation through the P300 histone acetyltransferase, allowing for access of vascular-specifying transcription factors. Finally, we will use pharmacologic agents to therapeutically target the process of RIR through inhibition of the P300 HAT. These experiments can lead to a new understanding of mechanisms underlying resistance to radiation therapy and open the door to new treatments.