Role of RBBP4/p300 Complex in Recovery from therapy induced DNA damage in glioblastoma

项目概要 替莫唑胺 (TMZ) 化疗是新诊断患者治疗的关键组成部分 胶质母细胞瘤（GBM）并提供具有临床意义的生存益处。 TMZ 的细胞毒性来自 未能修复 TMZ 诱导的 DNA 甲基化加合物。在复制过程中，这些损伤最终导致 复制叉崩溃与 DNA 双链断裂相关，同源基因严重修复 重组（HR）。在此背景下，我们最近发现视网膜母细胞瘤结合蛋白 4 (RBBP4) 在与组蛋白乙酰转移酶 p300 (p300) 的复合物中发挥作用，作为关键 DNA 修复的表观遗传写入者 包括六个关键 HR 基因（RAD50、BRCA1、BARD1、BRIP1FigNL1 和 RAD51） HR 路径中的不同角色。具体来说，在神经胶质瘤细胞系和 GBM 中敲低 RBBP4 或 p300 患者来源的异种移植（PDX）模型导致这六种基因产物的显着抑制，受损 HR 活性与 PARP 抑制剂的敏感性增强相关，并且显着增强对 PARP 抑制剂的敏感性 TMZ 在动物模型中的应用。 RBBP4/p300 复合物、溴结构域和末端外结构域 (BET) 的下游 家族成员（BRD2、BRD3、BRD4）作为 p300 介导的乙酰化标记的关键读者来驱动 基因表达。基于此和我们的初步数据，我们假设 RBBP4/p300/BRD 轴是 HR 效率的关键调节剂，是一种有前途的药理学策略，可用于开发稳健、新颖的 TMZ- 敏化策略。 p300 抑制剂和双 p300/BET 抑制剂现已进入临床测试 肿瘤学，强调充分理解这种复合物如何发挥 DNA 调节作用的重要性 修复。我们将通过一系列三个具体目标来探索这个概念： 目标 1：定义 RBBP4/p300 在 HR 基因调节中的作用。我们将扩展我们的初步观察 GBM43 定义了该复合体对多个 GBM 模型的 HR 基因的调节。 目标 2：评估 RBBP4/p300 对 DNA 修复能力的影响。我们假设协调 抑制与 RBBP4/p300/BET 功能破坏相关的多个 HR 基因会导致严重的后果 与仅调节 HR 的一种成分相比，HR 抑制和 TMZ 敏化作用。 目标 3：定义靶向 p300/BRD4 轴对 GBM 治疗反应的影响 我们将测试 p300 和 p300/BET 抑制剂单独使用以及与 TMZ 联合使用在 PDX 模型中的疗效。最终，这些 研究旨在为在 GBM 临床试验中寻求这些抑制剂提供强有力的理由。

PROJECT SUMMARY Temozolomide (TMZ) chemotherapy is a key component of treatment for patients with newly diagnosed glioblastoma (GBM) and provides clinically meaningful survival benefits. Cytotoxicity from TMZ results from failure to repair TMZ-induced DNA methylation adducts. During replication, these lesions ultimately result in replication fork collapse associated with DNA double strand breaks that are critically repaired by homologous recombination (HR). In this context, we recently discovered that retinoblastoma binging protein 4 (RBBP4) functions in a complex with histone acetyltransferase p300 (p300) as a epigenetic writer to key DNA repair processes including six key HR genes (RAD50, BRCA1, BARD1 BRIP1 FIGNL1, and RAD51) that play different roles in HR pathway. Specifically, knockdown of either RBBP4 or p300 in glioma cell lines and GBM patient-derived xenograft (PDX) models results in marked suppression of these six gene products, impaired HR activity associated with enhanced sensitivity to PARP inhibitors, and dramatically enhanced sensitivity to TMZ in animal models. Downstream of RBBP4/p300 complex, bromodomain and extraterminal domain (BET) family members (BRD2, BRD3, BRD4) function as key readers of p300-mediated acetylation marks to drive gene expression. Based on this and our preliminary data, we hypothesize that the RBBP4/p300/BRD axis is a key regulator of HR efficiency and is a promising pharmacologic strategy for developing a robust, novel, TMZ- sensitizing strategy. There are both p300- and dual p300/BET-inhibitors now entering clinical testing in oncology, which highlight the importance of fully understanding how this complex functions to regulate DNA repair. We will explore this concept in a series of three specific aims: Aim 1: Define the role of RBBP4/p300 in regulation of HR genes. We will extend our initial observations in GBM43 to define the regulation of HR genes across multiple GBM models by this complex. Aim 2: Evaluate the impact of RBBP4/p300 on DNA repair proficiency. We hypothesize that coordinated suppression of multiple HR genes associated with disruption of RBBP4/p300/BET function results in profound HR suppression and TMZ sensitizing effects as compared to modulation of only one component of HR. Aim 3: Define the impact of targeting the p300/BRD4 axis on therapy response in GBM We will test the efficacy of p300 and p300/BET inhibitors alone and in combination with TMZ in PDX models. Ultimately, these studies are designed to provide a strong rationale to pursue these inhibitors in clinical trials for GBM.