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

项目总结 替莫唑胺(TMZ)化疗是初诊患者治疗的关键组成部分。 胶质母细胞瘤(GBM)，并提供临床上有意义的生存益处。TMZ的细胞毒性由以下原因引起 未能修复TMZ诱导的DNA甲基化加合物。在复制过程中，这些损伤最终会导致 复制叉崩溃与DNA双链断裂相关，这些断裂由同源基因严重修复 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) 组蛋白乙酰转移酶p300(P300)复合体作为关键DNA修复的表观遗传写入者的功能 包括六个关键HR基因(Rad50、BRCA1、BARD1 BRIP1、FIGNL1和RAD51)的过程 在HR途径中扮演不同的角色。具体地说，RBBP4或p300在胶质瘤细胞系和GBM中的敲除 患者来源的异种移植(PDX)模型导致这六种基因产物的显著抑制，受损 HR活性与增强对PARP抑制剂的敏感性有关，并显著增强了对 动物模型中的TMZ。RBBP4/p300复合体下游、溴结构域和端外结构域(BET) 家族成员(BRD2、BRD3、BRD4)是p300介导的乙酰化标记的关键阅读器，以驱动 基因表达。基于这个和我们的初步数据，我们假设RBBP4/p300/BRD轴是一个 是HR效率的关键调节因子，是开发强健、新颖的TMZ的一种有前景的药理策略- 敏化策略。目前有两种p300和双p300/BET抑制剂正在进行临床测试 肿瘤学，强调了充分了解这种复合体如何调节DNA的重要性 修理。我们将从三个具体目标来探讨这一概念： 目的1：明确RBBP4/p300在HR基因调控中的作用。我们将把我们的初步观察扩展到 GBM43以确定该复合体在多个GBM模型中对HR基因的调节。 目的2：评价RBBP4/p300对DNA修复能力的影响。我们假设协调一致 与RBBP4/p300/BET功能中断相关的多个HR基因的抑制导致严重的 HR抑制和TMZ增敏作用与只调节HR的一个组分相比。 目标3：确定靶向p300/BRD4轴对基底膜治疗反应的影响我们将测试 P300和p300/BET抑制剂单独及联合TMZ在PDX模型中的疗效。最终，这些 研究旨在为在GBM的临床试验中追踪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.