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

项目摘要 替莫唑胺（TMZ）化疗是治疗新诊断患者的关键组成部分， 胶质母细胞瘤（GBM），并提供临床上有意义的生存益处。TMZ的细胞毒性来自 不能修复TMZ诱导的DNA甲基化加合物。在复制过程中，这些病变最终导致 与DNA双链断裂相关的复制叉塌陷， 重组（HR）。在这种情况下，我们最近发现视网膜母细胞瘤结合蛋白4（RBBP 4） 与组蛋白乙酰转移酶p300（p300）形成复合物，作为表观遗传书写者，对DNA修复起关键作用 包括六个关键的HR基因（RAD 50，BRCA 1，BARD 1 BRIP 1 FIGNL 1和RAD 51）， 在HR路径中的不同角色。具体地，在胶质瘤细胞系和GBM中RBBP 4或p300的敲低 患者来源的异种移植物（PDX）模型导致这六种基因产物的显著抑制， HR活性与对PARP抑制剂的敏感性增强相关，并显著增强对 动物模型中的TMZ。RBBP 4/p300复合物下游，溴结构域和末端外结构域（BET） 家族成员（BRD 2、BRD 3、BRD 4）作为p300介导的乙酰化标记的关键阅读器， 基因表达。基于这一点和我们的初步数据，我们假设RBBP 4/p300/BRD轴是一个基因调控系统。 HR效率的关键调节因子，是开发一种稳健的、新型的TMZ的有前途的药理学策略， 敏感战略。目前，p300和p300/BET双重抑制剂正在进入临床试验。 肿瘤学，它强调了充分理解这种复杂功能如何调节DNA的重要性 修复.我们将在一系列三个具体目标中探讨这一概念： 目的1：明确RBBP 4/p300在HR基因调控中的作用。我们将把我们最初的观察扩展到 GBM 43来定义该复合物在多种GBM模型中对HR基因的调节。 目的2：评估RBBP 4/p300对DNA修复能力的影响。我们假设， 与RBBP 4/p300/BET功能破坏相关的多个HR基因的抑制导致了深刻的 与仅调节HR的一种组分相比，HR抑制和TMZ增敏作用。 目的3：确定靶向p300/BRD 4轴对GBM治疗反应的影响。 p300和p300/BET抑制剂单独和与TMZ组合在PDX模型中的功效。最终，这些 研究旨在为在GBM的临床试验中寻求这些抑制剂提供强有力的理论基础。

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.