Genotypic Interactions in Brain Cancer Heterogeneity

脑癌异质性中的基因型相互作用

• 批准号: 10375989
• 负责人: Frank Furnari
• 金额: $ 17.75万
• 依托单位: UNIVERSITY OF CALIFORNIA, SAN DIEGO
• 依托单位国家: 美国
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-09-01 至 2023-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10375989
• 关键词: Genotypic; Interactions; Brain; Cancer; Heterogeneity

Project Summary Minimal improvement in the 12-15 month average survival of patients with glioblastoma multiforme (GBM) has been achieved despite decades of advances in neurosurgery and radiation therapy, many clinical trials for novel therapeutics, and increased understanding of the driving molecular mechanisms. A central issue that confounds successful treatment is the heterogeneous nature of this aggressive tumor. This heterogeneity presents phenotypically as mixed cytological subtypes, genotypically as mutations and gene amplifications, and transcriptionally as regional differences in gene expression. As a result, multiple and spatially distinct heterotypic populations exist within a single GBM, making any lesion- or pathway-specific therapy less effective. While considerable effort has been placed on understanding cell intrinsic mechanisms conferring therapeutic resistance, much less is known about the interactions between heterogeneous tumor cells within these neoplasms that contribute to the recalcitrant nature of this cancer. In GBM, amplification of the epidermal growth factor receptor, a hallmark mutation present in 60% of cases, often occurs in a heterogeneous manner and is frequently associated with structural alterations. The most common of these alterations, EGFRvIII, (also known as ∆EGFR) results in a constitutively active mutant receptor with tumor enhancing capability. This ability is lacking from amplified wtEGFR despite its more pervasive tumor expression. By modeling this type of genetic heterogeneity in vivo, we have determined that an IL-6 paracrine signaling mechanism driven by EGFRvIII activity can not only recruit wtEGFR-expressing cells into accelerated proliferation, but also promote EGFR-targeted therapeutic resistance through activation of a pro-survival inflammatory NF-κB/BRD4 signaling axis. Given the central role of NF-κB/BRD4 in the remodeling of chromatin super enhancers we postulate that EGFRvIII/wtEGFR sub-population interactions not only enhance aggressive tumor growth, but also prompt the synchronization of aspects of gene expression in these heterotypic cells through shared enhancer remodeling. The overall goal of this renewal project is to dissect and target the mechanisms whereby GBM EGFR/EGFRvIII heterogeneity drives therapeutic resistance through orchestration of NF-κB/BRD4-mediated remodeling of the epigenetic landscape. The following lines of experimentation will be carried out: 1) genome editing to create a drug-selective BRD4 allele for mechanistic chemical biology studies; 2) use of this modified BRD4 allele as a tool for chromatin structure and functional analysis of the cytokine-stimulated NF-κB/BRD4 enhancer landscape in heterotypic and subpopulation-ablated gliomas; 3) genetic and pharmacological inhibition of identified NF-κB/BRD4-mediated genetic or epigenetic vulnerabilities shared among EGFR and EGFRvIII heterotypic cells to enhance therapeutic efficacy.

项目摘要 多形性胶质母细胞瘤（GBM）患者12-15个月平均生存期的微小改善， 尽管在神经外科和放射治疗方面取得了数十年的进展，但许多临床试验 新的治疗方法，并增加对驱动分子机制的理解。一个核心问题， 这种侵袭性肿瘤的异质性是导致治疗失败的主要原因。这种异质性 表现为混合细胞学亚型，基因型为突变和基因扩增， 以及基因表达的区域差异。因此，多个和空间上不同的 异型群体存在于单个GBM中，使得任何病变或通路特异性治疗都不那么有效。 有效虽然相当大的努力已经放在理解细胞内在机制赋予 由于治疗耐药性，人们对体内异质肿瘤细胞之间的相互作用知之甚少 这些肿瘤导致了这种癌症的恶性性质。在GBM中， 表皮生长因子受体是一种标志性突变，存在于60%的病例中，通常发生在 它是一种异质性的方式，经常与结构改变有关。其中最常见的 EGFRvIII（也称为EGFR）的改变导致了一种组成型活性突变受体， 增强能力。扩增的wtEGFR缺乏这种能力，尽管其更普遍的肿瘤 表情通过在体内模拟这种类型的遗传异质性，我们已经确定IL-6旁分泌 由EGFRvIII活性驱动的信号传导机制不仅可以将表达wtEGFR的细胞募集到加速的细胞内， 增殖，而且还通过激活促存活因子促进EGFR靶向治疗抗性。 炎症NF-κB/BRD 4信号轴。考虑到NF-κB/BRD 4在细胞重构中的核心作用， 我们假设EGFRvIII/wtEGFR亚群的相互作用不仅增强了 侵袭性肿瘤生长，而且还促使这些基因表达方面的同步化， 异型细胞通过共享增强子重塑。 该更新项目的总体目标是剖析和靶向GBM EGFR/EGFRvIII的机制， 异质性通过协调NF-κB/BRD 4介导的细胞重构驱动治疗抗性， 表观遗传景观将进行以下实验：1）基因组编辑，以创建一个 用于机理化学生物学研究的药物选择性BRD 4等位基因; 2）使用该修饰的BRD 4等位基因作为药物选择性BRD 4等位基因， 一种用于染色质结构和分析丝氨酸刺激的NF-κB/BRD 4增强子功能的工具 异型和亚群消融胶质瘤的景观; 3）遗传和药理学抑制 确定了EGFR和EGFRvIII之间共有的NF-κB/BRD 4介导的遗传或表观遗传脆弱性 异型细胞以增强治疗功效。