Mechanisms and Vulnerabilities of Aberrant Transcriptional Enhancers in Cancer

癌症中异常转录增强子的机制和脆弱性

• 批准号: 9341186
• 负责人: A. THOMAS LOOK
• 金额: $ 104.64万
• 依托单位: DANA-FARBER CANCER INST
• 依托单位国家: 美国
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-09-01 至 2023-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9341186
• 关键词: Acute T Cell Leukemia; Amino Acids; Animal Model; Automobile Driving; Binding; CRISPR/Cas technology; Cancer Cell Growth; Cell Lineage; Cell Survival; Cells; Chromosomal translocation; Chromosome abnormality; Code; DNA Sequence; Dependence; Development; Enhancers; Epigenetic Process; Genetic Transcription; Genomics; Goals; Growth; Human; Insertion Mutation; Malignant - descriptor; Malignant Neoplasms; Mediator of activation protein; Molecular; Mus; Mutagenesis; Mutation; Neoplasm Metastasis; Oncogenes; Oncogenic; Pathogenesis; Patients; Perception; Phenotype; Proteins; RNA Interference; Reader; Research; Role; Site; Somatic Mutation; Structure; TAL1 gene; Testing; Tissues; Up-Regulation; Xenograft procedure; Zebrafish; base; cancer cell; cancer therapy; cell growth; improved; in vivo; insight; leukemia; neoplastic cell; novel; overexpression; programs; success; targeted treatment; therapy design; transcription factor; treatment strategy

Project Summary/Abstract Many important oncogenes in human cancers have normal coding sequences and amino acid structures, but become oncogenic due to genomic abnormalities that create strong transcriptional enhancers. Despite the central role of these aberrant enhancers in malignant transformation, insights into their mechanisms of action are based largely on associated chromosomal abnormalities, such as chromosomal translocations. Very recently, in studies of the oncogene TAL1 in T cell acute lymphoblastic leukemia (T-ALL), we discovered a new mechanism that promises to revise conventional perceptions of the role of aberrant transcriptional enhancers in cancer. We found that small, somatically acquired insertion mutations introduce binding motifs for the MYB transcription factor in a precise noncoding site, creating an aberrant transcriptional enhancer that drives high levels of TAL1 expression. This finding opens the opportunity to investigate how mutations and small insertions are formed in human cancer cells and how they create new enhancers to drive the expression of oncogenes critical for cell growth and survival. Such information will be vital on two fronts. (1) It will provide a conceptual framework for how normal enhancers regulate cell identity in the development of diverse tissues and (2) it will help to clarify the molecular mechanisms that distinguish normal from oncogenic enhancers, thus guiding the development of new targeted cancer treatments. My working hypothesis is that aberrant enhancers formed by somatic mutation in cancer cells are selected to provide the precise levels of oncogene expression needed to promote malignant transformation within a given cell lineage. My long-term goal is to experimentally dissect the specific DNA sequences, transcription factors, transcriptional adaptors and mediators, and epigenetic readers, writers and erasers that are required to form and sustain aberrant transcriptional enhancers capable of driving high levels of key oncogene expression in human cancer cells. To achieve this goal, I will focus initially on the analysis of human T-ALL and AML, and I propose to (i) identify diverse examples of enhancer mutations associated with the overexpression of key oncogenes in these leukemias; (ii) use CRISPR-cas9 mutagenesis to assess the dependence of the tumor cells on novel enhancer mutations for oncogene expression and malignant cell growth and survival; and (iii) define by RNAi which proteins in the epigenetic machinery (e.g., BRD4, CDK7, and CDK9) are required for the target oncogene to be overexpressed in tumor cells and the phenotypic consequences of downregulated expression. Finally, I will construct animal models in zebrafish and primary patient derived xenografts in mice to study molecular pathogenesis of aberrant transcriptional enhancers in vivo. With these animal models I will test strategies to eliminate these tumor cells with therapies designed to specifically target the mechanisms underlying aberrant transcriptional enhancers. Success in this research program will catalyze a paradigm shift in the understanding of oncogenic enhancers and their potential as candidates for targeted therapy.

项目概要/摘要 人类癌症中许多重要的癌基因具有正常的编码序列和氨基酸 结构，但由于基因组异常产生强转录增强子而成为致癌物质。 尽管这些异常增强子在恶性转化中发挥着核心作用，但对其的深入了解 作用机制主要基于相关的染色体异常，例如染色体 易位。最近，在 T 细胞急性淋巴细胞白血病 (T-ALL) 癌基因 TAL1 的研究中， 我们发现了一种新机制，有望改变对异常角色作用的传统看法 癌症中的转录增强子。我们发现小的、体细胞获得性插入突变 在精确的非编码位点引入 MYB 转录因子的结合基序，产生异常 驱动 TAL1 高水平表达的转录增强子。这一发现为我们提供了机会 研究人类癌细胞中如何形成突变和小插入以及它们如何产生新的 增强子驱动对细胞生长和存活至关重要的癌基因的表达。此类信息将 在两个方面都至关重要。 (1)它将为正常增强子如何调节细胞身份提供一个概念框架 不同组织的发育；（2）它将有助于阐明区分的分子机制 正常的致癌增强子，从而指导新的靶向癌症治疗的开发。我的 工作假设是癌细胞中体细胞突变形成的异常增强子被选择 提供在给定范围内促进恶性转化所需的癌基因表达的精确水平 细胞谱系。我的长期目标是通过实验剖析特定的 DNA 序列、转录因子、 转录接头和介体，以及形成所需的表观遗传读取器、写入器和擦除器 并维持异常的转录增强子，能够驱动关键癌基因的高水平表达 人类癌细胞。为了实现这一目标，我将首先关注人类 T-ALL 和 AML 的分析，并且我 提议 (i) 识别与关键基因过度表达相关的增强子突变的不同例子 这些白血病中的癌基因； (ii) 使用CRISPR-cas9诱变来评估肿瘤的依赖性 细胞中致癌基因表达和恶性细胞生长和存活的新型增强子突变； (三) 通过 RNAi 定义表观遗传机制中的哪些蛋白质（例如 BRD4、CDK7 和 CDK9）是 肿瘤细胞中过度表达的靶癌基因及其下调的表型后果 表达。最后，我将在斑马鱼和小鼠中构建原发性患者异种移植动物模型 研究体内异常转录增强子的分子发病机制。有了这些动物模型我会 通过专门针对这些机制设计的疗法来测试消除这些肿瘤细胞的策略 潜在的异常转录增强子。该研究计划的成功将促进范式转变 了解致癌增强剂及其作为靶向治疗候选者的潜力。