SWI/SNF complex loss facilitates gene silencing during NSCLC development

SWI/SNF 复合物丢失促进 NSCLC 发展过程中的基因沉默

• 批准号: 7635080
• 负责人: Bernard E. Weissman
• 金额: $ 30.71万
• 依托单位: UNIV OF NORTH CAROLINA CHAPEL HILL
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-07-17 至 2011-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7635080
• 关键词: ATP phosphohydrolase; Accounting; Address; Adult; Aerosols; Alleles; Animal Model; Attention; Binding; CD44 gene; CDH1 gene; Cause of Death; Cell Culture Techniques; Cell Cycle Regulation; Cell Line; Chromatin; Chromatin Remodeling Factor; Chromatin Structure; Chromosomal translocation; Complex; DNA; DNA Methylation; DNA Modification Methylases; DNA Sequence; Development; Disease; Drug Design; Engineering; Epigenetic Process; Etiology; Exposure to; Formaldehyde; Frequencies; Gene Expression; Gene Expression Regulation; Gene Silencing; Genes; Genetic Transcription; Genetically Engineered Mouse; Histology; Histone Acetylation; Histone Deacetylase Inhibitor; Histones; Homologous Gene; Human; Human Development; Immunohistochemistry; Lung Neoplasms; Malignant Epithelial Cell; Malignant Neoplasms; Mating Types; Methylation; Modeling; Modification; Mus; Mutate; Mutation; Neoplasm Metastasis; Non-Small-Cell Lung Carcinoma; Nucleosomes; Outcome; Patients; Pattern; Play; Positioning Attribute; Prevention; Process; Promoter Regions; Proteins; Publishing; RNA Interference; Reagent; Regulatory Element; Reporting; Research; Role; SMARCA1 gene; SMARCA4 gene; Screening procedure; Solid Neoplasm; Sucrose; Technology; Testing; Tumor Suppressor Proteins; Woman; Yeasts; base; cell growth regulation; chromatin remodeling; gene discovery; histone modification; human disease; imprint; improved; insight; leukemia; loss of function; men; mouse model; novel; novel strategies; outcome forecast; promoter; protein complex; translational study; tumor; tumorigenesis

Epigenetic changes in gene expression play an important role in the development and progression of human non-small cell lung carcinoma (NSCLC). Recent studies have shown that patients with tumors possessing one or more epigenetically silenced genes often show a poorer overall survival. Most reports have focused upon two major mechanisms to account for epigenetic modifications, DNA methylation and alterations in histone modifications. However, altered nucleosome positioning at gene promoters represent another important mechanism by which genes can be epigenetically regulated. Indeed, several studies have now implicated chromatin-remodeling complexes in the genesis of epigenetic silencing in human tumor development. In particular, the SWI/SNF (mating type switch/sucrose nonfermenting) chromatin remodeling complex appears like a strong candidate for contributing to epigenetic alterations in NSCLC. Originally identified in yeast, the SWI/SNF complex alters chromatin structure by remodeling nucleosomes through an ATP-dependent process. Loss or expression of the SWI2 ATPase homologs, BRG1 and BRM, by promoter methylation and/or mutations of either or both genes occurs in ~25% of human NSCLC cell lines and ~10% of primary human NSCLCs. Importantly, several groups including our own have shown a correlation between loss of expression of BRG1/BRM and poor prognosis in NSCLC patients. Our published reports and preliminary results demonstrate that reexpression of BRG1 or BRM in deficient NSCLC cells induces expression of many epigenetically silenced genes. Therefore, we hypothesize that loss of SWI/SNF complex activity represents a novel mechanism for gene silencing during NSCLC development. To test this hypothesis, we propose a synergistic research plan using cell culture and genetically engineered mouse models. Specifically, we will determine which gene promoters are activated by BRG1 and/or BRM after reexpression in deficient NSCLC cell lines, discover gene promoters that undergo silencing after loss of BRG1 expression in NSCLC cell lines and assess the effects of BRG1 and/or BRM loss on tumor development in a genetically engineered mouse model for NSCLC. The successful completion of the proposed studies will provide valuable insights into the mechanisms of epigenetic silencing during NSCLC development and of SWI/SNF chromatin remodeling as well as generate a novel genetically engineered animal model for further basic and translational studies. Furthermore, if DNMT or HDAC inhibitors are not effective in reversing gene silencing in the subset of NSCLCs that lack BRG1 and BRM expression, they may require a novel approach for treatment and prevention of progression. By identifying the unique chromatin changes that occur in these tumors and how they differ from BRG1 and/or BRM-positive tumors, we can initiate rational drug design studies to find the reagents to treat this deadly disease.

基因表达的表观遗传学改变在人类非小细胞肺癌（NSCLC）的发生和发展中起重要作用。最近的研究表明，具有一个或多个表观遗传沉默基因的肿瘤患者通常表现出较差的总体生存率。大多数报告都集中在两个主要的机制来解释表观遗传修饰，DNA甲基化和组蛋白修饰的改变。然而，改变核小体定位在基因启动子代表另一个重要的机制，基因可以表观遗传调控。事实上，现在有几项研究表明，染色质重塑复合物参与了人类肿瘤发展中表观遗传沉默的发生。特别是，SWI/SNF（交配型转换/蔗糖非发酵）染色质重塑复合物似乎是导致NSCLC表观遗传学改变的强有力候选者。SWI/SNF复合物最初在酵母中发现，通过ATP依赖性过程重塑核小体来改变染色质结构。 在约25%的人NSCLC细胞系和约10%的原代人NSCLC中，由于启动子甲基化和/或任一或两种基因突变导致SWI 2 ATP酶同源物BRG 1和BRM缺失或表达。重要的是，包括我们自己的研究小组在内的几个研究小组已经表明， BRG 1/BRM与NSCLC患者预后不良我们发表的报告和初步结果表明，BRG 1或BRM在缺陷型NSCLC细胞中的再表达诱导了许多表观遗传学沉默基因的表达。因此，我们假设SWI/SNF复合物活性的丧失代表了NSCLC发展过程中基因沉默的一种新机制。为了验证这一假设，我们提出了一个协同研究计划，使用细胞培养和基因工程小鼠模型。具体而言，我们将确定哪些基因启动子在缺陷型NSCLC细胞系中重新表达后被BRG 1和/或BRM激活，发现NSCLC细胞系中BRG 1表达缺失后发生沉默的基因启动子，并评估BRG 1和/或BRM缺失对NSCLC基因工程小鼠模型中肿瘤发展的影响。这些研究的成功完成将为NSCLC发展过程中的表观遗传沉默机制和SWI/SNF染色质重塑机制提供有价值的见解，并为进一步的基础和转化研究产生一种新的基因工程动物模型。此外，如果DNMT或HDAC抑制剂不能有效逆转缺乏BRG 1和BRM表达的NSCLC亚组中的基因沉默，则可能需要一种新的治疗和预防进展的方法。通过识别这些肿瘤中发生的独特染色质变化以及它们与BRG 1和/或BRM阳性肿瘤的差异，我们可以启动合理的药物设计研究，以找到治疗这种致命疾病的试剂。