Cancer-based discovery of novel mechanisms of chromatin control

项目概要/摘要： 癌症基因组的系统测序揭示了编码癌症的基因中突变的高患病率。 染色质调节蛋白。在这些畸变中，编码SWI/SNF（BAF）亚基的基因突变 染色质重塑复合物是最常见的，在所有癌症中总共发生超过20%。 虽然大多数在癌症中以如此高的频率突变的基因已经被研究了几十年， 对SWI/SNF突变的显著作用的认识是最近才有的。SWI/SNF与 当编码SMARCB 1亚基的基因被发现在几乎所有的细胞中双等位基因失活时， 儿童早期高度侵袭性和致死性癌症的所有病例，称为恶性横纹肌样瘤（RT）。 值得注意的是，这些RT癌症是基因组稳定的和二倍体的，使它们成为高度有用的模型，其中 研究SWI/SNF中断的影响。我们的长期目标是阐明SWI/SNF的功能 复合物，以确定它们的损失如何导致肿瘤发生，并将这种理解转化为新的 非常有效的疗法。我们的研究小组确定SMARCB 1是一种真正有效的肿瘤抑制因子， 后来有了高影响力的发现，帮助定义了SWI/SNF突变导致 细胞增殖失调。迄今为止，我们的研究结果表明，SWI/SNF促进控制 转录是细胞命运特化的基础，这种控制的破坏是癌症的基础。 阵我们假设SMARCB 1的缺失在驱动癌症生长的同时，也创造了独特的 漏洞为了识别这种脆弱性，我们对21个RT细胞系进行了严格的筛选， 与其他800种癌细胞系进行比较。从这个屏幕上，我们确定并随后验证了两个新的 这些基因是RT细胞存活所需的特异性和有效的基因。使用多种方法和工具，我们 已经验证了这两个基因在RT细胞中是特别必需的。我们随后的初步数据显示， 基因在染色质调节中具有意想不到的新作用：既调节活性染色质， 促进组蛋白H3上赖氨酸残基的乙酰化，其促进靶基因的转录。我们现在 假设这些基因与SWI/SNF复合物协同作用，其功能阐明将 提供了新的见解染色质介导的转录调节，机制，突变， SWI/SNF亚基驱动癌症和SWI/SNF突变产生的脆弱性。此外，这两种基因 带来了治疗靶向的机会。在建议的工作中，我们将定义机械关系 这些基因和SWI/SNF之间的联系，并确定RT中特定脆弱性的潜在机制。 总之，这些努力有可能通过扩大对以下方面作用的了解而产生重大影响： 染色质调节剂在正常细胞和转化中的作用，并通过鉴定高度特异性的新治疗药物， 这些致命的儿童癌症的靶点。

Project Summary/Abstract: The systematic sequencing of cancer genomes has revealed a high prevalence of mutations in genes encoding chromatin regulatory proteins. Of these aberrations, mutations in genes encoding subunits of SWI/SNF (BAF) chromatin-remodeling complexes are the most frequent, collectively occurring in over 20% of all cancers. Whereas most genes that are mutated at such high frequencies in cancer have been studied for many decades, recognition of a prominent role for SWI/SNF mutations is much more recent. The first link between SWI/SNF and cancer came when the gene encoding the SMARCB1 subunit was found to be biallelically inactivated in nearly all cases of the highly aggressive and lethal cancer of early childhood termed malignant rhabdoid tumor (RT). Notably, these RT cancers are genomically stable and diploid, rendering them a highly useful model in which to study the effects of SWI/SNF disruption. Our long-term goals are to elucidate the function of SWI/SNF complexes, to determine how their loss leads to oncogenesis, and to translate this understanding into novel highly effective therapies. Our group established SMARCB1 to be a bona fide and potent tumor suppressor and later made high-impact discoveries that help define mechanisms by which SWI/SNF mutations lead to dysregulated cell proliferation. Our findings to date suggest a model whereby SWI/SNF-facilitated control of transcription underlies cellular fate specification, with disruption of this control being the basis for cancer formation. We hypothesized that loss of SMARCB1, while driving cancer growth, also creates unique vulnerabilities. To identify such vulnerabilities, we undertook a rigorous screen involving 21 RT cell lines compared to 800 other cancer cell lines. From this screen, we identified and subsequently validated two novel genes as being required specifically and potently for RT cell survival. Using multiple approaches and tools, we have validated both genes as specifically essential in RT cells. Our subsequent preliminary data reveal that both genes have unanticipated novel roles in chromatin regulation: both regulate active chromatin and specifically facilitate acetylation of lysine residues on histone H3 that facilitate transcription of target genes. We now hypothesize that these genes cooperate with SWI/SNF complexes, and that elucidation of their function will provide novel insights into chromatin-mediated regulation of transcription, mechanisms by which mutation of SWI/SNF subunits drive cancer, and vulnerabilities created by SWI/SNF mutations. Additionally, both genes bring the opportunity for therapeutic targeting. In the proposed work, we will define the mechanistic relationship between these genes and SWI/SNF and determine the mechanism underlying the specific vulnerabilities in RT. Taken together, these efforts have potential for substantial impact by broadening understanding of the roles of chromatin regulators in normal cells and in transformation and by identifying highly specific new therapeutic targets for these lethal childhood cancers.