Pathogenesis and Treatment of NUT-Midline Carcinoma

项目摘要摘要。坚果中线癌(NMC)，中位生存期6.7个月，是 已知的最具侵袭性的实体肿瘤。它是鳞状细胞癌的一种亚型，其特征是 NUT(又名NUTM1)基因易位，最常见的是形成与双溴结构域的融合 编码蛋白(BET)，BRD4。迫切需要确定更具体的治疗方法 NMC的目标。这一拟议项目的超常目标是更好地了解 BRD4-NUT的肿瘤发生和确定有效的治疗靶点来治疗这种疾病。 BRD4-NUT主要通过以下途径抑制NMC细胞的分化和维持其增殖 激活MYC的表达。这一功能在使用BET抑制剂治疗时被破坏，作为乙酰- 赖氨酸模拟阻止BRD4溴结构域与乙酰化染色质的结合。BRD4-NUT驱动 促进生长的靶基因的表达，包括MYC，通过形成百万碱基大小的 过度乙酰化的“巨人”。BRD4-NUT超大抗原来源于已有的活性增强剂和 扩展以填充特定单元格类型的拓扑关联域(TADS)。TADS是高阶基因组 其功能是协调细胞命运的结构，通过DNA-DNA决定转录程序 联系人。我们小组最近发现的BRD4-NUT招募的独特蛋白质包括组蛋白乙酰基- 转移酶(HAT)、p300和几种ZNF蛋白统称为Z4。这些发现表明BRD4- 坚果‘劫持’细胞型特异性TADS以驱动促生长、抗分化基因的转录，如 假设在以下模型中：首先，BRD4-NUT复合蛋白质种子区域对应于细胞类型- 通过BRD4的染色质结合而产生特定的活性TADS。其次，大城市是由毗连的 依赖于p300 HAT的BRD4-NUT复合体在染色质上的前馈扩展 活动。第三，巨噬细胞的大小受到TAD边界和Z4复合体招募的HDAC活动的限制。 第四，高乙酰化的染色质、染色质重构体的招募和顺式转录因子的上调。 改变染色质构型以增强DNA-DNA相互作用，以驱动关键的前体转录 生长，反分化基因。本提案的目标是测试此假设模型，如 具体目标如下。 目的1.确定BRD4-NUT超大核糖体的形成。 目的2.确定BRD4-NUT大核糖体的功能。 冲击力。AIMS的成功完成有望识别出与BRD4-NUT相关的关键蛋白质 病理巨腺瘤的形成，并将确定新的和可能更有效的治疗靶点 NMC和其他癌症。此外，我们预测BRD4-NUT巨型机场将提供一个具有远距离- 达到影响染色质构象在肿瘤发生发展中的构效关系。

Project Summary Abstract. NUT midline carcinoma (NMC), with a median survival of 6.7 months, is one of the most aggressive solid tumors known. It is a subtype of squamous cell carcinoma characterized by translocation of the NUT (aka NUTM1) gene, most commonly forming a fusion to the double-bromodomain encoding protein (BET), BRD4. There is an urgent need for the identification of more specific therapeutic targets in NMC. The over-reaching goal of this proposed project is to greater understand the mechanism of BRD4-NUT oncogenesis and identify effective therapeutic targets for treating this disease. BRD4-NUT functions to block differentiation and maintain proliferation of NMC cells, largely through activation of MYC expression. This function is disrupted upon treatment with BET inhibitors, which as acetyl- lysine mimetics prevent binding of BRD4 bromodomains to acetylated chromatin. BRD4-NUT drives the expression of pro-growth target genes, including MYC, through the formation of megabase-sized massive hyperacetylated 'megadomains'. BRD4-NUT megadomains arise from pre-existing active enhancers and spread to fill cell-type-specific topologically associating domains (TADs). TADs are higher order genomic structures whose function is to orchestrate cell-fate determining transcriptional programs through DNA-DNA contacts. Unique proteins recruited by BRD4-NUT recently identified by our group include the histone acetyl- transferase (HAT), p300, and several ZNF proteins collectively termed Z4. These findings indicate that BRD4- NUT ‘hijacks’ cell-type specific TADs to drive transcription of pro-growth, anti-differentiative genes as postulated in the following model: First, BRD4-NUT complex proteins seed regions corresponding to cell-type- specific active TADs through the chromatin-binding of BRD4. Second, megadomains form from contiguous expansion of BRD4-NUT complexes across chromatin in a feed-forward manner dependent upon p300 HAT activity. Third, megadomain size is limited by TAD boundaries and HDAC activity recruited by the Z4 complex. Fourth, hyperacetylated chromatin, recruitment of chromatin remodelers, and upregulation of cis lncRNAs changes the chromatin configuration to enhance DNA-DNA interactions to drive transcription of key pro- growth, anti-differentiative genes. The goals of this proposal are to test this hypothetical model, as listed in the specific aims below. Aim 1. To determine how BRD4-NUT megadomains form. Aim 2. To determine how BRD4-NUT megadomains function. Impact. Successful completion of the aims is expected to identify key BRD4-NUT-associated proteins in pathologic megadomain formation, and will identify novel and possibly more effective therapeutic targets in NMC and other cancers. In addition, we predict that BRD4-NUT megadomains will provide a model with far- reaching impact on the structure-function relationship of chromatin conformation in cancer and development.