Pathogenesis and Treatment of NUT-Midline Carcinoma

项目摘要。NUT中线癌（NMC）的中位生存期为6.7个月，是 已知最具侵袭性的实体瘤它是鳞状细胞癌的一种亚型，其特征在于： NUT（又名NUTM 1）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），BRD 4.迫切需要确定更具体的治疗方法， 在NMC的目标。本拟议项目的目标是更好地了解 BRD 4-NUT肿瘤发生和确定治疗这种疾病的有效治疗靶点。 BRD 4-NUT主要通过以下途径阻断NMC细胞的分化并维持其增殖： MYC表达的激活。这种功能在用BET抑制剂处理时被破坏，BET抑制剂作为乙酰基- 赖氨酸模拟物阻止BRD 4溴结构域与乙酰化染色质的结合。BRD 4-NUT驱动 促生长靶基因的表达，包括MYC，通过形成巨大的 超乙酰化的“巨霉素”。BRD 4-NUT巨蛋白由预先存在的活性增强子产生， 扩散以填充细胞类型特异性拓扑关联域（TADs）。TADs是高阶基因组 其功能是通过DNA-DNA协调细胞命运决定转录程序的结构 联系人.我们小组最近发现的BRD 4-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，BRD 4- NUT“劫持”细胞类型特异性TADs以驱动促生长、抗分化基因的转录， 首先，BRD 4-NUT复合体蛋白种子区域对应于细胞类型， 通过BRD 4的染色质结合特异性活性TADs。第二，巨脉形成于相邻的 BRD 4-NUT复合物以依赖于p300 HAT的前馈方式跨染色质扩增 活动第三，巨肌群的大小受到Z4复合物募集的HDAC活性和肌层边界的限制。 第四，高乙酰化染色质，染色质重塑的募集，顺式lncRNA的上调 改变染色质构型以增强DNA-DNA相互作用，从而驱动关键前体的转录， 生长、抗分化基因。本提案的目标是测试此假设模型，如 具体目标在下面。 目标1。确定BRD 4-NUT巨肌群的形成方式。 目标2.确定BRD 4-NUT大电源如何工作。 冲击这些目标的成功完成预计将确定关键的BRD 4-NUT相关蛋白， 病理性巨肌群形成，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BRD 4-NUT巨肌群将提供一个远- 达到影响癌症和发展中染色质构象的结构-功能关系。

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.