Targeting BET-bromodomains in neuroblastoma

 描述（由申请人提供）：MYC转录因子在癌症中经常失调。染色质相关蛋白复合物将MYC与表观基因组中组蛋白赖氨酸乙酰化增加联系起来。因此，溴结构域和末端外结构域（BET）蛋白与这些乙酰化组蛋白赖氨酸结合并招募MYC蛋白，已成为癌症中引人注目的靶点，抑制剂已进入临床试验。神经母细胞瘤是儿童最常见的颅外实体瘤，高危疾病常表现为MYCN扩增。我们对不同的癌细胞系进行了对BET布罗莫结构域抑制剂（BETi）的敏感性的无偏筛选。我们验证了BRD4定向的shRNA和BETi对MYCN扩增的神经母细胞瘤细胞的活性，将这些体内研究扩展到患者来源的异种移植物（PDX）和MYCN驱动的神经母细胞瘤的基因工程小鼠（GEM）模型。重要的是，虽然BETi在体内显示出显著的疗效，但它们不是治愈性的，这表明需要联合治疗。我们假设BETi阻断MYCN与表观遗传机制的相互作用，并且结合BETi的联合疗法代表了增强疗效的稳健的、可转化的方法，并阻断MYCN驱动的NB中出现的耐药性。我们的提案确定了A）MYCN的阻断干扰转化的机制，B）肿瘤对BETi产生抗性的机制，和C）阻断新出现的抗性的可转化的组合疗法。成功完成指导有效的临床翻译BETi作为MYCN的途径特异性抑制剂。目的1：阐明EZH2在MYCN驱动的神经母细胞瘤中作为对BETi应答的介体的作用。目的2：在神经母细胞瘤的临床前试验中测试BETi与EZH2i以及与其他可转化的组合疗法。目的3：通过确定耐药的紧急机制，指导开发其他有效的联合治疗。

 DESCRIPTION (provided by applicant): MYC transcription factors are frequently dysregulated in cancer. Chromatin-associated protein complexes link MYC to increased histone lysine acetylation in the epigenome. Bromodomain and extraterminal domain (BET) proteins, which bind to these acetylated histone lysines and recruit MYC protein, have therefore emerged as compelling targets in cancer, with inhibitors entering clinical trials. Neuroblastoma is the most common extracranial solid tumor of childhood, with high-risk disease frequently showing Amplification of MYCN. We performed an unbiased screen of diverse cancer cell lines for sensitivity to BET bromodomain inhibitors (BETi). We validated the activity of both BRD4-directed shRNA and BETi against MYCN-amplified neuroblastoma cells, extending these studies in vivo both to patient derived xenografts (PDX) and to genetically engineered mouse (GEM) models of MYCN-driven neuroblastoma. Importantly, while BETi showed remarkable efficacy in vivo, they were not curative, suggesting the need for combination therapies. We hypothesize tat BETi block interactions of MYCN with the epigenetic machinery, and that combination therapies incorporating BETi represent a robust, translatable approach to enhance efficacy, and block emergent resistance in MYCN-driven NB. Our proposal identifies A) Mechanisms through which blockade of MYCN interferes with transformation, B) Mechanisms by which tumors develop resistance to BETi, and C) Translatable combination therapies to block emergent resistance. Successful completion guides effective clinical translation of BETi as pathway-specific inhibitors of MYCN. Aim 1: To clarify a role for EZH2 as a mediator of response to BETi, in MYCN-driven neuroblastoma. Aim 2: To test BETi with EZH2i, and with other translatable combination therapies in preclinical trials in neuroblastoma. Aim 3: To guide development of additional effective combination therapies, by identifying emergent mechanisms for resistance.