Evaluating ADGRB3 as a tumor suppressor epigenetically silenced in WNT medulloblastoma

项目摘要/摘要 迫切需要为髓母细胞瘤(MB)患者开发新的疗法，MB是最常见的 儿童恶性中枢神经系统肿瘤。目前的治疗方法包括手术、放射治疗、 和化疗，根据亚型的不同，5年生存率为40%-90%。然而，孩子们 在治疗后出现严重的发病率，包括神经、智力和身体残疾。 本项目的总体目的是研究ADGRB3受体在慢性粒细胞白血病易感性中的作用。 小脑转化，并在相关机制的基础上探索MB的新疗法。ADGRB3是一种 孤儿七号跨膜G蛋白偶联受体(GPCR)在大脑中特异表达，以及 属于粘附型亚家族。我们新的初步数据显示，ADGRB3的表达是 在WNT组的MBS患者中显著减少，启动子在表观遗传上沉默， 提示ADGRB3缺失可能促进WNT-MB的形成。我们提出证据证明 甲基化的CpG结合蛋白Mbd2和组蛋白甲基转移酶EZH2切换到沉默的染色质。 此外，我们发现ADGRB3的重新激活可以减少细胞增殖和肿瘤生长，从而支持一种 抑瘤作用。为了在生理环境中测试这一点，我们产生了ADGRB3基因敲除(KO)小鼠， 我们计划将其与在菱形嘴唇和神经前体中表达突变b-连环素的小鼠杂交 背侧脑干，它们是WNT-MB的来源细胞。根据这些结果，我们假设 ADGRB3是小脑中的一种肿瘤抑制因子，并通过表观遗传疗法恢复其表达 可能代表了一种治疗WNT-MB儿童的新方法。为了检验我们的假设，我们建议 目的如下：(1)确定和靶向ADGRB3基因沉默的表观遗传学机制(S)。 WNT-MB，(Ii)确定ADGRB3表达的恢复是否以及如何抑制MB细胞的生长， 致癌信号和致癌特性，以及(Iii)决定ADGRB3基因表达的缺失 在致癌背景下CTNNB1激活使小鼠易发生小脑转化和MB瘤 发展。这些研究很重要，因为它们增加了我们对发育神经生物学的了解。 在中枢神经系统，并可能导致开发新的治疗方法的患者 髓母细胞瘤。

Project Summary/Abstract There is an urgent need to develop novel therapies for patients with medulloblastoma (MB), the most common malignant central nervous system (CNS) tumor in children. Current treatments include surgery, radiotherapy, and chemotherapy and result in 5-year survival rates of 40-90% depending on subtype. However, children suffer important morbidity secondary to treatment, including neurological, intellectual and physical disabilities. The overall purpose of the present project is to investigate the role of the ADGRB3 receptor in susceptibility of cerebellar transformation, and explore new therapies for MB based on the related mechanisms. ADGRB3 is an orphan seven transmembrane G protein-coupled receptor (GPCR) specifically expressed in the brain, and belonging to the adhesion-type sub-family. Our new preliminary data show that ADGRB3 expression is significantly reduced in patients with MBs of the WNT group, and the promoter is epigenetically silenced, suggesting that ADGRB3 loss may facilitate WNT-MB formation. We present evidence for the involvement of methylated CpG binding protein MBD2 and histone methyltransferase EZH2 in switch to a silent chromatin. Moreover, we show that reactivation of ADGRB3 can reduce cell proliferation and tumor growth, supporting a tumor suppressive role. To test this in the physiological setting, we generated ADGRB3 knockout (KO) mice, which we plan to cross with mice expressing mutant b-catenin in neural progenitors of the rhombic lip and dorsal brainstem, which are the cells of origin of WNT-MB. Based on these results, we hypothesize that ADGRB3 is a tumor suppressor in the cerebellum and that restoration of its expression with epigenetic therapy may represent a novel therapeutic intervention for children with WNT-MB. To test our hypothesis, we propose the following aims: (i) identify and target the epigenetic mechanism(s) underlying ADGRB3 gene silencing in WNT-MB, (ii) determine whether and how restoration of ADGRB3 expression can inhibit MB cell growth, oncogenic signaling and tumorigenic properties, and (iii) determine whether loss of ADGRB3 gene expression in the background of oncogenic Ctnnb1 activation predisposes mice to cerebellar transformation and MB tumor development. These studies are important as they increase our knowledge about developmental neurobiology in the CNS, and may lead to the development of novel therapeutic approaches for patients with medulloblastoma.