Role of Methyltransferases in MYC-driven Medulloblastoma

项目摘要/摘要 髓母细胞瘤(MB)是一种发生在儿童的后脑肿瘤，其发病率在各年龄段之间最高。 基于广泛的分子证据，髓母细胞瘤被分为四个主要类型，其中 MYC过表达的(G3)MB组预后较差。因此，需要新的治疗方法。 以有效地治疗这些儿童侵袭性脑瘤。最新的全基因组测序和850K 甲基化分析表明，G3MB有少量突变，其中大部分发生在表观遗传调控中 修饰组蛋白的酶。然而，很大一部分由MYC驱动的G3 MBS没有任何 突变表明额外的非突变的表观遗传调节因子，即所谓的“隐藏驱动因素”，可能起到 癌基因或肿瘤抑制基因，与形成染色质结构和驱动G3MB的形成有关。我们 进行了243个独特的小鼠表观遗传调控因子的缺失shRNA筛选，最受欢迎的是SMYD3，一种 H4K5me1甲基转移酶，重要调节MYC的表达。系统生物学揭示SMYD3 在G3 MB中过度表达最多，与其他G3 MB相比，MYC(类型II)特异性过度表达 亚型和MB组。为了解决SMYD3在推动G3 MB方面的作用，我们将使用多个互补 小鼠和人G3MB的体外和活体实验方法：1)评估SMYD3的过度表达 有助于G3MB肿瘤的发生，2)使用质谱学来鉴定相互作用的蛋白质并确定其作用 SMYD3在形成转录组、蛋白质组和磷酸蛋白质组中的作用，以及3)评估SMYD3和 其他表观遗传调节因子可被视为未来MYC驱动的临床试验的治疗靶点 G3MB。我们的最终目标是识别表观遗传脆弱性，这些脆弱性可以通过治疗靶向治疗 最具侵袭性的疾病形式。

Project Summary/Abstract Medulloblastoma (MB) is a tumor of the hindbrain that occurs in children with a peak incidence between the ages of 3 and 7. Based on extensive molecular evidence, medulloblastoma is classified into four major groups, among which Group (G3) MB with MYC overexpression, carry the worse prognosis. Thus, novel therapies are needed to effectively treat these aggressive brain tumors in children. Recent genome wide sequencing and 850K methylation profiling showed that G3MB has a paucity of mutations, most of which occur in epigenetic regulatory enzymes that modify histones. However, a significant proportion of MYC-driven G3 MBs do not harbor any mutations suggesting that additional non-mutated epigenetic regulators, so called “hidden drivers”, might act as oncogenes or tumor-suppressors, implicated in shaping the chromatin structure and driving G3 MB genesis. We performed a dropout shRNA screen of 243 unique mouse epigenetic regulators, and the top hit was SMYD3, a H4K5me1 methyltransferase that importantly regulates MYC expression. Systems biology reveals that SMYD3 is most overexpressed in G3 MBs that specifically overexpress MYC (type II) compared to the other G3 MB subtypes and MB Groups. To address the role of SMYD3 in driving G3 MB, we will use multiple complementary approaches in vitro and in vivo in both mouse and human G3MB to 1) assess how SMYD3 overexpression contributes to G3MB tumorigenesis, 2) use mass spectrometry to identify interacting proteins and define the role of SMYD3 in shaping the transcriptome, proteome and phosphoproteome, and 3) evaluate whether SMYD3 and other epigenetic regulators could be considered as therapeutic targets for future clinical trials in MYC-driven G3MB. Our ultimate goal is to identify epigenetic vulnerabilities that can be therapeutically targeted to treat the most aggressive forms of the disease.