The epigenetic mechanisms of high-grade pediatric glioblastoma

小儿高级别胶质母细胞瘤的表观遗传机制

• 批准号: 9309372
• 负责人: Zhiguo Zhang
• 金额: $ 38.03万
• 依托单位: COLUMBIA UNIVERSITY HEALTH SCIENCES
• 依托单位国家: 美国
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-06-15 至 2022-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9309372
• 关键词: Acetylation; Affect; Alleles; Amino Acids; Ca(2+)-Calmodulin Dependent Protein Kinase; Cell Maintenance; Cell model; Cells; Child; Childhood Glioblastoma; Collaborations; Complex; Coupled; Development; Diagnosis; Diffuse intrinsic pontine glioma; Disease; Drug Targeting; Epigenetic Process; Foundations; Future; Gene Activation; Gene Expression; Gene Silencing; Genes; Histone H3; Human; Laboratories; Lysine; Malignant Neoplasms; Methionine; Methylation; Methyltransferase; Molecular; Mutation; Nucleosomes; Pathway interactions; Patients; Play; Primary Brain Neoplasms; Process; Proteins; Role; Signal Pathway; Signal Transduction; Somatic Mutation; Stat3 protein; Testing; Tumor Suppressor Genes; Variant; Vision; WNT Signaling Pathway; Xenograft Model; actionable mutation; base; cell killing; genome-wide; human embryonic stem cell; insight; molecular targeted therapies; mutant; novel; promoter; protein H(3); small hairpin RNA; stem cell differentiation; therapeutic target; tumor; tumor growth; tumorigenesis

Diffuse intrinsic pontine glioma (DIPG) is an aggressive primary brain tumor found exclusively in children. The median survival for DIPG patients is about one year from diagnosis, with no treatment in sight. Recent studies have uncovered driver mutations for DIPG, specifically, somatic mutations in the H3F3A gene have been observed in majority of DIPG cases. H3F3A encodes histone H3 variant H3.3 that plays an important role in regulating gene expression during development. The predominant mutation at H3F3A leads to amino acid change at lysine (K) 27 residue of H3.3 to methionine (M) (H3K27M). In human cells, there are two genes that encode H3.3, which is assembled into nucleosomes in a replication-independent nucleosome assembly pathway. In addition, there are 13 genes encoding canonical histones H3.1 and H3.2, which differ from H3.3 by 4 or five amino acids and are assembled into nucleosomes in a replication-coupled process. Lysine 27 is conserved among all these histone H3 proteins. Therefore, it is unknown how H3.3 K27M mutation, which occurs at one allele of H3F3A gene, promotes tumorigenesis. H3K27 is modified post-translationally by either acetylation or methylation. H3K27 methylation is catalyzed by the PRC2 lysine methyltransferase and plays an important role in gene silencing during stem cell differentiation and maintenance. We and others have shown that a global loss of H3K27 methylation occurs in DIPG cells containing K27M mutation, which is due to inhibition of PRC2 enzymatic activity by H3.3M27 mutant proteins. In addition to the global loss of H3K27me3 that is associated with gene activation, we also observed that H3K27me3 is present at the gene promoters of about 800 genes. These genes are largely silenced and are enriched in pathways associated with tumorigenesis. In addition, we performed an shRNA screen to identify genes that when depleted inhibit the proliferation of DIPG cells. We found that Wnt5a, a protein involved in non-canonical Wnt signaling pathway, inhibits proliferation of DIPG cells. Based on these exciting results, we hypothesize that H3.3M27 mutation proteins reprogram epigenetic states and gene expression of a key regulator(s)/pathway(s) and thereby promotes tumorigenesis. In this proposal, we will elucidate the molecular mechanism whereby the 800 genes with H3K27me3 and determine to what extent “gain” of H3K27me3 at these genes promotes tumorigenesis. In addition, we will elucidate the molecular mechanisms whereby Wnt5a and several components of Wnt5a signaling pathway are required for the proliferation of DIPG cells and test the hypothesis that inhibition of components of Wnt5a signaling pathway is a viable approach for the future treatment of DIPG. Together, the proposed studies will not only discover the molecular basis of tumorigenesis of DIPG, but also lay the foundation for molecularly targeted therapies for this deadly disease.

弥漫性内在庞然神经胶质瘤（DIPG）是一种仅在儿童中发现的侵袭性原发性脑肿瘤。 DIPG患者的中位生存期约为诊断，没有治疗。最近的研究 具有DIPG的驱动器突变，特别是H3F3A基因中的体细胞突变已是 在大多数DIPG病例中观察到。 H3F3A编码组蛋白H3变体H3.3在 调节发育过程中基因表达。 H3F3A的主要突变导致氨基酸 在赖氨酸（K）27 H3.3居住下的变化为方法（M）（H3K27M）。在人类细胞中，有两个基因 编码H3.3，该H3.3在非复制与核小体组装中组装成核小体 路径。此外，还有13个编码规范组蛋白H3.1和H3.2的基因，与H3.3不同 4或5个氨基酸，并在复制耦合过程中组装成核小体。赖氨酸27是 在所有这些组蛋白H3蛋白中保守。因此，尚不清楚H3.3 K27M突变如何 发生在H3F3A基因的一个等位基因上，促进肿瘤发生。 H3K27通过乙酰化或甲基化对后翻译进行了修饰。 H3K27甲基化被催化 PRC2赖氨酸甲基转移酶，在干细胞分化过程中的基因沉默中起重要作用 和维护。我们和其他人表明，在DIPG细胞中发生H3K27甲基化的全球损失 含有K27M突变，这是由于H3.3M27突变蛋白抑制PRC2酶活性。 除了与基因激活相关的H3K27me3的全局损失外，我们还观察到 H3K27me3存在于约800个基因的基因启动子上。这些基因在很大程度上是沉默的，并且 富含与肿瘤发生相关的途径。此外，我们进行了一个shRNA屏幕以识别 耗尽抑制DIPG细胞的增殖时，基因。我们发现Wnt5a是一种参与的蛋白质 非典型的Wnt信号通路，抑制DIPG细胞的增殖。基于这些令人兴奋的结果，我们 假设H3.3M27突变蛋白重编程表观遗传态和钥匙的基因表达 调节剂/途径（S），从而促进肿瘤发生。在此提案中，我们将阐明分子 具有H3K27me3的800个基因并确定H3K27me3的机制 这些基因促进了肿瘤发生。此外，我们将阐明Wnt5a的分子机制 Wnt5a信号通路的几个组件是DIPG细胞增殖并进行测试所需的 抑制Wnt5a信号传导途径的抑制是对未来的可行方法的假设 DIPG的处理。总之，拟议的研究不仅会发现肿瘤发生的分子基础 DIPG的含量，但也为这种致命疾病的分子靶向疗法奠定了基础。