Evaluating the role of EZH2-interacting protein (EZHIP) in pediatric posterior fossa ependymoma metabolism

摘要 儿科室管膜瘤是中枢神经系统的第三大常见恶性肿瘤。当他们出现的时候 在神经轴的不同位置，这些肿瘤最常见于后颅窝区域。 大脑。后颅窝室管膜瘤被分成两组(A组和B组) DNA甲基化、转录和临床分析。在这两组中，A组(也称为PFA) 侵袭性更强，预后更差。这些肿瘤对化疗有抵抗力，并出现在 可能使其无法手术的敏感位置。Pfas是罕见的，因为超过80%的这些肿瘤 不会产生反复发生的基因突变。有趣的是，这些肿瘤的定义是转录上的全球缺失- 抑制性组蛋白修饰H3K27me3和转录激活组蛋白修饰的全局获得 H3K27ac。DNA甲基化和全球H3K27me3基因还原的变化表明PFA是表观遗传的 干劲十足。EZH2抑制蛋白(EZHIP)是一种在PFA中高表达并驱动全球 通过抑制组蛋白甲基转移酶EZH2的活性来还原H3K27me3。目前还不清楚是如何做到的 EZHIP表达和H3K27me3缺失促进了PFA室管膜瘤的致瘤性。引人注目的是，RNA测序 对多聚脂肪酸的分析表明，丙酮酸脱氢酶复合体上调，这是连接 糖酵解和三氯乙酸循环。随后的代谢和RNA分析表明，糖酵解和TCA循环 这些肿瘤的新陈代谢也得到了增强。根据这些初步数据，我假设EZHIP 表达通过表观激活丙酮酸脱氢酶上调PFA代谢 很复杂。为了验证这一假设，我将描述外源EZHIP的表观遗传和代谢效应 神经干细胞的表达和患者来源的PFA细胞系中EZHIP的缺失。要定义 PDC在肿瘤发病机制中的作用，我将通过RNA干扰和药物抑制靶向PDC的表达 并测定其在体内和体外对PFA生长的影响。这些实验将提供新的机制 对PFA生长的洞察，并将提供坚实的科学数据，可能为未来的治疗策略提供参考。

ABSTRACT Pediatric ependymomas are the third-most common malignancy of the central nervous system. While they arise in different places of the neuraxis, these tumors are most commonly seen in the posterior fossa region of the brain. Posterior fossa ependymomas have been stratified into two groups (Group A and Group B) based on DNA methylation, transcriptional, and clinical profiling. Of these two groups, Group A (also referred to as PFA) is more invasive and carries a worse prognosis. These tumors are resistant to chemotherapy and arise in sensitive locations that may render them inoperable. PFAs are unusual as more than 80% of these tumors do not bear recurrent genetic mutations. Interestingly, these tumors are defined by global loss of transcriptionally- repressive histone modification H3K27me3 and global gain of transcriptionally-activating histone modification H3K27ac. Alterations in DNA methylation and global H3K27me3 reduction indicate that PFAs are epigenetically driven. EZH2-inhibitory protein (EZHIP) is a novel protein that is expressed highly in PFAs and drives global reduction of H3K27me3 by inhibiting the activity of histone methyltransferase EZH2. It remains unknown how EZHIP expression and H3K27me3 loss drives tumorigenicity in PFA ependymomas. Strikingly, RNA-sequencing analysis of PFAs show upregulation of the pyruvate dehydrogenase complex, a key metabolic complex that links glycolysis and the TCA-cycle. Subsequent metabolomic and RNA analysis show that glycolytic and TCA-cycle metabolism are also enhanced in these tumors. Based on these preliminary data, I hypothesize that EZHIP expression upregulate PFA metabolism by epigenetically activating the pyruvate dehydrogenase complex. To test this hypothesis, I will characterize the epigenetic and metabolic effect of exogenous EZHIP expression in neuronal stem cells and EZHIP deletion in patient-derived PFA cell lines. To define the role of the PDC on tumor pathogenesis, I will target PDC expression via RNA-interference and pharmacological inhibition and determine the effect on PFA growth in vivo and in vitro. These experiments will provide novel mechanistic insights into PFA growth and will provide solid scientific data that may inform future therapeutic strategies.