人脑胶质瘤中IDH1基因突变及DNA甲基化调控与干细胞相关基因表达

【作者】 施金龙；

【导师】 朱剑虹； 赵曜；

【作者基本信息】 复旦大学 ， 神经外科学， 2010， 博士

【摘要】 脑胶质瘤是神经系统原发肿瘤中的最常见类型,随着现代医学发展及综合治疗技术的进步,脑胶质瘤的诊断与治疗有了很大提高,但其疗效预后并没有明显改善,因此,积极探索胶质瘤发生发展的分子机制并在肿瘤防治上寻找新的突破仍是当前医学研究的热点。异柠檬酸脱氢酶1(isocitrate dehydrogenase 1, IDH1)是三羧酸循环关键酶之一,其编码基因突变在胶质瘤中发生频率很高,具有胶质瘤特异性。IDH1基因突变可激活细胞缺氧诱导因子1α(hypoxia-inducible factor 1α, HIF-1α)信号通路,可能是脑胶质瘤发生发展的重要原因。本课题采用直接测序法检测了24例脑星形细胞胶质瘤患者原发及原位复发肿瘤样本中IDH1的突变分布,发现原发胶质瘤中IDH1基因突变发生率为54.2%,复发胶质瘤中突变分布与原发肿瘤一致。同时检测原复发肿瘤样本中干细胞相关基因OCT4、CD133 mRNA、蛋白及阳性细胞的表达水平,并根据IDH1突变分布和病理级别进行配对分析,结果显示：IDH1突变在原发胶质瘤中可促进干细胞相关基因表达上调；而复发胶质瘤中干细胞相关基因表达上调与IDH1突变似无明显相关。进一步对OCT4、CD133、IDH1的启动子甲基化水平进行BSP克隆测序检测,并分析目标基因甲基化水平与基因表达的相关性,结果提示：DNA低甲基化可上调OCT4、CD133基因表达,可能是复发胶质瘤中干细胞相关基因表达上调的主要原因之一,且部分参与了原发胶质瘤的发生过程；而IDH1启动子在原复发胶质瘤中均没有发生明显DNA甲基化。本课题初步证明了人脑胶质瘤中IDH1基因突变可促进干细胞相关基因的表达,可能是原发胶质瘤发生的重要机制之一,而DNA低甲基化可上调干细胞相关基因表达,在胶质瘤发生、复发过程中同样也发挥着重要的调控作用。这为进一步理解胶质瘤的发生机制与探索临床治疗新方向提供了部分实验基础。更多还原

【Abstract】 Glioma is the most common tumor of nervous system. With the development of modern medicine and treatment advances, diagnosis and treatment of glioma had been greatly improved, but its prognosis had not been improved significantly. So the molecular mechanism of the development of glioma and the new breakthroughs in medical research remained a current hot spot.Isocitrate dehydrogenase(IDH1) was one of the key enzymes in the citric acid cycle, and its’encoding gene mutations frequently in glioma. Further studies showed that IDHl mutations decreased its downstream products of a-ketoglutarate (a-KG), thus activated the HIF signaling pathway and promoted glioma formation.This issue analysised the relevance and the possible mechanism of IDHl mutation and stem cell-related genes expression of OCT4 and CD133 in 24 cases of primary and corresponding recurrent glioma tumor samples, in order to further understand the carcinogenic mechanism of IDHl mutation in gliomas and to provide new ideas and experiments for glioma stem cells research. The results showed that: IDH1 mutations have significant correlation with increased expression of OCT4 and CD133 in primary glioma; IDHl mutations have no significant correlation with increased expression of OCT4 and CD133 in glioma recurrence process. Then we detected IDH1, OCT4, CD133 promoter methylation by BSP cloning sequencing and analysised the relation of DNA methylation level and gene expression. The results showed:DNA methylation can regulate the gene expression of OCT4 and CD133 in primary gliomas; The promoter DNA methylation level of OCT4 and CD133 declined in recurrent glioma and it may be one of the main reasons of glioma recurrence; there was no obvious DNA methylation of IDH1 promoter region in gliomas.Taken together, our studies implicate that IDH1 mutations can promote stem cell-related gene expression in primary human glioma, and DNA methylation also play an important role in human glioma occurrence and recurrence. And our studies contribute to understand the pathogenesis of glioma and provided some experimental basis for new direction to explore the clinical treatment of glioma.更多还原