PRMT2促进低氧介导的转录激活在胶质母细胞瘤中的作用及机制研究

The tumor microenvironment of glioblastoma multiforme (GBM) suffers from hypoxia, which is a contributor to worse disease outcome. In our previous study, we demonstrated that protein arginine methyltransferase 2 (PRMT2) highly expressed in GBM, and was responsible for H3R8 asymmetric methylation. Recently, we found that PRMT2 was up-regulated by HIF-1a upon hypoxic treatment, and its expression level was positively correlated with HIF-1a and HIF-1a target genes in GBM. Together, we hypothesize that HIF1 firstly activates the expression of PRMT2 which catalyzes the formation of H3R2me2a and then in turn acts as a transcriptional co-activator to activate HIF1 target genes in GBM. In this project, we plan to detect the expression level of PRMT2 and the modification status of H3R8me2a in different regions in GBM, then establish the correlation between PRMT2 and HIF1 pathway; find out the essential role of PRMT2 in HIF1 activation of genes involved in tumor angiogenesis, invasion, cell proliferation, and metabolic reprogramming; uncover the regulation of HIF-1a to PRMT2 expression, as well as the mechanism of PRMT2 promotion of HIF-1a activated GBM malignant transformation. These results will provide further evidence to develop PRMT2 small molecule inhibitors to cure GBM.

胶质母细胞瘤（GBM）内部的缺氧状态与不良预后相关。我们前期证实组蛋白精氨酸甲基化转移酶2（PRMT2）在GBM中高表达，催化与基因表达活化相关的组蛋白H3R8me2a；近期发现：低氧环境下GBM中PRMT2的表达被低氧诱导因子HIF-1a激活，其表达水平与HIF-1a及下游靶基因表达正相关。我们推论：低氧环境下HIF1发挥功能需要首先激活PRMT2，后者催化H3R8me2a，两者协同调控细胞低氧反应。本项目，我们将检测GBM中PRMT2的表达水平以及H3R8me2a修饰水平，建立其与HIF1及其信号通路之间的相关性；明确PRMT2在HIF1激活与肿瘤血管生成、侵袭、细胞增殖、代谢重编程等相关的靶基因表达中的作用；揭示低氧环境下HIF-1a对PRMT2表达的调控以及PRMT2协助HIF-1a激活低氧相关基因及肿瘤恶性演变的机制，为开发PRMT2特异性小分子抑制剂用于治疗GBM提供理论依据。

胶质母细胞瘤（GBM）是一种最常见的、恶性的脑部原发性肿瘤，预后极差，其特征之一是瘤体内普遍存在着缺氧区域。缺/低氧诱导因子(HIF)是低氧反应中的最重要的调控因子，然而目前我们对GBM中HIF转录功能的调控机制还只是略知皮毛。在本项研究中，我们发现低氧条件下蛋白质精氨酸甲基转移酶2（PRMT2）能够被HIF-1a诱导表达，并催化HIF-1a靶基因上H3R8非对称性甲基化（H3R8me2a）的发生。进一步的研究证明，PRMT2催化的H3R8me2a能提高靶基因上H3K9乙酰化（H3K9ac）的修饰水平。H3K9ac是基因转录活跃的标志，能够通过控制RNA聚合酶II的暂停释放来参与转录延伸的发生。我们的结果证实，PRMT2通过催化H3R8me2a促进了HIF-1a靶基因的表达。在GBM细胞系中敲低PRMT2的表达或抑制其甲基转移酶的活性能够显著降低HIF-1a靶基因的表达水平，抑制细胞的侵袭能力，并削弱细胞的体外成球能力。我们还发现，抑制PRMT2的甲基转移酶活性能够抑制小鼠GBM肿瘤模型的发生发展，并进一步加强替莫唑胺的治疗效果。总之，我们的研究揭示了低氧条件下，PRMT2通过调控HIF-1a靶基因的表达水平促进GBM的进程，而抑制PRMT2的甲基转移酶活性提高了GBM对替莫唑胺的敏感性。