Menin通过泛素-蛋白酶体通路促进肝癌的表观遗传学机制

Currently, it is poorly understood whether positive histone methyl-modification H3K4 contribute to the development of primary hepatocellular carcinoma (HCC). We found menin the product of Men1 gene induced H3K4me3 redistribution in HCC, heterozygous deletion of Men1 dramatically reduced the HCC incidence which induced by DEN, however, the key molecular network was not defined. In this project we will utilize the liver specific Men1 deletion mice to establish the HCC, identify the tumor promoter function of menin-MLL histone methyltransferase complex in HCC; Screen and identify the crucial molecular network and their functions regulated by menin through integrated analysis of ChIP-on-Chip and expression profile data; Reveal the function of menin in histone methyl-modification and epigenetic regulation to target gene in liver; Screen the small molecule inhibitors targeting the interaction between menin and MLL to exploit the prospect of these inhibitors in HCC therapy,such as IC-30. This study will reveal the novel epigenetic mechanism of positive histone methyl-modification regulated by menin in HCC.

目前尚不清楚H3K4等正性组蛋白甲基化修饰是否参与肝细胞肝癌（HCC）发生。我们发现，Men1基因编码产物menin促进肝细胞染色质H3K4me3重建，Men1杂合敲除显著降低DEN诱发的小鼠原发性HCC，但关键的分子网络尚未阐明。本项目拟利用肝脏特异性Men1敲除小鼠建立原发性肝癌等疾病模型，明确menin组蛋白甲基化酶复合物促进HCC发生发展的关键生物学功能；从已获得的ChIP-on-Chip、表达谱芯片等组学数据的整合性分析入手，筛选并鉴定肝脏中受menin调控的CUL4A泛素-蛋白酶体通路等关键分子网络及其临床意义；采用ChIP等关键技术鉴定menin在肝脏中的组蛋白甲基化调控特点及靶基因转录调控的表观遗传学规律；探讨IC-30等以menin-MLL为靶点的小分子化合物治疗HCC的潜在应用前景。将有助于深入揭示menin调控的正性组蛋白甲基化修饰促进HCC发生发展的表观遗传学机制。

肝癌是目前我国发病率和致死率位居第二位的恶性肿瘤，肝细胞癌（HCC）是肝癌的主要发病形式，至今仍缺乏对肝癌相关关键分子及其信号网络的深入认识。表观遗传学研究的广泛开展为深入揭示肝癌等肿瘤的发病机制提供了崭新的思路。研究显示，PcG 调控的H3K27 负性组蛋白甲基化修饰与HCC 发生有关。我们的前期工作证明menin-MLL 及其调控的H3K4正性组蛋白修饰可能是促进肝癌发生发展的重要分子事件，但其关键的调控网络有待于进一步鉴定，其精确的调控机制目前尚不清楚。为了进一步明确HCC发生过程中PcG家族调控的负性组蛋白修饰H3K27me3的生物学功能及其与menin-MLL调控的正性组蛋白修饰H3K4me3的关系。我们分别构建了PcG家族成员EZH2、SUZ12、BMI1和CBX8干扰的细胞系，结果显示PcG干扰后肝癌细胞系的体内、体外增值能力明显减弱；通过表达谱芯片筛选，我们鉴定了HCC中PcG下游的靶基因调控网络，筛选到已知的靶基因CDKN2A及新发现的靶基因E2F、NOTCH2和FOXO3等；利用ChIP-on-chip筛选并鉴定了正性组蛋白修饰H3K4me3和负性组蛋白修饰H3K27me3在HCC中潜在的协同促进作用；临床数据分析提示menin和EZH2共同高表达作为临床HCC不良预后评估分子标志的可行性；同时，我们的研究结果揭示了menin-MLL介导的H3K4组蛋白共价修饰及染色质重塑对HCC中印记基因IGF2新的转录激活机制，为肝癌的临床治疗提供了新的潜在靶标。