FOXR2蛋白的SUMO化修饰对脑胶质瘤增殖的影响及机制研究

Malignant glioma is a serious threat to human health and life. However, the mechanisms of glioma oncogenesis still remain unclear. The transcription factor FOXR2, as a new oncogene, plays an important role in oncogenesis. Strikingly, unlike control cells, the Schwann cells over-expressing FOXR2 could form tumors in xenograft experiments. Our previous studies demonstrated that FOXR2 is over-expressed in glioma tissues and have important effects on the proliferation and growth of glioma cells. However, the regulation of FOXR2 activity, especially for its post-translational modification, is still poorly understood. Sumoylation could regulate the subcellular localization of target proteins and the transactivation of transcription factors, which plays important roles in tumorigenesis. We previously found that FOXR2 is modified by SUMO, suggesting that the FOXR2 sumoylation may have critical effects on the proliferation of glioma cells. In this study, we will further confirm FOXR2 is sumoylated and identify the potential sumoylation sites, elucidate the role of FOXR2 sumoylation on its protein stability, subcellular localization and transactivation in glioma, and clarify the effect of FOXR2 sumoylation on the proliferation and tumorigenesis of glioma by in vitro and in vivo experiments. Our expected results will provide valuable idea and potential targets for molecular therapy of glioma.

脑胶质瘤是严重威胁人类健康的疾病，其发生机制未完全阐明。转录因子FOXR2是在肿瘤发生中具有重要调控作用的新致癌基因。令人惊讶的是在正常血旺细胞系中过表达外源FOXR2，使该细胞产生了成瘤能力。我们前期证实FOXR2在脑胶质瘤中高表达，且调控其增殖和生长。但目前对FOXR2的活性调控，特别是其蛋白翻译后修饰调节机制所知甚少。SUMO化修饰可调控靶蛋白亚细胞定位、转录活性等功能，与肿瘤的发生密切相关。我们前期发现，FOXR2是SUMO化修饰的新靶蛋白，推断其SUMO化对胶质瘤增殖等方面具有重要影响。因此，本项目拟进一步明确SUMO化对FOXR2的调控及修饰位点；探明在脑胶质瘤中SUMO化修饰对FOXR2蛋白稳定性、亚细胞定位及转录活性的调控；体外和体内实验阐明FOXR2的SUMO化修饰对脑胶质瘤细胞增殖及成瘤性的影响。预期研究成果将为脑胶质瘤的分子靶向治疗提供新的有益思路及潜在靶点。

脑胶质瘤是严重威胁人类健康的疾病，其发生机制未完全阐明。转录因子FoxR2是在肿瘤发生中具有重要调控作用的新致癌基因，但目前对FoxR2的致癌活性，特别是其蛋白翻译后修饰调节机制所知甚少。本项目研究了FoxR2调控脑胶质瘤细胞增殖的作用与机制，分析了FoxR2的SUMO化修饰对FoxR2功能的调控。研究结果如下所示：1）与正常脑组织相比，在胶质瘤组织中FoxR2在mRNA水平与蛋白水平均高表达；2）敲除FoxR2后胶质瘤细胞周期进程显著阻滞于G1期，且FoxR2调控G1期重要调节蛋白如cyclin D1，p-Rb，p21与cyclin E的表达；3）FoxR2可通过调控MMP-2等蛋白的表达及活性影响胶质瘤细胞侵袭与迁移；4）体内实验结果表明，敲除FoxR2可抑制原位移植瘤的生长，延长荷瘤鼠的中位生存期；抑制体内细胞增殖相关抗原Ki67的表达，而促进了凋亡相关蛋白酶cleaved caspase-3的表达；5）FoxR2与SUMO1相互作用，结合位点为第258位赖氨酸，SUMO化连接酶PIAS1可促进FoxR2的SUMO化修饰；6）FoxR2的SUMO化修饰可增强FoxR2蛋白的稳定性与转录活性；7）FoxR2蛋白的SUMO化位点突变后可抑制胶质瘤细胞的增殖；8）小鼠模型中，FoxR2蛋白的SUMO化位点突变后可抑制胶质瘤成瘤能力。综上，FoxR2的SUMO化修饰可促进胶质瘤细胞增殖与肿瘤形成。该研究结果有助于加深对脑胶质瘤发病的认识，为胶质瘤治疗提供潜在的靶点。