UBA2基因介导的SUMO修饰在肾癌细胞凋亡中的作用及分子机制研究

Renal cell carcinoma (RCC), with increasing incidence rate and mortality, was one of the ten most common malignant tumors in the world. The pathogenic mechanisms of it remain unclear. UBA2 was one of the two members in the activating enzyme complex for posttranslational SUMO modification system. In our early study, we detected the higher expression of UBA2 in RCC tissues and cell lines than in normal tissues and cell lines. But when UBA2 was knocked down in 786-O cells, cell proliferation was inhibited and cell cycle was arrested at G2/M phase. On contrary, cell apoptotic rate increased greatly in UBA2 knockdown group. And in accordance, the activity of Caspase3/7 was also promoted significantly by UBA2 knockdown. The expression of c-Myc and p53 was also increased in UBA2 knockdown group. Based on these data, we deduced that UBA2 inhibits cell apoptosis through SUMO modification regulating the expression of p53 and Myc. Therefore, we designed the following experiments.To analyze the association between UBA2 and RCC, we will determine the expression of UBA2 in RCC tissues and normal renal tissues, and searched relative information in TCGA databank. We will also verify the role of UBA2 in Caki-1 cells and observe the effects of UBA2 on nude mice model bearing xenograft RCC. The molecular mechanism of apoptosis of RCC cells will be elucidated through UBA2-mediated SUMO modification regulating p53 and Myc. This study will provide some useful information for the diagnosis and therapy of RCC.

肾癌是威胁人类身体健康的十大恶性肿瘤之一，其发病机制目前尚不完全清楚。UBA2基因是SUMO蛋白修饰系统的激活酶复合物主要成分之一。我们前期研究发现，UBA2基因在肾癌组织及细胞系中表达均显著增高。当敲减786-O细胞中UBA2基因后，该细胞增殖能力减弱、细胞周期阻滞于G2/M期、Caspase3/7活性增强、细胞凋亡率增高、p53和c-Myc基因表达增高。结合文献，我们推测：在肾癌中，UBA2基因通过SUMO修饰调节p53和Myc基因表达，调控肾癌细胞的凋亡。为此，我们拟在肾癌和远癌正常肾标本中检测UBA2表达，并结合TCGA数据库信息分析UBA2基因与肾癌的关系；通过体内、体外实验验证UBA2基因在肾癌细胞生长及凋亡中的作用；并从SUMO修饰介导p53和Myc基因调控肾癌细胞凋亡的角度入手，揭示UBA2基因调控肾癌细胞凋亡的分子机制。为肾癌的诊治提供新的线索和思路。

肾癌是威胁人类身体健康的十大恶性肿瘤之一，其发病机制目前尚不完全清楚，且现有RCC 药物治疗的效果仍不十分乐观。因此寻找新的肾癌靶点是目前治疗晚期肾癌和转移性肾癌的当务之急。UBA2是SUMO蛋白修饰系统的激活酶复合物主要成分之一。我们在本课题的研究中，我们发现，UBA2基因在肾癌组织及细胞系中表达均显著增高，并且UBA2蛋白表达水平与患者的年龄和性别无关，但与肿瘤大小、Fuhrman分级和肿瘤分期显着相关。在2种肾透明细胞癌Caki-1和786-O细胞中，当敲减UBA2基因后，该细胞增殖能力减弱、细胞周期阻滞于G2/M期、细胞凋亡率增高、细胞迁移和侵袭能力减弱，p53和c-Myc等基因表达增高。过表达UBA2基因后，情况正好相反。裸鼠异种移植瘤模型中，我们观察到敲低UBA2后，肿瘤增殖速度减慢，Caspase3/7活性增强；过表达UBA2后，肾癌细胞的增殖速度显著加快，Caspase3/7活性增强。同时，我们发现p53突变体或者C-Myc的过表达减轻了UBA2敲低对细胞增殖和凋亡的影响。提示UBA2可能是通过调节p53突变体或者C-Myc的类泛素化修饰从而产生对细胞增殖的调节作用。总之，本课题研究证明了，UBA2与肾透明细胞癌密切相关，且UBA2在癌组织中特异性表达。且UBA2促进肾透明细胞癌的增殖、侵袭和迁移能力，抑制细胞凋亡。UBA2的这些作用与p53突变体或者C-Myc的类泛素化修饰密切相关，这些数据证明了UBA2可能是一种具有临床潜力的治疗靶点。