转录因子BORIS转位线粒体调控结直肠癌发生发展的机制研究

The morbidity and mortality of colorectal cancer have ranked third and fourth places respectively in the world. The suppression of apoptosis in cancer cells is a main cause for tumorigenesis. BORIS, a transcription factor and expressed specifically high in cancer cells, accumulated in cytoplasm of cancer cells in clinical colorectal cancer tissue, suppressed apoptosis and promoted the progression of colorectal cancer, while the mechanisms remain unknown. Bcl2-associated athanogene BAT3 interacted with BORIS, expressed generally in normal cells, translocated from nucleus to mitochondria under the treatment of apoptosis inducers, regulated AIF dependent mitochondrial apoptosis pathway, might mediate BORIS to promote the progression of colorectal cancer. In previous study, the applicant has shown that apoptosis inducers promoted the translocation of BORIS from nucleus to mitochondria, AIF participated in the regulation of colorectal cancer cell proliferation by BORIS, BORIS mutant which lacked of nuclear localization signal promoted colorectal cancer cell proliferation. In this project, the applicant plans to investigate the translocation mechanism of the transcription factor BORIS to mitochondria. The success of the project would reveal the novel function of the transcription factor BORIS on apoptosis suppression in mitochondria and provide new perspective for finding new targets for diagnosis and therapy of colorectal cancer.

结直肠癌全球发病率和死亡率分别位于第三和第四位。癌细胞凋亡受抑制是癌症的重要起因。癌细胞特异高表达的转录因子BORIS在临床结直肠癌组织的细胞质内含量增高，抑制癌细胞凋亡促进结直肠癌发生发展，但机制不明。与BORIS相互作用的Bcl2相关抑凋亡因子BAT3，在正常细胞内广泛表达，凋亡诱导剂作用下由细胞核转位至线粒体，调控AIF依赖的线粒体凋亡通路，可能介导BORIS调控结直肠癌发生发展。申请人前期证明：凋亡诱导剂促使BORIS由细胞核转位至线粒体，AIF参与BORIS调控结直肠癌细胞增殖的过程，核定位信号缺失的BORIS促进结直肠癌细胞增殖。本项目拟研究转录因子BORIS向线粒体转位的机制。本项目的顺利开展将揭示转录因子BORIS在线粒体中抑制细胞凋亡的新功能，为寻找结直肠癌诊疗靶点提供新视角。

癌细胞特异高表达的转录因子BORIS在癌细胞的细胞质中高表达，抑制癌细胞凋亡，但机制不明。本项目利用免疫共沉淀和质谱测序，发现BORIS与凋亡诱导因子AIF相互作用。由于前期研究发现BORIS在核质均有定位，本项目中研究发现BORIS的sf6亚型蛋白专一定位于细胞质，通过核质分离以及线粒体分离的方法，本项目确证sf6亚型定位于线粒体，与BORIS的缺失锌指结构域的截短体相同均抑制MNNG诱导的细胞凋亡。由于BORIS的sf6亚型与BORIS的锌指结构域缺失截短体含有相同的N端氨基酸，表明BORIS的N端氨基酸对于BORIS的抑凋亡功能必需。此外本项目发现BORIS存在ADP-核糖化修饰，且抑制AIF的修饰和转位。因此ADP-核糖化修饰的BORIS可能是具有抑凋亡活性的BORIS。由于BORIS的N端1-258AA对BORIS的抑制癌细胞凋亡的功能必需。在确证BORIS的N的氨基酸为BORIS重要功能区的基础上，本项目筛选获得了靶向BORIS的多肽抑制物，该多肽结合BORIS的52AA-172AA，诱导癌细胞凋亡，抑制小鼠皮下肿瘤的发生发展。BORIS靶向肽的获得为今后进一步筛选靶向BORIS的药物奠定了基础。