利用肠道特异性FBX8条件敲除小鼠探讨FBX8在结直肠癌侵袭和转移中的作用机制

前期工作中我们发现FBX8是转移促进因子miR-223的一个重要功能靶基因，FBX8在结直肠癌组织中表达下调，抑制结直肠癌细胞的增殖和侵袭能力。根据生物信息学分析及预实验结果，我们提出FBX8可能参与肿瘤转移调控的假设：即FBX8可能在SOX17转录调控下，通过泛素化降解mTOR抑制结直肠癌侵袭和转移。为证实这一假设，本研究拟利用细胞株、临床标本、裸鼠及转基因小鼠模型等技术；（1）明确FBX8在结直肠癌增殖、侵袭、各阶段转移（侵入血管、侵出血管及转移部位增殖）中的作用；（2）验证SOX17对FBX8的转录调控及FBX8对mTOR的泛素化降解并抑制下游靶基因；（3）检测mTOR泛素化降解对FBX8诱导结直肠癌侵袭和转移中的作用；（4）建立与结直肠癌演进规律相一致的肿瘤发生和（或）自发转移基因敲除小鼠模型并进行验证。为肿瘤转移机制研究提供新思路，为肿瘤转移的诊治提供新的靶点和理想的动物模型。

In our previous study, we found that FBX8 was a key functional target of metastasis promoting miR-223. FBX8 was down-regulated in colorectal cancer and suppressed cell proliferation and invasion of colorectal cancer. Based on the bioinformatic analyses and results of preliminary experiment, we proposed a novel regulatory mechanism of FBX8 in tumor metastasis: FBX8 is transcriptionally regulated by SOX17 and inhibits invasion and metastasis of colorectal cancer by targeting mTOR for ubiquitin degradation. This study will validate this mechanism by using cell lines,nude mouse, transgenic mouse and tissue sample (1) To reveal the role of FBX8 in proliferation, invasion and metastasis (including intravasation, extravasation and colonization at the metastatic sites) of colorectal cancer; (2) To verify that SOX17 transcriptionally regulates FBX8 and FBX8 targets mTOR for ubiquitin degradation and inhibits the expressions of downstream target genes; (3) To detect the effect of ubiquitin degradation of mTOR in FBX8-induced invasion and metastasis of colorectal cancer; (4) To establish the gene knockout model of tumorigenesis and spontaneous metastasis that is consistant with colorectal cancer progression and validate the novel mechanism of FBX8. Our study aims to give new clues for molecular mechanism of tumor metastasis, and provide novel target and animal model for clinical anti-metastasis.