miR-223在MEF2A调控下通过FBXO8和Akt/mTOR信号通路参与结直肠癌侵袭和转移的分子机制

Our previous study showed that miR-223 was a metastasis associated miRNA of colorectal carcinoma. miR-223 promoted cancer cell invasion in vitro. Based on the bioinformatic analyses and preliminary experiments, we proposed a novel regulatory mechanism of miR-223, that miR-223, transcriptionally regulated by MEF2A, promotes invasion and metastasis of colorectal carcinoma by targeting FBXO8 and Akt/mTOR signaling pathway. To validate this mechanism, miRNA transfection, interference, luciferase reporter system and experiments in vitro and in vivo are performed (1) To confirm that miR-223 is targeted by transcription factor MEF2A, and miR-223 regulates FBXO8 and Akt/mTOR signaling pathway; (2) To detect the effects of FBXO8 and Akt/mTOR pathway on the invasion and metastasis of colorectal carcinoma induced by miR-223; (3) To confirm that FBXO8 is a functional targeted gene of miR-223. Our study aims to reveal a novel regulatory mechanism of miR-223, to illustrate the molecular mechanism of miR-223 in the progression of colorectal carcinoma, and to provide the novel miRNA or gene target for clinical intervention of invasion and metastasis of colorectal carcinoma.

预实验中我们筛选出miR-223为一个结直肠癌转移候选miRNA，发现miR-223能促进结直肠癌细胞的体外侵袭能力；根据生物信息学分析及预实验结果，我们提出了一个新的miR-223调控机制：即miR-223在MEF2A转录调控下，通过靶基因FBXO8及Akt/mTOR信号通路促进结直肠癌侵袭和转移。本项目拟验证这一机制，利用miRNA转染、干扰、荧光素酶报告系统、体内外侵袭及转移实验等进行（1）确认MEF2A是miR-223的上游转录因子，miR-223调控靶基因FBXO8及Akt/mTOR信号通路；（2）检测FBXO8及Akt/mTOR通路在miR-223诱导结直肠癌侵袭和转移中的作用；（3）证实FBXO8是miR-223的功能靶基因。旨在揭示一个新的miR-223表达调控机制，阐明miR-223在结直肠癌演进中的作用机制，为临床抗结直肠癌侵袭、转移提供新的miRNA和基因靶点。

miR-223是我们前期利用 miRNA 芯片筛选出结直肠癌转移相关的 miRNAs。我们通过荧光素酶报告系统和ChIP实验证实MEF2A是miR-223上游转录因子；证实MEF2A可通过调控miR-223表达进而调控FBXO8及Akt/mTOR信号通路；通过荧光素酶报告系统证实FBXO8是miR-223的下游靶基因；证实miR-223可通过FBXO8调控mTOR/P70S6K信号通路；通过体内外功能试验实验证实miR-223可通过FBXO8调控结直肠癌的增殖、侵袭及转移；通过免疫组化证实结直肠癌组织FBXO8表达水平与病人的转移与预后存在相关性。本项目揭示了一个新的 miR-223 表达调控的机制，即 miR-223 在 MEF2A 的转录调控下，通过靶基因FBXO8 及Akt/mTOR信号通路促进结直肠癌侵袭和转移。这一新机制的提出不仅为全面理解肿瘤演进的分子机制提供理论基础，更为 miR-223 及 FBXO8 作为新的结直肠癌转移分子标志物提供科学依据，为结直肠癌侵袭、转移的临床干预提供新的miRNA或基因靶点。