分化抑制因子家族调控结直肠癌侵袭转移机制的研究

Inhibitor of differentiation (Id) families are overexpressed in several kinds of cancer including colorectal cancer. Ids have been shown to promote tumor growth, invasion and metastasis, and maintenance the embryonic stem cell self-renewal function. Liver metastasis is one of the difficult problems in the therapy of colorectal cancer, in which the mechanism is not yet clear. Although a small amount of researchs have shown that Id can promote the early hematogenous dissemination，and regulate the self-renewal of cancer stem cells, it needs the further verification about the role of Ids on the hepatic metastasis of colorectal carcinoma and the colorectal cancer stem cells characteristics. In this study, we will use gene transfection technique to increase or decrease Ids expression in intestinal epithelial cells and several kinds of colorectal cancer cell lines, and study the effects of Ids on invasion and metastasis of colorectal cancer by cytobiological and molecular biological experiments, as well as analyze the detail molecular mechanisms. Furhtermore we will establish an orthotopic colorectal cancer liver metastasis animal model by inoculating colorectal cancer cell into the cecum of the nude mice, and explore the mechanism of Ids in controllong the metastasis in vivo. All the data would provide new ideas for the therapy of liver metastases from colorectal cancer.

分化抑制因子（Inhibitors of differentiation, Id）作为新的肿瘤相关基因在一些癌症包括结直肠癌中高表达，并被证明具有促进肿瘤生长、侵袭和转移的作用，并维持胚胎干细胞自我更新的功能。肝转移是肠癌治疗中棘手的问题之一，其机理并不明确。虽有少量的研究表明Id分子具有促进早期血行播散和调节肿瘤干细胞的自我更新的作用，但其在肠癌肝转移以及维持肠癌干细胞相关特性作用需要进一步验证。本研究采用基因转染技术提高或减低肠上皮细胞和肠癌细胞Id分子表达，通过体外细胞学和分子生物学实验，研究Id对肠癌细胞侵袭能力的影响以及相关的分子机制。进一步建立盲肠原位移植肠癌肝转移的裸鼠模型，通过分析肠癌细胞在体内的侵袭转移规律，探索Id分子对于肠癌肝转移调控的机制，从而为肠癌肝转移的治疗提供新的思路。

结直肠癌肝转移是肠癌治疗中最棘手的问题之一，导致了患者的高致死率，但其机制尚不明确，可能与关键基因的异常表达有关。分化抑制因子（Inhibitors of differentiation, Id）在多种癌症包括结直肠癌中高表达，有文献表明Id分子具有促进早期血行播散的作用。本项目重点探讨Id分子在结直肠癌细胞侵袭转移中的调控作用及其分子机制。研究结果显示，Id家族四个成员在结直肠癌中的作用各不相同：Id1、Id2、Id3在结直肠癌中呈高表达，起促癌作用。Id1和Id3具有一定的协同效应，且调节肠癌细胞的“干性”；Id4则呈低表达，起抑癌作用。敲减Id1、Id2、Id3或过表达Id4后，肠癌细胞生长、迁移、侵袭和EMT也随之受抑制。动物实验证实敲减Id1或过表达Id4可抑制结直肠癌细胞的体内成瘤能力和肝转移潜能。机制研究表明，Id分子是通过PI3K/AKT通路或Wnt/β-catenin通路调控肠癌细胞增殖、转移、EMT以及“干性”特征。Id4可与角蛋白CK18相互作用，抑制侵袭转移。同时探索以Id1为靶点治疗肠癌的可行性，发现七羟基异黄酮（7-HIF）可通过Id1抑制肠癌细胞的增殖和干性；调控Id1上游基因ATF3基因也能抑制肠癌细胞的侵袭和转移。本项目成果明确了Id 分子与结直肠癌肝转移的相关性，并通过体内外试验揭示Id 分子对肠癌生长、转移、EMT和“干性”的影响。明确了与Id4相互作用的蛋白，初步阐明相关分子机制，并为以Id为靶点治疗肠癌提供初步的实验依据。