MACC1调控β-catenin信号通路参与结直肠癌发生和转移的分子机制

β-catenin signaling pathway plays important roles in tumorigenesis of many malignant tumours and the study on molecular mechanism of β-catenin signaling pathway is the hot spot of the current research. Metastasis-associated in colon cancer 1 (MACC1) is a newly identified key regulator gene, which is closely associated with infiltration and metastasis of colorectal carcinoma (CRC). However, the interaction between MACC1 and β-catenin signaling pathway in CRC has not been reported in the literature. Our preliminary data showed that the protein expression of MACC1 and β-catenin were upregulated in CRC cells and fresh CRC tissues by Western blot analysis. Moreover, MACC1 expression was significantly associated with histological grade, T classification and lymph node metastasis in CRC tissues by immunohistochemistry staining. Furthermore, there was significantly positive correlation between MACC1 high expression and β-catenin abnormal expression in CRC. It is more important that we observed MACC1 knockdown downregulated β-catenin expression in CRC cell line transfected with MACC1 siRNA compared with the control group by Western blot analysis. So we creat a hypothesis that MACC1 regulating β-catenin signaling pathway might be crucial in cacinogenesis and progression of CRC. Our current project includes the following content: 1) the expression characteristics of MACC1 in different stages of CRC; 2)the effect on β-catenin transcriptional activity and its downstream genes'expression by upregulating/downregulating MACC1 expression in CRC cell lines; 3) the pattern of MACC1 regulating β-catenin signaing pathway by Co-IP and ChIP methods to clarify the molecular mechanisms of MACC1 regulating Wnt/β-catenin signaling pathway in carcinogenesis and metastasis of CRC. Our object is to provide the new idea and valuable experiment evidence for illustrating the mechanism of carcinogenesis and progression of CRC and to find a novel target gene for CRC treatment.

恶性肿瘤发生发展中β-catenin信号通路的作用及机制是该领域的研究热点。MACC1是新近发现与结直肠癌侵袭转移密切相关的重要基因，其对β-catenin信号通路的调控尚未见报道。我们前期研究发现结直肠癌中MACC1和β-catenin蛋白呈高表达且二者存在明显正相关；同时，MACC1 siRNA可明显下调结直肠癌细胞中β-catenin蛋白表达。本课题拟利用临床结直肠癌组织标本对MACC1表达进行动态检测，探讨MACC1与结直肠癌发生和侵袭转移的关系；采用基因转染和RNA干扰技术，分别上调和下调结直肠癌细胞MACC1表达，检测其对β-catenin通路活性及下游基因表达的影响；进一步用免疫共沉淀、ChIP等技术研究MACC1调控β-catenin通路的作用模式，探明MACC1促进结直肠癌侵袭转移的分子机制，为阐明结直肠癌发生发展机制提供理论和实验依据，并为结直肠癌基因治疗寻找新的靶点。

本项目旨在研究metastasis-associated in colon cancer 1 (MACC1)在结直肠癌发生发展中的作用及与β-catenin信号通路关系。主要研究了1）MACC1和β-catenin在结直肠癌细胞和组织中表达及其与结直肠癌患者临床病理关系；2）体内外实验研究了MACC1对结肠癌细胞增殖、克隆形成、凋亡、迁移、侵袭和体内成瘤等生物学行为的影响；3）探讨了结直肠癌细胞中MACC1对β-catenin信号通路的影响。结果发现，1）MACC1和β-catenin在结直肠癌细胞和组织中表达高于正常结肠黏膜上皮细胞和相应的癌旁结直肠黏膜组织，MACC1表达与结直肠癌组织学分级、UICC分期，T分期和N分期密切相关。Cox回归分析显示高MACC1表达和β-catenin异常表达是结直肠癌患者总生存率减少的独立预后因子。结直肠癌中MACC1高表达和β-catenin异常表达存在明显正相关。2）下调MACC1表达可明显抑制结肠癌细胞SW620增殖、迁移、侵袭、克隆形成和体内移植瘤生长，并诱导细胞凋亡。而上调MACC1表达可明显促进结肠癌细胞HCT116增殖、迁移、侵袭、克隆形成和体内移植瘤生长，并抑制细胞凋亡。3）高表达MACC1可明显增加结肠癌细胞HCT116中Met, β-catenin,及通路相关基因包括c-Myc, cyclin D1、MMP9和 phos-GSK3β (Ser9) 表达，同时增加vimentin和抑制E-cadherin表达，而下调MACC1表达可明显抑制结肠癌细胞SW620中Met, β-catenin及通路相关基因包括c-Myc, cyclin D1、MMP9和 phos-GSK3β (Ser9) 表达，同时抑制vimentin和增加E-cadherin表达。结论，本研究发现MACC1可能通过β-catenin信号通路促进结直肠癌的发生发展。