hTERT非逆转录酶活性促胃癌转移的分子机制研究

文献及我们的研究表明,人端粒酶逆转录酶(hTERT)与肿瘤转移密切相关,但机制不清.文献报道,TERT非逆转录酶活性可通过与Brg1作用,活化Wnt信号,参与神经系统发育.我们前期预实验表明hTERT转染可以明显增加肿瘤细胞肝素酶表达,生物信息学预测到Wnt下游靶分子c-myc在肝素酶启动子上有结合位点,双荧光素酶实验提示c-myc可增强肝素酶启动子转录活性,提示hTERT可通过Brg1活化Wnt信号,促进c-myc表达,增强肝素酶转录,进而促进胃癌转移.基于以上假说,本课题拟采用分子生物学技术,首先证实c-myc可与肝素酶启动子结合,然后构建hTERT非逆转录酶表达载体,从体内、外二方面证明hTERT非逆转录酶活性在Wnt信号活化、c-myc表达、肝素酶转录以及胃癌转移中的作用及其机制.本课题将从另一个角度阐明hTERT在胃癌进程中的作用,为以hTERT为靶点的胃癌干预提供新的理论依据.

Literatures and our previous studies have showed that the human telomerase reverse transcriptase (hTERT) is related with tumor invasion and metastasis, but the mechanism is unclear. Scholars reported that TERT can be combined with Brg1 (brahma-related gene 1) and activate Wnt/β-catenin signal pathway and further participate in the development of nervous system independent of its reverse transcriptase. Our previous preliminary experiments demonstrated that hTERT transfection significantly increased heparanase expression in tumors. Bioinformatics predicted that there were binding sites of c-myc, a target molecular in the downstream of Wntβ-catenin signal pathway, in the promoter of heparanase. The dual luciferase experiments suggested that c-myc could enhance the promoter transcriptional activity of heparanase promoter. Based on the above analysis, we presume that hTERT could activate Wnt/β-catenin signal pathway through combining with Brg1 to promote the expression of c-myc, the latter would enhance the transcription of heparanase. This result will ultimately contribute to the invasion and metastasis of gastric cancer. Based on the above hypothesis, this study will first confirm that c-myc can be binded to the promoter of heparanase and increase the transcription of heparanase promoter. And then we will construct expression vector of hTERT independent of its reverse transcriptase and transfected with gastric cancer. We will further study the role and mechanism of hTERT in the activavtion of Wnt/β-catenin signal pathway, c-myc expression, heparanase transcription, and invasion and metastasis of gastric cancer by in vitro and in vivo experiments. This study will clarify the mechanism of hTERT in the advance of gastric cancer from another point of view. The results will provide a new theoretical basis for intervention to hTERT as a target for gastric cancer.