SPT6通过上调hTERT表达促进结肠癌发生发展的分子作用机制和临床意义

The elevated hTERT activity is the hallmarker of colon tumorigenesis. It is of significance to discover and identify the tumor-specific factors which regulate hTERT expression in colon cancer. In our preliminary study, we pulled down and identified SPT6 as a new hTERT promoter-binding protein in colon cancer cells by magnetic biopanning technique and proteomics methods. We also showed that SPT6 was highly expressed in colon cancer cells and tissues, regulated hTERT transcription and colon cancer cell growth. However, so far it is still unclear about the molecular mechanisms by which SPT6 regulates hTERT expression and colon tumorigenesis and development as well as its clinical implications. In this study, we will knockdown or overexpress SPT6 in human lung cancer cell lines and animal models, and then study the effects of SPT6 on hTERT expression, telomerase activity, telomere length , the stemness of cancer stem cells and tumor cell growth, thereby revealing the mechanisms of action of the SPT6/hTERT signaling pathway in colon tumorigenesis. Moreover,we will use tissue array, combined with the clinical data, to analyze the expression levels and the correlation of SPT6 and hTERT in tumor tissues from cancer patients, and to evaluate their relationship with colon tumorigenesis, pathological staging, recurrence and prognosis, thereby identifying the clinical implications of SPT6/hTERT. The results from this study will provide theoretical and experimental basis for the identification of the SPT6/hTERT signaling as a new therapeutic target for colon cancer treatment.

端粒酶重要组分hTERT的异常活化是结肠癌发生发展的风向标，发现和确定肿瘤特异性的hTERT转录活化因子意义重大。前期研究中，我们利用磁生物淘洗和蛋白质组学方法，在结肠癌细胞中垂钓并确定了新型的hTERT启动子结合蛋白SPT6，发现其在结肠癌细胞和组织中高表达，调控hTERT转录并影响结肠癌细胞生长，但SPT6在结肠癌细胞中调控hTERT继而影响肿瘤发生发展的具体分子机制和临床意义，尚不清楚。本项目拟在结肠癌细胞和动物模型中敲低或过表达SPT6，研究其对hTERT表达、端粒酶活性、端粒长度、肿瘤干细胞干性以及肿瘤生长的调控，揭示SPT6/hTERT信号通路在结肠癌发生发展中的机制和功能；并利用组织芯片，结合临床资料，分析结肠癌患者组织中二者的表达水平及其相关性，评估其与结肠癌发生、分期、复发、预后的关系，确定其临床意义。本项目将为确立SPT6/hTERT作为结肠癌治疗新靶点提供理论依据。

人端粒酶逆转录酶（hTERT）在决定细胞命运，特别是在癌症，包括结直肠癌的发生和发展中，发挥着重要作用。尽管如此，在不同的癌症类型中，hTERT被表达调控的准确的分子机制仍不清楚。本研究中，我们基于对结肠癌细胞的下拉/质谱分析，确定SPT6可能是与hTERT启动子结合的转录因子。体外研究表明SPT6敲低表达下调了hTERT启动子活性和hTERT表达，抑制了结肠癌细胞的增殖、侵袭和干细胞样特性，促进了细胞的凋亡诱导，并增强了体外化疗药物的敏感性。SPT6表达的沉默也导致小鼠体内人结肠癌细胞的异种移植物的生长和转移的延迟。进一步的机制研究表明SPT6通过与SND1的相互作用来共同调控hTERT的表达。敲低SND1表达可抑制SPT6在hTERT启动子的结合，并在体内外抑制SPT6过表达导致的hTERT表达，细胞增殖和stemness维持的上调。在小鼠结直肠癌原位模型和人的结直肠癌原位肿瘤组织中，SPT6、SND1和hTERT同时高表达，且这三个因子中两两表达均呈现出显著正相关。总之，我们的研究表明，SPT6通过与SND1协同作用共同靶向hTERT继而促进结直肠癌的发展，同时也表明阻断SPT6-SND1-hTERT轴可能有利于提高结直肠癌的治疗效率。