人端粒酶逆转录酶(hTERT)诱导肿瘤细胞异质性的分子机制研究

The plasticity of tumor cell is involved in the construction of tumor heterogeneity, and tumor heterogeneity is the basis of invasion, metastasis and chemoresistance.The literature and our research showed human telomerase reverse transcriptase (hTERT) can promote the epithelial-mesenchymal transition(EMT) of tumor cells and stemness maintenance in cancer stem cells (CSCs), and closely related to the invasion, metastasis and chemoresistance of tumors. However, the mechanism of how hTERT inducing tumor heterogeneity is not clarified. It has been reported that hTERT can activate Wnt pathway through Brg1, promote the transcription of EMT and stemness maintenance associated factors in downstream. But Wnt signal pathway is not activated in all tumor cells，however, hTERT, EMT and stemness maintenance associated factors are still expressed. In additon, inhibition of Wnt pathway did not eliminate the role of hTERT in EMT and stemness maintenance. According to the literature and our preliminary experimental results, we suggest that hTERT as a cofactor which could be recruited by EMT and stemness maintenance associated nuclear transcription factors (ZEB1, Nanog or Sox2,et al), directly regulate EMT and stemness maintenance which are involved in the construction of tumor heterogeneity，and ultimately lead to tumor invasion, metastasis and chemoresistance. This project will provide a theoretical basis on the prevention and theropy of tumor heterogeneity induced by hTERT.

肿瘤细胞的可塑性参与了肿瘤细胞异质性的构筑，而肿瘤细胞异质性又是肿瘤侵袭转移和耐药的基础。文献及我们前期研究发现，人端粒酶逆转录酶(hTERT)可促进肿瘤细胞上皮间叶转化(EMT)和肿瘤干细胞(CSCs)干性维持,但其分子机制不明。文献报道hTERT可活化Wnt通路，促进其下游EMT和干性维持相关因子转录。但部分肿瘤中Wnt通路不活化,而其hTERT以及EMT和干性维持相关因子仍高表达；抑制Wnt通路不能消除hTERT在肿瘤细胞EMT及CSCs干性维持中的作用。结合文献及前期预实验结果,推测hTERT还可能作为一种辅助因子，被EMT或干性维持的关键核转录因子(ZEB1, Nanog 或 Sox2等)所募集，直接调控EMT和干性维持相关的关键核转录因子的表达,参与肿瘤细胞异质性构筑，最终在肿瘤侵袭转移及耐药中发挥重要作用。本课题的实施将为基于hTERT诱导的肿瘤细胞异质性的防治提供理论依据。

肿瘤细胞的可塑性参与了肿瘤细胞异质性的构筑，而肿瘤细胞异质性又是肿瘤侵袭转移和耐药的基础。文献及我们前期研究发现，人端粒酶逆转录酶(hTERT)可促进肿瘤细胞上皮间叶转化(EMT)和肿瘤干细胞(CSCs)干性维持,但其分子机制不明。我们一方面拟通过体内外侵袭转移实验阐明hTERT促进肿瘤侵袭转移分子机制，进一步采用双荧光素酶实验、ChIP及免疫共沉淀等实验揭示hTERT通过与ZEB1交互作用抑制E-cadherin转录表达，促进结肠癌的侵袭转移；另一方面通过克隆形成等实验阐明hTERT促进肿瘤细胞干性维持分子机制，进一步采用流式分选实验、免疫共沉淀实验及干细胞成球等实验揭示hTERT通过激活AKT/GSK-3β信号通路，GSK-3β不能磷酸化PRMT4 Ser487 ，促进PRMT4入核，促进下游干性关键转录因子Nanog、OCT4的转录表达，维持胃癌细胞的干性。因此，我们的研究揭示了hTERT通过进肿瘤细胞侵袭转移和肿瘤干细胞干性维持参与肿瘤细胞异质性的构筑中重要作用，靶向hTERT的肿瘤治疗可作为一潜在应用价值的新治疗手段。