人端粒酶逆转录酶（hTERT）抑制c-Myc泛素化的机制研究及其在胃癌侵袭转移中的作用

In our previous study, we found that hTERT could regulate the expression of c-Myc through transcription and post-translation levels and thus promotes the metastasis and invasion of gastric cancer. However, the mechanism remains unclear. Our pre-experiment shows that hTERT inhibits the ubiquitination of c-Myc and enhance its protein stability. Through bioinformatics predictions and experiments, we observed that hTERT interacts with the deubiquitinating enzyme USP44, and USP44 participates in mediating the regulation of c-Myc ubiquitination by hTERT. Therefore, we speculate that hTERT can inhibit the ubiquitination of c-Myc by recruiting USP44 to stabilize the expression of c-Myc protein and ultimately facilitate the invasion and metastasis of gastric cancer. This study is planning to investigate the molecular mechanism of the inhibition of hTERT to c-Myc ubiquitination and its role in invasion and metastasis of gastric cancer, by co-immunoprecipitation, immunofluorescence, GST pull-down and animal experiments, ect. which will provide a new theoretical basis and therapeutic target for hTERT-based tumor therapy and drug development.

文献及课题组前期表明hTERT可从转录及翻译后水平调控c-Myc的表达，从而促进胃癌的侵袭转移。然而，hTERT如何参与胃癌细胞c-Myc蛋白的翻译后修饰调控机制不清。我们前期预实验发现，hTERT可抑制c-Myc的泛素化而增强其蛋白稳定性，进一步通过生物信息学预测及实验发现，hTERT与去泛素化酶USP44存在相互作用，而USP44参与介导了hTERT对c-Myc的泛素化调控。为此，我们推测，hTERT可通过募集去泛素化酶USP44抑制c-Myc的泛素化，从而稳定c-Myc蛋白表达，最终促进胃癌的侵袭转移。本课题拟通过免疫共沉淀、免疫荧光、GST pull-down及动物实验等，阐明hTERT抑制c-Myc泛素化的分子机制及其在胃癌侵袭转移中的作用，为基于hTERT的肿瘤治疗和药物开发提供新的理论依据及治疗靶点。

文献及课题组前期表明hTERT可从转录及翻译后水平调控c-Myc的表达，从而促进胃癌的侵袭转移。然而，hTERT如何参与胃癌细胞c-Myc蛋白的翻译后修饰调控机制不清。我们前期预实验发现，hTERT可抑制c-Myc的泛素化而增强其蛋白稳定性，进一步通过生物信息学预测及实验发现，hTERT与去泛素化酶USP44存在相互作用，而USP44参与介导了hTERT对c-Myc的泛素化调控。为此，我们首先检测了胃癌标本中，USP44、hTERT及c-Myc三种蛋白的表达情况，结果证实，在胃癌标本中，三种蛋白均不同程度上调，跟患者的预后呈负相关，且三者在胃癌组织中存在共定位现象。进一步，我们在胃癌细胞中，过表达了USP44，其明显的促进了肿瘤的运动、迁移及侵袭转移能力，同时上调了c-Myc蛋白表达水平。同时，细胞免疫荧光及免疫共沉淀证实，hTERT与USP44在细胞核内存在共定位。因此，本课题证实hTERT可能通过募集USP44抑制c-Myc泛素化的分子机制及其在胃癌侵袭转移中的作用，为基于hTERT的肿瘤治疗和药物开发提供新的理论依据及治疗靶点。