E3泛素连接酶Hrd1通过降解IGF-1R抑制乳腺癌发生发展的分子机制研究

Understanding the process of breast cancer development has long been an essential research interest. In recent years, E3 ubiquitin ligases are regarded associated with the various diseases, including cancers. The preliminary data from the current research project demonstrated that expression of Hrd1 is significantly higher in the peri-cancerous tissues than in the cancerous tissues. The results from the in vitro study indicated that Hrd1 expression downregulates Insulin-like Growth Factor-1 Receptor (IGF-1R) expression by their direct interaction, affecting the epithelial mesenchymal transformation of normal breast cells and proliferation as well as migration of breast cancer cells. In this project, we will focus on the mechanism of IGF-1R degradation mediated by Hrd1 in both normal breast epithelial cells and breast cancer cells. Based on this, we intend to further clarify the effects of Hrd1 on the tumorigenesis, proliferation and metastasis of breast cancer. Meanwhile, the tumorigenetic effect of estrogen will be studied from its impact on Hrd1 expression in breast epithelial cell. The findings from our current study help us to develop antitumor drugs targeting E3 ubiquitin ligases.

E3泛素连接酶通过对细胞内重要蛋白质的降解参与机体的生理与病理甚至肿瘤的发生发展过程。而E3泛素连接酶Hrd1在乳腺癌中的作用与功能尚不清楚。本课题前期发现： Hrd1在乳腺癌组织中呈高表达；Hrd1的表达与正常乳腺上皮细胞发生EMT及抑制乳腺癌细胞增殖与迁移有关； Hrd1可与IGF-1R在乳腺癌细胞中直接结合。据此，我们推测Hrd1可能通过降解细胞内的IGF-1R而发挥抑制乳腺癌的作用。为验证此假说，本课题拟运用体内、体外模型，围绕Hrd1对乳腺癌发生发展的影响，重点阐明Hrd1介导IGF-1R的降解机制，进而探讨其对IGF-1R信号通路活性的影响，证明Hrd1抑制乳腺正常细胞的恶性转化及促进乳腺癌细胞的转移和侵袭，同时从Hrd1的角度对雌激素引起乳腺癌发生发展的机制进行深入的认识，本课题结果为针对E3泛素连接酶为靶点开发抗癌药具有重要的理论和实践意义。

泛素化是关键的蛋白质翻译后修饰，参与底物蛋白质的降解、定位或活化。HRD1是一种参与内质网相关降解的E3泛素连接酶，参与ERAD介导的IRE1α的泛素化降解，但目前研究发现它在不同肿瘤中发挥的功能不尽相同，可以器官特异性的参与ERAD进程外的一系列靶蛋白调控。代谢重编程已被公认为肿瘤的十大特征之一。肿瘤细胞代谢重编程的法则在于平衡细胞的能量需求和合成代谢，以满足肿瘤细胞快速持续增殖对能量、生物大分子合成和氧化还原力的需求。本研究利用生物信息学、分子生物学、肿瘤代谢及肿瘤生物学等研究方法揭示HRD1在乳腺癌发生发展过程中的具体作用靶点和分子机制，并得出以下重要结果：（1）HRD1通过泛素化IGF-1R参与乳腺癌的细胞增殖、侵袭转移及EMT过程；（2）HRD1通过泛素化CPT2促进三阴性乳腺癌脂肪酸β氧化及肿瘤发生。另外，还明确了HRD1 mRNA的调控机制：乳腺癌中P65可与HRD1启动子特异性结合并抑制Hrd1的表达，抑制NF-κB活性可逆转IL-6诱导的HRD1表达下调。总的来说，本项目通过发现并确认HRD1在乳腺癌中的两个重要靶蛋白IGF-1R及CPT2，揭示HRD1作为抑癌蛋白参与乳腺癌肿瘤发生、肿瘤代谢重编程等多个过程中的具体作用机制，为以IGF-1R及肿瘤代谢为靶点的乳腺癌靶向治疗提供新的可利用靶标。