NDRG4-NF-κB反馈环路在结直肠癌中对Notch信号受体间调控的作用和机制

Notch signal plays an important and complex role in cancer, which deserves further investigation. The applicant proved that Notch1 and Notch2 played opposite roles in large samples of colorectal cancer specimens. And there is reciprocal inhibition function between Notch1 and Notch2, with research paper published in Clinical Cancer Research and other journals. Based on our previous work, the applicant raised a new theory: balance loss of Notch receptors in colorectal cancer promotes carcinogenesis and progression. And this theory has been half proved by applicant in the research funded by NSFC youth program, which proved that Notch2 can inhibit Notch1 through NDRG2. At the same time, it is found that Notch1 may inhibit Notch2 through NDRG4-NF-κB feedback regulation circle and its downstream microRNA miR-630. And NDRG4 may play a switch role in the activation of NF-κB by Notch1. In order to prove this theory and clarify mechanism, we will investigate the relation between molecules and their association with clinical characteristics among large sample of clinical specimens; clarify the mechanism of NDRG4; prove this regulation pathway and clarify the precise molecular mechanism of this pathway; clarify the function of this pathway in vivo and in vitro. The anticipated results would add new knowledge on the regulation of Notch signal and with potential clinical utility.

Notch信号在肿瘤中发挥重要且复杂的作用，调控网络有待于深入研究。申请人在临床大样本中发现Notch1和Notch2在结直肠癌中不仅作用相反，而且存在交互抑制，相关论文已发表于Clinical Cancer Research等期刊。根据前期研究，申请人提出了Notch信号受体间调控失衡促进结直肠癌发生发展的新理论，并通过青年项目阐明了其中Notch2通过NDRG2抑制Notch1的机制。进一步研究提示Notch1可能通过新抑癌基因NDRG4与NF-κB形成反馈环路及其下游的miR-630抑制Notch2，NDRG4在其中发挥阻断Notch1激活NF-κB的开关作用。本研究将在大样本中分析通路分子间及其与临床的相关性；利用多种分子生物学方法证明这一通路的调控方式并阐明其分子机制；通过体内体外研究验证通路在结直肠癌发生发展中的作用。预期成果将增加对Notch信号的全新认识并具有临床应用潜力。

Notch信号在肿瘤中发挥重要且复杂的作用，调控网络有待于深入研究。项目负责人前期研究提示Notch1可能通过新抑癌基因NDRG4与NF-κB形成反馈环路及其下游的miR-630抑制Notch2，NDRG4在其中发挥阻断Notch1激活NF-κB的开关作用。本研究通过多种分子生物学方法研究证实了Notch1与Notch2之间存在相互抑制作用，在同一临床队列中研究发现，在正常结肠、炎症、不典型增生和肿瘤组织中，Notch1与Notch2的表达趋势相反；而且在结肠癌样本中Notch1与Notch2信号受体活性胞内段的表达呈负相关关系，在结肠癌细胞中验证研究证明了Notch1与Notch2之间存在相互调控作用。进一步研究发现Notch1 通过转录-非依赖方式活化NF-κB，NDRG4 在这一起始阶段通过与p65 相互作用，抑制NF-κB 复合物入核，发挥阻断其活化的 “开关”作用；而当NDRG4 表达下调时，Notch1 活化去抑制的NF-κB，活化NF-κB 入核后转录上调Myc，Myc 进一步转录下调NDRG4 表达，导致正反馈式的NF-κB 去抑制，由Notch1 进一步活化NF-κB，经筛选发现活化的NF-κB可诱导非编码RNA miR-630和LUNAR1，在细胞中验证了二者可抑制Notch2受体表达。而Notch2可能通过抑制N1ICD与的RBP-J的结合，从而抑制Notch1靶基因转录。进一步研究发现Notch2可通过NDRG4抑制N1ICD，机制可能为NDRG4与N1ICD的相互作用，抑制N1ICD与RBP-J结合。综上所述，申请人研究成果证实论Notch1 可通过NDRG4-NF-κB 正反馈环路及其诱导的非编码 径抑制Notch2，而Notch2可通过NDRG4抑制N1ICD与的RBP-J的结合。