NIT1负反馈调控HIF1α/Notch/Hes1轴抑制结直肠癌增殖的作用机制研究

结直肠癌晚期患者手术治愈希望渺茫，精准的基因靶向治疗或可为患者带来显著的生存获益。我们前期发现NIT1在结直肠癌中表达下调且通过与TGFβ-Smad2/3之间的正反馈环路抑制结直肠癌增殖。近期我们又发现NIT1表达下调可能激活HIF1α通路，促进缺氧糖酵解，并促使Notch/Hes1通路激活，协同促进结直肠癌增殖，而HIF1α及Hes1可能作为转录因子与NIT1启动子区结合并负调控NIT1的表达，故我们新提出“NIT1↓-HIF1α/Glut1↑-Notch/Hes1↑-NIT1↓”负反馈机制假说，此外，NIT1表达可能还受其启动子区CpG岛甲基化程度的影响。本项目拟采用双荧光素酶报告基因、ChIP、Western blot等方法旨在阐明上述反馈调控机制，并从转录水平和表观遗传学角度阐明及完善NIT1在结直肠癌中的表达调控机制，为抗癌靶向治疗提供新的思路和靶点。

Patients with colorectal cancer in advanced stage have little chance to heal with operations. They may be benefited with significantly longer survival rates by targeting gene therapy. In our previous studies, we found that NIT1 suppresses CRC proliferation through a positive feedback loop between NIT1 and the activation of TGFβ–Smad2/3 signaling pathway. In recent preliminary experiments, we found that down-regulation of NIT1 might promote the proliferation of CRC by activating the HIF1α signaling pathway, making a contribution to the hypoxia-enhanced glycolysis and activating the Notch/Hes1 signaling pathway. Bioinformatics analysis suggested that predicted candidate transcription factors, HIF1α and Hes1 might control the transcription regulation of NIT1. Knock-down of HIF1α or Hes1 increased the expression of NIT1. Therefore, we put forward that “NIT1↓-HIF1α/Glut1↑-Notch/Hes1↑-NIT1↓” as a novel signaling pathway may regulate the proliferation of CRC. Furthermore, we found that the expression of NIT1 might be regulated by methylation of CpG Island. Dual luciferase reporter assay, chromatin immunoprecipitation assay, western blot assay will be carried out to validate the negative feedback loop between NIT1 and HIF1α or Notch/Hes1 pathway, and to investigate the regulatory mechanism of NIT1 expression in CRC at transcriptional and epigenetic levels. This study may provide a new promising strategy for CRC.