HNF4α调控sFRP1/Wnt-CDX2互作环路在胆汁酸诱导胃黏膜肠化生中的作用机制研究

Intestinal metaplasia is the most important precancerous lesion of gastric cancer. It was demonstrated that sustained CDX2 activation plays an important role.However, it's still unclear how CDX2 was activated in IM cells. We previously demonstrated that bile acid could enhance CDX2 expression and activate sFRP1/Wnt pathway through regulating HNF4α expression. It was documented that Wnt and CDX2 positively regulates each other during intestinal development and may promote HNF4α in a positive feedback way. We therefore propose that, during IM process, HNF4α is activated firstly and furhter regulates sFRP1/Wnt-CDX2 circuit. Furhtermore, sFRP1/Wnt and CDX2 both in turn positively promote HNF4α expression and ultimately lead to sustained CDX2 activation and IM development. The present study aims to clarify the key role and molecular pathway of HNF4α in regulating sFRP1/Wnt-CDX2 network during IM in cellular model, clinical IM tissues, mice model and gastric specifical HNF4α transgenic mice through IHC, gene transfection, pathway blockage, ChIP, EMSA and luciferase reporter gene assay. This project aims to explore the function and mechanisms of HNF4α in gastric IM both in vivo and in vitro, which will provide novel target for treatment of gastric precancerous lesion.

胃黏膜肠上皮化生（IM）是胃癌重要的癌前病变，肠转录因子CDX2持续活化是IM发生的关键，但其上游机制不明。我们前期发现，胆汁酸可通过肝核因子4α（HNF4α）调控CDX2和sFRP1/Wnt通路。文献表明，Wnt-CDX2存在互作，且可能正反馈调控HNF4α表达。由此假设：在胆汁酸诱导IM的过程中，HNF4α被激活，进而直接调控sFRP1/Wnt-CDX2互作环路，而后者又正反馈促进HNF4α表达，从而维持CDX2持续表达和IM的存在。本项目拟借助体外细胞模型、IM组织标本、MNU诱导的IM小鼠模型和胃组织特异性HNF4α转基因小鼠，利用免疫组化、基因转染、通路阻断、ChIP、EMSA和报告基因等技术，在分子、细胞、器官组织和整体水平，深入阐明HNF4α调控sFRP1/Wnt-CDX2互作网络在IM发生和维持中的关键作用及活化机制，为胃癌癌前病变的防治提供新的思路和潜在治疗靶点。

胃黏膜肠化生是胃癌重要的癌前病变。大量研究显示，胆汁反流是胃癌及其癌前病变的独立危险因素。然而，胆汁酸促进肠化生的分子机制尚未完全阐明。基于前期工作和文献回顾，我们推测，HNF4α通过调控sFRP1/Wnt-CDX2 环路，从而参与胆汁酸诱导胃黏膜肠化生的发生。. 本课题研究发现，胆汁酸可在胃上皮细胞内诱导肝细胞核因子HNF4α的表达，过表达HNF4α能够促进多种肠型标志分子的表达，而胃黏膜上皮细胞特异性表达的HNF4α转基因小鼠出现了诱导性的胃黏膜肠化生。进一步研究表明，胆汁酸可通过TGR5-ERK通路和FXR-SNAI2-miR-1通路激活HNF4α，而HNF4α-HDAC6-FOXP3和HNF4α-sFRP1-TCF7L2互作环路进一步增强HNF4α的表达水平，后者通过直接靶向激活CDX2和KLF4，最终促进胃黏膜肠化生的发生发展。研究还发现，胆汁酸通过miR-21/SOX2/CDX2轴促进CDX2的活性，WNT通路的抑制分子DKK1基因甲基化参与胆汁酸诱导的胃粘膜肠化生，而白藜芦醇能够通过激活PI3K/AKT/p-FoxO4通路抑制胆汁酸诱导的胃黏膜肠化生。上述结果为阐明胆汁酸致病机理和丰富胃粘膜肠化生发病机制提供了良好的理论依据，并为干预肠化生预防胃癌的发生提供了一定的实验依据。. 课题组共发表SCI学术论文8篇。共培养博士生3名、硕士生5名，其中3名博士生和3名硕士生已毕业并获得相应学位。在项目执行期间，课题负责人入选空军级专家，并当选中华医学会内科学分会副主任委员。