关于胃Lgr5+细胞在上皮异型增生形成及进展的过程中参与积累遗传变异的作用及机制研究

It is known that dysplasia is the precancerous lesion for gastric cancer and associated with genetic variation. Because the turnover rate in gastric mucosa is too fast to accumulate and inherit genetic variation, some special paths for accumulation genetic variation might be present in the formation and progression of gastric dysplasia. Our previous studies have shown that chronic injury can promote gastric epithelium to gradually progress to severe dysplasia and increase the expression of Lgr5 (Leucine-rich repeat-containing G-protein coupled receptor). So we hypothesis that the Lgr5+ cells possessing the capacity to differentiate into various cells can accumulate and transfer the genetic variation induced by chronic injury to progeny in the formation and development of gastric dysplasia. We will conduct this research from in vitro, animal and human studies utilizing transgenic animals, lineage tracer, microdissection, DNA fingerprint analysis and so on. In this research, the differentiation capacity in Lgr5+ cells can be verified, The disorder of DNA damage and repair system in Lgr5+ cells can be detected, the Nei's genetic distance of Lgr5+ cells from DNA fingerprint analysis in the progression toward severe dysplasia can be analyzed. This research will confirm that the Lgr5+ cells can accumulate and transfer impaired genes to progeny in formation and progression of gastric dysplasia. This finding will be important for clarifying the mechanism of progression from chronic lesions to severe dysplasia and helpful for understanding the origin of gastric cancer. It will provide new paths for preventing or delaying gastric carcigenesis.

胃粘膜异型增生为癌前病变，也存在基因变异。然而胃粘膜上皮细胞更新快，难以积累并传承变异基因，那么异型增生的形成及进展过程中是否存在缓慢积累基因变异的特殊机制？我们前期研究发现持续的慢性损伤刺激可诱发胃粘膜上皮逐步向重度异型增生进展，同时伴Lgr5高表达，据此推测具有胃干细胞潜能的Lgr5+细胞有可能在慢性损伤诱发异型增生形成及进展的进程中参与积累并向子代传递遗传变异的作用。我们将从细胞、动物、临床的方向进行研究，通过转基因动物、谱系示踪、显微切割、DNA指纹谱分析、二代测序等技术验证Lgr5+细胞的分化修复功能，显示Lgr5+细胞内DNA损伤与DNA修复系统的状态，分析Nei氏遗传距离的变化趋势。本研究将有助于揭示Lgr5+细胞在异型增生形成及进展的进程中参与受损基因的积累并向子代传递，有助于阐明慢性病变缓慢进展至重度异型增生的机制，推进肿瘤起源的认识，为预防或延缓胃癌的发生提供新切入点。

胃癌是我国常见的恶性肿瘤之一，总体预后差。胃癌并非朝夕之间形成的，其实胃粘膜发生癌变之前将经历相对缓慢的癌前疾病期（萎缩肠化、轻度异型增生、重度异型增生等等）。虽然组织结构、细胞异型性改变不显著，但是隐匿性的改变是持续进行着，那么这些隐匿性的变化是如何发生？如何向子代延续并继发癌变的发生呢？本项目选取胃干细胞Lgr5+作为切入点，尝试探索胃粘膜上皮由异形增生向灶性癌变的进展过程中Lgr5细胞所发生了系列变化以及其参与的相关作用。本项目要采用MNNG成功诱导出大鼠胃癌，并建立稳定动物胃癌模型，进一步的分析发现Lgr5+细胞增殖活跃，并伴随DNA损伤与修复相关指标的异常失衡。该现象提示环境因素通过影响Lgr5+细胞内DNA损伤与修复的失衡而加速异型增生向灶性癌变的进程，有助于阐明慢性病变缓慢进展至灶性癌变的机制，推进肿瘤起源的认识，为预防或延缓胃癌的发生提供新切入点。