Elucidating the mechanism of Hit-and-Run carcinogenesis by H. pylori CagA through a CagA-inducible mice model

本研究建立了一种新的幽门螺杆菌CagA诱导小鼠模型GT(ROSA)26Sor(CAG-LSL-cagA)(CAG-LSL-cagA)。利用这个体内模型，我们证明了CagA的急性无处不在的表达导致Shp2的异常激活而导致小鼠胚胎死亡。在成年小鼠中，CagA的急性无处不在的表达破坏了胃上皮细胞，导致粘液颈部细胞和壁细胞的丧失，分别显著减少了粘蛋白和酸性的分泌。在胃上皮细胞中观察到DNA损伤(p-γ，H_2AX)，这是一种依赖于CagA的方式，通过诱导DNA损伤诱导干细胞群中p21的积聚来扰乱胃的周转。CagA长时间的胃特异性表达导致胃增生和腺癌的发生，肿瘤区域的P53表达减弱。通过体外小鼠胃器官模型的后续分析表明，虽然CagA的急性表达抑制了器官的维持，但P53的敲除可以将胃器官从CagA诱导的生长抑制中解救出来。作者在体内和体外两个系统中都证明了CagA诱导胃上皮细胞包括干细胞群的DNA损伤，导致关键的抑癌基因如P53的突变和突变的积累，这是CagA诱导胃癌发生的关键早期步骤。总之，这项研究利用了各种实验程序和设计，导致了在依赖CagA的致癌方面取得了非凡的进展，这比本研究开始时预期的要多。

In the study, a new inducible mouse model of H. pylori CagA, Gt(ROSA)26Sor(CAG-LSL-cagA) (CAG-LSL-cagA), was established. Using this in vivo model, we demonstrated that acute ubiquitous expression of CagA induces embryonic lethality in mice due to aberrant activation of Shp2.In adult mice, acute ubiquitous expression of CagA disrupted the gastric epithelium, resulting in the loss of mucous neck cells and parietal cells, drastically reducing mucin and acid secretion, respectively. DNA damage (p-γH2AX) was observed in the gastric epithelium in a CagA-dependent manner which perturbed gastric turnover by eliciting DNA damage-induced p21 accumulation in stem cell populations. Prolonged gastric-specific expression of CagA resulted in the development of gastric hyperplasia and adenocarcinoma, where p53 expression was attenuated in the tumor regions.Subsequent analysis using ex vivo mice gastric organoid models demonstrated that while acute CagA expression inhibits organoid maintenance, knockdown of p53 rescues gastric organoids from CagA-induced growth inhibition.Using both in vivo and ex vivo systems, the author demonstrated that CagA induces DNA damage to the gastric epithelium, including the stem cell population, resulting in accumulation of mutations and mutations of key tumor suppressors such as p53, an essential early step in CagA-induced gastric carcinogenesis.Overall, this study utilized a variety of experimental procedures and design which resulted in exceptional progress in CagA-dependent carcinogenesis, which was more than expected at the start of this study.