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H. pylori CagA，Gt（ROSA）26Sor（CAG-LSL-cagA）（CAG-LSL-cagA）。利用该体内模型，我们证明了CagA的急性普遍表达可诱导小鼠胚胎死亡，这是由于Shp 2的异常激活。在成年小鼠中，CagA的急性普遍表达破坏了胃上皮，导致粘液颈细胞和壁细胞的损失，分别显著减少粘蛋白和酸分泌。在胃上皮中以CagA依赖性方式观察到DNA损伤（p-γ H2 AX），其通过引发干细胞群中DNA损伤诱导的p21积累来扰乱胃转换。CagA的胃特异性表达延长导致胃增生和腺癌的发展，其中p53表达在肿瘤区域中减弱。随后使用离体小鼠胃类器官模型的分析表明，虽然急性CagA表达抑制类器官的维持，但p53的敲低拯救胃类器官免于CagA诱导的生长抑制。使用体内和离体系统，作者证明，CagA诱导胃上皮（包括干细胞群）的DNA损伤，导致突变和关键肿瘤抑制因子（例如p53）突变的积累，这是CagA诱导的胃癌发生的重要早期步骤。总的来说，该研究利用了多种实验方法和设计，其导致CagA依赖性致癌作用的异常进展，这超过了该研究开始时的预期。

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.