Potential Association of EEF1A Dimethylation at Lysine 55 in the Basal Area of Helicobacter Pylori-Eradicated Gastric Mucosa with the Risk of Gastric Cancer: A Retrospective Observational Study

Background: Although eradication therapy for chronic Helicobacter pylori reduces the risk of gastric cancer (GC), its effectiveness is incomplete. Therefore, it is critically important to identify those patients who remain at high risk after H. pylori eradication therapy. Accumulation of protein methylation is strongly implicated in cancer, and a recent study showed that dimethylation of eEF1A lysine 55 (eEF1AK55me2) promotes carcinogenesis in vivo . We aimed to investigate the relationship between eEF1A dimethylation and H. pylori status in gastric mucosa and to reveal potential downstream molecules of eEF1A dimethylation in H. pylori -eradicated mucosa. Methods Records of 115 patients (11 H. pylori -negative, 29 H. pylori -positive, 75 post-eradication patients) who underwent upper gastrointestinal endoscopy were retrospectively reviewed. The eEF1A dimethyl level was evaluated in each functional cell type of gastric mucosa by immunofluorescent staining. We also investigated the relationship between eEF1AK55me2 downregulation by CRISPR/Cas9-mediated deletion of Mettl13, which is known as a dimethyltransferase of eEF1AK55me2. Results The level of eEF1A dimethylation significantly increased in the surface and basal areas of H. pylori -positive mucosa compared with -negative mucosa (surface, p =0.0031; basal, p <0.0001). The eEF1A dimethyl levels in the surface area were significantly reduced by eradication therapy ( p= 0.005), but those in the basal area were maintained even after eradication therapy. Multivariate analysis revealed that high dimethylation of eEF1A in the basal area of the mucosa was the independent factor related to GC incidence (odds ratio=3.6611, 95% confidence interval=1.0350–12.949, p =0.0441). We also showed the relationship between eEF1A dimethylation and expressions of reprogramming factors Oct4 and Nanog by immunohistochemistry and in vitro genome editing experiments. Conclusions The results indicated that H. pylori infection potently induced eEF1A dimethylation in gastric mucosa. The accumulation of dimethyl-eEF1A in the basal area of the mucosa might contribute to GC risk via regulation of reprograming factors in H. pylori -eradicated gastric mucosa.