MicroRNA‐222‐3p associated with Helicobacter pylori targets HIPK2 to promote cell proliferation, invasion, and inhibits apoptosis in gastric cancer

Gastric cancer ranks as the second leading cause of malignancy-related death worldwide, and always diagnosed at advanced stage. MicroRNA-222-3p (miR-222-3p) is aberrantly upregulated in various malignant tumors including gastric cancer, but its role and underlying molecular mechanisms in gastric cancer remain largely unknown. Helicobacter pylori (H. pylori) infection acts as a trigger in the development of gastric cancer, and increasing evidence suggests that H. pylori affects microRNA expression. In this study, gastric cancer tissue samples were divided into H. pylori positive group (+) and negative group (-). QRT-PCR showed that miR-222-3p was significantly upregulated in H. pylori (+) group compared with H. pylori (-) group, and luciferase reporter assays identified homeodomain-interacting protein kinase 2 (HIPK2) as a novel target of miR-222-3p in gastric cancer. Immunohistochemistry revealed that HIPK2 levels were decreased in H. pylori (+) group compared with H. pylori (-). After that, functional experiments indicated that miR-222-3p overexpression promoted the proliferation and invasion, while inhibiting apoptosis of SGC7901 gastric cancer cells, but miR-222-3p knockdown exhibited the opposite effects. Also, HIPK2 knockdown induced similar effects as miR-222-3p overexpression in SGC7901 cells. Nude mouse experiments further suggested that HIPK2 overexpression signally attenuated the enhancing effect of miR-222-3p overexpression on cell proliferation, indicating that the effect of miR-222-3p on gastric cancer progression depends on HIPK2, at least in part. Overall, our results demonstrated that miR-222-3p/HIPK2 signal pathway regulated gastric cancer cell proliferation, apoptosis, and invasion, provided a novel therapeutic target for the treatment of gastric cancer infected by H. pylori.