In vitro tests were performed on different gastric cancer cell lines like MKN-28 GC cells, NUGC-4 GC cells, and MKN-45 GC cells, and human gastric epithelial cell line (GES-1) and showed that (GPx2) knockdown inhibited GC proliferation, migration, and epithelial–mesenchymal transition (EMT) in both in vitro and in vivo tests. The gene discussed is GPX2; the disease is gastric cancer.