PTGS2 and gastric cancer: The most frequently studied putative molecular biological prognostic factors in gastric cancer are human epidermal growth factor receptor 2 (HER2/neu), epidermal growth factor receptor (EGFR), vascular endothelial growth factor receptor (VEGFR), cyclooxygenase 2, hepatocyte growth factor receptor (HGFR/MET) and etc. Trastuzumab, a monoclonal antibody targeting HER2, has been successfully approved as the first molecularly targeted drug against patients with HER2 positive gastric cancer [5].