PTGS2 and esophageal cancer: Large-scale epidemiological studies have indicated that regular use of non-steroidal anti-inflammatory drugs, such as aspirin, which mainly acts by inhibiting COX-1 and COX-2, may reduce the risk of esophageal cancer [49], as selective COX-2 inhibition not only inhibits tumor invasiveness and metastasis in colon cancer cells [50] but also induces apoptosis in multidrug-resistant cell lines [51].