In Shin’s study, nicotine stimulated β-adrenergic receptors and subsequently activated the downstream PKC/ERK1/2/activator protein-1 (AP-1)/cyclooxygenase-2 (COX-2)/prostaglandin E2 (PGE2) signaling cascade to promote gastric cancer cell growth and proliferation (Shin et al., 2007). This evidence concerns the gene PTGS2 and gastric cancer.