Non-steroidal anti-inflammatory drug activated gene (NAG-1) expression is closely related to death receptor-4 and -5 induction, which may explain sulindac sulfide induced gastric cancer cell apoptosis.

Non-steroidal anti-inflammatory drugs (NSAIDs) are powerful chemopreventive agents in various cancers. They act by inhibiting cyclooxygenase (COX) activity, or through other mechanisms. NSAID-activated gene (NAG-1) has antitumorigenic and pro-apoptotic activities, but the mechanisms of NAG-1-induced apoptosis are poorly understood. Here we examined whether NAG-1 expression is induced in gastric cancer cells treated with NSAIDs, and the effect of NAG-1 expression on cell death. NAG-1 cDNA was transfected into SNU601 cells, and the relation between the ectopic expression of NAG-1 and death receptor-4 (DR-4) and DR-5 levels was studied. We found that NAG-1 expression was strongly induced in SNU601 cells, which lack endogenous COX-2, by sulindac sulfide, and that this was closely related with increased apoptosis and decreased cell viability. Moreover, temporal expressions of DR-4 and DR-5 induced by sulindac sulfide were similar to that of NAG-1. Most SNU601 cells transfected with NAG-1 cDNA did not survive during expansion. Forced NAG-1 expression significantly induced apoptosis and DR-4 and DR-5 expression. We conclude that NAG-1 expression is closely related to DR-4 and DR-5 induction, which could provide a mechanistic basis for the apoptotic effect of COX inhibitors in gastric cancer cells.