MAPK (ERK2) kinase - a key target for NSAIDs-induced inhibition of gastriccancer cell proliferation and growth

Limited clinical and experimental studies indicate that nonsteroidal anti-i nflammatory drugs (NSAIDs) may inhibit gastric cancer growth. However, the mechanisms involved are not completely understood and cannot be explained b y COX-2 inhibition alone. MAPK signaling pathway is essential for cell prol iferation, but the effect of NSAIDs on MAPK activity and phosphorylation in gastric cancer has never been studied. Since increased and unregulated cel l proliferation and reduced cell apoptosis are important features of cancer growth, we studied whether NS-398, a selective COX-2 inhibitor and/or indo methacin (IND), a non-selective NSAID: 1) inhibit gastric cancer cell proli feration, 2) whether this inhibition is mediated via MAPK (ERK2), and 3) wh ether NSAIDs enhance apoptosis in gastric cancer cells. Human gastric epith elial cells (MKN28) derived from gastric tubular adenocarcinoma were cultur ed and treated with either vehicle, IND (0.25-0.5mM) or NS-398 (50-100 muM) for 6, 16, 24 and 48h. Studies: 1) Cellular proliferation was determined b y H-3-thymidine uptake. 2) MAPK activity was measured by incorporation of r adiolabeled phosphate into myelin basic protein. 3) Apoptosis was evaluated using TUNEL assay. IND and NS-398 significantly inhibited the proliferatio n of MKN28 cells at 24h by 3.5-5 fold (p <0.002) and at 48h by 2.5-10 fold (p <0.02). Both NSAIDs also significantly inhibited ERK2 activity: IND > 53 % inhibition, NS-398, 100 muM > 72% inhibition; all p <0.05. Both IND and N S-398 significantly increased apoptotic index. In conclusion, IND and NS-39 8 significantly inhibit proliferation and growth of human gastric cancer ce ll line MKN28. This effect is mediated by NSAID-induced inhibition of MAPK (ERK2) kinase signaling pathway, essential for cell proliferation. NSAIDs a lso increase apoptosis in MKN28 cells. In addition to inhibiting cyclooxyge nase, NSAIDs inhibit phosphorylating enzymes-kinases essential for signalin g cell proliferation. (C) 2001 Elsevier Science Inc. All rights reserved.