Differential apoptosis by indomethacin in gastric epithelial cells throughthe constitutive expression of wild-type p53 and or up-regulation of c-myc

Nonsteroidal anti-inflammatory drug (NSAID)-induced apoptosis is considered to be an important mechanism in the antineoplastic effects and damage prod uced by the drugs in the gastrointestinal tract. In this study, two differe nt gastric cancer cell lines, MKN28 (mutant-type p53) and AGS (wild-type p5 3), were compared as to growth inhibition, apoptosis, and cell cycle and ap optosis-related gene expression in response to indomethacin treatment. Cell growth was measured by MTT (3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyl tet razolium bromide) assay. Apoptosis was characterized by acridine orange sta ining and DNA fragmentation, and cell cycle kinetics by flow cytometry. The mRNA and protein levels of p53, p21(waf1/cip1), and c-myc were determined by Northern and Western blotting. The results showed that indomethacin init iated growth inhibition and apoptosis in both cell lines without cell cycle shifting. AGS cells were more sensitive to growth inhibitory activity and apoptosis of indomethacin than MKN28 cells. In MKN28 cells, the levels of p 53, p21(waf1/cip1), and c-myc mRNA remained unchanged over the 24-hr treatm ent with indomethacin, but the p53 protein level was elevated alter li hr. There was no change in the p21(waf1/cip1) and c-myc protein levels in the M KN28 cells. In AGS cells, a progressive increase in c-myc mRNA and protein levels was noted, while p53 and p21(waf1/cip1) remained unchanged. It can b e concluded that wild-type p53 and/or up regulation of c-myc is associated with indomethacin-mediated differential apoptosis in gastric epithelial cel ls. BIOCHEM PHARMACOL 58;1:193-200, 1999. (C) 1999 Elsevier Science Inc.