Apoptosis Induced by NS‐398, a Selective Cyclooxygenase‐2 Inhibitor, in Human Colorectal Cancer Cell Lines

Recent studies have suggested that apoptosis is a key phenomenon in the chemopreventive action of nonsteroidal antiinflammatory drugs (NSAIDs), which exhibit cancer‐preventive and tumor‐regressive effects in the human colon. The effect of NS‐398, N‐(2‐cyclohexyloxy‐4‐nitrophenyl)methanesul‐fonamide, which is a selective inhibitor of cyclooxygenase‐2 (COX‐2), on the induction of apoptosis in two human colorectal cancer cell lines (Colo320 and THRC) was determined. The apoptotic ratios (‐fold vs. control value) of Colo320 in the presence of 100 μM indomethacin and NS‐398 were 3.3 ± 1.5 and 9.0±0.94, and those of THRC were 2.3±0.46 and 7.4±0.87, respectively. The ability of NS‐398 to induce apoptosis is greater than that of indomethacin. Both indomethacin and NS‐398 reduced the cell proliferation in a concentration‐dependent manner. The IC50 values of NS‐398 (54.8+3.6 and 77.2±4.9μM) were significantly lower than those of indomethacin (206.3±43.0 and 180.3±22.6/μM) at P