Role of caspase-3 in apoptosis of colon cancer cells induced by nonsteroidal anti-inflammatory drugs

Epidemiological studies have demonstrated that nonsteroidal anti-inflammato ry drugs (NSAIDs) decrease the incidence of and mortality from colon cancer . In addition, NSAIDs reduce the number and the size of polyps in patients with familial adenomatous polyposis. The mechanisms responsible for the ant ineoplastic effect of NSAIDs are not yet completely understood, but one of the possible mechanisms is an induction of apoptosis, We explored the role of caspase-3, a major apoptosis-executing enzyme, in NSAID-induced apoptosi s of colon cancer cell line HT-29. Treatment of MT-29 cells with indomethac in induced a dramatic increase in caspase-3-like protease activity measured by a cleavage of the fluorogenic substrate Ac-DEVD-AMC. Western blot analy sis showed that indomethacin treatment led both to decrease in pro-caspase- 3 and to cleavage of its substrate poly(ADP-ribose) polymerase (PARP). Furt hermore, the caspase-3-like protease inhibitor Ac-DEVD-CHO attenuated indom ethacin-induced DNA fragmentation dose dependently, However, mRNA expressio n of GASP genes was not affected by the addition of indomethacin, highlight ing the importance of posttranslational modification of this enzyme for the activation. These results suggest that NSAIDs, including indomethacin, ind uce apoptosis in colon cancer cells through a caspase 3 dependent mechanism which may contribute to the chemopreventive functions of these agents.