Chemoprevention for colorectal tumorigenesis associated with chronic colitis in mice via apoptosis.

The mechanism of the suppressive effect of nonsteroidal anti-inflammatory drugs in azoxymethan and dextran sulfate sodium-induced colonic aberrant crypt foci/tumors associated with chronic colitis in mice was studied. With administration of sulindac, a cyclooxygenase-1 and -2 inhibitor, the mean number of colonic aberrant crypt foci/tumors was significantly smaller than that of controls. There was no significant difference in prostaglandin E2 content in the colonic mucosa between the groups. Furthermore, nimesulid, a cyclooxygenase-2 selective inhibitor, also suppressed colonic aberrant crypt foci/tumors as well as sulindac. Administration of nimesulid caused apoptosis indices to be significantly higher along with cyclooxygenase-2 expression being significantly lower than in controls. Apoptosis indices of 400 ppm group of nimesulid were significantly higher than that of 200 ppm group. Nonsteroidal anti-inflammatory drugs distinctly suppress the occurrence of aberrant crypt foci/tumors in this murine colitis-associated neoplasia model. Induction of apoptosis is a more important factor for chemoprevention than this reduction of prostaglandin E2.