ABSTRACT
The modification effects of nimesulide, a cyclooxygenase (COX)-2 inhibitor, administration during the postinitiation phase of pancreatic carcinogenesis were investigated in hamsters treated with N-nitrosobis(2-oxopropyl)amine (BOP). Male Syrian hamsters were given 4 weekly s.c. injections of BOP at a dose of 10 mg/kg and thereafter administered 0, 100 or 400 ppm nimesulide in the diet for 36 weeks. Additional groups of hamsters were fed 400 ppm nimesulide without prior BOP initiation or nontreated. At week 40, all surviving animals were killed and development of neoplastic and preneoplastic lesions was assessed histopathologically. The incidence of pancreatic adenocarcinomas was significantly (p < 0.05) decreased in the BOP/400 ppm nimesulide group compared to the BOP alone group. The multiplicity of total lesions of pancreatic adenocarcinoma plus atypical hyperplasia was also significantly (p < 0.05) lowered. Immunohistochemically, COX-2 was clearly expressed in pancreatic and lung tumor cells, whereas expression was not remarkably affected by the 400 ppm nimesulide treatment. Proliferating cell nuclear antigen labeling indices of pancreatic ducts were significantly (p < 0.01) reduced by nimesulide. The incidence and multiplicity of neoplastic lesions in other organs did not significantly differ among the BOP-treated groups, though only the multiplicity of lung tumors showed a tendency to decrease. No neoplastic lesions were detected in animals receiving nimesulide alone. Our results clearly indicate that nimesulide protects against BOP-induced pancreatic tumors in hamsters.