The effects of aspirin on the urinary bladder carcinogenesis in rats treated with
N-butyl-N-(4-hydroxybutyl) nitrosamine (BBN) were studied. The effects of chemoprevention
of aspirin were evaluated with incidence of preneoplastic lesions. Forty-five
female Sprague-Dawley rats were divided into three groups. Group A received 0.05%
BBN in drinking water for 12 weeks. Group B received 0.05% BBN in drinking water with
0.5% aspirin in the diet for 12 weeks. Group C received control diet without added
chemicals. The rats were sacrificed after 12 weeks. There were no typical preneoplastic
lesions in the control group. Preneoplastic lesions such as simple hyperplasia, focal
hyperplasia and papilloma were noted in Group A and B. The incidence of simple
hyperplasia, focal hyperplasia and papilloma in Group A was 100%, 100% and 80%,
respectively. The incidence of simple hyperplasia, focal hyperplasia and papilloma in
Group B were 100%, 100% and 20%. Counts of focal hyperplasia and papilloma lesion
in each rat were significantly reduced in Group B than in Group A (P＜0.001). The result
suggests that aspirin significantly decreases the incidence of precancerous lesions
induced with BBN and it can act as an effective cheomopreventive agent for
precancerous lesions in urinary bladder.

Keywords: Carcinogenesis, Bladder tumor, Chemoprevention, Aspirin