Effect of intravesical bacillus Calmette-Guérin on N-butyl-N-(4-hydroxybutyl)-nitrosamine induced urinary bladder carcinogenesis in rats

Abstract

The effect of intravesical Bacillus Calmette-Guérin (BCG) on N-butyl-N-(4-hydroxybutyl)-nitrosamine (BBN) induced urinary bladder carcinogenesis was pathologically evaluated. As a suppressive study of BCG on initiation, F344 female rats given 0.05% BBN orally for 6 weeks had intravesical instillation of either BCG or saline 3 times during BBN administration (Group A). As an inhibitory study of BCG on promotion, F344 female rats given the same strength BBN for 10 weeks had intravesical instillation of either BCG or saline 4 times starting at 7th week of BBN administration (Group B). The bladders were extirpated at 18th or 36th week after BBN administration in Group A and at 10th or 18th week in Group B. The lesions in the bladder were classified into 4 pathological findings; simple hyperplasia, papillary or nodular hyperplasia, papilloma and transitional cell carcinoma. The incidence of the lesions and the number of the lesions per 10 cm basement membrane were observed. BCG did not inhibit the growth of transitional cell carcinoma in Group A nor in Group B, rather partly promoted carcinogenesis. These results indicate that BCG have no inhibitory effect on carcinogenesis. We concluded that prophylactic effect of intravesical BCG is not due to inhibition of carcinogenesis but elimination of residual tumors by strong antitumor effect of BCG.