[A study of BBN induced bladder cancer in mice. The time differences in changes of histopathology and nuclear DNA content].

To evaluate the process of tumor progression in BBN induced bladder cancer, BBN was administered to C57BL/6 mice for 10 weeks. The mice were sacrificed every week from the 5th week to the 22nd week. The urinary bladder was embedded in paraffin block for histopathological examination and was sampled for DNA content analysis by flow cytometry. The results were as follows: 1. In the histopathological findings, the incidence of atypical hyperplasia of the urinary bladder, indicative of a precancerous state, was 29% 7 weeks after the initiation with BBN. And the cancer was found in 74% of the mice 9 weeks after the initiation. 2. In the analysis of nuclear DNA content, the atypical hyperplasia and the incipient cancer of the urinary bladder were all DNA diploid, and the DNA aneuploid was found in 50% of the cancer group 11 weeks after the initiation. 3. These data suggest that the change of nuclear DNA content is an occurrence after the completion of the carcinogenesis in BBN induced bladder cancer of mice.