Genetic instability and p53 mutations in metastatic foci of mouse urinary bladder carcinomas induced by N-butyl-N-(4-hydroxybutyl)nitrosamine.

In a variety of human malignancies, alteration of the p53 tumour suppressor gene is known as a significant indicator of late progression events including invasion and metastasis, with a possible close relationship to genetic instability. Mutational analysis of the p53 and H-ras genes was performed for 10 pairs of N-butyl-N-(4-hydroxybutyl)nitrosamine-induced invasive mouse urinary bladder carcinomas and metastatic foci. p53 Mutations were found in nine of 10 (90%) primary carcinomas and seven of 10 (70%) metastatic foci. A total of eight p53 mutations in primary carcinomas were common in metastatic foci in six pairs. Additional p53 or H-ras mutations which were not identified in the primary carcinomas were found in three metastatic foci. Evaluation of the allelic distribution of the p53 mutations using RT-PCR, PCR and subcloning, further indicated possible intra-tumour genomic heterogeneity or excess copy numbers of the p53 gene due to genetic instability. Overall, p53 alterations were frequent in mouse urinary bladder carcinomas demonstrating progression. The results suggest that genetic instability might underlie generation of additional genetic alterations in this animal model.