p53 Gene mutations in superficial bladder cancer

Objectives: To assess the presence of p53 gene mutations in superficial tumors of the urinary bladder (transitional cell carcinoma) and their relationship to classic prognostic factors for cancer recurrence and progression. To analyze the implication of these mutations on the P53 protein structure.

Materials and methods: Observational, cross-sectional study of 90 consecutive patients, 60 with superficial transitional cell carcinoma (pTa and pT1) and 30 without neoplastic disease (control group). Samples of bladder tumor and control normal mucosa were analyzed by polymerase chain reaction-single-strand conformation polymorphism (PCR-SSCP) to detect p53 mutations in exons 5-9. Automatic sequencing was used to characterize the mutations and their effect on the P53 protein was analyzed. Bivariate analysis was used to assess the association with other prognostic factors.

Results: PCR-SSCP found no mutations in any control group patient, whereas 38.3% of patients with superficial transitional cell carcinoma had one or more mutations in the exons analyzed. Thirty mutations were sequenced; all were point mutations and 86.67% were considered relevant for the P53 structure. A total of 93.3% of the mutations were located in highly conserved regions and 73.3% in mutational hot spots. The highest cell differentiation grades and pT1 stage were associated with a higher incidence of p53 gene mutations. Previous recurrences and other tumor-related histological variables were not associated with a higher percentage of mutations.

Conclusion: Mutations at p53 did not appear in healthy bladder mucosa and were significantly more frequent in pT1 and high-grade (G-II and G-III) tumors. All mutations detected were point mutations and most caused considerable P53 structural abnormalities, implying major repercussions on P53 function. These data suggest that certain p53 mutations may have prognostic value, even though they were not associated with other classic recurrence and tumor progression parameters. Future analyses of the progress of patients with superficial bladder transitional cell carcinoma and mutated p53 will help clarify this aspect.