Relevance of p53 gene alterations for tumor recurrence in patients with superficial transitional cell carcinoma of the bladder

Purpose: The prognostic relevance of p53 protein accumulation in muscle-inv asive bladder carcinoma is well documented, but the prognostic relevance of p53 alterations in superficial bladder tumors remains uncertain. Immunohis tochemical data are divergent, possibly because of the use of nonstandardiz ed techniques. We therefore investigated the relevance of p53 gene point mu tations and loss of heterozygosity (LOH) for tumor recurrence. The results of this molecular analysis were compared with accumulation of the p53 prote in as shown by immunohistochemistry. Material and Methods: Representative tumor tissue was selected and microdis sected from 40 patients (pTa, 18 patients; pT1, 22 patients; grade 1, 7 pat ients; grade II, 28 patients; grade III, 5 patients). Polymerase chain reac tion (PCR) was carried out with exons 5-8. All PCR products were screened f or p53 mutations with temperature-gradient gel electrophoresis (TGGE). When mobility shift was observed, direct nucleotide sequencing was performed. D etection of LOH was performed with nonradioactive microsatellite analysis u sing three markers (TP 53, D17S513 and D17S786) on chromosome 17p. Immunohi stochemistry was performed with the DO 7 antibody. Tumor samples with p53 a ccumulation of 5% or more positive nuclei were classified as positive. Univ ariate analysis for disease-free survival was performed using Kaplan-Meier analysis and the log-rank test. Results: TGGE and direct sequencing detected mutations in 10 of 40 patients (2 of 18 pTa and 8 of 22 pT1 patients). LOH was detected in 11 patients. B oth a mutation and LOH were detected in 3 patients. p53 immunohistochemistr y detected at least 5% positive nuclei in 28 of 40 patients (70%). After a median follow-up of 26 months 14 patients suffered disease recurrence. Wher eas disease-free survival did not correlate with a mutation (p = 0.77, log- rank test), LOH (p = 0.2) or a mutation in combination with LOH (p = 0.23), a positive p 53 immunoreaction was significantly associated with short dis ease-free survival (p = 0.009). Conclusion: Despite the relatively high percentage of patients with p53 gen e alteration in this population no significant correlation between the dete ction of molecular alteration and disease recurrence could be found. We con clude that, in contrast to immunohistochemical accumulation, gene alteratio ns play only a minor role in tumor recurrence of p53 in patients with super ficial transitional cell carcinoma of the bladder, and that immunohistochem ical accumulation of the p53 protein has to be explained by mechanisms othe r than gene mutations. Copyright (C) 2001 S. Karger AG, Basel.