Purpose: To test the value of a recently developed screening method for the detection of p53 mutations in prostate and bladder cancers.
Materials and methods: Tumor tissue from 24 prostate cancers and 27 bladder cancers were evaluated. DNA of the critical p53 exons 5-8 were amplified and run on horizontal polyacrylamide gels under defined temperature conditions (TGGE) to yield specific gel shifts and sets of homo- and heteroduplexes in case of mutation. Sequencing with a laser-fluorescent electrophoresis unit was done directly from polymerase chain reaction (PCR) products and/or from reamplified mutant and wild type bands excised from the gels.
Results: The p53 genotype predicted from the TGGE analysis was always confirmed on the excised DNA fragments, in contrast to only 50% of cases tested by direct sequencing from mixed wild type and mutant DNA present in PCR products. With this screening protocol, 6 of 24 prostate cancers (25.0%) and 11 of 27 bladder cancers (40.7%) showed p53 mutations. At stage T1, none of prostate cancers and 41.2% of bladder cancers contained mutant p53. At higher stages (> or = T2), 30.0% of prostate cancer and 50.0% of bladder cancers were mutated. Histological tumor grading was > G1 in all but two prostate/bladder cancers with mutant p53. It appears that p53 mutations can occur early in bladder carcinogenesis.
Conclusion: TGGE fulfills the clinical need of a rapid and specific screening method, and, at the molecular level, has the advantage of sorting out the wild type and mutant alleles for consecutive sequencing.