Screening of human bladder carcinomas for the presence of Ha-ras codon 12 mutation

Contradictory results were obtained from previous studies aiming at definin g the frequency of Ha-ras codon 12 mutations in bladder tumors. Differences in the sensitivities of the methods used could account for this discrepanc y. In this study, we reevaluated the frequency of Ha-ras codon 12 mutations in a series of 87 human bladder tumors using a combination of two differen t methods. The first was derived from the protocol of Ooi et al and consist ed in a one-step allele-specific polymerase chain reaction using mismatched primers in two separate PCR. This method is very rapid and highly sensitiv e, detecting the presence of minor populations (less than 10%) of mutant al leles. The second strategy consisted in screening all tumors using natural restriction fragment length polymorphism (RFLP) analysis. The two methods w ere in complete concordance and enabled us to show that only one out of 87 primary bladder carcinomas (1%) exhibited the mutation, in accordance with previous studies. These results strongly suggest that, even if minor cell p opulations overexpress codon 12 Ha-res mutation, the analysis of this mutat ion cannot be used to screen potentially invasive transitional cell tumors of the bladder.