Objective: To determine some of the genetic alterations involved in the pathogenesis and progression of transitional cell carcinoma of the bladder. Materials and methods In a population-based study, freshly frozen tissue was collected from all patients newly diagnosed with urinary bladder cancer in the Stockholm region during 1995-1996. The prevalence of loss of heterozygosity (LOH) was assessed at seven sites on chromosome 3, analysed in 151 patients, using a fluorescent multiplex polymerase chain reaction based on DNA from the tumour and peripheral blood.
Results: LOH was detected in 12.1% (at 3q25-26.2) to 22.1% (at 3p11-12) of the informative cases. Relatively frequent LOH was detected at 3p22-24.2 (21.6%), at 3p14.2 within FHIT (21.5%), and at 3p11-12 (22.1%). Of 151 tumours, 72 (47.7%) showed LOH at one or more loci on chromosome 3. LOH on chromosome 3 was weakly associated with tumour grade (P = 0.095), but not with tumour stage (P = 0.701). However, when the frequency of LOH was analysed individually at each site, the prevalence of LOH at 3p11-12 was closely correlated with higher tumour stage (P = 0.011). Replication errors were detected in only four of 151 (2.6%) tumours. Conclusion These findings suggest that the 3p11-12 locus may involve a putative candidate tumour-suppressor gene which might be associated with bladder tumour invasiveness. The FHIT gene locus showed a relatively high frequency of LOH even in Ta tumours.