Objectives: To investigate the prevalence of loss of heterozygosity (LOH) at 12 different loci on chromosome 9 in patients with bladder neoplasms using a newly developed fluorescent multiplex polymerase chain reaction.
Patients and methods: In a population-based study, freshly frozen tissue was collected from all cases of newly detected bladder neoplasms in the Stockholm region during 1995 and 1996 (n = 538) and 156 representative cases were subsequently studied in the present series.
Results: In total, at one or more loci of chromosome 9, 89% (139/156) of the tumours showed LOH. Loss of heterozygosity in informative cases was in the range from 33.1% (41/124) at the 9p21 locus to 67% (77/115) at the 9q31.3-32 loci. When minor LOH was studied, representing a single LOH with retention of heterozygosity at both adjacent markers, relatively frequent losses were detected at 9q22.3 harbouring the PTCH gene (7.7%), at 9q32-33.1 (6.6%) and at 9q33.2 harbouring the DBCCR1 gene (7.5%). In relation to clinical information, LOH at 9p22.1 was statistically significantly correlated with tumour grade (p = 0.01), but not with tumour stage. Replication errors were observed in 14 of 156 (9%) tumours.
Conclusions: Our observation of relatively frequent minor LOH at 9p22.1, 9q22.3 and 9q32-33.1 identifies regions within which putative tumour suppressor genes, including the PTCH and the DBCCR1 genes, may reside.