6th ESACP Congress, Heidelberg, April 7-11, 1999

A121
GENETIC HETEROGENEITY IN MICRODISSECTED FLAT NEOPLASTIC LESIONS OF THE URINARY BLADDER
Schlake G, Hartmann A, Kutz H, Hofstädter F, Knüchel R,

Institut für Pathologie der Universität, Regensburg, Germany

Aim: Within a study of genetic alterations of early bladder cancer lesions, one important aspect was the investigation of the genes on chromosome 17 and 9 in multifocal carcinoma in situ (CIrS) and moderate urothelial dysplasia (DYSII). Material and Methods: 33 CIS and 14 DYSII from a total of 22 patients were investigated. Sections were cut from frozen tissue, and stained with methylene blue. Urothelium was microdissected and dissolved to a nuclear suspension. Dual colour fluorescence in situ hybridisation was performed with biotinylated probes for the gene loci 9q22(FACC), 9p21(CDK) and 17p13(p53). For the alpha-centromere region of both chromosomes digoxygenated probes were used. The signals of an average of 85 cells were counted. Deletion was defined with > 40% of the cells counted as deleted. Aneuploidy was defined with >10% of the cells counted as polysome for both chromosomes. Controls were taken from normal urothelium and from a normal bladder cell line. Results: In CIS, deletions were found in CDK(85%) > p53(82%) > FACC(76%). DYSII showed comparable results with slightly lower frequency of deletion. Aneuploidy was found in 85% of CIS and in 93% of DYSII, and was found in nearly a third of dysplasias without simultaneous deletion of the gene loci investigated. Conclusions: Data provide first evidence of identical frequencies of chromosome 9 and p53 alterations in flat urothelial lesions, and indicate that DYSII are genetically precursors of CIS. Further polysomy seems to precede the deletions in a significant amount of lesions.