LOH analyses in the region of the putative tumour suppressor gene C13 on chromosome 13q13

Background: In previous studies we isolated a new cDNA fragment named C13 w hich is down-regulated in malignant prostate tissues. The corresponding gen e is localized on chromosome 13q13 between the known tumour suppressor gene s (TSG) BRCA-2 and RB-1. Materials and Methods: Loss of heterozygosity (LOH ) analyses were carried out in the region of C13 in order to investigate th e importance of the new putative TSG for prostate cancer development. Using semiquantitative LOH analysis, we screened 21 prostate carcinoma patients of different tumour stages (pT2-pT4) for 14 microsatellite markers in the r egion of C13 (13q13) and in the flanking BRCA-2 and the RB-1 loci. Results: For 18 (86%) patients LOH or allelic imbalances were found. We identified three to nine alterations in affected tumours per marker. An overall geneti c alteration frequency per patient of 38% (86 of 225 informative cases) cou ld be calculated. One important finding regarding the overall frequency of determined microsatellite instability is that the LOH/AI rate of 47% for th e seven C13-associated markers was higher than for the four markers of the RB-1 locus (39%) and for the three BRCA-2 markers (25%). Surprisingly, defi ning LOH critical regions (LCR) for the investigated marker panel, eight of the ten affected LCR cases showed chromosomal imbalances simultaneously fo r the RB-1 and the C13 LOH markers. Conclusions: The high LOH rate for eigh t different microsatellite markers in and around the putative TSG locus C13 on chromosome 13q13 further supports an involvement of C13 in prostate tum ourigenesis.