To define regions of deletion on chromosome 6q in papillary serous
carcinoma of the peritoneum (
PSCP), we analyzed 103
tumor tissues from 53 patients by using 11 polymorphic microsatellite markers spanning loci from 6q23 to 6q27. Allelic losses on 6q were observed in 42 of 53 (79.2%) cases. We identified 3 distinct regions with a high percentage (>40%) of loss of heterozygosity. The first region is located at 6q23-24 and defined by D6S311 (15 of 35 informative cases, 42.9%). Detailed deletion mapping of chromosome 6q23-24 in these
tumor samples identified a novel 9 cM minimal deletion region flanked by D6S250 and ESR. The second one is located at 6q25.1-25.2 and defined by D6S448 (17 of 36 informative cases, 47.2%). A second minimal deletion region of 4 cM was flanked by D6S420 and D6S442. The third region is located at 6q27 and defined by D6S297 (9 of 19 informative cases, 47.4%). Comparing these results with our cases of advanced staged invasive serous
epithelial ovarian carcinoma (SEOC), we observed that allelic losses at D6S311 (6q23) and D6S149 (6q27) were significantly higher for
PSCP than for SEOC. The pattern of allelic loss at each
tumor site within an individual patient was also studied. A total of 36 cases displayed allelic loss for at least 1 of multiple
tumor sites, and 35 of these patients exhibited nonidentical patterns of allelic loss at various
tumor sites of the same patient. Furthermore, an alternating pattern of allelic loss in the same patient was identified in 3 of 53 patients studied. These results show that allelic losses on 6q are very frequent in
PSCP, and we show 2 discrete minimal deletion regions on 6q, suggesting the existence of at least 2 tumor suppressor genes within 6q that may be involved in the pathogenesis of
PSCP. In addition, the finding of different patterns of allelic loss at different
tumor sites within the same patient indicate a mutifocal origin in some
PSCP cases. These results provide strong evidence to support our previous reports that
PSCP is a multifocal disease entity.