Frequent loss of heterozygosity on chromosome 6 in human ovarian carcinoma

Abstract

Summary Investigation of genetic changes in tumours by loss of heterozygosity (LOH) is a powerful technique for identifying chromosomal regions that may contain tumour suppressor genes. LOH has been described on chromosome 6 in ovarian carcinoma using restriction fragment length polymorphism analysis with a small number of probes. We studied 29 ovarian carcinomas with 19 probes mapping to chromosome 6. Sixteen of the 29 tumours showed LOH on 6q (55%). Of these 16, 63% showed loss of all informative markers on that arm. One tumour showed loss of 6q24-qter, localising the putative tumour suppressor gene to that region. Loss on 6p was 28% overall. However, using three dinucleotide repeat primer pairs from 6p to study LOH in seven (Friend et al., 1986), with the finding that a germline mutation constituted the first 'hit', to be followed by a second, somatic inactivation of the gene, which was usually detectable by RFLP analysis of filters of DNA from matched normal-tumour pairs. More recently, it has been shown that some families with retinoblastoma share a common mutation that can be traced from affected parent to affected child. In these cases, the other allele is lost or inactivated in various ways that differ in different affected family members (Phillips et al., 1991).For soine years there has been considerable cytogenetic evidence that in OC, one chromosome 6, particularly the long arm, is missing in part or in whole (Mitelman, 1991 seven had breakpoints between 6q21 -23, thus loss of the long arm telomeric to this region was the commonest single abnormality of chromosome 6 in this study. Despite the common occurrence of aneuploidy, Atkin et al. (1983) showed that one copy of 6q may be lost in early stage tumours, when the karotype is relatively undisturbed. These data have been followed up more recently by molecular studies of LOH that have broadly confirmed the cytogenetic findings (Ehlen & Dubeau, 1990;Lee et al., 1990).Further data are now needed to accurately define regions of LOH, so that efforts can be concentrated on cloning genes in the relevant region of chromosome 6. Therefore we have studied 29 pairs of matched malignant tumour and normal DNA with ten DNA markers that detect polymorphic sequences on 6q and six that do so on 6p. We also used the centromeric marker p308 (D6ZJ). Oka et al. (1991) showed that by using carefully dissected tumours it was possible to reliably demonstrate LOH by PCR. Subsequently dinucleotide (microsatellite) repeats mapping to chromosome 17 were used to successfully demonstrate LOH in breast cancer (Futreal et al., 1992). Therefore we included the dinucleotide repeats D6S89 and FTHPI, which were utilised to study the regions 6p22.3-23 and 6pl2-21 respectively by PCR-LOH. From the use of these eight 6p probes in all the tumours, we selected seven tumours for a more extensive analysis with three further dinucleotide repeats mapping to the region 6pl2-6p23. We also included 12 nonmalignant ovarian tissue specimens in our RFLP analysis. Although not all these samples wer...

Screening of microsatellite markers in penile cancer reveals differences between metastatic and nonmetastatic carcinomas

“…LOH in 6p22-23-detected in more than 30% of penile carcinoma in this study-has also been shown in cervix carcinoma, 20,24 nonsmall cell lung cancer 25 or ovarian cancer, 26 although no correlations to advanced stages or survival could be established. LOH in microsatellite loci D6S260 and D6S1267 is in this study frequently associated with occurrence of metastases and poor prognosis.…”

Physical map of the D6S149-D6S193 region on chromosome 6Q27 and its involement in benign surface epithelial ovarian tumours

“…This is, on the other hand, in keeping with the telomeric position of the region bounded by them. At variance with the fairly well characterized ovarian carcinomas (Zheng et al, 1991;Iwabuchi et al, 1995;Orphanos et al, 1995;Cooke et al, 1996;Sato et al, 1991, Saito et al, 1992Foulkes et al, 1993;Wan et al, 1994;Tibiletti et al, 1996) very few reports have investigated the involvement of chromosome 6 and, in particular of the long arm, in benign surface epithelial ovarian tumors (BOT) (Orphanos et al, 1995) We therefore decided to exploit the information derived from the cloning of the D6S149-D6S193 region to investigate by FISH analysis its integrity in a panel of benign ovarian tumors (BOTs). Besides the above considerations the rationale for this was the recent localization to 6q27, in a region de®ned by markers D6S133 and D6S281, of a locus for SV40-mediated immortalization of human cells (Sandhu et al, 1994;Banga et al, 1997).…”

“…Keywords: chromosome 6q27; physical map; YAC clones; deletion; benign ovarian tumors The 6q27 region, found to be deleted in ovarian carcinomas and corresponding to loci D6S149 and D6S93 (Saito et al, 1992;Foulkes et al, 1993;Cooke et al, 1996), was cloned by screening CEPH and ICI YAC libraries. With markers D6S149, D6S193 and D6S297 (which is located in between the previous two) used as hybridization probes or for PCR assays, several YAC clones were isolated and characterized (Figure 1 bottom).…”

Loss of heterozygosity on chromosome 5q in ovarian cancer is frequently accompanied by TP53 mutation and identifies a tumour suppressor gene locus at 5q13.1-21

“…In an attempt to refine the location of the candidate region we have analysed for LOH using seven polymorphic microsatellite markers on chromosome Sq (Shepherd, 1989). DNA was isolated from tumours and blood as described by Foulkes et al (1993a).…”