Loss of heterozygosity on chromosome 13q12-q14, BRCA-2 mutations and lack of BRCA-2 promoter hypermethylation in sporadic epithelial ovarian tumors.
BACKGROUND
BRCA-1 and BRCA-2 are tumor suppressor genes in familial breast-ovarian carcinoma syndrome. BRCA-1 is also a tumor suppressor gene in sporadic ovarian carcinomas. However, the role of BRCA-2 in sporadic ovarian tumors remains unclear.


METHODS
DNA from 52 patients with clinically apparent sporadic ovarian tumors was extracted from blood and from fresh-frozen tumor tissue and normal tissue (10 benign, 7 borderline, and 35 malignant). Loss of heterozygosity (LOH) was analyzed in six microsatellite loci on chromosome 13q. BRCA-2 mutations were detected by single-strand conformation polymorphism analysis and the protein truncation test. BRCA-2 promoter methylation was evaluated by methylation specific polymerase chain reaction analysis.


RESULTS
LOH on chromosome 13q12-q14 was identified in 16 tumors (30.8%): Fifteen of these tumors were carcinomas (15 of 35 tumors; 42.8%) and one was a borderline tumor. LOH was frequent in carcinomas with serous differentiation (12 of 16 tumors; 75%). LOH on chromosome 13q12-q14 coexisted with LOH on chromosome 17q in 10 carcinomas. BRCA-2 methylation was not detected in any tumor. BRCA-2 mutations were found in three tumors (one somatic nonsense and two germline frameshift). BRCA-2 fulfilled the two hits for a tumor suppressor gene in these three tumors; in one of them, a BRCA-1 tumor suppressor role had been demonstrated previously.


CONCLUSIONS
The results suggest that BRCA-1 and BRCA-2 may act synergically in sporadic ovarian carcinomas with serous differentiation. The demonstration of BRCA-2 germline mutations in patients with ovarian carcinoma with LOH on chromosome 13q12-q14 and lack of a remarkable family history of cancer suggest that the proportion of ovarian carcinomas that result from hereditary predisposition may be higher than previously estimated.
Gras
E
E
Department of Pathology, Hospital Santa Creu i Sant Pau, Autonomous University of Barcelona, 08025 Barcelona, Spain.
Cortes
J
J
Diez
O
O
Alonso
C
C
Matias-Guiu
X
X
Baiget
M
M
Prat
J
J
D024682:BRCA2 Protein; D002277:Carcinoma / Q000235:genetics*; D002882:Chromosomes, Human, Pair 13; D019175:DNA Methylation; D004273:DNA, Neoplasm / Q000032:analysis; D005260:Female; D016147:Genes, Tumor Suppressor; D006801:Humans; D019656:Loss of Heterozygosity; D018895:Microsatellite Repeats; D009154:Mutation; D009363:Neoplasm Proteins / Q000235:genetics*; D010051:Ovarian Neoplasms / Q000235:genetics*; D010375:Pedigree; D016133:Polymerase Chain Reaction; D018807:Polymorphism, Single-Stranded Conformational; D017422:Sequence Analysis, DNA; D014157:Transcription Factors / Q000235:genetics*
D024682:BRCA2 Protein; D004273:DNA, Neoplasm; D009363:Neoplasm Proteins; D014157:Transcription Factors