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J Clin Oncol. 2007 May 20;25(15):2027-34.

Screening for a BRCA2 rearrangement in high-risk breast/ovarian cancer families: evidence for a founder effect and analysis of the associated phenotypes.

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  • 1Molecular Biology Department and Breast Cancer Risk Evaluation Clinic, Instituto Português de Oncologia de Lisboa, Francisco Gentil, Lisboa, Portugal.

Abstract

PURPOSE:

BRCA2 rearrangements are rare genetic events. A large BRCA2 genomic insertion was recurrently observed in our participants, and we sought to characterize it at the molecular and phenotypic level.

PATIENTS AND METHODS:

We studied 210 high-risk breast/ovarian cancer families. Fifty-three probands were fully screened for BRCA1/2 mutations, and three of 53 had a large insertion in exon 3 of BRCA2. This finding was analyzed by polymerase chain reaction (PCR), reverse transcriptase PCR (RT-PCR), and sequencing. An additional 157 consecutive families were screened for this mutation by a three-step PCR method. Phenotype and haplotype analysis was also performed.

RESULTS:

Sixteen BRCA mutations were observed in 19 of 53 patients (36% detection rate). A recurrent Alu motif insertion in position c.156_157 was observed after sequencing of an abnormal fragment obtained after the amplification of BRCA2 exon 3. RT-PCR revealed exon 3 skipping. Screening of this rearrangement identified 14 additional families (out of 157). In total, 17 (8%) of 210 high-risk families ascertained in our clinic were positive for this mutation. Segregation of a common haplotype (from D13S260 to D13S1695) confirmed a common origin, estimated to have occurred 2,400 to 2,600 years ago. The following four cancer phenotypes were observed in the 17 positive families: female breast (n = 9), male breast (n = 4), breast/ovarian (n = 2), and heterogeneous (n = 2). Male breast cancer was more frequently observed in c.156_157insAlu-positive families compared with negative families (23% v 12%, respectively), and 33% of all male breast cancer families with an identified BRCA mutation were c.156_157insAlu positive.

CONCLUSION:

c.156_157insAlu is a founder mutation of Portuguese origin and is the most frequent BRCA2 rearrangement described to date.

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PMID:
17513806
[PubMed - indexed for MEDLINE]
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