Mutational analysis of BRCA1 and BRCA2 genes in Spanish women with early-onset breast cancer

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Germ line mutations in the BRCA1 and BRCA2 genes predispose women to breast cancer. The prevalence of BRCA1 and BRCA2 mutations in patients with breast cancer who were unselected for a family history has not been determined in the Mediterranean area. We have screened for BRCA1 and BRCA2 mutations 110 women diagnosed with breast cancer before age 40 years in order to determine the prevalence of these mutations. This screening was performed by using PCR-SSCP analysis of multiplexes and DNA fragments resulting from digestion of about 1300 bp-long PCR products with restriction endonucleases. Sequencing of abnormal bands was used to identify mutations.

Mutations that are predicted to encode truncated protein were detected in 7 (6.3%) of 110 women with early onset breast cancer (2 BRCA1 and 5 BRCA2). Mutations that encode missense amino acid change were detected in 8 (7.2%) (4 BRCA1 and 4 BRCA2). This information is important because it determines the cost-benefit implications of genetic testing. We predict that BRCA1 and BRCA2 mutations are approximately equal in our population. A low proportion of the early-onset breast cancer is attributable to mutations in these genes. Clinical and histological features of these women carrying BRCA1\BRCA2 mutations will be presented.