Contribution of BRCA1 and BRCA2 mutations to breast cancer in Tunisia

Abstract

e22191 Background: Hereditary breast cancer accounts for 3–8% of all breast cancers. It was recently estimated that a combination of BRCA1 and BRCA2 genes mutations is responsible for 30% of hereditary breast cancer cases. Methods: To investigate the prevalence of BRCA1 and BRCA2 gene mutations in breast cancer patients with affected relatives in Tunisia, 36 patients who had at least one first degree relative affected with breast and/or ovarian cancer were analysed. Thirty three patients are suggestive of BRCA1 mutation and 3 are suggestive of BRCA2 mutation. Results: Four mutations in BRCA1 gene were described among which, one novel splice site mutation (330 dupA) and 3 frameshift mutations including the 4160 delAG, the 2789 delG and the 5385 insC. Our study is the first to describe the 5385 insC mutation which was described only among Jewish Ashkenazi population. Two frameshift mutations (1537 del4 and 5909 insA) were screened in BRCA2 gene. Nineteen percent (7/36) of the familial cases were altered on BRCA1 or BRCA2 genes with deleterious mutations at heterozygous state and 55% (20/36) by mutation with uncertain value (UV) or by single nucleotide polymorphisms (SNPs). Conclusions: Almost all the cases mutated by deleterious mutations on BRCA1 gene reported a family history of breast and/or ovarian cancer in the index case or in their relatives. On the contrary, patients with an UV mutation or SNPs have no history of ovarian cancer in their corresponding families. Our data are the first to contribute to information on mutation spectrum of BRCA genes and offer a recommended screening mode for clinical genetic testing policy in Tunisia. No significant financial relationships to disclose.