Mutational analysis of BRCA1 and BRCA2 genes in early-onset breast cancer patients in Shanghai

Abstract

To investigate the prevalence of BRCA1 and BRCA2 mutations among early-onset breast cancer patients in Shanghai. Fifty patients unselected for family history, who were diagnosed with breast cancer before the age of 40 years were analyzed. Among them, 13 patients have at least one first-degree relative affected with breast cancer. Mutation screening of BRCA1 and BRCA2 was performed in the whole coding sequence through Denaturing High Performance Liquid Chromatography (DHPLC) and subsequent DNA direct sequencing. Six deleterious mutations, including 2 novel frameshift mutations (3449insA, 5587-1del8) and 2 novel splice-site mutations (IVS17-1G > T, IVS21 + 1G > C) in BRCA1 were identified. Two deleterious mutations detected in BRCA2, including one frameshift mutation (5950delCT) and one novel missense mutation (5911G > C), all occurring on exon 11 adjacently. Additional 12 novel sequence variants were also detected including one unclassified variant and 7 intronic variants in BRCA1, and 4 novel intronic variants in BRCA2, all causing no alteration of amino acid coding. The prevalence of BRCA1 and BRCA2 mutations in the patients with early-onset breast cancer was 12% and 4%, respectively. Four novel mutations in BRCA1 and one novel mutation in BRCA2 may be mutations characterized of early-onset breast cancer in Chinese population. Germline mutations in BRCA2 may contribute less than mutations in BRCA1 to early-onset breast cancer in Shanghai. These data contribute to information on spectrum of BRCA gene in Chinese population and also offer a recommended screening mode for clinical genetic testing programme in China.