Identification of new susceptibility genes in familial breast cancer by exome sequencing.

1538 Background: Familial breast cancer was described in the early 1970s with its syndromy confirmed by the discovery of BRCA germline mutations in the 1990s. BRCA mutations account for less than 10% of affected families. Efforts made in the past two decades have resulted in limited results in identifying additional susceptibility genes for familial breast cancer. Methods: Using exome sequencing, we analyzed eight members in a BRCA1-, BRCA2-, p53- and PTEN-negative breast cancer family; five with breast cancer and three unaffected. Mutation candidates were idenified by bioinformatics analysis, experimentally validated by Sanger sequencing and their damaging effect was predicted by the SIFT program. Validated mutations were also tested in 42 additional breast cancer samples from BRCA-negative breast cancer families. Results: We identified 55 non-synonymous germline mutations affecting 49 genes in multiple members of this family, 20 of 22 selected mutations predicted to cause damaging effects were validated...