Abstract LB-284: Exome sequencing of high-risk Finnish hereditary breast and breast-ovarian cancer families

Abstract

Abstract Background: Breast cancer has a well-established genetic component. However, genetic predisposition factors remain mostly unresolved in high-risk hereditary breast cancer families that do not carry mutations in two major susceptibility genes, BRCA1 and BRCA2. In this study, we aimed to identify rare variants contributing to disease susceptibility in the high-risk Finnish BRCA1/2-negative hereditary breast or breast-ovarian cancer families by using family-based exome sequencing approach. Methods: Germline DNA of 37 individuals from 13 high-risk hereditary breast or breast-ovarian cancer families was analyzed using targeted exome capture and massively parallel sequencing. Priority was given for rare (minor allele frequency<0.05) coding functional variants including nonsynonymous single nucleotide variants (SNVs), frameshift indels as well as stoploss/stopgain and splice-site variants. Candidate variants were selected based on the computational pathogenicity predictions by several tools and gene pathway analyses. Moreover, segregation of the variants with the disease was studied in the families. Candidate variants were confirmed by Sanger sequencing and genotyped in additional cohorts of breast cancer patients and healthy controls. Results: Altogether 21,530 rare coding functional variants (97.0% nonsynonymous SNVs, 1.6% frameshift indels, 1.4% stoploss/stopgains variants) as well as 5 splice site variants were observed in 37 individuals. Of these, 93 novel variants, that harbor genes participating in the DNA damage response pathway, were prioritized. Furthermore, only variants that were predicted to be pathogenic, were considered and they were manually studied through literature. Altogether 20 candidate variants were selected for further segregation, validation, and genotyping experiments, which are currently ongoing. Conclusions: Identified rare functional variants especially in the DNA damage response pathway genes can explain a fraction of the genetic predisposition to breast and ovarian cancer in the high-risk Finnish families. Citation Format: Kirsi M. Kuusisto, Tommi Rantapero, Minna Kankuri-Tammilehto, Matti Nykter, Satu-Leena Laasanen, Johanna Schleutker. Exome sequencing of high-risk Finnish hereditary breast and breast-ovarian cancer families. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr LB-284. doi:10.1158/1538-7445.AM2015-LB-284