Breast cancer susceptibility variants alter risks in familial disease

Abstract

Background: Recent candidate and genome-wide association studies have identified variants altering susceptibility to breast cancer.

Objective: To establish the relevance of these variants to breast cancer risk in familial breast cancer cases both with and without BRCA1 or BRCA2 (BRCA1/2) mutations.

Methods: A cohort of unrelated individuals with breast cancer due to the presence of either BRCA1 (121) or BRCA2 mutations (109) and individuals with familial breast cancer not due to BRCA1/2 mutations (722) were genotyped using Taqman SNP Genotyping Assays. Allele frequencies were compared with an ethnically and gender-matched group (436).

Results: A synonymous variant (Ser51) in TOX3 (previously TNRC9) was associated with an increased risk of breast cancer (OR=1.82, p<0.001) in BRCA2 mutation carriers. The associations for FGFR2 (OR=1.20, p=0.046), TOX3 (OR=1.5, p<0.001), MAP3K1 (OR=1.26 p=0.03), CASP8 (OR=0.73 p=0.02) and the chromosome 8-associated SNP (OR=1.31, p=0.004) were replicated in individuals without BRCA1/2 mutations. In addition, homozygote carriers of MAP3K1 variants were shown to have a significantly lower Manchester Score (mean 13.8-17.6, p=0.003), whereas individuals carrying one or two copies of the FGFR2 variant had a higher Manchester Score (mean 17.5-17.9, p=0.01).

Conclusions: This study confirms that susceptibility variants in FGFR2, TOX3 and MAP3K1 and on chromosome 8q are all associated with increased risk of cancer in individuals with a family history of breast cancer, whereas CASP8 is protective in this context. The level of risk is dependent on the strength of the family history and the presence of a BRCA1/2 mutation and contributes to the understanding of the use of these variants in clinical risk prediction.