Association of a germline copy number polymorphism of APOBEC3A and APOBEC3B with burden of putative APOBEC-dependent mutations in breast cancer.

Abstract

IntroductionThe somatic mutations in a cancer genome are the aggregate outcome of one or more mutational processes operative through the life of the cancer patient1-3. Each mutational process leaves a characteristic mutational signature determined by the mechanisms of DNA damage and repair that constitute it. A role was recently proposed for the APOBEC family of cytidine deaminases in generating particular genome-wide mutational signatures1,4 and a signature of localized hypermutation called kataegis1,4. A germline copy number polymorphism involving APOBEC3A and APOBEC3B, which effectively deletes APOBEC3B5, has been associated with a modest increased risk of breast cancer6-8. Here, we show that breast cancers in carriers of the deletion show more mutations of the putative APOBEC-dependent genome-wide signatures than cancers in non-carriers. The results suggest that the APOBEC3A/3B germline deletion allele confers cancer susceptibility through increased activity of APOBEC-dependent mutational processes, although the mechanism by which this occurs remains unknown.