Common germline haplotypes and genotypes identified in BRCA2 exon 11 of dogs with mammary tumours and histopathological analyses.

The canine BRCA2 is a tumor supressor gene which encodes the BRCA2 protein, involved in DNA repair through interaction with the RAD51 recombinase. This process is mediated by eigth BRC repeats that are encoded by BRCA2 exon 11. Two variants corresponding to human mutations in human BRC3 repeat have been reported in canine BRC3 repeat. In addition, other variants have also been described in canine BRCA2 exon 11. Considering the importance of polymorphisms in human BRCA2 to breast cancer development, this study aimed to investigate the frequency of variants in BRCA2 exon 11 in 48 blood and tissue DNA samples from bitches with canine mammary tumors (CMT), as well as, to analyze tumor stage and histopathological features. Seven Single Nucleotide Polymorphisms (SNPs) were identified, three of which were evaluated as possibily or probably deleterious variant. Interestingly, almost all the 22 mammary tumors (except one) which presented a clinical staging equal to or greater than III carried at least one mutant allele of these three variants. Besides that, no statistically significant correlation was observed between any of the reported SNPs in heterozygosis or homozygosis and either dogs data (such as breed, age or disease stage) or mammary tumors histopathological characteristics. A total of 97.9% of bitches had one to three polymorphisms of the seven identified in this study, which suggests a possibly correlation between the canine BRCA2 exon 11 polymorphisms and mammary carcinogenesis.