Methylation pattern and mutational status of BRCA1 in canine mammary tumors in a Brazilian population

In female dogs, mammary tumors are the most common neoplasia representing about 50% of the tumors affecting this species. In women, the importance of mutations in BRCA1 and mammary tumors development is well established. However, little information is available on the molecular mechanisms that contribute to canine mammary tumors. In this work, we evaluated the mutational and methylation status of the BRCA1 gene, in tumoral and non-tumoral tissues of canine mammary glands in order to characterize its influence in mammary carcinogenesis on this species. Samples of 16 animals were collected and two hotspot regions (intron 8-exon 9 and 5′UTR) were sequenced. For methylation analysis, the bisulfite sequencing PCR approach was used. No evidence of hypermethylation was observed in the BRCA1 promoter region, suggesting this mechanism may not be involved in BRCA1 silencing in canine mammary tumorigenesis. No alteration was observed in intron 8-exon 9 region. On the other hand, two polymorphisms in the 5′UTR region were observed: a transition (T > C) that has not been previously described in the literature, and observed in one patient with an unfavorable prognosis, and the previously described transversion (C > G). We suggest that methylation is not the main BRCA1 inactivation mechanism in sporadic CMTs. Regarding the genetic alterations, two variations were detected in our population, and we were able to detect regional allele frequency differences in our population.