Introduction: Breast cancer (BC) is an important public health problem worldwide. In Brazil, breast cancer is the most frequently diagnosed tumor and the leading cause of cancer death in women. Hereditary cancer represents approximately 5 to 10 % of BC cases. Even outside the hereditary cancer context, the presence of polymorphisms acting as genetic modifiers may contribute to a better or worse prognosis. Not much is known about the hereditary BC epidemiology in Brazil or about the influence of polymorphisms on hereditary predisposition.
Objective: This study examined the role of five different polymorphisms in four groups of women with BC: Group 1: women with a germline mutation in the BRCA1/2 genes; Group 2: women with variants of uncertain significance in BRCA1/2 and Group 3: women with no mutations in BRCA1/2.
Patients and methods: The women included in groups 1, 2 and 3 were patients from the Department of Oncogenetics of the Barretos Cancer Hospital who had undergone genetic testing because of a clinical suspicion of hereditary predisposition syndrome. The constitutive DNA was analyzed for the presence of polymorphisms at rs2981582 (FGFR2 gene); rs3803662 (TNRC9); rs889312 (MAP3K1); rs3817198 (LSP1 gene); and rs13281615 (8q24). The analyses were performed using PCR amplification and bi-directional sequencing.
Results: No differences were identified in the frequency of the polymorphisms that were analyzed among the three groups. However, some associations were identified, such as the occurrence of bilateral breast cancer and homozygosity for the G allele in rs13281615 as well as the correlation between the SNPs rs2981582 and rs13281615 and the number of cancer cases in the family. Regarding the G allele of rs13281615, we observed that the proportion of individuals who were homozygous for this allele increased with the number of generations affected by cancer, regardless of the group where the patients were included. Concerning the rs2981582 we could observe that individuals from group 1 and homozygous CC had fewer cancer (and also fewer breast cancer) cases. Regarding the hormone receptors, we observed an increased frequency in C homozygotes (rs3803662) among estrogen receptor-negative individuals from groups 1 and 3. For rs2981582 (FGFR2), we observed an increased frequency of the T allele in women who were positive for the estrogen and progesterone receptors regardless of the BRCA1/2 mutational status (p = 0.020 and p = 0.014, respectively).
Conclusion: The results presented here provide interesting data on the modifying effect of polymorphisms on a family history of cancer; this may be a variable to consider in the analysis of tumor diversity, and of the family history observed in families with hereditary breast cancer (even in those harboring the same type of genetic alteration).