Benign polymorphisms in the <scp><i>BRCA</i></scp> genes with linkage disequilibrium is associated with cancer characteristics

Germline pathogenic mutation of the BRCA gene increases the prevalence of breast cancer. Reports on the benign variants of BRCA genes are limited. However, the definition of these variants might be altered with the accumulation of clinical evidence. Therefore, in the present study, we focused on benign single nucleotide polymorphisms (SNPs) of BRCA genes. Linkage disequilibrium was calculated from whole genome sequencing of the BRCA genes obtained from 500 healthy controls and 49 breast cancer patients. Sanger sequencing was used to confirm the mutation. The linkage disequilibrium was noted for seven and three SNPs in the BRCA1 and BRCA2 genes, respectively. Breast cancer with BRCA1/2 linkage disequilibrium was not correlated with a personal history of benign diseases or family history of cancer. Nevertheless, breast cancer with BRCA1 linkage disequilibrium was correlated with high tumor-infiltrating lymphocytes and positive extensive intraductal components. The patients with BRCA1 linkage disequilibrium tended to have worse disease-specific survival. Cancers with BRCA2 linkage disequilibrium are associated with a lower ratio of grade III cancer. Moreover, patients with BRCA2 linkage disequilibrium tended to have better overall survival. In conclusion, linkage disequilibrium from benign SNPs of the BRCA genes potentially affects cancer characteristics.