Genetic variants that modify breast cancer risk identified

It is known that disrupting mutations in the BRCA1 gene increases risk of breast cancer.

Now, Mayo Clinic researchers have discovered that some of those persons may possess additional genetic variants that modify their risk.

"These findings should be useful in helping determine individual risk for breast cancer in BRCA1 carriers," Nature quoted Fergus Couch as saying.

They first studied 550,000 genetic alterations from across the human genome in 1,193 carriers of BRCA1 mutations under age 40 who had invasive breast cancer and compared the alterations to those in 1,190 BRCA1 carriers of similar age without breast cancer.

The 96 single nucleotide polymorphisms (SNPs) discovered were subsequently studied in a larger sample population of roughly 3,000 BRCA1 carriers with breast cancer and 3,000 carriers without cancer.

Further studies of breast cancer patients without BRCA1 mutations showed associations with oestrogen-receptor-negative disease, meaning cancer in which tumours don't possess oestrogen receptors.

In another study, the five SNPs also were associated with triple-negative breast cancer, an aggressive form of the disease. The researchers also found that these SNPs were not related to risk for ovarian cancer in BRCA1 mutations carriers.

By locating these risk-modifying SNPs, the researchers have provided a target for better understanding the mechanisms behind the development of breast cancer.

Furthermore, it may be possible to identify certain BRCA1 carriers who are at lower risk of cancer and, also, carriers at particularly elevated risk of cancer who may decide to change their approach to cancer prevention.

These new findings appear in the current Nature Genetics.