A variant of a gene may have a role in triggering breast cancer in some women, according to a new study published on Monday.
The gene, BARD1, has a variant named Cys557Ser. A team of Icelandic researchers said that the Cys557Ser allele was nearly twice as common in women with breast cancer as in healthy women.
Using a computerized genealogy of the Icelandic population to study the familial cluster of breast cancer, the researchers also found that the variant was more common in women who had a family history of breast cancer or who had developed breast cancer more than once.
The study, conducted by the group from the Reykjavik-based biopharmaceutical company deCODE Genetics, appeared in the June 19 edition of the Public Library of Sciences (PLoS) Medicine, an open-access scientific journal.
The researchers studied 1,090 Icelandic women who had had breast cancer and compared them with 703 unaffected women to see whether the variant was associated with an increased cancer risk.
Earlier studies have found that two genes called BRCA1 and BRCA2 are closely linked with the breast cancer. It is typically estimated that malignant mutations in BRCA1 and BRCA2 account for 15%-25% of the inherited component of the breast cancer risk.
According to the Icelandic researchers, defects in BRCA1 are known to increase the risk of breast cancer, but the protein encoded by BRCA1 interacts with the protein encoded by BARD1. Hence they believe that defects in an interacting protein might have a similar effect.
The most striking result was that carrying the Cys557Ser allele seemed to increase the already high risk of breast cancer in women who had a BRCA2 variant known as BRCA2 999del5, which accounts for 40% of inherited breast cancer risk in Iceland.
These results suggest that inheriting the BARD1 variant allele increases a woman's breast cancer risk, the researchers concluded. But for most women the risk is slight, they added, only those women with the BRCA2 999del5 mutation will have a "dramatically higher" cancer risk.
Moreover, by now the Cys557Ser variant can only be found in European women, according to the researchers. Based on the data of the international human genome project, they found that the Han Chinese, Japanese, and African Yoruba women lack the variant.