The international team of investigators led by the University of Melbourne, identified rare mutations in the RINT1 gene to increase risk of breast and many other cancers.
"This discovery will assist some more women learn the genetic explanation for their breast cancer risk and which of their family members are at high risk of developing cancer.
Currently only about 35 per cent of the familial risk for breast cancer has been explained," Professor Melissa Southey from the University's Department of Pathology, said.
"Although mutations in RINT1 are rare, it is most likely that the remaining unknown breast cancer susceptibility genes will account for similar small proportions of the disease," said co-researcher Dr Daniel Park.
Rare mutations in RINT1 were identified in three of 49 families participating in a multiple-case breast cancer family study. The study applied the latest technology to search for unidentified breast cancer susceptibility genes.
The researchers then assessed the association between RINT1 mutations and breast cancer risk by conducting a population-based case-control study that identified 23 mutation carriers in a sample of 1,313 women diagnosed with early-onset breast cancer and only 6 mutation carriers in 1,123 unaffected women, demonstrating a significant association between mutations in RINT1 and risk of early onset breast cancer.
Further research included testing an additional 684 affected women from multiple-case breast cancer families for RINT1 mutations and six additional families were found to carry mutations in RINT1.