About a quarter of smokers who have a defect in the BRCA2 gene, best known for increasing the risk of breast cancer, will develop lung cancer at some point in their lifetime, according to a study published in Nature Genetics on June 1.

Researchers led by a team at the Institute of Cancer Research in London discovered the previously unknown link between lung cancer and the particular BRCA1 defect by comparing the DNA of 11,348 Europeans with lung cancer to 15,861 without disease. Looking for differences at specific points in the participants’ DNA, the researchers discovered that the defect increases the risk for developing lung cancer by 1.8 times.

The study’s findings additionally revealed that the link between lung cancer and defective BRCA2 was particularly strong in patients with squamous cell lung cancer. An association was also observed between squamous cell lung cancer and a defect in a second gene: CHEK2. In the future, patients with squamous cell lung cancer may potentially benefit from drugs specifically designed for effectiveness in cancers with BRCA mutations.

“Smokers in general have nearly a 15 percent chance of developing lung cancer, far higher than that in non-smokers. Our results show that some smokers with BRCA2 mutations are at an enormous risk of lung cancer—somewhere in the region of 25 percent over their lifetime,” said Richard Houlston, Professor of Molecular and Population Genetics at the Institute of Cancer Research, in a press release. “We now know that the single biggest thing we can do to reduce death rates is to persuade people not to smoke,” he continued, “and our new findings make plain that this is even more critical in people with an underlying genetic risk.”