Summary A gene that could help explain why some non-smokers develop lung cancer has been found.
It is hoped that further research into the GPC5 gene could open the way for new targeted treatments as well as picking out those at high risk.
But Cancer Research UK said more work was needed to work out the exact reason for the link.
A quarter of lung cancers globally occur in people who have never smoked, The Lancet Oncology reports.
In the UK, 10% of lung cancers develop in people who do not smoke.
The researchers said lung cancer in non-smokers was an increasing problem but the causes were not well understood.
DNA samples from 754 people who had smoked fewer than 100 cigarettes in their lifetime were scanned to find the genetic differences that seemed most likely to affect the risk of lung cancer.
