These findings provide a crucial new insight into how lungs function on a cellular level and could help scientists devise a test to detect the early stages of lung cancer in people who are at a high risk of developing damaged lungs - such as long term smokers .
The primary role of stem cells is to maintain and repair the tissue in which they are found. But because stem cells are rare in comparison to normal cells, identifying exactly where they are and how they work has remained elusive.
They found that, while stem cells don't appear to be involved in the normal maintenance of healthy or moderately injured lungs, they do play a vital role in repairing severely damaged lungs.
Study author Dr Adam Giangreco, from Cancer Research UK's Cambridge Research Institute, said: "Our results suggest that tissue injury is a catalyst for stem cell activation, as we only saw stem cells working to repair this tissue after severe damage.
"Understanding how stem cells repair damaged lungs will also help us to determine the way in which these cells promote the development of lung diseases including cancer. We hope that these findings lead to improved methods for early lung cancer detection. These might include regular screening for lung stem cell activation in people with a high risk of lung damage."
Lung cancer is the second most common cancer in the UK with 38,000 people receiving a diagnosis every year. The disease is also the most common cause of cancer death in the UK, accounting for more than one in five of all cancer deaths - or 22 per cent.
The earlier lung cancer is diagnosed, the greater the chance of survival. But more than two-thirds of lung cancers are diagnosed at a late stage when the disease is much more difficult to treat successfully.
Co-author Professor Fiona Watt , group leader and deputy director of Cancer Research UK's Cambridge Research Institute, said: "We believe these findings may help us explain why in the context of normal airways, faulty genes do not automatically lead to lung cancer. But when there is severe injury to the lung - caused by smoking or industrial chemicals for example - activation of stem cells carrying these gene defects could then lead to the development of lung cancer."
Dr Lesley Walker, director of cancer information at Cancer Research UK, said: "These are very interesting findings which help to improve our understanding of what goes wrong when lungs become damaged. They could also have important practical applications in terms of detecting lung cancer and improving treatments for the disease.
"Sadly, fewer than ten per cent of lung cancer patients will survival for more than five years after diagnosis, so the need to find better methods of detecting and treating the disease is crucial.
"It's also important to remember that smoking causes nine in ten cases of lung cancer so quitting is the best way to reduce the risk of developing the disease."