Smokers leave a history of their addiction in DNA

6 November 2012

Smokers are leaving a history of their addiction in their DNA that may help to measure their risk of cancer, according to research presented at the NCRI Cancer Conference, on Tuesday 7 November.

Researchers at Imperial College London and the Human Genetics Foundation (HuGeF) in Italy have identified a number of sites in the DNA of blood that have been chemically tagged as a result of smoking. These tags are also detectable in lung tissue and could be used to measure the increased risk of certain cancers such as breast and bowel, as well as lung.

Smoking leaves a footprint on the surface of the DNA but the sequence of genetic code remains the same. This is known as an “epigenetic” modification. Once you give up smoking, these tags start to disappear although they never quite match the unmarked DNA of a non-smoker.

In this initial study, measuring the level of tagging allowed the researchers to investigate the risk of breast and bowel cancer associated with smoking, with plans to expand the work into other areas such as lung cancer.

A link between smoking and breast cancer has not been proven but the researchers believe that previous studies haven’t had the same genetic or epigenetic measures of smoke exposure available. This test will make that information available to scientists so they can spot any DNA tags that might be attributable to any risk that might exist.

Dr James Flanagan, Breast Cancer Campaign scientific fellow at Imperial College London and co-author of the research, said: “This research may help to build a test that will be able to look at a person’s epigenetic information at the molecular level and measure in great detail the added risk of cancer from exposures such as smoking.

“Previous research into smoking has often asked people to fill out questionnaires, which have their obvious drawbacks and inaccuracies. Using this approach, we will be able to read the fingerprint on a person’s DNA to tell us a story of how their habit may have changed over the course of their life.”

Professor Paolo Vineis, chair in environmental epidemiology at Imperial College London’s School of Public Health and head of the HuGeF laboratory in Italy, said: “This research will help us to build a molecular profile of cancer risk, where we can screen people and quantify the exposure they’ve had to a number of risk factors over their lifetime, just by examining a blood sample.

“We hope that smoking is just the start – further work will look into other factors like alcohol and start to measure the risk an individual has built up over a lifetime of exposure to these contributors to cancer.”

Dr Jane Cope, director of the NCRI, said: “This reinforces the message that smoking doesn’t just affect the risk of lung cancer, it can increase the risk of more than a dozen different cancers. Smokers lose around a decade of life and, along with many other benefits, giving up will mean the added risk of cancer drops off over time.”

Baroness Delyth Morgan, Chief Executive, Breast Cancer Campaign said, “There is currently limited evidence available to understand the role of smoking as a risk factor for breast cancer so Dr Flanagan’s findings are fascinating. The message is, lifestyle choices have a real and lasting impact on our DNA and ultimately our risk of developing cancer.

“The potential to reverse or counteract epigenetic changes is also an exciting possibility for future research and we look forward to seeing more from Dr Flanagan’s research.”

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