Cancer news
Genetic variants increase smokers’ risk of lung cancer
Scientists have identified genetic variants that increase a person’s risk of developing lung cancer, but only if they have ever smoked. The findings will shed light on how people get addicted to tobacco and how our genes and environment conspire to cause cancer.
More than 38,300 new cases of lung cancer are diagnosed in the UK each year and more than 33,000 people die from the disease, according to Cancer Research UK. Worldwide it is the most common cancer with 1.3 million people diagnosed every year.
Smoking is responsible for nine out of ten cases in the UK, with smokers 26 times more likely than non-smokers to develop the disease. Though all smokers and former smokers have a higher risk of developing lung cancer, fewer than a fifth will get the disease, and scientists have been trying to get a handle on how genetic factors might increase a person’s lifetime risk of developing lung cancer.
To help answer this question, three teams worked independently to scan the genomes of more than 60,000 people, some with lung cancer and some without. Their results, published on Thursday in the journals Nature and Nature Genetics, are the first to identify common genetic variants that influence lung cancer risk.
All three studies found two genetic variants on chromosome 15 that were more common among the lung cancer patients than the healthy people. The variants, which encode nicotine receptors on cells, are thought to play a role in nicotine addiction and researchers estimate that more than half of the general population have a copy of one of the disease variants and 10-15% have two copies.
People who smoke and who carry one copy of each genetic variant increase their risk of lung cancer by 28%. Those who smoke and have two copies of each variant increase their risk by 80%. However, people who carry the variants but who have never smoked are not at any increased risk of the disease.
Exciting results
Paul Brennan from the International Agency for Research on Cancer in Lyon, who led one of the teams, said: “These results are particularly exciting as they provide the first identification of a major genetic factor that contributes to lung cancer risk. These findings will help us understand why lung cancer develops, and may indicate new strategies for treating the disease.
“They should not, however, detract from the main lung cancer message that people who do not smoke should not start and people who smoke should quit. Even those who do not have any copies of the risk genes have an important risk of developing lung cancer, as well as other tobacco-related diseases.”
The groups did not agree on how the genetic variants they found might actually increase the risk of lung cancer. One theory is that they influence smoking behaviour, making people want to smoke more, for example, or making it difficult for them to quit. Increased consumption of cigarettes would then lead to a higher risk of cancer. The alternative is that the genetic variants play a more direct role in the development of the disease.
Christopher Amos of the University of Texas, who led one of the other teams, said: “What we do not understand is why some long-term smokers develop lung cancer and others don’t. There are so many different cancer-causing compounds in tobacco smoke that it’s hard to separate them and we don’t fully understand the mechanisms that cause lung cancer.”
Extra vulnerability
Lesley Walker, director of cancer information at Cancer Research UK, said: “We know that smoking greatly increases the risk of lung cancer – causing nine out of ten cases of the disease. This research tells us there are some smokers who are even more vulnerable to lung cancer because of their genetic profile.”
She added: “It will be some time before we are able to identify who is most at risk of developing lung cancer, but when we do, this could help us discourage people from taking up smoking altogether. Stop Smoking services could also be more specifically tailored to this group, but all smokers would be strongly encouraged to quit, as they are still at high risk of developing a tobacco-related disease.
“It’s important to remember that the best thing a smoker can do to reduce their risk of lung cancer and a host of other life-threatening diseases is to quit.”
Kari Stefansson, chief executive of the Icelandic company deCODE, which looked at 40,000 people in the third analysis, said: “This is an important advance that we will use in our diagnostics programmes to develop means to enable individuals and their doctors to better understand and reduce the risk of smoking to their health.”
Source: guardian.co.uk
