British scientists believe they have discovered an important means by which the body protects itself from cancer.

BBC Science Correspondent James Wilkinson explains the significance of the discovery

The ground-breaking discovery may account for why some heavy smokers manage to evade lung cancer whereas others are less fortunate.

Scientists working for two leading cancer charities have isolated a gene which acts as a self-defence mechanism against the disease.

The gene plays a major part in breaking down cancer-causing toxins, such as those in cigarette smoke. It plays an important role in the lungs and bladder, where smoking is a common cause of cancer.

Scientists carried out initial experiments on laboratory mice

But the anti-smoke pressure group, Ash - Action on Smoking and Health - has warned against complacency.

Ash Director, Clive Bates, says the findings should not be an excuse for young people to take up smoking in the belief that, by the time they are old, cancer can be cured.

The scientists involved in the breakthrough believe the defence gene exists in several different forms which vary in effectiveness.

They hope that in the future those with a defective copy of the gene could be tested and offered treatments to strengthen their protection.

John Wyte: "Tobacco smoke contains many other chemicals"

The discovery was made after experiments on laboratory mice. Scientists found that mice lacking the gene were more than three times more susceptible to cancer after exposure to cigarette carcinogens than mice with a fully functioning gene.

"You take out the gene and you find they've lost their protection against the chemical," said Professor Roland Wolf, who led the team of scientists from the Imperial Cancer Research Fund, the Cancer Research Campaign and the Centre for Genome Research in Edinburgh.

Dr Colin Henderson of the Imperial Cancer Institute: "It confirms what we suspected" (1'44")

Prof Wolf said the gene could be one reason why some heavy smokers escape lung cancer and live to an old age while others die young.

Lung cancer is the most common form of cancer in the UK, causing more than 36,000 deaths a year. According to Ash 80-90% of lung cancers are caused by smoking.

Scientists hope the discovery will one day lead to preventative treatment

"It does open the door to new types of treatment," said Prof Wolf, of the Imperial Cancer Research Fund's Molecular Pharmacology Unit at Ninewell's Hospital in Dundee.

"I think the significance of this discovery comes from its simplicity. If you know that you can modulate a single gene and protect against cancer, that does make it much easier to envisage new forms of cancer prevention."

But smokers have been warned that the finding is not a panacea to their problems.

Professor John Wyte, of the Cancer Research Campaign, said it was not a cue for smokers to relax.

His view was backed by Ash Director Clive Bates.

"It would be terrible if kids started to say that it's okay to smoke now because by the time they are 60 there'll be a cure for lung cancer," said Mr Bates.

"The idea of genetically engineering people to make them more resistant to tobacco smoke is not something to bet your life on."
 

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