Your lungs have an almost “magical” ability to repair cancerous mutations caused by smoking, but only if you stop doing so, scientists say.
Mutations that lead to lung cancer were considered permanent and persist even after quitting smoking.
But the surprise findings, published in Nature, show that the few cells that escape damage can repair the lungs.
The effect has been observed even in patients who had smoked a pack a day for 40 years before giving up.
Thousands of chemicals in tobacco smoke corrupt and mutate the DNA in lung cells, slowly transforming them from healthy to cancerous.
The study found that this happened on a large scale in a smoker’s lungs even before they had cancer.
The vast majority of cells taken from a smoker’s airways had been mutated by tobacco, with cells containing up to 10,000 genetic alterations.
“These can be considered as mini time bombs, waiting for the next blow that will make them progress to cancer,” said Dr. Kate Gowers, one of the UCL researchers.
But a small proportion of cells came out unharmed.
It is not clear exactly how they avoid the genetic devastation caused by smoking, but the researchers said they seemed to “exist in a nuclear bunker.”
However, after someone quits smoking, it is these cells that grow and replace damaged cells in the lungs.
In people who quit smoking, up to 40% of their cells resembled those of people who had never smoked.
“We were not prepared for the find,” Dr. Peter Campbell of the Sanger Institute told the BBC.
He added: “There is a population of cells that, in some way, magically replenish the lining of the airways.
“One of the most notable things was that patients who had quit smoking, even after 40 years of smoking, had completely undamaged cell regeneration from exposure to tobacco.”
Motivation to quit smoking
Researchers still need to evaluate how much lungs are repaired. The study focused on the main airways instead of the small structures called alveoli, where oxygen crosses from the air we breathe into our lungs.
There are about 47,000 cases of lung cancer in the United Kingdom each year. Almost three quarters of them are caused by smoking.
Studies have already shown that people reduce their risk of lung cancer almost from the day they stop smoking.
This was supposed to be simply because other mutations caused by smoking were avoided.
Dr. Rachel Orritt of Cancer Research UK said: “It is a really motivating idea that people who quit smoking could reap the benefits twice as much, by preventing further tobacco-related damage to lung cells and by giving them the lungs the opportunity to balance some of the existing damage with healthier cells. “
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