Smoking 'causes hundreds of genetic mutations'

8th November 2016 – Scientists say they've been able to measure the damage to our genes caused by smoking.

The US study in the journal Science found that on average someone who smokes one packet of cigarettes a day can accumulate 150 extra mutations in every lung cell each year.

Mutations were also measured in other parts of the body.

A global killer

Each year, smoking kills around 6 million people worldwide and 96,000 in the UK.

Researchers first linked smoking tobacco with lung cancer in the 1950s. Today smoking is linked to at least 17 types of cancer, including pancreatic, oesophageal and bladder cancers.

The harm from smoking is down to the large number of toxic chemicals in cigarettes which are first inhaled into the lungs and which then spread around the body.

Although the link between tobacco smoke and cancer has been known for years, a team led by the Wellcome Trust Sanger Institute say they have gained an insight into how smoking causes the disease.

The mechanism of disease

Cancer is caused when DNA in cells mutates, or changes its structure. This can lead to an increase in the rate of cell division or a loss of normal function. The scientists analysed 5,243 tumours and looked for differences in DNA between those of smokers and non-smokers.

They found the highest mutation rates in the lungs of smokers. However, other organs also contained these smoking-associated mutations, which they say could explain how smoking causes many types of human cancer in places not directly exposed to the tobacco smoke.
 

In a statement, co-author Professor David Phillips, a cancer expert at King’s College London, explains: "The results are a mixture of the expected and unexpected, and reveal a picture of direct and indirect effects.

"Mutations caused by direct DNA damage from carcinogens in tobacco were seen mainly in organs that come into direct contact with inhaled smoke. In contrast, other cells of the body suffered only indirect damage, as tobacco smoking seems to affect key mechanisms in these cells that in turn mutate DNA."

Mutations throughout the body

Another author, Ludmil Alexandrov, from Los Alamos National Laboratory, says: "With this study, we have found that people who smoke a pack a day develop an average of 150 extra mutations in their lungs every year, which explains why smokers have such a higher risk of developing lung cancer."

The scientists also estimate that a pack a cigarettes a day for a year led to an average 97 mutations in each cell in the larynx, 39 mutations for the pharynx, 23 mutations for the mouth, 18 mutations for the bladder, and 6 mutations in every cell of the liver each year.