ONE PACKED OF TABACCO PER DAY CAUSES 150 GANETIC MUTATIONS PER YEAR IN THE LUNGS

That tobacco kills is no longer new. That cancer is caused by mutations in the DNA was also already known. What was now found for the first time was a direct relationship between the number of cigarettes smoked and the number of mutations in the DNA.

If you smoke a pack of cigarettes per day, after a year, you will have caused 150 gene mutations in your lung cells on average, which increases the risk of cancer - concludes this week in the journal Science.

If there is a product consisting of toxic and irritating substances, it is a cigarette. In all, they have about 7000 chemicals, 70 of which are carcinogenic. In World Health Organization estimates, at least six million smokers die every year and by the end of this century more than 1 billion are expected to die.

A scientific research coordinated by the Los Alamos National Laboratory (United States) and the Sanger Institute (UK), in collaboration with researchers from Japan, South Korea, Italy and Belgium, identified some genetic mutations caused by exposure, both Direct as well as indirect, to tobacco smoke.

"Until now, we had a broad epidemiological body about the relationship between smoking and cancer. At the moment, we have also observed and quantified the molecular changes in DNA for cigarette smokers, "one study author, Ludmil Alexandrov, a Los Alamos researcher, said in a statement.

In all, the team sequenced the genome of 5243 cancers. Scientists were able to determine that among those who had those cancers, there were 2490 smokers and 1063 non-smokers, and these two groups were compared. So what are the differences in the cells of smokers and non-smokers? And the conclusion reached, using software to recognize patterns in genetic mutations, is that these mutations are higher in smokers. In a video, Ludmil Alexandrov explains the investigation.

The number of harmful mutations caused by tobacco is alarming, especially in lung cells, where scientists have counted the aforementioned 150 genetic alterations. "This number is extremely high and greatly increases the risk of developing lung cancer in smokers," says Ludmil Alexandrov to the PUBLIC.

A packet of tobacco per day is also responsible for genetic mutations in other organs at the end of a year, the study found: on average, 97 in the larynx, 39 in the pharynx, 23 in the mouth, 18 in the bladder, and six in the liver.

At present, tobacco is linked to 17 types of cancers. Throughout the study, more than 20 specific mutations associated with these 17 cancers were identified. These mutations are signatures left in the DNA by tobacco. However, only five of these mutations are very common in smokers.

One such genetic mutation, which scientists have designated as "signature 4", results from even direct exposure to tobacco smoke - that is, DNA damage is caused by carcinogenic substances contained in the cigarette, such as benzopyrene. "Signature 4 mutations are also detected in cancers of the oral cavity, pharynx and esophagus, although in a much smaller number than cancers of the lungs and larynx, perhaps due to a reduced exposure to tobacco smoke," reads In the scientific article.

Another mutation highlighted in the investigation is number 5. Previously discovered in another study, also in the National Laboratory of Los Alamos, this change is generally occurring in all cells of the body and with the known regularity of a clock. But the number 5 mutation is faster in smokers than in non-smokers, explains a statement from the Los Alamos National Laboratory.

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"The results are a mixture of expected and unexpected, and reveal a picture of the direct and indirect effects of tobacco. Mutations caused by direct DNA damage by tobacco carcinogens were observed mainly in organs in direct contact with inhaled smoke, "notes another study author, David Phillips of King's College London.

And who is "just" a social smoker? Smoking a cigarette or two from time to time also causes mutations in the DNA, Ludmil Alexandrov responds. "A simple cigarette can cause some - though very few - mutations," says the researcher. But the risk that the mutations caused by tobacco will result in cancer is lower. "Smoking 50 cigarettes over a lifetime results in an average mutation."

In addition to the relationship between tobacco and cancer, detected in terms of the genetic mutations that smoking causes, this type of study can be applied to uncover the genetics involved in other oncological risk factors such as obesity and eating. "It may be a contribution to the discovery of other causes of cancer," says Ludmil Alexandrov.

To have now the notion of the number of genetic mutations caused by tobacco can also be a weighty argument used in the prevention of smoking. For Charlie McMillan, director of the Los Alamos National Laboratory, this work "drives the use of pattern recognition software in genetic monitoring and represents a creative breakthrough in cancer research."

But tobacco was not always considered to be harmful. This plant came from America to Europe, brought in the time of the Discoveries. It came to be known as an extraordinary medicinal plant. Chewed or inhaled, it was not until the late 19th century that the use of tobacco in cigarettes expanded in Europe.

And if today there is no doubt about its harmful effects, the tobacco industry has not always assumed this reality, as recalled by the small publication book Cancer Ponto e Comma, published in 2015 by the Institute of Pathology and Molecular Immunology of the University of Porto (Ipatimup). "It has taken [tobacco industry] about 50 years to admit that tobacco consumption is harmful to health," reads the publication, which contains the illustration of a cigarette, which is the "autopsy of a killer".

SAISI