Smoking a pack of cigarettes a day can cause damaging lung cell mutations, said a study published Thursday in the journal Science.
Researchers found that as many as 150 changes can happen to the lung cells of smokers each year because of cigarette use, Reuters reported. While the highest mutation rate was seen in lung cancer, smoking affected tumors in other parts of the body as well, including the bladder, liver and throat, the study said.
"Tobacco smoking increases the risk of at least 17 classes of human cancer," the study's abstract in Science said. "We analyzed somatic mutations and DNA methylation in 5,243 cancers of types for which tobacco smoking confers an elevated risk.
"Smoking is associated with increased mutation burdens of multiple distinct mutational signatures, which contribute to different extents in different cancers. One of these signatures, mainly found in cancers derived from tissues directly exposed to tobacco smoke, is attributable to misreplication of DNA damage caused by tobacco carcinogens," the abstract continued.
According to the Wellcome Trust Sanger Institute, which conducted the study with the Los Alamos National Laboratory and other collaborators, tobacco smoking claims the lives of at least six million people every year and could cause more than a billion deaths this century at current rates.
"Before now, we had a large body of epidemiological evidence linking smoking with cancer, but now we can actually observe and quantify the molecular changes in the DNA due to cigarette smoking," Ludmil Alexandrov, from Los Alamos National Laboratory and the lead author of the study said in a Sanger statement.
"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," he continued.
The study discovered that there are different mechanisms by which tobacco smoking causes the dangerous mutations, depending on the area of the body affected, the Sanger statement noted.
"The results are a mixture of the expected and unexpected, and reveal a picture of direct and indirect effects," David Phillips, professor of environmental carcinogenesis at King's College London and another author, said, according to the Sanger statement.
"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."
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