Researchers sought to measure genetic damage influenced by smoking tobacco in different body organs and found that smoking a pack a day for a year causes 150 mutations in lung cells.
A minimum of 6 million people die every year because of smoking. If current trends keep up, the World Health Organization is predicting that more than a billion deaths related to tobacco will occur within the century. At least 17 types of cancer have been associated with smoking but no one has identified the underlying mechanism influenced by smoking that leads to these cancers.
In a study published in the journal Science, researchers were able to directly link the number of mutations in tumor DNA with the number of cigarettes smoked in a lifetime. The highest rate of mutations were observed in lung cancer cases but those tumors that developed in other body parts also had mutations associated with smoking, which explained how smoking tobacco leads to many cancer types.
DNA Mutations From Smoking
For the first comprehensive look at DNA in cancers associated with smoking, researchers examined more than 5,000 tumors, comparing samples from both smokers and non-smokers. They found mutational signatures within the DNA of smokers and counted the number of these specific mutations in different tumors.
Aside from the 150 mutations in lung cells, there were also an estimated average of 97 in larynx cells, 23 in mouth cells, 39 in larynx cells, six in liver cells and 18 in bladder cells for every year that a pack of cigarettes is smoked every day.
According to David Phillips, one of the authors of the study, their findings were a mix of expected and unexpected results, which provided an idea of how smoking directly and indirectly affects the body. While DNA damage due to carcinogen exposure from tobacco was mainly evident in organs coming into direct contact with smoke, it would also appear that tobacco smoking affects key mechanisms as well in other cells in the body that cause DNA mutation.
The Link Between Smoking And Cancer
At least five smoking-related processes leading to DNA damage were revealed by the study, the most prevalent of which is a mutational signature that is present in all cancer types. According to the researchers, smoking tobacco promotes DNA damage by speeding up the cellular clock responsible for genetic mutations.
"Our research indicates that the way tobacco smoking causes cancer is more complex than we thought," said Mike Stratton, lead author for the study, adding that looking into cancer DNA was an effective way to get clues on how the disease develops, which then helps in crafting more effective prevention and treatment methods in the fight against cancer.