An international team of researchers found several differences in the amount of altered DNA signatures in the tumors of smokers compared with those from non-smokers with the same type of cancer.
"Tobacco smoking leaves permanent mutations - it erodes the genetic material of most cells in your body", says Ludmil Alexandrov of Los Alamos National Laboratory in New Mexico, who led the analysis. "Even if you are just a social smoker who occasionally has one or two or five cigarettes, there is a cumulative effect."
The team compiled data on over 5000 human samples of 17 different cancers. The DNA was then searched for patterns of damage, known as "mutation signatures". One type of mutation, called "Signature 4", which indicates damage to Guanine, showed a far greater presence in tissues exposed to tobacco smoke. Signature 4 also strongly correlated with lung squamous cancer, lung adenocarcinoma and larynx cancers.
Strangely, signature 4 showed a significantly lesser correlation with oral, pharynx, and esophagus cancer, despite being just as exposed to tobacco smoke as the lungs and larynx. Researchers also were able to graph the relationship between quantity smoked and number of mutations. For instance, a pack a day for one year leads to 150 mutations in a lung cell, 97 in a larynx cell, 39 in the pharynx, 23 in the oral cavity, 18 in the bladder and 6 in the liver cell.
I take interest in the genetic or hereditary aspects of tobacco resistance. I have known individuals who have smoked a pack or so a day for numerous decades and never got lung cancer, and others who have smoked far less over a shorter period of time, yet fell ill with some respiratory related cancer.