Smoking's Devastating Mutation Toll

DNA mapping has revealed that smokers that consume a pack of 20 cigarettes a day trigger an extra 150 mutations per year, in each lung cell

It's clear now how detrimental cigarettes are for one's health, but until now the precise mutation toll of regular smoking has not been definitively mapped. Now a new study published in Science has laid out a clear link between the quantity of consumption and the number of mutations occurring as a consequence. 

Unravelling the link between smoking and disease

Smoking is linked to the deaths of 6 million people every year and is associated with 17 types of cancer. A number of chemical agents in cigarettes and tobacco smoke are known mutagens, and in a novel comprehensive scan of over 5000 tumours researchers have identified the extent of DNA damage caused by regular smoking. The major finding of the research was that smoking a pack a day on average equals 150 new mutations in every lung cell per year - a significant burden. 

"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. 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"

Credit: Genome Research Limited

An effect on multiple organs

While the highest collateral damage was found in lung cells, a pack a day also led to significant rises in mutation rates in a number of other tissues too: 97 mutations per cell in the larynx, 39 in the pharynx, 23 per cell in the mouth, 18 mutations per cell in the bladder, and 6 mutations in every cell of the liver each year. This new analysis explains how smoking is tied to increased cancer rates across the body, through both direct and indirect influences on DNA integrity. Direct exposure to the smoke led to higher mutation rates, but there also appeared to be a larger organism wide response through other mechanisms. All in all the research lays out 5 distinct ways that smoking caused DNA damage.

"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"

Read more at MedicalXpress