NOV 10, 2016 11:36 AM PST

Scientists Quantify Smoking Damage in Cancer Genomes

WRITTEN BY: Xuan Pham

Scientists from the Los Alamos National Laboratory hope to squash any preconceived notions that the occasional cigarette is harmless. In their new study, the researchers finally quantified the amount of DNA damage caused by smoking, cigarette per cigarette - and the results are sombering.

Smoking and DNA mutations, the exact numbers are in | Image: pixabay.com
They found that a new mutation appears for every 50 cigarettes smoked. While that number seems innocent, think about how fast people smoke through a single cigarette before needing to light up another. Over the course of a year, a one-pack-a-day smoker can rack up as much as 150 mutations per lung cell alone. Mutations also pile on in other tissues exposed to the cigarette – the team estimated 97 mutations per larynx cell, 23 mutations per mouth cell, 18 mutations per bladder cell, and 6 mutations per liver cell.
           
Furthermore, cellular mutations can compound upon one another. This means a mutation that activates a cancer-promoting gene may influence mutations of other cancer genes. And if these mutations are maintained through cell division, it’s not hard to imagine an environment ripe for cancer to grow.
           
“Smoking is like playing Russian roulette: the more you play, the higher the chance the mutations will hit the right genes and you will develop cancer,” said Ludmil Alexandrov, the study’s co-lead author. “However, there will always be people who smoke a lot but the mutations do not hit the right genes.”
 


These results follow suit with a slew of recent evidence to highlight the molecular danger of smoking. Most recently, another study found that DNA damages caused by smoking can linger in a person’s genome for over 30 years, even after quitting. Taken together, we can conclude from the two studies that for every 50 cigarettes smoked, the genome acquires a new DNA mutation that may persist for decades in our body.
 
This isn’t to say that there’s no hope for smokers. In fact, it’s quite the opposite. The researchers hope that putting a concrete number for DNA damages associated with cigarettes will help smokers reduce and even quit their habit.
 
“Many smokers believe there’s no point in quitting because the damage is already done,” said Simon Chapman, Emeritus Professor in the School of Public Health at the University of Sydney, Australia. “But if smokers quit by middle age, they can avoid nearly all the excess risk of tobacco-caused deaths.” It’s estimated that a 40-year-old smoker could potentially live 9 years longer after having quit smoking as compare to continued smoking.

Additional sources: New Scientist, Los Alamos National Laboratory via EurekAlert!

About the Author
I am a human geneticist, passionate about telling stories to make science more engaging and approachable. Find more of my writing at the Hopkins BioMedical Odyssey blog and at TheGeneTwist.com.
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