Just 15 Cigarettes May Alter DNA

By Liz Neporent from AOL Health

Think puffing on a cigarette every now and then wont hurt you? Think again. New research suggests that smoking just 15 cigarettes damages your DNA.

The large new study led by researchers from the Cancer Genome Project at the Wellcome Trust Sanger Institute in Britain identified more than 20,000 genetic mutations caused by tobacco toxins. This translates into roughly one mutation for every 15 cigarettes smoked, with each mutation ravaging the genetic code held within the DNA. Sometimes the bodys cells are able to make repairs and fend off cancer but often its a losing battle: When mutations grab hold of key genes, it leads to cancer.

"The profile of mutations we observed is exactly that expected from tobacco, suggesting that the majority of the 23,000 we found are caused by the cocktail of chemicals found in cigarettes, notes Peter Campbell, senior author of the work.

All cancers are the result of mutations, or mistakes in the genetic code, and frequently theyre caused by environmental factors such as tobacco toxins. In fact, smoking is considered the leading cause of preventable diseases. In this instance, no single mutation stood out as the lung cancer gene. Mutations ranged from simple swaps of a few letters in the genetic code to complex rearrangements of many thousands of letters. Most were a type known as passenger mutations that only appear to cause cancer when merged with other mutations.

The study was so comprehensive that the team could see signatures of an undiscovered system of DNA repair, reducing the mutations in highly active genes, suggesting the genome seeks to preserve these regions and sacrifice others. But the damage done by lighting up is passed onto every subsequent generation of daughter cells leaving a permanent record of the havoc wrecked. Like an archaeologist, we can begin to reconstruct the history of the cancer clone -- revealing a record of past exposure and accumulated damage in the genome," said Andy Futreal, Ph.D., another one of the investigators.

Still, if you kick the habit, there is a glimmer of hope. The Wellcome trust team suspects that over long periods of time lung cells are able to activate fresh stem cells that can clear away mutations and repair the damage. They say the risk of lung cancer falls to around normal some 15 years after a person quits smoking.