Scientists find new link between tobacco chemical and cancer

In collaboration with the Press Association

Scientists have found a second, indirect way in which cancer-causing chemicals in cigarettes cause lung cancer.

Previous research has shown that chemicals called polycyclic aromatic hydrocarbons (PAHs) damage DNA by binding to it and causing mutations.

Now, researchers at the University of Pennsylvania School of Medicine's Centre of Excellence in Environmental Toxicology (CEET) have found that PAHs can also lead to mutations in critical genes important to lung cancer via a process called oxidative stress, in which destructive molecules called free radicals accumulate and cause cell death.

The findings are published in the Proceedings of the National Academy of Sciences and provide the first demonstration of this link, according to co-author Dr Ian Blair, a professor in the university's department of pharmacology.

"This is a second, but indirect way in which PAHs can cause cancer. We also know that PAHs can also cause cancer directly," he noted.

Senior author Dr Trevor Penning, director of CEET, explained that enzymes called AKRs, which transform PAHs to produce oxygen free radicals, are over-expressed in lung cancer cells.

"Our study also shows that those same enzymes are responsible for the oxidative stress from PAHs in the human lung cells we used in our experiments," he revealed.

"Because this study relates AKR over-expression to oxidative damage of DNA with lung cancer, it makes you wonder if the ten per cent of smokers that are most prone to lung cancer have either dysregulated AKR expression or genetic differences in their AKRs that predispose them to disease," he theorised.

"These findings go beyond the first step of DNA damage and may provide a reason why disease progresses," he added.