Nicotine chewing gum, lozenges and inhalers designed to help people to give up smoking may have the potential to cause cancer, find a team of British scientists.
The research team, led by Muy-Teck Teh, of Queen Mary, University of London, has found a link between mouth cancer and exposure to nicotine, which may indicate that using oral nicotine replacement therapies for long periods could contribute to a raised risk of the disease.
In the study, researchers found that the effects of a genetic mutation that is common in mouth cancer can be worsened by nicotine in the levels that are typically found in smoking cessation products.
The results raise the prospect that nicotine, the addictive chemical in tobacco, may be more carcinogenic than had previously been appreciated.
"Although we acknowledge the importance of encouraging people to quit smoking, our research suggests nicotine found in lozenges and chewing gums may increase the risk of mouth cancer," Times Online quoted Dr Teh as saying.
"Smoking is of course far more dangerous, and people who are using nicotine replacement to give up should continue to use it and consult their GPs if they are concerned. The important message is not to overuse it, and to follow advice on the packet," Dr. Teh added.
In the study, Dr. Teh's team investigated the role of a gene called FOXM1 in mouth cancer.
A mutation that raises the activity of this gene is commonly found in many tumors, and is also present in pre-cancerous cells in the mouth, the scientists found.
According to Dr. Teh, this raised expression can then be worsened by exposure to nicotine.
"If you already have a mouth lesion that is expressing high levels of FOXM1 and you expose it to nicotine, it may add to the risk of converting it into cancer. Neither the raised FOXM1 nor nicotine is alone sufficient to trigger cancer, but together they may have an effect," he said.
"The concern is that with smokers, you are looking at people who are already at risk of oral cancer. I'm worried that some may already have lesions they don't know about in the mouth, and if they keep on taking nicotine replacement when they stop smoking products they will not be doing themselves any good," he added.
The study is published in the journal Public Library of Science One.