E-cigarette users with a limited smoking history experience similar DNA changes to specific cheek cells as smokers, a new study led by researchers at UCL and University of Innsbruck have found.

Although the study does not show that e-cigarettes cause cancer, long-term follow-up is important to assess whether they have harmful effects and, if so, what they are, the scientists said.  

The paper, published in Cancer Research, analysed the epigenetic effects of tobacco and e-cigarettes on DNA methylation in over 3,500 samples, to investigate the impact on cells that are directly exposed to tobacco (e.g. in the mouth) and those that are not directly exposed (e.g. in blood or cervical cells).

The researchers found that epithelial cells in the mouth showed substantial epigenomic changes in smokers. Importantly, these changes were further elevated in lung cancers or pre-cancers when compared to the normal lung tissue.

However, the publication also includes new data showing that similar epigenomic changes were observed in the cells of e-cigarette users who had smoked fewer than 100 tobacco cigarettes in their lives.

First study of its kind

Dr Chiara Herzog from UCL EGA Institute for Women’s Health and University of Innsbruck said the study was the first to investigate the impact of smoking and vaping on different kinds of cells, rather than blood only.

“We cannot say that e-cigarettes cause cancer based on our study, but we do observe e-cigarette users exhibit some similar epigenetic changes in buccal cells as smokers, and these changes are associated with future lung cancer development in smokers,” she said.

“While the scientific consensus is that e-cigarettes are safer than smoking tobacco, we cannot assume they are completely safe to use and it is important to explore their potential long-term risks and links to cancer. We hope this study may help form part of a wider discussion into e-cigarette usage – especially in people who have never previously smoked tobacco,” Dr Herzog said.

The NHS says e-cigarettes are substantially safer than smoking tobacco and smokers are recommended to switch to vaping to improve their health.

More research needed

The researchers hope to further investigate how epigenetic changes related to smoking in cheek swabs could be used for identifying individuals at highest risk of developing cancer and assess the long-term health risks of e-cigarettes. 

Dr Ian Walker, Cancer Research UK’s executive director of policy, emphasied that the study does not show that e-cigarettes cause cancer. “This paper does however highlight that e-cigarettes are not risk-free, and so we need additional studies to uncover their potential longer-term impacts on human health,” he added.