Many smokers are switching to the seemingly healthier alternative, e-cigarettes. However, as a study now shows, they are nowhere near as harmless as assumed.
Modification of the genetic material: The consumption of e-cigarettes and snuff leads to similar changes to the DNA as classic cigarette smoking, as a study has now shown. These epigenetic changes in cells in the oral mucosa and elsewhere are similar in part to those of cancer cells and are therefore considered “procarcinogenic”. Smoking, vaping and sniffing could potentially cause cancer. Are they still recommended as a means of quitting smoking?
Study examines the consequences of e-cigarette consumption
Smoking has a whole range of negative health consequences. Cigarette consumption, for example, makes us age faster, promotes COPD and cancer and can sometimes be fatal. Although this has been known for a long time, the number of deaths caused by smoking continues to rise. In search of healthier alternatives to tobacco, smokers have been increasingly switching to e-cigarettes, which vaporize a liquid containing nicotine, in recent years.
Whether vaping actually causes less damage to our bodies than regular cigarettes is controversial. Although the e-cigarette seems to make it easier to quit smoking, some studies have shown that vaping changes the oral flora and can damage the gums. There is also evidence that vaping also leads to cancer-causing mutations in the DNA and inhibits the DNA repair systems.
A team led by Chiara Herzog from the University of Innsbruck has now researched for the first time what epigenetic effects classic tobacco and e-cigarettes have on the genome of different cells. In the epigenome, molecular attachments on the DNA such as methyl groups determine where and when which genes are read. However, these epigenetic appendages can change with aging and through contact with environmental toxins. As a result, the regulation of our genes also changes, which can potentially lead to mutations and cancer.
For their study, Herzog and her colleagues analyzed how smoking traditional and electronic cigarettes affects DNA methylation. The researchers examined cells that are directly exposed to smoke or steam – for example in the oral cavity – as well as cells that are only indirectly affected – for example in the cervix or in the immune system. In total, they evaluated more than 3,500 saliva and blood samples as well as swabs from the cervix and compared them with samples of cancer tissue.
DNA reveals tobacco consumption
The analyzes showed that smoking changed DNA methylation in all cells tested and at a total of 535 sites in the genome. The exact pattern differed depending on the cell type, but also affected cells that were only indirectly exposed to steam or smoke. Epithelial cells of various organs tended to be more susceptible to epigenetic changes than immune cells.
Some of these epigenetic changes also remained stable for years. Using the methylation rate in oral mucosa samples, Herzog and her colleagues were able to say with over 90 percent accuracy whether a person currently smokes or vapes, has done so in the past, or has never done so.
Similar epigenetic changes to those in smokers
The researchers also found that the cells of the oral mucosa in the test subjects sometimes had DNA methylations similar to those of cancer cells. “Changes that are observed in lung cancer tissue can also be detected in mouth cells of smokers that are not (yet) cancerous themselves,” says senior author Martin Widschwendter from the University of Innsbruck.
The scientists also observed such “procarcinogenic” epigenetic changes in the oral cells of people who consumed e-cigarettes or snus (snus). The samples also came from people who had not smoked traditional cigarettes before they started vaping.
“Based on our study, we cannot definitively say that e-cigarettes cause cancer. “But we observe that e-cigarette users have some similar epigenetic changes in cheek cells as smokers, and these changes are associated with the future development of lung cancer in smokers,” explains Herzog.
E-cigarettes “not as harmless as originally thought”
This suggests that the consumption of e-cigarettes and snus can also have longer-term health consequences. According to the researchers, vaping and sniffing are not healthy alternatives to classic cigarettes. “These new products may not be as harmless as originally thought,” emphasizes Widschwendter.
The researchers write that e-cigarettes and especially their long-term consequences need to be examined more closely before they are generally recommended for smoking cessation. Although vaping has been proven to help you quit cigarettes, vaping is not completely harmless. “We hope this study contributes to a broader discussion about why it is important to limit both tobacco and e-cigarette use – especially among people who have never smoked,” says Herzog.
However, experts not involved in the study do not see the results as a clear indication that electronic cigarettes are as harmful as regular cigarettes. They continue to recommend smokers switch to vaporizers. “Compared to cigarettes, e-cigarettes remain an essential tool for harm reduction,” says George Laking from the University of Auckland. However, non-smokers should not even start consuming tobacco.
In follow-up studies, Herzog and her colleagues now want to investigate how their results could be used to identify people at highest risk of cancer. The epigenetic changes in the mouth cells can provide evidence of existing cancer cells in the lungs. Analysis of DNA methylation in oral swabs could therefore potentially facilitate cancer diagnosis. (Cancer Research, 2024; doi: 10.1158/0008-5472.CAN-23-2957)
Source: University of Innsbruck, University College London
By Claudia Krapp