The last few years have seen a nearly 10-fold increase in electronic cigarette (e-cig) use, or "vaping," particularly among adult smokers and among adolescents who have never smoked a cigarette. E-cigs are frequently touted as a safer alternative to traditional cigarettes, but new research done at the University of Southern California (USC) reveals that vaping produces some of the same cancer-causing molecular changes to oral tissue that are produced by cigarette smoking.
"The existing data show that e-cig vapor is not merely 'water vapor' as some people believe," remarked Ahmad Besaratinia, PhD, Associate Professor at USC's Keck School of Medicine and senior author of the study, which was published in the International Journal of Molecular Sciences. "Although the concentrations of most carcinogenic compounds in e-cig products are much lower than those in cigarette smoke, there is no safe level of exposure to carcinogens."
The researchers investigated the regulation of genes and associated molecular pathways in the entire genome of oral cells of e-cig users (vapers) and cigarette smokers as compared to non-smokers. RNA-sequencing analysis of the oral transcriptome revealed a significantly higher number of aberrantly expressed transcripts in both vapers and smokers compared with non-smokers. The effect was worse for smokers, however, who had around 50% more differentially expressed transcripts than did vapers.
There was also a difference between smokers and vapers in the type of deregulated transcripts: smokers had more deregulated transcripts in protein-coding genes (79% of the deregulated transcripts for smokers vs 53% for vapers), while in vapers, more of the aberrantly expressed transcripts were from regulatory non-coding RNAs (28% for vapers vs 8% for smokers). Of the genes that were deregulated in vapers, 26% were identical to those found in smokers. Analyses of molecular pathways and functional networks showed that cancer was the top disease associated with the deregulated genes in both vapers (62%) and smokers (79%). Some of the deregulated genes found in vapers but not in smokers were associated with lung cancer, esophageal cancer, leukemia, bladder cancer, and ovarian cancer.
Next, the researchers intend to replicate their results in a larger group of subjects and explore the mechanisms behind gene deregulation. In addition, Dr. Besaratinia is launching an investigation concerning whether switching from smoking to vaping causes any changes in gene regulation.
For More Information
Tommasi S, Caliri AW, Caceres A, et al (2019). Deregulation of biologically significant genes and associated molecular pathways in the oral epithelium of electronic cigarette users. Int J Mol Sci, 20(3):738. DOI:10.3390/ijms20030738