Category: Science

A new study has found no evidence that vapor from a commercially-available electronic cigarette promotes the development of cancer in laboratory cells, whereas smoke from a reference tobacco cigarette was found to be positive for cancer-promoting activity, even at very low concentrations.

“These results add to growing weight of evidence that e-cigarettes are likely to be significantly safer than conventional cigarettes,” said Damian Breheny, lead author and adverse outcome pathway manager at British American Tobacco.

Scientists at BAT used a test called the Bhas 42 assay to compare tobacco and nicotine products. The Bhas 42 cell transformation assay assesses the carcinogenic potential of chemicals by looking for changes in a line of cells that are characteristic of tumor development.

Bhas 42 was used to compare the tumor promoter activity of vapor from a Vype ePen, one of BAT’s commercially available electronic cigarettes, and smoke from a reference cigarette (3R4F), by exposing cells to the total particulate matter collected from the vapor or smoke.

Results showed that cigarette smoke was positive for cancer-promoting activity at concentrations as low as 6μg/mL, whereas the test electronic cigarette vapor was not observed to have any in vitro cancer promoter activity at concentrations up to 120μg/mL.

The Bhas 42 assay is part of a suite of in vitro tests being developed by BAT to compare the relative biological effects of electronic cigarettes and tobacco-heating products with those of traditional cigarettes.

“This is the first study to use the Bhas assay to compare tobacco and nicotine products, and it demonstrates the potential for its future application as part of a product assessment framework,” said Breheny.

Assessment of tobacco and nicotine products has traditionally involved genotoxicity tests, which evaluate initial DNA damage that can lead to cancer. Such tests indicate that electronic cigarette vapor, in contrast to cigarette smoke, does not cause mutations and DNA damage. Using the Bhas 42 assay allows for increased understanding of potential carcinogenic risk.

Previous research conducted by BAT has shown that Vype ePen vapor contains about 95 percent less toxicants – in terms of the nine harmful components the World Health Organization recommends should be reduced in cigarette smoke (Chem. Res. Toxicol, DOI: 10.1021/acs.chemrestox.6b00188) – than does cigarette smoke from a reference cigarette.

New research by British American Tobacco comparing the effects of cigarette smoke and electronic cigarette vapor has shown that, at equivalent or higher doses of nicotine, acute exposure to electronic cigarette vapor has very limited impact on gene expression when compared to the impact of cigarette smoke.

A BAT press note said that the human genome had tens of thousands of genes, and that the profile of genes that were switched on and off could be used to understand whether exposure to an aerosol had had a toxic effect.

‘Scientists at British American Tobacco used nicotine as a reference point and exposed MucilAir™, a realistic in vitro 3D model of a human airway, to e-cigarette vapor and cigarette smoke to assess their comparative effect on gene expression,’ the press note said.

‘The MucilAir™ human respiratory tissue was exposed to smoke from a reference cigarette (3R4F) or vapor from an e-cigarette (Vype ePen) continuously for an hour. Two doses of vapor were tested, matching or doubling the amount of nicotine reaching the cells compared to smoke. Then, to measure the cell response, the scientists mapped the genes that were switched on and off at 24 hours and 48 hours after the one-hour exposure.

‘In the tissue exposed to smoke, the scientists found 873 and 205 genes were affected after 24 and 48 hours of recovery, respectively. However, significantly fewer genes – only 3 and 1, respectively – were affected after exposure to e-cigarette vapour.’

Further analysis was said to have revealed that the exposure to cigarette smoke had caused changes in the expression of genes involved in the development of lung cancer, inflammation and fibrosis, while the test electronic cigarette vapor had caused only minor changes in genes known to be involved in cell metabolism and oxidative stress mechanisms.

“Our results clearly show that cigarette smoke has an adverse effect on cells, triggering a robust gene expression response,’ said Dr. James Murphy, head of reduced risk substantiation at BAT. “However,” he said, “even at equivalent or higher dose of nicotine, acute exposure to the test e-cigarette vapor has very limited impact on gene expression compared to cigarette smoke exposure – it’s a striking difference.”

These results, which were published in Scientific Reports (DOI: 10.1038/s41598-017-00852-y), were said to add to an increasing weight of evidence that electronic cigarette vapor caused less damage to cells than did cigarette smoke.

‘Previous research conducted by British American Tobacco has shown that Vype ePen vapor contains around 95 percent less toxicants (Chem. Res. Toxicol, DOI: 10.1021/acs.chemrestox.6b00188) compared to cigarette smoke from a reference cigarette (in terms of the priority list of nine toxicants which the World Health Organization recommends to reduce),’ the press note said.