Vaping cancer claims challenged by limits of laboratory study

Recent headlines have suggested that vaping causes cancer. They are based partly on a study that examined how a molecule called VALT1 behaves in lung cells.

The study found that VALT1 levels increased after cells were exposed to an extract made from vaping aerosol. The researchers then changed the amount of VALT1 in the cells to see what happened.

They found several changes linked to cancer-like behaviour. These included faster cell growth, increased movement, changes in the cells’ structure and greater resistance to programmed cell death.

The findings are worth investigating. However, the study does not show that people who vape develop cancer.

What did the study test?

Researchers from the University of the Philippines Diliman used two types of lung cell in their experiments.

One was A549, a cell line taken from a lung cancer. The other was BEAS-2B, an immortalised human bronchial cell line used as a laboratory model of non-cancerous lung cells.

The researchers exposed the cells to an extract made from a strawberry cheesecake-flavoured vaping product containing 0.6mg of nicotine per millilitre. The device was used at 22 watts.

They measured the amount of VALT1 in the cells and looked at how the cells behaved.

In the cancer cell line, the vaping extract was linked to faster growth, changes in the cells’ response to oxidative stress and greater resistance to cell death. The cells also moved more quickly across a gap in a layer of cells, an experiment used to measure cell movement.

The researchers then increased VALT1 levels artificially. Some of the same changes appeared even when the cells were not exposed to the vaping extract.

When the researchers reduced VALT1, several of the changes became weaker.

The study’s abstract says the findings “support an active role for VALT1 as an e-cigarette vapor-upregulated transcript” and that the molecule “enhances cellular survival under extracellular chemical stress”.

This means the researchers found a possible biological process that may be relevant to cancer research. It does not mean that the cells became cancerous, or that vaping has been shown to cause cancer in people.

Why the findings have been overstated

Laboratory experiments can reveal how cells respond under controlled conditions, but they can’t tell us how likely a disease is to develop in people using a product over many years.

This study did not follow people who vape over many years. It did not compare cancer rates among vapers, smokers and people who use neither product. It did not test whether the changes seen in the cells eventually produced tumours.

The researchers also did not compare vaping with smoking. That’s an important omission when considering the likely health impact for adult smokers who switch from cigarettes to vaping.

The experiment used one vape liquid, one flavour and one device setting. Vaping products differ widely in their ingredients, design, temperature and power.

The researchers acknowledged this limitation in the paper.

“Given the heterogeneity of e-cigarette formulations and the lack of complete chemical characterization of the utilized eCSE formulation, the extent to which these findings can be extrapolated to e-cigarette use more broadly is limited,” they wrote.

The vaping extract was also prepared under laboratory conditions. It may not represent the aerosol produced by every device or the way every person vapes.

The experiment examined cells over a short period, and cancer usually develops through a complicated series of changes over a much longer time.

A cell that grows more quickly or survives for longer may display a feature associated with cancer. That does not prove it will form a tumour in the body.

What does the wider evidence show?

The Office for Health Improvement and Disparities has reviewed the evidence on vaping and cancer.

Its 2022 evidence update said that laboratory and animal studies were difficult to apply directly to people because they often used short-term or highly concentrated exposures.

The review also found that vaping generally exposed people to lower levels of many of the cancer-causing chemicals found in tobacco smoke.

Levels of several tobacco-specific nitrosamines were substantially lower among vapers than smokers. These chemicals are linked to cancer and are found in tobacco smoke.

OHID said this did not mean vaping was risk-free. People who have never smoked should not be encouraged to take up vaping.

However, it concluded that helping people who smoke to switch completely to vaping could reduce their exposure to toxicants and carcinogens.

That context matters when new laboratory research is reported. A study can identify a possible warning signal without showing how large the risk is in real life.

It can also highlight questions for future research, such as whether different vaping products have different effects, whether any changes last over time and how vaping compares with smoking.

A reason for further research, not proof of cancer

The study’s authors described their findings as “preliminary data linking e-cigarette exposure to lncRNA-mediated tumorigenic phenotypes”.

In simple terms, they found that vaping extract and changes in VALT1 were linked to cell behaviours that can also be seen in tumour cells.

They described VALT1 as a molecule that needs further investigation. That is a reasonable conclusion from a laboratory study.

The research raises questions about how different vaping aerosols may affect cells. It does not justify reporting the findings as proof that vaping causes cancer.

People who don’t smoke face the lowest risk by avoiding both smoking and vaping. For adults who smoke, completely switching away from combustible tobacco remains important because the smoke from burning tobacco contains many of the chemicals responsible for smoking-related cancer.

The clearest message from this study is that vaping needs continued research, while cancer claims need to match what the research actually tested.