Understanding of lung cancer takes a major step forward with this study

warodom changyencham/Getty Images Asian female doctors speculate on X-ray images from virus corona-infected lung patients.

warodom changyencham/Getty Images

Illustrative image showing a lung x-ray

HEALTH – As “hidden killer”air pollutants can cause lung cancer in non-smokers via a mechanism unveiled this Saturday, September 10 in a study, which marks a “not important for science – and society” according to experts.

Already implicated in climate change, fine particles – less than 2.5 microns, about the diameter of a hair – are responsible for cancerous changes in cells of the respiratory tract, according to scientists from the Francis-Crick Institute and from University College London.

Found in vehicle exhaust, brake dust or fossil fuel fumes, fine particles are “hidden killer”told AFP Charles Swanton of the Francis-Crick Institute, responsible for presenting this research, not yet peer-reviewed, at the annual congress of the European Society for Medical Oncology, which takes place until 13 September, in Paris.

If air pollution has long been suspected, “We didn’t really know if this pollution directly caused lung cancer, or how”explained Professor Swanton.

The researchers first explored data from more than 460,000 residents of England, South Korea and Taiwan, and showed that exposure to increasing concentrations of fine particles was linked to an increased risk of lung cancer.

When and how does lung cancer start?

The major discovery is that of the mechanism by which these pollutants can trigger lung cancer in non-smokers.

Through laboratory studies on mice, the researchers showed that the particles caused changes in two genes (EGFR and KRAS), already linked to lung cancer.

They then analyzed nearly 250 samples of healthy human lung tissue, never exposed to carcinogens from tobacco or heavy pollution. Mutations in the EGFR gene appeared in 18% of the samples, alterations in KRAS in 33%.

“On their own, these mutations are probably not enough to lead to cancer. But when you expose a cell to pollution, it probably stimulates some sort of reaction.” inflammatory, and if “the cell harbors a mutation, it will form a cancer”sums up Professor Swanton.

It’s a “deciphering the biological mechanism of what was an enigma” but “quite confusing”recognizes this chief medical officer of Cancer Research UK, the main funder of the study.

Traditionally, it was thought that exposure to carcinogenic factors, such as those from cigarette smoke or pollution, caused genetic mutations in cells, making them tumorous and causing them to proliferate.

For Suzette Delaloge, director of the cancer prevention program at the Gustave-Roussy Institute, “It’s quite revolutionary because we had practically no demonstration before of this alternative carcinogenesis”.

“This study is a pretty big step for science – and for society too, I hope”told AFP this oncologist, responsible for discussing the study at the congress. “This opens a great door for knowledge but also for prevention”.

The next step will be to “understand why certain altered lung cells become cancerous after exposure to pollutants”according to Professor Swanton.

Air pollution affects everyone

This study confirms that reducing air pollution is also crucial for health, insist several researchers.

“We have the choice whether to smoke or not, but not the air we breathe. As probably five times more people are exposed to unhealthy levels of pollution than tobacco, this is a major global problem.”launched Professor Swanton.

More than 90% of the world’s population is exposed to what the WHO considers to be excessive levels of fine particulate pollutants.

This research also gives hope for new approaches to prevention and treatment. To detect and prevent, Suzette Delaloge is considering several avenues but “not for tomorrow” : “personal assessment of our exposure to pollutants”detection – not yet possible – of the EGFR genetic mutation, etc.

For Tony Mok, from the University of Hong Kong, quoted in an ESMO press release, this research, “as intriguing as it is promising”, “make it possible to one day look for precancerous lesions in the lungs using imaging, then try to treat them with drugs like interleukin-1 inhibitors? ».

Professor Swanton imagines “what molecular cancer prevention could be in the future, with a pill, maybe every day, to reduce the risk of cancer in high-risk areas”.

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