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Illustrative image showing a lung x-ray
HEALTH – How “hidden killer”air pollutants can cause lung cancer in non-smokers through a mechanism revealed 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 University College London.
Fine particles are found in vehicle exhaust, brake dust, or fossil fuel vapors. “hidden killer”Charles Swanton, from the Francis-Crick Institute, responsible for presenting this research, not yet peer-reviewed, told AFP at the annual congress of the European Society of Medical Oncology, which runs until September 13, in Paris.
If air pollution has been suspected for a long time, “We really didn’t know if or how this pollution directly caused lung cancer.”Professor Swanton explained.
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 biggest discovery is the mechanism by which these pollutants can trigger lung cancer in non-smokers.
Through laboratory studies in 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, which had never been 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 cause cancer. But when you expose a cell to contamination, it probably stimulates some kind 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 “pretty confusing”recognizes this medical director of Cancer Research UK, the main financier of the study.
Traditionally, it was thought that exposure to carcinogenic factors, such as those in cigarette smoke or pollution, caused genetic mutations in cells, turning them into tumors and proliferating.
For Suzette Delaloge, director of the cancer prevention program at the Gustave-Roussy Institute, “It is quite revolutionary because we had practically no proof before of this alternative carcinogenesis”.
“This study is a big step for science, and also for society, I hope”This oncologist, in charge of discussing the study at the congress, told AFP. “This opens a great door to knowledge but also to prevention”.
The next step will be “Understanding 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, several researchers insist.
“We have a choice 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.”Professor Swanton launched.
More than 90% of the world’s population is exposed to what the WHO considers to be excessive levels of fine particulate matter pollutants.
This research also gives hope for new prevention and treatment approaches. To detect and prevent, Suzette Delaloge is considering various avenues, but “not for tomorrow” : “personal assessment of our exposure to contaminants”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 and then treat them with drugs like interleukin-1 inhibitors? ».
Professor Swanton imagines “what could be the molecular prevention of cancer in the future, with a pill, maybe every day, to reduce the risk of cancer in high-risk areas”.
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