As a “hidden killer”, air pollutants can cause lung cancer in non-smokers through a mechanism revealed in a study on Saturday, marking a “significant step for science and society”, according to experts.
Already involved in climate change, fine particles (less than 2.5 microns, about the diameter of a hair) are responsible for cancerous changes in the cells of the respiratory tract, according to scientists from the Francis-Crick Institute and University College London.
Fine particles, found in car exhaust, vehicle brake dust or fossil fuel vapors, are “a hidden killer,” said Charles Swanton of the Francis-Crick Institute, which is responsible for present the research, not yet peer-reviewed, at the annual congress of the European Society for Medical Oncology, which runs until September 13, in Paris.
While air pollution has long been suspected, “we weren’t sure whether or how this pollution was directly causing lung cancer,” Professor Swanton said.
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.
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.
“A Riddle”
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 probably aren’t enough to cause cancer. But when you expose a cell to contamination, it probably stimulates some sort of ‘inflammatory’ reaction, and if ‘the cell harbors a mutation, it will form cancer,'” he summarizes. Professor Swanton.
It is a “deciphering of the biological mechanism of what was an enigma” but “quite confusing”, admits 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.
An important step “for science and for society”
For Suzette Delaloge, director of the cancer prevention program at the Gustave-Roussy Institute, “it is quite revolutionary because we had practically no prior demonstration of this alternative carcinogenesis.”
“This study is a very important step for science, and also for society, I hope,” said the oncologist, responsible for discussing the study at the congress. This opens a great door to knowledge but also to prevention”.
The next step will be “to understand why certain altered lung cells become cancerous after exposure to pollutants”, according to Professor Swanton. This study confirms that reducing air pollution is also crucial for health, several researchers insist.
“We have a choice whether or not to smoke, 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,” said Professor Swanton.
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 considers several ways but “not for tomorrow”: “personal evaluation 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”, “allows us to consider one day looking for precancerous lesions in the lungs using images and then trying to treat them with drugs such as interleukin-1 inhibitors?
Professor Swanton envisions “what molecular cancer prevention might look like in the future, with a pill, perhaps every day, to reduce cancer risk in high-risk areas.”
Source: BFM TV
