Researchers uncover role of air pollution in causing some lung cancers

Some air pollutants appear to be a “hidden killer” in that they can cause a range of lung cancers in non-smokers, through a mechanism explained by a study published Saturday, and understanding them is an “important step.” for science and society. ”, according to a group of experts.

Scientists from the Francis Crick Institute and University College London explained that fine particles (less than 2.5 microns, approximately equivalent to the diameter of a hair), considered among the causes of climate change, cause cancerous changes in the cells of the respiratory system.

Fine particles in exhaust gases, brake dust or fossil fuel fumes can be compared to a “hidden killer”, according to Charles Swanton of the Francis Crick Institute, who presented the results of this research, which has not yet been published. has been reviewed by other researchers. During the annual conference of the European Society for Medical Oncology, held in Paris on September 13.

While Professor Swanton stated that the harm of air pollution has long been known, he noted that scientists “were not sure whether this pollution directly causes lung cancer, or how this happens.”

First, the researchers studied data from more than 460,000 people from England, South Korea, and Taiwan, and based on this they showed an association between exposure to higher concentrations of fine particles and an increased risk of lung cancer.

However, the most remarkable discovery is the understanding of the mechanism by which these pollutants cause lung cancer in non-smokers.

The researchers demonstrated, through laboratory studies in mice, that the particles caused changes in two genes, namely the epidermal growth factor receptor (EGFR) and Keras (KRAS), which are originally linked to lung cancer. .

The researchers then analyzed about 250 samples of healthy human lung tissue that had never been exposed to carcinogens from tobacco or heavy pollution. Mutations in the EGFR gene appeared in 18 percent of the samples and changes in KRAS in 33 percent of them.

Professor Swanton said: “These mutations may not be sufficient in themselves to cause cancer.” But when the cell is exposed to contamination, it is likely to stimulate an inflammatory reaction. He added that “the cell will give rise to cancer” if it “has a mutation.”

Swanton, who heads the study’s main sponsor, Cancer Research UK, said this study is “a decoding of the biological mechanism of what has been a mystery.”

Exposure to cancer-causing factors, such as those resulting from cigarette smoke or pollution, was believed to cause genetic mutations in cells, turning them into tumors and causing them to proliferate.

The director of the Cancer Prevention Program at the Gustave Rossi Sozette Delalog Institute called the study’s findings a “revolutionary development” as “there was no previous evidence of this alternative carcinogenesis.”

This oncologist, in charge of commenting on the study during the day, stressed that it is an “important step for science”, hoping that it will be “also for society”, and considered that “it opens a wide door to knowledge”. , but also for prevention.”

Professor Swanton said the next step would be to “understand why some of the altered lung cells become cancerous after exposure to pollutants.”

Several researchers highlighted that this study confirms that reducing air pollution is also important for health.

Professor Swanton said: “We can choose whether or not to smoke, but we can’t choose the air we breathe. So it’s a global problem given that the number of people exposed to harmful levels of pollution is five times more likely than people exposed to smoke from tobacco products.

More than 90 percent of the world’s population is exposed to what the World Health Organization describes as excessive levels of particulate matter.

This research also provides hope for new prevention and treatment methods.

Suzette Delalog indicated the possibility of working on various methods of detection and prevention, but not in the short term, including “personal evaluation of exposure to pollutants”, the detection – not yet possible – of the EGFR genetic mutation, etc.

As for Tony Mok of the University of Hong Kong, a statement from the European Society for Medical Oncology quoted him as saying that this research is “as interesting as it is promising”, and believes that it allows “one day to think about looking for precancerous lesions in the lungs.” using medical imaging techniques, and then try to treat them with drugs like interleukin-1 beta inhibitors.”

Professor Swanton did not rule out finding “molecular cancer prevention with pills, perhaps one a day, to reduce cancer risk in high-risk areas” in the future.