Some air pollutants look like a “hidden killer” as they can cause a number of lung cancers in non-smokers, through a mechanism explained by a study published on Saturday, September 10, 2022. 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 have shown that particulate matter (less than 2.5 microns, roughly equivalent to the diameter of a hair) that is considered a cause of climate change leads to cancerous changes in the cells of the respiratory system.
Fine particles found in exhaust gases, vehicle brake dust or fumes from fossil fuels can be likened to an “invisible killer,” Charles Swanton of the Francis Crick Institute, who presented the findings of the research, which has not yet been peer-reviewed, told AFP. During the annual conference of the European Society of Oncology, held in Paris until September 13.
Recalling that the harm of air pollution has been known for a long time, Professor Swanton pointed out that scientists were not “sure whether or how this pollution directly causes lung cancer.”
The researchers first studied data on more than 460,000 people from England, South Korea and Taiwan, and based on them showed an association between exposure to increased concentrations of fine particulate matter and an increased risk of lung cancer.
However, the most important discovery is the understanding of the mechanism through which these pollutants cause lung cancer in non-smokers.
The researchers demonstrated through laboratory studies on mice that the particles induced changes in two genes, the epidermal growth factor receptor (EGFR) and KRAS, which are already 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 on their own to lead to cancer. But when a cell is exposed to contamination, it is likely to trigger some kind of” inflammatory reaction. He added that “the cell will lead to the emergence of cancer” if “it harbors a mutation.”
Swanton, who heads the main funder of the study, the “Cancer Research UK” center for cancer research, said that this study is “deciphering the biological mechanism of what was a mystery.”
It was believed that exposure to cancer-causing factors, such as those resulting from cigarette smoke or pollution, causes genetic mutations in cells, which makes them tumors and leads to their proliferation.
Suzette Delaloge, director of the Cancer Prevention Program at the Institut Gustave Rossi, said the study’s findings were a “revolutionary development” since “there was no evidence of this alternative carcinogenesis before.”
This oncology specialist, who was assigned to discuss the study during the conference, stressed that it is an “important step for science,” hoping that it will be “for society as well,” and considered that it “opens a wide door for knowledge, but also for prevention.”
Prof Swanton said the next step was to “understand why some altered lung cells turn cancerous after exposure to pollutants”.
A number of researchers highlighted that this study confirms that reducing air pollution is also important for health.
Professor Swanton said: “We have a choice whether we smoke or not, but we can’t choose the air we breathe. It is therefore a global problem given that more people are five times more likely to be exposed to unhealthy levels of pollution than are 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 pollutants.
This research also offers hope for new methods of prevention and treatment.
Suzette Delalog indicated that it is possible to work on several methods of detection and prevention, but not in the short term, including the “personal assessment of exposure to pollutants”, and the detection – which is not yet possible – of the EGFR gene mutation, and so on.
As for Tony Mok of the University of Hong Kong, he was quoted in a statement by the European Society of Oncology as saying that this research is “as interesting as it is promising,” and considered that it allows “to think one day about searching for precancerous lesions in the lungs using medical imaging techniques, and then trying treated with medications such as interleukin-1 beta inhibitors.
Professor Swanton did not rule out the future of “molecular cancer prevention by means of pills, perhaps at the rate of one every day, to reduce the risk of cancer in high-risk areas.”