Scientists say they have identified the mechanism by which air pollution causes lung cancer in non-smokers, a discovery hailed by one expert as “an important step for science – and for the society”.
The study illustrated the health risk created by small particles from burning fossil fuels, sparking calls for more urgent action to combat climate change.
It could also pave the way for a new field of cancer prevention, according to Charles Swanton of the UK’s Francis Crick Institute.
Swanton presented the study, which has not yet been published in a peer-reviewed journal, at the annual conference of the European Society of Medical Oncology in Paris on Saturday.
Air pollution has long been linked to a higher risk of lung cancer in people who have never smoked.
“But we don’t really know if pollution directly causes lung cancer – or how,” Swanton told AFP news agency.
Traditionally, it was thought that exposure to carcinogens, such as in cigarette smoke or pollution, causes DNA mutations that then become cancerous.
But there’s an “inconvenient truth” to this model, Swanton says: previous research has shown that DNA mutations can occur without causing cancer — and most environmental carcinogens do not. cause mutations.
His research suggests a different model.
A future cancer pill?
The team from the Francis Crick Institute and University College London analyzed the health data of more than 460,000 people in the UK, South Korea and Taiwan.
They found that exposure to microscopic PM2.5 pollution particles – less than 2.5 micrometers (microns) in size – led to an increased risk of mutations in the epidermal growth factor receptor (EGFR) gene. ).
In laboratory studies in mice, the team showed that the particles cause changes in the EGFR gene as well as in the Kirsten mouse sarcoma virus (KRAS) gene, both of which are associated with cancer. lung.
To that end, they analyzed nearly 250 samples of human lung tissue that had never been exposed to carcinogens by smoking or heavy pollution.
Despite the healthy lungs, they found DNA mutations in 18 percent of the EGFR gene and 33 percent of the KRAS gene.
“They just sit there,” Swanton said, adding that the mutations seem to increase with age.
“On their own, they are probably not enough to reverse cancer,” he said.
But when a cell is exposed to pollution, it can trigger a “healing response” that causes inflammation, Swanton said.
And if that cell “contains a mutation, then it will form cancer,” he added.
“We have provided a biological mechanism behind what was previously a mystery,” he said.
In another experiment in mice, the researchers showed that an antibody can block a mediator – called interleukin 1 beta – from causing inflammation, stopping cancer from starting in the first place.
Swanton said he hopes the finding will “provide an effective basis for a future of what could be molecular cancer prevention, where we can give people a pill, perhaps every day, to reduce the risk of cancer”.
‘Revolution’
Suzette Delaloge, head of the cancer prevention program at France’s Gustave Roussy Institute, said the study was “quite revolutionary, because we have practically no proof of this alternative way of cancer formation. “.
“This research is quite an important step forward for science – and for society as well,” she told AFP.
Delaloge, who was not involved in the study but discussed it at Saturday’s conference, said: “This opens a huge door, both in terms of knowledge but also in new ways to prevent prevent” cancer from developing.
“This level of protest forces the authorities to act on an international scale.”
Tony Mok, an oncologist at the Chinese University of Hong Kong, called the study “interesting”.
“It means we can question whether in the future it’s possible to use lung computed tomography to look for precancerous lesions in the lungs and try to reverse them with drugs like these,” he said. beta-blocker interleukin 1 or not.
Swanton calls air pollution the “hidden killer,” pointing out that the study estimates it’s linked to the deaths of more than eight million people each year — roughly the same number as tobacco causes.
Another study linked PM2.5 to 250,000 annual deaths from lung cancer alone.
“You and I have a choice about whether we smoke or not, but we don’t have a choice about the air we breathe,” said Swanton, also chief clinician at Cancer Research UK, main sponsor of the study, said. .
He added: “With five times more people exposed to unhealthy levels of pollution than cigarettes, you can see this is a sizable global problem.
“We can only solve it if we recognize the truly intimate connection between climate health and human health.”
