Scientists discover how air pollution causes lung cancer

An international team of scientists has made a breakthrough in determining how air pollution causes lung cancer in people who have never smoked, a development that could help medical professionals. prevention and treatment of tumors.

Researchers discovered fine particles in polluted air that cause pneumonia, activating pre-existing cancer genes that were inactive. It was previously believed that air pollution caused genetic mutations that lead to cancer.

The findings, based on research led by the Francis Crick Institute in London and funded by Cancer Research UK, have been published at European Society of Medical Oncology Conference in Paris on Saturday.

As fewer people smoke, air pollution is emerging more clearly as a cause of tumors in the lungs. Estimate 300,000 deaths from lung cancer each year worldwide is caused by very fine pollutant particles less than 2.5 microns in diameter, known as PM2.5, that are released in vehicle exhaust and fossil fuel combustion.

“Our research has fundamentally changed the way we see the lungs cancer in people who have never smoked,” said project leader Charles Swanton. “Cells with cancer-causing mutations build up naturally as we age, but they are usually dormant. We have demonstrated that air pollution awakens these cells in the lungs, encouraging them to grow and potentially form tumors.”

The project is part of the £14m Cancer Research UK programme, which aims to understand how lung cancer begins and progresses. Scientists analyzed data on PM2.5 exposure and lung cancer in 400,000 people from the UK, Taiwan and South Korea, and performed laboratory experiments with mice, human cells and tissues. .

Lung tumor, tumor cells (cyan) express proteins (pink) to handle low-oxygen environments.  These images allow scientists to examine the blood vessels (in red) in the tumor
Lung cancer cells under the microscope © Francis Crick Institute

Two important environmental carcinogens, cigarette smoke and ultraviolet light, damage DNA and create tumor-generating mutations. But the researchers found no evidence that PM2.5 particles directly mutate DNA, which prompted them to look for another explanation.

They found that the particles cause inflammation, triggering pre-existing mutations in genes that lead to the development of many lung cancers.

“The mechanism we identified could help us find better ways to prevent and treat lung cancer in never-smokers,” Swanton said. “The next step is to discover why some mutated lung cells become cancerous when exposed to pollutants while others do not.”

Emilia Lim, another member of the Crick research team, said the findings could apply to other cancers linked to air pollution, including mesothelioma and throat tumors. and mouth. “Ninety-nine percent of the world’s population live in areas that exceed the World Health Organization’s annual limit for PM2.5, underscoring the public health challenges posed by air pollution globally,” she added.

One way to combat the harmful effects of air pollution could be to block a molecule called interleukin-1beta, which plays an important role in the inflammatory response to PM2.5. The team found that the method worked in mice.

Tony Mok, a professor of oncology at the Chinese University of Hong Kong, who was not involved in the study, said the study results were “intriguing and exciting”.

“That means we can question whether in the future it’s possible to use lung tomography to look for precancerous lesions in the lungs and find ways to reverse them with drugs,” he said. .

He joined Swanton in emphasizing the importance of reducing air pollution to reduce the risk of disease.

“We have known about the link between pollution and lung cancer for a long time, and now we have a possible explanation for it,” says Mok. “As fossil fuel consumption goes hand in hand with pollution and carbon emissions, we have a strong mandate to address these issues – for both environmental and health reasons.”

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