Scientists discover how air pollution causes lung cancer

Scientist studying brain tumour cells

A searcher looks at the vascular network of a cancerous tumor, in an oncology laboratory at the research and development site of French Pharmaceutical Company Sanofi, near Paris on September 9, 2022.

Photo credit: AFP

A team of scientists has made a breakthrough in identifying how air pollution triggers lung cancer in non-smokers.

The new development could help medical experts prevent, detect and treat tumours.

The findings expose how tiny particles produced by combustion engine vehicles promote the growth of lung cells that harbour cancer-causing mutations.

The findings help explain why so many non-smokers develop lung cancer and could provide clues for preventing them from developing such tumours, the researchers said.

The findings, which have not yet been published in a peer-reviewed journal, were presented at the European Society for Medical Oncology’s annual conference in Paris on Saturday.

“Our study has fundamentally changed how we view lung cancer in people who have never smoked,” said project leader Charles Swanton, professor of personalised cancer medicine at University College London.

“Cells with cancer-causing mutations accumulate naturally as we age but are normally inactive. We’ve demonstrated that air pollution wakes these cells up in the lungs, encouraging them to grow and potentially form tumours.”

The scientists analysed data about PM2.5 exposure and lung cancer in 400,000 people from the UK, Taiwan, and South Korea and conducted laboratory experiments with mice, human cells, and tissues.

Two crucial environmental carcinogens – tobacco smoke and ultraviolet light – damage DNA and create mutations that generate tumours.

However, the researchers found no evidence that PM2.5 particles directly mutate DNA, which prompted them to look for a different explanation.

They found that the particles caused inflammation, which activated pre-existing mutations in genes that drive the development of many lung cancers.

“The mechanism we’ve identified could ultimately help us to find better ways to prevent and treat lung cancer in never smokers. The next step is to discover why some lung cells with mutations become cancerous when exposed to pollutants while others don’t,” Prof Swanton added.

The findings may apply to other cancers associated with air pollution, including mesothelioma and tumours of the throat and mouth, said Emilia Lim, a member of the Francis Crick Institute in London.

Leading cause

Smoking remains the leading cause of lung cancer, but in 2019, some 300,000 deaths worldwide were attributed to exposure to PM2.5 – tiny particles found in car fumes.

“Ninety-nine per cent of the world’s population lives in areas which exceed annual World Health Organization limits for PM2.5, underlining the public health challenges posed by air pollution across the globe,” Ms Lim added.

Air pollution has been linked to other health problems, including asthma, chronic obstructive pulmonary disease (COPD), heart disease, and dementia. How it causes cancer in people who have never smoked has long been a mystery.

Prof Swanton emphasised the importance of reducing air pollution to lower disease risk.

The research was funded by Cancer Research UK as part of broader efforts to understand how lung cancer starts and evolves in the hope of finding new treatments for the disease.

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