Lung cancer cases are on the rise in non-smokers around the world, and air pollution could be an insidious, contributing factor.
The findings don’t mean that air pollution is directly causing lung cancer, but they do contribute to evidence suggesting that possibility.
“Our research shows that air pollution is strongly associated with the same types of DNA mutations we typically associate with smoking.”
Not so for air pollution or tobacco smoking: both were strongly linked to DNA mutations.
The majority of non-smokers with lung cancer had adenocarcinomas (the most common type of lung cancer), and nearly 5 percent of those tumors showed the SBS4 mutational signature.
Globally, the number of nonsmokers developing lung cancer is increasing, and air pollution may be a sneaky contributing factor.
According to a genome study, soot and outdoor smog are now strongly linked to DNA mutations linked to lung cancer, including new ones specific to non-smokers and known ones seen in smokers.
Scientists discovered more mutations in lung tumors of people exposed to higher levels of pollution.
The results add to evidence that air pollution may be a direct cause of lung cancer, but they do not prove it.
Related: Researchers Are Now Nearer to the Causes of Lung Cancer in Nonsmokers.
“We haven’t understood why we’re seeing this problematic trend that never-smokers are getting lung cancer more and more,” says Ludmil Alexandrov, a biomolecular scientist at the University of California San Diego (UCSD).
The same kinds of DNA mutations that we usually associate with smoking are also strongly linked to air pollution, according to our research. “.”.
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The comprehensive global analysis analyzed the cancer genomes of 871 people from four continents who had lung cancer even though they had never smoked and had not yet received cancer treatment.
Shorter telomeres, EGFR mutations, and TP53 mutations were substantially more common in people who lived in areas with high air pollution levels.
Shorter telomeres are associated with accelerated aging, and abnormal TP53 and EGFR genes are characteristic of lung cancers, particularly those caused by the SBS4 DNA mutation.
Nonsmokers in the current study were almost four times more likely to have SBS4 signatures in areas with higher air pollution than in areas with cleaner air.
On the other hand, secondhand smoke exposure, which is known to increase the risk of cancer, only slightly increased the number of genetic mutations.
“If there is a mutagenic effect of secondhand smoke, it may be too weak for our current tools to detect,” says Tongwu Zhang, a geneticist at the National Cancer Institute (NCI) in the country.
The same was true for tobacco use and air pollution, which were both closely associated with DNA mutations.
In the United States, between 10 and 20 percent of lung cancer cases occur in people who have never smoked or who have smoked fewer than 100 cigarettes in their lifetime.
The precise relationship between fine particulate matter in the air and tobacco smoking or secondhand smoke exposure is still unknown, despite scientists’ long-standing suspicion that air pollution may play a role.
Although most of the research used to draw these conclusions was observational, some studies claim that breathing in polluted air is equivalent to smoking a pack a day.
In order to delve deeper, the current study examines a few potential molecular mechanisms. It looked for similarities and differences between the lung cancer genomes of 345 smokers and 871 non-smokers with tumors.
Nearly 5% of adenocarcinomas, the most prevalent form of lung cancer, in non-smokers with the disease exhibited the SBS4 mutational signature.
Furthermore, a new signature known as SBS40a was present in 28% of non-smokers but not in tobacco users. Surprisingly, the cause of this specific mutational driver was not identified, but it does not appear to be environmental.
“We don’t yet know what’s driving it, but we see it in a majority of cases in this study,” Alexandrov says. This opens up a whole new field of research and is completely different. “,”.
Since the current study only looked at regional air pollution levels, it is unable to determine the exact amount of fine particulate matter that any one person was exposed to directly. Even those who claimed never to have smoked might have smoked more than they disclosed.
Notwithstanding these drawbacks, the results generally support other data suggesting that soot or smog may promote tumor growth similarly to cigarette chemicals.
“With regard to never-smokers, this is a pressing and expanding worldwide issue that we are trying to comprehend,” says NCI epidemiologist Maria Teresa Landi.
In the future, the group intends to broaden their investigation to incorporate cancer genomes from a more varied, international group.
