Link discovered between pollution and lung cancer in people who have never smoked

BarcelonaA quarter of lung cancer cases occur in people who have never smoked, and a study published Wednesday in Nature suggests that the global increase in these tumors in this group is closely linked to air pollution and other environmental exposures. The research, led by researchers from the University of California, San Diego, and the National Cancer Institute (NCI), analyzed the tumors of more than 870 nonsmokers from different regions of the world.

"Our research shows that air pollution is strongly associated with the same types of DNA mutations typically associated with smoking," explains Ludmil Alexandrov, co-author of the study, a professor at the University of California and a member of the Moores Cancer Center at the University of San Diego. In fact, this is the first time lung cancer has been linked to DNA damage caused by breathing polluted air.

By sequencing the entire genome of 870 people, researchers identified distinct patterns of DNA mutations ormutational signatures, These are molecular fingerprints of past environmental exposures. Combining this with estimates of air pollution, the study concludes that those who have never smoked but live in areas with high pollution have a higher number of mutations in lung tumors, especially those that promote cancer development and others that reflect previous exposure to carcinogens.

In other words, the more pollution a person was exposed to, the more mutations were found in their lung tumors. However, this doesn't mean that pollution causes a unique signal.per se, but rather increases the total number of mutations, explains the new head of the Digital Genomics Group at the Spanish National Cancer Research Centre (CNIO), Marcos Díaz-Gay, a former postdoctoral researcher in Alexandrov's laboratory, in a CNIO statement.

Mutations specific to non-smokers

Joaquim Bosch Barrera, clinical expert on lung cancer at ICO Girona, told SMC Spain that "this study highlights the importance of controlling air pollution to prevent respiratory diseases." However, he also emphasized that "smoking remains the most important risk factor for developing lung cancer."

However, researchers have not found a strong link between lung cancer and secondhand smoke. In nonsmokers exposed to secondhand smoke, tumors showed only a slight increase in mutations and signs of cellular aging, but not the genetic alterations typical of cancer development. Although secondhand smoke remains a risk factor, research indicates that its impact is much smaller than that of air pollution.

Finally, the team has identified a pattern of mutations that appear in most cancers in nonsmokers, but that have not been detected in smokers. The reason for this mutation is unknown, as it has no correlation with air pollution or any known environmental exposure. "We see it in most cases in this study, but we still don't know what causes it," Alexandrov said. This new question opens up a new area of research for the future.

Recently Díaz-Gay and Alexandrov also published inNatureanother analysis of the trace left on DNA by certain environmental agents, and thus related the increase in colorectal cancer in young people with exposure to a bacterial toxin in childhood.