Genomic analysis has shown that most of the mutations associated with lung cancer in non-smokers are not environmentally related. The study was published in Nature Genetics.
Lung cancer is the leading cause of cancer death. In 10-25% of cases, this tumor develops in non-smokers, it occurs in them at a younger age than in smokers.
It is known that factors such as passive smoking influence the risk of lung cancer , exposure to radon and asbestos, lung disease. However, scientists believe that their influence cannot explain such a prevalence of the disease in non-smokers.
In a new study led by experts from the US National Institutes of Health, scientists conducted genome sequencing of cancerous and normal tissues of 232 non-smokers with several types of lung cancer. The study was done before people started treatment.
Lung Cancer
Men get lung cancer 7-10 times more often than women, and the incidence increases in proportion to age. In men aged 60-69, the incidence rate is 60 times higher than in men aged 30-39
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The authors of the study first tested the cancer genome for the presenceof known cancer-causing mutations that develop as a result of oxidative stress and the action of carcinogens. (Modern methods help determine which mutation caused the cancer.) Scientists have found that known oncogenic mutations do not explain some cases of cancer.
It turned out that in non-smokers, cancer-causing mutations are usually associated with endogenous gene damage, that is, with the impact of various processes occurring in the body. Even people exposed to secondhand smoke did not have mutations associated with direct exposure to tobacco smoke. Scientists note that the study had relatively few participants and it was not known how often they smoked passively.
«We need a large, detailed sample to study the impact of secondhand smoke on lung cancer in non-smokers,» said Maria Teresa Landi of the National Institutes of Health's Division of Cancer Epidemiology and Genetics, lead author of the study.
Genome analysis has also identified three new subtypes of lung cancer in non-smokers. Scientists gave them musical names depending on the number of mutations:
- «piano» (the variant with the fewest mutations, with very slow growth);
- “mezzo-forte” (mutations are combined with chromosomal changes, grows relatively quickly);
- “forte” (characterized by genome doubling and rapid growth) .
Scientists believe that the discovery of new cancer subtypes will lead to the development of individual approaches to their treatment and prevention.
“We are just beginning to understand how these tumors develop. This analysis shows that there are differences in lung cancers in people who have never smoked,” Lundy said.