Lung cancer is the leading cause of cancer death. In 10-25% of cases, this tumor develops in nonsmokers, it happens at a younger age than smokers.
It is known that the risk of lung cancer is influenced by factors such as secondhand smoke, exposure to radon and asbestos, and lung disease. However, scientists believe that their influence cannot explain the prevalence of the disease in nonsmokers.
In a new study led by experts from the US National Institutes of Health, scientists sequenced the genome of cancerous and normal tissues in 232 nonsmoking patients with multiple types of lung cancer. The study was conducted before people began to receive treatment.
The study authors first checked the cancer genome for the presence of known mutations that can lead to oncological diseases, which develop as a result of oxidative stress and the action of carcinogens. (Modern methods are helping to clarify which mutation caused the cancer.) Scientists have found that known oncogenic mutations do not explain some cancers.
It turned out that in nonsmokers, mutations that cause cancer are usually associated with endogenous gene damage, that is, with the impact of various processes in the body. Even people who were exposed to secondhand smoke did not have mutations associated with direct exposure to tobacco smoke. The researchers note that there were relatively few participants in the study and it was not known how often they were passively smoking.
“We need a large sample of detailed information to study the effects of secondhand smoke on the development of lung cancer in nonsmokers,” said Maria Teresa Landi of the National Institutes of Health’s Cancer Epidemiology and Genetics Division, lead author of the study.
Genome analysis also revealed three new subtypes of lung cancer in non-smokers. Scientists have given them musical names depending on the number of mutations:
- “Piano” (variant with the least number of mutations, with very slow growth);
- “Mezzo-forte” (mutations are combined with chromosomal changes, it grows relatively quickly);
- “Forte” (characterized by a doubling of the genome and rapid growth).
Scientists believe that the discovery of new subtypes of cancer 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.