Researchers may have discovered why only some smokers develop lung cancer. Photo by Myriams-Fotos/Pixabay
Some cigarette smokers may have genes that protect them from the genetic mutations that cause lung cancer, a study published Monday by Nature Genetics found.
The analysis of the cells lining the lungs of both smokers and non-smokers found that smokers had more of the genetic mutations that cause lung cancer, the data showed.
However, while the number of genetic mutations detected in lung cells increased in parallel with the amount and length of time people smoked, this increase stopped at a certain point — 23 «pack-years,» which equates to smoking one pack per day of cigarettes for 23 years, the researchers said.
This suggests that some long-time, heavy smokers are able to «suppress further mutation accumulation» because they have «proficient systems for repairing DNA damage or detoxifying cigarette smoke,» study co-author Dr. Simon Spivack said.
«The heaviest smokers did not have the highest mutation burden,» Spivack, a professor of medicine, epidemiology and population health and genetics at Albert Einstein College of Medicine in New York City and a pulmonologist at Montefiore Health System, said in a press release.
«Our data suggest that these individuals may have survived for so long in spite of their heavy smoking because they managed to suppress further mutation accumulation,» he said.
Nearly 240,000 people in the United States will be diagnosed with lung cancer this year, about 80% of them smokers, the American Cancer Society estimates.
However, although the majority of lung cancer cases involve smokers, not all smokers develop lung cancer, Spivack and his colleagues said.
About 13% of adults in the United States are active smokers, the lowest level since the 1960s, according to the Centers for Disease Control and Prevention.
For this study, Spivack and his colleagues used a technology called single-cell multiple displacement amplification, which was developed by Einstein College of Medicine researcher Jan Vijg, and allows for genetic analysis of individual cells.
They used the approach to assess lung epithelial cells, or those lining the walls of the lungs, in 14 «never-smokers» ages 11 to 86 years and 19 smokers ages 44 to 81 years. The cells were collected from patients who were undergoing bronchoscopy for diagnostic tests unrelated to cancer, according to the researchers.
The analysis revealed that genetic mutations accumulated in the lung cells of both non-smokers and smokers as they age, the data showed.
However, significantly more mutations were found in the lung cells of the smokers in the study, the researchers said.
The number of cell mutations detected in lung cells increased along with the number of pack years of smoking, with one pack-year equating to one pack of cigarettes smoked per day for one year, they said.
Still, the rise in genetic mutations in lung cells stopped after the 23 pack-years of exposure.
The findings could help identify smokers who are at higher risk for lung cancer and thus warrant close monitoring, the researchers said.
«This may prove to be an important step toward the prevention and early detection of lung cancer risk and away from the current herculean efforts needed to battle late-stage disease,» Spivack said.