In France, there are approximately 13 million smokers for 46,363 cases of lung cancer (registered in 2018). If the lung cancer is the third most common cancer in the country, between 10 and 20% of lifetime smokers, eventually develop the disease. According to one study conducted by scientists at the Albert Einstein College of Medicine and published April 11, 2022 in the journal Nature Geneticssome smokers may have robust mechanisms that protect them from lung cancer by limiting mutations.
According to cancer specialists, cigarette smoke would promote the onset of the disease by causing mutations in the DNA of lung cells, which over time become malignant cells. “But that could never be proven until this study, because there was no way to quantify mutations in normal cells.“, says Jan Vijg, co-lead author of the study.
To achieve their results, the Albert Einstein College researchers developed a new sequencing technique called single-cell multiple displacement amplification (SCMDA). The researchers used it on 33 participants aged 11 to 86, in order to “compare the mutational landscape” bronchial basal cells, i.e. those lining the lungs. The participants were divided into two groups: 14 non-smokers aged 11 to 86 on one side, and 19 smokers aged 44 to 81 years. “These lung cells can survive for years, even decades, and therefore can accumulate mutations with age and smoking“, indicates the study. Those who are most at risk of becoming cancerous cells.
“The heaviest smokers did not have the highest number of mutations“
Results: many more mutations were found in the lung cells of smokers than in those of non-smokers. “This experimentally confirms that smoking increases the risk of lung cancer by increasing the frequency of mutationssaid Dr. Spivack, another author of the study. This is probably one of the reasons why so few non-smokers get lung cancer.“. In France, 15% of lung cancers occur in non-smokers. Besides, ISmoking is implicated in approximately 80% of lung cancer cases. “There are other risk factors that are rarer, in particular occupational exposure to certain heavy metals, asbestos, arsenic, etc.“, told us in a previous article Professor Nicolas Girard, oncologist at the Institut Curie.
Another interesting finding: the number of mutations detected in lung cells increased in a straight line with the number of pack-years of smoking – one pack-year is equivalent to one pack of cigarettes smoked per day for one year. However, the increase in mutations stopped after 23 packet-years. “The heaviest smokers did not have the highest number of mutations. Our data suggest that these individuals may have survived so long, despite their heavy smoking, because they managed to prevent the accumulation of additional mutations.“, ends Dr. Spivack.
These results could help identify smokers who face an increased risk of contracting the disease and which therefore warrant particularly close monitoring. “This may prove to be an important step towards prevention and early detection of lung cancer risk.“, concludes the study.
Sources:
- Single-cell analysis of somatic mutations in human bronchial epithelial cells in relation to aging and smoking, Nature GeneticsApril 11, 2022
- Study suggests why most sleepers don’t get lung cancer, Science DailyApril 11, 2022
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