Why do many longtime smokers not get lung cancer?

This natural defense against cancer-causing mutations is thought to be what keeps some long-term smokers from getting lung cancer.

Smoking is the main cause of lung cancer, however, only a small number of smokers develop the disease.

New research, led by scientists at Albert Einstein College of Medicine, USA, and published in the journal Nature Genetics on April 11, shows that some smokers have a powerful mechanism to help protect them from cancer lung by limiting mutations.

Cigarette smoking increases the risk of lung cancer by increasing the frequency of mutations.

Prof. Dr. Simon Spivack, Albert Einstein College of Medicine, USA, co-author, said: 'This could be an important step forward in the prevention and early detection of lung cancer risk, avoiding extremes when fighting against cancer. this disease".

According to Science Daily, it has long been thought that smoking leads to lung cancer by triggering DNA mutations in normal lung cells.

"But that was never proven until our study came out, because there is no way to accurately quantify mutations in normal cells," said Prof. Dr. Jan Vijg, co-author of the study. , added.

Single-cell whole-genome sequencing methods can introduce errors that make it difficult to distinguish the true mutation. In the newly published paper, Dr. Vijg's team has solved this problem by developing a new sequencing technique called single-cell multiple-shift amplification (SCMDA), which minimizes existing errors.

The team of experts used SCMDA to compare mutations in normal lung epithelial cells (i.e. the cells lining the lungs) from two groups of people: 14 never-smokers (11-86 years old); 19 smokers (44-81 years old), smoked 116 packs of cigarettes/year. Cells were collected from patients undergoing bronchoscopy for diagnostic tests unrelated to cancer.

'These lung cells last for years, even decades. Therefore, it can accumulate mutations because of age and smoking. Of all lung cell types, this is one of the most likely to become cancerous,' said Prof. Dr. Simon Spivack.

The researchers found mutations that build up in the lung cells of non-smokers as they age. And more mutations were found in the lung cells of smokers.

This demonstrates that smoking increases the risk of lung cancer by increasing the frequency of mutations. "This could be one reason so few non-smokers get lung cancer, while 10-20% of long-term smokers get lung cancer," he explained.

They also found that the number of mutations in lung cells increased proportionally with the number of years smoked, meaning an increased risk of lung cancer. However, the special thing is that this increase stops after 23 years.

Dr Spivack said: 'The heaviest smokers weren't the groups with the highest mutations. They could have survived and been free of lung cancer because their bodies prevented the accumulation of mutations. This phenomenon may be due to the fact that these people have very proficient systems to repair DNA damage or detoxify tobacco smoke."

This discovery led to a new direction of research. Dr Vijg said: 'We're looking to develop new tests that can measure someone's ability to repair or detoxify DNA, which could, in turn, offer a new way to assess risk of infection. lung cancer'.