Study Reveals Why Most Smokers Don't Fall Prey To Lung Cancer

Worldwide, cigarette smoking is considered to be the main reason behind lung cancer but only a small percent of smokers fall prey to the disease. A study done by scientists at the Albert Einstein College of Medicine and published online in Nature Genetics reveals that certain smokers have in-built mechanisms, which safeguards against cancer by limiting mutations.

The findings of the study can be useful in knowing which smoker has a higher chance of getting the disease and therefore, can be kept under close survey.

Commenting on the developments, Simon Spivack, MD, MPH, a co-senior author of the study, 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, where the majority of health expenditures and misery occur."

The study revealed that single-cell whole-genome sequencing methods could introduce sequencing errors, which are difficult to separate from true mutations. This is a serious flaw while analysing cells containing rare and random mutations. Researchers solved this problem by developing a new sequencing technique called single-cell multiple displacement amplification or SCMDA. As has been earlier reported in Nature Methods in 2017, this method is far equipped to handle sequencing errors.

The Einstein researchers used SCMDA to compare the mutational landscape of normal lung epithelial cells (i.e., cells lining the lung) from two types of people: 14 never-smokers, ages 11 to 86; and 19 smokers, ages 44 to 81, who had smoked a maximum of 116 pack years. The cells were collected from patients who were undergoing bronchoscopy for diagnostic tests unrelated to cancer. Spivack said, "These lung cells survive for years, even decades, and thus can accumulate mutations with both age and smoking. Of all the lung's cell types, these are among the most likely to become cancerous."

The researchers found that mutations, whether single-nucleotide variants and small insertions and deletions deposited in the lung cells of non-smokers as they age and more mutations were found in the lung cells of the smokers. "This experimentally confirms that smoking increases lung cancer risk by increasing the frequency of mutations, as previously hypothesized," said Dr. Spivack.

Another finding from the study is that the number of cell mutations found in lung cells increased in a straight line with the number of pack years of smoking and thus increasing the risk for lung cancer as well. However, the rise in cell mutations was stopped exposure to 23 years of smoking cigarettes.

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