New Delhi: Smoking is one of the leading causes of lung cancer, but a long-standing question has puzzled scientists for decades: Why do some lifelong smokers never develop lung cancer, while some people who have never smoked are diagnosed with the disease?
A new study by researchers at the University of Cambridge, published in the journal Nature, suggests that the answer may lie partly in a person’s inherited genetic makeup. The findings provide the first direct evidence that genetic differences can influence how the body responds to DNA damage caused by cigarette smoke, sunlight and other environmental exposures.
Cancer develops when DNA accumulates mutations that allow abnormal cells to grow uncontrollably. Cigarette smoke contains numerous carcinogens that damage DNA and significantly increase the risk of lung cancer. However, researchers found that inherited genetic variations may determine how efficiently the body repairs this damage, influencing whether cancer eventually develops.
To investigate this, scientists studied nearly 600 tumours in genetically diverse mice that were exposed to the same cancer-causing chemical under identical laboratory conditions. Because every mouse experienced the same environmental exposure, researchers were able to isolate the role of inherited genes. While tumours across different mice often followed similar biological pathways, the mutations that developed varied depending on their genetic background.
According to the researchers, these findings help explain why cancer risk is not determined by smoking alone. Factors such as inherited genes, environmental exposures, the amount and duration of tobacco use, and the body’s ability to repair DNA damage all play important roles in determining an individual’s risk.
Pulmonologists say the findings should not be misunderstood as suggesting that some people are “immune” to smoking. Experts stress that smoking remains the single biggest preventable risk factor for lung cancer and several other serious illnesses, including chronic obstructive pulmonary disease (COPD), heart disease and stroke. Even if a smoker never develops lung cancer, tobacco smoke can still cause irreversible damage to the lungs, blood vessels and other organs.
Researchers believe the study could eventually improve cancer screening by helping identify people who are genetically more susceptible to developing cancer. In the future, inherited genetic information may allow doctors to personalise cancer prevention strategies and recommend earlier screening for individuals at higher risk. However, the current findings were obtained in mice, and further research is needed to confirm whether the same mechanisms apply to humans.
Despite the promising findings, scientists emphasise that the public health message remains unchanged. Quitting smoking is still the most effective way to reduce the risk of lung cancer and many other smoking-related diseases. The absence of symptoms does not mean the lungs are healthy, as tobacco-related damage often develops silently over many years.
