Lung cancer is the number one cause for cancer death among both men and women, but our treatment efforts have fallen short because we don't really understand how the condition starts. A new study may have found this crucial puzzle piece; scientists recently isolated and identified the cells that appear to trigger squamous cell carcinoma, the second most common form of lung cancer. Although more research is needed, the team believe that knowing the origin of a cancer may help them prevent it.

The discovery was led by Clare Weeden from the University of Melbourne, and results are now published online in Public Library of Science: Biology. Weeden found the stem cells that repair our lungs when they become damaged due to environmental pollution and cigarette smoke, reported Pursuit, a publication run by The University of Melbourne. The cells, lung basal stem cells, trigger these repairs, but also are liable to create the mutations that eventually lead to cancer. Identifying these cells as the origin of lung cancer could lead to drugs that target these cells and prevent cancer from developing in the first place.

Read: 3 Reasons Why Non-Smokers Get Lung Cancer

For the research, Weeden spent years analyzing samples of lung cells from recent lung cancer patients. However, it wasn’t until she analyzed the cells of a non-smoker cancer patient — a group that makes up only about 4 percent of all lung cancer patients—that she finally found what she was looking for. Weeden realized a correlation between smoking status and basal stem cell quality, noting that lung samples from patients that had never smoked had low basal cell growth. On the other hand, the more heavily a patient had smoked, the higher the growth rate.

“Our lungs are constantly being exposed to what we inhale. When we breathe in something like cigarette smoke that causes lung damage, these basal cells receive a signal to grow and repair the damage,” explained Weeden to Pursuit, adding that, on the flip side, these basal cells were also very prone to mutations. The more they have to repair, the more likely they were to make a cancerous mutation.

Understanding the trigger to a problem is essential for fixing it, and preventing it from occurring again in the future — cancer is no different. Researchers now believe this discovery could stand as a model for drug developments aimed at helping to prevent cancer in ex-smokers. The biggest beneficiaries would be people who quit 20 or 30 years ago, as the drug would be counterproductive for those who continue their habit.

“If a person was treated with a drug that turned off basal cells and continued to smoke, I would imagine that other lung problems may develop due to the inability of the stem cell to repair the lung airways from cigarette smoke-induced damage,” warned Weeden.

The discovery is still quite new and it could be awhile before any such drug becomes available. However, in the meantime, we've seen other breakthroughs in the treatment of lung cancer patients, particularly in the field of immunology, or using the body’s own immune system to fight disease. In October, a drug called pembrolizumab was found to be more effective than chemotherapy in preventing cancer deaths by 40 percent. Unlike chemotherapy that uses non-organic drugs to destroy cancer cells, and unfortunately many healthy cells along the way, this drug enlisted the help of the body’s immune system to attack lung tumors.

Source: Weeden CE, Chen Y, Ma SB, et al. Lung Basal Stem Cells Rapidly Repair DNA Damage Using the Error-Prone Nonhomologous End-Joining Pathway. Plos Biology . 2017

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