A common virus known to cause cervical and head and neck cancers may also trigger some cases of lung cancer. Nearly 6% of lung cancer tissue samples from nonsmokers show signs that human papillomavirus (HPV) may have triggered the tumors.

If HPV indeed plays a role in lung cancer in some patients, the next step is to better understand those tumors so they can be treated more effectively. “The ultimate goal,” said study author Ranee Mehra, MD, attending physician in medical oncology at Fox Chase Cancer Center in Philadelphia, Pennsylvania, “is to determine if we can target our therapies to the specific characteristics of these tumors.”

Studies from Asia have shown that lung tumors are frequently infected with HPV. The pattern makes sense, explained Mehra—the lungs are located very near the head and neck, which are known to be at risk for tumors upon exposure to some strains of HPV.

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To investigate, she and her colleagues examined 36 tissue samples from people diagnosed with non-small cell lung cancer who had never smoked. The reason they chose nonsmokers, Mehra explained, is that smoking is a major cause of lung cancer—but in nonsmokers, the explanation is often less obvious.

The researchers found that four of 36 samples had signs of infection from two strains of HPV known to cause cancer, strains 16 and 18. Looking more closely at the two samples infected by HPV 16, Mehra and her team saw signs the virus had integrated into the tumor’s DNA, which is even more suggestive that the infection caused the tumor. They presented their findings at the annual meeting of the American Association for Cancer Research on April 10 in Washington, DC.

Although this suggests that HPV drives lung cancer in less than 6% of nonsmoker patients, making it a relatively rare occurrence, lung cancer is very common, Mehra noted. Lung cancer kills more than 1 million people every year. Approximately 10% of cases occur in nonsmokers. “Given how many patients develop lung cancer, if even a small percentage of those tumors stem from HPV, that ends up being a large number of patients,” she said.

It’s not clear how HPV reaches the lung, she said; patients may simply breathe it in. Just because these patients have evidence of an HPV infection that does not necessarily mean the infection caused their tumors, Mehra cautioned. “It could simply be a coincidence that they had both lung cancer and HPV,” she noted. “But the presence of both simultaneously, and the integration of the virus into the tumor’s DNA, fuels the hypothesis that they are related.”

“In my practice, I treat many people with head and neck cancers who are infected with HPV. Some fear that they are ‘contagious’, and could somehow pass the cancer onto their families,” Mehra said. “Mostly, I reassure them—even though most people have been exposed to HPV, it’s rare for someone to develop cancer as a result.”