The Lung Tumor Microbiome

A host of bacteria and other microscopic organisms live in your body. This natural community of tiny organisms is called the microbiome. Research has shown that a balanced and diverse microbiome is important for your health.¹

In the past, experts thought the lungs had no bacteria. But advances in testing have shown that the lungs contain a unique microbiome. There is now clear evidence that changes in the normal lung microbiome play a role in lung cancer.^2-8

The normal lung microbiome

The healthy lung microbiome contains many of the same bacteria found in the upper airway (nose, mouth, and throat). Bacteria move between the lungs and the rest of the upper airway as you breathe. But normally, the lungs contain fewer bacteria than the upper airway.²

A balanced microbiome works with your immune system to protect your body. But changes to the normal lung microbiome can lead to illness. These changes may increase your chances of developing lung cancer. They also may reduce the success of cancer treatment.^2-6,9

The lung tumor microbiome

Advanced technology allows scientists to study the bacteria found in lung cancer tissue. These studies show that the microbiome in lung tumors is different from that of normal lung tissue.^3-8,10

This microbiome varies between different lung cancer types and stages. But both the types and the amounts of bacteria are different in lung tumors than in normal tissue. And the overgrowth of certain bacteria is linked to a higher risk of cancer recurrence and a worse prognosis.^3-8,10

Also, a 2021 study found that non-small cell lung cancer (NSCLC) had high amounts of a specific type of bacteria. Having these bacteria was linked to poor response to a class of anti-cancer drugs called immune checkpoint inhibitors.⁶

Lung cancer and microbiome changes

The interactions between bacteria, the immune system, and cancer are complex. But ongoing research is providing a glimpse into this hidden world.^7,9

Genetic changes (mutations) can occur in the normal cells that line the lungs. These changes allow cancer-promoting bacteria to overgrow (dysbiosis). Dysbiosis changes the environment inside the lungs and plays a role in lung tumor growth. However, more research is needed to understand which happens first – dysbiosis or lung cancer.^2,3,10

One of the ways dysbiosis may promote lung cancer is by triggering the immune system. Complex interactions between bacteria and the immune system can cause normal cells to become cancerous.^2,3,9

Also, some bacteria are known to cause cancer directly. These bacteria can change the genes of normal cells, transforming them into cancer cells.⁹

Current lung microbiome research

A 2022 study from the National Cancer Institute looked at the activity of bacteria inside lung tumors. The researchers studied tissue samples from patients with early-stage lung cancer. They looked at both the bacteria and immune cells inside lung tumors. The bacterial load inside lung tumors was higher than in normal lung tissue.⁸

A higher amount of bacteria was linked with a boost in cell processes that promote tumor growth. This study provides strong evidence that bacteria can lead to lung tumors.⁸

Future lung microbiome research

Using data about the lung microbiome, scientists hope to create tests that can find lung cancer and predict recurrence. They are studying whether testing for specific patterns of bacteria could be used to find lung cancer earlier.^3-5,7

Another area of interest is whether the lung microbiome can be changed. Can the normal microbiome be restored? Could changing the microbiome improve treatment response or even prevent cancer from developing? More research is needed to answer these questions.^6-8