byUniversity of Colorado Anschutz

Researchers at the CU Anschutz Cancer Center have discovered how breast cancer cells that spread to the lungs may take advantage of the body's natural healing response and how a commonly used drug might slow that process. They found that breast cancer cells that spread to the lungs trigger the lung's normal repair system, creating conditions that unintentionally help tumors grow.

The study was published inCancer Research Communications.

How cancer uses the lung's healing system

When breast cancer spreads to the lungs, it damages tiny air sacs needed for people to breathe. Normally the lung would quickly work to repair this damage.

Researchers found that cancer cells prolong the damage repair mode, leading to chronic inflammation.

Specialized lung cells calledalveolar type II cellsnormally help rebuild lung tissue after injury. When cancer cells are present, these lung cells begin releasing signals that encourage tumors to grow.

"The lung is doing what it is designed to do and that is to clear debris and repair damage," said Jessica L. Christenson, Ph.D., first author of the study and an instructor in the Department of Pathology at CU Anschutz. "But in this case, cancer cells are taking advantage of that repair response."

A cycle that helps tumors grow

The researchers found thatcancer cellsand lung cells begin signaling to each other.

Cancer cells activate lung cells, which then release substances that fuel cancer growth. This eventually allows tumors to expand.

A possible new way to slow metastatic cancer

The team tested Roflumilast, a medication approved to treat Chronic Obstructive Pulmonary Disease (COPD).

In mouse models of metastatic breast cancer, the drug slowed tumor cell growth and reduced the size of tumors in the lungs. Rather than killing cancer cells, the drug prevented the lung environment from helping the tumors grow.

"This suggests a new strategy for treating metastatic cancer," said Jennifer K. Richer, Ph.D., senior author of the study and professor of pathology at the CU Anschutz Cancer Center. "In addition totargeting cancer cellsthemselves, we may also be able to target the environment that allows them to thrive."

Why this matters

Breast cancer is more difficult to treat once it spreads to other parts of the body. It often spreads to the lungs. About one third of people with metastatic breast cancer develop lung metastases and treatment options are limited.

Because roflumilast is already approved for another condition, it may be possible to study its potential use in metastatic cancer more quickly.

What comes next

Researchers plan to study how this drug might work together with chemotherapy or immunotherapy and whether it can effectively alleviate common side effects of cancer treatment. They are also exploringinhaled versionsof similar drugs that could deliver treatment directly to the lungs.

"We are very excited to translate these findings to the clinic and evaluate roflumilast as a treatment for patients with triple-negative breast cancer to prevent recurrence in the lungs," said Jennifer R. Diamond, MD, a professor of medical oncology and medical director of the Cancer Clinical Trials Office (CCTO) at the CU Anschutz Cancer Center and close collaborator on this project.

More information Jessica L. Christenson et al, Metastasis-associated wound repair promotes reciprocal lung epithelium activation and breast cancer metastatic outgrowth, Cancer Research Communications (2026). DOI: 10.1158/2767-9764.crc-25-0459