After breaking away from the original tumor, cancer cells often spread to other organs. There they can either form metastases or lie dormant for many years before reactivating. Scientists at the University of Fribourg have discovered a mechanism that makes it possible to keep such cancerous cells in a dormant state by stimulating the immune system’s response. This discovery was recently published in the journal NPJ Breast Cancer. It could help improve therapies for women with breast cancer.

Thanks to early detection and modern therapies, most breast-cancer patients today have a very good chance of recovery. However, in some women, metastases do appear and unfortunately remain difficult to treat. Finding ways to control these metastases would open up new therapeutic avenues in patient care.

The immune system plays an essential role in controlling cancer. It can stop tumors from forming, maintain cancerous cells in a “dormant” state, and slow their growth. It is of major clinical importance then to better understand how cancerous cells enter this dormancy, are kept in that state, and may become active once again.

CXCL10: A “sleep-inducing” molecule that stimulates the immune system
The postdoctoral researcher Alev Ylmaz is part of Professor Curzio Rüegg’s research team at the University of Fribourg. Working with Dr. Qiang Lan, a senior research associate at the University of Bristol, she ran several experiments using mice as models and discovered that a molecule produced by dormant cancer cells makes it possible to maintain the dormancy of cancer cells in so-called “triple-negative” breast cancers, a particularly aggressive form of the disease.

The molecule is called CXCL10 and belongs to a well-known family of molecules that are able to attract immune cells, called chemokines (short for chemotactic cytokines). CXCL10 acts by drawing to the site of the tumor immune cells that are able to fight it, preventing cancerous cells from developing. On the other hand, when CXCL10 or its receptor, CXCR3, are deliberately blocked in experiments , the immune cells can no longer reach the tumor. The cancer cells then emerge from their dormant state and begin to grow once again. Crucially they can now spread to other organs like the lungs.

From these lab results, the researchers have identified a “dormancy signature” that is linked to CXCL10 and detectable in patients’ tumors. As Alev Ylmaz explains, “This signal shows that the cancer cells are dormant rather than active. It is especially important to note that patients exhibiting this signature have on average a better prognosis.”

Implications for cancer patients
This discovery brings to light a key new role played by the immune system in the progression of breast cancer and points the way to new treatments. First, it suggests that targeting the CXCL10/CXCR3 axis could improve the treatments currently offered to triple-negative breast cancer patients. Secondly, the dormancy signature based on CXCL10 might also help identify patients who are at higher risk of metastases and would benefit the most from new therapeutic strategies.

Yilmaz, A., Haerri, L., Estrella Granda, M., Coquoz, O., Lan, Q., & Rüegg, C. (2026). The CXCL10/CXCR3 axis is essential for sustaining immunological dormancy in triple-negative breast cancer. NPJ Breast Cancer. https://doi.org/10.1038/s41523-026-00903-6