A hormone released from the muscle during exercise may prevent breast cancer and boost the effects of chemotherapy drugs used to treat it, according to a study carried out at the University of New Mexico.

Following on from recent findings that exercise can slow the growth of breast cancer tumours in mice, new research suggests women who exercise regularly have a 30 to 40 per cent reduced risk of breast cancer and improved survival rates if they do get the disease.

The team at UNM built on previous studies which had found that the hormone irisin increases with exercise and stimulates metabolism in select tissues, such as fat.

“The association between exercise and improved cancer rates/mortality is strong, so it was only logical that our team pursue the link between chemicals produced during exercise and breast cancer survival,” says study collaborator Roger Vaughan. “Others were looking at how exercised muscles communicate with the body to cause overall effects. But our team at UNM was curious what, if anything, irisin might do for cancer.”

Irisin was administered to both non-cancer and cancerous cells, which selectively killed aggressive cancer cells without negatively affecting normal cells.

The researchers observed a 22-fold increase in cancer cell death compared to untreated cells. When irisin was combined with a commonly used chemotherapy drug, the destruction of cells increased significantly, while cells absorbed less of the drug. This could mean that patients could be given a more tolerable dose of the drug.

Senior author of the study, Kristina Trujillo, says: “Chemotherapy can have devastating side effects. Sometimes they are so severe that treatment regimens are disrupted. So the possibility of a method to decrease the effective dose is very exciting. Our next steps will be to test irisin against other cancers and to figure out how best to deliver irisin to the cancer cells.”

Researcher Nick Gannon says: “While the crux of the work is the effect of irisin on breast cancer, the underlying message is that exercise is important for overall health and quite often the best preventative medicine there is.”

Christine Mermier, another researcher on the study, stresses the importance of being active: “The truth is, most cancers are caused by lifestyle factors, not genes.”