International researchers said Monday they have made steps toward understanding why the most commonly used drugs for osteoporosis worldwide, known as bisphosphonates, may also prevent some kinds of lung, breast and colon cancers.
If confirmed in clinical trials, the findings could accelerate the use of drugs like alendronic acid (Fosamax), zoledronic acid (Reclast, Zometa) and ibandronic acid (Boniva) to prevent tumors or treat them in their early stages, according to two studies in the Proceedings of the National Academy of Sciences.
Bisphosphonates work by blocking the abnormal growth signals that are passed through a family of proteins known as human EGF receptors (HER), the studies found.
This, in essence, shuts down the cancer's ability to spread, and is of particular importance because HER cancers tend to be more aggressive than other types.
"Our study reveals a newfound mechanism that may enable the use of bisphosphonates in the future treatment and prevention of the many lung, breast and colon cancers driven by the HER family of receptors," said lead study author Mone Zaidi, professor of medicine at the Icahn School of Medicine at Mount Sinai in New York.
"Having already been approved by the Food and Drug Administration (FDA) as effective at preventing bone loss, and having a long track record of safety, these drugs could be quickly applied to cancer if we can confirm in clinical trials that this drug class also reduces cancer growth in people."
Previous research has shown that some breast cancer patients have lived longer while taking the medications to prevent bone loss, and that those who take them also have fewer cases of colon and breast cancer than people who do not take them.
About one in five cases of breast cancer is HER2-positive, meaning it contains a protein that promotes cancer cell growth.
The medications could have important implications for colon and lung cancer, too, since about 30 percent of cases of non small cell lung cancer and 90 percent of colon cancers are driven by HER mutations.
Such cancers often become resistant to treatment.
Researchers from China, Italy, Britain and the United States also found that the drugs did not work against colon cancer cells expressing low levels of HER.
The studies were done on mice and on cells in lab dishes. Randomized trials in humans are needed in order to better understand the drugs' effect on cancer.
However, researchers are encouraged that "bisphosphonates can potentially be repurposed for the prevention and therapy of HER family-driven cancers," the study said.