The most commonly used medications for osteoporosis may also help prevent or treat certain types of cancer.

Bisphosphonates have been used for more than 30 years to treat osteoporosis, or bone thinning, which commonly occurs as we age. Now, a team of researchers led by Dr. Mone Zaidi, a professor of structural and chemical biology at the Icahn School of Medicine at Mount Sinai, has found that bisphosphonates may treat or even prevent certain types of lung, breast, and colon cancer.

Their findings are published in two papers in Proceedings of the National Academy of Sciences.

In the first study, the researchers found that bisphosphonates kill breast, colon, and lung cancer cells that have special receptors called human epidermal growth factor receptors (human EGFR, or HER). They kill by blocking the signal that causes the cancer cells to divide and multiply rapidly.

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In the second study, the researchers describe potential applications for this discovery. These include cancer prevention, combining bisphosphonates with existing anti-cancer drugs called tyrosine kinase inhibitors (TKIs), and helping non-small cell lung cancers (NSCLC) overcome resistance to drug treatment.

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“Our study reveals a new mechanism that may allow the future use of bisphosphonates for the treatment and prevention of the many lung, breast, and colon cancers driven by the HER family of receptors,” Zaidi told Healthline.

Zaidi explained that because bisphosphonates have a long track record of safety and efficacy, they could quickly be repurposed to treat cancer if clinical trials demonstrate that they slow or prevent tumor growth in humans.

Some human cancers, including NSCLC, have mutations, or changes, in the HER receptors that make these cancers grow and spread quickly. TKIs work by binding to the HER receptor.

Zaidi and his team showed that bisphosphonates are able to bind to the same part of the HER receptor as TKIs. So bisphosphonates may have the potential to treat cancers that are resistant to TKIs.

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Once the researchers had found a link between the HER receptor and bisphosphonates, the scientists ran experiments in mice. They found that bisphosphonates alone or in combination with the TKI gefitinib (Iressa) prevented the growth and spread of tumor cells.

Plus, bisphosphonates and TKIs together were shown to reverse tumor growth in mice. Moreover, mice that were given only bisphosphonates did not form HER-driven tumors in the first place. On the other hand, mice with colon cancer cells that were not driven by HER did not respond to treatment with bisphosphonates.

The researchers hope to conduct human clinical trials in the near future. In the meantime, Zaidi said, “I think physicians should be told the literature now suggests these drugs can prevent cancers.”

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