Bone drug’s anti-cancer properties should be celebrated
Some calcium-binding drugs often used to treat people with osteoporosis may also benefit people with tumours outside the skeleton (including breast cancer), and now experts have discovered why.
Several clinical trials – where women with breast cancer were given bisphosphonates as well as normal treatment for early-stage disease – showed that they have a “survival advantage” and inhibit cancer spread in some women.
Now new imaging technologies show that bisphosphonates attach to tiny calcifications in tumours in mice. These calcium-drug complexes are then devoured by immune cells (macrophages) that the cancer hijacks early in its development to conceal its existence.
“We do not yet fully understand how the macrophages revert from being ‘bad cops’ to being ‘good cops’, although it is clear that this immune cell interacts with tumours, and probably changes its function in the presence of bisphosphonates,” explains project leader Prof Mike Rogers.
“The surprising thing is that we didn’t make the connection between bisphosphonates and tumour calcifications before – of course bisphosphonates are going to bind to calcium! It had been staring us in the face for a long time, yet we didn’t explore that action of the drug. Perhaps because there is such strong acceptance that these drugs only work in bone.”
The team thinks that the process is the same in humans. When they stained a breast cancer tumour sample for calcifications, they found them next to and even inside macrophages.
“This study is potentially transformative for treatment of some cancers, because it is telling us for the first time that drugs we thought acted only in bone can also act within tumours completely outside the skeleton, and have a beneficial effect,” says Prof Rogers. “We already know this drug is well-tolerated in people and provides a survival advantage for some patients with certain cancers when taken early in disease development. This now provides a rationale for using these drugs in a different, and potentially more effective, way in the clinic.”
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Image credit: Matthew Faltz
