When breast cancer spreads, it often targets the spine. Now scientists may have finally discovered why.
A newfound kind of stem cell drives cancer cells to bones in the vertebrae, pathologist Matthew Greenblatt of Weill Cornell Medicine in New York City and his colleagues report September 13 in Nature. The find helps explain a long-standing mystery of metastasis: why some cancers break away from their site of origin, journey through the bloodstream and take up residence in the backbone.
“This is a major advance in our understanding of bone metastasis,” says Xiang Zhang, a cancer biologist at Baylor College of Medicine in Houston who was not involved with the new study.
In people with metastatic breast cancer, some 70 percent experience subsequent bone cancer. And of the bones in the skeleton, cancer cells preferentially seek out vertebrae. For these patients, “spine metastases are one of the most common complications,” Greenblatt says, “and one of the most dreaded.” Tumors that take root in the spine can crush the spinal cord, which houses nerve bundles crucial for body sensation and movement. Such damage can hamper people’s ability to walk and control their bladder and bowels, and shorten their life spans.
Doctors have known for decades that some cancers preferentially seek out the spine, Greenblatt says, but no one has had a good explanation for why. One idea proposed in 1940, that actions like coughing jolt blood off course and somehow send cancerous cells to the vertebrae, still hangs on today. It’s what Greenblatt learned when he was a medical student. But for him and his team, “that didn’t make sense to us scientifically.”
What did end up making sense was stem cells. The researchers had a hunch that stem cells inside vertebral bones differed from those in other sites in the skeleton, like the long bones in the arms and legs. In the lab, that’s just what they found. Greenblatt’s team pulled out a population of stem…
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