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.
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.
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 cells from mice vertebrae distinctly unlike ones collected from long bones. These new stem cells switched on a separate set of genes and behaved differently in experiments, the researchers found.
The cells traveled to the mini vertebra nearly twice as often as they did to the little long bone, as if lured by a cancer-calling Pied Piper. It’s an elegant way to show that “tumor cells preferentially come to the organoid and not to the organoid of the long bone,” Carmeliet says.