Why does breast cancer spread to the spine? Scientists finally have an answer

In a major breakthrough, Matthew Greenblatt and his colleagues from Weill Cornell Medicine, New York City have reportedly unravelled a long-standing mystery that why some cancers break away from their site of origin, journey through the bloodstream and take up residence in the backbone. The report was published last month in Nature.

Greenblatt said in 70% cases, people with metastatic breast cancer subsequently develop bone cancer, and the cells actually preferentially metastasize to the spine. For these patients, “spine metastases are one of the most common complications and one of the most dreaded.” ScienceNews quoted Greenblatt as saying. The team has found a new kind of stem cell that might be involved in this process, he added.

“This is a major advance in our understanding of bone metastasis,” ScienceNews quoted Xiang Zhang, a cancer biologist at Baylor College of Medicine in Houston who was not involved with the new study, as saying.

The report said the metastatic tumors after spreading in the spine can crush the spinal cord, which houses nerve bundles crucial for body sensation and movement. This spinal cord damage can hamper people’s ability to walk and control their bladder and bowels, and shorten their life spans.

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Greenblatt said for decades, doctors knew that some cancer cells preferentially seek out the spine, but no one has had a good explanation for why. 

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. 

The Experiment

In a key experiment, the researchers transplanted spinal stem cells into one hind leg of mice and long bone stem cells into the other. Each transplant formed miniature bones in the animals’ bodies — a tiny vertebra on the right, and a bit of long bone on the left. Then, they injected breast cancer cells into the mice.

The researchers noted that cells travelled 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, the report said.

The report further said the newly identified spinal stem cells, found in both mice and humans, secrete a protein called MFGE8 that acts as a tumor attractant, drawing cancer cells to spinal tissue. 

The protein may not be the only factor involved, Greenblatt said, “but it’s an important one in driving tumor cells to the spine.”

It’s possible that blocking MFGE8 could prevent or treat spine metastasis. “I think it’s definitely worth further investigation,” Zhang said. But, he noted, it’s still too early to know what the therapeutic implications may be.