Researchers might now have an idea of how breast cancer spreads to other parts of the body and metastasizes, which means they are one step closer to finding out how they can stop that process, according to Forbes.

Based on studies of live mice and human tissue, the researchers found a protein called endosialin that helps move molecules from one part of the body to another through the blood stream. That movement through the body is what can cause metastasis as generally non-deadly breast cancer cells are swept into other parts of the body where new tumors form.

That means that if doctors are able to find a way to prevent endosialin production, they might be able to stop new tumors from forming from run-away breast cancer cells. And they might even be able to stop women who already have breast cancer from having it come back—there was more endosialin in the bodies of women who had breast cancer recurrence than the women who didn’t.

Check out Forbes to see how the researchers were able to confirm (in mice and humans) that the protein played such an important part in the spread of cancer.