Scientists have successfully blocked breast cancer cells from entering and hiding in the bones of mice, where the disease can survive chemotherapy. Researchers at Duke University have devised a method of flushing breast cancer cells out of bone marrow in mice, making them easier to eradicate.The findings, published in the journal Science Translational Medicine, heralds the prospect of similar trials in humans and has prompted hopes that one of the most devastating characteristics of breast cancer can be prevented."Most often the site of the metastasised cancer is in the bone. Now we know how it is getting in."Breast cancer can return years after therapy and spread to other parts of the body.Previous research suggests bone marrow may offer a haven from chemotherapy, meaning breast cancer cells can lie dormant for an extended period. Up to now, however, little has been known about how metastatic breast cancer cells enter and hide in bones.Using real-time microscopy techniques, the Duke University team tracked the migration of breast cancer cells through the bone marrow of mice and identified E-selectin, the protein that allows cancer cells to enter the bone marrow, and CXCR4, the protein that anchors them to the bone and allows the malignant cells to hide.Treatment with an E-selectin inhibitor blocked cancer cells from entering the bone, and a CXCR4 inhibitor forced them back out into the bloodstream.Dorothy Sipkins, an associate professor at Duke, said: "Studies have found that breast cancer can be caught early and treated, and patients can have no signs of disease. Then five, 10 or even 15 years later, a patient can relapse."We also identified an important mechanism that allows breast cancer cells to remain anchored in the bone marrow."In the mouse, our findings could offer new strategies to intervene at the molecular level before dormant cells can take hold and cause relapse."The E-selectin inhibitor used in the mice study, called GMI-1271, is already being used in separate human clinical trials.Sipkins said she hoped to conduct additional studies in mice to better understand how breast cancer cells migrate through the body before moving on to human studies. ..