BOSTON - Massachusetts General Hospital (MGH) researchers have identified a new - and surprising - mechanism by which breast cancer cells metastasize to the lymph nodes and lungs. By blocking this path, the researchers believe it may be possible to prevent the deadly spread of cancer cells from a primary tumor. The report from the MGH Cutaneous Biology Research Center (CBRC) appears in the February issue of Nature Medicine.
"We have identified a mechanism of breast cancer metastasis, I wouldn't say it's the mechanism because there may be several others," says Michael Detmar, MD, a dermatologist and principal investigator in the CBRC. "But this is certainly a major molecular mechanism of how breast cancer metastasizes to the lymph nodes."
Although cancer cells are believed to enter the lymph nodes through the lymphatic system-a multipurpose tangle of vessels-little is known about how tumor cells get from the primary tumor into the lymphatic system. In the February issue of Nature Medicine, Detmar, Mihaela Skobe, PhD, a postdoctoral fellow, and their colleagues report that the tumor cells appear to be exiting the tumor through a home-grown system of lymphatic vessels-one expressly cultivated by the tumor.
What is surprising about the discovery is that lymphatic vessels were not thought to exist in tumors. Part of the problem, says Detmar, is that until recently there has been no effective means of visualizing lymphatic vessels. Using a new method for imaging lymphatic vessels, he and Skobe observed networks of lymphatic vessels deep inside breast tumor masses grown in mice. Upon closer inspection, the vessels appeared to be carrying tumor cells.
Most striking, the number of lymphatic vessels inside the tumor appeared to be highly correlated with the number of metastatic cells in the lymph nodes and lungs, suggesting that the lymphatic vessels were providing a conduit for the flow of metastatic tumor cells.