US scientists have unravelled breast cancer's migration to the lungs and bone marrow in a finding that may represent a new way to fight invasive cancer.
Why stray cancer cells choose certain organs to form secondary tumours and how to arrest this process, metastasis, which is the main cause of death in cancer patients, has always puzzled experts.
Scientists at the DNAX Research Institute in Palo Alto, California, Schering-Plough Corp's centre for immunology and bio-technology biology, said yesterday the answer lies in molecules called chemokines that carry messages between cells.
"This is the first very clear concept that provides a reason why tumours reside in certain places," Dr Jonathan Sedgwick, the director of the immunology unit, said. Chemokines are found in tissues such as the lung and lymph nodes and act as traffic policemen telling cells where to go.
If chemokines are increased in a particular tissue, the cell with the receptor, or partner, for that particular molecule is attracted to move in that tissue.
Most tumours express receptors for chemokines. In breast cancer tissue a receptor called CXCR4 is abundant.
The DNAX team looked for a chemokine that binds to it and found CXCL12.
"It turned out it is highly expressed in bone marrow, lymph nodes, liver and lungs into which breast tumours preferentially metastasise," Dr Sedgwick explained.
After identifying the chemokines, the researchers conducted studies on mice to try to block the receptor and stop the metastasis.
Their research is published in the science journal Nature.
They injected human breast tumour cells into the mice and treated the animals with an antibody that blocked the receptor from binding with the chemokine, preventing the metastasis.