Breast cancer is the most common tumor in women and was diagnosed in more than 184,000 U. S. patients in 2008, according to estimates from the National Cancer Institute.

Recent study revealed the hand of three genes in aiding cancer cells to enter brain tissue. Earlier studies have shown that two of the genes, COX2 and HB-EGF help cancer spread to the lungs. Researchers found that the third gene ST6GALNAC5 helped the cancer to penetrate the brain.

Using animal models, researchers found that COX2 and HB-EGF made the cancer cells more mobile and more invasive whereas ST6GALNAC5 appears to cause a chemical reaction that coats the outside of breast cancer cells. ST6GALNAC5 make the outer coat of cancer cells sticky. This coating allow them to linger in tiny blood vessels in the brain long enough to seep through and enter brain tissue.

Joan Massague of Memorial Sloan-Kettering Cancer Center in New York and a Howard Hughes Medical Institute investigator said: "Our research sheds light on the role these genes play in determining how breast tumor cells break free and, once mobile, how they decide where to attack."

Massague added that it may be possible to find drugs that can block this process.