This document discusses three genes - COX2, HB-EGF, and ST6GALNAC5 - that are involved in breast cancer spreading to the brain. COX2 and HB-EGF help breast cancer spread to the lungs, while ST6GALNAC5 causes cancer cells to have a sticky outer layer, allowing them to remain in brain blood vessels long enough to enter brain tissue. Researchers injected human breast cancer cells into mice and found that ST6GALNAC5 makes the cells sticky and able to infiltrate the brain by coating them chemically. This could provide targets for drugs to block breast cancer's ability to metastasize to the brain.