robert2cane points out a promising study from Cornell University about controlling the spread of cancer. There are many treatments for an isolated tumor, but once cancer cells reach the bloodstream and start spreading through the body, it's much more difficult to control. The new research (PDF), led by Michael King, developed a compound that is able to target and eliminate cancer cells in the blood of mice. "When attempting to develop a treatment for metastases, King faced two problems: targeting moving cancer cells and ensuring cell death could be activated once they were located. To handle both issues, he built fat-based nanoparticles that were one thousand times smaller than a human hair and attached two proteins to them. One is E-selectin, which selectively binds to white blood cells, and the other is TRAIL. He chose to stick the nanoparticles to white blood cells because it would keep the body from excreting them easily. This means the nanoparticles, made from fat molecules, remain in the blood longer and thus have a greater chance of bumping into freely moving cancer cells. There is an added advantage. Red blood cells tend to travel in the center of a blood vessel, and white blood cells stick to the edges. This is because red blood cells are lower density and can be easily deformed to slide around obstacles. Cancer cells have a similar density to white blood cells and remain close to the walls, too. As a result, these nanoparticles are more likely to bump into cancer cells and bind their TRAIL receptors."