All of our cells rely in sugar for energy. Cancer cells just need more sugar than normal cells. This is because many cancers only use some of the available energy making processes, so they get less energy per sugar molecule.
Using kidney cancer as a model, researchers have identified a target that can starve the cancer cells of the sugar they need. The target (GLUT1) is a transport protein that helps cells to absorb the sugar glucose from their surroundings. When the transporter is blocked, the cells starve to death. Normal cells are not hurt by the treatment because they don't need as much sugar to survive.