NARRATOR: How does a gene that causes cancer, known as an oncogene, work? Cells have genes that direct the formation of receptor molecules. Receptor molecules are like antennae sitting on the cell's surface. When they receive growth signals from the outside, they send a message to the cell nucleus that it's time to divide.
The oncogene causes a slight difference in the receptor molecule. Like an accelerator pedal stuck permanently to the floor, the receptor keeps signaling the cell to divide, whether or not the receptor is getting that message. The more oncogenes there are, the more receptors present that are sending a stream of signals for the cell to reproduce.
But how does cancer spread? How do cells escape into a person's blood stream and attach themselves in other parts of the body? First, the cells fasten to the membrane around the blood vessel. Then, they use a strong chemical to work their way through the tough membrane into the circulatory system, which carries them to new tissues and organs.
Scientists understand the molecules that accompany each of these steps, and are trying to develop drugs to stop them. Other therapies are aimed at shutting down the receptor molecules to stop the cancer from growing.