Written by Kelly A. Hogan, University of North Carolina at Chapel Hill

When discussing the cell cycle and cancer causing genes, I often use an analogy to cars. There are two ways to lose control of a car: the gas pedal can get stuck down or the brakes will not work when engaged. In either case, the car speeds along without driver control. In this anology, tumor supressors are like brakes, which normally prevent the cell cycle from losing control (preventing cancer). When mutated, the brakes are lost and the cell divides out of control. Proto-oncogenes are like the gas pedal, in that they promote cell division. When mutated, like a gas pedal stuck down, they cause unregulated cell division.