An oncogene is a mutated gene that contributes to the development of a cancer. In their normal, unmutated state, onocgenes are called proto-oncogenes, and they play roles in the regulation of cell division. Some oncogenes work like putting your foot down on the accelerator of a car, pushing a cell to divide. Other oncogenes work like removing your foot from the brake while parked on a hill, also causing the cell to divide.
Within every cell in our body is a class of genes known as proto-oncogenes. Proto-oncogenes play important roles in controlling cell division and cell death during our growth and development. However, if a proto-oncogene becomes mutated, or the cell makes extra copies of the proto-oncogene, it can become hyper-activated and lead to the appearance of uncontrolled cell division. This therefore contributes to the development of a cancer cell from a normal cell. Once a proto-oncogene is activated by a mutation, we then refer to it as an oncogene. So it's the activation of oncogenes that's one type of genetic lesion that contributes to the development of a tumor.Daphne W. Bell, Ph.D.