Tumor suppressor genes are genes that regulate the growth of cells. When these genes are functioning properly, they can prevent and inhibit the growth of tumors.
When tumor suppressor genes are altered or inactivated (due to a mutation), they lose the ability to make a protein that controls cell growth. Cells can then grow uncontrolled and develop into a cancer.
There are 3 main types of tumor suppressor genes. One type tells cells to slow down and stop dividing. Another type is responsible for fixing damages in DNA that can happen when cells divide. A third type is responsible for telling cells when to die, a process called apoptosis.