1) Genes in the body that can suppress or block the development of cancer.

2) Genes that normally restrain cell growth but, when missing or inactivated by mutation, allow cells to grow uncontrolled.

3) A tumor suppressor gene directs the production of a protein that is part of the system that regulates cell division. The tumor suppressor protein plays a role in keeping cell division in check. When mutated, a tumor suppressor gene is unable to do its job, and as a result uncontrolled cell growth may occur. This may contribute to the development of a cancer.