A tumor-suppressing gene involved in controlling cellular growth; inactivation of this type of gene leads to deregulated cellular proliferation, as in cancer.

A number of antioncogenes have been identified. Their deletion, mutation, or inactivation opens the gateway for further cellular harm. Typically, the shut-off of an antioncogene results first in cell proliferation. In the presence of one or more oncogenes, this proliferation is accelerated and the cells become invasive.