NCIt definition : A gene that normally directs cell growth. If mutated or overexpressed in a dominant
fashion, it can release the cell from normal restraints on growth. It alone or in
concert with other changes, converts the cell into a tumor cell. Alterations can be
inherited or caused by an environmental exposure to carcinogens.;
Alternative definition : NCI-GLOSS: A gene that is a mutated (changed) form of a gene involved in normal cell
growth. Oncogenes may cause the growth of cancer cells. Mutations in genes that become
oncogenes can be inherited or caused by being exposed to substances in the environment
that cause cancer.;