Oncogenes are dominant; mutation in only one of the alleles is sufficient to make cells evade apoptosis and continue proliferating. In cancer, proto-oncogenes can be mutated, resulting in gain of function. When a proto-oncogene is activated, it is then referred to as an oncogene. Oncogenes can be activated by several ways, including mutation, epigenetic regulation, chromosomal translocation, or gene duplication. The result is hyperactive or highly expressed oncogenes that overcome the functions of tumor suppressor genes and promote cancer development. Examples of oncogenes include MYC, RAS, TGF-B, HER2, ERK, and others.