In 1986, the human HER2 proto-oncogene was cloned. HER2 is also called neu and erbB2. This finding established the HER2 oncogene hypothesis for the development of some human cancers.

The subsequent two decades have brought about an explosion of information about the biology of HER2 and the Human Epidermal Growth Factor Receptor (HER) family.

Numerous experimental models now solidly support the hypothesis that HER2 overexpression promotes tumorigenesis and the finding of HER2 amplification and overexpression in many human breast cancers and its link with the biology of this disease now clearly implicate this oncogene in the pathogenesis of this type of human cancer.