HER2

ERBB2

A gene on chromosome 17q11.2-q12 that encodes a member of the epidermal growth factor receptor (EGFR) family of receptor tyrosine kinases. ERBB2 has no ligand-binding domain and thus cannot bind growth factors; it does, however, bind to other ligand-bound EGF receptor family members, forming a heterodimer, stabilising ligand binding and enhancing kinase-mediated activation of downstream signalling pathways (e.g., those involving mitogen-activated protein kinase and phosphatidylinositol-3 kinase).
Molecular pathology
ERBB2 amplification and overexpression commonly occurs in breast and ovarian cancers.

HER2

Human epidermal growth factor receptor 2, a receptor that plays an essential role in cell proliferation and differentiation. It is a member of a family of transmembrane tyrosine kinases. The 20 to 25 percent of breast cancers that over-express HER2 have a high rate of recurrence in the first two or three years after surgery. The HER2 gene is on the short arm of chromosome 17. Over-expression of this gene increases the malignancy of affected cancer cells, enhancing growth and proliferation and increasing their metastatic tendency. The monoclonal antibody drug trastuzumab (Herceptin) which blocks this receptor is effective in reducing the dangers of HER2-expressing breast cancers.