The gene for HER-2/neu (also known as c-erbB-2) oncoprotein was cloned and characterized by Akiyama et al in 1986.1 It is an approximately 185 kD transmembrane glycoprotein which is structurally similar to epidermal growth factor receptor (EGFR). The protein is associated with tyrosine kinase activity similar to that of several growth factor receptors, and to that of the transforming proteins of the src family. The coding sequence is consistent with an extracellular binding domain and an intracellular kinase domain. This suggests that HER-2/neu may be involved in signal transduction when bound by a growth factor, stimulating mitogenic activity.1
The HER-2/neu oncoprotein is expressed in the cytoplasmic membrane at a level detectable by immunohistochemistry in up to 20 percent of adenocarcinomas from various sites. Between 15 and 30 percent of invasive ductal cancers are positive for HER-2/neu.2 Almost all cases of Paget’s disease of breast3 and up to 90 percent of cases of ductal carcinoma in situ of comedo type are positive.2 The immunohistochemical detection of HER-2/neu protein overexpression is also used as an aid in determination of patients for whom Herceptin therapy is indicated.4
Package Inserts
