HER-2/neu Oncogene Amplification Determined by Fluorescence In Situ Hybridization

The proto-oncogene HER-2/neu (C-erbB-2) has been localized to chromosome 17q and encodes a transmembrane tyrosine kinase growth factor receptor. The name for the HER-2 protein is derived from human epidermal growth factor receptor (EGFR) because it features substantial homology with the EGFR (1 ,2 ). HER-2/neu gene amplification has been associated with the development of breast cancer in animal models (1 ). The HER-2/neu protein is a component of a four-member family of closely related growth factor receptors including EGFR or HER-1 (erb-B1) , HER-2 (erb-B2) , HER-3 (erb-B3) , and HER-4 (erb-B4) (3 ). In addition to its association with disease outcome in gastrointestinal, pulmonary, genitourinary, and other neoplasms, amplification of the HER-2/neu gene or overexpression of the HER-2/neu protein has been identified in from 10 to 34% of breast cancers (4 –5 ). The techniques used to evaluate HER-2/neu status in breast cancer have included gene-based assays such as Southern and slot blotting, polymerase chain reaction methods, and, more recently, in situ hybridization featuring both fluorescent and nonfluorescent techniques (4 –5 ).