Enzyme-linked immunosorbent assay of c-erbB-2 oncoprotein in breast cancer

Amplification or increased expression of the c-erbB-2 gene has previously been reported to be a prognostic marker for breast cancer. Gene amplification is usually measured by Southern blotting, whereas increased protein expression is usually detected by immunocytochemistry. We measured c-erbB-2 protein with an enzyme-linked immunosorbent assay (ELISA). High concentrations of oncoprotein were found in 25 of 161 (16%) primary breast cancers and in 3 of 6 (50%) breast cancer metastases. High concentrations were not found in normal breast tissue or benign breast tumors. In the primary cancers, high concentrations of c-erbB-2 protein were found more frequently (a) in estrogen receptor-negative tumors than in estrogen receptor-positive tumors, (b) in progesterone receptor-negative tumors than in progesterone-positive tumors, and (c) in axillary node-positive cancers than in node-negative cancers. Patients with tumors containing high amounts of the c-erbB-2 protein had a significantly shorter (P less than 0.001) disease-free interval and overall survival rate than did patients with low amounts. We conclude that assay of c-erbB-2 protein by ELISA is simple, rapid, and quantitative and offers important prognostic information in breast cancer.