Assay of the c-erbB-2 oncogene encoded protein by ELISA and

SUMMARY. The c-erbB-2 gene is amplified in a wide variety of different adenocarcinomas. Generally, gene amplification correlates with increased expression of the c-erbB-2 oncoprotein. Previous assays for the c-erbB-2 oncoprotein have been qualitative or semi-quantitative. In this investigation using human breast cancers, c-erbB-2 oncoprotein levels as measured by enzyme-linked immunosorbent assay (ELISA) correlated significantly with semi-quantitation by immunocytochemistry (r=0'843, P<O'OOOl, n=97). The cut-off point for the ELISA which gave the strongest agreement with immunocytochemistry was 15 units/JLg protein. It is concluded that detection of c-erbB-2 oncoprotein by ELISA is quantitative and objective. Additional key phrases: method comparison; cut-off points It is now generally agreed that most human cancers result from the activation of cellular (c)-oncogenes and inactivation of suppressor genes. One of the most widely investigated c-oncogenes in human cancer is c-erbB-2 (also known as neu or HER-2). This gene is amplified in 10-30070 of most human adenocarcinomas, including breast cancer. 1 In breast cancer amplification of the c-erbB-2 gene usually correlates with increased expression of the protein product although about 10 % of tumours have increased oncoprotein levels without apparent gene amplification.? In 1987, Slamon et al. ' reported that amplification of the c-erbB-2 gene correlated significantly with poor prognosis in breast cancer. These results were later confirmed by many groups and in addition high levels of the c-erbB-2 encoded protein were also found to correlate with poor outcome in patients with breast cancer. I More recently, either amplification or increased expression of c-erbB-2 gene has been associated with poor prognosis in ovarian.? lung? and gastric cancers.? Thus, c-erbB-2 may be a prognostic marker for many different types of adenocarcinoma. Previous assays for the measurement of c-erbB-2 gene activation have included Souther