ELISA for quantitation of serum C-erbB-2 oncoprotein in breast cancer patients

C-erbB-2 is a protooncogene that is overexpressed in various cancers, either due to its amplification and/or increased transcription, and has been associated with more aggressive disease and a poor clinical prognosis in 20-30% of patients with breast cancer. Besides the prognostic factors such as tumor size, tumor grade, lymph node status, etc., which are significant in the management of breast cancer, C-erbB-2 level might also serve as an additional factor. Immunohistochemistry is the most frequently used method to study the expression of C-erbB-2 in breast cancer. We have generated a panel of monoclonal antibodies against GerbB-2 oncoprotein with a view to evaluate their application for the diagnosis and therapy of breast cancer. In the present study, a simple, quantitative sandwich ELISA has been developed that uses two monoclonal antibodies directed against the extracellular domain of C-erbB-2 product, designated as CIBCgp185 as the capture antibody and CIBCHER-2 as the detector antibody. GerbB-2 protein, isolated from BT474 cells, a human breast carcinoma cell line with high expression of C-erbB-2 and purified by Concanavalin A-Sepharose 4B affinity chromatography and HPLC has been used to develop the ELISA procedure. Sera samples of 150 healthy women donors and of 300 breast cancer patients with different histological types of malignancies have been analysed. The control women had serum GerbB-2 in the range of 4.0-13.2 ng/mL, whereas the 300 breast cancer patients studied had a range of 4.8-75.2 ng/mL with a cut off value of 13.8 ng/mL. Our study showed that 18.6% of breast cancer patients had elevated levels of circulating C-erbB-2. These results might suggest that the serum C-erbB-2 level can be used as a potential tumor marker for breast cancer and that the Sandwich ELISA procedure might serve as an excellent alternative to immunohistochemistry in the near future.