FLOW CYTOMETRIC DETECTION AND QUANTITATION OF THE EPIDERMAL GROWTH-FACTOR RECEPTOR IN COMPARISON TO SCATCHARD ANALYSIS IN HUMAN BLADDER-CARCINOMA CELL-LINES

The epidermal growth factor receptor (EGFR) is considered a tumor-rela ted marker with potential diagnostic and prognostic value. In order to assess the sensitivity of flow cytometry to detect EGFR and to quanti fy receptors objectively, two human bladder carcinoma cell lines with different urothelial differentiation, RT4 and J82, were grown in vitro , and their membrane EGFR content was measured by flow cytometry. Expo nential monolayers showed decrease of EGFR content after 20 min pulses with 10 ng/ml EGF in medium, as detected with the antibody EGFR1 in a double staining technique with propidium iodide for DNA evaluation. F urther decrease of green fluorescence intensity was seen in cells cons tantly exposed to EGF. Absolute receptor numbers were determined by Sc atchard analysis with radioactive EGF and resulted in relatively low r eceptor numbers for both cell lines (similar to 3-4 x 10(4) EGFR/cell) , as well as one affinity class. These findings could be matched by ab solute receptor quantification by flow cytometry, adding beads with de fined antigenic sites (Quantum Simply Cellular, Microbead Corporation) to the cell suspension for staining. Our data suggest that flow cytom etric EGFR detection and quantitation may be supplied to in vivo tumor samples and that measurements by multiparameter analysis may define s ubpopulations valuable for tumor diagnosis and judgment on tumor progr ession. (C) 1994 Wiley-Liss, Inc.