A new monoclonal antibody for detection of EGF‐receptors in western blots and paraffin‐embedded tissue sections

The prognostic significance of the epidermal growth factor receptor status (EGF‐R‐status) for certain human tumors requires the development of antibodies useful for clinical application. We used purified receptor preparations to generate monoclonal antibodies immunoreactive with the EGF‐R purified from placenta membranes and A431 tumors. Four of the hybridomas contained antibodies (R2, R3, R5, and R9) which recognized both antigens. Antibody R3 was shown to display the following properties: it binds with a K_D value of about 10⁻⁹–10⁻¹⁰ M to the receptor, a half maximal inhibition of EGF‐binding is achieved at 5 × 10⁻⁸ M, and in Western blots of cell membranes R3 specifically detects the EGF‐R at 0.1 μ/ml. R3 inhibits EGF‐dependent clonogenic growth of NRK cells and completely blocks EGF stimulated autophosphorylation of the receptor. Moreover, R3 also detects EGF‐R in paraffin‐embedded tissue sections taken from human salivary gland, term placenta, and adult skin and mammary carcinomas. Thus, R3 can be used in retrospective diagnostic clinical studies and might help to develop new immunotherapeutic intervention.