Epidermal growth factor (EGF) binding by normal and neoplastic human renal tissue

The identification of EGF mRNA in the renal tissue, that of TGFα in human renal cell carcinoma (RCC) and that of EGF receptor (EGF-R) obtained with monoclonal antibodies in a large number of RCC cell lines prompt us to study the EGF-R in normal human kidney and in human RCC in order to evaluate whether the concentration of the EGF-R could be regarded as a prognostic parameter. Time course of EGF binding at 25°C reached a plateau within 30-40 minutes and was stable for up to 120 minutes; competition experiments revealed that only cold EGF was able to inhibit the binding, whilst FSH, Insulin, Calcitonin did not compete. Saturation analysis of EGF-R, performed by incubating the membranes with 0.015-10 nM 125 I-EGF in the presence and in absence of 100 fold excess of cold EGF revealed that both normal human kidney and human RCC had high affinity binding sites of EGR-R (Kd = 0.8 ± 0.13 nM and 1.9 ± 0.17 nM respectively). The binding capacity of EGF-R was significantly higher in human RCC than in human normal renal tissue (320 ± 192 vs 16.7 ± 9.8 fmol/mg protein), either as results of an over expression of c-erb B protooncogene in the tumor or as a result of EGF-R synthesis by estradiol in human RCC. Preliminary results on the correlation of EGF-R with ER in paired samples obtained from human RCC and peritumoral normal tissue demonstrated a trend to an inverse correlation between these two parameters.