Epidermal growth factor is not the major growth-promoting agent in extracts of prostatic tissue

Extracts of benign prostatic hyperplasia (BPH) contain a factor which is mitogenic for human foreskin fibroblasts in culture. Because of the similarity of BPH extract and epidermal growth factor (EGF) in stimulating quiescent fibroblasts to divide, it was of interest to determine if the prostate-associated growth factor competes for EGF receptor binding. BPH extract was found to compete poorly for 125I-EGF-receptor binding, did not influence the dissociation of cell-bound 125I-EGF and caused only a slight down-regulation of the EGF receptor. These findings indicate that EGF and BPH extract do not recognize the same receptor and that the major growth stimulating activity of BPH extract is not due to EGF.