Epidermal growth factor in the normal and neoplastic kidney and bladder.

Epidermal growth factor (EGF) is a cell-regulating polypeptide that appears important to the maintenance and function of some benign tissues and to the transformation and proliferation of certain malignancies. In humans the highest concentrations of EGF are found in the urine. We investigated possible interactions between EGF and normal and neoplastic tissues of the urinary system with indirect immunohistochemical staining of paraffin-embedded tissue sections. A polyclonal antibody directed against mouse EGF but shown to react with human EGF was used in the assays. Positive staining was granular in nature and confined to the cytoplasm. Staining of the renal parenchyma (N = 5) was observed in the epithelium of the proximal and distal tubules and the collecting ducts. There was staining of clear cell (N = 6) and papillary (N = 3) carcinomas of the kidney. Staining of the normal urothelium (N = 5) was limited to superficial cells. All transitional cell (N = 21) and squamous (N = 2) carcinomas of the bladder stained. Subjectively, the staining intensity of the transitional cell carcinomas correlated inversely with tumor differentiation. In light of evidence that internalized, receptor-bound EGF is rapidly degraded, the striking immunohistochemical demonstration of cytoplasmic EGF suggests active synthesis. EGF synthesized by urothelial and renal carcinomas may be involved in an autocrine mechanism of malignant proliferation.