Immunohistochemical localization of epidermal growth factor (EGF) and EGF receptor in human oral mucosa and its malignancy.

The immunohistochemical localizations of human epidermal growth factor (hEGF) and EGF receptor (EGFr) in oral tissues, including normal mucosa, leukoplakia and squamous cell carcinoma were examined by the use of monoclonal antibodies to hEGF and EGFr. In normal mucosa and leukoplakia, immunostaining of hEGF was limited to an underlying layer of connective tissue near the epithelium. The intensity of extracellular staining appeared to increase with the degree of epithelial malignancy and was eventually most striking in the stroma of invasive carcinoma. The epithelial cells in normal mucosa, leukoplakia, and squamous cell carcinoma showed negligible immunoreactivity for hEGF. Expression of EGFr appeared to be associated with the proliferative activity of cells and/or epithelial malignancy. In normal mucosa, anti-EGFr monoclonal antibody reacted only with the basal cell layer. In all sections of leukoplakia, the positive cells for EGFr were found in the prickle cell layer in addition to the basal cell layer. Most tumour cells in squamous cell carcinoma were strongly positive for EGFr. These findings indicate increased expression of hEGF and EGFr with malignancy. The characteristic localization of extracellular hEGF in the underlying connective tissue and in stroma of oral mucosal tumours suggests a possible epithelial-mesenchymal interaction in hEGF secretion.