E4, a new monoclonal antibody identifying a human prostatic cell surface antigen

The monoclonal antibody E4 (IgG2a, kappa) was raised by immunizing mice with dispersed cells obtained from human benign prostatic hyperplasia (BPH). The antibody identifies an antigen abundantly expressed in normal prostate epithelial cells, in benign epithelial prostatic cells and in well- and moderately well differentiated adenocarcinomas of the prostate, whereas poorly differentiated prostatic adenocarcinomas display somewhat less expression. Investigation of the human prostatic adenocarcinoma cell line DU 145 revealed E4 immunoreactivity localized to the cell surface. SDS-PAGE analysis under reducing conditions demonstrated an approximate molecular weight of 70,000 for the antigen. The highly specific reactivity with prostate tissue, as well as intense surface staining, especially in well- and moderately well differentiated prostatic adenocarcinomas, makes the E4 antibody a useful immunohistochemical marker and a possible candidate for future immunoscintigraphy and/or targeted radiotherapy.