PR1--a Monoclonal Antibody That Reacts with an Antigen on the Surface of Normal and Malignant Prostate Cells

Background : The principal treatment for prostate cancer is surgery; prostate cancer is resistant to the common anticancer drugs. The only useful therapy for metastases involves diminishing testosterone levels by orchiectomy or administration of drugs, either of which may increase survival time. One approach to prostate cancer treatment is to use a monoclonal antibody (MAb) to target cytotoxic substances to these cancer cells. The MAbs available either do not react uniformly with prostate cancer cells or react with normal tissues. Thus, a new MAb is needed. Purpose : The goal of this study was to isolate an MAb that reacts with an antigen present on the surface of prostate cancer cells. Methods : A strain of prostate cancer cells was isolated from a prostate cancer specimen, grown for 2–4 weeks in shortterm culture, and used to immunize BALB/c mice. Hybridomas were then prepared by using spleen cells from the immunized mice. One hybridoma produced an MAb (PR1) that reacted with prostate cancers. Results : MAb PR1 is an IgM k subtype that reacts uniformly with the surface of most (25 of 26) adenocarcinomas of the prostate. It also reacts with the surface antigen on normal prostate epithelial cells and on cells from benign prostatic hyperplasia. MAb PR1 reacts with a limited number of normal tissues including a subset of principal cells located in the collecting ducts of the kidney. Conclusion : We conclude that MAb PR1 reacts with a differentiation antigen present in normal prostate and that this antigen continues to be expressed on almost all adenocarcinomas of the prostate. Implications : This antibody may be useful for the diagnosis of or therapy for prostate cancer. [J Natl Cancer Inst 85: 1149–1154, 1993]