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; pr ostate cancer is resistant to the common anticancer drugs. The only us eful therapy for metastases involves diminishing testosterone levels b y 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 canc er cells. The MAbs available either do not react uniformly with prosta te cancer cells or react with normal tissues. Thus, a new MAb is neede d. Purpose: The goal of this study was to isolate an MAb that reacts w ith an antigen present on the surface of prostate cancer cells. Method s: A strain of prostate cancer cells was isolated from a prostate canc er specimen, grown for 2-4 weeks in short-term culture, and used to im munize BALB/c mice. Hybridomas were then prepared by using spleen cell s from the immunized mice. One hybridoma produced an MAb (PR1) that re acted with prostate cancers. Results: MAb PR1 is an IgM(kappa) subtype that reacts uniformly with the surface of most (25 of 26) adenocarcin omas of the prostate. It also reacts with the surface antigen on norma l prostate epithelial cells and on cells from benign prostatic hyperpl asia. MAb PR1 reacts with a limited number of normal tissues including a subset of principal cells located in the collecting ducts of the ki dney. Conclusion: We conclude that MAb PR1 reacts with a differentiati on antigen present in normal prostate and that this antigen continues to be expressed on almost all adenocarcinomas of the prostate. Implica tions: This antibody may be useful for the diagnosis of or therapy for prostate cancer.