A putative prostate cancer marker called PC-1 has been identified in prostate cancers but not benign hyperplasia or normal prostate. Matritech scientists have produced specific anti-PC-1 monoclonal antibodies, selected by immunofluorescent nuclear antigen localization on the PC-1-positive prostate tumor cell line LNCAP and 1-D immunoblots against LNCAP-extracted nuclear matrix proteins. Following further characterization of PC-1- specific antibodies by 2-D immunoblotting on nuclear matrix extracted from prostate cancer tissue, the goal of this SBIR Phase I study is to evaluate the tissue specificity of PC-1 by immunohistochemical localization of PC-1 antigen in frozen sections of prostate tumor tissue, benign hyperplastic and normal prostate, as well as a panel of non-prostate tissues. Antibodies selected for their ability to distinguish between cancerous and benign/normal prostate tissue will be used to search for PC-1 protein in urine or serum from prostate cancer patients by two site immunoassay. If tissue localization of PC-1 can distinguish cancer patients from those with benign disease, or if PC-1 is detectable in either serum or urine, then an immunoassay based upon the detection of this protein could improve patients management or could aid in the early detection of prostate cancer.