Monoclonal antibody PD41 recognizes an antigen restricted to prostate adenocarcinomas

A monoclonal antibody (MAb) designated PD41 (IgG1k) was generated by hyperimmunizing BALB/c mice with a membrane preparation prepared from a moderately to poorly differentiated prostate carcinoma surgical specimen. The immunohistochemical reactivity of MAb PD41 was shown to be highly restricted to the ductal epithelia and secretions of prostate adenocarcinoma tissues. Sixty-five % of the prostate tumor specimens were stained with MAb PD41, whereas no staining of the fetal or benign prostate specimens was observed. PD41 reacted minimally with normal prostate tissues, with less than 1% of the epithelial cells staining. This MAb did not react with nonprostate carcinomas or to a variety of normal human tissues. Using both radioimmunoassay and immunofluorescent procedures, several cultured human tumor cell lines, human blood cells, and purified antigens to prostate-specific antigen and prostatic acid phosphatase also were found not to express the PD41 antigen. MAb PD41 also was shown to bind to the target antigen present in seminal plasma obtained from prostate carcinoma patients but not to seminal plasma from normal donors. Immunoblots of gel-separated components of prostate carcinoma tissue extracts indicate that the molecular weight of the proteins carrying the PD41 antigenic determinant can differ among individual tumors, ranging from Mr 90,000 to greater than 400,000. However, in seminal plasma from prostate cancer patients, the predominant component recognized by PD41 is the diffuse Mr greater than 400,000 band. It appears that this monoclonal antibody may recognize a prostate carcinoma-associated mucin-like antigen, which is preferentially expressed on prostate carcinomas, and therefore, may be a useful marker to distinguish benign prostate hyperplasia from prostate carcinoma.