Human prostate tissue antigens defined by murine monoclonal antibodies.

BALB/c mice were hyperimmunized against a membrane preparation derived from a pool of transurethral resection specimens which included three benign prostatic hyperplasia and one prostate adenocarcinoma tissue samples. The activated lymphocytes were fused with the NS-1 mouse myeloma cell line, and supernatants from immunogen-reactive hybridomas were screened for antibody binding activity using a solid-phase radioimmunoassay against the Calu-1 human lung adenocarcinoma cell line and several membrane preparations derived from various normal human tissues. Hybridoma cultures secreting antibodies which did not appear cross-reactive were doubly cloned by limiting dilution and screened against a large panel of membrane preparations derived from normal prostate, benign prostatic hyperplasia, and prostate adenocarcinoma tissues as well as samples obtained from a variety of normal human tissues. The monoclonal antibodies were also evaluated against 24 normal, virally transformed, and malignant human cell lines. Two monoclonal antibodies were isolated which demonstrated a restricted binding activity to prostate antigens and were not widely cross-reactive with nonprostate normal tissues or cell lines. These antibodies were designated TURP-27 (IgG3, k) and TURP-73 (IgG2a, k). Both of these monoclonal antibodies were reactive against formalin-fixed, paraffin-embedded tissues in the immunoperoxidase assay and were subsequently tested against a variety of normal, hyperplastic, and malignant human tissues. These studies indicated that TURP-27 may be directed against a new prostate organ-associated marker and that TURP-73 is directed against an antigen expressed on prostate and a limited number of other tissues.

Immunohistochemical localization of prostate carcinoma-associated antigens.

The immunoperoxidase technique was used to study the localization and distribution of antigens reactive with two monoclonal antibodies, D83.21 and P6.2, produced against cultured prostate tumor cells, in formalin-fixed, paraffin-embedded histological sections of human tissues. Monoclonal D83.21 reacted with 11 of 19 (58%) primary prostate carcinomas and 1 of 6 (17%) metastatic tumors, whereas monoclonal P6.2 reacted with 14 of 19 (68%) primary and 4 of 6 (67%) metastatic prostate tumors. Neither antibody reacted with five primary prostate tumors and one metastatic prostate tumor. In some tumor cells, the antigens recognized by these monoclonals were localized in either the cytoplasm or cell membrane, while in other tumor cells, both diffuse cytoplasmic and membrane or focal staining patterns were observed. In addition to the variable staining patterns, antigenic heterogeneity was also noted within most prostate tumors examined. Two types of staining variability were observed: (a) tumor cells in one area of the tissue section stained positive, but in another area they did not react with the antibody; and (b) both stained and unstained tumor cells were adjacent to each other. These results would suggest that a panel of monoclonals will be required to detect the different subpopulations of prostate tumor cells. Neither antibody reacted with 6 normal or 12 benign prostate tissues, nor any of a variety of other normal human tissues except for staining of the proximal tubules of normal kidneys. The antigen detected by P6.2 demonstrated a wider tissue distribution being found on bladder, breast, lung, and pancreatic tumors, whereas the antigen recognized by D83.21 was restricted to prostate and bladder carcinomas. These antibodies may have clinical applicability for the identification of prostate tumor cells in biopsy specimens and for immunohistopathological classification of prostate carcinomas.