No abstract

No abstract

Monoclonal antibodies (MAbs) were produced against a highly purified preparation of prostate secretory protein (PSP) isolated from normal seminal plasma. Fifteen antibodies were selected for further evaluation based on their strong reactivity and specificity for PSP. All the MAbs had a specificity for prostate epithelial cells and none reacted to any of a variety of normal tissues as determined by immunoperoxidase staining. Six of the MAbs were selected for further immunohistochemical evaluation based on their ability to recognize different antigenic determinants. Using competitive binding immunoassays, a variety of overlapping specificities were observed with at least 2 distinct epitopes identified. Although some staining variability was noted, the 6 antibodies, in general, gave the same pattern of tissue reactivity. Both the normal prostate and the benign prostate hyperplastic ductal epithelial cells stained intensely, with 78 to 100% and 50-100% of the cells staining, respectively. The number and often the staining intensity of the tumor cells decreased as the tumor became more undifferentiated. Approximately 40 to 100% and 15 to 70% of the tumor cells stained in the moderately-differentiated and well-differentiated carcinoma tissues, respectively, whereas either no staining was observed or less than 20% of the tumor cells stained in the poorly-differentiated and undifferentiated tumors. Most of the metastatic prostate tumors showed either no staining or scattered staining in a few cells (i.e., less than 20%).

A prostate carcinoma-associated antigen recognized by MAb TURP-27 was characterized immunohistochemically and biochemically. TURP-27 antigen was found localized in the cell membrane and cytoplasm of the ductal epithelial cells of normal (10%), benign (75-100%) and malignant (20-100%) prostate cells. Fetal prostate tissues were also found to express the TURP-27 antigen, suggesting expression early in development. This antigen was not expressed by non-prostate tumors examined, but significant cross-reactivity was observed in myelinated nerves while minor cross-reactivity was seen in certain lymphocyte subsets, cells in the adrenal medulla and chief cells of stomach. Immunoblotting and biochemical data demonstrated that the TURP-27 antigen is a sialic-acid-containing glycoprotein complex with major molecular species in prostate tissues of 310-250, 180, 140, 115, 95-90, 69, and 40- to 35-kDa. Immunoblotting patterns similar to those observed for prostate tissues were also seen in CNS extracts with the exception of the 69 and 40- to 35-kDa proteins. This prostate carcinoma-associated sialoglycoprotein complex (PAC) recognized by MAb TURP-27 is likely to represent a novel tumor antigen expressed by prostate tumors.

Prostate specific antigen (PSA) is the most useful serum marker for following the disease status of prostate cancer patients after therapy. While PSA is felt to be an organ specific marker, lack of PSA expression in the seminal vesicles has not been adequately established. MHS-5 is a monoclonal antibody which recognizes an epitope on seminal vesicle specific antigen. Our objectives were to define PSA expression by the seminal vesicles, to determine whether MHS-5 could serve as an adjunct in the diagnosis of seminal vesicles invasion by carcinoma of the prostate, and to determine whether carcinoma, having invaded seminal vesicles would retain its expression of PSA and other prostate markers. Using an immunoperoxidase procedure, we studied thirteen seminal vesicles without histologic evidence of prostate cancer invasion and five seminal vesicles with locally invasive cancer. No seminal vesicles expressed PSA, whereas prostate cancer invading the seminal vesicles expressed PSA in all cases. MHS-5 expression was more variable. Only two of five cases of locally invasive tumor demonstrated seminal vesicles expression for MHS-5. Our findings further support the specificity of PSA. While MHS-5 may be helpful in delineating seminal vesicles in some instances, it is not a consistently reliable marker.

The biotin-avidin immunoperoxidase assay was used to evaluate the expression of several prostate carcinoma-associated markers in formalin-fixed paraffin-embedded tissue sections of three human prostate nude mouse heterotransplant lines PC-82, PC-EW, and PC-EG. In addition to monoclonal antibodies to PSA and PAP, monoclonal antibodies to five other potentially useful markers for prostate carcinomas (TURP-27, Leu-7, 7E11-C5, PSP-19, and PD41) were tested. Tissues from two or more transplant passages were evaluated. The human prostate target antigens were found to be expressed by one or more of the three heterotransplant lines. The PC-82 and PC-EW lines were the most efficient in terms of expression of multiple prostate carcinoma-associated markers and percentage of tumor cells positive for a given prostate antigen. The staining pattern of each marker, in terms of staining intensity, number of tumor cells stained, and staining location, i.e., membrane, cytoplasmic, or ductal secretions, was similar to what has been observed in tissue sections from human prostate carcinomas. The lack of an appropriate model for evaluating the preclinical potential of these Mabs (especially TURP-27, PSP-19, and PD41) makes the findings of this study of considerable importance, and suggests that these human prostate xenografts may be useful models for exploring the diagnostic and therapeutic potential of these anti-prostate carcinoma monoclonal antibodies.