Isolation and characterization of monoclonal antibodies specific for protein conformational epitopes present in prostate-specific membrane antigen (PSMA).

Prostate-specific membrane antigen (PSMA) is a 750-amino acid glycoprotein highly expressed in malignant prostate tissues. PSMA reacts with the murine monoclonal antibody 7E11.C5, whose binding epitope has been mapped to the N-terminal of the protein distributed on the cytoplasmic side of the plasma membrane. We have developed murine monoclonal antibodies specific for extracellular epitopes of PSMA. Three of these antibodies--1G9, 3C6, and 4D4--display distinct binding properties consistent with their recognition of conformational epitopes within native PSMA. Results indicate this panel of antibodies binds to native full-length PSMA, but not to fusion proteins containing portions of the linear sequence of the protein. Antibody binding is greatly reduced upon heat denaturation of native PSMA, and these antibodies do not detect PSMA by Western blot. Immunoprecipitation experiments demonstrate the ability of each to bind to full-length PSMA as well as PSM', a form of the protein missing the first 57 amino acids. These results indicate each antibody is specific for an epitope within the extracellular domain, a region spanning residues 44-750. Flow cytometric experiments indicate strong specific binding to live LNCaP cells. Antibody inhibition studies demonstrate that these antibodies recognize at least two distinct epitopes. Taken together, the results demonstrate that these antibodies are specific for native protein conformational epitopes within the extracellular domain. Their properties, in particular strong binding to live cancer cells, make them ideal candidates that are clearly superior to linear sequence epitope specific antibodies for in vivo applications.

Mammographic wire localization in diagnosis and treatment of occult carcinoma of breast.

The use of screening mammography has increased dramatically, leading to the discovery of suspicious, nonpalpable mammary lesions. Mammographic wire localization (MWL) is currently being used to facilitate the biopsy of these lesions. We reviewed 104 patients undergoing 106 biopsies after MWL during a 14 month period to determine the usefulness of MWL. The average age of the patients was 58 +/- 14 years, with a range of 38 to 83 years. Abnormal mammographic findings consisted of microcalcifications (48 per cent) or mass and density (43 per cent), or both (9 per cent). Lesions of the right side (55 per cent) and upper and outer quadrant (49 per cent) were predominant. An average of 1.4 (range of one to four) specimens taken at biopsy per patient were required to remove the lesion. The mean duration of the biopsy was 34 minutes, with a range of ten to 75 minutes, and the mean total time in the operating room was 63 (range 31 to 115) minutes. The average cost of the procedure did not differ significantly between local and general anesthesia ($1,030 versus $1,142, respectively). Pathologic findings included fibrocystic disease (77 per cent), carcinoma (12 per cent) and fibroadenoma (7 per cent). Normal mammary tissue was found in 4 per cent of the biopsies. Five of the 13 carcinomas were in situ and seven were either in situ (five) or microinvasive only (two); only six lesions were frankly invasive. Ten patients were treated with modified radical mastectomy while three had segmental resection. All patients had in situ or Stage I carcinoma. MWL effectively localized nonpalpable mammary lesions and allowed accurate diagnosis and treatment of early stage carcinoma of the breast.