Comparison of prostate specific antigen,prostate specific membrane antigen,and LNCaP-based enzyme-linked immunosorbent assays in prostatic cancer patients and patients with benign prostatic enlargement

Serum assays for prostate specific antigen (PSA; monoclonal), for prostate specific membrane antigen (PSM; Western blot), and a LNCaP/7E11.C5-based competitive enzyme-linked immunosorbent assay (ELISA) were evaluated in a small number of prostate cancer patients with localized or disseminated disease, and judged to be in clinical progression or remission based on National Prostate Cancer Project (NPCP) criteria. PSA values recognized the presence of clinical progression in localized disease (B₁-C) and to a lesser degree disseminated disease (D₁-D₂). In contrast, to a limited degree the ELISA test recognized clinical progression mainly in disseminated disease and chiefly in stage D₂. PSM values were elevated in both D₁ and D₂ but not in a linear fashion as observed with PSA. The ELISA and PSM results may be assessing a different clinical response to prostatic cancer than that recognized by PSA. This could reflect a developing clone of resistant prostatic cells as previously postulated. To further pursue this possibility a secondary generation of monoclonal antibodies to PSM is being developed. The ELISA levels for benign prostatic enlargement were not elevated above normal. In contrast both with PSA and PSM the assays reflected levels significantly above the normal range in benign prostatic hypertrophy (BPH).