Three immunoassays based on monoclonal antibodies specific for prostate specific antigen (PSA), α‐1‐antichymotrypsin (ACT), and the PSA–ACT complex

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Abstract
BACKGROUND: Prostate specific antigen (PSA) has been widely used as a biomarker for the screening and diagnosis of prostate cancer. PSA in serum predominantly exists as a complex with α‐1‐antichymotrypsin (ACT), and measurement of free PSA and the PSA–ACT complex may improve the utility of the serum PSA assay for differential diagnosis of prostate cancer and non‐malignant prostate diseases, such as benign prostatic hyperplasia (BPH).METHODS: Monoclonal antibodies (MAbs) against PSA, ACT, and the PSA–ACT complex were produced by immunizing mice with an incubated mixture of PSA and ACT, and characterized by Western blot analyses and several enzyme‐linked immunosorbant assay (ELISA) methods.RESULTS: The MAbs produced in this study are capable of distinguishing the PSA–ACT complex from free PSA and ACT. Four MAbs have been selected and utilized to construct three ELISA systems for the separate measurements of free PSA, the PSA–ACT complex, and total PSA.CONCLUSIONS: The three PSA assay systems developed in this study can specifically measure free PSA, total PSA, and the PSA–ACT complex with equal molar sensitivity. It is expected that these PSA assay systems could be useful in the diagnosis of prostate cancer. Prostate 56: 131–141, 2003.