title: Selective recognition of enzymatically active prostate-specific antigen (PSA) by anti-PSA monoclonal antibodies.
abstract: Prostate-specific antigen (PSA) is widely used as a serum marker for the diagnosis of prostate cancer. To evaluate two anti-free PSA monoclonal antibodies (mAbs) as potential tools in new generations of more relevant PSA assays, we report here their properties towards the recognition of specific forms of free PSA in seminal fluids, LNCaP supernatants, 'non-binding' PSA and sera from cancer patients. PSA from these different origins was immunopurified by the two anti-free PSA mAbs (5D3D11 and 6C8D8) as well as by an anti-total PSA mAb. The composition of the different immunopurified PSA fractions was analysed and their respective enzymatic activities were determined. In seminal fluid, enzymatically active PSA was equally purified with the three mAbs. In LNCaP supernatants and human sera, 5D3D11 immunopurified active PSA mainly, whereas 6C8D8 immunopurified PSA with residual activity. In sera of prostate cancer patients, we identified the presence of a mature inactive PSA form which can be activated into active PSA by use of high saline concentration or capture by an anti-total PSA mAb capable of enhancing PSA activity. According to PSA models built by comparative modelling with the crystal structure of horse prostate kallikrein described previously, we assume that active and activable PSA could correspond to mature intact PSA with open and closed conformations of the kallikrein loop. The specificity of 5D3D11 was restricted to both active and activable PSA, whereas 6C8D8 recognized all free PSA including intact PSA, proforms and internally cleaved PSA.
authors.affiliation: Unité Mixte de Recherche UMR 2714 CNRS/bioMérieux, IFR128 BioSciences Lyon-Gerland, France.
authors.forename: Sandrine
authors.initials: S
authors.lastname: Michel
authors.forename: Emilie
authors.initials: E
authors.lastname: Collomb-Clerc
authors.forename: Christophe
authors.initials: C
authors.lastname: Geourjon
authors.forename: Jean-Philippe
authors.initials: JP
authors.lastname: Charrier
authors.forename: Jacques
authors.initials: J
authors.lastname: Passagot
authors.forename: Yves
authors.initials: Y
authors.lastname: Courty
authors.forename: Gilbert
authors.initials: G
authors.lastname: Deléage
authors.forename: Colette
authors.initials: C
authors.lastname: Jolivet-Reynaud
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000737:chemistry / Q000494:pharmacology; D000918:Antibody Specificity; D006736:Horses; D006801:Humans; D007610:Kallikreins / Q000737:chemistry; D008297:Male; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017430:Prostate-Specific Antigen / Q000037:antagonists & inhibitors / Q000276:immunology* / Q000378:metabolism*; D011471:Prostatic Neoplasms / Q000097:blood* / Q000473:pathology; D012661:Semen / Q000737:chemistry; D017386:Sequence Homology, Amino Acid; D014407:Tumor Cells, Cultured
chemical_list: D000911:Antibodies, Monoclonal; D007610:Kallikreins; D017430:Prostate-Specific Antigen