| 1. |
- Becker, Charlotte, et al.
(författare)
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Characterization of epitope structure for 53 monoclonal antibodies against prostate-specific antigen
- 1999
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Ingår i: Tumor Biology. - : Springer Science and Business Media LLC. - 1423-0380 .- 1010-4283. ; 20:Suppl. 1, s. 13-17
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Tidskriftsartikel (refereegranskat)abstract
- Prostate-specific antigen (PSA) is the most widely used marker of prostate cancer. Assays for PSA are based on anti-PSA antibodies, and the characterization and selection of these antibodies is important for determining their optimum performance. In our study, we characterized the reactivity of 53 antibodies, submitted to the ISOBM TD-3 PSA Workshop, using free PSA, PSA complexed to alpha1-antichymotrypsin (ACT) and purified ACT. Immunoblotting was performed after native agarose gel or reducing sodium dodecyl polyacrylamide gel electrophoresis. Immunoblotting after agarose gel electrophoresis revealed 10 antibodies that recognized only the free form of PSA, and 43 antibodies that detected both free PSA and PSA-ACT. Immunoblotting of reducing sodium dodecyl-polyacrylamide gels showed the linear or conformation-dependent nature of the epitopes. Two antibodies specific for free PSA and 18 antibodies that recognized both free PSA and PSA-ACT complex recognized linear epitopes. Moreover, 7 antibodies also detected fragmented forms of PSA.
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| 2. |
- Becker, Charlotte, et al.
(författare)
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Individual prostate-specific antigen (PSA) forms as prostate tumor markers
- 1997
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Ingår i: Clinica Chimica Acta. - 0009-8981. ; 257:1, s. 117-132
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Tidskriftsartikel (refereegranskat)abstract
- Prostate-specific antigen (PSA) is a kallikrein-like serine protease mainly expressed in the human prostate. It is responsible for the proteolysis of the gel-forming proteins in human semen. Two major extracellular protease inhibitors, alpha-1-antichymotrypsin (ACT) and alpha-2-macroglobulin (AMG) may inactivate PSA escaping from the prostate. The predominant immunodetected form of PSA in serum is complexed to ACT but PSA exists also in a free non-complexed form despite the large excess of inhibitors. The concentrations of PSA in serum are normally less than 4 micrograms/l. but elevated concentrations are found in a majority of patients with prostate cancer (CAP) and the analysis of PSA in serum has become invaluable in the detection and monitoring of patients with CAP. However, it is not an ideal tumor marker in the sense that there are CAP patients with normal PSA concentrations in serum and patients with benign hyperplasia of the prostate (BPH) with elevated PSA concentrations. Analysis of the various PSA forms in serum attracts much interest as there is a higher proportion of PSA in complex with ACT in patients with CAP than in those with BPH. Optimal combinations of monoclonal antibodies have been used to design sensitive noncross-reacting immunoassays for the detection of free PSA, PSA-ACT complexes and the detection of both free PSA and PSA complexes in an equimolar fashion (i.e. total PSA). Several studies have demonstrated that the analysis of the proportions of the free-to-total PSA in serum may increase the diagnostic specificity by 15-20% without significant loss in the sensitivity for detection of CAP.
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| 3. |
- Piironen, T, et al.
(författare)
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Determination and analysis of antigenic epitopes of prostate specific antigen (PSA) and human glandular kallikrein 2 (hK2) using synthetic peptides and computer modeling
- 1998
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Ingår i: Protein Science. - : Wiley. - 1469-896X .- 0961-8368. ; 7:2, s. 259-269
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Tidskriftsartikel (refereegranskat)abstract
- Prostate specific antigen (PSA) and human glandular kallikrein 2 (hK2), produced essentially by the prostate gland, are 237-amino acid monomeric proteins, with 79% identity in primary structure. Twenty-five anti-PSA monoclonal antibodies (Mabs) were studied for binding to a large array of synthetic linear peptides selected from computer models of PSA and hK2, as well as to biotinylated peptides covering the entire PSA sequence. Sixteen of the Mabs were bound to linear peptides forming four independent binding regions (I-IV). Binding region I was localized to amino acid residues 1-13 (identical sequence for PSA and hK2), II (a and b) was localized to residues 53-64, III (a and b) was localized to residues 80-91 (= kallikrein loop), and IV was localized to residues 151-164. Mabs binding to regions I and IIa were reactive with free PSA, PSA-ACT complex, and with hK2; Mabs binding to regions IIb, IIIa, and IV were reactive with free PSA and PSA-ACT complex, but unreactive with hK2; Mabs binding to region IIIb detected free PSA only. All Mabs tested (n = 7) specific for free PSA reacted with kallikrein loop (binding region IIIb). The presence of Mabs interacting with binding region I did not inhibit the catalytic activity of PSA, whereas Mabs interacting with other binding regions inhibited the catalysis. Theoretical model structures of PSA, hK2, and the PSA-ACT complex were combined with the presented data to suggest an overall orientation of PSA with regard to ACT.
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| 4. |
- Stenman, U H, et al.
(författare)
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Summary report of the TD-3 workshop: characterization of 83 antibodies against prostate-specific antigen
- 1999
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Ingår i: Tumor Biology. - : Springer Science and Business Media LLC. - 1423-0380 .- 1010-4283. ; 20:Suppl. 1, s. 1-12
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Tidskriftsartikel (refereegranskat)abstract
- Twelve research groups participated in the ISOBM TD-3 Workshop in which the reactivity and specificity of 83 antibodies against prostate-specific antigen (PSA) were investigated. Using a variety of techniques including cross-inhibition assays, Western blotting, BIAcore, immunoradiometric assays and immunohistochemistry, the antibodies were categorized into six major groups which formed the basis for mapping onto two- and three-dimensional (2-D and 3-D) models of PSA. The overall findings of the TD-3 Workshop are summarized in this report. In agreement with all participating groups, three main antigenic domains were identified: free PSA-specific epitopes located in or close to amino acids 86-91; discontinuous epitopes specific for PSA without human kallikrein (hK2) cross-reactivity located at or close to amino acids 158-163; and continuous or linear epitopes shared between PSA and hK2 located close to amino acids 3-11. In addition, several minor and partly overlapping domains were also identified. Clearly, the characterization of antibodies from this workshop and the location of their epitopes on the 3-D model of PSA illustrate the importance of selecting appropriate antibody pairs for use in immunoassays. It is hoped that these findings and the epitope nomenclature described in this TD-3 Workshop are used as a standard for future evaluation of anti-PSA antibodies.
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| 5. |
- Tornblom, M, et al.
(författare)
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Diagnostic value of percent free prostate-specific antigen: retrospective analysis of a population-based screening study with emphasis on men with PSA levels less than 3.0 ng/mL
- 1999
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Ingår i: Urology. - 1527-9995 .- 0090-4295. ; 53:5, s. 945-950
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: To retrospectively investigate the use of percent free prostate-specific antigen (PSA) compared with total PSA in serum as predictor of prostate cancer in men selected randomly from the general population who underwent biopsy on the basis of abnormal findings on digital rectal examination (DRE) or transrectal ultrasound (TRUS) and/or serum PSA levels greater than 10 ng/mL. METHODS: A single intervention, population-based screening study was undertaken in 1988 and 1989. Of the 2400 men aged 55 to 70 years invited to participate, 1782 men responded and were examined with DRE, TRUS, and PSA testing (Tandem-Hybritech). In 1995, frozen serum samples from 1748 men were analyzed for percent free PSA (Prostatus, Wallac OY). Five-year follow-up data on new cancers in the screened population were obtained from the Swedish Cancer Registry (SCR). RESULTS: Of the 1748 men, 367 underwent TRUS-guided biopsies because of abnormal findings on either DRE or TRUS or serum PSA levels of greater than 10 ng/mL. This resulted in the diagnosis of 64 cases of prostate cancer (3.7%). PSA levels of 3.0 ng/mL or greater were found in 55 (86%) of 64 cancer cases and in 399 (24%) of the 1684 benign cases. Among the 1294 men with PSA less than 3.0 ng/mL, 9 prostate cancers were diagnosed (14% of all prostate cancers). All 9 patients with cancer and with PSA less than 3.0 ng/mL had a percent free PSA of 18% or less. In the group of 1109 patients with PSA less than 3.0 ng/mL and a percent free PSA greater than 18%, 159 biopsies were performed because of abnormal DRE or TRUS. However, no prostate cancer was diagnosed in this category of patients. Five years after the screening intervention, 7 more cases of prostate cancer were clinically diagnosed in the screened population according to the SCR. CONCLUSIONS: The combination of PSA levels less than 3.0 ng/mL and percent free PSA greater than 18% defines a large part of the population at a very low risk of cancer of the prostate both at the time of screening and during the following 5 years. Men in this group may be spared DRE, and longer screening intervals may be considered. However, the risk of having prostate cancer is not negligible in men with PSA less than 3.0 ng/mL and percent free PSA of 18% or less. The results of this study indicate that biopsy should be recommended to men fulfilling these criteria, although these results should be confirmed in larger prospective studies because of the limited number of patients with prostate cancer in the present series.
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