Identification of novel prostate-specific antigen-binding peptides modulating its enzyme activity

Abstract Background: Prostate-specific antigen (PSA) is the most important marker for prostate cancer, but PSA concentrations determined by various assays can differ significantly because of differences in specificity of the antibodies used. To identify epitopes recognized by various monoclonal antibodies (MAbs) to PSA, we have isolated peptides that react with the paratopes of these. Methods: Six anti-PSA MAbs representing three major epitope groups were screened with five cyclic phage display peptide libraries. After selection, the peptide sequences were determined by sequencing of the relevant part of viral DNA. Binding of the phage peptides to the MAbs was monitored by immunoassay. Results: For each MAb, several paratope-binding peptides with distinct sequence motifs were identified, but only ∼10% showed similarity with the PSA sequence. Some of these correctly predicted the location of the epitopes. By sequential panning of the library with two closely related MAbs, we identified peptides reacting equally with both MAbs. When analyzed against a large panel of PSA MAbs, the peptides generally showed restricted specificity toward the MAb used for selection, but some peptides bound to several related MAbs. Conclusions: Most of the cyclic peptides selected with PSA MAbs are specific for the MAb used for selection and do not resemble any sequence on the antigen. Peptides reactive with two MAbs recognizing the same epitope can be obtained by sequential panning. This method can be used to predict the location of some epitopes, but additional methods are needed to confirm the result.

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Structure, function, and regulation of the enzyme activity of prostate-specific antigen

World Journal of Urology ◽

10.1007/bf00185066 ◽

1993 ◽

Vol 11 (4) ◽

Cited By ~ 55

Author(s):

H. Lilja

Keyword(s):

Enzyme Activity ◽

Structure Function ◽

Prostate Specific Antigen ◽

Specific Antigen

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Concanavalin A immobilized magnetic poly(glycidyl methacrylate) beads for prostate specific antigen binding

Colloids and Surfaces B Biointerfaces ◽

10.1016/j.colsurfb.2015.06.050 ◽

2015 ◽

Vol 134 ◽

pp. 461-468 ◽

Cited By ~ 11

Author(s):

Neslihan Idil ◽

Işık Perçin ◽

Veyis Karakoç ◽

Handan Yavuz ◽

Nilüfer Aksöz ◽

...

Keyword(s):

Prostate Specific Antigen ◽

Concanavalin A ◽

Glycidyl Methacrylate ◽

Specific Antigen ◽

Antigen Binding

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Interfacial recognition of human prostate-specific antigen by immobilized monoclonal antibody: effects of solution conditions and surface chemistry

Journal of The Royal Society Interface ◽

10.1098/rsif.2012.0148 ◽

2012 ◽

Vol 9 (75) ◽

pp. 2457-2467 ◽

Cited By ~ 35

Author(s):

Xiubo Zhao ◽

Fang Pan ◽

Luis Garcia-Gancedo ◽

Andrew J. Flewitt ◽

Gregory M. Ashley ◽

...

Keyword(s):

Monoclonal Antibody ◽

Surface Chemistry ◽

Prostate Specific Antigen ◽

Physical Adsorption ◽

Specific Antigen ◽

Cancer Diagnostics ◽

Molecular Engineering ◽

Human Prostate ◽

Antigen Binding ◽

Adsorbed Amount

The specific recognition between monoclonal antibody (anti-human prostate-specific antigen, anti-hPSA) and its antigen (human prostate-specific antigen, hPSA) has promising applications in prostate cancer diagnostics and other biosensor applications. However, because of steric constraints associated with interfacial packing and molecular orientations, the binding efficiency is often very low. In this study, spectroscopic ellipsometry and neutron reflection have been used to investigate how solution pH, salt concentration and surface chemistry affect antibody adsorption and subsequent antigen binding. The adsorbed amount of antibody was found to vary with pH and the maximum adsorption occurred between pH 5 and 6, close to the isoelectric point of the antibody. By contrast, the highest antigen binding efficiency occurred close to the neutral pH. Increasing the ionic strength reduced antibody adsorbed amount at the silica–water interface but had little effect on antigen binding. Further studies of antibody adsorption on hydrophobic C8 (octyltrimethoxysilane) surface and chemical attachment of antibody on (3-mercaptopropyl)trimethoxysilane/4-maleimidobutyric acid N -hydroxysuccinimide ester-modified surface have also been undertaken. It was found that on all surfaces studied, the antibody predominantly adopted the ‘flat on’ orientation, and antigen-binding capabilities were comparable. The results indicate that antibody immobilization via appropriate physical adsorption can replace elaborate interfacial molecular engineering involving complex covalent attachments.

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Evaluation of a monoclonal immunoradiometric assay for prostate-specific antigen.

Clinical Chemistry ◽

10.1093/clinchem/33.12.2257 ◽

1987 ◽

Vol 33 (12) ◽

pp. 2257-2261 ◽

Cited By ~ 29

Author(s):

R C Rock ◽

D W Chan ◽

D Bruzek ◽

C Waldron ◽

J Oesterling ◽

...

Keyword(s):

Enzyme Activity ◽

Acid Phosphatase ◽

Prostate Specific Antigen ◽

Prostatic Carcinoma ◽

Mass Measurement ◽

Clinical Stage ◽

Specific Antigen ◽

Prostatic Acid Phosphatase ◽

Immunoradiometric Assay ◽

Enzyme Activity Assay

Abstract We evaluated the analytical performance of a new monoclonal immunoradiometric assay ("M-PSA") for prostate-specific antigen ("Tandem"; Hybritech Inc.) in comparison with a monoclonal immunoradiometric assay ("M-PAP") for mass measurement of prostatic acid phosphatase ("Tandem") and with a conventional enzyme-activity assay ("E-PAP") for prostatic acid phosphatase (EC 3.1.3.2). For M-PSA, the CVs were 1.3-3.0% within-run and 3.0-4.9% between-run. The minimum detectable mass concentration was 0.10 microgram/L, and linearity extended to 100 micrograms/L. The reference interval for M-PSA in 178 healthy men was 0-2.8 micrograms/L. Serum specimens from men with prostatic disease (primarily prostatic carcinoma and benign prostatic hypertrophy) were assayed by the three methods. Correlation was best between mass measurement (M-PAP) and enzyme activity (E-PAP) for prostatic acid phosphatase (r = 0.958). Results for PSA did not correlate well with those for either M-PAP (r = 0.629) or E-PAP (r = 0.387). PSA was increased in a higher percentage of specimens from men with earlier (clinical stage B) prostatic carcinoma than were results from either assay for PAP.

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