Improvement of prostate cancer diagnosis using a multiplex test of PSA, GDF-15 (NAG-1) and glycan-binding auto-IgG in plasma

Document Type

Conference Proceeding

Publication Date

7-1-2018

Publication Title

Cancer Res

Abstract

The blood prostate-specific antigen (PSA) assay is used for prostate cancer diagnosis but specificity of the assay is not satisfactory. Previously a combined PSA and GDF-15 (NAG-1) score was shown to improve specificity of prostate cancer detection. Our hypothesis was that, in prostate cancer, glycoproteins were secreted from tumor tissues into blood and induce autoimmune immunoglobulin G (auto-IgG) production and, thus, measurement of the glycan-auto-IgG in blood would improve prostate cancer diagnosis. The 24 glycan-containing microarray analyses have been carried out with plasma samples obtained from 35 prostate cancer patients and 46 healthy subjects to identify glycan-binding auto-IgG biomarker candidates by incubating the auto-IgG captured by glycans spotted on the slide with biotinylated anti-human secondary IgG/streptavidin-Alexa647. Among the 24 glycans, GlcNAc-polyacrylamide (PAA) (G09) and Fucα1-3GlcNAcβ-PAA (G24) glycans showed lower signals of the auto-IgG in the prostate cancer after quantile normalization. β-D-Galactose-PAA (G04) and L-rhamnose-PAA (G08) glycans showed higher signals of the auto-IgG in prostate cancer. No auto-IgM signal was detected. Subsequently, a 5-glycan subarray analysis was developed and lower signals of G09 and G24 glycan-binding auto-IgG were verified by the subarray analysis using 35 prostate cancer plasma samples compared with 54 controls. A higher signal of Neu5Acα2-8Neu5Acα2-8Neu5Acα-sp-PAA (G81)-binding auto-IgG in prostate cancer was detected by the subarray analysis. When the result obtained with the G81-binding auto-IgG was combined with levels of PSA and NAG-1, the prediction rate of prostate cancer increased to 86.2% from 78.2% with PSA levels alone, improving diagnostic accuracy of prostate cancer. The G81 glycan-binding auto-IgG was isolated from prostate cancer and control plasma samples using G81 glycan-affinity chromatography. Western blot analysis of the auto-IgG eluate with a secondary IgG antibody revealed that the level of the 50 kDa heavy chain of the auto-IgG obtained from the prostate cancer patient was ~3-fold higher than the control sample. The 50 kDa fragment was identified as an IgG heavy chain variable region by N-terminal sequencing (Edman's degradation). Our result demonstrated that a multiplex biomarker diagnostic consisting of glycan-binding auto-IgG, PSA and NAG-1 increased specificity and sensitivity of prostate cancer diagnosis. Supported by NCI SBIR Phase I, CA159721.

Volume

78

Issue

Issue 13 Supplement

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