Oligosaccharide Profiles of the Prostate Specific Antigen in Free and Complexed Forms from the Prostate Cancer Patient Serum and in Seminal Plasma: a Glycopeptide Approach

Abstract

The oligosaccharide structures of prostate specific antigen (PSA) are expected to be useful in discriminating prostate cancer from benign conditions both accompanied by increased serum PSA levels. A large proportion of PSA forms a covalent complex with a glycoprotein, alpha(1)-antichymotrypsin, in human blood. In the present study, the glycan profiles of free and complexed forms of PSA from cancer patient serum and of seminal plasma PSA were compared by analyzing the glycopeptides obtained by lysylendopeptidase digestion of the electrophoretically separated PSA with mass spectrometry. The profiles of the PSA N-glycans from the free and complexed molecules were quite similar to each other and consisted of fucosylated biantennary oligosaccharides as the major class. They were mostly sialylated, and a considerable sialic acid fraction was alpha2,3-linked as determined by Streptococcus pneumoniae neuraminidase digestion of the glycopeptides. In the seminal plasma PSA, high-mannose and hybrid types of oligosaccharides were predominant, and the sialic acids attached to the latter as well as to biantennary oligosaccahrides were exclusively alpha2,6-linked because they were removed by Arthrobacter ureafaciens neuraminidase but resistant to S. pneumoniae neuraminidase. Complex-type oligosaccharides from other sources were found in the seminal plasma sample, indicating that analysis of released glycans carries a risk of being misleading. The results suggest that identification of alpha2,3-linked sialic acids on PSA potentially discriminates malignant from benign conditions, if the analysis is applied to oligosaccharides specifically attached to the N-glycosylation site of PSA in either a free or a complexed form in the serum.

Glycan Characterization of PSA 2-DE Subforms from Serum and Seminal Plasma

“…In the same study, we observed a different proportion of alpha 2-3 linked sialic acid in the PSA present in patients, which was decreased in relation to that from healthy seminal plasma (15 vs. 25%) (Tabares et al, 2006). However, our present results are more consistent with the observations made by other authors (Ohyama et al, 2004;Tajiri et al, 2008).…”

“…The low amount of PSA in sera is, however, the limiting step to fully characterize the glycan structures of PSA. So far, few groups have reported the detailed glycan structures of serum PSA from PCa patients (Tabares et al, 2006;Tajiri et al, 2008). Taking into account that the PSA 2-DE subforms (F1-F5) show different proportions between BPH and PCa sera (Sarrats et al, 2010), in this work we have characterized by N-glycan sequencing these 2-DE spots of PSA samples from PCa patients' sera.…”

“…PSA N-glycosylation has been investigated by different authors (Okada et al, 2001;Peracaula et al, 2003;Tabares et al, 2006;Tajiri et al, 2008). However, no evidence of Olinkages has been reported.…”

Focused Differential Glycan Analysis with the Platform Antibody-assisted Lectin Profiling for Glycan-related Biomarker Verification

“…However, their profiles did not necessarily show particular similarity to the one reported recently for serum PSA derived from prostate cancer (PC) patients, except for ␣2-3 Sia increment. It should be mentioned, however, that serum PSA level is abnormally high (Ͼ10 g/ml serum) in these patients (35). From a clinical viewpoint, it is important to differentiate PSA glycoforms of malignant prostate cancer from benign prostate hyperplasia.…”

Sweetened kallikrein-related peptidases (KLKs): glycan trees as potential regulators of activation and activity

“…Seemingly, differences exist in fucosylation and sialylation of KLK3 from prostate cancer patients, although they do not appear to be sufficient for reliable prognosis of the disease (Tabares et al, 2006(Tabares et al, , 2007. Nevertheless, these differences have the potential to discriminate between benign and malignant prostate disease, e.g., by monitoring the complex of KLK3 with anti-chymotrypsin, by using fucosylation analysis, mass spectrometry or lectin microarrays and immunosorbent assays (Tajiri et al, 2008;Dwek et al, 2010;Sarrats et al, 2010;Yan Li et al, 2011).…”