Different glycan structures in prostate-specific antigen from prostate cancer sera in relation to seminal plasma PSA

Abstract

Prostate-specific antigen (PSA), the tumor marker currently used for prostate cancer (PCa), is not specific enough to distinguish between PCa and benign prostate hyperplasia (BPH). Glycan processing is normally perturbed in tumors, therefore we investigated whether changes in glycosylation of PSA could be useful diagnostic indicators. Previously we determined that the glycosylation of PSA secreted by the tumor prostate cell line LNCaP differs significantly from that of PSA from seminal plasma (normal control). We therefore undertook a detailed glycan analysis of PSA derived from sera from PCa patients and, importantly, established that the glycosylation of the PCa serum PSA was significantly different from the PSA from the LNCaP cell line. In comparison with seminal plasma PSA, the fucose content of PSA from the PCa patient serum was significantly lower and there was a decrease in alpha2,3-linked sialic acid. Differences in the glycosylation of PSA derived from PCa patients' sera, seminal plasma, and LNCaP cells were further established by lectin detection, glycosylation immunosorbent assay, and two-dimensional electrophoresis. We also investigated whether the impact of glycosylation changes initiated by the tumor was reflected in the serum glycome. By comparing the glycans released from the total glycoproteins in PCa patient serum with those of normal serum we found an increase in the proportion of sialyl-Lewis x structures. Further analysis of the glycosylation of PSA from PCa and BPH sera will be required in order to determine the utility of these glycan differences to discriminate specifically between benign and malignant prostate states.

Microfluidic integration for automated targeted proteomic assays

“…Here, we quantify endogenous PSA isoforms present in 3 μL of minimally processed lysate from LAPC-4 cells derived from a lymph node of a human prostate cancer patient. The probed LAPC-4 lysate presents a distinctive four peak pattern in the pI 6.9-7.9 range that is similar to slab-gel assays of PSA purified from LAPC-4 cell culture medium (8,30). As a negative control, lysate from a PSA negative cell line (DU145) was assayed and shows no detectable PSA isoform readout, as expected.…”

“…The two PSA+ samples each show three major PSA isoforms falling within the pI 6.4-7.5 range, in good agreement with comparatively laborious slab-gel IEF studies (6,8). Patient-specific differences in PSA isoform representation and pI are clearly apparent, recapitulating the potential utility of isoform ratio measurements in clinical diagnostics and personalized medicine (6,7).…”

“…Proteomic studies suggest a promising link between prostate cancer incidence and differential isoform expression in healthy and cancer patient sera (6,8,9). Although promising, rigorous validation studies are needed to translate the potential of protein isoforms to the clinic.…”

A lectin array-based methodology for the analysis of protein glycosylation

“…There is increasing evidence that the PSA glycosylation is altered in prostate cancer serum in comparison to normal PSA [24,25]. Fig.…”

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

“…Also, the glycosylation of prostate cancer KLK3 was reduced in benign prostate hyperplasia (BPH) and exhibited a different composition (Basu et al, 2003;Ohyama et al, 2004) KLK3 from prostate tumor cell lines shows an altered sugar composition, with a significant lack of sialic acid in the N-glycan tree (Peracaula et al, 2003). 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).…”