Alterations in the serum glycome due to metastatic prostate cancer

Abstract

Glycomic profiles derived from human blood sera of 10 healthy males were compared to those from 24 prostate cancer patients. The profiles were acquired using MALDI-MS of permethylated N-glycans released from 10-microL sample aliquots. Quantitative permethylation was attained using solid-phase permethylation. Principal component analysis of the glycomic profiles revealed significant differences among the two sets, allowing their distinct clustering. The first principal component distinguished the 24 prostate cancer patients from the healthy individuals. It was determined that fucosylation of glycan structures is generally higher in cancer samples (ANOVA test p-value of 0.0006). Although more than 50 N-glycan structures were determined, 12 glycan structures, of which six were fucosylated, were significantly different between the two sample sets. Significant differences were confirmed through two independent statistical tests (ANOVA and ROC analyses). Ten of these structures had significantly higher relative intensities in the case of the cancer samples, while the other two were less abundant in the cancer samples. All 12 structures were statistically significant, as suggested by their very low ANOVA scores (<0.001) and ROC analysis, with area under the curve values close to 1 or 0. Accordingly, these structures can be considered as cancer-specific glycans and potential prostate cancer biomarkers. Therefore, serum glycomic profiling appears worthy of further investigation to define its role in cancer early detection and prognostication.

Figure 1

MALDI mirror spectra of permethylated N-glycans derived from human blood serum of a healthy individual vs. a prostate cancer patient. Symbols: , N-acetylglucosamine; , mannose; , galactose; , fucose; , N-acetylneuraminic acid.

Figure 2

Principal component analysis (PCA) scores plot for mass spectra of glycans derived from blood sera of healthy individuals (n=10) and prostate cancer patients (n=24).

Figure 3

Representative ROC analysis AUC plots for different glycan structures reflecting high- (a), moderate- (b), and low-accuracy (c) tests.

Figure 4

MALDI mass spectra representative of the N-glycans derived from human blood serum of a healthy individual and a prostate cancer patient.

Figure 5

Box graphs comparing the average relative intensities of all N-glycans which demonstrated highly accurate ROC analysis AUC values (0.9p-values lower than 0.001, for 10 healthy and 24 prostate cancer samples.