Serum N-glycan profiling is a potential biomarker for castration-resistant prostate cancer

Abstract

We investigated the diagnostic and prognostic potential of serum N-glycan profiling for castration-resistant prostate cancer (CRPC). We retrospectively investigated serum N-glycan structural analysis by glycoblotting for 287 patients with benign prostatic hyperplasia (BPH), 289 patients with newly diagnosed prostate cancer (PC), 57 patients with PC treated with androgen-deprivation therapy without disease progression (PC-ADT), and 60 patients with CRPC. N-Glycan profiling was compared between the non-CRPC (BPH, newly diagnosed PC and PC-ADT) and CRPC patients. We obtained the quantitative score for CRPC (CRPC N-glycan score) by discriminant analysis based on the combination of 9 N-glycans that were significantly associated with CRPC. The median CRPC N-glycan score was found to be significantly greater in CRPC patients than in non-CRPC patients. The CRPC N-glycan score could classify CRPC patients with sensitivity, specificity, and area under the curve of 87%, 69%, and 0.88, respectively. The CRPC N-glycan score >1.7 points was significantly associated with poor prognosis in patients with CRPC. The glycoprotein analysis showed that not immunoglobulins but α-1-acid glycoprotein (AGP) were a potential candidate for the carrier protein of N-glycans. The overexpression of specific N-glycans may be associated with their castration-resistant status and be a potential biomarker for CRPC.

Figure 1

The difference in the serum N-glycan levels between the non-CRPC (BPH, newly diagnosed PC, and PC-ADT) and CRPC patients. A significant difference in the serum N-glycan levels was noted between the non-CRPC (BPH, newly diagnosed PC, and PC-ADT) and CRPC patients in m/z 1871 (A; P < 0.001), m/z 2337 (B; P < 0.001), m/z 2744 (C; P < 0.001), m/z 2890 (D; P < 0.001), m/z 3049 (E; P < 0.001), m/z 3109 (F; P < 0.001), m/z 3195 (G; P < 0.001), m/z 3414 (H; P < 0.001), and m/z 3719 (I; P < 0.001).

Figure 2

Representative mass spectra. Representative mass spectra were shown in the patients with BPH (A), newly diagnosed PC (B), PC-ADT (C), and CRPC (D).

Figure 3

Clinical impact of the CRPC N-glycan score on CRPC discrimination. The Waterfall plots show the association between the CRPC N-glycan score and the CRPC status (A). The CRPC N-glycan score was significantly greater in patients with CRPC than in those with BPH, newly diagnosed PC, and PC with ADT (B). The predictive value of the N-glycan score for CRPC was significant, with an area under the curve (AUC) of 0.88 (95% CI = 0.83–0.93, P < 0.001) (C). The CSS (from serum N-glycan analysis until death) were significantly shorter in CRPC patients with higher CRPC N-glycan score (>1.7 points) than in those with lower scores (≤1.7 points) (D; P = 0.028). The longitudinal evaluation of the CRPC N-glycan score showed the CRPC N-glycan score was greater before-and-after CRPC (n = 5) than that at the baseline (E; P = 0.048).

Figure 4

The longitudinal value of the CRPC N-glycan score. The case 1 showed early elevation (−985 days) of the CRPC N-glycan score before the PSA-based CRPC diagnosis (A). Similarly, the case 2 showed early elevation (−126 days) of the CRPC N-glycan score before the PSA-based CRPC diagnosis (B).

Figure 5

N-Glycan analysis of immunoglobulins (Igs). N-Glycan profiling in Igs was not consistent with that of whole serum N-glycan profiling. The Igs-related N-glycans of m/z 1871 (A), 2337 (B), and 2744 (C) were significantly decreased in the CRPC patients than that of non-CPRC patients. There was no significant difference in the m/z 2890 (D), 3049 (E), 3109 (F), and 3195 (G) between the CRPC and non-CPRC patients. The N-glycans of m/z 3414, and m/z 3719 were not detected on Igs.

Figure 6

Detection of lectin-reactive glycans on α-1-acid glycoprotein (AGP) using recombinant lectin array chip. The AGP concentration adjusted lectin array analysis showed that terminal α2.3 sialylated glycan (A), α2.6 sialylated glycan (B), and terminal galactose (C), were significantly increased in the CRPC patients. In contrast, branched-LacNAc structure was significantly decreased in the CRPC patients (D). RFI: Relative fluorescent intensity.

Figure 7

The difference in the serum N-glycans on α-1-acid glycoprotein (AGP) between the PC-ADT and CRPC patients using Gly-Q system. Serum N-glycans on AGP (pooled serum) were measured between the PC-ADT (A) and CRPC (B). The signal area of A3, A4, and A2 were higher in the patients with CRPC (5390 RFU * GU) than that of PC-ADT (4247 RFU * GU) (C). RFU: Relative Fluorescence Unit, GU: Glucose Unit.