Chondroitin Sulfate Disaccharides, a Serum Marker for Primary Serous Epithelial Ovarian Cancer

Abstract

Glycosaminoglycans are long polysaccharidic chains, which are mostly present in connective tissues. Modified GAG expression in tissues surrounding malignant cells has been shown to contribute to tumor progression, aggressive status and metastasis in many types of cancer. Ovarian cancer is one of the most lethal gynecological malignancies due to its late diagnosis because of the absence of clear symptoms and unavailability of early disease markers. We investigated for the first time GAG changes at the molecular level as a novel biomarker for primary epithelial ovarian cancer. To this end, serum of a cohort of 68 samples was digested with chondroitinase ABC, which releases chondroitin sulfate into disaccharides. After labeling and purification, they were measured by HPLC, yielding a profile of eight disaccharides. We proposed a novel GAG-based score named "CS- bio" from the measured abundance of disaccharides present that were of statistical relevance. CS-bio's performance was compared with CA125, the clinically used serum tumor marker in routine diagnostics. CS-bio had a better sensitivity and specificity than CA125. It was more apt in differentiating early-stage patients from healthy controls, which is of high interest for oncologists.

Keywords: HPLC; biomarker; chondroitin sulfate; disaccharide; glycosaminoglycan; ovarian cancer.

Figure 1

(a) Mean and 95% confidence intervals [1] of relative areas of CS disaccharides released from human serum measured by HPLC coupled to fluorescence detection. (b) Enlarged view of the low abundant CS disaccharides. * p < 0.5, ** p < 0.01, *** p < 0.001 as judged from non-parametric Mann–Whitney U-test. S indicates sulfate and the preceding digit indicates the sulfation position.

Figure 2

ROC curves of the biomarkers CS-bio and CA125 for (a) all EOC (n = 26) and control samples included in this study (n = 30) and (b) early stage (FIGO I + II, n = 18) and control samples (n = 30).

Figure 3

Boxplots were performed for CS-bio and logarithmic values of CA125. In (a,b), the whole cohort was considered in the EOC group. In (c,d), the EOC cohort was divided according to stages. The Bonferroni corrected p-values (* p < 0.5, ** p < 0.01, *** p < 0.001, n.s. non-significant) were estimated from non-parametric multiple pairwise comparison Jonckh eere–Terpstra test (T_JT).