Novel plasma glycoprotein biomarkers predict progression-free survival in surgically resected clear cell renal cell carcinoma

Introduction: Limited data exists on utilization of protein post-translational modifications as biomarkers for clear cell renal cell carcinoma (ccRCC). We employed high-throughput glycoproteomics to evaluate differential expression of glycoprotein-isoforms as novel markers for ccRCC progression-free survival (PFS). Methods: Plasma samples were obtained from 77 patients treated surgically for ccRCC. Glycoproteomic analyses were carried out after liquid chromatography tandem mass spectrometry. Age-adjusted Cox proportional hazard models were constructed to evaluate PFS. Optimized Harrell's C-index was employed to dichotomize the collective for the construction of Kaplan-Meier curves. Results: The average length of follow-up was 3.4 (range: 0.04–9.83) years. Glycoproteomic analysis identified 39 glycopeptides and 14 non-glycosylated peptides that showed statistically significant (false discovery rate P ≤ 0.05) differential expression associated with PFS. Five of the glycosylated peptides conferred continuous hazard ratio (HR) of > 6 (range 6.3–11.6). These included prothrombin A2G2S glycan motif (HR = 6.47, P = 9.53E-05), immunoglobulin J chain FA2G2S2 motif (HR = 10.69, P = 0.001), clusterin A2G2 motif (HR = 7.38, P = 0.002), complement component C8A A2G2S2 motif (HR = 11.59, P = 0.002), and apolipoprotein M glycopeptide with non-fucosylated and non-sialylated hybrid-type glycan (HR = 6.30, P = 0.003). Kaplan-Meier curves based on dichotomous expression of these five glycopeptides resulted in hazard ratios of 3.9 to 10.7, all with P-value < 0.03. Kaplan-Meyer plot using the multivariable model comprising 3 of the markers yielded HR of 11.96 (P < 0.0001). Conclusion: Differential glyco-isoform abundance of plasma proteins may be a useful source of biomarkers for the clinical course and prognosis of ccRCC.