PRM-MS Quantitative Analysis of Isomeric N-Glycopeptides Derived From Human Serum Haptoglobin of Patients With Cirrhosis and Hepatocellular Carcinoma

Currently surveillance strategies have inadequate performance for the early detection of hepatocellular carcinoma (HCC). Protein glycosylation is a potential source of biomarkers to differentiate between cirrhosis and HCC. We performed a comprehensive LC-PRM-MS approach where a targeted parallel reaction monitoring (PRM) strategy was coupled to a powerful LC system to study the microheterogeneity of haptoglobin (Hp) extracted from 15 patients with cirrhosis and 15 with HCC. We found that our strategy was able to identify a large number of isomeric N- glycopeptides mainly located in the glycosylation site Asn207. Nine out of twelve N- glycopeptides, located in the Asn207 site, had significant differences in abundance between patients with cirrhosis and HCC ( p  < 0.05). The area under the curve (AUC) of alpha-fetoprotein (AFP) was alone 0.85, which improved to 0.95 (95% CI: 0.88, 1) when NLF_5613 Isomer 1 was combined with AFP. When comparing the early HCC vs. cirrhosis, four sialylated-fucosylated glycopeptides better estimated AUCs with respect to AFP (AUC AFP = 0.66, and AUC N− glycopeptides = 0.86, 0.84, 0.88, and 0.80, respectively). Further large scale validation of glycopeptides for the early detection of HCC is warranted.