Altered glycosylation, expression of serum haptoglobin and alpha-1-antitrypsin in chronic hepatitis C, hepatitis C induced liver cirrhosis and hepatocellular carcinoma patients

Normal Alpha-1-Antitrypsin Variants Display in Serum Allele-Specific Protein Levels

Alpha-1-antitrypsin (A1AT or SERPINA1) has been proposed as a putative biomarker distinguishing healthy from diseased donors throughout several proteomics studies. However, the SERPINA1 gene displays high variability of frequent occurring genotypes among the general population. These different genotypes may affect A1AT expression and serum protein concentrations, and this is often not known, ignored, and/or not reported in serum proteomics studies. Here, we address allele-specific protein serum levels of A1AT in donors carrying the normal M variants of A1AT by measuring the proteoform profiles of purified A1AT from 81 serum samples, originating from 52 donors. When focusing on heterozygous donors, our data clearly reveal a statistically relevant difference in allele-specific protein serum levels of A1AT. In donors with genotype PI*M1VM1A, the experimentally observed ratio was approximately 1:1 (M1V/M1A, 1.00:0.96 ± 0.07, n = 17). For individuals with genotype PI*M1VM2, this ratio was 1:1.28 (M1V/M2, 1.00:1.31, ±0.19, n = 7). For genotypes PI*M1VM3 and PI*M1AM3, a significant higher amount of M3 was observed compared to the M1-subtypes (M1V/M3, 1.00:1.84 ± 0.35, n = 8; M1A/M3, 1.00:1.61 ± 0.33, n = 5). We argue that these observations are important and should be considered when analyzing serum A1AT levels before proposing A1AT as a putative serum biomarker.

Serum Glycoprotein Markers in Nonalcoholic Steatohepatitis and Hepatocellular Carcinoma

Fatty liver disease progresses through stages of fat accumulation and inflammation to nonalcoholic steatohepatitis (NASH), fibrosis and cirrhosis, and eventually hepatocellular carcinoma (HCC). Currently available diagnostic tools for HCC lack sensitivity and specificity. In this study, we investigated the use of circulating serum glycoproteins to identify a panel of potential prognostic markers that may be indicative of progression from the healthy state to NASH and further to HCC. Serum samples were processed and analyzed using a novel high-throughput glycoproteomics platform. Our initial dataset contained healthy, NASH, and HCC serum samples. We analyzed 413 glycopeptides, representing 57 abundant serum proteins, and compared among the three phenotypes. We studied the normalized abundance of common glycoforms and found 40 glycopeptides with statistically significant differences in abundances in NASH and HCC compared to controls. Summary level relative abundances of core-fucosylated, sialylated, and branched glycans containing glycopeptides were higher in NASH and HCC as compared to controls. We replicated some of our findings in an independent set of samples of individuals with benign liver conditions and HCC. Our results may be of value in the management of liver diseases. Data generated in this work can be downloaded from MassIVE (https://massive.ucsd.edu) with identifier MSV000088809.

Proteoform Profiles Reveal That Alpha-1-Antitrypsin in Human Serum and Milk Is Derived From a Common Source

The Alpha-1-Antitrypsin (A1AT) protein is an important protease inhibitor highly abundant in human serum and other body fluids. Additional to functioning as a protease inhibitor, A1AT is an important acute phase protein. Here, we set out to compare the proteoform profiles of A1AT purified from the human serum and milk of eight healthy donors to determine the origin of human milk A1AT. Following affinity purification, size-exclusion chromatography coupled to native mass spectrometry was used to monitor individual proteoform profiles comparing inter- and intra-donor profiles. The A1AT intra-donor proteoform profiles were found to be highly identical between serum and milk, while they were highly distinct between donors, even when comparing only serum or milk samples. The observed inter-donor proteoform variability was due to differences in the abundances of different N-glycoforms, mainly due to branching, fucosylation, and the relative abundance of N-terminally processed A1AT fragments. From our data we conclude that nearly all A1AT in serum and milk is synthesized by a common source, i.e. the liver, and then secreted into the circulation and enters the mammary gland via diffusion or transport. Thereby, proteoform profile changes, as seen upon infection and/or inflammation in the blood will be reflected in the milk, which may then be transferred to the breastfed infant.

Glycosylation in viral hepatitis

BACKGROUND

The interaction between hepatitis viruses and host cells is regulated by glycans exposed on the surfaces of human and viruses cells. As the biosynthesis and degradation of human glycoproteins take place at the highest level in the liver, the changes in glycosylation of serum proteins may potentially be useful in the diagnosis of liver pathology. On the other hand, specific alterations in viruses envelope glycans could cause large changes in the entry process of hepatitis viruses into a host cells.

SCOPE OF REVIEW

Unique alterations in glycosylation of specific proteins can be detected in HBV and HCV infected patients especially with confirmed fibrosis/cirrhosis. On the other hand, viral envelope proteins that bind to host cells are glycosylated. These glycosylated proteins play a key role in recognition, binding and penetration of the host cells. In this review we summarized the knowledge about significance of glycosylation for viral and host factors.

MAJOR CONCLUSIONS

Glycosylation changes in single serum glycoproteins are noticed in the sera of patients with viral hepatitis. However, a more specific biomarker for the diagnosis of chronic hepatitis than that of a single glycosylated molecule is systemic investigation of complete set of glycan structures (N-glycome). Glycans play important roles in the viral biology cycle especially as a connecting element with host receptors.

GENERAL SIGNIFICANCE

The interaction between virus glycoproteins and cellular receptors, which are also glycoproteins, determines the possibility of virus penetration into host cells. Therefore these glycans can be the targets for the developing of novel treatment strategies of viral hepatitis.

Identification and characterization of non-small cell lung cancer associated sialoglycoproteins

Aberrantly sialylated cellular glycoconjugates were found to be involved in different processes during tumorigenesis. Such alteration was also noted in case of lung cancer, an important cause of cancer-related death throughout the world. Thus, study on lung cancer associated sialoglycoproteins is of paramount relevance to have a deeper insight into the mechanism of the disease pathogenesis. In the present study, sialic acid specific lectin (Maackia amurensis agglutinin and Sambcus nigra agglutinin)-based affinity chromatography followed by 2D-PAGE and MALDI-TOF/TOF mass spectrometric analysis were done to explore the disease-associated serum proteins of squamous cell carcinoma and adenocarcinoma [the major two subtypes of NSCLC (non-small cell lung carcinoma)] patients. Among seven identified proteins, α1-antitrypsin and haptoglobin-β were preferred for further studies. These two proteins were characterized as the disease associated serum-sialoglycoproteins of NSCLC-patients by western immunoblotting using each lectin specific inhibitor. The presence of these sialoglycoproteins was found on NSCLC cell lines (NCI-H520 & A549) by confocal microscopy. Both these proteins were also present in tissue samples of NSCLC origin and involved in proliferation, invasion and migration of NSCLC cells. Our findings suggest that α1-antitrypsin and haptoglobin-β may be the disease-associated sialoglycoproteins in NSCLC, which seem to be involved in disease progression. SIGNIFICANCE: Our contribution regarding the identification of the NSCLC associated sialoglycoproteins may provide a new vision towards the development of clinically useful newer strategies for the treatment of this disease.

Association of the Sialylation of Antibodies Specific to the HCV E2 Envelope Glycoprotein with Hepatic Fibrosis Progression and Antiviral Therapy Efficacy

The E2 envelope glycoprotein of the hepatitis C virus (HCV) is a major target of broadly neutralizing antibodies that are closely related to a spontaneous cure of HCV infection. There is still no data about the diversity of E2-specific antibodies (Abs) glycosylation. The aim of this study was to analyze the level and sialylation of E2 IgG Abs, the relation of the respective changes to hepatic fibrosis (F) progression and their possible association with the efficacy of interferon-α-2a plus ribavirin (IFN-RBV) antiviral therapy. One hundred three HCV infected treatment-naive patients were examined using ELISA with E2 recombinant protein as antigen and sialic acid-specific Sambucus nigra agglutinin. The efficacy of the IFN-RBV treatment of patients with HCV dominant 1b and 3a genotypes (GT) was evaluated. A significant decrease of E2 Abs sialylation in the late stages of fibrosis was found irrespective of HCV genotype. On this basis, the F4 stage of fibrosis can be discriminated from its F0 or F1-3 stage by an about 75-79% accuracy. HCV infection of 1b genotype is associated with the production of lower sialylated E2 Abs, a higher frequency of F4 stage fibrosis, and a worse response to antiviral therapy. The increased SNA reactivity of E2 Abs was observed in patients with a sustained virological response (SVR). The proportion of SVR responders was significantly higher among patients with 3a genotype. However, for both dominant HCV genotypes (3a and 1b), an increased sialylation of E2 IgG was associated with a higher rate of patients with sustained virological response to antiviral therapy. Thus, the association of alterations of anti-E2 IgG Abs sialylation with hepatic fibrosis stage, HCV genotype, and the efficacy of antiviral therapy enables using these changes as novel noninvasive predictive biomarkers. The clinical potential of these findings is discussed.

Glycopeptide Biomarkers in Serum Haptoglobin for Hepatocellular Carcinoma Detection in Patients with Nonalcoholic Steatohepatitis

Nonalcoholic steatohepatitis (NASH) is rising in prevalence in the United States and is a growing cause of hepatocellular carcinomas (HCCs). Site-specific glycan heterogeneity on glycoproteins has been shown as a potential diagnostic biomarker for HCC. Herein, we have performed a comprehensive screening of site-specific N-glycopeptides in serum haptoglobin (Hp), a reporter molecule for aberrant glycosylation in HCC, to characterize glycopeptide markers for NASH-related HCCs. In total, 70 NASH patients (22 early HCC, 15 advanced HCC, and 33 cirrhosis cases) were analyzed, with Hp purified from 20 μL of serum in each patient, and 140 sets of mass spectrometry (MS) data were collected using liquid chromatography coupled with electron-transfer high-energy collisional dissociation tandem MS (LC-EThcD-MS/MS) for quantitative analysis on a novel software platform, Byos. Differential quantitation analysis revealed that five N-glycopeptides at sites N184 and N241 were significantly elevated during the progression from NASH cirrhosis to HCC (p < 0.05). Receiver operating characteristic (ROC) curve analysis demonstrated that the N-glycopeptides at sites N184 and N241 bearing a monofucosylated triantennary glycan A3G3F1S3 had the best diagnostic performance in detection of early NASH HCC, area under the curve (AUC) = 0.733 and 0.775, respectively, whereas α-fetoprotein (AFP) had an AUC of 0.692. When combined with AFP, the two panels improved the sensitivity for early NASH HCC from 59% (AFP alone) to 73% while maintaining a specificity of 70%, based on the optimal cutoff. Two-dimensional (2-D) scatter plots of the AFP value and N-glycopeptides showed that these N-glycopeptide markers detected 58% of AFP-negative HCC patients as distinct from cirrhosis. These site-specific N-glycopeptides could serve as potential markers for early detection of HCC in patients with NASH-related cirrhosis.

High Throughput Multiplex SNP-analysis in Chronic Obstructive Pulmonary Disease and Lung Cancer

Background:

A number of human inflammatory diseases and tumors have been shown to cause alterations in the glycosylation pattern of plasma proteins in a specific manner. These highly variable and versatile post-translational modifications finetune protein functions by influencing sorting, folding, enzyme activity and subcellular localization. However, relatively little is known about regulatory factors of this procedure and about the accurate causative connection between glycosylation and disease.

Objective:

The aim of the present study was to investigate whether certain single nucleotide polymorphisms (SNPs) in genes encoding glycosyltransferases and glycosidases could be associated with elevated risk for chronic obstructive pulmonary disease (COPD) and lung adenocarcinoma.

Methods:

A total of 32 SNPs localized in genes related to N-glycosylation were selected for the association analysis. Polymorphisms with putative biological functions (missense or regulatory variants) were recruited. SNPs were genotyped by a TaqMan OpenArray platform. A single base extension-based method in combination with capillary gel electrophoresis was used for verification.

Results:

The TaqMan OpenArray approach provided accurate and reliable genotype data (global call rate: 94.9%, accuracy: 99.6%). No significant discrepancy was detected between the obtained and expected genotype frequency values (Hardy–Weinberg equilibrium) in the healthy control sample group in case of any SNP confirming reliable sampling and genotyping. Allele frequencies of the rs3944508 polymorphism localized in the 3’ UTR of the MGAT5 gene significantly differed between the sample groups compared.

Conclusion:

Our results suggest that the rs34944508 SNP might modulate the risk for lung cancer by influencing the expression of MGAT5. This enzyme catalyzes the addition of N-acetylglucosamine (GlcNAc) in beta 1-6 linkage to the alpha-linked mannose of biantennary N-linked oligosaccharides, thus, increasing branching that is the characteristic of invasive malignancies.

Prognostic and clinicopathological significance of Hapto and Gremlin1 expression in extrahepatic cholangiocarcinoma

Background: Some studies have demonstrated that Hapto and Gremlin1 play an important biological role in many neoplasms. However, the role of Hapto and Gremlin1 in extrahepatic cholangiocarcinoma (ECC) remains to be revealed. Thus, this study investigated the prognostic and clinicopathological significance of Hapto and Gremlin1 expression in ECC.

Methods: We examined Hapto and Gremlin1 expression in 100 ECC, 30 peritumoral tissues, 10 adenoma and 15 normal biliary tract tissues using EnVision immunohistochemistry. The relationship between Hapto and Gremlin 1 expression and clinicopathological parameters was evaluated using the χ² test or Fisher's exact test. The overall survival of patients was analyzed using Kaplan-Meier univariate survival analysis and log-rank tests.

Results: Hapto and Gremlin1 proteins were overexpressed in ECC compared to peritumoral tissues, adenoma, and normal biliary tract (P<0.05 or P<0.01). The positive rate of Hapto and Gremlin1 expression was significantly higher in cases with poor differentiation, lymph node metastasis, invasion of surrounding tissues and organs, a tumor-node-metastasis (TNM) stage of III or IV and no resection. Kaplan-Meier survival analysis showed that ECC patients with positive Hapto and/or Gremlin1 expression survived significantly shorter than patients with negative Hapto and/or Gremlin1 expression. Cox multivariate analysis revealed that positive Hapto and Gremlin1 expression were independent poor prognostic factors in ECC patients.

Conclusion: The present study indicated that positive Hapto and/or Gremlin1 expression are closely associated with the pathogenesis, clinical, pathological and biological behaviors, and poor prognosis in ECC.

Disease-specific haptoglobin-β chain N-glycosylation as biomarker to differentiate non-small cell lung cancer from benign lung diseases

Background: The association of pathological states with N-glycosylation of haptoglobin-β has attracted increasing attention.

Materials & Methods: In the present study, disease-specific haptoglobin-β (DSHp-β) was separated from serum immunoinflammation-related protein complexes (IIRPCs) of 600 participants including 300 patients with benign lung diseases (BLDs) and 300 patients with non-small cell lung cancer (NSCLC). The enriched glycopeptides of the tryptic digests of the DSHp-β were analyzed using matrix assisted laser desorption/ionization-Fourier transform ion cyclotron resonance mass spectrometry (MALDI-FTICR MS).

Results: 20 of glycopeptides were detected for each sample. The statistical analysis has indicated that significant changes in the sialylation of DSHp-β between BLDs and NSCLC patients were observed. The age- and sex-matched participants were randomly clarified into the training set and the validation set. Receiver operating characteristic (ROC) analysis has revealed that the level ratio of glycopeptides (G2G3/G2G3S4) at the sites of Asn207/211 has potential capability to distinguish BLDs from NSCLC, with the sensitivity of 74.4%, the specificity of 82.8%, and the area under curve (AUC) of 0.805.

Conclusion: The glycosylation of DSHp-β can distinguish NSCLC from BLDs with high diagnostic accuracy compared with current clinical available serum markers.

Differentially expressed serum host proteins in hepatitis B and C viral infections

Hepatitis B virus (HBV) and Hepatitis C virus (HCV) infection often lead to hepatocellular carcinoma (HCC), which is mostly detected in advanced stage. Hence, its early detection is of paramount importance using a biomarker having sensitivity and specificity both. The present study highlights differentially expressed host proteins in response to HBV/HCV infection at different stages. Comparative proteomic study was done by two-dimensional gel electrophoresis followed by mass spectrometry. Sera from each of chronically infected, liver cirrhosis and HCC in HBV or HCV infection along with controls were selected. Analysis of functional association between differentially expressed proteins with viral hepatitis was extensively carried out. Forty-three differentially expressed spots (≥ 1.5 fold; P < 0.05) on two-dimensional gel electrophoresis were corresponded to 28 proteins by mass spectrometry in variable liver diseases. Haptoglobin protein levels were decreased upon disease progression to HCC due to HBV infection. The other proteins expressed differentially are ceruloplasmin, serum paraoxonase 1, retinol binding protein and leucine rich alpha 2 proteins in plasma maybe associated to HBV HCC. Whereas, upregulation of C4a/C4b showed it as a reliable marker in patients with end stage liver disease related to HCV infection. ApolipoproteinA1 levels in liver diseases in both HBV and HCV infection corresponding to healthy controls may be a common marker for early diagnosis and disease monitoring. Protein interaction studies by extensive pathway analysis using bioinformatics tools such as EnrichNet application and STRING revealed significant associations with specific infections.

Direct Assessment of Plasma/Serum Sample Quality for Proteomics Biomarker Investigation

Blood proteome analysis for biomarker discovery represents one of the most challenging tasks to be achieved through clinical proteomics due to the sample complexity, such as the extreme heterogeneity of proteins in very dynamic concentrations, and to the observation of proper sampling and storage conditions. Quantitative and qualitative proteomics profiling of plasma and serum could be useful both for the early detection of diseases and for the evaluation of pathological status. Two main sources of variability can affect the precision and accuracy of the quantitative experiments designed for biomarker discovery and validation. These sources are divided into two categories, pre-analytical and analytical, and are often ignored; however, they can contribute to consistent errors and misunderstanding in biomarker research. In this chapter, we review critical pre-analytical and analytical variables that can influence quantitative proteomics. According to guidelines accepted by proteomics community, we propose some recommendations and strategies for a proper proteomics analysis addressed to biomarker studies.

Glycosylation-dependent galectin-1/neuropilin-1 interactions promote liver fibrosis through activation of TGF-β- and PDGF-like signals in hepatic stellate cells

Concomitant expressions of glycan-binding proteins and their bound glycans regulate many pathophysiologic processes, but this issue has not been addressed in liver fibrosis. Activation of hepatic stellate cells (HSCs) is a rate-limiting step in liver fibrosis and is an important target for liver fibrosis therapy. We previously reported that galectin (Gal)-1, a β-galactoside-binding protein, regulates myofibroblast homeostasis in oral carcinoma and wound healing, but the role of Gal-1 in HSC migration and activation is unclear. Herein, we report that Gal-1 and its bound glycans were highly expressed in fibrotic livers and activated HSCs. The cell-surface glycome of activated HSCs facilitated Gal-1 binding, which upon recognition of the N-glycans on neuropilin (NRP)-1, activated platelet-derived growth factor (PDGF)- and transforming growth factor (TGF)-β-like signals to promote HSC migration and activation. In addition, blocking endogenous Gal-1 expression suppressed PDGF- and TGF-β1-induced signaling, migration, and gene expression in HSCs. Methionine and choline-deficient diet (MCD)-induced collagen deposition and HSC activation were attenuated in Gal-1-null mice compared to wild-type mice. In summary, we concluded that glycosylation-dependent Gal-1/NRP-1 interactions activate TGF-β and PDGF-like signaling to promote the migration and activation of HSCs. Therefore, targeting Gal-1/NRP-1 interactions could be developed into liver fibrosis therapy.

Identification of Candidate Serum Biomarkers for Schistosoma mansoni Infected Mice Using Multiple Proteomic Platforms

BACKGROUND

Schistosomiasis is an important helminth infection of humans. There are few reliable diagnostic biomarkers for early infection, for recurrent infection or to document successful treatment. In this study, we compared serum protein profiles in uninfected and infected mice to identify disease stage-specific biomarkers.

METHODS

Serum collected from CD1 mice infected with 50-200 Schistosoma mansoni cercariae were analyzed before infection and at 3, 6 and 12 weeks post-infection using three mass spectrometric (MS) platforms.

RESULTS

Using SELDI-TOF MS, 66 discriminating m/z peaks were detected between S. mansoni infected mice and healthy controls. Used in various combinations, these peaks could 1) reliably diagnose early-stage disease, 2) distinguish between acute and chronic infection and 3) diagnose S. mansoni infection regardless the parasite burden. The most important contributors to these diagnostic algorithms were peaks at 3.7, 13 and 46 kDa. Employing sample fractionation and differential gel electrophoresis, we analyzed gel slices either by MALDI-TOF MS or Velos Orbitrap MS. The former yielded eight differentially-expressed host proteins in the serum at different disease stages including transferrin and alpha 1- antitrypsin. The latter suggested the presence of a surprising number of parasite-origin proteins in the serum during both the acute (n = 200) and chronic (n = 105) stages. The Orbitrap platform also identified many differentially-expressed host-origin serum proteins during the acute and chronic stages (296 and 220 respectively). The presence of one of the schistosome proteins, glutathione S transferase (GST: 25 KDa), was confirmed by Western Blot. This study provides proof-of-principle for an approach that can yield a large number of novel candidate biomarkers for Schistosoma infection.