Mary Ann Comunale

Identification and development of fucosylated glycoproteins as biomarkers of primary hepatocellular carcinoma

Changes in N-linked glycosylation are known to occur during the development of cancer. For example, we have previously reported changes in N-linked glycosylation that occur with the development of hepatocellular carcinoma (HCC) and, through the use of glycoproteomics, identified many of those proteins containing altered glycan structures. To advance these studies and further explore the glycoproteome, we performed N-linked glycan analysis from serum samples depleted of the major acute phase proteins, followed by targeted lectin extraction of those proteins containing changes in glycosylation. Using this method, changes in glycosylation, specifically increased amounts of core and outer arm fucosylation, were observed in the depleted samples. The identities of those proteins containing core and outer arm fucose were identified in the serum of patients with HCC. The usefulness of some of these proteins in the diagnosis of HCC was determined through the analysis of over 300 patient samples using a high-throughput plate based approach. Greatest performance was achieved with fucosylated hemopexin, which had an AUROC of 0.9515 with an optimal sensitivity of 92% and a specificity of 92%.

Novel Fucosylated Biomarkers for the Early Detection of Hepatocellular Carcinoma

Changes in glycosylation, most notably fucosylation, have been associated with the development of hepatocellular carcinoma (HCC). In this report, the levels of fucosylated kininogen (Fc-Kin) and fucosylated α-1-antitrypsin were analyzed individually and in combination with the currently used marker, α-fetoprotein, and a previously identified biomarker, Golgi protein 73 (GP73), for the ability to distinguish between a diagnosis of cirrhosis and HCC. This analysis was done on serum from 113 patients with cirrhosis and 164 serum samples from patients with cirrhosis plus HCC. The levels of Fc-Kin and fucosylated α-1-antitrypsin were significantly higher in patients with HCC compared with those with cirrhosis (P < 0.0001). Greatest performance was achieved through the combination of Fc-Kin, α-fetoprotein, and GP73, giving an optimal sensitivity of 95%, a specificity of 70%, and an area under the receiver operating characteristic of 0.94. In conclusion, the altered glycosylation of serum glycoproteins can act as potential biomarkers of primary HCC when used independently or in combination with other markers of HCC. (Cancer Epidemiol Biomarkers Prev 2009;18(6):1914–21)

Linkage Specific Fucosylation of Alpha-1-Antitrypsin in Liver Cirrhosis and Cancer Patients: Implications for a Biomarker of Hepatocellular Carcinoma

Background We previously reported increased levels of protein-linked fucosylation with the development of liver cancer and identified many of the proteins containing the altered glycan structures. One such protein is alpha-1-antitrypsin (A1AT). To advance these studies, we performed N-linked glycan analysis on the five major isoforms of A1AT and completed a comprehensive study of the glycosylation of A1AT found in healthy controls, patients with hepatitis C- (HCV) induced liver cirrhosis, and in patients infected with HCV with a diagnosis of hepatocellular carcinoma (HCC). Methodology/Principal Findings Patients with liver cirrhosis and liver cancer had increased levels of triantennary glycan-containing outer arm (α-1,3) fucosylation. Increases in core (α-1,6) fucosylation were observed only on A1AT from patients with cancer. We performed a lectin fluorophore-linked immunosorbent assay using Aleuria Aurantia lectin (AAL), specific for core and outer arm fucosylation in over 400 patients with liver disease. AAL-reactive A1AT was able to detect HCC with a sensitivity of 70% and a specificity of 86%, which was greater than that observed with the current marker of HCC, alpha-fetoprotein. Glycosylation analysis of the false positives was performed; results indicated that these patients had increases in outer arm fucosylation but not in core fucosylation, suggesting that core fucosylation is cancer specific. Conclusions/Significance This report details the stepwise change in the glycosylation of A1AT with the progression from liver cirrhosis to cancer and identifies core fucosylation on A1AT as an HCC specific modification.

Increased Levels of Galactose-Deficient Anti-Gal Immunoglobulin G in the Sera of Hepatitis C Virus-Infected Individuals with Fibrosis and Cirrhosis

ABSTRACT Hepatitis B and C viruses are major causative agents of liver fibrosis, cirrhosis, and liver cancer. Using comparative glycoproteomics, we identified a glycoprotein that is altered both in amount and in glycosylation as a function of liver fibrosis and cirrhosis. Specifically, this altered glycoprotein is an immunoglobulin G (IgG) molecule reactive to the heterophilic alpha-Gal epitope [Galα-1-3Galβ1-(3)4GlcNAc-R]. While similar changes in glycosylation have been observed in several autoimmune diseases, the specific immunoglobulins and their antigen recognition profiles were not determined. Thus, we provide the first report identifying the specific antigenic recognition profile of an immunoglobulin molecule containing altered glycosylation as a function of liver disease. This change in glycosylation allowed increased reactivity with several fucose binding lectins and permitted the development of a plate-based assay to measure this change. Increased lectin reactivity was observed in 100% of the more than 200 individuals with stage III or greater fibrosis and appeared to be correlated with the degree of fibrosis. The reason for the alteration in the glycosylation of anti-Gal IgG is currently unclear but may be related to the natural history of the disease and may be useful in the noninvasive detection of fibrosis and cirrhosis.

Glycomic characterization of prostate-specific antigen and prostatic acid phosphatase in prostate cancer and benign disease seminal plasma fluids.

Prostate-specific antigen (PSA) and prostatic acid phosphatase (PAP) are glycoproteins secreted by prostate epithelial cells, and have a long clinical history of use as serum biomarkers of prostate cancers. These two proteins are present at significantly higher concentrations in seminal plasma, making this proximal fluid of the prostate a good source for purifying enough protein for characterization of prostate disease associated changes in glycan structures. With the use of seminal fluid samples representative of normal control, benign prostatic disease and prostate cancers, PAP and PSA were enriched by thiophilic absorption chromatography. Released N-linked glycan constituents from both proteins were analyzed by a combination of normal phase HPLC and MALDI-TOF spectrometry. For PSA, 40 putative glycoforms were determined, and 21 glycoforms were determined for PAP. PAP glycans were further analyzed with a hybrid triple quadrupole/linear ion trap mass spectrometer to assign specific glycoform classes to each of the three N-linked sites. The glycans identified in these studies will allow for more defined targeting of prostate disease-specific changes for PAP, PSA and other secreted prostatic glycoproteins.

N-Linked Glycosylation of the Liver Cancer Biomarker GP73

The association between elevated circulating levels of GP73 (and fucosylated GP73 in particular) and hepatocellular carcinoma suggests that a thorough analysis of the extent of GP73 glycosylation is warranted. Detailed analysis of the glycosylation patterns of such low abundance proteins are hampered by technical difficulties. Using conventional lectin affinity chromatography, we have established that three quarters of the GP73 secreted from a cell line derived from HCC is fucosylated. Using mass spectrometry, we have established that at least two of three potential sites of N‐linked glycosylation are occupied on most molecules of GP73 secreted from cultured hepatoma cells. Furthermore, the oligosaccharides added to recombinant GP73 resemble those present in the bulk of secreted protein, mostly bi‐antennary with core fucose, with a smaller fraction of tri‐ and tetra‐antennary structures. The frequency of fucosylation observed on the recombinant protein agrees well with the pattern of lectin binding of the endogenous secreted protein. Finally, we have developed a method to interrogate the glycans added to either the near full length protein or at a particular sequon, providing proof of concept that a small peptide embedded in a heterologous context can preserve both fucosylation and a high level of branching of oligosaccharides added. J. Cell. Biochem. 104: 136–149, 2008.

Small molecule inhibitors of ER α-glucosidases are active against multiple hemorrhagic fever viruses.

Host cellular endoplasmic reticulum α-glucosidases I and II are essential for the maturation of viral glycosylated envelope proteins that use the calnexin mediated folding pathway. Inhibition of these glycan processing enzymes leads to the misfolding and degradation of these viral glycoproteins and subsequent reduction in virion secretion. We previously reported that, CM-10-18, an imino sugar α-glucosidase inhibitor, efficiently protected the lethality of dengue virus infection of mice. In the current study, through an extensive structure-activity relationship study, we have identified three CM-10-18 derivatives that demonstrated superior in vitro antiviral activity against representative viruses from four viral families causing hemorrhagic fever. Moreover, the three novel imino sugars significantly reduced the mortality of two of the most pathogenic hemorrhagic fever viruses, Marburg virus and Ebola virus, in mice. Our study thus proves the concept that imino sugars are promising drug candidates for the management of viral hemorrhagic fever caused by variety of viruses.

Increased levels of tetra-antennary N-linked glycan but not core fucosylation are associated with hepatocellular carcinoma tissue.

Background: Alterations in glycosylation have long been associated with the development of cancer. In the case of primary hepatocellular carcinoma (HCC), one alteration that has often been associated is increased amounts of fucose attached to the N-glycans of serum proteins secreted by the liver. Methods: In an effort to determine the origin of this increased fucosylation, we have conducted N-linked glycan analysis of HCC tissue, the surrounding nontumor tissue, and compared this to tissue from a nondiseased adult liver. Results: Surprisingly, no difference in the level of fucosylation was observed from the three donor groups, suggesting that the increased levels of fucosylation observed in serum of those with HCC is not the result of increased synthesis of fucosylated proteins in the cancer tissue. On the other hand, increased levels of a tetra-antennary glycan were observed in the HCC tissue as compared with the surrounding tissue or to the nondiseased livers. Conclusions: This represents, to our knowledge, one of the first reports associating increased levels of branching with the development of HCC. Impact: The identification of increased levels of tetra-antennary glycan on liver tumor tissue, as opposed to adjacent or nondiseased tissue may lead to improved detection of HCC. Cancer Epidemiol Biomarkers Prev; 21(6); 925–33. ©2012 AACR.

Novel Changes in Glycosylation of Serum Apo-J in Patients with Hepatocellular Carcinoma

Background: Hepatocellular carcinoma (HCC) is one of the most common malignancies worldwide and the occurrence of HCC has more than doubled in the United States in the past decade. Early detection is considered key to reducing the mortality of HCC. Methods: Using two-dimensional gel electrophoresis and high-performance liquid chromatography we have analyzed the glycosylation of Apo-J from healthy controls, patients with liver cirrhosis, or those with HCC. Results: Apo-J in the serum from patients with HCC had decreased levels of (β-1,4) triantennary N-linked glycan compared with the healthy controls or patients with liver cirrhosis. We analyzed this change in an independent cohort of 76 patients with HCC, 32 with cirrhosis, and 43 infected with hepatitis C virus using the Datura stramonium lectin (DSL), which binds to (β-1,4) triantennary N-linked glycan. The level of DSL-reactive Apo-J allowed us to differentiate HCC from cirrhosis with an area under the receiver operating characteristic curve (AUROC) of 0.852. When Apo-J was combined with other serum biomarkers such as α-fetoprotein (AFP) and fucosylated kininogen by using a multivariate logistic regression model, the AUROC increased to 0.944, a value much greater than that observed with AFP alone (AUROC of 0.765). Conclusions: The glycosylation of Apo-J is a useful marker when used alone or in combination with outer makers for the early detection of HCC. Impact: The potential use of a combination of AFP, DSL-reactive Apo-J, and fucosylated kininogen as a biomarker of HCC would have great value in the management of patients with liver disease. Cancer Epidemiol Biomarkers Prev; 20(6); 1222–9. ©2011 AACR.

Development of recombinant Aleuria aurantia lectins with altered binding specificities to fucosylated glycans

Changes in glycosylation have long been associated with disease. While there are many methods to detect changes in glycosylation, plant derived lectins are often used to determine changes on specific proteins or molecules of interest. One change in glycosylation that has been observed by us and by others is a disease or antigen associated increase in fucosylation on N-linked glycans. To measure this change, the fucose binding Aleuria aurantia lectin (AAL) is often utilized in plate and solution based assays. AAL is a mushroom derived lectin that contains five fucose binding sites that preferentially bind fucose linked (α-1,3, α-1,2, α-,4, and α-1,6) to N-acetyllactosamine related structures. Recently, several reports by us and by others have indicated that specific fucose linkages found on certain serum biomarker glycoproteins are more associated with disease than others. Taking a site-directed mutagenesis approach, we have created a set of recombinant AAL proteins that display altered binding affinities to different analytes containing various fucose linkages.