Antibody-overlay Lectin Microarray Research Articles

Differential Glycoform Analysis of MUC1 Derived from Biological Specimens Using an Antibody-Overlay Lectin Microarray.

The association between altered glycosylation of MUC1 and various disease events has sparked significant interest. However, analytical technologies to investigate the disease-related glycoforms of endogenous MUC1 in blood and tissue specimens are limited. Therefore, we devised a reliable technique for differential analysis of endogenous MUC1 glycoforms based on an antibody-assisted lectin microarray. Its highly sensitive detection aids in analyzing soluble MUC1 from relatively small amounts of serum via a simple enrichment process. Micro-/macro-dissection of the MUC1-positive region is combined with glycoform analysis of the membrane-tethered MUC1. Thus, we have optimized the protocol for sample qualification using immunohistochemistry, sample pretreatment for tissue sections, protein extraction, purification via immunoprecipitation, and the antibody-overlay lectin microarray, which are sequentially essential for differential glycoform analysis of endogenous MUC1.

Assessment of tumor characteristics based on glycoform analysis of membrane-tethered MUC1

Clinical tissue specimens are useful for pathological diagnosis, which is, in some cases, supported by visualization of biomolecule localization. In general, diagnostic specificity in molecular pathology is increased by the acquisition of a probe to distinguish the modification of isomers. Although glycosylation is one of the candidate modifications in a protein, comparative glycan analysis of disease-associated proteins derived from a single tissue section is still challenging because of the lack of analytical sensitivity. Here we demonstrate a possible method for differential glycoform analysis of an endogenous tumor-associated glycoprotein MUC1 by an antibody-overlay lectin microarray. Tissue sections (5 μm thick) of patients with cholangiocarcinoma (CCA; n=21) and pancreatic ductal adenocarcinoma (PDAC; n=50) were stained with an anti-MUC1 antibody MY.1E12 that was established as a monoclonal antibody recognizing an MUC1 glycosylation isoform with a sialyl-core 1 structure (NeuAcα2-3galactosyl β1-3-N-acetylgalactosamine). MY.1E12-positive tissue areas (2.5 mm2) were selectively dissected with a laser capture microdissection procedure. The membrane MUC1 was enriched by immunoprecipitation with MY.1E12 and subjected to lectin microarray analysis. Even though the reactivities of MY.1E12 between CCA and PDAC were similar, the lectin-binding patterns varied. We found Maackia amurensis leukoagglutinin and pokeweed lectin distinguished MY.1E12-reactive MUC1 of CCA from that of PDAC. Moreover, MUC1 with M. amurensis hemagglutinin (MAH) reactivity potentially reflected the degree of malignancy. These results were confirmed with MAH-MY.1E12 double fluorescent immunostaining. These glycan changes on MUC1 were detected with high sensitivity owing to the cluster effect of immobilized lectins on a tandem repeat peptide antigen covered with highly dense glycosylation such as mucin. Our approach provides the information to investigate novel glycodynamics in biology, for example, glycoalteration, as well as diseases related to not only MUC1 but also other membrane proteins.

Alteration of matrix metalloproteinase-3 O-glycan structure as a biomarker for disease activity of rheumatoid arthritis.

BackgroundNearly all secreted proteins are glycosylated, and serum glycoproteins that exhibit disease-associated glycosylation changes have potential to be biomarkers. In rheumatoid arthritis (RA), C-reactive protein (CRP), and matrix metalloproteinase-3 (MMP-3) are widely used as serologic biomarkers, but they lack sufficient specificity or precision. We performed comparative glycosylation profiling of MMP-3 using a recently developed antibody-overlay lectin microarray technology that allows semicomprehensive and quantitative analysis of specific protein glycosylation to develop an RA-specific disease activity biomarker.MethodsSerum was taken from patients with RA (n = 24) whose disease activity was scored using composite measures, and MMP-3 was immunoprecipitated and subjected to lectin microarray analysis. A disease activity index (DAI) based on lectin signal was developed and validated using another cohort (n = 60). Synovial fluid MMP-3 in patients with RA and patients with osteoarthritis (OA) was also analyzed.ResultsIntense signals were observed on a sialic acid-binding lectin (Agrocybe cylindracea galectin [ACG]) and O-glycan-binding lectins (Jacalin, Agaricus bisporus agglutinin [ABA], and Amaranthus caudatus agglutinin [ACA]) by applying subnanogram levels of serum MMP-3. ACG, ABA, and ACA revealed differences in MMP-3 quantity, and Jacalin revealed differences in MMP-3 quality. The resultant index, ACG/Jacalin, correlated well with disease activity. Further validation using another cohort confirmed that this index correlated well with several DAIs and their components, and reflected DAI changes following RA treatment, with correlations greater than those for MMP-3 and CRP. Furthermore, MMP-3, which generated a high ACG/Jacalin score, accumulated in synovial fluid of patients with RA but not in that of patients with OA. Sialidase digestion revealed that the difference in quality was derived from O-glycan α-2,6-sialylation.ConclusionsThis is the first report of a glycoprotein biomarker using glycan change at a local lesion to assess disease activity in autoimmune diseases. Differences in the degree of serum MMP-3 α-2,6-sialylation may be a useful index for estimating disease activity.

Monoclonal Antibody LpMab-9 Recognizes O-glycosylated N-Terminus of Human Podoplanin.

Podoplanin (PDPN) induces cell invasion and cancer metastasis, and its expression in cancer cells or cancer-associated fibroblasts has been reported to be involved in poor prognosis of several cancers including malignant gliomas and lung cancers. PDPN is also expressed in normal cells such as lymphatic endothelial cells, lung type I alveolar cells, and kidney podocytes. Many anti-PDPN monoclonal antibodies (MAbs) have been established; however, almost all anti-PDPN MAbs recognize a platelet aggregation-inducing (PLAG) domain, because the PLAG domain is known to be highly immunogenic. Here, we developed and characterized LpMab-9, a novel anti-PDPN MAb. LpMab-9 reacted with LN319 glioblastoma cells, but did not react with LN319/PDPN knock-out cells. LpMab-9 showed slight reaction with sialylated O-glycan-deficient PDPN. We identified the minimum epitope of LpMab-9 as Thr25-Asp31, which is the N-terminus of human PDPN, using Western blot analysis. Furthermore, Thr25, Gly26, Gln27, and Pro28 were shown to be critical for LpMab-9-binding to PDPN using flow cytometry. Antibody-overlay lectin microarray using LpMab-9 demonstrated that PDPN reacts with sialic acid ± core1 binders and sialo-mucin binders. Taken together, these results indicate that LpMab-9 recognizes O-glycosylation of Thr25 in the N-terminus of PDPN. LpMab-9 could be useful for uncovering the physiological function of O-glycosylated N-terminus of human PDPN.

Multiple lectin assays for detecting glyco-alteration of serum GP73 in liver diseases

Serum GP73 is a functional resident Golgi type II membrane protein with three potential N-glycosylation sites. In this study, we used multiple lectin assays to analyze glycan patterns of serum GP73 and evaluated its diagnostic value for distinguishing hepatocellular carcinoma (HCC) from liver cirrhosis (LC). Firstly, Antibody overlay lectin microarray and lectin blot were performed to observe altered glycans of GP73. Fucosylated structures were found to increase significantly in LC compared with HCC patients. Then, AAL ELISA assay using ELISA Index was utilized to measure fucosylation level of GP73 on its protein level (Fuc-GP73). ELISA Indices of 54 LC and 54 HCC patients was obtained and the area under the ROC curve (AUC) was 0.807 with a sensitivity of 85.2% and a specificity of 63.0% (cutoff of 3.182). In addition, combining Fuc-GP73 and AFP-L3 greatly improved the diagnostic accuracy (AUC = 0.953) and the diagnostic values were 94.4% sensitivity at 88.9% specificity. These data indicated that multiple lectin assays could contribute to pre-clinical evaluation of focused glycoprotein and Fuc-GP73 could act as a potential glycobiomarker complementary to AFP-L3 for discrimination of HCC from LC patients.

Differential glycan analysis of an endogenous glycoprotein: toward clinical implementation--from sample pretreatment to data standardization.

There are huge numbers of clinical specimens being stored that contain potential diagnostic marker molecules buried by the coexistence of high-abundance proteins. To utilize such valuable stocks efficiently, we must develop appropriate techniques to verify the molecules. Glycoproteins with disease-related glycosylation changes are a group of useful molecules that have long been recognized, but their application is not fully implemented. The technology for comparative analysis of such glycoproteins in biological specimens has tended to be left behind, which often leads to loss of useful information without it being recognized. In this chapter, we feature antibody-assisted lectin profiling employing antibody-overlay lectin microarray, the most suitable technology for comparative glycoanalysis of a trace amount of glycoproteins contained in biological specimens. We believe that sharing this detailed protocol will accelerate the glycoproteomics-based discovery of glyco-biomarkers that has attracted recent attention; simultaneously, it will increase the value of clinical specimens as a gold mine of information that has yet to be exploited.

Reconstruction of a robust glycodiagnostic agent supported by multiple lectin‐assisted glycan profiling

Wisteria floribunda agglutinin positive human Mac-2-binding protein (WFA(+)-hM2BP) was recently validated as a liver fibrosis glycobiomarker with a fully automated lectin-antibody sandwich immunoassay. In this study, we supplied recombinant WFA(+)-hM2BP as the standard glycoprotein and the overlaid antibody to enhance the robustness of WFA(+)-hM2BP quantification. The optimum conditions for producing recombinant WFA(+)-hM2BP were selected by cell glycome analysis based on a lectin microarray. Interlot variability of recombinant WFA(+)-hM2BP was determined using an antibody-overlay lectin microarray. Screening of anti-M2BP mAb was completed by incorporating a WFA-antibody sandwich ELISA and an antibody-overlay lectin microarray. The lectin microarray analysis revealed that human embryonic kidney 293 cells efficiently and stably produced WFA(+)-hM2BP in DMEM containing 10% FCS without any variation in the M2BP glycosylation level. A spiking experiment with recombinant WFA(+)-hM2BP was mostly effective for antibody screening. The reconstituted sandwich immunoassay was useful for the continuous quantification and cutoff index expression of serum WFA(+)-hM2BP. The multiple use of lectin-assisted glycan profiling enabled us to construct a reliable sandwich assay kit for monitoring liver fibrosis in patients with viral hepatitis. This will assist in the development pipeline for other glycodiagnostic agents.

Podocalyxin Is a Glycoprotein Ligand of the Human Pluripotent Stem Cell-Specific Probe rBC2LCN

In comprehensive glycome analysis with a high-density lectin microarray, we have previously shown that the recombinant N-terminal domain of the lectin BC2L-C from Burkholderia cenocepacia (rBC2LCN) binds exclusively to undifferentiated human induced pluripotent stem (iPS) cells and embryonic stem (ES) cells but not to differentiated somatic cells. Here we demonstrate that podocalyxin, a heavily glycosylated type 1 transmembrane protein, is a glycoprotein ligand of rBC2LCN on human iPS cells and ES cells. When analyzed by DNA microarray, podocalyxin was found to be highly expressed in both iPS cells and ES cells. Western and lectin blotting revealed that rBC2LCN binds to podocalyxin with a high molecular weight of more than 240 kDa in undifferentiated iPS cells of six different origins and four ES cell lines, but no binding was observed in either differentiated mouse feeder cells or somatic cells. The specific binding of rBC2LCN to podocalyxin prepared from a large set of iPS cells (138 types) and ES cells (15 types) was also confirmed using a high-throughput antibody-overlay lectin microarray. Alkaline digestion greatly reduced the binding of rBC2LCN to podocalyxin, indicating that the major glycan ligands of rBC2LCN are presented on O-glycans. Furthermore, rBC2LCN was found to exhibit significant affinity to a branched O-glycan comprising an H type 3 structure (Ka, 2.5 × 10(4) M(-1)) prepared from human 201B7 iPS cells, indicating that H type 3 is a most probable potential pluripotency marker. We conclude that podocalyxin is a glycoprotein ligand of rBC2LCN on human iPS cells and ES cells.

Tyramide Signal Amplification for Antibody-Overlay Lectin Microarray: A Strategy to Improve the Sensitivity of Targeted Glycan Profiling

Antibody-overlay lectin microarray (ALM) has been used for targeted glycan profiling to identify disease-related protein glycoforms. In this context, high sensitivity is desired because it allows for the identification of disease-related glycoforms that are often present at low concentrations. We describe a new tyramide signal amplification (TSA) for the antibody-overlay lectin microarray procedure for sensitive profiling of glycosylation patterns. We demonstrate that TSA increased the sensitivity of the microarray over 100 times for glycan profiling using the model protein prostate specific antigen (PSA). The glycan profile of PSA enriched from LNCAP cells, obtained at a subnanogram level with the aid of TSA, was consistent with the previous reports. We also established the glycan profile of prostate specific membrane antigen (PSMA) using the TSA and ALM. Thus, the TSA for antibody-overlay lectin microarray is a sensitive, rapid, comprehensive, and high-throughput method for targeted glycan profiling and can potentially be used for the identification of disease-related protein glycoforms.

Multilectin Assay for Detecting Fibrosis-Specific Glyco-Alteration by Means of Lectin Microarray

Despite the progress made in understanding glyco-alterations of specific glycoproteins such as α1-acid glycoprotein (AGP) associated with liver fibrosis, there has been no useful diagnostic assay with a lectin recognizing the fibrosis-specific alteration and an antibody against the core protein. We therefore developed a compatible multiple lectin-antibody sandwich immunoassay on the basis of the results obtained by the lectin microarray analysis for monitoring fibrosis. AGP-enriched fractions derived from 0.5-μL sera of 125 patients with staging-determined fibrosis (26.4% F0-F1, 25.6% F2, 24% F3, and 23.2% F4) were subjected to systematic analysis by antibody-overlay lectin microarray. Data were analyzed to statistically relate to the degree of fibrosis progression. Additionally, we applied an optimal lectin signal set on the microarray to distinguish 45 patients with cirrhosis from 43 patients with chronic hepatitis. Signal patterns of the 12 selected lectins reflected fibrosis-associated glyco-alteration of AGP. Among the 12 lectins, we found a specific lectin at each stage of fibrosis (i.e., significant fibrosis, severe fibrosis, and cirrhosis) (P < 0.0001). The test for the detection of cirrhosis showed that combinational use of 3 lectins (AOL, MAL, and DSA) on the array enhanced the diagnostic value for liver cirrhosis to 95% diagnostic sensitivity and 91% diagnostic specificity. The multiple lectin-antibody sandwich immunoassay targeting AGP enables monitoring of disease progression in chronic hepatitis patients at risk of developing hepatocellular carcinoma.

Focused Differential Glycan Analysis with the Platform Antibody-assisted Lectin Profiling for Glycan-related Biomarker Verification

Protein glycosylation is a critical subject attracting increasing attention in the field of proteomics as it is expected to play a key role in the investigation of histological and diagnostic biomarkers. In this context, an enormous number of glycoproteins have now been nominated as disease-related biomarkers. However, there is no appropriate strategy in the current proteome platform to qualify such marker candidate molecules, which relates their specific expression to particular diseases. Here, we present a new practical system for focused differential glycan analysis in terms of antibody-assisted lectin profiling (ALP). In the developed procedure, (i) a target protein is enriched from clinic samples (e.g. tissue extracts, cell supernatants, or sera) by immunoprecipitation with a specific antibody recognizing a core protein moiety; (ii) the target glycoprotein is quantified by immunoblotting using the same antibody used in (i); and (iii) glycosylation difference is analyzed by means of antibody-overlay lectin microarray, an application technique of an emerging glycan profiling microarray. As model glycoproteins having either N-linked or O-linked glycans, prostate-specific antigen or podoplanin, respectively, were subjected to systematic ALP analysis. As a result, specific signals corresponding to the target glycoprotein glycans were obtained at a sub-picomole level with the aid of specific antibodies, whereby disease-specific or tissue-specific glycosylation changes could be observed in a rapid, reproducible, and high-throughput manner. Thus, the established system should provide a powerful pipeline in support of on-going efforts in glyco-biomarker discovery.