Serial lectin affinity chromatography demonstrates altered asparagine-linked sugar-chain structures of prostate-specific antigen in human prostate carcinoma

High-Throughput Glycomic Methods

Glycomics aims to identify the structure and function of the glycome, the complete set of oligosaccharides (glycans), produced in a given cell or organism, as well as to identify genes and other factors that govern glycosylation. This challenging endeavor requires highly robust, sensitive, and potentially automatable analytical technologies for the analysis of hundreds or thousands of glycomes in a timely manner (termed high-throughput glycomics). This review provides a historic overview as well as highlights recent developments and challenges of glycomic profiling by the most prominent high-throughput glycomic approaches, with N-glycosylation analysis as the focal point. It describes the current state-of-the-art regarding levels of characterization and most widely used technologies, selected applications of high-throughput glycomics in deciphering glycosylation process in healthy and disease states, as well as future perspectives.

Research advances and prospects of legume lectins

Lectins are widely distributed proteins having ability of binding selectively and reversibly with carbohydrates moieties and glycoconjugates. Although lectins have been reported from different biological sources, the legume lectins are the best-characterized family of plant lectins. Legume lectins are a large family of homologous proteins with considerable similarity in amino acid sequence and their tertiary structures. Despite having strong sequence conservation, these lectins show remarkable variability in carbohydrate specificity and quaternary structures. The ability of legume lectins in recognizing glycans and glycoconjugates on cells and other intracellular structures make them a valuable research tool in glycomic research. Due to variability in binding with glycans, glycoconjugates and multiple biological functions, legume lectins are the subject of intense research for their diverse application in different fields such as glycobiology, biomedical research and crop improvement. The present review specially focuses on structural and functional characteristics of legume lectins along with their potential areas of application.

Lectins applied to diagnosis and treatment of prostate cancer and benign hyperplasia: A review

Environmental factors, as well as genetic factors, contribute to the increase in prostate cancer cases (PCa), the second leading cause of cancer death in men. This fact calls for the development of more reliable, quick and low-cost early detection tests to distinguish between malignant and benign cases. Abnormal cell glycosylation pattern is a promising PCa marker for this purpose. Proteins, such as lectins can decode the information contained in the glycosylation patterns. Several studies have reported on applications of plant lectins as diagnostic tools for PCa considering the ability to differentiate it from benign cases. In addition, they can be used to detect, separate and differentiate the glycosylation patterns of cells or proteins present in serum, urine and semen. Herein, we present an overview of these studies, showing the lectins that map glycans differentially expressed in PCa, as well as benign hyperplasia (BPH). We further review their applications in biosensors, histochemical tests, immunoassays, chromatography, arrays and, finally, their therapeutic potential. This is the first study to review vegetable lectins applied specifically to PCa.

Affinity monolith chromatography: A review of general principles and recent developments

Affinity monolith chromatography (AMC) is a liquid chromatographic technique that utilizes a monolithic support with a biological ligand or related binding agent to isolate, enrich, or detect a target analyte in a complex matrix. The target-specific interaction exhibited by the binding agents makes AMC attractive for the separation or detection of a wide range of compounds. This article will review the basic principles of AMC and recent developments in this field. The supports used in AMC will be discussed, including organic, inorganic, hybrid, carbohydrate, and cryogel monoliths. Schemes for attaching binding agents to these monoliths will be examined as well, such as covalent immobilization, biospecific adsorption, entrapment, molecular imprinting, and coordination methods. An overview will then be given of binding agents that have recently been used in AMC, along with their applications. These applications will include bioaffinity chromatography, immunoaffinity chromatography, immobilized metal-ion affinity chromatography, and dye-ligand or biomimetic affinity chromatography. The use of AMC in chiral separations and biointeraction studies will also be discussed.

Study of glycosylation of prostate-specific antigen secreted by cancer tissue-originated spheroids reveals new candidates for prostate cancer detection

Prostate-specific antigen (PSA) is the most frequently used biomarker for the screening of prostate cancer. Understanding the structure of cancer-specific glycans can help us improve PSA assay. In the present study, we analysed the glycans of PSA obtained from culture medium containing cancer tissue-originated spheroids (CTOS) which have similar characteristics as that of the parent tumour to explore the new candidates for cancer-related glycoforms of PSA. The glycan profile of PSA from CTOS was determined by comparing with PSA from normal seminal plasma and cancer cell lines (LNCaP and 22Rv1) using lectin chromatography and mass spectrometry. PSA from CTOS was mostly sialylated and the content of Wisteria floribunda agglutinin reactive glycan (LacdiNAc) was similar to that of PSA derived from seminal plasma and 22Rv1. Conversely, concanavalin A (Con A)-unbound PSA was definitely detected from the three cancer origins but was almost negligible in seminal PSA. Two novel types of PSA were elucidated in the Con A-unbound fraction: one is a high molecular weight PSA with highly branched N-glycans, and the other is a low molecular weight PSA without N-glycans. Furthermore, the existence of Lewis X antigen group on PSA was indicated. These PSAs will be candidates for new cancer-related markers.

Membrane-associated gamma-glutamyl transferase and alkaline phosphatase in the context of concanavalin A- and wheat germ agglutinin-reactive glycans mark seminal prostasome populations from normozoospermic and oligozoospermic men

Background: Human seminal prostasomes are intrinsically heterogeneous extracellular vesicles (EVs) whose composition is, additionally, influenced by different physiological conditions. Aiming at the molecular properties of the prostasomal surface exemplified by glycan compositions as a possible distinction factor, we applied lectin-affinity chromatography (LAC) as a new tool for their separation. Since glycans, generally, exhibit various biological activities, introduction of glyco-parameters as reference could upgrade standardization of EVs isolated by different methods and intended for use in biomedicine.Methods: Preparations of seminal prostasomes from normozoospermic (sPro-N) and oligozoospermic (sPro-O) men were subjected to LAC on concanavalin A (Con A) and wheat germ agglutinin (WGA) columns. Prostasomes recovered in LAC-separated fractions were characterized according to the distribution of selected markers: gamma-glutamyl transferase (GGT), alkaline phosphatase (ALP), tetraspanin CD63, and total protein/glycoprotein composition.Results: Two CD63-immunoreactive populations exhibiting prostasome signature bands but differing in GGT activity and surface glycans were separated on the WGA column. Additional populations having distinct profiles of total glycoproteins and which can be tracked down by ALP activity were enriched on the Con A column. WGA-separated populations were similar in sPro-N and sPro-O, whereas Con A-separated ones were strikingly different.Conclusions: Membrane-associated gamma-glutamyl transferase and alkaline phosphatase in the context of Con A- and WGA-reactive glycans mark seminal prostasomes populations from normozoospermic and oligozoospermic men.

Analytical Application of Lectins

This review is devoted to the analytical application of carbohydrate-binding proteins called lectins. The nature of lectins and the regularities of their specificity with respect to simple sugars and complex carbohydrate-containing biomolecules are discussed. The main areas of the modern analytical application of lectins are described. Lectin-affinity chromatography, histo- and cytochemical approaches, lectin blotting, microarray, and biosensor technologies as well as microplate analysis are considered in detail. Data on the use of lectins for the detection of cells and microorganisms as well as the study of protein glycosylation are summarized. The large potential of lectins as components of analytical systems used for the identification of glycans and the characteristics of their structure are substantiated.

Intact glycopeptide characterization using mass spectrometry

Glycosylation is one of the most prominent and extensively studied protein post-translational modifications. However, traditional proteomic studies at the peptide level (bottom-up) rarely characterize intact glycopeptides (glycosylated peptides without removing glycans), so no glycoprotein heterogeneity information is retained. Intact glycopeptide characterization, on the other hand, provides opportunities to simultaneously elucidate the glycan structure and the glycosylation site needed to reveal the actual biological function of protein glycosylation. Recently, significant improvements have been made in the characterization of intact glycopeptides, ranging from enrichment and separation, mass spectroscopy (MS) detection, to bioinformatics analysis. In this review, we recapitulated currently available intact glycopeptide characterization methods with respect to their advantages and limitations as well as their potential applications.

Histochemical evaluation of postnatal lectin-binding sites in the mouse prostate

The prostate is a male accessory genital gland that plays an essential role in reproductive function. To understand the cytological characteristics of differentiating prostatic cells, we used lectin histochemistry combined with immunohistochemistry to examine the distribution of lectin-binding sites on prostatic cells during postnatal development in the mouse. During postnatal development, Hippeastrum Hybrid Lectin (HHL) lectin reacted consistently with the luminal cells of all prostatic lobes (regions), whereas the Ricinus Communis Agglutinin I (RCA-I) and Soybean Agglutinin (SBA) lectins showed remarkable differences with age, region, and cell type. We found that the lectin-binding pattern in differentiating prostatic cells acquired adult characteristics around 3 weeks after birth. The results indicate that prostatic cell differentiation during postnatal development in mice is characterized by the presence of cell- and region-specific lectin-binding sites in the prostate, suggesting that there may also be cellular and regional differences in their function. Furthermore, some lectins (HHL, RCA-I, and SBA) could provide useful markers for research into cell differentiation and for the pathological evaluation of prostatic diseases or in the diagnosis of male infertility.

Development and Applications of Lectins as Biological Tools in Biomedical Research

As a new and burgeoning area following genomics and proteomics, glycomics has become a hot issue due to its pivotal roles in many physiological and pathological processes. Glycans are much more complicated than genes or proteins since glycans are highly branched and dynamic. Antibodies and lectins are the two major molecular tools applied for glycan profiling. Though the study of antibodies and lectins started at almost the same time in 1880s, lectins gained much less attention than the antibodies until recent decades when the importance and difficulties of glycomics were realized. The present review summarizes the discovery history of lectins and their biological functions with a special emphasis on their various applications as biological tools. Both older techniques that had been developed in the last century and new technologies developed in recent years, especially lectin microarrays and lectin-based biosensors, are included in this account.

Lectin-binding sites in epithelial cells of the mouse prostate gland

The prostate is an exocrine gland in the male reproductive tract that secretes seminal fluids. To gain insight into the cytochemical properties of prostatic epithelial cells, the characteristics of glycoconjugates in mouse prostate sections were examined by lectin histochemistry and immunohistochemistry. Characteristic staining patterns were observed, depending on the type of lectins present in the epithelia. Luminal cells reacted specifically with mannose-binding lectins (Galanthus nivalis lectin, Hippeastrum hybrid lectin, Narcissus pseudonarcissus lectin) and Maclura pomifera lectin in all lobes of the prostate. Luminal cells also expressed galactose, N-acetyl-D-galactosamine (GalNAc), N-acetyl-D-glucosamine (GlcNAc), and fucose residues in the lateral and ventral lobes. Basal cells expressed GlcNAc and fucose, and reacted with Datura stramonium lectin and Aleuria aurantia lectin in all lobes. These results indicate that in the mouse prostate, the selectivity of lectin-binding sites for distinct cell types and lobe-dependent staining may relate to cellular and regional differences in function. Furthermore, some lectins selectively bound to prostatic epithelial cells, indicating their potential use as markers for the histopathological evaluation of prostatic diseases, cancer diagnosis, or male infertility.

The analysis of sialylation, N-glycan branching, and expression of O-glycans in seminal plasma of infertile men

Carbohydrates are known to mediate some events involved in successful fertilization. Although some studies on the glycosylation of seminal plasma proteins are available, the total glycan profile was rarely analyzed as a feature influencing fertilization potential. In this work we aimed to compare some glycosylation traits in seminal plasma glycoproteins of fertile and infertile men. The following findings emerge from our studies: (1) in human seminal plasma the presence and alterations of O-linked glycans were observed; (2) the expression of SNA-reactive sialic acid significantly differs between asthenozoospermia and both normozoospermic (fertile and infertile) groups; (3) the expression of PHA-L-reactive highly branched N-glycans was significantly lower in oligozoospermic patients than in both normozoospermic groups. Indication of the appropriate lectins that would enable the possibly precise determination of the glycan profile seems to be a good supplement to mass spectrum analysis. Extension of the lectin panel is useful for the further research.

Integration of the transcriptome and glycome for identification of glycan cell signatures

Abnormalities in glycan biosynthesis have been conclusively linked to many diseases but the complexity of glycosylation has hindered the analysis of glycan data in order to identify glycoforms contributing to disease. To overcome this limitation, we developed a quantitative N-glycosylation model that interprets and integrates mass spectral and transcriptomic data by incorporating key glycosylation enzyme activities. Using the cancer progression model of androgen-dependent to androgen-independent Lymph Node Carcinoma of the Prostate (LNCaP) cells, the N-glycosylation model identified and quantified glycan structural details not typically derived from single-stage mass spectral or gene expression data. Differences between the cell types uncovered include increases in H(II) and Le(y) epitopes, corresponding to greater activity of α2-Fuc-transferase (FUT1) in the androgen-independent cells. The model further elucidated limitations in the two analytical platforms including a defect in the microarray for detecting the GnTV (MGAT5) enzyme. Our results demonstrate the potential of systems glycobiology tools for elucidating key glycan biomarkers and potential therapeutic targets. The integration of multiple data sets represents an important application of systems biology for understanding complex cellular processes.

Using lectins to harvest the plasma/serum glycoproteome

Aberrant protein glycosylation has been shown to be associated with disease processes and identification of disease-specific glycoproteins and glycosylation changes may serve as potential diagnostic and therapeutic biomarkers. However despite recent advances in proteomic-based biomarker discovery, this knowledge has not yet translated into an extensive mining of the glycoproteome for potential biomarkers. The major challenge for a comprehensive glycoproteomics analysis arises primarily from the enormous complexity and the large dynamic range in protein constituent in biological samples. Methods that specifically target glycoproteins are therefore necessary to facilitate their selective enrichment prior to their identification by MS-based analysis. The use of lectins, with selective affinities for specific carbohydrate epitopes, to enrich glycoprotein fractions coupled with modern MS, have greatly enhanced the identification of the glycoproteome. On account of their ability to specifically bind cell surface carbohydrates lectins have, during the recent past, found extensive applications in elucidation of the architecture and dynamics of cell surface carbohydrates, glycoconjugate purification, and structural characterization. Combined with complementary depletion and MS technologies, lectin affinity chromatography is becoming the most widely employed method of choice for biomarker discovery in cancer and other diseases.

Glycosylation of prostate specific antigen and its potential diagnostic applications

Prostate specific antigen (PSA) assays are widely used for early detection of prostate cancer. However, those analyses are associated with considerable sensitivity and specificity problems. Several approaches have been developed to tackle this issue. PSA is a glycoprotein, which is primarily produced by the prostatic epithelial cells. Aberrant glycosylation modification of proteins is a fundamental characteristic of tumorigenesis. Study of PSA glycoforms offers interesting diagnostic perspectives. Modern technology allows us to analyze PSA glycoforms in a variety of clinical samples (serum or plasma, urine, seminal fluid, tissue). A number of novel techniques, such as lectin-based detection methods, mass spectrometry, 2-dimensional electrophoresis and capillary electrophoresis have been developed to analyze PSA glycosylation. This article reviews the technical and diagnostic aspects of PSA glycoforms.

Prostate-specific antigen/solvent interaction analysis: a preliminary evaluation of a new assay concept for detecting prostate cancer using urinary samples

OBJECTIVE

To provide preliminary clinical performance evaluation of a novel prostate cancer (CaP) assay, prostate-specific antigen/solvent interaction analysis (PSA/SIA) that focused on changes to the structure of PSA.

METHODS

Two-hundred twenty-two men undergoing prostate biopsy for accepted clinical criteria at 3 sites (University Hospitals Case Medical Center in Cleveland, Cleveland Clinic, and Veterans Administration Boston Healthcare System) were enrolled in institutional review board-approved study. Before transrectal ultrasound-guided biopsy, patients received digital rectal examination with systematic prostate massage followed by collection of urine. The PSA/SIA assay determined the relative partitioning of heterogeneous PSA isoform populations in urine between 2 aqueous phases. A structural index, K, whose numerical value is defined as the ratio of the concentration of all PSA isoforms, was determined by total PSA enzyme-linked immunosorbent assay and used to set a diagnostic threshold for CaP. Performance was assessed using receiver operating characteristic (ROC) analysis with biopsy as the gold standard.

RESULTS

Biopsies were pathologically classified as case (malignant, n=100) or control (benign, n=122). ROC performance demonstrated area under the curve=0.90 for PSA/SIA and 0.58 for serum total PSA. At a cutoff value of k=1.73, PSA/SIA displayed sensitivity=100%, specificity=80.3%, positive predictive value=80.6%, and negative predictive value=100%. No attempt was made in this preliminary study to further control patient population or selection criteria for biopsy, nor did we analytically investigate the type of structural differences in PSA that led to changes in k value.

CONCLUSION

PSA/SIA provides ratiometric information independently of PSA concentration. In this preliminary study, analysis of the overall structurally heterogeneous PSA isoform population using the SIA assay showed promising results to be further evaluated in future studies.

The cytotoxic effect of Eucheuma serra agglutinin (ESA) on cancer cells and its application to molecular probe for drug delivery system using lipid vesicles

Eucheuma serra agglutinin (ESA) derived from a marine red alga, Eucheuma serra, is a lectin that specifically binds to mannose-rich carbohydrate chains. ESA is a monomeric molecule, with a molecular weight of29,000. ESA induced cell death against several cancer cell lines, such as colon cancer Colo201 cells and cervix cancer HeLa cells. DNA ladder detection and the induction of caspase-3 activity suggested that the cell death induced by ESA against cancer cells was apoptosis. ESA bound to the cell surface of Colo201 cells in the sugar chain dependent manner. This means that the binding of ESA to the cell surface is specific for mannose-rich sugar chains recognized by ESA. The binding of ESA to the cell surface of Colo201 cells was slightly suppressed by the high concentrations of serum because of the competition with serum components possessing the mannose-rich sugar chain motifs. On the other hand, a lipid vesicle is a very useful microcapsule constructed by multilamellar structure,and adopted as drug or gene carrier. ESA was immobilized on the surface of the lipid vesicles to apply the lipid vesicles to cancer specific drug delivery system. ESA-immobilized lipid vesicles were effectively bound to cancer cell lines compared with plane vesicles.

alpha1,2-Fucosylated and beta-N-acetylgalactosaminylated prostate-specific antigen as an efficient marker of prostatic cancer

A prostate-specific antigen (PSA) is widely used as a diagnostic marker for prostate cancer (PC) because of its high specificity. However, elevated serum PSA does not occur only in PC but also in benign prostatic hyperplasia (BPH). Since the structural changes of N-glycans during carcinogenesis are common phenomena, we investigated whether PC-specific N-glycans are linked to PSA. We first analyzed the carbohydrate structures of PSA derived from seminal fluid, serum of BPH and PC patients, and PC cell line, namely, LNCaP using eight lectin-immobilized columns and then with enzyme-linked immunosorbent assay (ELISA). The fraction of serum PSA from PC patients bound to both Fucalpha1-2Gal and betaGalNAc binding Trichosanthes japonica agglutinin-II (TJA-II) column, while that from BPH patients did not exhibit this binding ability, thereby implying that there is elevated expression of alpha1,2-fucosylation and beta-N-acetylgalactosaminylation of PSA during carcinogenesis. We then performed a real-time polymerase chain reaction (PCR) and confirmed that these structural changes were responsible for the elevated expression of fucosyltransferase I (FUT1) and beta-N-acetylgalactosaminyltransferase 4(B4GALNT4). Second, we measured TJA-II-bound PSA contents and the binding ratios of TJA-II column chromatography in serum PSA samples from 40 patients of both PC and BPH. The results indicated that both TJA-II-bound PSA content and TJA-II binding ratios (%) could be used to discriminate between PC and BPH with more than 95% probability, and TJA-II-bound PSA can be regarded as a potential marker of PC.

Evaluation of the Pattern of Human Serum Glycoproteins in Prostate Cancer

Glycoprotein profiling at the level of cells, tissues and biological fluids is aimed at discovering new cancer biomarkers and also at finding specific cancer-related structural alterations of known tumor markers. In this study we comparatively evaluated the glycoprotein patterns of human prostate cancer (PCa)- and normal human sera regarding sialylation and fucosylation as structural characteristics relevant for cancer progression. Glycoproteins were isolated using affinity chromatography on Sambucus nigra agglutinin- and Lens culinaris agglutinin-columns and subsequently characterized by SDS-PAGE and on-chip normal phase-surface capture combined with surface-enhanced laser/desorption ionization time of flight mass spectrometry. Comparative analysis of the glycoproteins purified from healthy and PCa sera indicated differences and redundancy of the isolated molecules in terms of the microheterogeneity of counterpart glycans, the relative abundance and the presence/absence of particular molecular species. In PCa there was a general increase in sialylation and decrease in fucosylation of human serum glycans compared to normal sera. Taken together, the results obtained indicated that an affinity-approach based on the use of lectins of narrow specificity reduced the complexity of the examined samples and at this discovery-phase of our study pointed to specific glyco-changes that may be relevant for improving the monitoring of PCa progression.

Towards an integrated proteomic and glycomic approach to finding cancer biomarkers

Advances in mass spectrometry have had a great impact on the field of proteomics. A major challenge of proteomic analysis has been the elucidation of glycan modifications of proteins in complex proteomes. Glycosylation is the most structurally elaborate and diverse type of protein post-translational modification and, because of this, proteomics and glycomics have largely developed independently. However, given that such a large proportion of proteins contain glycan modifications, and that these may be important for their function or may produce biologically relevant protein variation, a convergence of the fields of glycomics and proteomics would be highly desirable. Here we review the current status of glycoproteomic efforts, focusing on the identification of glycoproteins as cancer biomarkers.

Differential N-glycosylation of kallikrein 6 derived from ovarian cancer cells or the central nervous system

Ovarian cancer causes more deaths than any other gynecological disorder. Perturbed glycosylation is one of the hallmarks of this malignancy. Kallikrein 6 (KLK6) elevation in serum is a diagnostic and prognostic indicator in ovarian cancer. The majority of ovarian carcinomas express high levels of KLK6, which diffuses into the circulation. Under physiological conditions, KLK6 is expressed highly in the central nervous system and found at high levels in cerebrospinal fluid from where it enters the circulation. Our aim was to characterize and compare the N-glycosylation status of this protein in ovarian cancer ascites fluid and cerebrospinal fluid. Anion-exchange chromatography was used to reveal different post-translational modifications on the two isoforms. Mobility gel shift Western blot analysis coupled with glycosidase digestion showed that the molecular weight difference between the two isoforms was because of differential glycosylation patterns. The presence of a single N-glycosylation site on KLK6 was confirmed by site-directed mutagenesis. Using a Sambucus nigra agglutinin-monoclonal antibody sandwich enzyme-linked immunosorbent assay approach, it was shown that ovarian cancer-derived KLK6 was modified with alpha2-6-linked sialic acid. The structure and composition of glycans of both KLK6 isoforms was elucidated by glycopeptide monitoring with electrospray ionization-Orbitrap tandem mass spectrometry. Therefore, the extensive and almost exclusive sialylation of KLK6 from ovarian cancer cells could lead to the development of an improved biomarker for the early diagnosis of ovarian carcinoma.

Integrated analytical strategies for the study of phosphorylation and glycosylation in proteins

The post-translational modification (PTM) of proteins is a common biological mechanism for regulating protein localization, function, and turnover. The direct analysis of modifications is required because they are not coded by genes, and thus are not predictable. Different MS-based proteomic strategies are used for the analysis of PTMs, such as phosphorylation and glycosylation, and are composed of a structural simplification step of the protein followed by specific isolation step to extract the classes of modified peptides (also called "sub-proteomes") before mass spectrometry. This specific isolation step is necessary because PTMs occur at a sub-stoichiometric level and signal suppression of the modified fractions in the mass spectrometer occurs in the presence of the more-abundant non-modified counterpart. The request of innovative analytical strategies in PTM studies is the capability to localize the modification sites, give detailed structural information on the modification, and determine the isoform composition with increased selectivity, sensitivity, and throughput. This review focuses on the description of recent integrated analytical systems proposed for the analysis of PTMs in proteins, and their application to profile the glycoproteome and the phosphoproteome in biological samples. Comments on the difficulties and usefulness of the analytical strategies are given.

Glycans as a Target in the Detection of Reproductive Tract Cancers

The significance of changes in glycosylation for the beginning, progress and outcome of different human diseases is highly recognized. In this review we summarized literature data on the alteration of glycans in cancer, especially glycoforms of tumor markers of reproductive tract cancers: prostate-specific antigen (PSA) and cancer antigen 125 (CA125). We aimed to highlight the diagnostic potential and relevance of glycan microheterogeneity and to present some novel methods for cancer detection. A computerized search of articles published up to 2007 was performed through the PubMed database. Search terms utilized included prostate/ovarian cancer glycosylation, prostate/ovarian cancer detection, PSA/CA125 glycosylation. Additional sources were identified through cross-referencing and researching in available biomedical books. The comparative studies of sugar chain structures of the PSA and CA125 indicated specific structural alterations associated with malignant transformation, in relation to glycan branching, sialylation and fucosylation. These glycan modifications should be better in distinguishing between benign and malignant conditions than the measurement of marker concentrations alone, which is widely used in practice. Cancer-associated changes in the glycosylation could yield more sensitive and discriminative diagnostic tests for reproductive tract cancer detection, i.e. for improvement of the clinical utility of known tumor markers or the discovery of new ones.

Oligosaccharide profiles of the prostate specific antigen in free and complexed forms from the prostate cancer patient serum and in seminal plasma: a glycopeptide approach

The oligosaccharide structures of prostate specific antigen (PSA) are expected to be useful in discriminating prostate cancer from benign conditions both accompanied by increased serum PSA levels. A large proportion of PSA forms a covalent complex with a glycoprotein, alpha(1)-antichymotrypsin, in human blood. In the present study, the glycan profiles of free and complexed forms of PSA from cancer patient serum and of seminal plasma PSA were compared by analyzing the glycopeptides obtained by lysylendopeptidase digestion of the electrophoretically separated PSA with mass spectrometry. The profiles of the PSA N-glycans from the free and complexed molecules were quite similar to each other and consisted of fucosylated biantennary oligosaccharides as the major class. They were mostly sialylated, and a considerable sialic acid fraction was alpha2,3-linked as determined by Streptococcus pneumoniae neuraminidase digestion of the glycopeptides. In the seminal plasma PSA, high-mannose and hybrid types of oligosaccharides were predominant, and the sialic acids attached to the latter as well as to biantennary oligosaccahrides were exclusively alpha2,6-linked because they were removed by Arthrobacter ureafaciens neuraminidase but resistant to S. pneumoniae neuraminidase. Complex-type oligosaccharides from other sources were found in the seminal plasma sample, indicating that analysis of released glycans carries a risk of being misleading. The results suggest that identification of alpha2,3-linked sialic acids on PSA potentially discriminates malignant from benign conditions, if the analysis is applied to oligosaccharides specifically attached to the N-glycosylation site of PSA in either a free or a complexed form in the serum.

The anti-tumor effect of Euchema serra agglutinin on colon cancer cells in vitro and in vivo

Eucheuma serra agglutinin (ESA) is a lectin derived from a marine red alga E. serra and binds specifically to mannose-rich sugar chains. Previous reports have indicated that ESA associates with several cancer cells via sugar chains on cell surfaces and induces apoptotic cell death. In this study, we investigated the effect of ESA on Colon26 mouse colon adenocarcinoma cells both in vitro and in vivo. ESA induced cell death against Colon26 cells in vitro, and the expression of caspase-3 and the translocation of phosphatidylserine in ESA-treated Colon26 cells suggested that this cell death was induced through apoptosis. An intravenous injection of ESA significantly inhibited the growth of Colon26 tumors in BALB/c mice; moreover, DNA fragmentation was detected in tumor cells following ESA treatment. These results indicated that ESA is effective as an anti-cancer drug not only in vitro but also in vivo. The side-effects of ESA were not considered to be serious because the decrease in body weight of the mice injected with it was negligible. These observations suggest that ESA has the potential to be an effective anti-tumor drug.

Semiautomated high-sensitivity profiling of human blood serum glycoproteins through lectin preconcentration and multidimensional chromatography/tandem mass spectrometry

We describe an effective analytical approach to identify trace glycoproteins in a small volume of human serum. The system is based on automatable affinity enrichment through silica-based lectin microcolumns and a further separation of the retained glycoproteins on a reversed-phase liquid chromatography with superficially porous packing, operating at high temperature. The fractionated sample is further directed into a 96-well plate for trypsinization and LC-MS/MS analysis. Using a major-component depleted blood serum (16 microg total protein), we were able to identify 271 glycoproteins through this analytical system.

Primary amine coding as a path to comparative proteomics

Various isotope coding strategies are being used today in the field of comparative proteomics. This article specifically reviews the strengths and limitations of various N-termini-directing strategies. N-termini-directed coding strategy allows for use of different chromatographic enrichment techniques. Since N-termini-directed coding strategies are global in nature, they can be utilized in studying PTMs as well as protein expression. Using different N-termini-directed coding strategies, both relative and absolute quantification of proteins can be achieved either in the MS mode or in the MS/MS mode. The review ends with the conclusion that significant improvements have been made in the last decade. Among various issues, a need still exists for a better understanding of the kinetic issues in proteomics, relative protein pool sizes for different proteins and the issue of stimulus-induced changes in protein aggregation. Another critical issue that needs to be addressed in great detail is the role of PTMs in regulation.

Gel-free mass spectrometry-based high throughput proteomics: Tools for studying biological response of proteins and proteomes

Revolutionary advances in biological mass spectrometry (MS) have provided a basic tool to make possible comprehensive proteomic analysis. Traditionally, two-dimensional gel electrophoresis has been used as a separation method coupled with MS to facilitate analysis of complex protein mixtures. Despite the utility of this method, the many challenges of comprehensive proteomic analysis has motivated the development of gel-free MS-based strategies to obtain information not accessible using two-dimensional gel separations. These advanced strategies have enabled researchers to dig deeper into complex proteomes, gaining insights into the composition, quantitative response, covalent modifications and macromolecular interactions of proteins that collectively drive cellular function. This review describes the current state of gel-free, high throughput proteomic strategies using MS, including (i) the separation approaches commonly used for complex mixture analysis; (ii) strategies for large-scale quantitative analysis; (iii) analysis of post-translational modifications; and (iv) recent advances and future directions. The use of these strategies to make new discoveries at the proteome level into the effects of disease or other cellular perturbations is discussed in a variety of contexts, providing information on the potential of these tools in electromagnetic field research.

Integrated lectin affinity microfluidic chip for glycoform separation

Lectin affinity chromatography was miniaturized into a microfluidic format, which results in improvement of performance, as compared to the conventional method. A lectin affinity monolith column was prepared in the microchannel of a microfluidic chip. The porous monolith was fabricated by UV-initiated polymerization of ethylene dimethacrylate (EDMA) and glycidyl methacrylate (GMA) in the presence of porogeneities, followed by immobilization of pisum sativum agglutinin (PSA) on the monolith matrix. Using electroosmosis as the driven force, lectin affinity chromatographies of three kinds of glycoprotein, turkey ovalbumin (TO), chicken ovalbumin (CO), and ovomucoid (OM), were carried out on the microfluidic system. All the glycoproteins were successfully separated into several fractions with different affinities toward the immobilized PSA. The integrated system reduces the time required for the lectin affinity chromatography reaction to approximately 3%, thus, the overall analysis time from 4 h to 400 s. Only 300 pg of glycoprotein is required for the whole separation process. Moreover, troublesome operations for lectin affinity chromatography are simplified.

Different glycan structures in prostate-specific antigen from prostate cancer sera in relation to seminal plasma PSA

Prostate-specific antigen (PSA), the tumor marker currently used for prostate cancer (PCa), is not specific enough to distinguish between PCa and benign prostate hyperplasia (BPH). Glycan processing is normally perturbed in tumors, therefore we investigated whether changes in glycosylation of PSA could be useful diagnostic indicators. Previously we determined that the glycosylation of PSA secreted by the tumor prostate cell line LNCaP differs significantly from that of PSA from seminal plasma (normal control). We therefore undertook a detailed glycan analysis of PSA derived from sera from PCa patients and, importantly, established that the glycosylation of the PCa serum PSA was significantly different from the PSA from the LNCaP cell line. In comparison with seminal plasma PSA, the fucose content of PSA from the PCa patient serum was significantly lower and there was a decrease in alpha2,3-linked sialic acid. Differences in the glycosylation of PSA derived from PCa patients' sera, seminal plasma, and LNCaP cells were further established by lectin detection, glycosylation immunosorbent assay, and two-dimensional electrophoresis. We also investigated whether the impact of glycosylation changes initiated by the tumor was reflected in the serum glycome. By comparing the glycans released from the total glycoproteins in PCa patient serum with those of normal serum we found an increase in the proportion of sialyl-Lewis x structures. Further analysis of the glycosylation of PSA from PCa and BPH sera will be required in order to determine the utility of these glycan differences to discriminate specifically between benign and malignant prostate states.

Glycosylation of urinary prostate-specific antigen in benign hyperplasia and cancer: assessment by lectin-binding patterns

OBJECTIVES

In the present study, we examined the glycosylation of urinary prostate-specific antigen (PSA) from benign prostatic hyperplasia (BPH) and prostate cancer (PCa) subjects, specifically looking at alterations in its oligosaccharide chain as a potential biomarker of these pathophysiological conditions.

DESIGN AND METHODS

First morning urine voids were collected from subjects with PCa and BPH before initiation of any treatment. Urinary PSA was characterized by ion-exchange chromatography, followed by lectin affinity chromatography on the columns using immobilized plant lectins.

RESULTS

Four isoforms of urinary PSA from both BPH and PCa samples were separated by ion-exchange chromatography. The elution profiles from lectin-affinity columns reflected molecular heterogeneity of PSA isoforms and the main differences observed were in the reactivity to Ulex europaeus agglutinin, Aleuria aurantia agglutinin, Phaseolus vulgaris erythroagglutinin and Phaseolus vulgaris leukoagglutinin.

CONCLUSIONS

The observed differences in the lectin reactivities between BPH PSA and PCa PSA may be of clinical importance in the evaluation of prostate health.

Use of Multidimensional Lectin Affinity Chromatography in Differential Glycoproteomics

This paper reports studies comparing the relative degree of sialylation among human serum glycoproteins carrying complex biantennary N-linked, hybrid, and high-mannose oligosaccharides. Comparisons were made by coupling lectin affinity selection with stable isotope coding of peptides from tryptic digests of serum. After proteolysis, samples were split and differentially acetylated with stable isotope coding agents according to either origin or the separation method by which they would be fractionated. A lectin column prepared from Sambucus nigra agglutinin (SNA) was used to select and compare the concentration of sialic acid containing glycopeptides. The relative standard deviation in quantification using this method was 4%. Using this method the concentration of sialic acid containing glycoproteins from a normal individual were compared to those in a pooled serum sample from a large number of normal individuals. It was found that sialylation varied less than 2-fold in all but four or five glycoproteins. Further studies were done on the degree of sialylation within glycoproteins. Samples labeled with the light isoform of the coding agent were applied to a set of serial lectin columns consisting of a concanavalin A (Con A) column coupled to an SNA column for selecting sialic acid appended to glycopeptides with complex biantennary N-linked, hybrid, and high-mannose glycans. In contrast, samples labeled with the heavy isoform of the coding agent were applied to a Con A lectin column alone to select glycopeptides containing complex biantennary N-linked, hybrid, and high-mannose glycans, without regard to sialylation. Glycopeptides thus selected were mixed, deglycosylated by PNGase F, and fractionated by reversed-phase chromatography (RPC). The RPC fractions were then analyzed by ESI-MS. The relative standard deviation of the method was 4%. All glycopeptides identified contained sialic acid except one. Peptides in which the relative abundance of isotopic isoforms was equal were considered to indicate that the protein parent was fully sialylated at that specific glycosylation site.

Characterization of lectins and their specificity in carcinomas-An appraisal

Lectins, a group of specific glycoproteins present in animal as well as plant cells, are used as differentiating markers to study cancers and metastatic cell lines. This property of lectins depends on the process of cellular glycosylation. Glycosylation of some of the extracellular membrane proteins and lipids maintains the cell/cell and cell/matrix interactions. Chemical alterations in glycosylation play an important role in the metastatic behavior of tumor cells. Carbohydrate residues of the membrane glycoproteins can be detected using lectins due to their binding specificity to carbohydrates. Lectins, therefore have gained an importance in the field of cancer research. Galectins, a specialized group of lectin like proteins that are Ca+ independent and galactoside binding, are also considered as differentiation markers in some specific cancers like the carcinomas of thyroid.Thus the use of lectins and galectins to identify specific carbohydrates present on cell surface help in invasion and metastasis processes.

Lectin and serum-PSA interaction as a screening test for prostate cancer

OBJECTIVES

The present investigation was designed to distinguish prostate cancer and benign prostate hyperplasia by lectin-prostate specific antigen (PSA) binding.

DESIGN AND METHODS

The quantitative precipitin method of concanavalin A (Con A)-carbohydrate interaction was explored with the serum PSA of patients suffering from prostatic complications.

RESULTS

The carbohydrate content in the precipitate after binding of Con A with serum PSA of prostate cancer was significantly lower than that of benign prostate hyperplasia. This may be due to altered sugar chain structure or less glycosylation of PSA in prostate cancer.

CONCLUSIONS

We conclude that a serum value <3.0 microg/ml of the carbohydrate content of Con A-PSA precipitate indicates strong suspicion for prostate cancer and this cut off level is effective in reducing the rate of unnecessary biopsies in men with total PSA value between 4.0 to 10.0 ng/ml.

Separation methods applicable to prostate cancer diagnosis and monitoring therapy

During the last decade, significant research has been conducted using prostate-specific antigen (PSA) in the basic and clinical sciences and many advances have occurred in the clinical use of PSA for detecting and monitoring prostate cancer (PCa). Separation methods including gel-permeation chromatography, isoelectric focusing, lectin-affinity chromatography, polyacrylamide gel electrophoresis and high-performance liquid chromatography have made significant contributions to the discovery and identification of different molecular forms of PSA. Furthermore, the measurement of free and total PSA has improved the ability of PSA to detect early PCa. However, unnecessary biopsies are still needed for men with slightly elevated PSA values. On the other hand, PSA is not adequate for staging newly diagnosed PCa and prognosticating the course in individual cases. The possible application of separation methods in the basic science of prostate cancer may be associated with identification of more cancer-specific forms of PSA and discoveries of other serum proteins useful not only for detecting, but also for staging and prognosticating PCa. Such novel markers might lead to a better understanding of PCa aggressiveness and to developments in the clinical field of treatment.

Exploiting lectin affinity chromatography in clinical diagnosis

Lectin affinity chromatography (LAC) offers a tool that aids purification of cell surface glycoconjugates in sufficient quantities so that studies addressing their structural elucidation could be carried out. It has several advantages over the conventional biochemical methods, such as immunoprecipitation and/or immunoaffinity chromatography, used for the purification of various glycoconjugates. Serial LAC (SLAC) not only helps establish the identity of a glycoprotein or allows purification of a glycoprotein to homogeneity from among a mixture of glycoproteins, but it also successfully resolves the microheterogeneity in these glycoproteins, which is an otherwise impracticable problem to address. Specific cases of the altered expression and maintenance of microheterogeneity of some of the glycoproteins in pathological conditions vis a vis during normal biology are presented. The application of LAC in (i) itself, (ii) a serial fashion, and (iii) conjunction with other techniques such as two-dimensional electrophoresis, capillary electrophoresis, mass spectrometry, etc. in the diagnosis of certain pathological conditions, and the possibility of using this knowledge in designing treatments for various diseases, is discussed.

Analysis of glycoconjugate patterns of normal and hormone-induced dysplastic Noble rat prostates, and an androgen-independent Noble rat prostate tumor, by lectin histochemistry and protein blotting

BACKGROUND

Alteration of the expression of glycoconjugates is frequently observed in tumors. However, studies on the changes of cellular glycosylation in the early premalignant stage of prostate carcinogenesis are scarce.

METHODS

The present study characterized and compared the glycoconjugates expressed in the dysplastic lateral prostate induced in Noble (Nb) rat by steroid hormones and a transplantable androgen-independent Nb rat prostatic carcinoma line (AIT) by lectin histochemistry and protein blotting.

RESULTS

The results of lectin histochemistry show that the dysplastic prostatic epithelium elaborates altered patterns of glycosylation, which are distinct from the normal secretory epithelium. Some individual cells in the dysplastic epithelium were intensely labeled by the N-acetylgalactosamine (GalNAc)-specific (agglutins from Glycine max [SBA], Helix aspera [HAA], Helix pomatia [HPA], Vicia villosa [VVA], Erythrina cristigalli [ECA]) and complex-type oligosaccharide-specific (Phaseolus vulgaris agglutin [PHA-E]) lectins, indicating that these cells contained abundant GalNAc(alpha1,3)GalNAc/Gal and Gal(beta1,4)GlcNAc(alpha1,2)Man(alpha1,6) residues. These lectins also bound to some tumor cells in the AIT, suggesting that these sugar residues are common in some dysplastic and neoplastic prostatic cells. The study has also identified several lectins (agglutins from Griffonia simplicifolia [GS-I-B4], Arachis hypogaea [PNA], Ricinus communis [RCA-I], Maackia amurensis [MAA], Sambucus nigra [SNA]), which bound only to some AIT tumor cells but not to dysplastic epithelium, indicating that alpha/betaGal and sialic acid-containing glycoconjugates are expressed by neoplastic prostatic cells. The results of lectin blottings with Triticum vulgare agglutin [S-WGA] Ulex europaeus agglutin [UEA-I] and PHA-E have identified five major glycoprotein bands (of apparent molecular weights of 116, 79, 64, 61, and 57 kDa) in the microsomal fraction of testosterone plus 17beta-estradiol (T + E2)-treated lateral prostate. These lectin-reactive bands were not detected in the AIT extracts. In the AIT microsomal extract, two glycoprotein bands of molecular weights of 58 and 46 kDa were revealed by SBA and PNA.

CONCLUSIONS

The present study shows that there is an increased expression of GalNAc(alpha1,3)GalNAc/Gal residues and triantennary complex-type oligosaccharides in the dysplastic epithelial cells as compared to normal secretory epithelial cells in rat lateral prostate. This altered expression of glycoconjugates revealed in the dysplastic epithelium indicates an aberrant glycosylation in the early premalignant stage of prostate carcinogenesis. The results also show that the AIT tumor cells are heterogeneous in their glycoconjugates and different from the dysplastic epithelial cells.