Fucose-containing antigens in normal and neoplastic human gastric mucosa: a comparative study using lectin histochemistry and blood group immunohistochemistry

Lectins in Cervical Screening

Cervical screening in low-resource settings remains an unmet need. Lectins are naturally occurring sugar-binding glycoproteins whose binding patterns change as cancer develops. Lectins discriminate between dysplasia and normal tissue in several precancerous conditions. We explored whether lectins could be developed for cervical screening via visual inspection. Discovery work comprised lectin histochemistry using a panel of candidate lectins on fixed-human cervix tissue (high-grade cervical intraepithelial neoplasia (CIN3, n = 20) or normal (n = 20)), followed by validation in a separate cohort (30 normal, 25 CIN1, 25 CIN3). Lectin binding was assessed visually according to staining intensity. To validate findings macroscopically, near-infra red fluorescence imaging was conducted on freshly-resected cervix (1 normal, 7 CIN3), incubated with topically applied fluorescently-labelled lectin. Fluorescence signal was compared for biopsies and whole specimens according to regions of interest, identified by the overlay of histopathology grids. Lectin histochemistry identified two lectins-wheat germ agglutinin (WGA) and Helix pomatia agglutinin (HPA)-with significantly decreased binding to CIN3 versus normal in both discovery and validation cohorts. Findings at the macroscopic level confirmed weaker WGA binding (lower signal intensity) in CIN3 vs. normal for biopsies (p = 0.0308) and within whole specimens (p = 0.0312). Our findings confirm proof-of-principle and indicate that WGA could potentially be developed further as a probe for high-grade cervical disease.

The Human Glycoprotein Salivary Agglutinin Inhibits the Interaction of DC-SIGN and Langerin with Oral Micro-Organisms

Salivary agglutinin (SAG), also known as gp340 or SALSA, is a glycoprotein encoded by the Deleted in Malignant Brain Tumours 1 gene and is abundantly present in human saliva. SAG aggregates bacteria and viruses, thereby promoting their clearance from the oral cavity. The mucosa lining the oral cavity contains dendritic cells (DC) and Langerhans cells (LC), which express the C-type lectin receptors (CLR) DC-SIGN and Langerin, respectively. Both DC-SIGN and Langerin recognise mannose and fucose carbohydrate structures on pathogens and self-glycoproteins to regulate immunity and homeostasis. The purpose of this study was to investigate whether SAG interacts with these CLR and whether this interferes with the binding to oral pathogens. We show that whole parotid saliva and SAG, when coated to microplates, strongly interact with DC-SIGN and Langerin, probably via mannose and fucose structures. Also, primary human DC and LC bind parotid saliva and SAG via DC-SIGN and Langerin, respectively. Furthermore, SAG binding to DC-SIGN or Langerin prevented binding to the micro-organisms Candida albicans and Escherichia coli which express mannose and fucose-containing glycan structures. Thus, binding of saliva glycoprotein SAG to DC-SIGN and Langerin may inhibit pathogen-DC/LC interactions, and could prove to be a new immunomodulatory mechanism of SAG.

The transcription factor ATF2 promotes melanoma metastasis by suppressing protein fucosylation

Melanoma is one of the most lethal skin cancers worldwide, primarily because of its propensity to metastasize. Thus, the elucidation of mechanisms that govern metastatic propensity is urgently needed. We found that protein kinase Cε (PKCε)-mediated activation of activating transcription factor 2 (ATF2) controls the migratory and invasive behaviors of melanoma cells. PKCε-dependent phosphorylation of ATF2 promoted its transcriptional repression of the gene encoding fucokinase (FUK), which mediates the fucose salvage pathway and thus global cellular protein fucosylation. In primary melanocytes and cell lines representing early-stage melanoma, the abundance of PKCε-phosphorylated ATF2 was low, thereby enabling the expression of FUK and cellular protein fucosylation, which promoted cellular adhesion and reduced motility. In contrast, increased expression of the gene encoding PKCε and abundance of phosphorylated, transcriptionally active ATF2 were observed in advanced-stage melanomas and correlated with decreased FUK expression, decreased cellular protein fucosylation, attenuated cell adhesion, and increased cell motility. Restoring fucosylation in mice either by dietary fucose supplementation or by genetic manipulation of murine Fuk expression attenuated primary melanoma growth, increased the number of intratumoral natural killer cells, and decreased distal metastasis in murine isograft models. Tumor microarray analysis of human melanoma specimens confirmed reduced fucosylation in metastatic tumors and a better prognosis for primary melanomas that had high abundance of fucosylation. Thus, inhibiting PKCε or ATF2 or increasing protein fucosylation in tumor cells may improve clinical outcome in melanoma patients.

Fucosyltransferase 1 mediates angiogenesis in rheumatoid arthritis

OBJECTIVE

To determine the role of α(1,2)-linked fucosylation of proteins by fucosyltransferase 1 (FUT1) in rheumatoid arthritis (RA) angiogenesis.

METHODS

Analysis of α(1,2)-linked fucosylated proteins in synovial tissue (ST) samples was performed by immunohistologic staining. Expression of α(1,2)-linked fucosylated angiogenic chemokine in synovial fluid (SF) was determined by immunoprecipitation and lectin blotting. To determine the angiogenic role of α(1,2)-linked fucosylated proteins in RA, we performed human dermal microvascular endothelial cell (HMVEC) chemotaxis and Matrigel assays using sham-depleted and α(1,2)-linked fucosylated protein-depleted RA SF samples. To examine the production of proangiogenic chemokines by FUT1 in HMVECs, cells were transfected with FUT1 sense or antisense oligonucleotides, and enzyme-linked immunosorbent assay was performed. We then studied mouse lung endothelial cell (EC) chemotaxis using wild-type and FUT1 gene-deficient mouse lung ECs.

RESULTS

RA ST endothelial cells showed high expression of α(1,2)-linked fucosylated proteins compared to normal ST. The expression of α(1,2)-linked fucosylated monocyte chemoattractant protein 1 (MCP-1)/CCL2 was significantly elevated in RA SF compared with osteoarthritis SF. Depletion of α(1,2)-linked fucosylated proteins in RA SF induced less HMVEC migration and tube formation than occurred in sham-depleted RA SF. We found that blocking FUT1 expression in ECs resulted in decreased MCP-1/CCL2 and RANTES/CCL5 production. Finally, we showed that FUT1 regulates EC migration in response to vascular endothelial cell growth factor.

CONCLUSION

Our findings indicate that α(1,2)-linked fucosylation by FUT1 may be an important new target for angiogenic diseases such as RA.

Lectin microarrays identify cell-specific and functionally significant cell surface glycan markers

Glycosylation is among the most complex posttranslational modifications with an extremely high level of diversity that has made it refractory to high-throughput analyses. Despite its resistance to high-throughput techniques, glycosylation is important in many critical cellular processes that necessitate a productive approach to their analysis. To facilitate studies in glycosylation, we developed a high-throughput lectin microarray for defining mammalian cell surface glycan signatures. Using the lectin microarray we established a binary analysis of cell binding and hierarchical organization of 24 mammalian cell lines. The array was also used to document changes in cell surface glycosylation during cell development and differentiation of primary murine immune system cells. To establish the biological and clinical importance of glycan signatures, the lectin microarray was applied in two systems. First, we analyzed the cell surface glycan signatures and were able to predict mannose-dependent tropism using a model pathogen. Second, we used the glycan signatures to identify novel lectin biomarkers for cancer stem-like cells in a murine model. Thus, lectin microarrays are an effective tool for analyzing diverse cell processes including cell development and differentiation, cell-cell communication, pathogen-host recognition, and cell surface biomarker identification.

Carbohydrate expression profile of colorectal cancer cells is relevant to metastatic pattern and prognosis

Carbohydrate expression of cancer cells is closely related to the metastatic nature of colorectal cancer. In the present study we investigated the relevance of carbohydrate expression profiles of colorectal cancer cells in the primary lesion to metastatic distribution patterns as well as prognosis in 134 cases. Carbohydrate expression was estimated by histochemistry with 17 kinds of lectins and 3 kinds of Lewis-related monoclonal antibodies (MAbs), and correlations between the staining and clinicopathological parameters were examined. The results showed that lymphatic invasion, lymph node metastasis, and peritoneal metastasis correlated with staining with lectins that bind galactose/N-acetylgalactosamine residues (Gal/GalNAc) such as Maclura pomifera (MPA), Arachis hypogaea (PNA), Helix pomatia (HPA), and Vicia villosa (VVA). In contrast, hepatic metastasis correlated with staining with Anguilla anguilla lectin (AAA), anti-LewisX (LEX-2), anti-sialyl Lewisa (NS 19-9), and anti-sialyl-dimeric LewisX (FH-6) MAbs, all of which bind preferentially to fucosylated carbohydrate chains. The five-year survival rate of patients was related to the staining of cancers with MPA, HPA, FH-6 or NS19-9, and MPA- and FH-6 staining were independent prognostic factors. We conclude that carbohydrate expression profiles of cancer cells are relevant to the route of tumor cell dissemination, metastatic pattern as well as prognosis of colorectal cancer.

Lectin-binding properties of the antral and body surface mucosa in the human stomach--are the differences relevant for Helicobacter pylori affinity?

Biopsy specimens from histologically normal human gastric mucosa were examined histochemically with the use of lectins. Significant differences were found in the glycoconjugate patterns of the surface mucous cells between the body and the corresponding antrum. Two lectins (Ulex europaeus agglutinin I and Ricinus communis agglutinin I) specific for fucose and galactose residues stained the apical membrane and the intracellular (perinuclear) region of the antral mucosa more strongly than those of the body (P < 0.04). Body and antral biopsies from patients with Helicobacter pylori-positive chronic active gastritis were also studied, but the lectin patterns of Helicobacter pylori-infected body and antrum did not differ. On comparing these chronically infected gastric biopsies with normal antral mucosa, however, significant changes could be seen with the fucose-binding lectin as well as with two other lectins (succinylated concanavalin A and peanut agglutinin). These differences could have been induced directly by bacterial virulence factors or could be due to non-specific reactions to the inflammatory process.

Prognostic value of the histochemical expression of helix pomatia agglutinin in advanced colorectal cancer. A univariate and multivariate analysis

PURPOSE

The expression of helix pomatia agglutinin in advanced colorectal cancer was evaluated in order to determine whether helix pomatia agglutinin could serve as an effective prognostic indicator.

METHODS

Using the histochemical procedure, the expression of helix pomatia agglutinin was studied in 117 patients with primary colorectal cancer. Sixty of 117 patients who died of either recurrence or metastasis within two years (Group 1) after resection were compared with the other 57 patients who survived for five years or longer (Group 2).

RESULTS

The helix pomatia agglutinin-positive expression was seen in 34 cases of Group 1 and in only 15 cases of Group 2 (P < 0.01). Lymph node metastasis, lymphatic invasion, venous invasion, mucin production, and helix pomatia agglutinin expression all had a significant correlation with the prognosis in the univariate analysis; however, only lymph node metastasis, venous invasion, and helix pomatia agglutinin expression were prognostic factors with a significant difference in the multivariate analysis.

CONCLUSIONS

Histochemical expression of helix pomatia agglutinin will indeed aid in accurately predicting the prognosis of patients with advanced colorectal cancer.

Immunohistochemical demonstration of glycoconjugates bearing the type 2 chain-backbone structure in human fetal, normal and neoplastic gastrointestinal tract

Immunohistochemical distributions of carbohydrate antigens based on the type 2 chain in normal as well as fetal and neoplastic tissues of human gastrointestinal tract were investigated with a monoclonal antibody (MAb) H11 (specific for type 2 chain) alone and in combination with the two MAbs MSG15 (for alpha 2----6 sialylated type 2 chain) and IB9 (for the alpha 2----6 sialylated type 2 chain and glycoproteins having NeuAc alpha 2----6Gal-NAc), and 188C1 (for short- and long-chain Lex antigens) and FH2 (for the long-chain Lex antigen). In the pyloric mucosa of secretors, the type 2 chain is oncodevelopmentally expressed, but in non-secretors it is detected in surface mucous cells of normal gastric mucosa. The alpha 2----6 sialylation, which is confined to endocrine cells of normal pyloric mucosa, occurs in fetal and carcinoma tissues. Irrespective of the secretor status, the short- and the long-chain Lex antigens can be detected in mature and immature glandular mucous cells of normal gastric mucosa, respectively; both antigens are also expressed in fetal and carcinoma tissues. In the colon, the type 2 chain and its alpha 2----6 sialylated counterpart are expressed in an oncodevelopmental manner. The short- and the long-chain Lex antigens are significantly enhanced in colonic carcinoma. The glycoproteins with NeuAc alpha 2----6GalNAc residues appear in gastric and colonic carcinoma as well as intestinalized gastric mucosa and transitional mucosa. Thus, some of these antigens were distinctively expressed in certain epithelial cells lining the normal gastrointestinal tract depending on maturation and patients' secretor status, and some were oncodevelopmental or carcinoma-associated antigens of the human gastrointestinal tract.

Gastric dysplasia: inter-observer variation, sulphomucin staining and nucleolar organizer region counting

Gastric dysplasia is regarded as a pre-neoplastic lesion and is generally believed to have higher potential for malignant transformation with increasing grade. To obtain consistency in diagnosis and management, reproducible diagnostic criteria are needed. We have used the classification system of the International Study Group on Gastric Cancer--ISGGC and investigated the interobserver variation in histological diagnosis. A Kappa statistic of 0.579, which reflects moderate agreement, was obtained for variation between two experienced pathologists. The prevalence of type III intestinal metaplasia was studied and found to occur in 55% of dysplastic areas, but in only 9% of hyperplastic areas (P less than 0.01). In addition, the correlation of mean nucleolar organizer region (AgNOR) counts with diagnostic categorization was investigated. A significant inter-observer variation was found between an experienced pathologist and a postgraduate student and only one of the observers obtained statistically significant separation of mean AgNOR counts between the categories of high-grade dysplasia, low-grade dysplasia, atypical hyperplasia, simple hyperplasia and normal.

The use of lectins in histopathology

Lectins are proteins and glycoproteins extracted predominantly from plants which have the capacity to bind sugars specifically. This property makes them of interest for histopathology since they will bind to saccharides forming parts of glycoproteins and glycolipids of tissue constituents. Lectins have and can be used as reagents for mucin histochemistry, to identify specific cells, in the recognition of glycoprotein alterations in disease states, in studies of infectious diseases, and in the assessment of glycoconjugate alterations occurring with malignancy. They can be used for both light microscopic and ultrastructural localisation and various methods are available. It is important though, to consider the nature of the glycoconjugates under study and select lectins appropriately because of their varying specificities and binding characteristics. A panel of lectins should be used to study a particular configuration. Care should be taken with tissue fixation and processing. It must be remembered that an open and critical mind should be kept concerning interpretation of results. At the present time lectins have a limited value diagnostically, but the binding of Ulex europeus agglutinin to endothelium is certainly of value.

Hepatic sinusoidal endothelium: Ulex lectin binding

The sinusoidal endothelial cells of human liver can be identified by light and electron microscopy, but there appear to be no specific immunocytochemical markers of these cells. Among specific markers available for vascular endothelial cells in general, Ulex europaeus I lectin (UEA I) is the most sensitive. In the present study, 37 liver biopsies were examined for UEA I binding and for Factor VIII related antigen (F VIII RAg) to determine if sinusoidal endothelial cells were positive. The material included normal liver, biopsies from patients with cirrhosis and biopsies in a variety of other liver diseases. Three embryonal human livers were also included in the immunocytochemical analysis. Eleven oesophageal rings obtained at mechanical transection for variceal bleeding in cirrhotic patients were used as control tissue. Sinusoidal endothelial cells of normal liver did not stain with UEA I, but six of seven with alcoholic cirrhosis and only one of 25 non-cirrhotic liver specimens (a case of acute hepatitis with bridging necrosis) were positive. In two of the six cirrhoses the sinusoidal endothelial cells were stained for F VIII RAg as well. Embryonal sinusoidal endothelial cells were stained with UEA I but were negative for F VIII RAg. The results of the study confirm that sinusoidal endothelial cells of normal adult human liver are phenotypically different from those lining blood vessels in other sites. In cirrhosis, positive staining may be related to the transformation of hepatic sinusoids into true capillaries and thus be a marker of the severity of physiological disturbance in the liver.