The expression of core fucosylated E-cadherin in cancer cells and lung cancer patients: prognostic implications

Modulation of E-cadherin function and dysfunction by N-glycosylation

Several mechanisms have been proposed to explain the E-cadherin dysfunction in cancer, including genetic and epigenetic alterations. Nevertheless, a significant number of human carcinomas have been seen that show E-cadherin dysfunction that cannot be explained at the genetic/epigenetic level. A substantial body of evidence has appeared recently that supports the view that other mechanisms operating at the post-translational level may also affect E-cadherin function. The present review addresses molecular aspects related to E-cadherin N-glycosylation and evidence is presented showing that the modification of N-linked glycans on E-cadherin can affect the adhesive function of this adhesion molecule. The role of glycosyltransferases involved in the remodeling of N-glycans on E-cadherin, including N-acetylglucosaminyltransferase III (GnT-III), N-acetylglucosaminyltransferase V (GnT-V), and the α1,6 fucosyltransferase (FUT8) enzyme, is also discussed. Finally, this review discusses an alternative functional regulatory mechanism for E-cadherin operating at the post-translational level, N-glycosylation, that may underlie the E-cadherin dysfunction in some carcinomas.

L-rhamnose and L-fucose suppress cancer growth in mice

It is documented that deficient fucosylation may play an important role in the pathogenesis of cancer. Since the supplementation of L-fucose could restore fucosylation in both in vitro and in vivo conditions, our intent was to examine the effect of intraperitoneal administration of L-fucose and L-rhamnose (a similar deoxysaccharide) on tumour growth, mitotic activity and metastatic setting of a solid form of Ehrlich carcinoma as well as on the survival rate of tumour bearing mice. Both L-fucose and L-rhamnose exerted a significant suppressive effect on tumour growth (P<0.05). After 10 days of therapy, the greatest inhibition of tumour growth expressed as a percentage of controls was observed in L-rhamnose at a dose of 3 g/kg/day (by 62%) and L-fucose at a dose of 5 g/kg/day (by 47%). Moreover, the mitotic index decreased with increasing doses of L-fucose and L-rhamnose. Prolonged survival of tumour bearing mice was observed after 14 consecutive days of daily administering L-rhamnose. Its optimal dose was estimated to be 3.64 g/kg/day. L-Fucose, however, displayed only a slight effect on the survival of the mice. Our results suggest that L-fucose and especially L-rhamnose have anticancer potential. This study is the first to demonstrate the tumour-inhibitory effect of L-rhamnose.

Fucosylated glycan inhibition of human hepatocellular carcinoma cell migration through binding to chemokine receptors

SMMC-7721 hepatocellular carcinoma cells (HCC) were incubated with fucosylated glycoproteins that had been isolated from retinoic acid-treated cells by affinity chromatography. HCC migration was significantly inhibited by AAL- and LCA-glycoproteins. Glycopeptides, obtained by digestion of the glycoproteins with trypsin and papain, were found to have a similar inhibitory effect on HCC migration as the corresponding glycoproteins. The inhibitory actions of the glycoproteins were almost abolished after digestion with alpha-L-1,3/4- or alpha-L-1,2-fucosidase. Induction of HCC migration with chemokines including interleukin-8 (IL-8), lymphotactin, monocyte chemoattractant protein-1, and stroma cell-derived factor-1 was examined and IL-8 was found to be the most potent. Interestingly, the isolated glycoproteins significantly inhibited HCC migration and F-actin aggregation induced by IL-8, whereas the glycans themselves did not induce F-actin assembly. From receptor binding analysis AAL-glycan was found to bind IL-8 receptors especially CXCR2 directly and such binding could be blocked by 3'- or 2'-fucosyllactose. After CXCR2 silence by target RNAi, the cells almost lost the response to AAL-glycan inhibition. Our findings suggest that fucosylation plays an important role in the interaction between IL-8 and its receptors inducing HCC migration.

Serum 3'-sulfo-Lea indication of gastric cancer metastasis

BACKGROUND

3'-Sulfo-Le(a) is known to be the potent ligand of E-selectin which is important in cell adhesion and migration. Yet the significance of serum 3'-sulfo-Le(a) has not been explored and reported.

METHODS

Serum 3'-sulfo-Le(a) was analyzed by enzyme-linked immunosorbent assay. SPSS software was used for statistics analysis. Cell adhesion to HUVEC and sL-selectin, and cell migration were performed in gastric cancer cells SCG7901 with 3'-sulfo-Le(a) silence by Gal3ST-2 RNAi.

RESULTS

Through analysis, the mean levels of serum 3'-sulfo-Le(a) antigen were found significantly higher in 108 patients with gastric cancer than that in 74 healthy volunteers. Depth of tumor invasion, lymph node metastasis, and differentiation were noted to be significantly correlated with the expression of this antigen in gastric carcinoma. After treatment with 5-FU (5-fluorouracil) and ATRP (N-all-trans-retinoyl-L-proline), the expression of 3'-sulfo-Le(a) antigen was markedly down regulated in SCG7901 gastric cancer cells. After transfection of Gal3ST-2 RNAi, the expression of 3'-sulfo-Le(a) was silenced and the cell adhesion to HUVEC or sL-selectin, and cell migration were suppressed.

CONCLUSION

Serum 3'-sulfo-Le(a) antigen can provide important information in patients with primary gastric cancer, which might be useful as a predictive marker especially for the detection of tumor metastasis.

Glycoproteomic profiling of serum peptides in canine lymphoma and transitional cell carcinoma

Differential expression of fucosylated glycoproteins has been correlated with malignancy and metastatic potential in various types of neoplasia. Utilizing glycoproteomics techniques, changes in fucosylated serum peptides associated with naturally occurring canine lymphoma and transitional cell carcinoma (TCC) have been evaluated. In both types of neoplasia, the majority of the fucosylated peptides that changed increased with the cancer. In one lymphoma case that was examined over the course of the disease, the same fucosylated peptides that increased during pre-chemotherapy decreased during post-chemotherapy, and then subsequently increased upon recurrence of the lymphoma. When comparing all the fucosylated peptides that increased in both types of cancer, there were only two peptides in common allowing discrimination between lymphoma and TCC based on their peptide profiles. These results emphasize the prospect of glycopeptide profiling in proteomics for use in discovering a panel of non-invasive, diagnostic or prognostic biomarkers of cancer.

Serum protein N-glycans profiling for the discovery of potential biomarkers for nonalcoholic steatohepatitis

The hepatic histology in nonalcoholic fatty liver disease can vary from isolated hepatic steatosis to steatohepatitis can progress to cirrhosis and liver-related death. The aim was to evaluate the use of blood serum N-glycan fingerprinting as a tool for differential diagnosis of nonalcoholic steatohepatitis from steatosis. A group of 47 patients with NAFLD was diagnosed by clinical laboratory analysis and ultrasonography, and was studied histologically using the Brunt's scoring system. The control group included 13 healthy individuals. N-glycan profiles of serum proteins were determined by DNA sequencer-based carbohydrate analytical profiling. We have found that the concentrations of two glycans (NGA2F and NA2) and their logarithm ratio of NGA2F versus NA2 (named GlycoNashTest) were associated with the degree of NASH-related fibrosis, but had no correlation with the grade of inflammation nor steatosis severity. When used to screen NAFLD patients, GlycoNashTest could identify advanced NASH-related fibrosis (F3-F4) with the diagnosis sensitivity of 89.5% and specificity of 71.4%. The serum N-glycan profile is a promising noninvasive method for detecting NASH or NASH-related fibrosis in NAFLD patients, which could be a valuable supplement to other markers currently used in diagnosis of NASH.

A strategy for precise and large scale identification of core fucosylated glycoproteins

Core fucosylation (CF) patterns of some glycoproteins are more sensitive and specific than evaluation of their total respective protein levels for diagnosis of many diseases, such as cancers. Global profiling and quantitative characterization of CF glycoproteins may reveal potent biomarkers for clinical applications. However, current techniques are unable to reveal CF glycoproteins precisely on a large scale. Here we developed a robust strategy that integrates molecular weight cutoff, neutral loss-dependent MS(3), database-independent candidate spectrum filtering, and optimization to effectively identify CF glycoproteins. The rationale for spectrum treatment was innovatively based on computation of the mass distribution in spectra of CF glycopeptides. The efficacy of this strategy was demonstrated by implementation for plasma from healthy subjects and subjects with hepatocellular carcinoma. Over 100 CF glycoproteins and CF sites were identified, and over 10,000 mass spectra of CF glycopeptide were found. The scale of identification results indicates great progress for finding biomarkers with a particular and attractive prospect, and the candidate spectra will be a useful resource for the improvement of database searching methods for glycopeptides.

Expression and enzyme activity of alpha(1,6)fucosyltransferase in human colorectal cancer

Changes in enzyme activity and the expression levels of alpha(1,6)fucosyltransferase [alpha(1,6)FT] have been reported in certain types of malignant transformations. To develop a better understanding of the role of alpha(1,6)FT in human colorectal carcinoma (CRC), we analysed the enzyme activity in healthy and tumour tissues. alpha(1,6)FT activity was considerably higher in tumour tissue than in healthy tissue and was related to gender, lymph node metastasis, type of growth and tumour stage. We also observed a significant increase in the alpha(1,6)FT expression in tumour tissues as compared to healthy and transitional tissues, inflammatory lesions and adenomas. The immunohistochemical expression in tumour tissues was correlated with the degree of infiltration through the intestinal wall. Finally, a statistical correlation was found between enzyme activity and expression obtained by Western blot in colorectal tumours when compared in the same patient. All these findings demonstrate an alteration of alpha(1,6)FT activity and expression in CRC.

Analysis of N-glycan in serum glycoproteins from db/db mice and humans with type 2 diabetes

Glycosylation has an important role in regulating properties of proteins and is associated with many diseases. To examine the alteration of serum N-glycans in type 2 diabetes, we used the db/db mouse model. Serum N-glycans were fluorescence labeled and applied to HPLC. There were reproducible differences in N-glycan profiles between the db/db mouse model and the db/+ control. The structures of the oligosaccharides, which had changed in their amounts, were analyzed by a two-dimensional mapping method, matrix-assisted laser desorption ionization-time-of-flight mass spectrometry, and exoglycosidase digestion. Those analyses revealed an increase in the N-glycans possessing alpha1,6-fucose in the serum of db/db mice. The level of alpha1,6-fucosyltransferase mRNA was increased in the liver of the db/db mice. The ratio of a biantennary N-glycan with alpha1,6-fucose to that without alpha1,6-fucose in the liver tissue of the db/db mouse was increased relative to the db/+ control. Next, we analyzed the serum N-glycan profile in human subjects with type 2 diabetes and found an increased amount of a biantennary N-glycan that had an alpha1,6-fucose with a bisecting N-acetylglucosamine. In conclusion, the increase in alpha1,6-fucosylation is a striking change in the serum N-glycans of the db/db mice, whereas the change in the fucosylation in humans with type 2 diabetes was small, albeit statistically significant. It is likely that the change is caused, at least partially, by the increase in the alpha1,6-fucosyltransferase mRNA level in the liver. The increased alpha1,6-fucosylation may affect protein properties associated with the pathophysiology of type 2 diabetes.

N-glycosylation affects the molecular organization and stability of E-cadherin junctions

Epithelial cell-cell adhesion is mediated by E-cadherin, an intercellular N-glycoprotein adhesion receptor that functions in the assembly of multiprotein complexes anchored to the actin cytoskeleton named adherens junctions (AJs). E-cadherin ectodomains 4 and 5 contain three potential N-glycan addition sites, although their significance in AJ stability is unclear. Here we show that sparse cells lacking stable AJs produced E-cadherin that was extensively modified with complex N-glycans. In contrast, dense cultures with more stable AJs had scarcely N-glycosylated E-cadherin modified with high mannose/hybrid and limited complex N-glycans. This suggested that variations in AJ stability were accompanied by quantitative and qualitative changes in E-cadherin N-glycosylation. To further examine the role of N-glycans in AJ function, we generated E-cadherin N-glycosylation variants lacking selected N-glycan addition sites. Characterization of these variants in CHO cells, lacking endogenous E-cadherin, revealed that site 1 on ectodomain 4 was modified with a prominent complex N-glycan, site 2 on ectodomain 5 did not have a substantial oligosaccharide, and site 3 on ectodomain 5 was decorated with a high mannose/hybrid N-glycan. Removal of complex N-glycan from ectodomain 4 led to a dramatically increased interaction of E-cadherin-catenin complexes with vinculin and the actin cytoskeleton. The latter effect was further enhanced by the deletion of the high mannose/hybrid N-glycan from site 3. In MDCK cells, which produce E-cadherin, a variant lacking both complex and high mannose/hybrid N-glycans functioned like a dominant positive displaying increased interaction with gamma-catenin and vinculin compared with the endogenous E-cadherin. Collectively, our studies show that N-glycans, and complex oligosaccharides in particular, destabilize AJs by affecting their molecular organization.

Cell phenotype in normal epithelial cell lines with high endogenous N-cadherin: comparison of RPE to an MDCK subclone

PURPOSE

Unlike most monolayer epithelial cells, cultured RPE are competent to form a zonular adhesion of N- rather than E-cadherin. To determine whether other normal epithelial cells do likewise, cells with high endogenous N-cadherin were cloned from the typically E-cadherin dominant epithelial line Madin-Darby canine kidney cells (MDCK) to analyze cell and junction phenotype in the presence of N-cadherin.

METHODS

A MDCK subclonal line, clone-YH, was selected for high endogenous N-cadherin and was compared with the RPE line hTERT-RPE1 with regard to cell phenotype, cadherin gene expression and cadherin protein distribution, glycosylation state, and catenin complex composition.

RESULTS

In early cultures, hTERT-RPE1 cells are moderately epithelioid with junctional N-cadherin, but clone-YH cells are initially highly fusiform with N-cadherin in multiple sites. With time, N-cadherin in clone-YH becomes deglycosylated, resistant to detergent extraction, and zonular, and cells become epithelioid. Treatment with the N-glycosylation inhibitor tunicamycin induces an epithelioid phenotype in clone-YH, like time in culture but disrupts the hTERT-RPE1 phenotype. N-cadherin traffics to surface membranes and complexes with catenins regardless of cell type or glycosylation state, although catenin complex composition varied, showing enriched alpha-catenin under the cell-type-specific conditions in which N-cadherin was junctional. Clone-YH continued to express E-cadherin as a very minor cadherin, which trafficked to membranes but did not accumulate at junctions.

CONCLUSIONS

RPE cells are not unique in localizing N-cadherin to a zonular adhesion typical of a monolayer epithelium, because even epithelial cells derived from a typically E-cadherin dominant line (clone-YH) form a zonular N-cadherin junction if the protein is abundant. However, there are cell and cadherin differences in mechanisms of cadherin accumulation in a zonular pattern, and a previously unrecognized cell-type-specific role for protein glycosylation in epithelial phenotype development.

The E-cadherin–β-catenin complex and its implication in lung cancer progression and prognosis

The E-cadherin–β−catenin complex plays a pivotal role in epithelial cell–cell adhesion and in the maintenance of differentiated adult epithelia. Perturbation of its expression or function is widely involved in tumor progression and metastasis. Recent years have seen a rapid expansion in the understanding of the biology and the clinical relevance of the E-cadherin adhesion complex in human lung cancer. During human lung cancer progression genomic, transcriptionnal and post-transcriptionnal alterations of the E-cadherin–β-catenin adhesion system are implicated and comprise deletion of the chromosomic region 3p21 that comprise the locus of the gene encoding β-catenin, transcriptionnal downregulation of E-cadherin, cytoplasmic redistribution, phosphorylation of both proteins and proteolysis of E-cadherin. E-cadherin-inactivating mutations and oncogenic-activating mutation of β-catenin are not reported.

Gal3ST-2 involved in tumor metastasis process by regulation of adhesion ability to selectins and expression of integrins

In this study, significantly higher expression of Gal3ST-2 (Gal: 3-O-sulfotransferase-2) and 3'-sulfated glycoconjugates were observed in highly metastastic cancer cells and in larynx cancer tissues with lymph node metastasis than those in lowly metastatic cancer cells and larynx cancer tissues without metastasis (P<0.01, n=42). These results indicated that there was a marked correlation between the expression of Gal3ST-2 and tumor metastasis potential. After RNAi transfection, a striking morphological change of SMMC7721 hepatoma cells from polygon to shuttle shape and significant decrease in adhesion to sL-selectin and HUVEC were observed. Interestingly, the expression of integrin subunit alphaV was markedly downregulated and 3'-sulfated subunit alphaV almost disappeared in the transfectants, but integrin subunit beta3 almost had no change. These results suggested that Gal3ST-2 was involved in tumor metastasis process by regulation of adhesion ability to selectins and expression of integrins.

Differences in Glycosylation Patterns of Heat Shock Protein, gp96: Implications for Prostate Cancer Prevention

Heat shock protein gp96 induces a tumor-specific protective immunity in a variety of experimental tumor models. Because the primary sequences of the glycoprotein, gp96 are identical between tumor and normal tissues, the peptides associated with gp96 and/or the posttranslational modifications of gp96, determine its immunogenicity. Gp96-associated peptides constitute the antigenic repertoire of the source tissue; thus, purified gp96-peptide complexes have clinical significance as autologous cancer vaccines. However, the role of altered glycosylation and its contribution in the biological as well as immunologic activity of gp96 still remains uncharacterized. We examined the cancer-specific glycosylation patterns of gp96. To this end, monosaccharide compositions of gp96 were compared between normal rat prostate and two cancerous rat prostate tissues, nonmetastatic/androgen-dependent Dunning G and metastatic/androgen-independent MAT-LyLu, as well as two human nonmetastatic prostate cancer cell lines, androgen-dependent LnCaP and androgen-independent DU145. Marked differences were observed between the gp96 monosaccharide compositions of the normal and cancerous tissues. Furthermore, gp96 molecules from more aggressive cellular transformations were found to carry decreasing quantities of several monosaccharides as well as sum total content of neutral and amino sugars. We believe that the unique glycosylation patterns contribute to cellular phenotype and that the posttranslational modifications of gp96 may affect its functional attributes.