Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.1.53 (sialidase)
 2,694 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Developing methods for in vitro synthesis of the carbohydrate structure Galalpha1-3Galbeta1-4GlcNAc-R (termed the alpha-galactosyl epitope) on human tumour cells may be of potential clinical significance in cancer immunotherapy. Tumour vaccines with this epitope would be opsonized in vivo by the natural anti-Gal antibody, which is present in large amounts in humans, and which interacts specifically with alpha-galactosyl epitopes. Binding of anti-Gal to alpha-galactosyl epitopes on tumour cell membranes is likely to increase uptake of the cell membranes by antigen-presenting cells, such as macrophages, via the adhesion of the Fc portion of anti-Gal to Fc receptors on these cells. This, in turn, may increase processing and presentation of tumour-associated antigens by antigen-presenting cells, and induce an effective immune response against tumour cells with these antigens. The present study describes a method for the synthesis of alpha-galactosyl epitopes on human cells (red cells used as a model) by recombinant alpha1,3galactosyltransferase (rec. alpha1,3GT) expressed in bacteria. Escherichia coli was transformed with cDNA of the luminal portion of New World monkey rec. alpha1,3GT linked to six histidines (His)6 at the N-terminus. The enzyme produced by the bacteria was isolated from bacterial lysates on a nickel-Sepharose column and eluted with imidazole. This recombinant enzyme displayed acceptor specificity similar to that of rec. alpha1,3GT produced in COS cells. Red cells were pre-treated with sialidase for exposure of N-acetyllactosamine acceptors, then subjected to rec. alpha1,3GT activity. This enzyme synthesized at least 4 x 10(4) alpha-galactosyl epitopes/red cell. These epitopes were found to be accessible for binding of anti-Gal, as well as Bandeiraea simplicifolia IB4 lectin. It is argued that the method presented can be used for the synthesis of alpha-galactosyl epitopes on membranes of autologous tumour vaccines in humans.
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PMID:alpha-galactosyl (Galalpha1-3Galbeta1-4GlcNAc-R) epitopes on human cells: synthesis of the epitope on human red cells by recombinant primate alpha1,3galactosyltransferase expressed in E.coli. 872 75

P-selectin (CD62P) is a Ca2+-dependent endogenous lectin that can be expressed by vascular endothelium and platelets. The major ligand for P-selectin on leukocytes is P-selectin glycoprotein ligand-1 (PSGL-1). P-selectin can also bind to carcinoma cells, but the nature of the ligand(s) on these cells is unknown. Here we investigated the P-selectin binding to a breast and a small cell lung carcinoma cell line that are negative for PSGL-1. We report that CD24, a mucin-type glycosylphosphatidylinositol-linked cell surface molecule on human neutrophils, pre B lymphocytes, and many tumors can promote binding to P-selectin. Latex beads coated with purified CD24 from the two carcinoma cell lines but also neutrophils could bind specifically to P-selectin-IgG. The binding was dependent on divalent cations and was abolished by treatment with O-sialoglycoprotein endopeptidase but not endoglycosidase F or sialidase. The beads were stained with a monoclonal antibody (MoAb) to CD57 (HNK-1 carbohydrate epitope) but did not react with MoAbs against the sialylLe(x/a) epitope. The carcinoma cells and CD24-beads derived from these cells could bind to activated platelets or P-selectin transfected Chinese hamster ovary cells (P-CHO) in a P-selectin-dependent manner and this binding was blocked by soluble CD24. Transfection of human adenocarcinoma cells with CD24 enhanced the P-selectin-dependent binding to activated platelets. Treatment of the carcinoma cells or the CD24 transfectant with phosphatidylinositol-specific phospholipase C reduced CD24 expression and P-selectin-IgG binding concomitantly. These results establish a role of CD24 as a novel ligand for P-selectin on tumor cells. The CD24/P-selectin binding pathway could be important in the dissimination of tumor cells by facilitating the interaction with platelets or endothelial cells.
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PMID:CD24, a mucin-type glycoprotein, is a ligand for P-selectin on human tumor cells. 912 46

The colon carcinoma cell line COLO 205 has earlier been shown to express and secrete two mucin-type glycoproteins, the leukocyte-associated sialoglycoprotein CD43 or leukosialin (named L-CanAg) and the MUC1 mucin (named H-CanAg). Both glycoproteins carry sialyl-Lewis a epitopes and could bind transfected COS cells expressing E-selectin in a Ca(2+)- and E-selectin-dependent way. Using the monoclonal antibodies C50, C241 (both against sialyl-Lewis a), and CSLEX1 (against sialyl-Lewis x), the MUC1 mucin was shown to express both sialyl-Lewis a and sialyl-Lewis x epitopes, while the CD43 mucin expressed sialyl-Lewis a and almost no sialyl-Lewis x epitopes. These two secreted glycoproteins could inhibit human polymorphonuclear leukocyte or HL-60 cell adhesion to E-selectin-transfected COS cells or IL-1 beta-stimulated human endothelial cells in vitro. The inhibitory efficiency of the MUC1 mucin was 5-10 times larger than that of the CD43 mucin, when studied on endothelial cells and comparable amounts of sample were used. Removing the sialic acids from the MUC1 or CD43 mucins by sialidase treatment abolished the inhibitory effect. Monoclonal antibodies against sialyl-Lewis a greatly and equally inhibited the binding of the MUC1 or CD43 mucins, whereas an antibody against sialyl-Lewis x (CSLEX1) showed almost no inhibitory effect. The result proposes that the sialyl-Lewis a epitope on at least some mucin-type molecules bind E-selectin better than sialyl-Lewis x and that the potency of tumor-secreted mucins to interfere with leukocyte attachment to E-selectin could be dependent on the apoprotein size or its presentation of the carbohydrate epitopes.
Tumour Biol 1997
PMID:Comparison of sialyl-Lewis a-carrying CD43 and MUC1 mucins secreted from a colon carcinoma cell line for E-selectin binding and inhibition of leukocyte adhesion. 914 14

Vitamin D3-binding protein (DBP; human DBP is known as Gc protein) is the precursor of macrophage activating factor (MAF). Treatment of mouse DBP with immobilized beta-galactosidase or treatment of human Gc protein with immobilized beta-galactosidase and sialidase generated a remarkably potent MAF, termed DBPMAF or GcMAF, respectively. The domain of Gc protein responsible for macrophage activation was cloned and enzymatically converted to the cloned MAF, designated CdMAF. In Ehrlich ascites tumor-bearing mice, tumor-specific serum alpha-N-acetylgalactosaminidase (NaGalase) activity increased linearly with time as the transplanted tumor cells grew in the peritoneal cavity. Therapeutic effects of DBPMAF, GcMAF, and CdMAF on mice bearing Ehrlich ascites tumor were assessed by survival time, the total tumor cell count in the peritoneal cavity, and serum NaGalase activity. Mice that received a single administration of DBPMAF or GcMAF (100 pg/mouse) on the same day after transplantation of tumor (1 x 10(5) cells) showed a mean survival time of 35 +/- 4 days, whereas tumor-bearing controls had a mean survival time of 16 +/- 2 days. When mice received the second DBPMAF or GcMAF administration at day 4, they survived more than 50 days. Mice that received two DBPMAF administrations, at days 4 and 8 after transplantation of 1 x 10(5) tumor cells, survived up to 32 +/- 4 days. At day 4 posttransplantation, the total tumor cell count in the peritoneal cavity was approximately 5 x 10(5) cells. Mice that received two DBPMAF administrations, at days 0 and 4 after transplantation of 5 x 10(5) tumor cells, also survived up to 32 +/- 4 days, while control mice that received the 5 x 10(5) ascites tumor cells only survived for 14 +/- 2 days. Four DBPMAF, GcMAF, or CdMAF administrations to mice transplanted with 5 x 10(5) Ehrlich ascites tumor cells with 4-day intervals showed an extended survival of at least 90 days and an insignificantly low serum NaGalase level between days 30 and 90.
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PMID:Immunotherapy of BALB/c mice bearing Ehrlich ascites tumor with vitamin D-binding protein-derived macrophage activating factor. 918 19

To clarify the relation between the mechanism of apoptosis in tumor tissues and sialic acids on the termini of sugar chains of glycoconjugates, a case of squamous cell carcinoma was examined using immunohistochemistry and glycohistochemistry. Immunohistochemistry and in situ hybridization histochemistry suggested that sialylation by the sialyltransferase in dominant in tumor cells, whereas hydrolysis of sialic acids by the sialidase is dominant in apoptotic bodies. Lectin histochemistry revealed that sialic acid alpha 2, 3 galactose beta 1, 3 N-acetylgalactosamine (Gal beta 1, 3 GalNAc) is present on the surfaces of tumor cells, and Gal beta 1, 3 GalNAc is present on those of apoptotic bodies. The exposed Gal beta 1, 3 GalNAc owing to the decrease in sialic acids on the surfaces of apoptotic bodies may be recognized by the C-type lectin on the macrophage for phagocytosis.
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PMID:[Glycohistochemical analysis of apoptotic bodies in eyelid tumor]. 925 24

Oncogenic transformation is often accompanied by alterations of glycosylation on a tumor cell's surface, which may contribute to uncontrolled cell growth. The sialoglycans and degree of sialylation on the cell surface are of increasing interest because of their possible role in metastasis and tissue invasion. Since primary tumors and metastases may differ in the degree of sialylation, we examined the expression of sialic acid as a terminal constituent of lactosaminyl glycans on the cell surfaces of 30 cervical lymph-node metastases and 30 squamous-cell carcinomas of the oropharynx and oral cavity. Cell-surface sialylation was determined by a new histobiochemical assay on cryostat sections and was based on the enzymatic introduction of a fluorescence-labelled sialic acid into lactosaminyl type (Gal-beta 1-4 GlcNAc) oligosaccharide chains of cell-surface-expressed glycoproteins. To this end, tissues were incubated in the presence of 5-acetamido-9-deoxy-9-fluoresceinyl-thioureido neuraminic acid (CMP-9-fluoresceinyl-NeuAc) and alpha-2,6-sialyltransferase. In order to compare the degree of sialylation with the potential total amount of sialylation sites, pretreatment with sialidase for desialylation was required. We observed a significantly higher amount of lactosaminyl-type binding sites for sialic acid on metastases compared to the primary tumors (P = 0.001), indicating a lower degree of sialylation in metastases. In primary tumors no correlation was seen between the amount of binding sites and tumor localization, TNM stage or histologic grading. Pretreatment of specimens with sialidase demonstrated a significant degree of sialylation on both primary tumors and lymph-node metastases, but no difference between primary tumors and metastases. When tumor stroma of primary tumors and metastases was compared, tumor cells showed a higher degree of free binding sites for sialic acid, but a low degree of sialylation. Our results suggest that differences in the degree of sialylation of glycoconjugates on a tumor cell's surface may play an important role in the process of cell metastasis. Our histobiochemical method turned out to be very reliable, effective and readily performed.
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PMID:A new histobiochemical method to analyze sialylation on cell-surface glycoproteins of head and neck squamous-cell carcinomas. 943 13

Squamous cell carcinomas of the head and neck have been found to show a high expression of the receptor for epidermal growth factor (EGF). This overexpression of the receptor has been associated with malignant transformation of cells, although there is still debate as to what extent this receptor takes part in the proliferation of malignant cells and which function it fulfills. The factors which determine receptor-ligand interaction are also not clearly defined. That the extracellular domain of the EGF receptor carries carbohydrate or sialoglycan structures might be important for function of the receptor. Since tumor specific enzymes can possibly alter such structures, it was the aim of our study to investigate the role of these structures on the EGF receptor during the proliferation of head and neck carcinomas. We used the human laryngeal squamous carcinoma cell line HLaC 79 and altered, for the first time, specific glycan structures with sialidase alpha-2,3 and alpha-2,6, causing desialylation. Changes were also produced by endo-beta-galactosidase and sialyltransferase. Findings were monitored by labeling with bromo-deoxyuridine. To determine receptor affinity, 125I-labeled EGF was employed. Results showed that both cell proliferation and receptor affinity depended on the level of sialylation of the receptor carbohydrate side chains. Desialylation led to a statistically significant reduction of tumor cell proliferation to 65 +/- 33% (P < 0.01), while receptor affinity decreased to 70 +/- 26% (P < 0.01). The importance of EGF receptor for the proliferation of malignant cells seems to depend on the level of sialylation of glycan structures on receptor protein. A release of enzymes by tumor cells may then produce auto-control of tumor proliferation on its own.
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PMID:Role of sialoglycan structures for the function of the epidermal growth factor receptor and the in vitro proliferation of head and neck cancer. 980 61

Four newly developed monoclonal antibodies (MAbs) are characterized using flowcytometry, enzyme-linked immunoadsorbent assay (ELISA), immunoprecipitation and Western blots, carbohydrate epitope mapping, glycosidase cleavage, and competition binding assays. Their effects on selectin binding to myeloid cells was tested. These MAbs react only with myeloid cells. MAbs CI-1, BU60, and HIM95 recognize epitopes expressed by CD11/CD18 (beta2) integrins, while HI247 and CSLEX1 do not. The epitopes require Lewis x [Galbeta1-4 (Fucalpha1-3)GlcNAc] based on reactivity with oligosaccharide-polyacrylamide-biotin or oligosaccharide-BSA conjugates. MAb HI247 recognizes a related structure, sialyl-Lewis x, NeuAcalpha2-3GaLbeta1-4(Fucalpha1-3)GlcNAc. The three MAbs against Lewis x show some minor differences in their reactivity such as recognizing their antigens on CD11/CD18 integrins after endo-beta-galactosidase treatment and recognizing free Lewis x. The hydroxyl group on C-3 of the terminal galactose is important for recognition by MAb CI-1, BU60, and HIM95 as its substitution with sulfo group of sialic acid abolishes the binding of these MAbs. The C-3 sialic acid is crucial for the binding of MAb HI247. Its replacement by sulphate or its cleavage by sialidase eliminates recognition by this MAb. MAbs HI247 and CSLEX-1 did not react in ELISA with immobilized CD11/CD18, suggesting that the majority of sialyl Lewis x on CD11/CD18 molecules may have sialic acid 6-linked rather than 3-linked to galactose. Unexpectedly, MAb BU60 inhibited binding of P-selectin mu chain chimera to HL-60 or U937 cells, while CI-1, HIM95 and three other defined anti-Lewis x MAbs (6C7, M6-1 and LeuM1) did not. MAb HI247 inhibited binding of both E- and P-selectin chimeras to these cell lines more effectively than several characterized MAbs (CSLEX-1, FH6, HECA-452) to sialyl Lewis x and related oligosaccharides. Certain combinations of these anticarbohydrate MAbs had additive inhibitory effects on selectin binding, suggesting a potential application of these new MAbs in cell adhesion/migration and tumor metastasis studies.
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PMID:Novel monoclonal antibodies to putative selectin carbohydrate ligands that inhibit selectin binding to myeloid cells. 987 90

Glycosphingolipids expressed in cancer cells have been implicated in the modulation of tumor cell growth through their interaction with transmembrane signaling molecules such as growth factor receptors. For glycosphingolipids to interact with growth factor receptors, the presence of sialic acid seems to be essential. Stable transfection of a gene encoding a soluble Mr 42,000 sialidase into a human epidermoid carcinoma cell line (A431) provided an approach by which the level of terminal lipid-bound sialic acid on the cell surface could be altered. In the sialidase-positive clones, the level of ganglioside GM3 was diminished, and little change was observed in protein sialylation. Sialidase-transfected cells grew faster than control cells. Sialidase expression did not modify the binding of epidermal growth factor (EGF) to its receptor but enhanced EGF receptor (EGFR) tyrosine autophosphorylation as compared to that of parental cells or cells transfected with the vector (pcDNA3) alone. Moreover, the phosphorylation of the EGFR, as well as other protein substrates, was observed at low EGF concentrations, suggesting an increase in the receptor kinase sensitivity. These data provided evidence that changes in ganglioside expression in cancer cells by appropriate gene transfection can dramatically affect EGFR kinase activity. Hence, the modulation of ganglioside expression may represent an approach to alter tumor cell growth.
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PMID:Sialidase gene transfection enhances epidermal growth factor receptor activity in an epidermoid carcinoma cell line, A431. 989 12

Cancerous cells secrete alpha-N-acetylgalactosaminidase (NaGalase) into the blood stream, resulting in deglycosylation of serum vitamin D3-binding protein (known as Gc protein), which is a precursor for macrophage activating factor (MAF). Incubation of Gc protein with immobilized beta-galactosidase and sialidase generates the most potent macrophage activating factor (designated GcMAF). Administration of GcMAF to cancer-bearing hosts can bypass the inactivated MAF precursor and act directly on macrophages for efficient activation. Therapeutic effects of GcMAF on Ehrlich ascites tumor-bearing mice were assessed by survival time and serum NaGalase activity, because serum NaGalase activity was proportional to tumor burden. A single administration of GcMAF (100 pg/mouse) to eight mice on the same day after transplantation of the tumor (5 x 10(5) cells) showed a mean survival time of 21 +/- 3 days for seven mice, with one mouse surviving more than 60 days, whereas tumor-bearing controls had a mean survival time of 13 +/- 2 days. Six of the eight mice that received two GcMAF administrations, at Day 0 and Day 4 after transplantation, survived up to 31 +/- 4 days whereas, the remaining two mice survived for more than 60 days. Further, six of the eight mice that received three GcMAF administrations with 4-day intervals showed an extended survival of at least 60 days, and serum NaGalase levels were as low as those of control mice throughout the survival period. The cure with subthreshold GcMAF-treatments (administered once or twice) of tumor-bearing mice appeared to be a consequence of sustained macrophage activation by inflammation resulting from the macrophage-mediated tumoricidal process. Therefore, a protracted macrophage activation induced by a few administrations of minute amounts of GcMAF eradicated the murine ascites tumor.
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PMID:Antitumor effect of vitamin D-binding protein-derived macrophage activating factor on Ehrlich ascites tumor-bearing mice. 989 64


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