[Show abstract][Hide abstract] ABSTRACT: Galectins are mammalian carbohydrate-binding proteins that are involved in cell-cell and cell-matrix adhesion, cell migration, and growth regulation with relevance to inflammation and tumor spread. These important functions account for the interest to design suitable low molecular weight inhibitors that match the distinct modes of presentation of the carbohydrate recognition domains of the different galectin subfamilies. Using 3,5-di-(2-aminoethoxy)benzoic acid as the branching unit, wedgelike glycodendrimers with two, four, and eight lactose moieties (G1-G3) were synthesized. They were tested in solid-phase competition assays with lactose maxiclusters and various N-glycan branching profiles (miniclusters) as the matrix and also in cell assays. Prototype galectins-1 and -7, chimera-type galectin-3, a plant (AB)(2) toxin, and a lactose-binding immunoglobulin G fraction from human serum were the carbohydrate-binding targets. Potent inhibition and remarkable cluster effects were seen for the homodimeric galectin-1, especially in combination with biantennary N-glycans as the matrix. Remarkably, for the tetravalent G2 glycodendrimer, the inhibitory potency of each lactose unit reached a maximum value of 1667 relative to free lactose. In haemagglutination experiments as a model for cell adhesion, galectin-3 was markedly sensitive to increased sugar valency and a relative potency per lactose of 150 was reached. The spatial orientation of the carbohydrate recognition domains of the endogenous lectins and the branching pattern of the carbohydrates of the glycoprotein matrices used are both important factors in the design and synthesis of glycodendrimers with galectin-selective properties.
[Show abstract][Hide abstract] ABSTRACT: Galectin-3, a member of the beta-galactoside-binding lectin family, is involved in a variety of biological events including interactions with galactose-containing glycoconjugates, cell proliferation, differentiation and apoptosis. Galectin-3 appears to intervene during tumor progression and altered expression patterns have been reported in a variety of malignancies. In our study, we have examined the expression of galectin-3 in a population of 145 prostate carcinoma samples using immunohistochemistry. We found that most of the non-tumoral prostatic glands exhibited moderate immunostaining for galectin-3 localized in both nucleus and cytoplasm. In prostatic cancer cells, galectin-3 was usually not expressed or decreased compared with the normal glands. Interestingly, when galectin-3 was detected in the cancer cells, it was consistently excluded from the nucleus and only present in the cytoplasmic compartment. The latter observation was also made for prostatic intraepithelial neoplasia (PIN) cells. Furthermore, we found that the levels of galectin-3 expression in the cancer cells were significantly associated with prostate-specific antigen (PSA) relapse in univariate analysis (p = 0.044). Cytoplasmic expression of galectin-3 in the carcinoma cells was an independent predictor of disease progression in multivariate analysis, after the pathological stage and the Gleason score. Our data demonstrate that galectin-3 is generally down-regulated in human prostate carcinoma cells, and consistently excluded from the nucleus. Interestingly, specific cytoplasmic expression of galectin-3 in a subset of lesions is associated with disease progression. These results suggest that galectin-3 might play anti-tumor activities when present in the nucleus, whereas it could favor tumor progression when expressed in the cytoplasm. Further studies should determine the exact role and mechanisms by which galectin-3 differentially affects cell behavior in the different locations where it is expressed.
Preview · Article · Aug 2000 · International Journal of Cancer
[Show abstract][Hide abstract] ABSTRACT: Our previous work demonstrated the capacity of galectin-3 (a beta-galactoside binding animal lectin) to inhibit IL-5 gene expression in different cell types, but the interaction of lectin with the cells and the pathways for the inhibition process are unknown. One of the purposes of this work was to study the cellular ligand for galectin-3. We have demonstrated that galectin-3 can bind to the low affinity IgG receptor (FcgammaRII or CD32) by using different experimental approaches, such as flow cytometry, fusion protein GST technology, and with a model of FcgammaRII-deficient mice. To further analyze the interaction between FcgammaRII and galectin-3, and its implication in IL-5 gene down-regulation we used FcgammaRII-deficient mice. When PBMC from these mice were incubated with galectin-3, the expression of the IL-5 gene was unchanged. However, when PBMC from wild type mice and FcgammaRIII-deficient mice were incubated with galectin-3, IL-5 gene expression was down-regulated. Finally, we studied the implication of the negative regulatory sequence in the IL-5 gene promoter. In the presence of galectin-3, a DNA-protein complex was formed with the IL-5REIII region. This complex was not observed when unrelated oligonucleotide was used. So, galectin-3 induces a pathway, which activates a transcription factor that binds to IL-5REIII. This interaction is capable of inhibiting IL-5 gene transcription.
[Show abstract][Hide abstract] ABSTRACT: Galectin-3 is a carbohydrate-binding protein endowed with affinity for beta-galactosides. It plays a role in cell-cell and cell-matrix interactions. Furthermore, it has been hypothesized to be involved in tumor progression and metastasis. To address the role of galectin-3 in the invasive and metastatic processes, we stably overexpressed galectin-3 in human breast carcinoma cell lines, and we evaluated the influence of elevated galectin-3 expression on several cell features, including cellular homotypic and heterotypic interactions and cell survival. No differences in various parameters related with cell growth features and proliferation were detected. By contrast, we found that galectin-3 overexpressing cells, with respect to low galectin-3 expressing cells, exerted: (1) a significantly enhanced adhesion to laminin, fibronectin and vitronectin exerted both directly or via increased expression of specific integrins, e.g., alpha-4 and beta-7; (2) a remodeling of those cytoskeletal elements associated with cell spreading, i.e., microfilaments; (3) an enhanced survival upon exposure to different apoptotic stimuli, such as cytokine and radiation. Collectively, our results indicate that overexpression of galectin-3 may play a role in tumor cell invasion and metastasis by specifically influencing cell adhesion to the extracellular matrix. This may confer selective survival advantage and resistance to the particular homeless-induced apoptosis called anoikia.
Full-text · Article · Mar 2000 · International Journal of Cancer
[Show abstract][Hide abstract] ABSTRACT: Galectin-3, a member of the beta-galactoside-binding lectin family, is involved in several biological events including binding to the basement membrane glycoprotein laminin. Although the exact role of galectin-3 during the interactions between cells and laminin is not yet known, it has recently been observed that its expression is down-regulated at both the protein and the mRNA level in colon cancer tissues in correlation with progression of the disease. This study investigated the possibility that breast cancer cells might also exhibit decreased galectin-3 expression in association with their aggressiveness. The expression of galectin-3 was examined by immunoperoxidase staining, using a polyclonal antibody raised against recombinant galectin-3, in a collection of 98 human breast lesions including 12 fibroadenomas, 15 fibrocystic disease lesions, 22 in situ carcinomas, and 49 infiltrating ductal carcinomas, 19 of which had positive axillary lymph nodes. Normal breast tissue adjacent to the lesions was present in 59 biopsies. Normal breast tissue expressed high levels (3+) of galectin-3. High expression (2+ to 3+) was also found in most benign lesions examined. The expression of galectin-3 was significantly decreased in in situ carcinoma and this down-regulation was more pronounced in invasive ductal carcinoma, particularly when associated with infiltration of axillary lymph nodes. These data constitute the first observation that galectin-3 is down-regulated in breast cancer and suggest the decreased expression of this galactoside-binding lectin is associated with the acquisition of the invasive and metastatic phenotype.
No preview · Article · May 1996 · The Journal of Pathology
[Show abstract][Hide abstract] ABSTRACT: (BALB/c x SJL)F1 mice, perinatally injected with peptide-N-glyconase F-treated, deglycosylated IgE heavy chain or recombinant IgE heavy chain (CH epsilon 2-CH epsilon 4), were profoundly inhibited in antigen-specific IgE production. There exist minimally two tolerogenic IgE peptides, residing in the CH epsilon 2 and CH epsilon 4 domains. Peptide I, generated by V8 protease, comprises 39 amino acids within CH epsilon 2, beginning at amino acid 103. Peptide E begins at amino acid 312 of the CH epsilon 4 domain and extends through the CH epsilon 4 domain. The total lack of antigen-specific IgE responses in IgE peptide-treated mice was not due to overproduction of interferon-gamma, nor lack of interleukin (IL)-4, as predicted by the Th2/IL-4 paradigm for IgE production. IgE-tolerant mice exhibited comparable levels of circulating anti-IgE antibodies to those of PBS-treated control mice. IgG obtained from sera of both sources failed to inhibit IgE responses in vitro. Moreover, IgE responses of spleen cells from IgE peptides-treated mice were restored by CD4+ T cells from PBS-treated control mice. We hypothesize that regulation of antigen-specific IgE responses is mediated by CD4+ T cells which normally recognize IgE peptides on IgE precursor B cells, and can be rendered tolerant by perinatal IgE peptide treatment.
No preview · Article · May 1996 · European Journal of Immunology
[Show abstract][Hide abstract] ABSTRACT: Galectin-3 is an endogenous soluble lectin within the family called galectins that bind beta-galactosides. Homologs of the protein isolated from different sources were previously designated as IgE-binding protein (epsilon BP), CBP35, CPB30, Mac-2, RL-29, RLL, L-29, and HL-29. All are now renamed galectin-3. This lectin is widely distributed in cells and tissues of mice, rats, dogs, hamsters, and humans. Light microscopic immunohistochemistry and ultrastructural immunogold labeling methods were used to determine the distribution of galectin-3 in human mast cells of several organs, in mast cells developed in vitro from human fetal liver cells, and in human peripheral blood basophils. Immunolabeling for the protein was observed in mast cells from all sources and in basophils. The lectin was detected in the nucleus and/or the cytoplasm. The nuclear labeling was over heterochromatin whereas euchromatin was unlabeled. Cytoplasmic labeling was concentrated over secretory granules. The intensity of staining generally was greater in mast cells of skin when compared with that of mast cells in other locations and with that of basophils. Studies have indicated that in mast cells galectin-3 may be involved in promoting their adhesion to basal laminae. In this study the localization of galectin-3 in the secretory granules of human mast cells and basophils suggests that these cells may release this lectin when activated to degranulate.
No preview · Article · Jun 1995 · The Anatomical Record
[Show abstract][Hide abstract] ABSTRACT: Macrophage cell-surface protein 2 (Mac-2), a galactose specific S-type lectin identified in inflammatory macrophages, presents a high degree of homology with the rat IgE-binding protein (epsilon BP). In the present study, we show by different experimental approaches that human eosinophils can express Mac-2/epsilon BP. Flow cytometry analysis revealed that a large proportion of eosinophilic patients expressing binding sites for IgE on their eosinophil membrane, were able to bind anti-Mac-2 monoclonal antibody (mAb). Northern blot performed with eosinophil RNA hybridized with the human Mac-2 or epsilon BP cDNA probes revealed that eosinophils presented a unique transcript at 1.2 kb. Immunoprecipitation of eosinophil extracts with anti-Mac-2 mAb revealed the presence of a molecule of 29 kDa corresponding to Mac-2 protein, as well as one additional molecule of 15 kDa, absent from control alveolar macrophages. The function of these molecules was investigated in a radiolabeled IgE binding assay. Anti-Mac-2 mAb as well as galactose and lactose saccharides significantly inhibited the binding of radiolabeled human myeloma IgE protein to eosinophils. Moreover, the dose-dependent inhibition by anti-Mac-2 mAb of IgE-dependent eosinophil-mediated cytotoxicity towards parasite targets indicated the role of these IgE-binding molecules in the function of human eosinophils. These results suggest that in addition to transmembrane receptors, lectin-type molecules can participate in the IgE-dependent effector function of eosinophils.
No preview · Article · Dec 1993 · European Journal of Immunology
[Show abstract][Hide abstract] ABSTRACT: IgE-binding protein (epsilon BP) was originally identified in rat basophilic leukemia (RBL) cells by virtue of its affinity for IgE. epsilon BP is now known to be a beta-galactoside-binding lectin containing an S-type carbohydrate recognition domain. It is identical to a macrophage surface antigen, Mac-2, and lectins designated as CBP35, L-34, and RL-29, for which various functions have been suggested. Studies from other groups as well as ours have indicated that epsilon BP is secreted by cells such as macrophages and is present in extracellular fluids. We demonstrated previously that binding sites for epsilon BP are present on the surface of RBL cells. In this report, we show that epsilon BP binds to a small number of glycoprotein species on the surface of RBL cells. Significantly, one of these glycoproteins is the high-affinity IgE receptor (Fc epsilon RI). Preliminary studies showed that epsilon BP causes mediator release from RBL cells, possibly through cross-linking of Fc epsilon RI. The results suggest a function of epsilon BP as an activator of mast cells.
[Show abstract][Hide abstract] ABSTRACT: epsilon BP (for epsilon binding protein) is a M(r) 31,000 S-type animal lectin that binds to IgE and has been identified as the homologue of Mac-2, a macrophage cell-surface marker, as well as the lectins RL-29, CBP35, and L-34. The protein is composed of two domains with the amino-terminal portion containing tandem repeats of nine amino acids and the carboxyl-terminal half containing consensus sequences shared by S-type animal lectins. We determined the genomic map in both rat and mouse and isolated overlapping genomic clones that contain the 5' two-thirds of the murine gene. The remaining portion of the gene was obtained by polymerase chain reaction (PCR) amplification of genomic murine DNA followed by subcloning into plasmid vectors. The epsilon BP gene is composed of six exons separated by five introns. The entire amino-terminal repetitive sequence is contained in exon III, and the carboxyl-terminal domain is encoded by the three succeeding exons (IV, V, VI). The latter three exons correspond well in size and share sequence homology with three exons coding for 14-kDa S-type lectins. The sequence in exon I offers an explanation for the generation of two mRNAs differing only in their 5' untranslated sequences, previously reported in Mac-2 cDNA clones. Using cDNA synthesis and PCR amplification, we determined that two alternative splice sites are used in many different types of cells. This alternative splicing results in different 5' untranslated regions of the murine epsilon BP mRNA.
[Show abstract][Hide abstract] ABSTRACT: Invasion of basement membranes by cancer cells is a critical step in metastasis, which requires the coordinated expression of specific genes such as laminin receptors and metalloproteinases. Estradiol and progesterone modulate the clinical progression of steroid-sensitive breast cancers; however, little is known about the molecular regulation of the invasive phenotype by these hormones. We therefore examined the effects of 10 nM estradiol and/or 10 nM progestin R5020 on the expression of 2 non-integrin laminin binding proteins, the 67-kDa laminin receptor (67LR) and HLBP31 as well as the 72-kDa type-IV collagenase (MMP-2) and its inhibitor, TIMP-2, in steroid-receptor-positive (T47D and MCF-7) and -negative (MDA-MB 231) human breast-cancer cells. The relative steady-state level of 67LR mRNA was increased 2- to 3-fold by estradiol in both MCF-7 (p < 0.001) and T47D (p < 0.001) cells, also by R5020, alone or in combination with estradiol, in T47D cells (p < 0.001) and to a much less extent in MCF-7 cells. HLBP31 mRNA and protein levels were increased 2- to 3-fold (p < 0.001) by R5020 alone or in combination with estradiol, but not by estradiol alone. None of the steroid treatments affected the expression or activity of MMP-2. Interestingly, however, TIMP-2 mRNA levels and protein expression in MCF-7 and T47D cells were 50% down-regulated (p < 0.001) by treatment with R5020 or R5020 plus estradiol, but not by treatment with estradiol alone. None of these genes were modulated in steroid-independent MDA-MB231 cells. The data suggest that estradiol and progesterone might act as coordinators regulating specific genes in the steroid-sensitive breast-cancer cell, leading to the acquisition of the metastatic phenotype.
No preview · Article · Oct 1992 · International Journal of Cancer
[Show abstract][Hide abstract] ABSTRACT: A number of lactose-binding lectins have recently been identified in the rat and mouse intestine, one of which corresponds to the C-terminal domain of IgE-binding proteins, originally identified in rat basophilic leukemia (RBL) cells and mouse 3T3 fibroblasts. In the present report, we describe the affinity purification of a rat intestinal lactose-specific lectin which binds murine IgE antibodies. This binding most likely occurs via the immunoglobulin carbohydrate chains, as it is inhibited by lactose. This intestinal lectin molecule is also immunologically related to the previously described IgE-binding protein (epsilon BP) isolated from RBL cells, since it is recognized by antibodies raised against recombinant epsilon BP. This intestinal form of epsilon BP has a molecular mass of 17.5 kDa, which is much lower than that of its RBL cell analogue (31 kDa). The attachment of IgE to the mouse intestinal epithelium was demonstrated by immunohistochemistry, along with the presence of a corresponding mouse intestinal epsilon BP. The carbohydrate-dependent nature of this attachment was established by demonstrating that IgE binding to mouse epithelium was specifically abolished by lactose (4 mM) and by a blood-group-A-active tetrasaccharide (0.2 mM), but not by mannose (10 mM). Finally, the association of IgE with the mouse intestinal epithelium was prevented by competition with the purified IgE-binding lectin isolated from rat intestine. Although the physiological function of this intestinal protein is still unknown, the finding that IgE binds to a lectin in the intestinal epithelium pinpoints a possible novel mechanism for the regulation of IgE-mediated disorders, such as food allergy.
Preview · Article · Mar 1992 · European Journal of Biochemistry
[Show abstract][Hide abstract] ABSTRACT: 1. The role of platelet-activating factor (PAF) and peptidoleukotrienes as putative mediators of some of the vascular changes triggered by antigen was investigated in rats passively sensitized with monoclonal anti-DNP (2,4-dinitrophenyl) IgE. 2. Lethal anaphylaxis with respiratory distress, systemic hypotension, detachment of the intestinal mucosa, leukopenia and extravasation of protein-rich plasma was observed after antigen challenge of rats sensitized with partially purified monoclonal IgE at concentrations of 15 mg protein kg-1. 3. Analysis of the peritoneal fluid obtained after i.v. challenge with DNP-BSA (bovine serum albumin) showed the presence of significant amounts of PAF (101 +/- 8 pg/rat), whereas this mediator was undetectable in control animals. Leukotriene D4 was the predominant peptidoleukotriene that could be recovered after antigen challenge, and showed an extremely high concentration (92 +2- 15 ng/rat) as compared to PAF levels. 4. Extravasation of protein-rich plasma was observed shortly after challenge and reached a maximum at 30 min. Treatment of animals with i.v. PCA 4248 (1-2 mg kg-1) and WEB 2086 (1 mg kg-1), two chemically unrelated compounds which are antagonists of the PAF-receptor, produced a significant reduction of the extravasation of protein-rich plasma. 5. The same degree of protection could be afforded by MK-886, an inhibitor of leukotriene biosynthesis. Combined treatment with WEB 2086 and MK-886 provided greater inhibition of protein-rich plasma extravasation than either compound alone. PCA 4248 was also found to inhibit in a dose-dependent manner the systemic hypotension observed upon DNP-BSA challenge.6. These data indicate that the lipid mediators PAF and peptidoleukotrienes are major effectors of the vascular disturbances observed in rat passive IgE-mediated anaphylaxis.
Preview · Article · Feb 1992 · British Journal of Pharmacology
[Show abstract][Hide abstract] ABSTRACT: IgE-binding protein (epsilon BP) refers to a protein originally identified in rat basophilic leukemia cells by virtue of its affinity for IgE. It is now known to be a beta-galactoside-binding lectin equivalent to carbohydrate-binding protein 35 (CBP 35). More recently, its identity to Mac-2, a macrophage cell-surface protein, has been established. cDNA coding for human epsilon BP has been cloned from a human HeLa cell cDNA library and contains an open reading frame of 750 base pairs encoding a 250 amino acid protein. Like the rat and murine counterparts, the human epsilon BP amino acid sequence can be divided into two domains with the amino-terminal domain consisting of a highly conserved repetitive sequence (YPGXXXPGA) and the carboxyl-terminal domain containing sequences shared by other S-type lectins. The human epsilon BP sequence exhibits extensive homology to murine and rat epsilon BP with 84% and 82% identity, respectively. The homology is particularly striking in the carboxyl-terminal domain where 95% identity is found between human and murine sequences in a stretch of over 70 amino acids. A survey of epsilon BP mRNA expression from several lymphocyte cell lines revealed that the level of epsilon BP transcription may reflect a relationship between cell differentiation and epsilon BP expression. Finally, human epsilon BP was purified from several human cell lines and shown to possess lactose-binding characteristics and cross-species reactivity to murine IgE. Surprisingly, three different human myeloma IgE proteins did not show reactivity to human epsilon BP. However, after neuraminidase treatment of each human IgE, pronounced binding to epsilon BP was observed, thereby indicating that only specific IgE glycoforms can be recognized by epsilon BP.