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PubMed1999

Galectin-3 expression is induced in cirrhotic liver and hepatocellular carcinoma.

Galectins are a family of beta-galactoside-binding animal lectins. In particular, a widely studied member galectin-3, previously designated as epsilonBP, CBP35, Mac-2, L-29 and L-34, has been associated with assorted processes such as cell growth, tumor transformation and metastasis. Galectin-3 is expressed in various tissues and organs but is significantly absent in normal hepatocytes. However, evaluation of patient liver biopsies for galectin-3 expression resulted in the finding that hepatocellular carcinoma (HCC) frequently expressed significant levels of this lectin (76% immunohistochemically positive). Further investigation revealed that galectin-3 expression in HCC is independent of whether the patient had prior hepatitis B virus infection: 14 of 18 HCC cases from HBV- patients, and 5 of 7 cases from HBV patients demonstrated positive galectin-3 immunohistochemistry. However, co-transfection studies using a galectin-3 promoter construct and an HBV-X protein (HBV-X) expression vector demonstrated that galectin-3 expression can occur through transactivation of the lectin promoter by HBV-X. Based on presently known properties of this lectin, it is possible that deregulated expression of galectin-3 can result in tumor transformation and invasiveness, or confer propensity for tumor cell survival. In addition, galectin-3 was abundantly expressed in cirrhotic liver in peripheral distribution within regenerating nodules. Such galectin-3 expression in rapidly proliferating hepatocytes in cirrhotic liver may be a result of the high mitotic index. Alternatively, it is possible that proliferating cells expressing galectin-3 are in the process of being transformed, thus indicating an early neoplastic event.

Animals↗
PubMed2000

Alteration of the cytoplasmic/nuclear expression pattern of galectin-3 correlates with prostate carcinoma progression.

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.

Aged↗
PubMed2002

Effects of galectin-3 expression on growth and tumorigenicity of the prostate cancer cell line LNCaP.

BACKGROUND: Galectin-3 is a beta-galactoside-binding vertebrate lectin. In human prostate cancer, galectin-3 expression has been shown to decrease with progression of disease. In the present study, we further investigated the role of galectin-3 in this malignancy by examining the phenotype of galectin-3-transfected prostate cancer cells. METHODS: Stably transfected galectin-3-expressing cell lines were developed from the prostate cancer cell line LNCaP, which does not constitutively express this molecule. Transfected cells lines were analyzed for alterations in morphology and growth rates, and for ability to form tumors in nude mice. RESULTS: Morphologically, when compared to the parental LNCaP cells, the galectin-3 transfectants had broader, flatter cell bodies, shorter and less finely branched dendritic processes, and large nuclei with pronounced and often multiple nucleoli. The galectin-3 lines were found to proliferate at a slower rate in vitro than either the vector control-transfected lines or parental LNCaP. When injected subcutaneously in nude mice, four of six galectin-3 lines formed tumors at a slower rate than control lines. Twenty-four tumors that formed from the transfected cell lines were examined by immunohistochemistry for galectin-3 expression. Only one tumor was found to express galectin-3, suggesting that the transfected cells which formed tumors were those which successfully down-regulated galectin-3 expression. CONCLUSIONS: In contrast to an apparent stimulatory role in some tumor types, galectin-3 is an inhibitory molecule for prostate cancer.

Animals↗
PubMed1998

Localization of galectin-3 in normal and diseased pancreatic tissue.

CONCLUSION: Galectin-3 is expressed in both human and hamster pancreatic tumors and tumor cell lines and this expression is increased over normal. BACKGROUND: Galectin-3 is overexpressed in many gastrointestinal tumors. This study examined the expression of galectin-3 in human and hamster pancreatic tumors to determine if galectin-3 could be used as a marker for pancreatic cancer. METHODS: Membranes were prepared from human and hamster pancreatic tumor cell lines. Galectin-3 was visualized by immunoblot analysis of separated membrane proteins using the monoclonal antibody (MAb) M3/38. Paraffin-embedded sections from normal, pancreatitis, and cancerous human pancreatic tissue and normal, N-nitrosobis(2-oxopropyl)amine (BOP)-treated hyperplastic, and cancerous hamster pancreatic tissues were processed immunohistochemically for galectin-3 using the MAb M3/38. RESULTS: Galectin-3 was heavily expressed in cytoplasmic and nuclear regions of 50% of normal human pancreatic tissue. Expression of galectin-3 in ductal cells in chronic pancreatitis and cancerous pancreatic tissue was increased over normal and was more uniform (>95% cells/duct stained). Normal hamster pancreatic ducts showed weak or no expression of galectin-3. Hyperplastic pancreatic ductal cells from BOP-treated hamsters heavily expressed galectin-3 (60-95% cells/duct stained). Galectin-3 expression in ductal cells in cancerous pancreatic lesions was increased to >95%. Galectin-3 was also detected in the pancreatic nerves in all human tissue specimens tested.

Adolescent↗
PubMed2006

Immunohistochemical and in situ hybridization analysis of galectin-3, a beta-galactoside binding lectin, in the urinary system of adult mice.

Galectin is an animal lectin that has high affinity to beta-galactoside of glycoconjugates. In the present study, cellular expression of galectin subtypes in the urinary system of adult mice was examined by in situ hybridization and immunohistochemistry. The major subtype expressed in the murine urinary system was galectin-3, which was expressed continuously from the kidney to the distal end of the urethra. The renal cortex expressed galectin-3 more intensely than the medulla. Renal galectin-3 immunoreactivity was strongest in the cortical collecting ducts, where principal cells were the sole cellular source. All cell layers of the transitional epithelium from the renal pelvis to the urethra strongly expressed galectin-3 at the mRNA and protein levels. An electron microscopic study demonstrated diffuse cytoplasmic localization of galectin-3 in principal cells of the collecting ducts and in the bladder epithelial cells. Urethral galectin-3 expression at the pars spongiosa decreased in intensity near the external urethral orifice, where the predominant subtype of galectin was substituted by galectin-7. The muscular layer of the ureter and urinary bladder contained significant signals for galectin-1. Taken together, the observations indicate that the adult urinary system shows intense and selective expression of galectin-3 in epithelia of the uretic bud- and cloaca-derivatives.

Animals↗
PubMed2006

Unique sequence and expression profiles of rat galectins-5 and -9 as a result of species-specific gene divergence.

Presence of species-specific gene divergence in a protein family prompts to thoroughly study structural aspects and expression profiles of the products. We herein focus on two members of an adhesion/growth-regulatory group of endogenous lectins, i.e. galectins-5 and -9. After first ascertaining species specificity of occurrence of galectin-5, constituted by a short section of rat galectin-9's N-terminal part and its C-terminal carbohydrate recognition domain, by database mining, we next detected and defined sequence differences in the proximal promoter region between the two genes. The ensuing hypothesis for distinct expression profiles was tested first by RT-PCR and then by immunohistochemistry. For the latter purpose, we employed antibodies rigorously controlled for absence of cross-reactivity including assays with various other galectins and, if necessary, refined by chromatographic removal of bi- or oligospecific activities. Indeed, the galectins have non-identical expression profiles, qualitative differences, e.g. seen for galectin-5-positive bone marrow and erythrocytes or for hitherto unknown expression in cells of the theca folliculi and galectin-9-positive skin epidermis and esophageal epithelium. Lack of hepatocyte or renal cortex staining separates these two expression profiles in rat from localization of galectin-9 in mouse. Interspecies extrapolation in a case of a galectin involved in unique gene divergence may thus not be valid. The presented results on galectin-5 relative to galectin-9 intimate distinct functions especially in erythropoiesis and imply currently unknown mechanisms to compensate its absence from the galectin network in other mammals.

Amino Acid Sequence↗
PubMed2006

Purification and some properties of galectin-1 derived from water buffalo (Bubalus bubalis) brain.

An increasing number of galectins have been found in various animal species, the most abundant of which is galectin-1. The purpose of the present study was to purify and characterize galectin-1 from buffalo brain. We purified the galectin using a combination of ammonium sulphate fractionation and affinity chromatography and the homogeneity was determined by both native polyacrylamide gel electrophoresis (PAGE) and denaturing SDS-PAGE. The molecular weight of the galectin as determined by SDS-PAGE under reducing conditions and by gel filtration column under native conditions was 13.8 and 24.5 kDa, respectively, suggesting a dimeric form of galectin. The most potent inhibitor of the galectin activity was lactose, giving complete inhibition of hemagglutination at 0.8 mM. Galectin showed higher specificity towards human blood group A. Free thiol groups were estimated at a molar ratio of 2.9. The effects of alkylating reagents (iodoacetate and iodoacetamide) on saccharide binding of the galectin were studied. Both alkylating reagents significantly inactivated the activity of the galectin within 20 min. The temperature and pH stability of the galectin were determined. Our findings based on physico-chemical properties, carbohydrate and blood group specificities of the galectin may have future implications in biological and clinical applications.

ABO Blood-Group System↗
PubMed1998

Metastasis of human colon cancer is altered by modifying expression of the beta-galactoside-binding protein galectin 3.

BACKGROUND & AIMS: Galectin 3 is a beta-galactoside-binding protein whose expression has been correlated with advanced tumor stage in the colon, but direct evidence for a role in metastasis is lacking. The current study was designed to more directly establish the role of galectin 3 in colon cancer metastasis. METHODS: Galectin 3 levels were manipulated in human colon cancer cells using eukaryotic expression constructs designed to express the complete galectin 3 complementary DNA in either the sense or antisense orientation. Liver colonization was assessed in athymic mice after splenic-portal inoculation or after spontaneous metastasis during cecal growth. RESULTS: Introduction of galectin 3 antisense into metastatic colon cancer cells (LSLiM6, HM7) resulted in a significant reduction in galectin 3-specific messenger RNA and total and cell surface galectin 3 protein. Conversely, stable integration of galectin 3 in the sense orientation resulted in an increase in cellular and cell surface galectin 3 in cells of low metastatic potential (LS174T). Reduction in galectin 3 levels was associated with a marked decrease in liver colonization and spontaneous metastasis by LSLiM6 and HM7 cells, whereas up-regulation of galectin 3 resulted in increased metastasis by LS174T cells. CONCLUSIONS: This study provides direct evidence that galectin 3 plays an important role in colon cancer metastasis.

Adenocarcinoma↗
PubMed1997

Galectin-3 inhibits granulocyte-macrophage colony-stimulating factor (GM-CSF)-driven rat bone marrow cell proliferation and GM-CSF-induced gene transcription.

The expression of galectin-3 (formerly known as IgE-binding protein or Mac-2) in rat bone marrow (BM) was investigated by FACS, immunocytochemical and immunoblot analysis. The functional significance of rat recombinant galectin-3 on mouse recombinant granulocyte-macrophage colony-stimulating factor (GM-CSF)-driven proliferation of macrophage progenitors and gene transcription was further examined. Immunocytochemical analysis of in situ BM sections demonstrated galectin-3 in myelopoietic cells and surrounding stroma, whereas erythropoietic and lymphopoietic environments essentially lacked galectin-3 expression. FACS analysis demonstrated that incubation of freshly isolated BMC with lactose, a competing ligand for galectin-3 binding to glycoconjugates, decreased binding of antigalectin antibodies to cells primarily expressing the myeloid antigen recognized by mAb His-54. Similarly, lectin-mediated binding of exogenous galectin-3 to myeloid lineage cells was also demonstrated. Immunoblot analysis of BM eluates demonstrated galectin-3 both in the extracellular matrix and in a lactose elutable form, bound to the surface of BMC. [3H]Thymidine incorporation studies on BMC cultured in the presence of galectin-3 demonstrated suppression of GM-CSF-induced proliferation by galectin-3. In addition, differential display analysis of immediate early gene expression in BMC cultured in the presence of galectin-3 revealed a 76.2% inhibition of GM-CSF-induced gene transcription by galectin-3 assessed by the number of PCR-fragments generated. Our data suggest a role for galectin-3 in the organization of myelopoietic compartments in rat BM and regulation of the action of growth factors on myelopoietic precursor cells.

Animals↗
PubMed2002

Role of galectin-8 as a modulator of cell adhesion and cell growth.

Galectin-8 belongs to the family of tandem-repeat type galectins. It consists as several isoforms, each made of two domains of approximately 140 amino-acids, both having a carbohydrate recognition domain (CRD). These domains are joined by a 'link peptide' of variable length. The human galectin-8 gene covers 33 kbp of genomic DNA. It is localized on chromosome 1 (1q42.11) and contains 11 exons. The gene produces by alternative splicing 14 different transcripts, altogether encoding 6 proteins. Galectin-8, like other galectins, is a secreted protein. Upon secretion galectin-8 acts as a physiological modulator of cell adhesion. When immobilized, it functions as a matrix protein equipotent to fibronectin in promoting cell adhesion by ligation and clustering of a selective subset of cell surface integrin receptors. Complex formation between galectin-8 and integrins involves sugar-protein interactions and triggers integrin-mediated signaling cascades such as Tyr phosphorylation of FAK and paxillin. In contrast, when present in excess as a soluble ligand, galectin-8 (like fibronectin) forms a complex with integrins that negatively regulates cell adhesion. Such a mechanism allows local signals emitted by secreted galectin-8 to specify territories available for cell adhesion and migration. Due to its dual effects on the adhesive properties of cells and its association with fibronectin, galectin-8 might be considered as a novel type of a matricellular protein. Galectin-8 levels of expression positively correlate with certain human neoplasms, prostate cancer being the best example studied thus far. The overexpressed lectin might give these neoplasms some growth and metastasis related advantages due to its ability to modulate cell adhesion and cellular growth. Hence, galectin-8 may modulate cell-matrix interactions and regulate cellular functions in a variety of physiological and pathological conditions.

Animals↗
PubMed2004

Nucling mediates apoptosis by inhibiting expression of galectin-3 through interference with nuclear factor kappaB signalling.

Nucling is a novel apoptosis-associated molecule, which is involved with cytochrome c /Apaf-1/caspase-9 apoptosome induction following pro-apoptotic stress. In the present study, we show first that Nucling is able to interact with galectin-3. Galectin-3 is known to participate in many biological processes, including apoptotic cell death. Nucling was found to down-regulate the expression level of galectin-3 mRNA/protein. Nucling-deficient cells, in which galectin-3 expression is up-regulated, appeared to be resistant to some forms of pro-apoptotic stress as compared with wild-type cells. In addition, the preputial gland from Nucling-deficient mice expressed a significant level of galectin-3 and exhibited a high incidence of inflammatory lesions, indicating that Nucling plays a crucial role in the homoeostasis of this gland by interacting with the galectin-3 molecule and regulating the expression level of galectin-3. Up-regulation of galectin-3 was also observed in the heart, kidney, lung, testis and ovary of the Nucling-deficient mice. In order to confirm the functional interaction between Nucling and galectin-3, a well-documented candidate for the mediator of galectin-3 expression, NF-kappaB (nuclear factor kappaB), was investigated as well. Nucling was shown to interfere with NF-kappaB activation via the nuclear translocation process of NF-kappaB/p65, thus inhibiting the expression of galectin-3. Taken together, we propose that Nucling mediates apoptosis by interacting and inhibiting expression of galectin-3.

Animals↗
PubMed1998

Homophilic binding properties of galectin-3: involvement of the carbohydrate recognition domain.

Galectin-3, an animal lectin specific for beta-galactosides, is composed of three different domains. The N-terminal half of the molecule (N domain) consists of a short N-terminal segment followed by glycine-, proline-, and tyrosine-rich tandem repeats. The C-terminal domain (C domain) harbors the carbohydrate recognition domain homologous to other members of the galectin family of lectins. Galectin-3 aggregates in solution, and participation of the N domain of the molecule in this process has already been demonstrated. Using a solid-phase radioligand binding assay, which allows the direct analysis of galectin-3 self-association, here we provide evidence that the carbohydrate recognition domain of the lectin is involved in carbohydrate-dependent homophilic interactions: (a) Radiolabeled galectin-3 binds to immobilized galectin-3, and the addition of unlabeled galectin-3 in solution increases the rate of binding of radiolabeled lectin; (b) binding of radiolabeled galectin-3 to immobilized galectin-3 is inhibited by the C domain; (c) binding of radiolabeled galectin-3 to immobilized galectin-3 or the C domain is inhibited by lactose but not by sucrose; and (d) the radiolabeled C domain does not bind to immobilized C domain. Taken together, these data suggest that in addition to the N domain, the homophilic interactions of galectin-3 are mediated by the C domain.

Antigens, Differentiation↗
PubMed2001

Galectin-3 phosphorylation is required for its anti-apoptotic function and cell cycle arrest.

Galectin-3, a beta-galactoside-binding protein, is implicated in cell growth, adhesion, differentiation, and tumor progression by interactions with its ligands. Recent studies have revealed that galectin-3 suppresses apoptosis and anoikis that contribute to cell survival during metastatic cascades. Previously, it has been shown that human galectin-3 undergoes post-translational signaling modification of Ser(6) phosphorylation that acts as an "on/off" switch for its sugar-binding capability. We questioned whether galectin-3 phosphorylation is required for its anti-apoptotic function. Serine to alanine (S6A) and serine to glutamic acid (S6E) mutations were produced at the casein kinase I phosphorylation site in galectin-3. The cDNAs were transfected into a breast carcinoma cell line BT-549 that innately expresses no galectin-3. Metabolic labeling revealed that only wild type galectin-3 undergoes phosphorylation in vivo. Expression of Ser(6) mutants of galectin-3 failed to protect cells from cisplatin-induced cell death and poly(ADP-ribose) polymerase from degradation when compared with wild type galectin-3. The non-phosphorylated galectin-3 mutants failed to protect cells from anoikis with G(1) arrest when cells were cultured in suspension. In response to a loss of cell-substrate interactions, only cells expressing wild type galectin-3 down-regulated cyclin A expression and up-regulated cyclin D(1) and cyclin-dependent kinase inhibitors, i.e. p21(WAF1/CIP1) and p27(KIP1) expression levels. These results demonstrate that galectin-3 phosphorylation regulates its anti-apoptotic signaling activity.

Anoikis↗
PubMed2004

Peptides specific to the galectin-3 carbohydrate recognition domain inhibit metastasis-associated cancer cell adhesion.

Intravascular cancer cell adhesion plays a significant role in the metastatic process. Studies indicate that galectin-3, a member of the galectin family of soluble animal lectins, is involved in carbohydrate-mediated metastatic cell heterotypic (between carcinoma cells and endothelium) and homotypic (between carcinoma cells) adhesion via interactions with the tumor-specific Thomsen-Friedenreich glycoantigen (TFAg). We hypothesized that blocking the galectin-3 carbohydrate recognition domain with synthetic peptides would significantly reduce metastasis-associated carcinoma cell adhesion. To test this hypothesis, we identified peptide antagonists of the galectin-3 carbohydrate recognition domain using combinatorial bacteriophage display technology. The peptides bound with high affinity to purified recombinant galectin-3 protein (K(d) approximately 17-80 nM) and to cell surface galectin-3. Experiments with a series of recombinant serially truncated galectin-3 mutants indicated that the peptides bound the carbohydrate recognition domain of galectin-3. Furthermore, the peptides did not bind the carbohydrate recognition domain of other galectins and plant lectins. Synthetic galectin-3 carbohydrate recognition domain-specific peptides blocked the interaction between galectin-3 and TFAg and significantly inhibited rolling and stable heterotypic adhesion of human MDA-MB-435 breast carcinoma cells to endothelial cells under flow conditions, as well as homotypic tumor cell aggregation. These results demonstrate that carbohydrate-mediated, metastasis-associated tumor cell adhesion could be inhibited efficiently with short synthetic peptides which do not mimic naturally occurring glycoepitopes yet bind to the galectin-3 carbohydrate recognition domain with high affinity and specificity.

Antigens, Tumor-Associated, Carbohydrate↗
PubMed1996

Galectin-1 from bovine spleen: biochemical characterization, carbohydrate specificity and tissue-specific isoform profiles.

Selected biochemical properties, including the charge heterodispersity profile and carbohydrate specificity, of bovine galectin-1 were determined in detail. The lectin was purified through an improved purification protocol that yielded 35-40 mg/kg of wet tissue with a specific activity of 1.7-2 x 10(4) mg-1.ml. The galectin is a homodimer of approximately 14.5 kDa subunits with E(280)mg/ml of 0.65 ml.mg-1.cm-1. When stored in the presence of its carbohydrate ligand, the lectin's binding activity remained stable in a non-reducing environment even at room temperature. The optimal pH for binding to the ligand was 6.5-8.0. The overall carbohydrate specificity of the bovine galectin-1 isolated from spleen is similar to that of the galectin isolated from heart and to other mammalian galectins that exhibit "conserved" (Type I) carbohydrate recognition domains (CRDs) [Ahmed, H. and Vasta, G.R. (1994) Glycobiology 4, 545-549], but differs from those from Xenopus laevis and rat intestine domain I. The fluorescence of 4-methylumbelliferyl alpha-D-galactopyranoside was quenched on binding to bovine spleen galectin-1. Scatchard plots of data obtained at 5, 15, and 30 degrees C showed that the galectin has two sugar exothermic binding sites with association constants of 3.4 x 10(5), 1.0 x 10(5), and 0.3 x 10(5), respectively. Chemical modification studies indicated that histidine, tryptophan, carboxylic acid, and arginine, but not lysine or tyrosine, are involved in the binding to the carbohydrate ligand. On isoelectric focusing, the spleen galectin-1 appeared as six isoforms ranging from pI4.56-4.88 with main components at pI 4.63 (34.0%), 4.73 (42.6%), and 4.88 (16.6%). The galectin-1 isolated from heart yielded a quali- and quantitatively different profile with four isoforms ranging from pI 4.53-4.73, those with pIs of 4.56, 4.63, and 4.73 being common to the spleen homolog. Edman degradation of selected peptides purified from the spleen galectin-1 digest revealed amino acid sequences identical to those obtained for the heart galectin-1. This suggests that although point mutations in the subunit primary structure may not be the likely source of isolectins, as observed for X. laevis, tissue-specific co- or post-translational modifications may be the possible cause of the differences in the galectin isoform profile between bovine spleen and heart.

Amino Acid Sequence↗
PubMed2003

Galectin-1-mediated apoptosis in mycosis fungoides: the roles of CD7 and cell surface glycosylation.

Sezary cells, the malignant T cells in mycosis fungoides/Sezary syndrome, resist a variety of apoptosis-inducing agents, a feature that contributes to the poor response to therapy in mycosis fungoides. Galectin-1 is a mammalian lectin that triggers T cell apoptosis. For T cells to be susceptible to galectin-1-induced apoptosis, the T cells must express specific glycoprotein receptors, such as CD7, that bear the specific oligosaccharides recognized by galectin-1. Because Sezary cells are characteristically CD7(-), lack of CD7 expression has been proposed to render Sezary cells resistant to galectin-1-induced death. However, the role played by aberrant cell surface glycosylation in resistance of Sezary cells to galectin-1 has not been examined. In this study, we demonstrated abundant galectin-1 in mycosis fungoides skin lesions, indicating that Sezary cells are exposed to galectin-1 in vivo. To determine specific characteristics of Sezary cells that contribute to galectin-1 resistance, we assessed CD7 expression and cell surface glycosylation of Sezary cells in mycosis fungoides lesions and of four Sezary T cell lines. Sezary cells in primary lesions and Sezary T cell lines demonstrated a characteristic "glycotype" with sialylated core 1 O-glycans that promote galectin-1 resistance. Expression of CD7 was necessary but not sufficient for galectin-1-induced death of Sezary cell lines. In addition, CD7(-) Sezary cell lines, and Sezary cells within mycosis fungoides lesions, expressed galectin-1, whereas CD7-positive Sezary cell lines did not express galectin-1. We propose that both loss of CD7 expression and altered cellular glycosylation contribute to apoptosis resistance of malignant T cells in mycosis fungoides.

Antigens, CD7↗
PubMed2005

Immunohistochemical characterization of the distribution of galectin-4 in porcine small intestine.

Galectins are an evolutionarily conserved family of 15 different lectins found in various combinations in virtually every type of animal cell. One of the primary galectins expressed in intestinal epithelium is galectin-4, a tandem-repeat galectin with two carbohydrate-recognition domains in a single polypeptide chain. In the current study, we produced an anti-galectin-4 monoclonal antibody (MAb) for determining the distribution of galectin-4 in porcine small intestine to enhance our understanding of where galectin-4 performs its functions in the small intestine. In immunohistochemistry studies, this MAb detected galectin-4 primarily in the cytoplasm of absorptive epithelial cells lining intestinal villi. Mature epithelial cells at the villous tips stained the most intensely with this MAb, with progressively less intense staining observed along the sides of villi and into the crypts. In addition to its cytoplasmic localization, galectin-4 was also associated with nuclei in villous tip cells, indicating that some galectin-4 may migrate to the nucleus during terminal maturation of these cells. In intestinal crypts, a specific subset of cells, which may be enteroendocrine cells, expressed galectin-4 at a relatively high level. Galectin-4 distribution patterns were similar in all three regions (duodenum, jejunum, and ileum) of porcine small intestine.

Animals↗
PubMed2001

Expression of galectin-3-reactive ligands in squamous cancer and normal epithelial cells as a marker of differentiation.

The definition of biological markers for oropharynx and larynx cancer is essential to predict their clinical behavior. Since cellular glycans play an important role in biological information transfer, we have employed an endogenous lectin, galectin-3, to examine in primary squamous carcinomas, lymph node metastases, and physiological squamous epithelia whether glycans recognized by this lectin are altered in relation to the state of differentiation. The expression of galectin-3 was concomitantly evaluated by immunohistochemistry using the A1D6 monoclonal antibody. In addition, other antibodies were used for the detection of cytokeratins and desmosomal proteins (desmoplakin-1 and desmoglein). The results show the expression of galectin-3-reactive ligands in moderately/highly differentiated carcinomas only in areas exhibiting a high level of keratinization. Except for one patient out of 14, metastatic cells in lymph nodes expressed no accessible binding sites for galectin-3. No galectin-3-reactivity was detected in the basal cell layer of all studied normal epithelia (which contains the proliferating cells). The suprabasal layers were positive in epidermis and epithelium of tongue and cornea and negative in epithelium of palatine tonsil. The tumor cells expressed galectin-3 with an intensity positively correlated with tumor differentiation. The position of galectin-3-reactive sites colocalized with the two tested desmosomal proteins. However, presence of these proteins was also detected in areas of tumor and suprabasal layers of tonsil epithelium where no binding reactivity for galectin-3 was found. The present study showed that expression of galectin-3-reactive glycoligands is differentiation-dependent in normal as well as malignant squamous cells. Colocalization of galectin-3-reactive sites with desmosomal proteins (desmoplakin-1 and desmoglein) suggests an association of the galectin-3 ligand(s) with the cell surface, pointing to a potential participation of galectin-3 in mediation of intercellular contacts in these tumor types.

Antigens, Differentiation↗