Identification of a 14-kDa laminin binding protein (HLBP14) in human melanoma cells that is identical to the 14-kDa galactoside binding lectin

LacNAc modification in bone marrow stromal cells enhances resistance of myelodysplastic syndrome cells to chemotherapeutic drugs

Chemotherapeutic drugs are used routinely for treatment for myelodysplastic syndrome (MDS) patients but are ineffective in a substantial proportion of patients. Abnormal hematopoietic microenvironments, in addition to spontaneous characteristics of malignant clones, contribute to ineffective hematopoiesis. In our study, we found expression of enzyme β1,4-galactosyltransferase 1 (β4GalT1), which regulates N-acetyllactosamine (LacNAc) modification of proteins, is elevated in bone marrow stromal cells (BMSCs) of MDS patients, and also contributes to drug ineffectiveness through a protective effect on malignant cells. Our investigation of the underlying molecular mechanism revealed that β4GalT1-overexpressing BMSCs promoted MDS clone cells resistant to chemotherapeutic drugs and also showed enhanced secretion of cytokine CXCL1 through degradation of tumor protein p53. Chemotherapeutic drug tolerance of myeloid cells was inhibited by application of exogenous LacNAc disaccharide and blocking of CXCL1. Our findings clarify the functional role of β4GalT1-catalyzed LacNAc modification in BMSCs of MDS. Clinical alteration of this process is a potential new strategy that may substantially enhance effectiveness of therapies for MDS and other malignancies, by targeting a niche interaction.

Synthesis and biological evaluation of modified laminin peptide (N2S2-KDP) with enhanced affinity for neuronal growth and targeted molecular imaging (SPECT)

An analog of γ1 laminin (RDIAEIIKDI) decapeptide has been used to augment neuronal survival and regeneration after injuries, during aging and other CNS disorder. As a prime synthetic peptide, KDI, is responsible for the neurite outgrowth of human embryonic neurons. In this study, we have designed, modified a KDI derivative and synthesized by replacing isoleucine (I) with Pro (P) amino acid at C-terminal to enhance its potency towards neurite growth. -Cys-Gly-Cys (-CGC) N2S2 motif was also incorporated in the present design for peptide radiolabeling. The modified peptide showed a better binding with the desired 3T1M receptor for neurite growth. The peptide was synthesized using solid phase peptide synthesis and Fmoc-strategy with more than 80% yield. The receptor binding studies of 99mTc-N2S2-KDP in Neuro2A cell lines showed Kd value in 31 nM range and the complex showed appreciable brain uptake in mice. The results on human SH-SY5Y indicate that the unlabeled N2S2-KDP may perhaps be useful for neurite growth in neurodegenerative disorder.

The Transition of the 37-Kda Laminin Receptor (Rpsa) to Higher Molecular Weight Species: Sumoylation or Artifact?

The 37-kDa laminin receptor (37LRP or RPSA) is a remarkable, multifaceted protein that functions in processes ranging from matrix adhesion to ribosome biogenesis. Its ability to engage extracellular laminin is further thought to contribute to cellular migration and invasion. Most commonly associated with metastatic cancer, RPSA is also increasingly found to be important in other pathologies, including microbial infection, neurodegenerative disease and developmental malformations. Importantly, it is thought to have higher molecular weight forms, including a 67-kDa species (67LR), the expression of which is linked to strong laminin binding and metastatic behavior. The composition of these larger forms has remained elusive and controversial. Homo- and heterodimerization have been proposed as events capable of building the larger species from the monomeric 37-kDa precursor, but solid evidence is lacking. Here, we present data suggesting that higher molecular weight species require SUMOylation to form. We also comment on the difficulty of isolating larger RPSA species for unambiguous identification and demonstrate that cell lines stably expressing tagged RPSA for long periods of time fail to produce tagged higher molecular weight RPSA. It is possible that higher molecular weight species like 67LR are not derived from RPSA.

Transcription factor c-jun regulates β3Gn-T8 expression in gastric cancer cell line SGC-7901

Aberrant glycosylation, a common feature of malignant alteration, is partly due to changes in the expression of glycosyltransferases, including β1,3-N-acetyl-glucosaminyltrans-ferase 8 (β3Gn‑T8), which synthesizes poly-N-acetyllactosamine (poly-LacNAc) chains on β1,6 branched N‑glycans. Although the role of β3Gn‑T8 in tumors has been reported, the regulation of β3Gn‑T8 expression, however, is still poorly understood. In the present study, we used three online bioinformatic software tools to identify multiple c‑jun binding sites in the promoter of the β3Gn‑T8 gene. Using luciferase reporter assay, chromatin immunoprecipitation (ChIP) analysis, RT‑PCR and western blot analysis, we revealed that c‑jun could bind to and activate the β3Gn‑T8 promoter, thus upregulating β3Gn‑T8 expression. This was also confirmed by changes in β3Gn‑T8 activity as demonstrated by flow cytometry, immunofluorescence and lectin blot analysis using LEA lectin. Moreover, expression of glycoprotein HG‑CD147, the substrate of β3Gn‑T8, was also regulated by c‑jun. In addition, c‑jun and β3Gn‑T8 were more highly expressed in the gastric cancer tissues when compared to these levels in the adjacent non‑tumor gastric tissues, and β3Gn‑T8 expression was positively correlated with c‑jun expression. These results suggest that c‑jun plays a significant role in regulating the expression of β3Gn‑T8 in the SGC‑7901 cell line and may be involved in the development of malignancy via the activity of β3Gn‑T8.

Deciphering the complex three-way interaction between the non-integrin laminin receptor, galectin-3 and Neisseria meningitidis

The non-integrin laminin receptor (LAMR1/RPSA) and galectin-3 (Gal-3) are multi-functional host molecules with roles in diverse pathological processes, particularly of infectious or oncogenic origins. Using bimolecular fluorescence complementation and confocal imaging, we demonstrate that the two proteins homo- and heterodimerize, and that each isotype forms a distinct cell surface population. We present evidence that the 37 kDa form of LAMR1 (37LRP) is the precursor of the previously described 67 kDa laminin receptor (67LR), whereas the heterodimer represents an entity that is distinct from this molecule. Site-directed mutagenesis confirmed that the single cysteine (C(173)) of Gal-3 or lysine (K(166)) of LAMR1 are critical for heterodimerization. Recombinant Gal-3, expressed in normally Gal-3-deficient N2a cells, dimerized with endogenous LAMR1 and led to a significantly increased number of internalized bacteria (Neisseria meningitidis), confirming the role of Gal-3 in bacterial invasion. Contact-dependent cross-linking determined that, in common with LAMR1, Gal-3 binds the meningococcal secretin PilQ, in addition to the major pilin PilE. This study adds significant new mechanistic insights into the bacterial-host cell interaction by clarifying the nature, role and bacterial ligands of LAMR1 and Gal-3 isotypes during colonization.

Quantitative analysis of glycans, related genes, and proteins in two human bone marrow stromal cell lines using an integrated strategy

Altered expression of glycans is associated with cell-cell signal transduction and regulation of cell functions in the bone marrow micro-environment. Studies of this micro-environment often use two human bone marrow stromal cell lines, HS5 and HS27a, co-cultured with myeloid cells. We hypothesized that differential protein glycosylation between these two cell lines may contribute to functional differences in in vitro co-culture models. In this study, we applied an integrated strategy using genomic, proteomic, and functional glycomic techniques for global expression profiling of N-glycans and their related genes and enzymes in HS5 cells versus HS27a cells. HS5 cells had significantly enhanced levels of bisecting N-glycans (catalyzed by MGAT3 [β-1,4-mannosyl-glycoprotein 4-β-N-acetylglucosaminyltransferase]), whereas HS27a cells had enhanced levels of Galβ1,4GlcNAc (catalyzed by β4GalT1 [β4-galactosyltransferase I]). This integrated strategy provides useful information regarding the functional roles of glycans and their related glycogenes and glycosyltransferases in the bone marrow microenvironment, and a basis for future studies of crosstalk among stromal cells and myeloma cells in co-culture.

Looking into laminin receptor: critical discussion regarding the non-integrin 37/67-kDa laminin receptor/RPSA protein

The 37/67-kDa laminin receptor (LAMR/RPSA) was originally identified as a 67-kDa binding protein for laminin, an extracellular matrix glycoprotein that provides cellular adhesion to the basement membrane. LAMR has evolutionary origins, however, as a 37-kDa RPS2 family ribosomal component. Expressed in all domains of life, RPS2 proteins have been shown to have remarkably diverse physiological roles that vary across species. Contributing to laminin binding, ribosome biogenesis, cytoskeletal organization, and nuclear functions, this protein governs critical cellular processes including growth, survival, migration, protein synthesis, development, and differentiation. Unsurprisingly given its purview, LAMR has been associated with metastatic cancer, neurodegenerative disease and developmental abnormalities. Functioning in a receptor capacity, this protein also confers susceptibility to bacterial and viral infection. LAMR is clearly a molecule of consequence in human disease, directly mediating pathological events that make it a prime target for therapeutic interventions. Despite decades of research, there are still a large number of open questions regarding the cellular biology of LAMR, the nature of its ability to bind laminin, the function of its intrinsically disordered C-terminal region and its conversion from 37 to 67 kDa. This review attempts to convey an in-depth description of the complexity surrounding this multifaceted protein across functional, structural and pathological aspects.

Differentially expressed glycosylated patterns of α-1-antitrypsin as serum biomarkers for the diagnosis of lung cancer

Lung cancer is the most common malignancy worldwide. Thus, there is a critical need for diagnostic biomarkers with adequate sensitivity and specificity for lung cancer detection. Glycans in glycoproteins are significantly altered in cancer, and may serve as a tool for identifying potential diagnostic biomarkers. Recent studies have reported changes in α-1-antitrypsin (A1AT) glycosylation in lung cancer serum, tissue and cell lines. In this study, a lectin microarray was used to detect glycosylation changes in serum A1AT from patients with lung adenocarcinoma (ADC), squamous cell lung cancer, small-cell lung cancer (SCLC) and benign pulmonary diseases. Differentially expressed glycosylated patterns of A1AT were identified by lectin arrays and were confirmed by lectin-based enzyme-linked immunosorbent assay (ELISA). We found that galactosylated A1AT could distinguish non-small-cell lung cancer (NSCLC) from benign pulmonary diseases (AUC = 0.834); fucosylated A1AT showed exceptional capability in distinguishing ADC from benign diseases (AUC = 0.919) or other lung cancer subtypes (AUC = 0.844), and A1AT containing poly-LacNAc could detect SCLC from benign diseases (AUC = 0.905) or NSCLC (AUC = 0.707). The present study indicates that glycosylated patterns of A1AT may serve as potential biomarkers for detection of lung cancer. Further studies in larger sample sizes are necessary to validate the clinical utility of these markers.

Analysis of glycan-related genes expression and glycan profiles in mice with liver fibrosis

Protein glycosylation plays an important role in the pathogenesis and progression of various liver diseases. However, little is known about the precise alterations in protein glycosylation or the potential correlation between glycan-related genes expression and glycan profiles in liver fibrosis. The aim of the study was to investigate potential associations between glycan-related genes expression and glycan profiles to evaluate liver fibrosis in a mouse model. Analyses of glycan-related genes expression and glycan profiles were performed using oligonucleotide microarrays and lectin microarrays, respectively. Real-time PCR and Western blot were used to confirm any altered glycan-related genes expression levels and protein levels. Moreover, altered glycan patterns on the surface of hepatocytes were verified by lectin histochemistry. These results revealed that the mRNA levels of 10 glycan-related genes were significantly altered in fibrotic liver. Furthermore, we observed an increase in multivalent sialic acid, poly-LacNAc, sialyl-T-antigen, Fucoseα-1,3/6GlcNAc, and GalNAcα1-3Gal in fibrotic liver specimens, whereas GlcNAc oligomers was decreased in fibrotic liver. Our findings indicated that the synthetic pathway of "Tn antigen → T antigen (core-1) → sialyl-T antigen" was activated for O-glycan during the process of liver fibrosis.

Differential expression of immunomodulatory galectin-1 in peripheral leukocytes and adult tissues and its cytosolic organization in striated muscle

Galectin-1 (Gal-1) is important in immune function and muscle regeneration, but its expression and localization in adult tissues and primary leukocytes remain unclear. To address this, we generated a specific monoclonal antibody against Gal-1, termed alphahGal-1, and defined a sequential peptide epitope that it recognizes, which is preserved in human and porcine Gal-1, but not in murine Gal-1. Using alphahGal-1, we found that Gal-1 is expressed in a wide range of porcine tissues, including striated muscle, liver, lung, brain, kidney, spleen, and intestine. In most types of cells, Gal-1 exhibits diffuse cytosolic expression, but in cells within the splenic red pulp, Gal-1 showed both cytosolic and nuclear localization. Gal-1 was also expressed in arterial walls and exhibited prominent cytosolic and nuclear staining in cultured human endothelial cells. However, human peripheral leukocytes and promyelocytic HL60 cells lack detectable Gal-1 and also showed very low levels of Gal-1 mRNA. In striking contrast, Gal-1 exhibited an organized cytosolic staining pattern within striated muscle tissue of cardiac and skeletal muscle and colocalized with sarcomeric actin on I bands. These results provide insights into previously defined roles for Gal-1 in inflammation, immune regulation and muscle biology.

Increased expression of galectin-1 during the progression of cervical neoplasia

Galectin-1, a member of the beta-galactoside-binding family, is widely expressed in epithelial and immune cells. It is involved in several normal and pathologic processes, such as cancer progression, metastasis, and immunobiology. Galectin-1 was found to be overexpressed in various cancer cells and the corresponding benign tissue. Therefore, it has been described as a marker for tumor progression in some malignancies. In the current study, the expression of galectin-1 was examined in 80 formalin-fixed, paraffin-embedded cervical tissues: 20 benign cervical specimen, 20 low-grade squamous intraepithelial lesions (LGSIL), 20 high-grade squamous intraepithelial lesions (HGSIL), and 20 invasive squamous cell carcinomas (ISCC). Immunohistochemical analyses showed that the intensity of the galectin-1 expression on stromal cells next to the transformed cells increased according to the pathologic grade: benign cervical tissue < LGSIL < HGSIL < ISCC (P < 0.001). The epithelial cells were always negative for galectin-1. These results suggest that galectin-1 expression on stromal cells increases with the histopathologic grade of cervical tissues, and it can be concluded that this increase is associated with the progression of cervical neoplasia.

A novel beta1,3-N-acetylglucosaminyltransferase (beta3Gn-T8), which synthesizes poly-N-acetyllactosamine, is dramatically upregulated in colon cancer

A new member of the UDP-N-acetylglucosamine: beta-galactose beta1,3-N-acetylglucosaminyltransferase (beta3Gn-T) family having the beta3-glycosyltransferase motifs was identified using an in silico method. This novel beta3Gn-T was cloned from a human colon cancer cell line and named beta3Gn-T8 based on its position in a phylogenetic tree and enzymatic activity. Beta3Gn-T8 transfers GlcNAc to the non-reducing terminus of the Galbeta1-4GlcNAc of tetraantennary N-glycan in vitro. HCT15 cells transfected with beta3Gn-T8 cDNA showed an increase in reactivity to both LEA and PHA-L4 in a flow cytometric analysis. These results indicated that beta3Gn-T8 is involved in the biosynthesis of poly-N-acetyllactosamine chains on tetraantennary (beta1,6-branched) N-glycan. In most of the colorectal cancer tissues examined, the level of beta3Gn-T8 transcript was significantly higher than in normal tissue. Beta3Gn-T8 could be an enzyme involved in the synthesis of poly-N-acetyllactosamine on beta1-6 branched N-glycans in colon cancer.

Oligosaccharide specificity of galectins: a search by frontal affinity chromatography

Galectins are widely distributed sugar-binding proteins whose basic specificity for beta-galactosides is conserved by evolutionarily preserved carbohydrate-recognition domains (CRDs). Although they have long been believed to be involved in diverse biological phenomena critical for multicellular organisms, in only few a cases has it been proved that their in vivo functions are actually based on specific recognition of the complex carbohydrates expressed on cell surfaces. To obtain clues to understand the physiological roles of diverse members of the galectin family, detailed analysis of their sugar-binding specificity is necessary from a comparative viewpoint. For this purpose, we recently reinforced a conventional system for frontal affinity chromatography (FAC) [J. Chromatogr., B, Biomed. Sci. Appl. 771 (2002) 67-87]. By using this system, we quantitatively analyzed the interactions at 20 degrees C between 13 galectins including 16 CRDs originating from mammals, chick, nematode, sponge, and mushroom, with 41 pyridylaminated (PA) oligosaccharides. As a result, it was confirmed that galectins require three OH groups of N-acetyllactosamine, as had previously been denoted, i.e., 4-OH and 6-OH of Gal, and 3-OH of GlcNAc. As a matter of fact, no galectin could bind to glycolipid-type glycans (e.g., GM2, GA2, Gb3), complex-type N-glycans, of which both 6-OH groups are sialylated, nor Le-related antigens (e.g., Le(x), Le(a)). On the other hand, considerable diversity was observed for individual galectins in binding specificity in terms of (1) branching of N-glycans, (2) repeating of N-acetyllactosamine units, or (3) substitutions at 2-OH or 3-OH groups of nonreducing terminal Gal. Although most galectins showed moderately enhanced affinity for branched N-glycans or repeated N-acetyllactosamines, some of them had extremely enhanced affinity for either of these multivalent glycans. Some galectins also showed particular preference for alpha1-2Fuc-, alpha1-3Gal-, alpha1-3GalNAc-, or alpha2-3NeuAc-modified glycans. To summarize, galectins have evolved their sugar-binding specificity by enhancing affinity to either "branched", "repeated", or "substituted" glycans, while conserving their ability to recognize basic disaccharide units, Galbeta1-3/4GlcNAc. On these bases, they are considered to exert specialized functions in diverse biological phenomena, which may include formation of local cell-surface microdomains (raft) by sorting glycoconjugate members for each cell type.

Possible role of galectin-9 in cell aggregation and apoptosis of human melanoma cell lines and its clinical significance

Galectin-9 expression was examined in 6 human melanoma cell lines. Among them, MM-BP proliferated with colony formation, but MM-RU failed. RT-PCR analysis revealed evident expression of galectin-9 mRNA in MM-BP but not in MM-RU. MM-BP expressed galectin-9 protein both on the surface and in the cytoplasm, whereas MM-RU expressed it only weakly in the cytoplasm. Exogenous galectin-9 induced in vitro both cell aggregation and apoptosis of MM-RU proliferating without colony formation. Association of galectin-9 expression in melanoma cells with prognosis of the patients bearing melanocytic tumors was further examined. Galectin-9 protein was strongly and homogeneously expressed in melanocytic nevi, but down-regulated in melanoma cells especially in metastatic lesions. High galectin-9 expression was inversely correlated with the progression of this disease, suggesting that high galectin-9 expression in primary melanoma lesions links to a better prognosis.

Increased expression of galectin-1 in carcinoma-associated stroma predicts poor outcome in prostate carcinoma patients

Galectin-1, a member of the beta-galactoside-binding galectin family, is a pleiotropic dimeric protein participating in a variety of normal and pathological processes, including cancer progression. Modulation of the interactions with the basement membrane glycoprotein laminin and induction of apoptosis in activated T lymphocytes are well-known functions of this galectin. In this study, the expression of galectin-1 was examined in 148 human primary prostate carcinoma samples. Immunohistochemical staining of paraffin sections of prostate tissues revealed that galectin-1 was not detected in normal, PIN (prostatic intraepithelial neoplasia) or carcinoma cells, but accumulated in the stroma and associated fibroblasts. Galectin-1 expression was significantly increased in the tumour-associated stroma compared with the non-neoplastic gland-associated stroma in 21.3% of the cases (Mantel-Haenszel test, p=0.001; Wilcoxon signed rank test, p<0.0001). Increased galectin-1 expression in the cancer-associated stroma compared to the normal gland-associated stroma (p=0.03) was identified by multivariate analysis as a strong independent predictor of prostate-specific antigen (PSA) recurrence, just after the pathological stage (p<0.0001). The association between accumulation of galectin-1 in the stroma of the malignant tissue and aggressiveness of the tumour adds weight to the body of evidence that identifies a role for galectin-1 in the acquisition of the invasive phenotype. In addition to modulating cancer cell interactions with laminin, galectin-1 accumulated around the cancer cells may act as an immunological shield by inducing activated T-cell apoptosis. This exciting hypothesis warrants further investigation.

Endogenous galectins and effect of galectin hapten inhibitors on the differentiation of the chick mesonephros

Galectins are galactoside-binding lectins. In the mesonephros of the chick embryo, the 16-kDa galectin is abundant in the glomerular and tubular basement membranes where it colocalizes with fibronectin and laminin. To test whether galectin-glycoprotein interactions could play a role in mesonephric development, the effects of the galectin hapten inhibitors thiodigalactoside (TDG) and lactose on the differentiation of the cultured mesonephros were investigated. When compared to control saccharide-free or maltose-treated cultures, mesonephroi cultured in the presence of TDG and lactose exhibited defects in tissue organization. These included a distorted tubule shape, pseudo-stratification of the tubular epithelium, and detachment of glomerular podocytes from the basement membrane. The presence of molecular differentiation markers in the developing mesonephros was investigated. In vivo, expression of the epithelial-specific cell adhesion molecule E-cadherin is restricted to differentiated tubular epithelial cells, whereas the intermediate filament protein vimentin is present in mesonephrogenic mesenchyme and is undetectable in tubular epithelial cells. In mesonephroi cultured in the absence of sugars or in the presence of maltose, the expression pattern of these two marker molecules resembles that found in the mesonephros in vivo. In contrast, in the mesonephroi cultured in the presence of TDG and lactose, the epithelial tubular cells expressing E-cadherin also express vimentin. Re-expression of vimentin in the tubular epithelial cells could indicate a partial reversal to a mesenchymal phenotype. Results suggest that galectin-glycoprotein interactions in the basement membrane are important in the maintenance of the renal epithelial phenotype. Dev Dyn 1999;215:248-263.

Identification of a 21 kDa laminin-binding component of Candida albicans

Binding of Candida albicans strain JCM0239 to radiolabelled laminin was studied to identify possible receptors. When two forms of the organism were examined, laminin was found to bind to germinating blastoconidia. There was only weak binding to blastoconidia without germ tubes. Laminin-binding to germinating blastoconidia was inhibited by non-labelled laminin or fibrinogen but not by fibronectin, a fibronectin peptide (Gly-Arg-Gly-Asp-Ser), or a laminin peptide (Tyr-Ile-Gly-Ser-Arg). A cell extract from germinating blastoconidia was analyzed by using SDS-PAGE and Western blotting, and 125I-labelled laminin was shown to bind to a 21 kDa component.

The 67 kDa laminin receptor as a prognostic factor in human cancer

Different receptors for adhesion molecules, including the monomeric 67 kDa laminin receptor (67LR), are responsible for the interactions between tumor cells and components of the extracellular matrix that play an important role in tumor invasion and metastasis. Clinical data clearly demonstrate the importance of the 67LR in the progression of a wide variety of tumors, including breast, lung, ovary, and prostate carcinomas and lymphomas. Indeed, data on more than 4000 cases of different tumors from different organs studied by immunohistochemistry are all concordant with a role for the 67LR in invasiveness, metastasis, and even tumor growth. This receptor molecule appears to be unusual since the corresponding full-length gene encodes a 37 kDa precursor protein which, after acylation, dimerizes to generate the mature 67 kDa form. The primary function of the membrane receptor is to stabilize the binding of laminin to cell surface integrins, acting as an integrin-accessory molecule, although homology of the gene encoding the receptor precursor with other genes suggests additional functions. Studies conducted to define the structure, expression, and function of this laminin receptor represent a step toward developing therapeutic strategies that target this molecule. In particular, therapeutic approaches that downregulate expression of the receptor on tumor cells might lead to decreased tumor aggressiveness.

Binding of synthetic sulfated ligands by human splenic galectin 1, a beta-galactoside-binding lectin

The carbohydrate-binding site of galectin 1, a vertebrate beta-galactoside-binding lectin, has a pronounced specificity for the betaGal(1-->3)- and betaGal(1-->4)GlcNAc sequences. The binding inhibition study reported herein was carried out to determine whether sulfation of saccharides would influence their binding by galectin 1. The presence of 6'-OSO3- on LacNAc greatly reduces the inhibitory potency relative to LacNAc. 3'-OSO3-LacNAc, 3'-OSO3-Galbeta(1-->3)GlcNAc(beta)1-OBzl and 3-OSO3-Galbeta1-OMe are more potent inhibitors than the non-sulfated parent compounds. Surprisingly, 2'-OSO3-LacNAc showed over 40 fold less inhibitory potency relative to LacNAc. Ovarian carcinoma A121 cells were shown to synthesize sulfated macromolecules that bind to galectin 1. Modulation in vivo of saccharide sulfation may lead to modulation of galectin 1 interaction with glycoconjugates; hence, sulfation could play a role in modulating lectin functions.

Changes in the distribution pattern of galectin-1 and galectin-3 in human placenta correlates with the differentiation pathways of trophoblasts

Human placentation is a complex biological phenomenon that results from precisely regulated interactions between cells and the extracellular matrix. Galectin- 1 and galectin-3 belong to a newly defined family of galactose-binding lectins that can bind several glycoconjugates such as the basement membrane glycoprotein laminin, and are involved in many biological events including cell adhesion. In this study, the expression of these two galectins in first and third trimester normal human placenta was examined using single and double immunohistochemical staining and specific antibodies for galectins and cytokeratins. Galectin-3 was detected in all trophoblastic lineages including villous cytotrophoblasts and extravillous trophoblasts (trophoblastic cell columns, infiltrating trophoblasts, endovascular trophoblasts and placental bed giant cells). On the contrary, galectin-1 distribution was restricted to endometrium. A reduction of galectin-3 expression was observed from the villous trophoblasts to the trophoblastic cell columns. This pattern correlated with the switch from a proliferative to a migratory phenotype. Galectin-1 and galectin-3 were both detected in maternal decidual cells. Our data demonstrate a specific pattern of galectin-1 and galectin-3 expression in trophoblastic tissue, and suggest these lectins could contribute to cell-cell and cell matrix interactions of trophoblast during placentation.

Modular organization of carbohydrate recognition domains in animal lectins

In spite of the great diversity of animal lectins, a common characteristic is their ability to bind sugars by means of discrete, modular carbohydrate recognition domains, CRDs. Three different groups of animal lectins-galectins, P-type and C-type lectins- have different types of CRDs which they arrange in a number of combinations, in three dimensions, in order to increase the affinity for oligosaccharides associated with glycoconjugates. The necessity of combining multiple CRDs in a native lectin molecule in order to increase the affinity for multiple ligands is of great importance physiologically, since many of the carbohydrate structures associated with proteins exist in a variety of different conformations. Recent work has clarified the structural basis for carbohydrate recognition by some of these lectins.

The biochemistry of cancer dissemination

The progression of a tumor cell from one of benign delimited proliferation to invasive and metastatic growth is the major cause of poor clinical outcome of cancer patients. Recent research has revealed that this complex process requires many components for successful dissemination and growth of the tumor cell at secondary sites. These include angiogenesis, enhanced extracellular matrix degradation via tumor and host-secreted proteases, tumor cell migration, and modulation of tumor cell adhesion. Each individual component is multifaceted and is discussed within this review with respect to historical and recent findings. The identification of components and their interrelationship have yielded new therapeutic targets leading to the development of agents that may prove effective in the treatment of cancer and its metastatic progression.

Galectin-3 and laminin expression in neoplastic and non-neoplastic thyroid tissue

Galectin-3 is a 31 kD beta-galactoside-binding lectin which is expressed by several types of non-neoplastic and neoplastic cells and which may be involved in cell-extracellular matrix interactions. An immunohistochemical study has been made of the expression of galectin-3, as well as its ligand, laminin, in a spectrum of benign and malignant thyroid neoplasms and in some non-neoplastic conditions. Immunohistochemistry with anti-human recombinant galectin-3 antibody showed consistent, intense positivity in the neoplastic cells of 18 cases of papillary carcinoma and less intense staining in the five anaplastic carcinomas studied. In addition, two out of three poorly differentiated carcinomas, three out of six medullary carcinomas, and four out of eight follicular carcinomas had less intense or focal positivity. One case of Hürthle cell carcinoma showed scattered strongly positive cells. Eight follicular adenomas, three hyperplastic nodules, five nodular goitres, and normal thyroid tissue were negative. Galectin-3 mRNA expression was also evaluated in three of the papillary carcinomas, two follicular adenomas, and one hyperplastic nodule with matched normal tissue. Northern blot analysis demonstrated mRNA overexpression in the three cases of papillary carcinomas, whereas normal and benign tissues were negative. Laminin distribution in neoplastic and non-neoplastic tissue varied with architectural patterns but did not correlate with galectin-3 immunohistochemical expression. We conclude that expression of galectin-3 is limited to inflammatory foci in normal and benign thyroid tissue and is a phenotypic feature of malignant thyroid neoplasms, especially papillary carcinomas.

Expression of the 67-kD laminin receptor, galectin-1, and galectin-3 in advanced human uterine adenocarcinoma

Alterations of tumor cell interactions with laminin, a basement membrane glycoprotein, are consistent features of the invasive and metastatic phenotype. Qualitative and quantitative changes in the expression of cell surface laminin-binding proteins have been correlated with the ability of cancer cells to cross basement membranes during the metastatic cascade. Such phenotypic modifications are usually associated with poor prognosis. In this study, the authors examined the possibility that expression of three laminin-binding proteins, the 67-kD laminin receptor (67LR), galectin-1, and galectin-3, is altered in human endometrial cancer in a fashion similar to that reported in other carcinomas, such as breast, colon, and ovarian cancer. Twenty advanced uterine adenocarcinomas were analyzed for expression of these three molecules using immunoperoxidase staining and specific antibodies. The authors found a significant increase in the expression of the 67LR and galectin-1 in cancer cells compared with normal adjacent endometrium (P = .0004 and .0022, respectively). As observed in other carcinomas, a significant down-regulation of galectin-3 expression was found in endometrial cancer cells compared with normal mucosa (P = .02). In the galectin-3 positive tumors, galectin-3 was detected in the cytoplasm and/or nucleus of cancer cells. Interestingly, tumors in which galectin-3 was detected only in the cytoplasm were characterized by deeper invasion of the myometrium than lesions where galectin-3 was found both in nucleus and cytoplasm (P = .02). This study shows an alteration of nonintegrin laminin-binding protein expression in advanced human endometrial cancer. Further studies on larger populations should determine the prognostic value of the detection of these laminin-binding proteins in endometrial carcinoma. Inverse modulation of the 67LR and galectin-3 appears to be a phenotypical feature of invasive carcinoma.

Decreased expression of galectin-3 is associated with progression of human breast cancer

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.

An immunohistochemical study of the 32-kDa galectin (beta-galactoside-binding lectin) in the nematode Caenorhabditis elegans

The localization of the 32-kDa galectin (beta-galactoside-binding lectin) of the nematode Caenorhabditis elegans, which is the first lectin to be found in a nematode, was examined immunohistochemically using an anti-lectin antiserum. The lectin was found to be localized most abundantly in the adult cuticle and also in the terminal bulb of the pharynx. However, it was difficult to locate the galectin in larval animals, though immunochemical experiments suggested its presence. These results suggest that one of the fundamental roles of the galectin may be as a component of the durable outer barrier, as in the case of the morphogenesis of chick embryonic skin.

Expression of the monomeric 67-kd laminin-binding protein in human lymphomas as defined by MLuC5 monoclonal antibody and paraffin section immunohistochemistry

Interactions between cancer cells and laminin, a major component of basement membranes, are mediated through a large variety of cell surface proteins designated as laminin receptors. Among the above proteins, a 67-kd monomeric high affinity laminin receptor (67 LR) has long been suspected to be involved in tumor progression. In this study we wished to establish whether the 67 LR molecule is detectable on tumor cells of Hodgkin's disease (HD) and non-Hodgkin's lymphomas (NHLs), to define its pattern of expression, and to assess the potential utility of 67 LR in differentiating these pathological entities. Morphological and immunohistological studies were performed on 85 specimens of HD and a series of 334 NHL specimens, including anaplastic large cell (ALC) (CD30-positive) lymphomas (73 specimens). For immunohistochemical assessment of the 67 LR we used the monoclonal antibody (MoAb) MLuC5 directed against the 67-kd laminin receptor on paraffin-embedded sections. Reed-Sternberg cells reacted with MLuC5 MoAb in four of 85 (4.7%) HD specimens. Among the NHL specimens, a MLuC5-positive reaction was expressed in 3.3% of B-cell lymphomas. They all belonged to the high grade subtypes. On the other hand, a MLuC5-positive reaction was detected in none of the T-cell lymphomas tested. In contrast to the results obtained with the other NHLs, in 30.2% of ALC (CD30-positive) lymphoma specimens, tumor cells reacted with MLuC5 MoAb. MLuC5-expressing ALC (CD30-positive) lymphoma cells were of either T-cell (six of 17 specimens), B-cell (three of 25 specimens), or undetermined phenotype (10 of 31 specimens). Our investigation has shown that 67 LR as shown by MLuC5 MoAb is detectable only in neoplastic cells of a fraction of ALC (CD30-positive) lymphomas and small subsets of B-cell high grade NHLs and HD. The restricted expression of the 67 LR molecule to ALC (CD30-positive) lymphomas provides a potential tool for the phenotypic separation of this pathological entity from HD and other lymphomas. Whether the detection of the 67 LR expression in these lymphoma subsets may be related to the aggressiveness of the disease remains to be ascertained.

Expression of the endogenous 14-kDa beta-galactoside-binding lectin galectin in normal human skin

The localization of an endogenous 14-kDa beta-galactoside-binding lectin (galectin) and its pattern of gene expression were examined in normal human skin by light- and electron microscopy. Under the light microscope, immunostaining of 14-kDa galectin was observed in the cell membrane of cells in the basal and spinous layers of the epidermis. Galectin was also found in the Langerhans cells, as shown by double labeling using anti-14-kDa galectin and anti-CD1a antibodies. In the dermis, immunostaining for the 14-kDa galectin was positive in the extracellular matrix and fibroblasts. At the electron-microscopic level of resolution, galectin was located primarily along the plasma membrane of keratinocytes, and in both the cytoplasm and nucleus of Langerhans cells in the epidermis, whereas in the dermis it was detected in the extracellular matrix and in both the nucleus and cytoplasm of fibroblasts. The gene expression of 14-kDa galectin was visualized by the HRP-staining method following in situ hybridization techniques. The expression was detected in the cytoplasm of cells in the basal and spinous layers of the epidermis; whereas, in the dermis, it was detected in the cytoplasm of fibroblasts. Moreover, SDS-polyacrylamide gel electrophoresis and lectin-blot analysis revealed that this galectin bound to glycoproteins of approximately 17, 62, and 72 kDa in the epidermis and to those of 29, 54, and 220 kDa in the dermis. The present study indicates that 1) normal human skin produces the beta-galactoside-binding 14-kDa galectin, and 2) this galectin is located in both the epidermis, particularly in the keratinocytes and Langerhans cells, and in the dermis. These results suggest that galectin is important for cell-cell contact and/or adhesion in the epidermis and for cell-extracellular matrix interaction in the dermis.

Selective modulation of the interaction of alpha 7 beta 1 integrin with fibronectin and laminin by L-14 lectin during skeletal muscle differentiation

The alpha 7 beta 1 integrin was originally identified and isolated from differentiating skeletal muscle and shown to be a laminin-binding protein (Song et al. (1992) J. Cell Biol. 117, 643–657). Expression of the alpha 7 gene and protein are developmentally regulated during skeletal muscle differentiation and have been used to identify cells at distinct stages of the myogenic lineage (George-Weinstein et al. (1993) Dev. Biol. 156, 209–229). The lactoside-binding protein L-14 exists as a dimer and has been localized on a variety of cells, in association with extracellular matrix. During myogenesis in vitro, L-14 is synthesized within replicating myoblasts but it is not secreted until these cells commence terminal differentiation and fusion into multinucleate fibers (Cooper and Barondes, J. Cell Biol. (1990) 110, 1681–1691). Addition of purified L-14 to myogenic cells plated on laminin inhibits myoblast spreading and fusion, suggesting that the L-14 lectin regulates muscle cell interactions with the extracellular matrix that are germane to myogenic development (Cooper et al. (1991) J. Cell Biol. 115, 1437–1448). We demonstrate here, using affinity chromatography and immunoblots, that alpha 7 beta 1 also binds to fibronectin and to the L-14 lectin. L-14 binds to both laminin and to the alpha 7 beta 1 integrin, and it can effectively inhibit the association of laminin and this integrin. Modulation of alpha 7 beta 1 interaction with its ligands by L-14 is selective: L-14 does not bind to fibronectin, nor does it interfere with the binding of fibronectin to alpha 7 beta 1.(ABSTRACT TRUNCATED AT 250 WORDS)