We show that high-grade astrocytic tumors with high levels of galectin-1 expression are associated with dismal prognoses. The immunohistochemical analysis of galectin-1 expression of human U87 and U373 glioblastoma xenografts from the brains of nude mice revealed a higher level of galectin-1 expression in invasive areas rather than non-invasive areas of the xenografts. Nude mice intracranially grafted with U87 or U373 cells constitutively expressing low levels of galectin-1 (by stable transfection of an expression vector containing the antisense mRNA of galectin-1) had longer survival periods than those grafted with U87 or U373 cells expressing normal levels of galectin-1. Galectin-1 added to the culture media markedly and specifically increased cell motility levels in human neoplastic astrocytes. These effects are related to marked modifications in the organization of the actin cytoskeleton and the increase in small GTPase RhoA expression. All the data obtained indicate that galectin-1 enhances the migratory capabilities of tumor astrocytes and, therefore, their biological aggressiveness.
onitoring of gene-expression profiles is assumed to refine tumor characterization of laryngeal squamous cell carcinomas (LSCCs) with a therapeutic perspective. This is especially expected for adhesion/growth-regulatory effectors such as galectins, a class of endogenous lectins. Using computer-assisted microscopy, we investigated the prognostic value contributed by the quantitative determination of the immunohistochemical levels of expression of galectin-1, -3 and -7 in a series of 62 LSCCs including 42 low- and 20 high-stage LSCCs. As galectin-1 may have a key role leading to a tumor escape from immune surveillance, we also investigated whether or not the level of galectin-1 expression correlated with lymphocyte infiltration in LSCCs. The immunohistochemical determination of expression of galectin-1 is of prognostic value in human squamous laryngeal cancers. LSCCs that display high levels of galectin-1 have worse prognoses than laryngeal cancers with low levels of galectin-1 expression. Elevation of galectin-1 levels in laryngeal cancers can contribute to the process of tumor immune escape by killing the activated T-cells and other protumoral activities such as promoting motility or activity of oncogenic H-Ras proteins. The quantitative determination of galectin-1 in LSCCs is an independent prognostic marker when opposed to TNM staging. It has the potential to identify patients unlikely to benefit from T-cell-mediated immunotherapy, although the definitive effector function from its pro- and antitumoral activity profile has not been delineated.
Thorough analysis of the principles of molecular recognition is the basis for rational development of clinical applications. Currently, our knowledge is expanding, how biological information is encoded in a language of carbohydrate moieties, constituting the glycopart of cellular glycoconjugates. Carbohydrate-binding proteins like lectins can specifically bind these ligands. This glycobiological interplay participates in recognitive inter- and intracellular processes that enable to devise clinical schemes with rational perspective like targeted drug delivery, non-steroidal treatment of inflammation or lectin ligand-dependent treatment of infectious diseases. Besides the ligands, lectins, too, can be of therapeutical value, e.g. as biomodulators in the immune system. The rapid development within glycobiology allows to propose that certain aspects can well find their place in veterinary practice after proving their efficacy in clinical trials.
Nasal polyposis is a model for the study of inflammatory processes. We analyzed the expression of galectin-7, a growth regulator, in surface epithelium, glandular epithelium, and connective tissue in human nasal polyps, and examined the effect of the glucocorticoid budesonide on its expression in human nasal polyps ex vivo.Using quantitative, computer-assisted microscopy and immunohistochemistry, we measured galectin-7 expression in nine nasal polyps obtained by surgical resection. Five polyps came from allergic patients and four came from non-allergic patients.Galectin-7 was expressed in all three polyp tissues analyzed. Treatment of polyps from allergic and non-allergic patients with 50 ng/ml budesonide increased the extent of galectin-7 expression in the connective tissue (p = 0.01). Conversely, budesonide at this concentration did not apparently affect galectin-7 expression in glandular epithelium; only a slight decrease in the percentage of the galectin-7-immunopositive cells was observed. In the surface epithelium of nasal polyps from non-allergic patients, the percentage of galectin-7-immunopositive cells was decreased (p = 0.03) by treatment with 250 ng/ml budesonide. In nasal polyps from allergic patients, this percentage was increased by treatment with 50 ng/ml budesonide (p = 0.0001).These data are consistent with a role for galectin-7 in the regulation of cell growth through a pro-apoptotic effect. Galectin-7 expression coincides with the degree of epithelial stratification, and is subject to upregulation in the connective tissue in response to treatment with 50 ng/ml budesonide. Budesonide modulates galectin-7 expression differently in the surface epithelia of polyps from allergic and non-allergic patients.
Abstract Glycans and sugar‐binding molecules (lectins) form an interactive recognition system, which may enable parasitic organisms to adhere to host cells and migrate into target tissues. The aim of the present study was to analyse surface‐associated glycans in the developmental stages of Myxobolus cerebralis (Hofer), the causative agent of whirling disease. A panel of biotin‐labelled plant lectins was used to detect a broad spectrum of glycan motifs with high specificity. Binding sites were detected histochemically in the tissue sections of infected rainbow trout, Oncorhynchus mykiss (Walbaum), and infected Tubifex tubifex (Müller), and were characterized by light, fluorescence and transmission electron microscopy. With mannose‐specific lectins [ Lens culinaris agglutinin, Pisum sativum agglutinin, Canavalia ensiformis agglutinin (LCA, PSA, CanA)] mannose‐containing glycans were detected in all the developmental stages and host tissues. No binding sites for galactose‐specific lectins were present in M. cerebralis spores but reactivity with host tissues occurred. Diversity in glycans was detected by N ‐acetyl‐D‐galactosamine‐specific lectins in sporoplasm cells of M. cerebralis and triactinomyxon spores. In the group of lectins with monosaccharide‐specificity for N ‐acetyl‐D‐glucosamine (GlcNAc), the reactivity of Datura stramonium agglutinin (DSA), Lycopersicon esculentum agglutinin (LEA) and Solanum tuberosum agglutinin (STA) was restricted to polar capsules whereas Griffonia simplicifolia agglutinin II (GSA II) also bound to sporoplasm cells of stages in the fish host but not in those present in infected T. tubifex . Moreover, Triticum vulgaris (wheat germ) agglutinin (WGA) and succinylated WGA indicated the presence of N ‐acetyl‐D‐glucosamine polymers in polar capsules. No specificity for spores was observed concerning ‘bisected’ N ‐glycans and no reactivity in parasitic stages was observed with the fucose‐binding lectin Ulex europaeus agglutinin (UEA) I, Sambucus nigra agglutinin (SNA) (specific for α 2,6‐sialylated glycans) and Maackia amurensis agglutinin (MAAI) (specific for α 2,3‐sialylated glycans). Arachis hypogaea (peanut) agglutinin (PNA), Erythrina cristagalli agglutinin (ECA), GSA I, Sophora japonica agglutinin (SJA), Dolichos biflorus agglutinin (DBA) and GSA II detected reactive sites solely confined to the developmental stages of M. cerebralis and were not reactive in the fish host. These parasite‐specific glycans may play a role in the adhesion process of the parasite to fish epidermis prior to infection, but may provide protection to the host by activating the complement system, or stimulating an adaptive immune response as putative antigens.
Galectin-related protein (GRP) is present in vertebrates. Sequence comparisons between GRPs from diverse species reveal an unusually high degree of similarity indicative of a strong positive selection. In solution, human and chicken GRPs are monomers irrespective of the presence of the 36-amino-acid-long extension of the core structure at the N-terminus. They are devoid of ability to bind lactose due to severe deviations from the respective sequence signature. Crystallography disclosed distortion of the binding-site architecture that precludes accommodation of lactose. The recent characterization of expression of chicken GRP (C-GRP) enables complete galectin network analysis in this organism. When tested in a panel of developing and adult organs, C-GRP presence was detected in bursa of Fabricius. Its epithelium and vessels as well as bursal B cells are positive in immunohistochemistry. In the B lymphocytes, C-GRP was predominantly cytoplasmic, whereas the chicken tandem-repeat-type galectin, the second member of the galectin family expressed in these cells, was detected at the surface. Binding of labeled C-GRP to cells and sections was blocked by heparin. These data illustrate disparities in expression and ligand profiles within the galectin family and hereby stimulate interest to perform respective mapping for mammalian GRPs as step to define its physiological function(s).
