Galectin-1-mediated cell adhesion, invasion and cell death in human anaplastic large cell lymphoma: regulatory roles of cell surface glycans

Identification and characterization of emGalaseE, a β-1,4 galactosidase from Elizabethkingia meningoseptica, and its application on living cell surface

The biological function of terminal galactose on glycoprotein is an open field of research. Although progress had being made on enzymes that can remove the terminal galactose on glycoproteins, there is a lack of report on galactosidases that can work directly on living cells. In this study, a unique beta 1,4 galactosidase was isolated from Elizabethkingia meningoseptica (Em). It exhibited favorable stability at various temperatures (4-37 °C) and pH (5-8) levels and can remove β-1, 4 linked galactoses directly from glycoproteins. Using Alanine scanning, we found that two acidic residues (Glu-468, and Glu-531) in the predicted active pocket are critical for galactosidase activity. In addition, we also demonstrated that it could cleave galactose residues present on living cell surface. As this enzyme has a potential application for living cell glycan editing, we named it emGalaseE or glycan-editing galactosidase I (csgeGalaseI). In summary, our findings lay the groundwork for further investigation by presenting a simple and effective approach for the removal of galactose moieties from cell surface.

Cannabidiol and Cannabigerol Modify the Composition and Physicochemical Properties of Keratinocyte Membranes Exposed to UVA

The action of UVA radiation (both that derived from solar radiation and that used in the treatment of skin diseases) modifies the function and composition of keratinocyte membranes. Therefore, this study aimed to assess the effects of phytocannabinoids (CBD and CBG), used singly and in combination, on the contents of phospholipids, ceramides, lipid rafts and sialic acid in keratinocyte membranes exposed to UVA radiation, together with their structure and functionality. The phytocannabinoids, especially in combination (CBD+CBG), partially prevented increased levels of phosphatidylinositols and sialic acid from occurring and sphingomyelinase activity after the UVA exposure of keratinocytes. This was accompanied by a reduction in the formation of lipid rafts and malondialdehyde, which correlated with the parameters responsible for the integrity and functionality of the keratinocyte membrane (membrane fluidity and permeability and the activity of transmembrane transporters), compared to UVA-irradiated cells. This suggests that the simultaneous use of two phytocannabinoids may have a protective effect on healthy cells, without significantly reducing the therapeutic effect of UV radiation used to treat skin diseases such as psoriasis.

Thymosin α1 interacts with Galectin-1 modulating the β-galactosides affinity and inducing alteration in the biological activity

The study of mechanism of action of Thymosin alpha 1 (Tα1) and the basis of the pleiotropic effect in health and disease, is one of the main focus of our ongoing research. Tα1 is a thymic peptide that demonstrates a peculiar ability to restore homeostasis in different physiological and pathological conditions (i.e., infections, cancer, immunodeficiency, vaccination, and aging) acting as multitasking protein depending on the host state of inflammation or immune dysfunction. However, few are the information about mechanisms of action mediated by specific Tα1-target protein interaction that could explain its pleiotropic effect. We investigated the interaction of Tα1 with Galectin-1 (Gal-1), a protein belonging to an oligosaccharide binding protein family involved in a variety of biological and pathological processes, including immunoregulation, infections, cancer progression and aggressiveness. Using molecular and cellular methodological approaches, we demonstrated the interaction between these two proteins. Tα1 specifically inhibited the hemagglutination activity of Gal-1, the Gal-1 dependent in vitro formation of endothelial cell tubular structures, and the migration of cancer cells in wound healing assay. Physico-chemical methods revealed the details of the molecular interaction of Tα1 with Gal-1. Hence, the study allowed the identification of the not known until now specific interaction between Tα1 and Gal-1, and unraveled a novel mechanism of action of Tα1 that could support understanding of its pleiotropic activity.

Multivalent glycosystems for human lectins

Human lectins are involved in a wide variety of biological processes, both physiological and pathological, which have attracted the interest of the scientific community working in the glycoscience field. Multivalent glycosystems have been employed as useful tools to understand carbohydrate-lectin binding processes as well as for biomedical applications. The review shows the different scaffolds designed for a multivalent presentation of sugars and their corresponding binding studies to lectins and in some cases, their biological activities. We summarise this research by organizing based on lectin types to highlight the progression in this active field. The paper provides an overall picture of how these contributions have furnished relevant information on this topic to help in understanding and participate in these carbohydrate-lectin interactions.

Galectin-1 and Galectin-3 in B-Cell Precursor Acute Lymphoblastic Leukemia

Acute lymphoblastic leukemias arising from the malignant transformation of B-cell precursors (BCP-ALLs) are protected against chemotherapy by both intrinsic factors as well as by interactions with bone marrow stromal cells. Galectin-1 and Galectin-3 are lectins with overlapping specificity for binding polyLacNAc glycans. Both are expressed by bone marrow stromal cells and by hematopoietic cells but show different patterns of expression, with Galectin-3 dynamically regulated by extrinsic factors such as chemotherapy. In a comparison of Galectin-1 x Galectin-3 double null mutant to wild-type murine BCP-ALL cells, we found reduced migration, inhibition of proliferation, and increased sensitivity to drug treatment in the double knockout cells. Plant-derived carbohydrates GM-CT-01 and GR-MD-02 were used to inhibit extracellular Galectin-1/-3 binding to BCP-ALL cells in co-culture with stromal cells. Treatment with these compounds attenuated migration of the BCP-ALL cells to stromal cells and sensitized human BCP-ALL cells to vincristine and the targeted tyrosine kinase inhibitor nilotinib. Because N-glycan sialylation catalyzed by the enzyme ST6Gal1 can regulate Galectin cell-surface binding, we also compared the ability of BCP-ALL wild-type and ST6Gal1 knockdown cells to resist vincristine treatment when they were co-cultured with Galectin-1 or Galectin-3 knockout stromal cells. Consistent with previous results, stromal Galectin-3 was important for maintaining BCP-ALL fitness during chemotherapy exposure. In contrast, stromal Galectin-1 did not significantly contribute to drug resistance, and there was no clear effect of ST6Gal1-catalysed N-glycan sialylation. Taken together, our results indicate a complicated joint contribution of Galectin-1 and Galectin-3 to BCP-ALL survival, with different roles for endogenous and stromal produced Galectins. These data indicate it will be important to efficiently block both extracellular and intracellular Galectin-1 and Galectin-3 with the goal of reducing BCP-ALL persistence in the protective bone marrow niche during chemotherapy.

Galectin Family Members: Emerging Novel Targets for Lymphoma Therapy?

The galectin family of proteins has high affinity with β-galactoside-containing glycans. These proteins participate in cell growth and differentiation, cell adhesion, cell signal transduction, cell apoptosis, and other cellular activities. In recent years, a large number of studies have described the expression and correlation of galectins in different tumors. Each member of the family plays a vital role in tumor growth, progression, angiogenesis, adhesion, and tumor immune escape. Studies on the roles of galectins in lymphoma have mainly involved galectin-1, -3, -7, and -9. The results suggest that galectins may become novel targets for precise tumor treatment. This article reviews current research progress regarding galectins in lymphoma and provides new ideas for exploring them as novel targets for treating lymphoma and other important medical issues.

The Differential Effect of Cannabidiol on the Composition and Physicochemical Properties of Keratinocyte and Fibroblast Membranes from Psoriatic Patients and Healthy People

The development of psoriasis is accompanied by oxidative stress, which can modify the components of skin cells. Therefore, the aim of this study was to evaluate the effect of cannabidiol (CBD), an antioxidant and anti-inflammatory phytocannabinoid, on the composition and physicochemical properties of the membranes of healthy and psoriatic keratinocytes and fibroblasts exposed to ultraviolet A (UVA) and ultraviolet B (UVB) radiation. In psoriasis-altered cells, decreased levels of the main groups of phospholipids and increased levels of sialic acid and malondialdehyde (MDA), a lipid peroxidation product, as well as negative charge of cell membranes compared to non-diseased cells, were found. On the other hand, UVA/B radiation increased the levels of phospholipids and MDA in both groups of cells. Moreover, psoriatic cells were characterized by lower levels of sialic acid and negative charge of cell membranes, while non-diseased cells showed the opposite response. The CBD treatment intensified some of the changes (phospholipid content and membrane charge) caused by the radiation of psoriatic cells, while it prevented these changes in the cells of healthy people. The results of this study indicate that CBD can prevent structural and functional changes to the membranes of healthy skin cells during phototherapy for psoriasis.

Insights into the role of sialylation in cancer progression and metastasis

Upregulation of sialyltransferases—the enzymes responsible for the addition of sialic acid to growing glycoconjugate chains—and the resultant hypersialylation of up to 40–60% of tumour cell surfaces are established hallmarks of several cancers, including lung, breast, ovarian, pancreatic and prostate cancer. Hypersialylation promotes tumour metastasis by several routes, including enhancing immune evasion and tumour cell survival, and stimulating tumour invasion and migration. The critical role of enzymes that regulate sialic acid in tumour cell growth and metastasis points towards targeting sialylation as a potential new anti-metastatic cancer treatment strategy. Herein, we explore insights into the mechanisms by which hypersialylation plays a role in promoting metastasis, and explore the current state of sialyltransferase inhibitor development.

Modulation of glycosyltransferase ST6Gal-I in gastric cancer-derived organoids disrupts homeostatic epithelial cell turnover

Programmed cell death promotes homeostatic cell turnover in the epithelium but is dysregulated in cancer. The glycosyltransferase ST6Gal-I is known to block homeostatic apoptosis through α2,6-linked sialylation of the death receptor TNFR1 in many cell types. However, its role has not been investigated in gastric epithelial cells or gastric tumorigenesis. We determined that human gastric antral epithelium rarely expressed ST6Gal-I, but the number of ST6Gal-I-expressing epithelial cells increased significantly with advancing premalignancy leading to cancer. The mRNA expression levels of ST6GAL-I and SOX9 in human gastric epithelial cells correlated positively with one another through the premalignancy cascade, indicating that increased epithelial cell expression of ST6Gal-I is associated with premalignant progression. To determine the functional impact of increased ST6Gal-I, we generated human gastric antral organoids from epithelial stem cells and differentiated epithelial monolayers from gastric organoids. Gastric epithelial stem cells strongly expressed ST6Gal-I, suggesting a novel biomarker of stemness. In contrast, organoid-derived epithelial monolayers expressed markedly reduced ST6Gal-I and underwent TNF-induced, caspase-mediated apoptosis, consistent with homeostasis. Conversely, epithelial monolayers generated from gastric cancer stem cells retained high levels of ST6Gal-I and resisted TNF-induced apoptosis, supporting prolonged survival. Protection from TNF-induced apoptosis depended on ST6Gal-I overexpression, because forced ST6Gal-I overexpression in normal gastric stem cell-differentiated monolayers inhibited TNF-induced apoptosis, and cleavage of α2,6-linked sialic acids from gastric cancer organoid-derived monolayers restored susceptibility to TNF-induced apoptosis. These findings implicate up-regulated ST6Gal-I expression in blocking homeostatic epithelial cell apoptosis in gastric cancer pathogenesis, suggesting a mechanism for prolonged epithelioid tumor cell survival.

Glycosylation in lymphoma: Biology and glycotherapy

Research using mouse lymphoma cell lines has resulted in many reports of glycosylation being a key regulator for the distant metastasis of mouse lymphoma cells in animal models. In contrast, there are only a few reports of experiments examining human lymphoma cell metastasis. The glycosylation pattern in human lymphoma shows that loss of Phaseolus vulgaris leukoagglutinating lectin (L-PHA) reactive oligosaccharides, and sialylation of L-PHA reactive oligosaccharides, are closely associated with a worse prognosis for diffuse large B cell lymphoma (DLBCL) patients. Sialic acid is related to cell adhesion to the extracellular matrix and metastasis of HBL-8 Burkitt lymphoma cells in a severe combined immunodeficiency (SCID) mouse animal model. In HBL-8 clones, differential cell surface sialylation was due to different expression levels of UDP-GlcNAc 2-epimerase (GNE). Knockdown of beta-galactoside alpha-2,6-sialyltransferase (ST6Gal1) resulted in enhanced lymphoma cell adhesion to galectin-1 in anaplastic large cell lymphoma cell line, H-ALCL. A fluorinated sialic acid analogue was shown to be useful for inhibiting sialyltransferase and may provide a new glycoengineering strategy for desialylation, as well as inhibiting invasion and metastasis and inducing cell death in lymphoma cell lines. This paper discusses glycosylation and sialylation in human lymphoma, and several glycoengineering therapeutic strategies for lymphoma.

Recent approaches for directly profiling cell surface sialoform

Sialic acids (SAs) are nine-carbon monosaccharides existing at the terminal location of glycan structures on the cell surface and secreted glycoconjugates. The expression levels and linkages of SAs on cells and tissues, collectively known as sialoform, present the hallmark of the cells and tissues of different systems and conditions. Accordingly, detecting or profiling cell surface sialoforms is very critical for understanding the function of cell surface glycans and glycoconjugates and even the molecular mechanisms of their underlying biological processes. Further, it may provide therapeutic and diagnostic applications for different diseases. In the past decades, several kinds of SA-specific binding molecules have been developed for detecting and profiling specific sialoforms of cells and tissues; the experimental materials have expanded from frozen tissue to living cells; and the analytical technologies have advanced from histochemistry to fluorescent imaging, flow cytometry and microarrays. This review summarizes the recent bioaffinity approaches for directly detecting and profiling specific SAs or sialylglycans, and their modifications of different cells and tissues.

Helicobacter pylori induces intracellular galectin-8 aggregation around damaged lysosomes within gastric epithelial cells in a host O-glycan-dependent manner

Galectin-8, a beta-galactoside-binding lectin, is upregulated in the gastric tissues of rhesus macaques infected with Helicobacter pylori. In this study, we found that H. pylori infection triggers intracellular galectin-8 aggregation in human-derived AGS gastric epithelial cells, and that these aggregates colocalize with lysosomes. Notably, this aggregation is markedly reduced following the attenuation of host O-glycan processing. This indicates that H. pylori infection induces lysosomal damage, which in turn results in the accumulation of cytosolic galectin-8 around damaged lysosomes through the recognition of exposed vacuolar host O-glycans. H. pylori-induced galectin-8 aggregates also colocalize with autophagosomes, and galectin-8 ablation reduces the activation of autophagy by H. pylori. This suggests that galectin-8 aggregates may enhance autophagy activity in infected cells. We also observed that both autophagy and NDP52, an autophagy adapter, contribute to the augmentation of galectin-8 aggregation by H. pylori. Additionally, vacuolating cytotoxin A, a secreted H. pylori cytotoxin, may contribute to the increased galectin-8 aggregation and elevated autophagy response in infected cells. Collectively, these results suggest that H. pylori promotes intracellular galectin-8 aggregation, and that galectin-8 aggregation and autophagy may reciprocally regulate each other during infection.

Extracellular galectins as controllers of cytokines in hematological cancer

Galectins and cytokines are both secreted proteins whose levels are prognosis factors for several cancers. Extracellular galectins bind to the glycans decorating glycoproteins and are overproduced in most cancers. Accumulative evidence shows that galectins regulate cytokines during cancer progression. Although galectins alter cytokine function by binding to the glycans decorating cytokines or their receptors, cytokines could also regulate galectin expression and function. This review revises these complex interactions and their clinical impact, particularly in hematological cancers.

Increased Level of α2,6-Sialylated Glycans on HaCaT Cells Induced by Titanium Dioxide Nanoparticles under UV Radiation

As one of the most widely used nanomaterials, the safety of nano-TiO₂ for human beings has raised concern in recent years. Sialylation is an important glycosylation modification that plays a critical role in signal transduction, apoptosis, and tumor metastasis. The aim of this work was to investigate the cytotoxicity and phototoxicity of nano-TiO₂ with different crystalline phases for human skin keratinocytes (HaCaT cells) under ultraviolet (UV) irradiation and detect sialic acid alterations. The results showed that the mixture of crystalline P25 had the highest cytotoxicity and phototoxicity, followed by pure anatase A25, whereas pure rutile R25 had the lowest cytotoxicity and phototoxicity. A25 and R25 had no effects on the expression of sialic acids on HaCaT cells. However, HaCaT cells treated with P25 and UV showed an increased level of alterations in α2,6-linked sialic acids, which was related to the level of reactive oxygen species (ROS) generated by nano-TiO₂ and UV. The abundance of α2,6-linked sialic acids increased as ROS production increased, and vice versa. Antioxidant vitamin C (VC) reversed the abnormal expression of α2,6-linked sialic acids caused by nano-TiO₂ and protected cells by eliminating ROS. These findings indicate that nano-TiO₂ can alter the sialylation status of HaCaT cells under UV irradiation in a process mediated by ROS.

α2,6-Sialylation mediates hepatocellular carcinoma growth in vitro and in vivo by targeting the Wnt/β-catenin pathway

Abnormal sialylation due to overexpression of sialyltransferases has been associated with tumorigenesis and tumor progression. Although ST6Gal-I influences cancer persistence and progression by affecting various receptors, the underlying mechanisms and mediators remain largely obscure, especially in hepatocellular carcinoma (HCC). We found that ST6Gal-I expression was markedly upregulated in HCC tissues and cells, high levels being associated with aggressive phenotype and poor prognosis. Furthermore, we examined the roles and mechanisms of ST6Gal-I in HCC tumorigenesis and metastasis in vitro and in vivo. ST6Gal-I overexpression promoted proliferation, migration and invasion of Huh-7 cells, whereas its knockdown restricted these abilities in MHCC97-H cells. Additionally, in a mouse xenograft model, ST6Gal-I-knockdown MHCC97-H cells formed significantly smaller tumors, implying that ST6Gal-I overexpression can induce HCC cell malignant transformation. Importantly, enhanced HCC tumorigenesis and metastasis by ST6Gal-I may be associated with Wnt/β-catenin signaling promotion, including β-catenin nuclear transition and upregulation of downstream molecules. Together, our results suggest a role for ST6Gal-I in promoting the growth and invasion of HCC cells through the modulation of Wnt/β-catenin signaling molecules, and that ST6Gal-I might be a promising marker for prognosis and therapy of HCC.

Galectin-1 mediates TGF-β-induced transformation from normal fibroblasts into carcinoma-associated fibroblasts and promotes tumor progression in gastric cancer

Rcinoma-associated fibroblasts (CAFs) are a major constituent of the tumor microenvironment. Cancer cells can induce the transformation from normal fibroblasts (NFs) into CAFs, reciprocally, CAFs promote tumor invasion and proliferation. TGF-β has been the mostly accepted factor to fuel NFs transformation into CAFs. Galectin-1 (Gal1) is highly upregulated in CAFs of multiple human cancers, and overexpression of Gal1 in CAFs promotes tumor progression. The effect of Gal1 on TGF-β-induced CAFs activation has not yet been established in gastric cancer (GC). In this study, we show that Gal1 expression in stroma is positively related to TGF-β in epithelial cells by retrospective analysis of GC patient samples. Meanwhile, conditioned media (CMs) from gastric cancer cells induce expression of both Gal1 and the CAFs marker alpha smooth muscle actin (α-SMA) in NFs via TGF-β secretion. Knockdown of Gal1 prevents TGF-β-induced the conversion of NFs to CAFs. CMs from fibroblasts overexpressing Gal1 inhibits cancer cells apoptosis, promotes migration and invasion in vitro. Thus, Gal1 is significantly involved in the development of tumor-promoting microenvironment by enhancing TGF-β signaling in a positive feedback loop. Targeting Gal1 in tumor stroma should be considered as a potential therapeutic target for GC.

Clinical implication of the serum galectin-1 expression in epithelial ovarian cancer patients

Background

galectin-1 has been implicated in tumor invasion and metastasis and is frequently over-expressed in epithelial ovarian cancer (EOC), but its potential as a biomarker remains unclear. In this novel study, we have explored the possible use of galectin-1 as a biomarker for EOC.

Methods

galectin-1 in sera was evaluated by ELISA in a pilot panel of EOC patients, healthy volunteers, patients with benign gynecologic tumors or other gynecologic malignancies. We examined galectin-1 expression in EOC tumor samples by Western Blot, qRT-PCR and immunohistochemistry. In vitro experiments were conducted to elucidate the biologic role of galectin-1 in EOC progression using over-expression of galectin-1 in OVCAR-3 cells. We also looked for the association of galectin-1 expression with clinic pathological variables and survival outcomes in EOC.

Results

A significant difference was detected in serum galectin-1 between EOC patients with non-metastatic and those with metastatic disease, but not between EOC patients and healthy volunteers. It increased in recurrent cases and decreased after debulking surgery. Both of galectin-1 mRNA and protein levels were increased in 90 % of the examined EOC tissue samples, compared with a wedge resection of a normal ovary. High galectin-1 in peritumor stroma was primarily detected in advanced stages of EOC. Over expression of galectin-1 significantly increased the ability of OVCAR-3 cells’ migration and invasion.

Conclusions

Our results suggest that galectin-1 might play a role in tumor progression and be associated with poor outcome in EOC. It could be a novel prognostic and progression biomarker in EOC patients.

Sialylation and glycosylation modulate cell adhesion and invasion to extracellular matrix in human malignant lymphoma: Dependency on integrin and the Rho GTPase family

To determine the biological roles of cell surface glycosylation, we modified the surface glycosylation of human malignant lymphoma cell lines using glycosylation inhibitors. The O-glycosylation inhibitor, benzyl-α-GalNAc (BZ) enhanced the fibronectin adhesion of HBL-8 cells, a human Burkitt's lymphoma cell line, and of H-ALCL cells, a human anaplastic large cell lymphoma cell line, both of which were established in our laboratory. The N-glycosylation inhibitor, tunicamycin (TM) inhibited the surface expression of Phaseolus vulgaris leukoagglutinating (L-PHA) lectin- and Canavalia ensiformis (ConA) lectin-reactive oligosaccharides in the HBL-8 cell line. Assay of the adhesion of HBL-8 cells to fibronectin showed that fibronectin adhesion is mediated by the integrin very late antigen (VLA)-4 and that not only BZ but also TM treatment enhanced HBL-8 cell adhesion to fibronectin. Furthermore, although BZ treatment also enhanced H-ALCL cell adhesion to fibronectin, this effect was not mediated by VLA-5 or the RGD sequence of fibronectin. We also showed that H-ALCL cell adhesion to galectin-3 was enhanced by pre-treatment with neuraminidase, which cleaves cell surface sialic acid. Additionally, H-ALCL cell adhesion to galectin-3 was inhibited by pre‑treatment with the RGD peptide suggesting that cell adhesion to galectin-3 is mediated by integrin (VLA-5). Furthermore, H-ALCL cell invasion of galectin-1 and galectin-3 was inhibited by pre-treatment with the RGD peptide. Therefore, cell adhesion to and invasion of galectin-1 and galectin-3 are integrin-dependent. In addition to these findings, cell adhesion to galectin-3 was markedly inhibited by treatment with β-lactose compared to treatment with sucrose. Therefore, interactions between integrins and galectin-3 may be mediated through β-galactose that is linked to glycans of integrins. AZA1, an inhibitor of Ras homolog oncoprotein (Rho) GTPase family proteins, RAS-related C3 botulinus toxin substrate 1 (Rac 1) and Cell division control protein 42 homolog (Cdc42) markedly inhibited cell invasion of galectin-1 and galectin-3 suggesting that Rac 1 and Cdc42 may be involved in the regulation of H-ALCL cell invasion of galectins. In conclusion, artificial modification of cell surface glycosylation revealed the biological roles of glycosylation in the adhesion to and invasion of the extracellular matrix (ECM) by human malignant lymphoma cell lines. These findings will provide new insight into the glycobiology of human malignant lymphoma.

Glycosylation of solute carriers: mechanisms and functional consequences

Solute carriers (SLCs) are one of the largest groups of multi-spanning membrane proteins in mammals and include ubiquitously expressed proteins as well as proteins with highly restricted tissue expression. A vast number of studies have addressed the function and organization of SLCs as well as their posttranslational regulation, but only relatively little is known about the role of SLC glycosylation. Glycosylation is one of the most abundant posttranslational modifications of animal proteins and through recent advances in our understanding of protein-glycan interactions, the functional roles of SLC glycosylation are slowly emerging. The purpose of this review is to provide a concise overview of the aspects of glycobiology most relevant to SLCs, to discuss the roles of glycosylation in the regulation and function of SLCs, and to outline the major open questions in this field, which can now be addressed given major technical advances in this and related fields of study in recent years.

Glycodendrimers: tools to explore multivalent galectin-1 interactions

Four generations of lactose-functionalized polyamidoamine (PAMAM) were employed to further the understanding of multivalent galectin-1 mediated interactions. Dynamic light scattering and fluorescence microscopy were used to study the multivalent interaction of galectin-1 with the glycodendrimers in solution, and glycodendrimers were observed to organize galectin-1 into nanoparticles. In the presence of a large excess of galectin-1, glycodendrimers nucleated galectin-1 into nanoparticles that were remarkably homologous in size (400-500 nm). To understand augmentation of oncologic cellular aggregation by galectin-1, glycodendrimers were used in cell-based assays with human prostate carcinoma cells (DU145). The results revealed that glycodendrimers provided competitive binding sites for galectin-1, which diverted galectin-1 from its typical function in cellular aggregation of DU145 cells.

Sialylation by β-galactoside α-2,6-sialyltransferase and N-glycans regulate cell adhesion and invasion in human anaplastic large cell lymphoma

The interaction between cell surface glycans and extracellular matrix (ECM) including galectins is known to be closely associated with tumor cell adhesion, invasion and metastasis. We analyzed the roles of cell surface sialylation or glycosylation in galectin or ECM-mediated cell adhesion and invasion of human malignant lymphoma cells. Neuraminidase from Arthrobacter ureafaciens (AU) treatment resulted in reduction of cell adhesion to galectin-8 in human anaplastic large cell lymphoma (H-ALCL) which was established in our laboratory. The knockdown of β-galactoside α-2,6-sialyltransferase (ST6Gal1) by siRNA showed inhibition of ST6Gal1 expression in the cytoplasm of H-ALCL cells on immunohistochemical findings, and showed dramatic enhancement of cell adhesion to galectin-8. On the other hand, α-2,3-specific neuraminidase treatment resulted in moderate enhancement of cell adhesion to galectin-8. We performed chemically artificial modification of cell surface O-glycans by treatment of benzyl 2-acetamido-2-deoxy-α-D-galactopyranoside (Bz-α-GalNAc) in H-ALCL. Cell adhesion to galectin-8 was enhanced by treatment of Bz-α-GalNAc suggesting that inhibition of elongation of O-glycans may enhance cell adhesion to galectin-8 in H-ALCL cells. On the other hand inhibition of elongation of N-glycosylation by tunicamycin (TM) resulted in inhibition of Phaseolus vulgaris-L (L-PHA) lectin-binding activity and inhibited cell adhesion to galectin-8,laminin and fibronectin. Neuraminidase treatment enhanced cell adhesion to laminin, and knockdown of ST6Gal1 resulted in enhancement of cell adhesion to laminin, but not to fibronectin, collagen type 1 and 4. Galectin-8 pre-treatment dramatically enhanced cell adhesion to laminin and neuraminidase treatment also enhanced cell adhesion to laminin in combination with galectin-8. Rho inhibitor, C3-transferase pre-treatment resulted in inhibition of cell invasion to galectin-8. Phosphatidylinositol 3-phosphate kinase (PI3K) inhibitor, wortmannin inhibits the cell invasive capacity to galectin-8. Neuraminidase treatment induces growth inhibition of lymphoma cells by galectin-8.

Galectins as therapeutic targets for hematological malignancies: a hopeful sweetness

Galectins are family of galactose-binding proteins known to play critical roles in inflammation and neoplastic progression. Galectins facilitate the growth and survival of neoplastic cells by regulating their cross-talk with the extracellular microenvironment and hampering anti-neoplastic immunity. Here, we review the role of galectins in the biology of hematological malignancies and their promise as potential therapeutic agents in these diseases.