Galectins in the tumor endothelium: opportunities for combined cancer therapy

Galectin-8 inhibition and functions in immune response and tumor biology

Galectins are among organisms' most abundantly expressed lectins (carbohydrate-binding proteins) that specifically bind β-galactosides. They act not only outside the cell, where they bind to extracellular matrix glycans, but also inside the cell, where they have a significant impact on signaling pathways. Galectin-8 is a galectin family protein encoded by the LGALS8 gene. Its role is evident in both T- and B-cell immunity and in the innate immune response, where it acts directly on dendritic cells and induces some pro-inflammatory cytokines. Galectin-8 also plays an important role in the defense against bacterial and viral infections. It is known to promote antibacterial autophagy by recognizing and binding glycans present on the vacuolar membrane, thus acting as a danger receptor. The most important role of galectin-8 is the regulation of cancer growth, metastasis, tumor progression, and tumor cell survival. Importantly, the expression of galectins is typically higher in tumor tissues than in noncancerous tissues. In this review article, we focus on galectin-8 and its function in immune response, microbial infections, and cancer. Given all of these functions of galectin-8, we emphasize the importance of developing new and selective galectin-8 inhibitors and report the current status of their development.

Poly (I:C) increases the expression of galectin 1, 3, 9 and HGF genes in exosomes isolated from human Wharton's jelly mesenchymal stem cells

Background

Mesenchymal stem cells (MSCs) are commonly employed as a powerful tool for the treatment of immune-mediated problems owing to their capacity to regulate the immune system and differentiate into different tissues. Researchers use mesenchymal stem cell products given the limitations associated with the application of MSCs. Exosomes are nanometer vesicles derived from MSCs that are used in cell-free therapy. Inflammatory environmental conditions, such as stimulation of Toll-like receptor 3 (TLR-3), has the ability to adjust the immune-regulating properties and anti-inflammatory function of mesenchymal stem cells and their exosomes. Galectins and hepatocyte growth factor (HGF) are known as immunomodulatory factors in mesenchymal stem cells. This study was designed to examine the expression of galectin-1, galectin-3, galectin-9, and HGF genes in exosomes isolated from human Wharton's jelly mesenchymal stem cells (hWJ-MSCs) after stimulation with Poly (I:C) (Polyinosinic:polycytidylic acid sodium salt).

Methods

To begin, the explant technique was used to extract mesenchymal stem cells from human umbilical cord Wharton's jelly. Then, the stem cells were stimulated using Poly (I:C) at three time intervals of 12, 24 and 48 h. Exosomes secreted from the supernatant of cells were extracted and exosome confirmation tests, including Scanning electron microscopy (SEM), Dynamic light scattering (DLS) and Flow cytometry were performed. Finally, the expression of galectin-1, galectin-3, galectin-9, and HGF genes in exosomes was evaluated by Real-Time PCR at three time intervals of 12, 24 and 48 h after stimulation.

Results

The findings of our study indicated that following stimulation with Poly (I:C), the expression of galectin-9 and HGF (P < 0.05) genes was markedly higher than in the control group after 12 h. After 24 h, the expression of galectin-9 (P < 0.01), galectin-3 and HGF (P < 0.05) increased; the expression of galectin-1, galectin-3, (P < 0.05), galectin-9 and HGF genes (p < 0.01) significantly increased compared to the control group after 48 h.

Conclusion

TLR3 stimulation can increase the expression of galectins and HGF genes in exosomes derived from hWJ-MSCs and may be improve the immunosuppressive abilities of exosomes.

Vascular galectins in tumor angiogenesis and cancer immunity

Sustained tumor angiogenesis, i.e., the induction and maintenance of blood vessel growth by tumor cells, is one of the hallmarks of cancer. The vascularization of malignant tissues not only facilitates tumor growth and metastasis, but also contributes to immune evasion. Important players in all these processes are the endothelial cells which line the luminal side of blood vessel. In the tumor vasculature, these cells are actively involved in angiogenesis as well in the hampered recruitment of immune cells. This is the result of the abnormal tumor microenvironment which triggers both angiostimulatory and immune inhibitory gene expression profiles in endothelial cells. In recent years, it has become evident that galectins constitute a protein family that is expressed in the tumor endothelium. Moreover, several members of this glycan-binding protein family have been found to facilitate tumor angiogenesis and stimulate immune suppression. All this has identified galectins as potential therapeutic targets to simultaneously hamper tumor angiogenesis and alleviate immune suppression. The current review provides a brief introduction in the human galectin protein family. The current knowledge regarding the expression and regulation of galectins in endothelial cells is summarized. Furthermore, an overview of the role that endothelial galectins play in tumor angiogenesis and tumor immunomodulation is provided. Finally, some outstanding questions are discussed that should be addressed by future research efforts. This will help to fully understand the contribution of endothelial galectins to tumor progression and to exploit endothelial galectins for cancer therapy.

Isomerization of proline-46 in the N-terminal tail of galectin-3 enhances T cell apoptosis via the ROS-ERK pathway

Galectin-3 (Gal-3) is unique in the galectin family, due to the presence of a long N-terminal tail (NT) arising from its conserved carbohydrate recognition domain (CRD). Although functional significance of the NT has remained elusive, our previous studies demonstrated the importance of NT prolines to Gal-3 function. Here, we show that during the time Gal-3 stands in solution for three or more days, Gal-3 NT undergoes a slow, intra-molecular, time-dependent conformational/dynamical change associated with proline cis-trans isomerization. From initial dissolution of Gal-3 in buffer to three days in solution, Gal-3-mediated T cell apoptosis is enhanced from 23 % to 37 %. Western blotting and flow cytometry show that the enhancement occurs via the ROS-ERK pathway, and not by the PKC-ERK pathway. To assess which proline(s) is (are) responsible for this effect, we individually mutated all 14 NT prolines within the first 68 residues to alanines, and assessed their effect on ROS production. Our study shows that isomerization of P46 alone is responsible for the upregulation of ROS and T cell apoptosis. NMR studies show that this unique effect is mediated by a change in dynamic interactions between the NT and CRD F-face, which in turn leads to this change in Gal-3 function.

Galectin-1 in Pancreatic Ductal Adenocarcinoma: Bridging Tumor Biology, Immune Evasion, and Therapeutic Opportunities

Pancreatic Ductal Adenocarcinoma (PDAC) remains one of the most challenging malignancies to treat, with a complex interplay of molecular pathways contributing to its aggressive nature. Galectin-1 (Gal-1), a member of the galectin family, has emerged as a pivotal player in the PDAC microenvironment, influencing various aspects from tumor growth and angiogenesis to immune modulation. This review provides a comprehensive overview of the multifaceted role of Galectin-1 in PDAC. We delve into its contributions to tumor stroma remodeling, angiogenesis, metabolic reprogramming, and potential implications for therapeutic interventions. The challenges associated with targeting Gal-1 are discussed, given its pleiotropic functions and complexities in different cellular conditions. Additionally, the promising prospects of Gal-1 inhibition, including the utilization of nanotechnology and theranostics, are highlighted. By integrating recent findings and shedding light on the intricacies of Gal-1's involvement in PDAC, this review aims to provide insights that could guide future research and therapeutic strategies.

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.

Unraveling the pathophysiologic role of galectin-3 in chronically injured liver

Galectin-3 (Gal-3) previously referred to as S-type lectins, is a soluble protein that specifically binds to β-galactoside carbohydrates with high specificity. Gal-3 plays a pivotal role in a variety of pathophysiological processes such as cell proliferation, inflammation, differentiation, angiogenesis, transformation and apoptosis, pre-mRNA splicing, metabolic syndromes, fibrosis, and host defense. The role of Gal-3 has also been implicated in liver diseases. Gal-3 is activated upon a hepatotoxic insult to the liver and its level has been shown to be upregulated in fatty liver diseases, inflammation, nonalcoholic steatohepatitis, fibrosis, cholangitis, cirrhosis, and hepatocellular carcinoma (HCC). Gal-3 directly interacts with the NOD-like receptor family, pyrin domain containing 3, and activates the inflammasome in macrophages of the liver. In the chronically injured liver, Gal-3 secreted by injured hepatocytes and immune cells, activates hepatic stellate cells (HSCs) in a paracrine fashion to acquire a myofibroblast like collagen-producing phenotype. Activated HSCs in the fibrotic liver secrete Gal-3 which acts via autocrine signaling to exacerbate extracellular matrix synthesis and fibrogenesis. In the stromal microenvironment, Gal-3 activates cancer cell proliferation, migration, invasiveness, and metastasis. Clinically, increased serum levels and Gal-3 expression were observed in the liver tissue of nonalcoholic steatohepatitis, fibrotic/cirrhotic, and HCC patients. The pathological role of Gal-3 has been experimentally and clinically reported in the progression of chronic liver disease. Therefore, this review discusses the pathological role of Gal-3 in the progression of chronic liver diseases.

The Role of Plant Lectins in the Cellular and Molecular Processes of Skin Wound Repair: An Overview

There is increasing pressure for innovative methods to treat compromised and difficult-to-heal wounds. Consequently, new strategies are needed for faster healing, reducing infection, hydrating the wound, stimulating healing mechanisms, accelerating wound closure, and reducing scar formation. In this scenario, lectins present as good candidates for healing agents. Lectins are a structurally heterogeneous group of glycosylated or non-glycosylated proteins of non-immune origin, which can recognize at least one specific monosaccharide or oligosaccharide specific for the reversible binding site. Cell surfaces are rich in glycoproteins (glycosidic receptors) that potentially interact with lectins through the number of carbohydrates reached. This lectin-cell interaction is the molecular basis for triggering various changes in biological organisms, including healing mechanisms. In this context, this review aimed to (i) provide a comprehensive overview of relevant research on the potential of vegetable lectins for wound healing and tissue regeneration processes and (ii) discuss future perspectives.

Vaccination against galectin-1 promotes cytotoxic T-cell infiltration in melanoma and reduces tumor burden

Galectin-1 (Gal1) is a glycan-binding protein that promotes tumor progression by several distinct mechanisms. Through direct binding to vascular endothelial growth factor (VEGF)-receptor 2, Gal1 is able to induce VEGF-like signaling, which contributes to tumor angiogenesis. Furthermore, several studies have demonstrated an immunosuppressive function of Gal1 through effects on both effector and regulatory T cells. Elevated Gal1 expression and secretion have been shown in many tumor types, and high Gal1 serum levels have been connected to poor prognosis in cancer patients. These findings suggest that therapeutic strategies directed against Gal1 would enable simultaneous targeting of angiogenesis, immune evasion and metastasis. In the current study, we have analyzed the potential of Gal1 as a cancer vaccine target. We show that it is possible to generate high anti-Gal1 antibody levels in mice immunized with a recombinant vaccine protein consisting of bacterial sequences fused to Gal1. Growth of Gal1 expressing melanomas was significantly impaired in the immunized mice compared to the control group. This was associated with improved perfusion of the tumor vasculature, as well as increased infiltration of macrophages and cytotoxic T cells (CTLs). The level of granzyme B, mainly originating from CTLs in our model, was significantly elevated in Gal1 vaccinated mice and correlated with a decrease in tumor burden. We conclude that vaccination against Gal1 is a promising pro-immunogenic approach for cancer therapy that could potentially enhance the effect of other immunotherapeutic strategies due to its ability to promote CTL influx in tumors.

Use of Glycoproteins-Prostate-Specific Membrane Antigen and Galectin-3 as Primary Tumor Markers and Therapeutic Targets in the Management of Metastatic Prostate Cancer

Simple Summary

Prostate specific membrane antigen and galectins are proteins expressed on cell surface and their expression is associated with cancer growth and spread. The goal of this research was to look at the pattern of these two glycoproteins in the human prostate cancer microenvironment. Prostate specific membrane antigen and galectins-1,3 and 8 were the most frequently detected glycoproteins in various phases of this disease. Furthermore, prostate specific membrane antigen and galectin-3 expression are good indicators of tumor aggressiveness, and their combined expression can be valuable tool for prostate cancer diagnosis and treatment in future. Together, our findings reveal a tightly regulated “Prostate specific membrane antigen-galectin-pattern” that accompanies disease in prostate cancer and point to a key role for combined prostate specific membrane antigen and galectin-3 inhibitors in prostate cancer treatment along with standard chemotherapy.

Abstract

Galectins and prostate specific membrane antigen (PSMA) are glycoproteins that are functionally implicated in prostate cancer (CaP). We undertook this study to analyze the “PSMA-galectin pattern” of the human CaP microenvironment with the overarching goal of selecting novel-molecular targets for prognostic and therapeutic purposes. We examined CaP cells and biopsy samples representing different stages of the disease and found that PSMA, Gal-1, Gal-3, and Gal-8 are the most abundantly expressed glycoproteins. In contrast, other galectins such as Gal-2, 4–7, 9–13, were uniformly expressed at lower levels across all cell lines. However, biopsy samples showed markedly higher expression of PSMA, Gal-1 and Gal-3. Independently PSA and Gleason score at diagnosis correlated with the expression of PSMA, Gal-3. Additionally, the combined index of PSMA and Gal-3 expression positively correlated with Gleason score and was a better predictor of tumor aggressiveness. Together, our results recognize a tightly regulated “PSMA-galectin- pattern” that accompanies disease in CaP and highlight a major role for the combined PSMA and Gal-3 inhibitors along with standard chemotherapy for prostate cancer treatment. Inhibitor combination studies show enzalutamide (ENZ), 2-phosphonomethyl pentanedioic acid (2-PMPA), and GB1107 as highly cytotoxic for LNCaP and LNCaP-KD cells, while Docetaxel (DOC) + GB1107 show greater efficacy in PC-3 cells. Overall, 2-PMPA and GB1107 demonstrate synergistic cytotoxic effects with ENZ and DOC in various CaP cell lines.

Examination of the Role of Galectins and Galectin Inhibitors in Endothelial Cell Biology

The growth of new blood vessels is a key event in many (patho) physiological processes, including embryogenesis, wound healing, inflammatory diseases, and cancer. Neovascularization requires different, well-coordinated actions of endothelial cells, i.e., the cells lining the luminal side of all blood vessels. Galectins are involved in several of these activities. In this chapter, we describe methods to study galectins in three key functions of endothelial cells during angiogenesis, i.e., endothelial cell migration, endothelial cell sprouting, and endothelial cell network formation.

Comparative Transcriptomic Analysis of Regenerated Skins Provides Insights into Cutaneous Air-Breathing Formation in Fish

Cutaneous air-breathing is one of the air-breathing patterns in bimodal respiration fishes, while little is known about its underlying formation mechanisms. Here, we first investigated the skin regeneration of loach (Misgurnus anguillicaudatus, a cutaneous air-breathing fish) and yellow catfish (Pelteobagrus fulvidraco, a water-breathing fish) through morphological and histological observations. Then, the original skins (OS: MOS, POS) and regenerated skins (RS: MRS, PRS) when their capillaries were the most abundant (the structural foundation of air-breathing in fish) during healing, of the two fish species were collected for high-throughput RNA-seq. A total of 56,054 unigenes and 53,731 unigenes were assembled in loach and yellow catfish, respectively. A total of 640 (460 up- and 180 down-regulated) and 4446 (2340 up- and 2106 down-regulated) differentially expressed genes (DEGs) were respectively observed in RS/OS of loach and yellow catfish. Subsequently, the two DEG datasets were clustered in GO, KOG and KEGG databases, and further analyzed by comparison and screening. Consequently, tens of genes and thirteen key pathways were targeted, indicating that these genes and pathways had strong ties to cutaneous skin air-breathing in loach. This study provides new insights into the formation mechanism of cutaneous air-breathing and also offers a substantial contribution to the gene expression profiles of skin regeneration in fish.

Glycosylation of PAMAM dendrimers significantly improves tumor macrophage targeting and specificity in glioblastoma

Glioblastoma is among the most aggressive forms of cancers, with a median survival of just 15-20 months for patients despite maximum clinical intervention. The majority of conventional anti-cancer therapies fail due to associated off-site toxicities which can be addressed by developing target-specific drug delivery systems. Advances in nanotechnology have provided targeted systems to overcome drug delivery barriers associated with brain and other types of cancers. Dendrimers have emerged as promising vehicles for targeted drug and gene delivery. Dendrimer-mediated targeting strategies can be further enhanced through the addition of targeting ligands to enable receptor-specific interactions. Here, we explore the sugar moieties as ligands conjugated to hydroxyl-terminated polyamidoamine dendrimers to leverage altered metabolism in cancer and immune targeting. Using a highly facile click chemistry approach, we modified the surface of dendrimers with glucose, mannose, or galactose moieties in a well-defined manner, to target upregulated sugar transporters in the context of glioblastoma. We show that glucose modification significantly enhanced targeting of tumor-associated macrophages (TAMs) and microglia by increasing brain penetration and cellular internalization, while galactose modification shifts targeting away from TAMs towards galectins on glioblastoma tumor cells. Mannose modification did not alter TAMs and microglia targeting of these dendrimers, but did alter their kinetics of accumulation within the GBM tumor. The whole body biodistribution was largely similar between the systems. These results demonstrate that dendrimers are versatile delivery vehicles that can be modified to tailor their targeting for the treatment of glioblastoma and other cancers.

Sperm Functional Genome Associated With Bull Fertility

Bull fertility is an important economic trait in sustainable cattle production, as infertile or subfertile bulls give rise to large economic losses. Current methods to assess bull fertility are tedious and not totally accurate. The massive collection of functional data analyses, including genomics, proteomics, metabolomics, transcriptomics, and epigenomics, helps researchers generate extensive knowledge to better understand the unraveling physiological mechanisms underlying subpar male fertility. This review focuses on the sperm phenomes of the functional genome and epigenome that are associated with bull fertility. Findings from multiple sources were integrated to generate new knowledge that is transferable to applied andrology. Diverse methods encompassing analyses of molecular and cellular dynamics in the fertility-associated molecules and conventional sperm parameters can be considered an effective approach to determine bull fertility for efficient and sustainable cattle production. In addition to gene expression information, we also provide methodological information, which is important for the rigor and reliability of the studies. Fertility is a complex trait influenced by several factors and has low heritability, although heritability of scrotal circumference is high and that it is a known fertility maker. There is a need for new knowledge on the expression levels and functions of sperm RNA, proteins, and metabolites. The new knowledge can shed light on additional fertility markers that can be used in combination with scrotal circumference to predict the fertility of breeding bulls. This review provides a comprehensive review of sperm functional characteristics or phenotypes associated with bull fertility.

Galectins in the Pathogenesis of Common Retinal Disease

Diseases of the retina are major causes of visual impairment and blindness in developed countries and, due to an ageing population, their prevalence is continually rising. The lack of effective therapies and the limitations of those currently in use highlight the importance of continued research into the pathogenesis of these diseases. Vascular endothelial growth factor (VEGF) plays a major role in driving vascular dysfunction in retinal disease and has therefore become a key therapeutic target. Recent evidence also points to a potentially similarly important role of galectins, a family of β-galactoside-binding proteins. Indeed, they have been implicated in regulating fundamental processes, including vascular hyperpermeability, angiogenesis, neuroinflammation, and oxidative stress, all of which also play a prominent role in retinopathies. Here, we review direct evidence for pathological roles of galectins in retinal disease. In addition, we extrapolate potential roles of galectins in the retina from evidence in cancer, immune and neuro-biology. We conclude that there is value in increasing understanding of galectin function in retinal biology, in particular in the context of the retinal vasculature and microglia. With greater insight, recent clinical developments of galectin-targeting drugs could potentially also be of benefit to the clinical management of many blinding diseases.

Galectin-3 N-terminal tail prolines modulate cell activity and glycan-mediated oligomerization/phase separation

Galectin-3 (Gal-3) has a long, aperiodic, and dynamic proline-rich N-terminal tail (NT). The functional role of the NT with its numerous prolines has remained enigmatic since its discovery. To provide some resolution to this puzzle, we individually mutated all 14 NT prolines over the first 68 residues and assessed their effects on various Gal-3-mediated functions. Our findings show that mutation of any single proline (especially P37A, P55A, P60A, P64A/H, and P67A) dramatically and differentially inhibits Gal-3-mediated cellular activities (i.e., cell migration, activation, endocytosis, and hemagglutination). For mechanistic insight, we investigated the role of prolines in mediating Gal-3 oligomerization, a fundamental process required for these cell activities. We showed that Gal-3 oligomerization triggered by binding to glycoproteins is a dynamic process analogous to liquid-liquid phase separation (LLPS). The composition of these heterooligomers is dependent on the concentration of Gal-3 as well as on the concentration and type of glycoprotein. LLPS-like Gal-3 oligomerization/condensation was also observed on the plasma membrane and disrupted endomembranes. Molecular- and cell-based assays indicate that glycan binding-triggered Gal-3 LLPS (or LLPS-like) is driven mainly by dynamic intermolecular interactions between the Gal-3 NT and the carbohydrate recognition domain (CRD) F-face, although NT-NT interactions appear to contribute to a lesser extent. Mutation of each proline within the NT differentially controls NT-CRD interactions, consequently affecting glycan binding, LLPS, and cellular activities. Our results unveil the role of proline polymorphisms (e.g., at P64) associated with many diseases and suggest that the function of glycosylated cell surface receptors is dynamically regulated by Gal-3.

Immunosuppressive Property of MSCs Mediated by Cell Surface Receptors

In the past decade, mesenchymal stem cells (MSCs) tend to exhibit inherent tropism for refractory inflammatory diseases and engineered MSCs have appeared on the market as therapeutic agents. Recently, engineered MSCs target to cell surface molecules on immune cells has been a new strategy to improve MSC applications. In this review, we discuss the roles of multiple receptors (ICAM-1, Gal-9, PD-L1, TIGIT, CD200, and CXCR4) in the process of MSCs' immunosuppressive properties. Furthermore, we discuss the principles and strategies for developing receptor-regulated MSCs and their mechanisms of action and the challenges of using MSCs as immunosuppressive therapies.

Galectin-3 in Inflammasome Activation and Primary Biliary Cholangitis Development

Primary biliary cholangitis (PBC) is a chronic inflammatory autoimmune liver disease characterized by inflammation and damage of small bile ducts. The NLRP3 inflammasome is a multimeric complex of proteins that after activation with various stimuli initiates an inflammatory process. Increasing data obtained from animal studies implicate the role of NLRP3 inflammasome in the pathogenesis of various diseases. Galectin-3 is a β-galactoside-binding lectin that plays important roles in various biological processes including cell proliferation, differentiation, transformation and apoptosis, pre-mRNA splicing, inflammation, fibrosis and host defense. The multilineage immune response at various stages of PBC development includes the involvement of Gal-3 in the pathogenesis of this disease. The role of Galectin-3 in the specific binding to NLRP3, and inflammasome activation in models of primary biliary cholangitis has been recently described. This review provides a brief pathogenesis of PBC and discusses the current knowledge about the role of Gal-3 in NLRP3 activation and PBC development.

Expression pattern of galectin-1 and galectin-3 in rat testes and epididymis during postnatal development

Galectins are a family of lectins-binding beta-galactosides involved in a variety of extracellular and intracellular processes, thereby contributing to homeostasis, cell adhesion, cellular turnover, and immunity. This study aimed to determine the localization and expression of galectin-1 (Gal-1) and galectin-3 (Gal-3) in the testis and epididymis of rats at postnatal [(prepubertal (day 5), pubertal (day 20), postpubertal (day 50) and mature (day 70)] periods by using immunohistochemistry and Western blotting. Gal-1 and Gal-3 were differentially expressed in different types of cells in the testis and epididymis during postnatal development. While we detected Gal-1 expression in some spermatogenic cells and Leydig cells in the testis, not in the epididymal epithelium, Gal-3 was expressed in Sertoli cells, peritubular myoid cells, Leydig cells, smooth muscles and interstitial CD68-positive macrophages. Epithelial cells of the corpus and cauda epididymis showed an intense Gal-3 expression. Gal-1 expression was higher in the testis than in the epididymis on days 50 and 70. The expression of Gal-3 in the testis increased from the prepubertal to mature period. While the expression difference of Gal-3 was not statistically significant in the testis and epididymis until puberty, Gal-3 expression in the postpubertal and mature periods was higher in the epididymis. The expression of Gal-3 in the corpus and cauda epididymis was higher than that in the caput epididymis. In conclusion, our findings suggest that puberty has potential regulatory effect on the expression of galectins in testis and epididymis of rats. Gal-1 and 3 may play a role in the development of the reproductive system and the preservation of the immune-privileged environment in the testis, due to their pro-apoptotic and anti-apoptotic functions. The presence of intense expression of Gal-3 in the corpus and cauda epididymis may contribute to the maturation and storage of spermatozoa.

Mesenchymal stem cells alleviate experimental autoimmune cholangitis through immunosuppression and cytoprotective function mediated by galectin-9

Background

Mesenchymal stem cells (MSCs) play an anti-inflammatory role by secreting certain bioactive molecules to exert their therapeutic effects for disease treatment. However, the underlying mechanism of MSCs in chronic autoimmune liver diseases—primary biliary cholangitis (PBC), for example—remains to be elucidated.

Methods

Human umbilical cord–derived MSCs (UC-MSCs) were injected intravenously into 2-octynoic acid coupled to bovine serum albumin (2OA-BSA)-induced autoimmune cholangitis mice. Serum levels of biomarkers and autoantibodies, histologic changes in the liver, diverse CD4⁺ T-cell subsets in different tissues, and chemokine activities were analyzed. Moreover, we investigated galectin-9 (Gal-9) expression and its function in UC-MSCs.

Results

In this study, UC-MSC transplantation (UC-MSCT) significantly ameliorated liver inflammation, primarily by diminishing T helper 1 (Th1) and Th17 responses as well as modifying liver chemokine activities in experimental autoimmune cholangitis mice. Mechanistically, UC-MSCs significantly repressed the proliferation of CD4⁺ T cells and suppressed the differentiation of Th1 and Th17 cells, which was likely dependent on Gal-9. Furthermore, the signal transducer and activator of transcription (STAT) and c-Jun N-terminal kinase (JNK) signaling pathways were involved in the production of Gal-9 in UC-MSCs.

Conclusions

These results suggest that Gal-9 contributes significantly to UC-MSC–mediated therapeutic effects and improve our understanding of the immunomodulatory mechanisms of MSCs in the treatment of PBC.

Electronic supplementary material

The online version of this article (10.1186/s13287-018-0979-x) contains supplementary material, which is available to authorized users.

A potential role of galectin-1 in promoting mouse trophoblast stem cell differentiation

Galectin-1 is highly expressed in blastocysts and trophoblast giant cells during implantation, and dysregulated galectin-1 is associated with many pregnancy-related abnormalities. Elevated galectin-1 contributes to cancer cells invasion. Here, we found that galectin-1 is expressed in mouse oocytes, preimplantation embryos (all stages), and trophoblast stem (TS) cells. Peak levels of galectin-1 mRNA and protein were detected on day 4 and day 5 after the induction of TS cells differentiation. Overexpression of galectin-1 increased TS cells migration and invasion, whereas knockdown of galectin-1 attenuated these effects. Additionally, knockdown of galectin-1 in TS cells decreased the expression of matrix metalloproteinase (MMP) 2/9, ZEB-1, Snail, N-cadherin, TGF-β, Nodal, and phospho-Smad2/3, whereas the expression of E-cadherin was increased. In contrast, overexpression of galectin-1 in TS cells increased the expression of MMP2/9, ZEB-1, and N-cadherin, whereas the expression of E-cadherin was decreased. These findings suggest a potential role of galectin-1 in the differentiation of mouse TS cells.

The Role of Galectins in Cervical Cancer Biology and Progression

Cervical cancer is one of the malignant tumors with high incidence and high mortality among women in developing countries. The main factors affecting the prognosis of cervical cancer are the late recurrence and metastasis and the effective adjuvant treatment, which is radiation and chemotherapy or combination therapy. Galectins, a family containing many carbohydrate binding proteins, are closely involved in the occurrence and development of tumor. They are involved in tumor cells transformation, angiogenesis, metastasis, immune escape, and sensitivity against radiation and chemotherapy. Therefore, galectins are deemed as the targets of multifunctional cancer treatment. In this review, we mainly focus on the role of galectins, especially galectin-1, galectin-3, galectin-7, and galectin-9 in cervical cancer, and provide theoretical basis for potential targeted treatment of cervical cancer.

Anti-CTLA-4 based therapy elicits humoral immunity to galectin-3 in patients with metastatic melanoma

The combination of CTLA-4 blockade ipilimumab (Ipi) with VEGF-A blocking antibody bevacizumab (Bev) has demonstrated favorable clinical outcomes in patients with advanced melanoma. Galectin-3 (Gal-3) plays a prominent role in tumor growth, metastasis, angiogenesis, and immune evasion. Here we report that Ipi plus Bev (Ipi-Bev) therapy increased Gal-3 antibody titers by 50% or more in approximately one third of treated patients. Antibody responses to Gal-3 were associated with higher complete and partial responses and better overall survival. Ipi alone also elicited antibody responses to Gal-3 at a frequency comparable to the Ipi-Bev combination. However, an association of elicited antibody responses to Gal-3 with clinical outcomes was not observed in Ipi alone treated patients. In contrast to being neutralized in Ipi-Bev treated patients, circulating VEGF-A increased by 100% or more in a subset of patients after Ipi treatment, with most having progressive disease. Among the Ipi treated patients with therapy-induced Gal-3 antibody increases, circulating VEGF-A was increased in 3 of 6 nonresponders but in none of 4 responders as a result of treatment. Gal-3 antibody responses occurred significantly less frequently (3.2%) in a cohort of patients receiving PD-1 blockade where high pre-treatment serum Gal-3 was associated with reduced OS and response rates. Our findings suggest that anti-CTLA-4 elicited humoral immune responses to Gal-3 in melanoma patients which may contribute to the antitumor effect in the presence of an anti-VEGF-A combination. Furthermore, pre-treatment circulating Gal-3 may potentially have prognostic and predictive value for immune checkpoint therapy.

Radiation-enhanced therapeutic targeting of galectin-1 enriched malignant stroma in triple negative breast cancer

Currently there are no FDA approved targeted therapies for Triple Negative Breast Cancer (TNBC). Ongoing clinical trials for TNBC have focused primarily on targeting the epithelial cancer cells. However, targeted delivery of cytotoxic payloads to the non-transformed tumor associated-endothelium can prove to be an alternate approach that is currently unexplored. The present study is supported by recent findings on elevated expression of stromal galectin-1 in clinical samples of TNBC and our ongoing findings on stromal targeting of radiation induced galectin-1 by the anginex-conjugated arsenic-cisplatin loaded liposomes using a novel murine tumor model. We demonstrate inhibition of tumor growth and metastasis in response to the multimodal nanotherapeutic strategy using a TNBC model with orthotopic tumors originating from 3D tumor tissue analogs (TTA) comprised of tumor cells, endothelial cells and fibroblasts. The ‘rigorous’ combined treatment regimen of radiation and targeted liposomes is also shown to be well tolerated. More importantly, the results presented provide a means to exploit clinically relevant radiation dose for concurrent receptor mediated enhanced delivery of chemotherapy while limiting overall toxicity. The proposed study is significant as it falls in line with developing combinatorial therapeutic approaches for stroma-directed tumor targeting using tumor models that have an appropriate representation of the TNBC microenvironment.

Advanced glycation endproducts link inflammatory cues to upregulation of galectin-1 in diabetic retinopathy

Diabetic retinopathy (DR) is an inflammatory and progressive vaso-occlusive disease resulting in angiogenesis. Galectin-1 is a hypoxia-induced angiogenic factor associated with cancer and proliferative DR. Here we reveal a significant upregulation of galectin-1 in eyes of DR patients along with progression of clinical stages beginning from the pre-ischemic, inflammatory stage with diabetic macular edema, but not in eyes with non-diabetic retinal vascular occlusions. As for its regulatory mechanism unrelated to hypoxia but selective to DR, in vitro galectin-1/LGALS1 expression was shown to increase after application to Müller glial cells with interleukin (IL)-1β, which was induced in monocyte-derived macrophages and microglial cells via toll-like receptor (TLR) 4 signaling stimulated by advanced glycation endproducts (AGE). In vivo inhibition of AGE generation with aminoguanidine, macrophage depletion with clodronate liposomes, and antibody-based blockade of Il-1β and Tlr4 attenuated diabetes-induced retinal Lgals1 expression in mice. Fibrovascular tissues from proliferative DR eyes were immunoreactive for AGE, TRL4 and IL-1β in macrophages, and IL-1β receptor-positive glial cells expressed galectin-1. Therefore, diabetes-induced retinal AGE accumulation was suggested to activate IL-1β-related inflammatory cues in macrophages followed by Müller cells, linking to galectin-1 upregulation in human DR with time. Our data highlight AGE-triggered inflammation as the DR-selective inducer of galectin-1.

Secretion of IFN-γ Associated with Galectin-9 Production by Pleural Fluid Cells from a Patient with Extrapulmonary Tuberculosis

In this study, we investigated the role of a matricellular protein galectin-9 (Gal-9) in pleural effusion related to tuberculosis (TB). Plasma and pleural fluid of a patient with extrapulmonary TB were analyzed for cytokine content by ELISA and Luminex. Peripheral blood mononuclear cells (PBMCs) and pleural fluid cells (PFCs) were examined for interferon-γ (IFN-γ) secretion by the enzyme-linked immunospot (ELISPOT) assay or IFN-γ ELISA, for apoptosis and necrosis by Cell Death Detection ELISA, and also underwent cell sorting. The results indicate that compared to plasma, pleural fluid had increased levels of IFN-γ (1.6 vs. 55.5 pg/mL), IL-10, IL-12p40, vascular endothelial growth factor (VEGF), and Gal-9 (3.0 vs. 936.0 pg/mL), respectively. PFCs culture supernatant exhibited higher concentration of Gal-9 compared to PBMCs in culture, consistent with enriched Gal-9 staining in the granuloma that is in closer vicinity to PFCs compared to PBMCs. PFCS displayed higher IFN-γ secretion after stimulation with TB antigens ESAT-6/CFP-10. Furthermore, in PFCs, Gal-9 alone could stimulate IFN-γ synthesis in culture or ELISPOT, which was inhibited by a Gal-9 antagonist lactose, and which may promote apoptosis and necrosis. These findings suggest that Gal-9 could modulate immune responses and participate in immunopathology of pleural effusion during TB.

Combined Anti-VEGF and Anti-CTLA-4 Therapy Elicits Humoral Immunity to Galectin-1 Which Is Associated with Favorable Clinical Outcomes

The combination of anti-VEGF blockade (bevacizumab) with immune checkpoint anti-CTLA-4 blockade (ipilimumab) in a phase I study showed tumor endothelial activation and immune cell infiltration that were associated with favorable clinical outcomes in patients with metastatic melanoma. To identify potential immune targets responsible for these observations, posttreatment plasma from long-term responding patients were used to screen human protein arrays. We reported that ipilimumab plus bevacizumab therapy elicited humoral immune responses to galectin-1 (Gal-1), which exhibits protumor, proangiogenesis, and immunosuppressive activities in 37.2% of treated patients. Gal-1 antibodies purified from posttreatment plasma suppressed the binding of Gal-1 to CD45, a T-cell surface receptor that transduces apoptotic signals upon binding to extracellular Gal-1. Antibody responses to Gal-1 were found more frequently in the group of patients with therapeutic responses and correlated with improved overall survival. In contrast, another subgroup of treated patients had increased circulating Gal-1 protein instead, and they had reduced overall survival. Our findings suggest that humoral immunity to Gal-1 may contribute to the efficacy of anti-VEGF and anti-CTLA-4 combination therapy. Gal-1 may offer an additional therapeutic target linking anti-angiogenesis and immune checkpoint blockade. Cancer Immunol Res; 5(6); 446-54. ©2017 AACR.

The clinical application of angiostatic therapy in combination with radiotherapy: past, present, future

Although monotherapy with angiostatic drugs is still far from effective, there is abundant evidence that angiostatic therapy can improve the efficacy of conventional treatments like radiotherapy. This has instigated numerous efforts to optimize and clinically implement the combination of angiostatic drugs with radiation treatment. The results from past and present clinical trials that explored this combination therapy indeed show encouraging results. However, current findings also show that the combination has variable efficacy and is associated with increased toxicity. This indicates that combining radiotherapy with angiostatic drugs not only holds opportunities but also provides several challenges. In the current review, we provide an update of the most recent insights from clinical trials that evaluated the combination of angiostatic drugs with radiation treatment. In addition, we discuss the outstanding questions for future studies in order to improve the clinical benefit of combining angiostatic therapy with radiation therapy.

Immunomodulation by Mesenchymal Stromal Cells and Their Clinical Applications

Mesenchymal stromal cells (MSCs) are multipotent progenitor cells that can be isolated and expanded from various sources. MSCs modulate the function of immune cells, including T and B lymphocytes, dendritic cells, and natural killer cells. An understanding of the interaction between MSCs and the inflammatory microenvironment will provide critical information in revealing the precise in vivo mechanisms involved in MSCs-mediated therapeutic effects, and for designing more practical protocols for the clinical use of these cells. In this review we describe the current knowledge of the unique biological properties of MSCs, the immunosuppressive effects on immune-competent cells and the paracrine role of soluble factors. A summary of the participation of MSCs in preclinical and clinical studies in treating autoimmune diseases and other diseases is described. We also discuss the current challenges of their use and their potential roles in cell therapies.

Multiple approaches to assess pectin binding to galectin-3

Although several approaches have been used to evaluate binding of carbohydrates to lectins, results are not always comparable, especially with larger polysaccharides. Here, we quantitatively assessed and compared binding of pectin-derived polysaccharides to galectin-3 (Gal-3) using five methods: surface plasmon resonance (SPR), bio-layer interferometry (BLI), fluorescence polarization (FP), competitive fluorescence-linked immunosorbance (cFLISA), and the well-known cell-based hemagglutination assay (G3H). Our studies revealed that whereas Gal-3-pectin binding parameters determined by SPR and BLI were comparable and correlated with inhibitory potencies from the G3H assay, results using FP and cFLISA assays were highly variable and depended greatly on the probe and mass of the polysaccharide. In the cFLISA assay, for example, pectins showed no inhibition when using the DTAF-labeled asialofetuin probe, but did when using a DTAF-labeled pectin probe. And the FP approach with the DTAF-lactose probe did not work on polysaccharides and large galactan chains, although it did work well with smaller galactans. Nevertheless, even though results derived from all of these methods are in general agreement, derived KD, IC50, and MIC values do differ. Our results reflect the variability using various techniques and therefore will be useful to investigators who are developing pectin-derived Gal-3 antagonists as anti-cancer agents.

The role of pattern recognition receptors in the innate recognition of Candida albicans

Candida albicans is both a commensal microorganism in healthy individuals and a major fungal pathogen causing high mortality in immunocompromised patients. Yeast-hypha morphological transition is a well known virulence trait of C. albicans. Host innate immunity to C. albicans critically requires pattern recognition receptors (PRRs). In this review, we summarize the PRRs involved in the recognition of C. albicans in epithelial cells, endothelial cells, and phagocytic cells separately. We figure out the differential recognition of yeasts and hyphae, the findings on PRR-deficient mice, and the discoveries on human PRR-related single nucleotide polymorphisms (SNPs).

Aflibercept Traps Galectin-1, an Angiogenic Factor Associated with Diabetic Retinopathy

Vascular endothelial growth factor (VEGF)-A-driven angiogenesis contributes to various disorders including cancer and proliferative diabetic retinopathy (PDR). Among several VEGF-A blockers clinically used is aflibercept, a chimeric VEGFR1/VEGFR2-based decoy receptor fused to the Fc fragment of IgG1 (i.e., VEGFR1/VEGFR2-Fc). Here, we revealed a novel anti-angiogenic function for aflibercept beyond its antagonism against VEGF family members. Immunoprecipitation and mass spectrometry analyses identified galectin-1 as an aflibercept-interacting protein. Biolayer interferometry revealed aflibercept binding to galectin-1 with higher affinity than VEGFR1-Fc and VEGFR2-Fc, which was abolished by deglycosylation of aflibercept with peptide:N-glycosidase F. Retinal LGALS1/Galectin-1 mRNA expression was enhanced in vitro by hypoxic stimulation and in vivo by induction of diseases including diabetes. Galectin-1 immunoreactivity co-localized with VEGFR2 in neovascular tissues surgically excised from human eyes with PDR. Compared with non-diabetic controls, intravitreal galectin-1 protein levels were elevated in PDR eyes, showing no correlation with increased VEGF-A levels. Preoperative injection of bevacizumab, a monoclonal antibody to VEGF-A, reduced the VEGF-A, but not galectin-1, levels. Galectin-1 application to human retinal microvascular endothelial cells up-regulated VEGFR2 phosphorylation, which was eliminated by aflibercept. Our present findings demonstrated the neutralizing efficacy of aflibercept against galectin-1, an angiogenic factor associated with PDR independently of VEGF-A.

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.

The great escape; the hallmarks of resistance to antiangiogenic therapy

The concept of antiangiogenic therapy in cancer treatment has led to the approval of different agents, most of them targeting the well known vascular endothelial growth factor pathway. Despite promising results in preclinical studies, the efficacy of antiangiogenic therapy in the clinical setting remains limited. Recently, awareness has emerged on resistance to antiangiogenic therapies. It has become apparent that the intricate complex interplay between tumors and stromal cells, including endothelial cells and associated mural cells, allows for escape mechanisms to arise that counteract the effects of these targeted therapeutics. Here, we review and discuss known and novel mechanisms that contribute to resistance against antiangiogenic therapy and provide an outlook to possible improvements in therapeutic approaches.

3D tumor tissue analogs and their orthotopic implants for understanding tumor-targeting of microenvironment-responsive nanosized chemotherapy and radiation

An appropriate representation of the tumor microenvironment in tumor models can have a pronounced impact on directing combinatorial treatment strategies and cancer nanotherapeutics. The present study develops a novel 3D co-culture spheroid model (3D TNBC) incorporating tumor cells, endothelial cells and fibroblasts as color-coded murine tumor tissue analogs (TTA) to better represent the tumor milieu of triple negative breast cancer in vitro. Implantation of TTA orthotopically in nude mice, resulted in enhanced growth and aggressive metastasis to ectopic sites. Subsequently, the utility of the model is demonstrated for preferential targeting of irradiated tumor endothelial cells via radiation-induced stromal enrichment of galectin-1 using anginex conjugated nanoparticles (nanobins) carrying arsenic trioxide and cisplatin. Demonstration of a multimodal nanotherapeutic system and inclusion of the biological response to radiation using an in vitro/in vivo tumor model incorporating characteristics of tumor microenvironment presents an advance in preclinical evaluation of existing and novel cancer nanotherapies.

FROM THE CLINICAL EDITOR

Existing in-vivo tumor models are established by implanting tumor cells into nude mice. Here, the authors described their approach 3D spheres containing tumor cells, enodothelial cells and fibroblasts. This would mimic tumor micro-environment more realistically. This interesting 3D model should reflect more accurately tumor response to various drugs and would enable the design of new treatment modalities.

Immunoregulation by mesenchymal stem cells: biological aspects and clinical applications

Mesenchymal stem cells (MSCs) are multipotent cells capable of differentiation into mesenchymal lineages and that can be isolated from various tissues and easily cultivated in vitro. Currently, MSCs are of considerable interest because of the biological characteristics that confer high potential applicability in the clinical treatment of many diseases. Specifically, because of their high immunoregulatory capacity, MSCs are used as tools in cellular therapies for clinical protocols involving immune system alterations. In this review, we discuss the current knowledge about the capacity of MSCs for the immunoregulation of immunocompetent cells and emphasize the effects of MSCs on T cells, principal effectors of the immune response, and the immunosuppressive effects mediated by the secretion of soluble factors and membrane molecules. We also describe the mechanisms of MSC immunoregulatory modulation and the participation of MSCs as immune response regulators in several autoimmune diseases, and we emphasize the clinical application in graft versus host disease (GVHD).

Examination of the role of galectins and galectin inhibitors in endothelial cell biology

The growth of new blood vessels is a key event in many (patho)physiological processes, including embryogenesis, wound healing, inflammatory diseases, and cancer. Neovascularization requires different, well-coordinated actions of endothelial cells, i.e., the cells lining the luminal side of all blood vessels. Galectins are involved in several of these activities. In this chapter we describe methods to study galectins and galectin inhibition in three key functions of endothelial cells during angiogenesis, i.e., endothelial cell migration, endothelial cell sprouting, and endothelial cell network formation.

Evolving mechanistic insights into galectin functions

Galectins are an evolutionarily ancient family of glycan-binding proteins (GBPs) and are found in all animals. Although they were discovered over 30 years ago, ideas about their biological functions continue to evolve. Current evidence indicates that galectins, which are the only known GBPs that occur free in the cytoplasm and extracellularly, are involved in a variety of intracellular and extracellular pathways contributing to homeostasis, cellular turnover, cell adhesion, and immunity. Here we review evolving insights into galectin biology from a historical perspective and explore current evidence regarding biological roles of galectins.

Galectins in angiogenesis: consequences for gestation

Members of the galectin family have been shown to exert several roles in the context of reproduction. They contribute to placentation, maternal immune regulation and facilitate angiogenesis encompassing decidualisation and placenta formation during pregnancy. In the context of neo-vascularisation, galectins have been shown to augment signalling pathways that lead to endothelial cell activation, cell proliferation, migration and tube formation in vitro in addition to angiogenesis in vivo. Angiogenesis during gestation ensures not only proper foetal growth and development, but also maternal health. Consequently, restriction of placental blood flow has major consequences for both foetus and mother, leading to pregnancy diseases. In this review we summarise both the established and the emerging roles of galectin in angiogenesis and discuss the possible implications during healthy and pathological gestation.

Role of galectins in re-epithelialization of wounds

Re-epithelialization is a critical contributing process in wound healing in the human body. When this process is compromised, impaired or delayed, serious disorders of wound healing may result that are painful, difficult to treat, and affect a variety of human tissues. Recent studies have demonstrated that members of the galectin class of β-galactoside-binding proteins modulate re-epithelialization of wounds by novel carbohydrate-based recognition systems. Galectins constitute a family of widely distributed carbohydrate-binding proteins with the affinity for the β-galactoside-containing glycans found on many cell surface and extracellular matrix (ECM) glycoproteins. There are 15 members of the mammalian galectin family that so far have been identified. Studies of the role of galectins in wound healing have revealed that galectin-3 promotes re-epithelialization of corneal, intestinal and skin wounds; galectin-7 promotes re-epithelialization of corneal, skin, kidney and uterine wounds; and galectins-2 and -4 promote re-epithelialization of intestinal wounds. Promising prospects for developing novel therapeutic strategies for the treatment of problematic, slow- or non-healing wounds are implicit in the findings that galectins stimulate the re-epithelialization of wounds of the cornea, skin, intestinal tract and kidney. Molecular mechanisms by which galectins modulate the process of wound healing are beginning to emerge and are described in this review.

Galectins in tumor angiogenesis

The expansion of solid tumors depends on the continuous ingrowth of new blood vessels out of pre-existing capillaries. Consequently, tumor neovascularization or tumor angiogenesis is considered a hallmark of cancer and an attractive target for cancer therapy. Tumor angiogenesis is mainly carried out by endothelial cells (EC), i.e., the cells lining the luminal vessel wall. These cells have to take on different functional activities in order to successfully make new tumor blood vessels. In the last decade it has become apparent that galectins are important regulators of tumor angiogenesis. In the present review we summarize the current knowledge regarding the role galectins in tumor angiogenesis focussing on the endothelial galectins, i.e., gal-1/-3/-8/-9.

Tumor-released Galectin-3, a soluble inhibitory ligand of human NKp30, plays an important role in tumor escape from NK cell attack

Human Galectin-3 (Gal-3), a β-galactoside-binding protein expressed by tumor cells, has been reported to act as an immune regulator in antitumor T cells. However, its effect on natural killer (NK) cells is elusive. Using a recombinant human NK cell-activating receptor, NKp30 fusion protein (NKp30-Fc), we found that soluble NKp30-Fc could immunoprecipitate Galectin-3. The direct interaction between NKp30 and Galectin-3 was further confirmed using surface plasmon resonance experiments. Because Galectin-3 was mainly released from tumor cells in a soluble form in our study, the binding assay was performed to show that soluble Galectin-3 specifically bound to NK cells and NKp30 on the surface of the NK cells. Functionally, when soluble Galectin-3 was added to the NK-tumor cell coculture system, the NKp30-mediated, but not NKG2D-mediated, cytolysis and CD107a expression in the NK cells were inhibited, and these phenotypes could be restored by preincubation of soluble Galectin-3 with NKp30-Fc fusion protein or the addition of anti-Gal-3 antibody alone. Moreover, genetic down-regulation of Galectin-3 (shGal-3) resulted in tumor cells being more sensitive to NK cell lysis, and, reversely, Galectin-3-overexpressing HeLa cells (exGal-3) became less sensitive to NK cell killing. The results of these in vitro experiments were supported by studies in shGal-3-HeLa or exGal-3-HeLa xenograft non-obese diabetic/severe combined immunodeficiency mice after NK cell adoptive immunotherapy, indicating that Galectin-3 strongly antagonizes human NK cell attack against tumors in vivo. These findings indicate that Galectin-3 may function as an immune regulator to inhibit NK cell function against tumors, therefore providing a new therapeutic target for tumor treatment.

Glycobiology of ocular angiogenesis

Ocular neovascularization can affect almost all the tissues of the eye: the cornea, the iris, the retina, and the choroid. Pathological neovascularization is the underlying cause of vision loss in common ocular conditions such as diabetic retinopathy, retinopathy of prematurity and age-related macular neovascularization. Glycosylation is the most common covalent posttranslational modification of proteins in mammalian cells. A growing body of evidence demonstrates that glycosylation influences the process of angiogenesis and impacts activation, proliferation, and migration of endothelial cells as well as the interaction of angiogenic endothelial cells with other cell types necessary to form blood vessels. Recent studies have provided evidence that members of the galectin class of β-galactoside-binding proteins modulate angiogenesis by novel carbohydrate-based recognition systems involving interactions between glycans of angiogenic cell surface receptors and galectins. This review discusses the significance of glycosylation and the role of galectins in the pathogenesis of ocular neovascularization.

Regulation of melanoma metastasis to lungs by cell surface Lysosome Associated Membrane Protein-1 (LAMP1) via galectin-3

Lysosome Associated Membrane Protein-1 (LAMP1), which lines the lysosomes, is often found to be expressed on surface of metastatic cells. We previously demonstrated that its surface expression on B16 melanoma variants correlates with metastatic potential. To establish the role of cell surface LAMP1 in metastasis and to understand the possible mechanism by which it facilitates lung colonization, LAMP1 was downregulated in high metastatic B16F10 cells using shRNAs cloned in a doxycycline inducible vector. This also resulted in significantly decreased LAMP1 on the cell surface. Being a major carrier of poly-N-acetyllactosamine (polyLacNAc) substituted β1,6 branched N-oligosaccharides, the high affinity ligands for galectin-3, LAMP1 down regulation also resulted in appreciably decreased binding of galectin-3 to the cell surface. LAMP1 has been shown to bind to Extracellular Matrix (ECM), Basement Membrane (BM) components and also to galectin-3 (via carbohydrates) which is known to get incorporated into the ECM and BM. Although, LAMP1 downregulation had a marginal effect on cellular spreading and motility on fibronectin and matrigel, it significantly altered the same on galectin-3, and ultimately leading to notably reduced lung metastasis. The results thus for the first time provide direct evidence that cell surface LAMP1 facilitates lung metastasis by providing ligands for galectin-3 which has been shown to be expressed in highest amounts on lungs and constitutively on its vascular endothelium.