Differential effect on TCR:CD3 stimulation of a 90-kD glycoprotein (gp90/Mac-2BP), a member of the scavenger receptor cysteine-rich domain protein family

LGALS3BP in Microglia Promotes Retinal Angiogenesis Through PI3K/AKT Pathway During Hypoxia

Purpose

Retinal microglia promote angiogenesis and vasculopathy in oxygen-induced retinopathy (OIR); however, its specific molecular mechanism in the formation of retinal angiogenesis remains unclear. The lectin galactoside-binding soluble 3 binding protein (LGALS3BP), a member of the scavenger receptor cysteine-rich (SRCR) domain protein family, is involved in tumor neovascularization, and we therefore hypothesized that LGALS3BP plays an active role in microglia-induced angiogenesis.

Methods

The expression of LGALS3BP in microglia was detected by immunofluorescence, RT-qPCR, and western blotting. Functional assays of human umbilical vein endothelial cells (HUVECs) such as migration, proliferation, and tube formation were measured by Transwell, EdU, and Matrigel assays. Angiogenesis-related factors and PI3K/AKT levels were detected by western blotting. The relationship between LGALS3BP and PI3K or HIF-1α was investigated by immunoprecipitation.

Results

Our results showed that the expression of LGALS3BP was significantly increased in microglia surrounding neovascularization of the OIR mice and was also upregulated in human microglial clone 3 (HMC3) cells after hypoxia. Moreover, HUVECs co-cultured with hypoxic HMC3 cells showed increased migration, proliferation, and tube formation, as well as levels of angiogenesis-related factor. However, the proangiogenic ability and angiogenesis-related factor expression of HMC3 cells was suppressed after silencing LGALS3BP. LGALS3BP induces the upregulation of angiogenesis-related factors through the PI3K/AKT pathway and then promotes angiogenesis in microglia.

Conclusions

Collectively, our findings suggest that LGALS3BP in microglia plays an important role in angiogenesis, suggesting a potential therapeutic target of LGALS3BP for angiogenesis.

Lgals3bp suppresses colon inflammation and tumorigenesis through the downregulation of TAK1-NF-κB signaling

Galectin 3-binding protein (LGALS3BP, also known as 90K) is a multifunctional glycoprotein involved in immunity and cancer. However, its precise role in colon inflammation and tumorigenesis remains unclear. Here, we showed that Lgals3bp-/- mice were highly susceptible to colitis and colon tumorigenesis, accompanied by the induction of inflammatory responses. In acute colitis, NF-κB was highly activated in the colon of Lgals3bp-/- mice, leading to the excessive production of pro-inflammatory cytokines, such as IL-6, TNFα, and IL-1β. Mechanistically, Lgals3bp suppressed NF-κB through the downregulation of TAK1 in colon epithelial cells. There was no significant difference in the pro-inflammatory cytokine levels between wild-type and Lgals3bp-/- mice in a chronic inflammatory state, during colon tumorigenesis. Instead, Lgals3bp-/- mice showed elevated levels of GM-CSF, compared to those in WT mice. We also found that GM-CSF promoted the accumulation of myeloid-derived suppressor cells and ultimately increased colon tumorigenesis in Lgals3bp-/- mice. Taken together, Lgals3bp plays a critical role in the suppression of colitis and colon tumorigenesis through the downregulation of the TAK1-NF-κB-cytokine axis. These findings suggest that LGALS3BP is a novel immunotherapeutic target for colon inflammation and tumorigenesis.

Galectin-3-binding protein: A multitask glycoprotein with innate immunity functions in viral and bacterial infections

Galectin-3-binding protein (Gal-3BP) is a ubiquitous and multifunctional secreted glycoprotein originally identified and mainly studied in the context of neoplastic transformation and cancer progression. However, Gal-3BP expression is induced in viral infection and by a multitude of molecules that either mimic or are characteristic for an ongoing inflammation and microbial infection, such as IFN-α, IFN-β, IFN-γ, TNF-α, poly(I:C), dsRNA, and dsDNA. Furthermore, Gal-3BP belongs to the scavenger receptor cysteine-rich (SRCR) domain-containing protein family, by virtue of its N-terminal SRCR domain. The SRCR domain is found in soluble or membrane-associated innate immunity-related proteins and is implicated in self-nonself discrimination. This review summarizes the current knowledge of structural features of Gal-3BP and its proposed intracellular and extracellular innate immunity functions with special emphasis on viral and bacterial infections.

90K immunostimulatory glycoprotein in children with juvenile idiopathic arthritis

OBJECTIVES

To assess whether circulating levels of 90K glycoprotein are increased in children with juvenile idiopathic arthritis (JIA) at different stages of the disease, compared to healthy controls and to evaluate potential over time changes in its concentrations following treatment with the antitumor-necrosis factor (TNF) drug etanercept.

METHODS

90K glycoprotein, C-reactive protein, erythrocyte sedimentation rate, TNF, antinuclear antibodies, rheumatoid factor and the Juvenile Arthritis Disease Activity Score were assessed in 71 children: 23 with newly diagnosed JIA, 23 with established and active JIA and 25 healthy controls. Patients, eligible for anti-TNF treatment, underwent a similar clinical/laboratory assessment after 6- and 12-month etanercept therapy.

RESULTS

At baseline, significant differences were found in 90K levels between the three study groups: JIA at onset (157.7 [131.4-241.5] μg/ml), JIA on treatment (90.0 [68.8-120.2] μg/ml) and control group (58.0 [44.5-79.0] μg/ml), (p for trend <.001), with the JIA at onset group showing the highest values. In the JIA on treatment group, following one-year etanercept treatment, a significant reduction in 90K was detected already at 6 months (74.3 [56.0-104.1] μg/ml p = .001) and a further decline was observed at 12 months (49.3 [46.0-67.6] μg/ml p < .001).

CONCLUSION

Our study showed that 90K glycoprotein levels are increased in JIA children compared to healthy controls, suggesting a potential pathogenetic role in the JIA. Besides, 12 months of therapy with etanercept can reduce 90K levels.

Prognostic relevance of LGALS3BP in human colorectal carcinoma

Background

A previous report has shown that LGALS3BP (also known as 90K or Mac-2 BP) has antitumor activity in colorectal cancer (CRC) via suppression of Wnt signalling with a novel mechanism of ISGylation-dependent ubiquitination of β-catenin. The role of LGALS3BP in CRC prognosis was investigated.

Methods

The role of LGALS3BP on CRC progression and clinical prognosis was analyzed by combining cell cultures, in vitro assays, and immunohistochemistry.

Results

Silencing of LGALS3BP in HCT-116 human colon cancer cells resulted in enhanced β-catenin expression that was reversed by addition of human recombinant LGALS3BP. Moreover, intra-tumor delivery of LGALS3BP reduced tumor growth of xenografts originating from LGALS3BP-silenced HCT-116 cells. Finally, in a series of 196 CRC patients, LGALS3BP expression in tumor tissue associated with clinical outcome. Patients with high LGALS3BP expression had lower risk of relapse and a longer overall survival time than those with low LGALS3BP expression. Multivariate analyses confirmed LGALS3BP expression status as the only independent prognostic factor of survival.

Conclusions

These results provide evidence that low expression of LGALS3BP participates in malignant progression of CRC and implicates poor prognosis, highlighting its augmentation as a potential therapeutic approach.

Inhibition of tumor growth and angiogenesis by SP-2, an anti-lectin, galactoside-binding soluble 3 binding protein (LGALS3BP) antibody

Accumulating evidence indicates that serum and tissue levels of lectin, galactoside-binding soluble 3 binding protein (LGALS3BP), a secreted glycoprotein, are elevated in human cancers. Recently, we have identified LGALS3BP as a factor capable of stimulating angiogenesis of microvascular endothelial cells in vitro as well as in vivo. However, the potential therapeutic implications of LGALS3BP function blockade have not been explored yet. Here, we tested the ability of an anti-LGALS3BP mouse monoclonal antibody, SP-2, to antagonize LGALS3BP-induced angiogenesis and tumor growth. The antibody was found to inhibit endothelial cell tubulogenesis induced by either conditioned medium of breast cancer and melanoma cells or human recombinant LGALS3BP. In addition, SP-2 inhibited phosphorylation of FAK and its recruitment to membrane sites as well as AKT and ERK phosphorylation promoted by LGALS3BP. When used in vivo, the antibody restrained LGALS3BP-stimulated angiogenesis and growth of tumor xenografts. Furthermore, the combination of SP-2 and low-dose bevacizumab was more effective than either agent alone. Taken together, these results lead to consideration of SP-2 as a promising candidate for LGALS3BP-targeted therapy.

Proteomic analysis identifies a novel function for galectin-3 in the cell entry of parvovirus

Cellular factors associated with the parvovirus minute virus of mice (MVM) during infection are thought to play important roles in the MVM life cycle but only a few of these have been identified. Here we used a proteomic-based approach in order to identify host-binding partners of MVM. Using purified MVM as bait for immunoprecipitation assays, a total of 150 proteins were identified in MVM immunoprecipitates by quantitative liquid chromatography-tandem mass spectrometry. Galectin-3 was one of six proteins showing a statistically significant enrichment across replicates. Small interfering RNA depletion studies revealed an important role for galectin-3 in MVM endocytosis and infectivity in LA9 mouse fibroblast cells. Galectin-3-depleted cells were less susceptible to MVM infection than control cells and showed a significant reduction of MVM cellular uptake, but not of MVM binding to the cell surface. Our results indicate an important role for galectin-3 in the cellular uptake of MVM. We propose that galectin-3 facilitates the access of MVM to its receptor(s) at the plasma membrane and in this way promotes MVM endocytosis.

LGALS3BP, lectin galactoside-binding soluble 3 binding protein, induces vascular endothelial growth factor in human breast cancer cells and promotes angiogenesis

Elevated serum or tissue levels of lectin galactoside-binding soluble 3 binding protein (LGALS3BP) have been associated with short survival and development of metastasis in a variety of human cancers. However, the role of LGALS3BP, particularly in the context of tumor-host relationships, is still missing. Here, we show that LGALS3BP knockdown in MDA-MB-231 human breast cancer cells leads to a decreased adhesion to fibronectin, a reduced transendothelial migration and, more importantly, a reduced expression of vascular endothelial growth factor (VEGF). Production of VEGF, that was restored by exposure of silenced cells to recombinant LGALS3BP, required an intact PI3k/Akt signaling. Furthermore, we show that LGALS3BP was able to directly stimulate HUVEC tubulogenesis in a VEGF-independent, galectin-3-dependent manner. Immunohistochemical analysis of human breast cancer tissues revealed a correlation among LGALS3BP expression, VEGF expression, and blood vessel density. We propose that in addition to its prometastatic role, LGALS3BP secreted by breast cancer cells functions critically as a pro-angiogenic factor through a dual mechanism, i.e by induction of tumor VEGF and stimulation of endothelial cell tubulogenesis.

The conserved scavenger receptor cysteine-rich superfamily in therapy and diagnosis

The scavenger receptor cysteine-rich (SRCR) superfamily of soluble or membrane-bound protein receptors is characterized by the presence of one or several repeats of an ancient and highly conserved protein module, the SRCR domain. This superfamily (SRCR-SF) has been in constant and progressive expansion, now up to more than 30 members. The study of these members is attracting growing interest, which parallels that in innate immunity. No unifying function has been described to date for the SRCR domains, this being the result of the limited knowledge still available on the physiology of most members of the SRCR-SF, but also of the sequence versatility of the SRCR domains. Indeed, involvement of SRCR-SF members in quite different functions, such as pathogen recognition, modulation of the immune response, epithelial homeostasis, stem cell biology, and tumor development, have all been described. This has brought to us new information, unveiling the possibility that targeting or supplementing SRCR-SF proteins could result in diagnostic and/or therapeutic benefit for a number of physiologic and pathologic states. Recent research has provided structural and functional insight into these proteins, facilitating the development of means to modulate the activity of SRCR-SF members. Indeed, some of these approaches are already in use, paving the way for a more comprehensive use of SRCR-SF members in the clinic. The present review will illustrate some available evidence on the potential of well known and new members of the SRCR-SF in this regard.

Controlling cell surface dynamics and signaling: how CD82/KAI1 suppresses metastasis

The recent identification of metastasis suppressor genes, uniquely responsible for negatively controlling cancer metastasis, are providing inroads into the molecular machinery involved in metastasis. While the normal function of a few of these genes is known; the molecular events associated with their loss that promotes tumor metastasis is largely not understood. KAI1/CD82, whose loss is associated with a wide variety of metastatic cancers, belongs to the tetraspanin family. Despite intense scrutiny, many aspects of how CD82 specifically functions as a metastasis suppressor and its role in normal biology remain to be determined. This review will focus on the molecular events associated with CD82 loss, the potential impact on signaling pathways that regulate cellular processes associated with metastasis, and its relationship with other metastasis suppressor genes.

Synthetic lactulose amines: novel class of anticancer agents that induce tumor-cell apoptosis and inhibit galectin-mediated homotypic cell aggregation and endothelial cell morphogenesis

Galectins, a family of structurally related carbohydrate-binding proteins, contribute to different events associated with cancer biology, including apoptosis, homotypic cell aggregation, angiogenesis and tumor-immune escape. To interfere with galectin-carbohydrate interactions during tumor progression, a current challenge is the design of specific galectin inhibitors for therapeutic purposes. Here, we report the synthesis of three novel low molecular weight synthetic lactulose amines (SLA): (1) N-lactulose-octamethylenediamine (LDO), (2) N,N'-dilactulose-octamethylenediamine (D-LDO), and (3) N,N'-dilactulose-dodecamethylenediamine (D-LDD). These compounds showed a differential ability to inhibit binding of galectin-1 and/or galectin-3 to the highly glycosylated protein 90K in solid-phase assays. In addition, each compound demonstrated selective regulatory effects in different events linked to tumor progression including tumor-cell apoptosis, homotypic cell aggregation, and endothelial cell morphogenesis. Our results suggest that galectin inhibitors with subtle differences in their carbohydrate structures may be potentially used to specifically block different steps of tumor growth and metastasis.

Role of 90K protein in asthma and TH2-type cytokine expression

BACKGROUND

The 90K protein (mac-2 binding protein) is a member of the macrophage scavenger receptor cysteine-rich domain superfamily. Although systemic levels of 90K protein have been correlated with inflammation in many diseases, its role in asthma is unknown.

OBJECTIVE

To determine whether asthma is associated with changes in the local and systemic expression of 90K protein and whether 90K protein affects the TH2 cytokine profile that is a hallmark of asthma.

METHODS

The 90K protein levels were measured in the systemic circulation of 69 individuals with asthma and 68 controls and in the bronchoalveolar lavage fluid of 9 controls and 7 atopic asthmatic patients before and after segmental allergen challenge. The effects of 90K protein on interleukin 4 (IL-4), IL-5, IL-13, and IL-6 production at protein and transcriptional levels in cultured human peripheral blood mononuclear cells were determined.

RESULTS

Plasma concentrations of 90K protein were higher in asthmatic individuals vs controls (P = .002), were higher in the bronchoalveolar lavage fluid of asthmatic patients vs controls (P < .01), and increased after segmental allergen challenge in atopic asthmatic patients (P < .03). Increasing concentrations of 90K protein resulted in significantly reduced IL-4, IL-5, and IL-13 concentrations and increased IL-6 concentrations in the supernatants of cultured peripheral blood mononuclear cells (P < .05). Reverse transcriptase-polymerase chain reaction studies showed parallel changes in the transcription of these cytokines.

CONCLUSIONS

Local and systemic concentrations of 90K protein are increased in asthma. Its inhibitory effect on TH2 cytokine transcription suggests that increased 90K protein expression is an attempt to limit the ongoing inflammation in asthma.

CD8+αβ+T Cells That Lack Surface CD5 Antigen Expression Are a Major Lymphotactin (XCL1) Source in Peripheral Blood Lymphocytes

To better characterize the cellular source of lymphotactin (XCL1), we compared XCL1 expression in different lymphocyte subsets by real-time PCR. XCL1 was constitutively expressed in both PBMC and CD4(+) cells, but its expression was almost 2 log higher in CD8(+) cells. In vitro activation was associated with a substantial increase in XCL1 expression in both PBMC and CD8(+) cells, but not in CD4(+) lymphocytes. The preferential expression of XCL1 in CD8(+) cells was confirmed by measuring XCL1 production in culture supernatants, and a good correlation was found between figures obtained by real-time PCR and XCL1 contents. XCL1 expression was mostly confined to a CD3(+)CD8(+) subset not expressing CD5, where XCL1 expression equaled that shown by gammadelta(+) T cells. Compared with the CD5(+) counterpart, CD3(+)CD8(+)CD5(-) cells, which did not express CD5 following in vitro activation, showed preferential expression of the alphaalpha form of CD8 and a lower expression of molecules associated with a noncommitted/naive phenotype, such as CD62L. CD3(+)CD8(+)CD5(-) cells also expressed higher levels of the XCL1 receptor; in addition, although not differing from CD3(+)CD8(+)CD5(+) cells in terms of the expression of most alpha- and beta-chemokines, they showed higher expression of CCL3/macrophage inflammatory protein-1alpha. These data show that TCR alphabeta-expressing lymphocytes that lack CD5 expression are a major XCL1 source, and that the contribution to its synthesis by different TCR alphabeta-expressing T cell subsets, namely CD4(+) lymphocytes, is negligible. In addition, they point to the CD3(+)CD8(+)CD5(-) population as a particular T cell subset within the CD8(+) compartment, whose functional properties deserve further attention.

Serum 90K/MAC-2BP glycoprotein in patients with liver cirrhosis and hepatocellular carcinoma: a comparison with alpha-fetoprotein

Glycoprotein 90K/MAC-2BP is a member of the scavenger receptor cystein-rich protein superfamily, which is thought to be involved in immune surveillance, defending the body against pathogens and cancer. 90K serum levels are elevated in patients with cancer of various origins and in viral infections, such as human immunodeficiency virus and hepatitis C virus (HCV). Because in patients with HCV-related cirrhosis the incidence of hepatocellular carcinoma (HCC) is high, in the present paper we examined, by means of an enzyme-linked immunosorbent assay, the 90K serum levels in 103 patients with liver cirrhosis, and in 69 with HCC, and compared them to alpha-fetoprotein, the reference tumor marker for this neoplasm. Serum levels of 90K (cut-off 14 microg/ml) were elevated both in cirrhosis (39%) and HCC (46%) compared to controls (14.1 microg/ml vs. 10.6 microg/ml in cirrhosis, and 14.8 microg/ml vs. 9.1 microg/ml in HCC, p < or = 0.001). There was a significant association with the presence of anti-HCV antibodies. 90K was found to be a non-specific tumor marker which is complementary to alpha-fetoprotein on the basis of its probable different biological significance. In fact, 74% of HCC patients had at least one positive marker. Combined use of 90K and alpha-fetoprotein could improve the sensitivity of a single test in the diagnosis of HCC.

Adhesion to 90K (Mac-2 BP) as a mechanism for lymphoma drug resistance in vivo

A cell-adhesive protein of the human serum, 90K binds galactin-3, β1-integrins, collagens, and fibronectin, and it is of importance in cell-cell and cell–extracellular matrix adhesion. Serum 90K levels in 137 patients with lymphoma were measured by enzyme-linked immunosorbent assay. Compared with healthy controls, pretreatment serum 90K levels in patients with lymphoma were elevated (P &lt; .001). Of 97 patients who showed objective response to treatment, 20 (21%) had pretreatment 90K levels above the normal cutoff compared with 17 (53%) of 32 patients who did not respond (P = .002). When used as a plastic-immobilized substrate, 90K caused a significant reduction in chemotherapy-induced apoptosis of Jurkat T lymphoma cells. This finding could explain the lack of response in lymphoma patients with high 90K serum levels.

Adhesion to 90K (Mac-2 BP) as a mechanism for lymphoma drug resistance in vivo

A cell-adhesive protein of the human serum, 90K binds galactin-3, β1-integrins, collagens, and fibronectin, and it is of importance in cell-cell and cell–extracellular matrix adhesion. Serum 90K levels in 137 patients with lymphoma were measured by enzyme-linked immunosorbent assay. Compared with healthy controls, pretreatment serum 90K levels in patients with lymphoma were elevated (P < .001). Of 97 patients who showed objective response to treatment, 20 (21%) had pretreatment 90K levels above the normal cutoff compared with 17 (53%) of 32 patients who did not respond (P = .002). When used as a plastic-immobilized substrate, 90K caused a significant reduction in chemotherapy-induced apoptosis of Jurkat T lymphoma cells. This finding could explain the lack of response in lymphoma patients with high 90K serum levels.

Elevated levels of circulating immunostimulatory 90K in Henoch-Schoenlein purpura

In order to clarify the immunologic reaction present in Henoch-Schoenlein purpura (HSP), 20 children (11 boys and 9 girls; median age, 5.8 +/- 2.8 years) with HSP and 20 sex- and age-matched healthy children were studied. The 90K/Mac-2 BP serum concentrations were significantly higher in the patients than in the healthy controls (12.5 +/- 7.5 vs 4.5 +/- 2.7 micrograms/ml, respectively; P < 0.0001). 90K/Mac-2 BP values higher than the cutoff value were observed in 13 of 20 (65%) patient. The soluble intercellular adhesion molecule 1 concentrations were significantly higher in HSP patients than controls (P < 0.0001), with mean values of 1631 +/- 703 and 85 +/- 16 ng/ml, respectively. The 90K/Mac-2 BP serum levels were significantly correlated with soluble intercellular adhesion molecule 1 (r = 0.90, P < 0.0001). Although the underlying causes of these immunological abnormalities are unclear, these observations suggest that the 90K/Mac-2 BP protein may play a role in the immunological reactions involved in the development of HSP.