Regulation of galectin-1 expression by transforming growth factor beta1 in metastatic mammary adenocarcinoma cells: implications for tumor-immune escape

Galectin-1 Modulates the Fusogenic Activity of Placental Endogenous Retroviral Envelopes

Syncytin-1 and -2 are glycoproteins encoded by human endogenous retrovirus (hERV) that, through their fusogenic properties, are needed for the formation of the placental syncytiotrophoblast. Previous studies suggested that these proteins, in addition to the EnvP(b) envelope protein, are also involved in other cell fusion events. Since galectin-1 is a β-galactoside-binding protein associated with cytotrophoblast fusion during placental development, we previously tested its effect on Syncytin-mediated cell fusion and showed that this protein differently modulates the fusogenic potential of Syncytin-1 and -2. Herein, we were interested in comparing the impact of galectin-1 on hERV envelope proteins in different cellular contexts. Using a syncytium assay, we first demonstrated that galectin-1 increased the fusion of Syncytin-2- and EnvP(b)-expressing cells. We then tested the infectivity of Syncytin-1 and -2 vs. VSV-G-pseudotyped viruses toward Cos-7 and various human cell lines. In the presence of galectin-1, infection of Syncytin-2-pseudotyped viruses augmented for all cell lines. In contrast, the impact of galectin-1 on the infectivity of Syncytin-1-pseudotyped viruses varied, being cell- and dose-dependent. In this study, we report the functional associations between three hERV envelope proteins and galectin-1, which should provide information on the fusogenic activity of these proteins in the placenta and other biological and pathological processes.

Galectin-8, cytokines, and the storm

Galectin-8 (Gal-8) belongs to a family of animal lectins that modulate cell adhesion, cell proliferation, apoptosis, and immune responses. Recent studies have shown that mammalian Gal-8 induces in an autocrine and paracrine manner, the expression and secretion of cytokines and chemokines such as RANKL, IL-6, IL-1β, SDF-1, and MCP-1. This involves Gal-8 binding to receptor complexes that include MRC2/uPAR/LRP1, integrins, and CD44. Receptors ligation triggers FAK, ERK, Akt, and the JNK signaling pathways, leading to induction of NF-κB that promotes cytokine expression. Indeed, immune-competent Gal-8 knockout (KO) mice express systemic lower levels of cytokines and chemokines while the opposite is true for Gal-8 transgenic animals. Cytokine and chemokine secretion, induced by Gal-8, promotes the migration of cancer cells toward cells expressing this lectin. Accordingly, Gal-8 KO mice experience reduced tumor size and smaller and fewer metastatic lesions when injected with cancer cells. These observations suggest the existence of a ‘vicious cycle’ whereby Gal-8 expression and secretion promotes the secretion of cytokines and chemokines that further promote Gal-8 expression. This ‘vicious cycle’ could enhance the development of a ‘cytokine storm’ which is a key contributor to the poor prognosis of COVID-19 patients.

Galectin-1 and Galectin-3 Expression in Lesional Skin of Patients With Systemic Sclerosis-Association With Disease Severity

Galectin-1 (Gal-1) and galectin-3 (Gal-3) are carbohydrate-binding proteins involved in normal processes, autoimmunity, and cancer. Increased serum Gal-3 levels in scleroderma were associated with active disease, vasculopathy, and mortality.

OBJECTIVES

The aim of this study was to evaluate Gal-1 and Gal-3 expression in the lesional skin of patients with scleroderma regarding disease severity and organ involvement.

METHODS

A cross-sectional study was conducted on patients diagnosed as systemic sclerosis (SSc), after informed consent. Clinical and serological profiles were reviewed from medical records. Lesional skin biopsies were taken by losange incision from patients. Samples were analyzed by immunohistochemistry and compared with normal skin of a healthy patient. Parametric statistical analysis was done with Student t test and Pearson coefficient. Significance was established as p ≤ 0.05 with a 95% confidence interval.

RESULTS

Biopsies of 10 patients and a healthy control (9 female, 1 male) were analyzed. The mean age was 54.5 years (18-74 years). Four of 10 patients had diffuse, 4 had limited scleroderma, 1 had overlap syndrome, and 1 had sclerodermiform graft-versus-host disease. The mean fibroblasts count per field was 13.2 in scleroderma versus 7.2 in normal skin. The mean expression of Gal-1 in scleroderma fibroblasts was 13% (0%-56%) and 47.5% for Gal-3 (6.5%-95.5%); in normal skin, the mean expression was 91% (90%-95%) for Gal-1 and 97% (89%-100%) for Gal-3. A higher Gal-3 expression in scleroderma (within its lower expression compared with normal skin) was associated with pulmonary artery hypertension (p = 0.004) and to a higher modified Rodnan's skin score (p = 0.0003). In a similar manner, anti-centromere antibodies were associated with a higher Gal-1 expression in SSc skin fibroblasts (p = 0.04).

CONCLUSIONS

Gal-1 and Gal-3 had a lower expression in scleroderma lesional skin compared with a normal control. We found a significant correlation between a higher Gal-3 expression (within the lower ones compared with normal skin) in fibroblasts from SSc patients and severe disease (pulmonary hypertension and a higher modified Rodnan's skin score) compared with patients with lower expression of this protein. Similarly, the presence of anti-centromere antibodies was associated with a higher expression of Gal-1 within this group of patients.

Chemical metabolome assay by high-resolution Orbitrap mass spectrometry and assessment of associated antitumoral activity of Actinocephalus divaricatus

RATIONALE

Actinocephalus divaricatus (Eriocaulaceae) is an important source of income for rural communities as it is sold as an ornamental plant. To date, no investigation has been conducted concerning the chemical composition and biological studies of the aerial parts of A. divaricatus.

METHODS

The methanolic extract of the aerial parts of this species was chemically characterized. We applied an analytical dereplication approach based on Liquid Chromatography coupled to High-Resolution Orbitrap Mass Spectrometry in order to develop, identify and define rapidly the metabolite fingerprint of the aerial parts of A. divaricatus. Biological in vitro antitumor tests were undertaken using breast and lung cell lines of mice and humans.

RESULTS

High-Resolution Mass Spectrometry (HRMS) allowed the fast determination of 30 compounds, which comprised three different classes of compounds: naphthopyranones, flavonoids and saponins. Chromatographic fractionation of the crude methanolic extract validated these results, since it led to the isolation of compounds belonging to the aforementioned classes of compounds, including new acyl glycosylated flavonoids (6-hydroxy-7-methoxyquercetin-3-O-(2"-O-acetyl)-β-D-glucopyranoside and 6-hydroxy-7-methoxyquercetin-3-O-(6"-O-acetyl)-β-D-glucopyranoside), which were fully characterized by Nuclear Magnetic Resonance and Mass Spectrometry experiments, and a known triterpenic saponin (3-O-β-D-glucuronopyranosyl-30-norolean-12,20(29)-dien-28-O-β-D-glucopyranosyl ester). Biological assays indicated that the methanolic extract of the capitula exhibited the best in vitro cytotoxicity against MCF7 cells (human breast cancer).

CONCLUSIONS

The HRMS technique enabled us to identify several classes of compounds. In addition, saponins were identified for the first time in plants belonging to the Eriocaulaceae family. Thus, the essential contribution of this work lies in the new elements it brings to the taxonomic discussion which the Actinocephalus genus as a distinct genus of the Paepalanthus. The results obtained show that the methanolic extract of the capitula could be a promising source of bioactive fractions and/or compounds that may contribute towards breast cancer treatment.

Galectin-1 knockdown in carcinoma-associated fibroblasts inhibits migration and invasion of human MDA-MB-231 breast cancer cells by modulating MMP-9 expression

Carcinoma-associated fibroblasts (CAFs) play central roles in facilitating tumor progression and metastasis in breast cancer. Galectin-1 (Gal-1), a marker of CAFs, was previously reported to be associated with tumorigenesis and metastasis of various types of tumors. The aim of this study is to investigate the role of Gal-1 in CAF-mediated breast cancer metastasis and its underlying molecular mechanisms. Our results showed that CAFs isolated from human breast tumor tissues expressed higher level of Gal-1 compared with paired normal fibroblasts, and the conditioned medium (CM) of CAFs significantly induced the migration and invasion of human MDA-MB-231 breast cancer cells. Knockdown of Gal-1 in CAFs dramatically inhibited CAF-CM-induced cell migration and invasion, probably by inhibiting the expression of matrix metalloprotein 9 (MMP-9). Our findings demonstrate that Gal-1-regulated CAFs activation promotes breast cancer cell metastasis by upregulating MMP-9 expression, which indicated that Gal-1 in CAFs might be a potential novel target for breast cancer therapy.

Thiodigalactoside shows antitumour activity by beta-galactoside-binding protein and regulatory T cells inhibition in oral squamous cell carcinoma

OBJECTIVE

Thiodigalactoside (TDG), a synthetic inhibitor of β-galactoside-binding protein (β-GBP) suppresses tumour growth by inhibiting multiple cancer enhancing activities of β-GBP. Hence, we attempted to understand whether disruption of β-GBP functions and indirect inhibition of Treg cells by TDG affect the growth and establishment of oral cancer cells.

METHOD

The growth, morphology, cell cycle regulation, apoptosis induction and angiogenesis of oral cancer cell lines (SCC-4, SCC-9, SCC-25) via MACS-purified Treg cells were performed by MTT, propidium iodide (PI) staining, annexin-V-binding assay and ELISA respectively.

RESULTS

Treatment with β-GBP showed growth-promoting effects on Tregs and oral cancer cells. However, the treatment with its inhibitor TDG resulted in inhibition of Treg subsets and also decreased the frequency of IL10(+) and IL35(+) Tregs indicating its immunomodulatory effects. Additionally, TDG treatment significantly (P < 0.001) inhibited the growth of OSCC cells with a concomitant induction of apoptosis, cell cycle arrest and anti-angiogenesis.

CONCLUSION

It appears that TDG concurrently prevents many tumour-promoting effects of β-GBP in oral cancer cells possibly by Treg inhibition. This offers a preclinical proof of the concept that therapeutic targeting of β-GBP can overcome Treg -mediated tumour promotion and immunosuppression in oral cancer patients.

Galectin-1 Controls the Proliferation and Migration of Liver Sinusoidal Endothelial Cells and Their Interaction With Hepatocarcinoma Cells

Galectin-1 (Gal1), a β-galactoside-binding protein elevated in hepatocellular carcinoma (HCC), promotes epithelial-mesenchymal transition (EMT) and its expression correlates with HCC growth, invasiveness, and metastasis. During the early stages of HCC, transforming growth factor β1 (TGF-β1 ) acts as a tumor suppressor; however in advanced stages, HCC cells lose their cytostatic response to TGF-β1 and undergo EMT. Here, we investigated the role of Gal1 on liver endothelial cell biology, and the interplay between Gal1 and TGF-β1 in HCC progression. By Western blot and immunofluorescence, we analyzed Gal1 expression, secretion and localization in HepG2 and HuH-7 human HCC cells, and in SK-HEP-1 human liver sinusoidal endothelial cells (SECs). We used loss-of-function and gain-of-function experiments to down- or up-regulate Gal1 expression, respectively, in HepG2 cells. We cultured SK-HEP-1 cells with conditioned media from HCC cells secreting different levels of Gal1, and demonstrated that Gal1 derived from tumor hepatocytes induced its own expression in SECs. Colorimetric and scratch-wound assays revealed that secretion of Gal1 by HCC cells induced SEC proliferation and migration. Moreover, by fluorescence microscopy we demonstrated that Gal1 promoted glycan-dependent heterotypic adhesion of HepG2 cells to SK-HEP-1 SECs. Furthermore, TGF-β1 induced Gal1 expression and secretion by HCC cells, and promoted HepG2 cell adhesion to SK-HEP-1 SECs through a Gal1-dependent mechanism. Finally, Gal1 modulated HepG2 cell proliferation and sensitivity to TGF-β1 -induced growth inhibition. Our results suggest that Gal1 and TGF-β1 might function coordinately within the HCC microenvironment to regulate tumor growth, invasion, metastasis, and angiogenesis.

Intracellular galectins in cancer cells: potential new targets for therapy (Review)

Dysregulation of galectin expression is frequently observed in cancer tissues. Such an abnormal expression pattern often correlates with aggressiveness and relapse in many types of cancer. Because galectins have the ability to modulate functions that are important for cell survival, migration and metastasis, they also represent attractive targets for cancer therapy. This has been well-exploited for extracellular galectins, which bind glycoconjugates expressed on the surface of cancer cells. Although the existence of intracellular functions of galectins has been known for many years, an increasing number of studies indicate that these proteins can also alter tumor progression through their interaction with intracellular ligands. In fact, in some instances, the interactions of galectins with their intracellular ligands seem to occur independently of their carbohydrate recognition domain. Such findings call for a change in the basic assumptions, or paradigms, concerning the activity of galectins in cancer and may force us to revisit our strategies to develop galectin antagonists for the treatment of cancer.

Proliferation rate of stem cells derived from human dental pulp and identification of differentially expressed genes

Stem cells from human exfoliated deciduous teeth (SHED) and dental pulp stem cells (DPSCs) obtained from the dental pulp of human extracted tooth were cultured and characterized to confirm that these were mesenchymal stem cells. The proliferation rate was assessed using AlamarBlue® cell assay. The differentially expressed genes in SHED and DPSCs were identified using the GeneFishing™ technique. The proliferation rate of SHED (P < 0.05) was significantly higher than DPSCs while SHED had a lower multiplication rate and shorter population doubling time (0.01429, 60.57 h) than DPSCs (0.00286, 472.43 h). Two bands were highly expressed in SHED and three bands in DPSCs. Sequencing analysis showed these to be TIMP metallopeptidase inhibitor 1 (TIMP1), and ribosomal protein s8, (RPS8) in SHED and collagen, type I, alpha 1, (COL1A1), follistatin-like 1 (FSTL1), lectin, galactoside-binding, soluble, 1, (LGALS1) in DPSCs. TIMP1 is involved in degradation of the extracellular matrix, cell proliferation and anti-apoptotic function and RPS8 is involved as a rate-limiting factor in translational regulation; COL1A1 is involved in the resistance and elasticity of the tissues; FSTL1 is an autoantigen associated with rheumatoid arthritis; LGALS1 is involved in cell growth, differentiation, adhesion, RNA processing, apoptosis and malignant transformation. This, along with further protein expression analysis, holds promise in tissue engineering and regenerative medicine.

Pancreatic satellite cells derived galectin-1 increase the progression and less survival of pancreatic ductal adenocarcinoma

BACKGROUND

Galectin-1, a member of carbohydrate-binding proteins with a polyvalent function on tumor progression, was found strongly expressed in pancreatic satellite cells (PSCs), which partner in crime with cancer cells and promote the development of pancreatic ductal adenocarcinoma (PDAC). We evaluated the effects of PSCs derived Galectin-1 on the progression of PDAC, as well as the tumor establishment and development in mouse xenografts.

METHODS

The relationship between immunohistochemistry staining intensity of Galectin-1 and clinicopathologic variables were assessed in 66 PDAC tissues, 18 chronic pancreatitis tissues and 10 normal controls. The roles of PSCs isolated from PDAC and normal pancreas on the proliferative activity, MMP2 and MMP9 expression, and the invasion of CFPAC-1 in the co-cultured system, as well as on the tumor establishment and development in mouse xenografts by mixed implanting with CFPAC-1 subcutaneously were evaluated.

RESULTS

Galectin-1 expression was gradually increased from normal pancreas (negative), chronic pancreatitis (weak) to PDAC (strong), in which Galectin-1 expression was also increased from well, moderately to poorly differentiated PDAC. Galectin-1 staining intensity of pancreatic cancer tissue was associated with increase in tumor size, lymph node metastasis, perineural invasion and differentiation and UICC stage, and served as the independent prognostic indicator of poor survival of pancreatic cancer. In vitro and in vivo experiments indicated that TGF-β1 upregulated Galectin-1 expression in PSCs, which could further promotes the proliferative activity, MMP2 and MMP9 expression, and invasion of pancreatic cancer cells, as well as the tumor establishment and growth.

CONCLUSION

Galectin-1 expression in stromal cells of pancreatic cancer suggests that this protein plays a role in the promotion of cancer cells invasion and metastasis and provides a therapeutic target for the treatment of pancreatic cancer.

TGF-beta specifically enhances the metastatic attributes of murine lung adenocarcinoma: implications for human non-small cell lung cancer

Lung cancer is the most frequent and one of the most deadly cancer types and is classified into small cell lung cancer and non-small cell lung cancer (NSCLC). Transforming growth factor beta (TGFβ) regulates a wide array of cell functions and plays a major role in lung diseases, including NSCLC. TGFβ signals through the complex of TGFβ type I and type II receptors, triggering Smad and non-Smad signaling pathways such as PI3K/Akt and MEK1/ERK. We investigated the role of TGFβ1 on the progression of the murine lung adenocarcinoma cell line LP07. Furthermore, we undertook a retrospective study with tissue samples from stage I and II NSCLC patients to assess the clinical pathologic role and prognostic significance of TβRI expression. We demonstrated that although lung cancer cell monolayers responded to TGFβ1 anti-mitogenic effects and TGFβ1 pulse (24 h treatment) delayed tumor growth at primary site; a switch towards malignant progression upon TGFβ1 treatment was observed at the metastatic site. In our model, TGFβ1 modulated in vitro clonogenicity, protected against stress-induced apoptosis and increased adhesion, spreading, lung retention and metastatic outgrowth. PI3K and MEK1 signaling pathways were involved in TGFβ1-mediated metastasis stimulation. Several of these TGFβ responses were also observed in human NSCLC cell lines. In addition, we found that a higher expression of TβRI in human lung tumors is associated with poor patient's overall survival by univariate analysis, while multivariate analysis did not reach statistical significance. Although additional detailed analysis of the endogenous signaling in vivo and in vitro is needed, these studies may provide novel molecular targets for the treatment of lung cancer.

Targeting galectin-1 overcomes breast cancer-associated immunosuppression and prevents metastatic disease

Galectin-1 (Gal1), an evolutionarily conserved glycan-binding protein, contributes to the creation of an immunosuppressed microenvironment at sites of tumor growth. In spite of considerable progress in elucidating its role in tumor-immune escape, the mechanisms underlying the inhibitory functions of Gal1 remain obscure. Here, we investigated the contribution of tumor Gal1 to tumor growth, metastasis, and immunosuppression in breast cancer. We found that the frequency of Gal1(+) cells in human breast cancer biopsies correlated positively with tumor grade, while specimens from patients with benign hyperplasia showed negative or limited Gal1 staining. To examine the pathophysiologic relevance of Gal1 in breast cancer, we used the metastatic mouse mammary tumor 4T1, which expresses and secretes substantial amounts of Gal1. Silencing Gal1 expression in this model induced a marked reduction in both tumor growth and the number of lung metastases. This effect was abrogated when mice were inoculated with wild-type 4T1 tumor cells in their contralateral flank, suggesting involvement of a systemic modulation of the immune response. Gal1 attenuation in 4T1 cells also reduced the frequency of CD4(+)CD25(+) Foxp3(+) regulatory T (T(reg)) cells within the tumor, draining lymph nodes, spleen, and lung metastases. Further, it abrogated the immunosuppressive function of T(reg) cells and selectively lowered the expression of the T-cell regulatory molecule LAT (linker for activation of T cells) on these cells, disarming their suppressive activity. Taken together, our results offer a preclinical proof of concept that therapeutic targeting of Gal1 can overcome breast cancer-associated immunosuppression and can prevent metastatic disease.

Stromal galectin-1 expression is associated with long-term survival in resectable pancreatic ductal adenocarcinoma

The overall 5 year survival rate for pancreatic ductal adenocarcinoma (i.e., PDAC) is a dismal 5%, although patients that have undergone surgical resection have a somewhat better survival rate of up to 20%. Very long-term survivors of PDAC (defined as patients with ≥ 10 year survival following apparently curative resection), on the other hand, are considerably less frequent. The molecular characteristics of very long-term survivors (VLTS) are poorly understood, but might provide novel insights into prognostication for this disease. In this study, a panel of five VLTS and stage-matched short-term survivors (STS, defined as disease-specific mortality within 14 months of resection) were identified, and quantitative proteomics was applied to comparatively profile tumor tissues from both cohorts. Differentially expressed proteins were identified in cancers from VLTS vs. STS patients. Specifically, the expression of galectin-1 was 2-fold lower in VLTS compared with STS tumors. Validation studies were performed by immunohistochemistry (IHC) in two additional cohorts of resected PDAC, including: 1) an independent cohort of VLTS and 2) a panel of sporadic PDAC with a considerable range of overall survival following surgery. Immunolabeling analysis confirmed that significantly lower expression of stromal galectin-1 was associated with VLTS (p = 0.02) and also correlated with longer survival in sporadic, surgically-treated PDAC cases (hazard ratio = 4.9, p = 0.002). The results from this study provide new insights to better understand the role of galectin-1 in PDAC survival, and might be useful for rendering prognostic information, and developing more effective therapeutic strategies aimed at improving survival.

Galectin-1 promotes lung cancer progression and chemoresistance by upregulating p38 MAPK, ERK, and cyclooxygenase-2

PURPOSE

This study is aimed at investigating the role and novel molecular mechanisms of galectin-1 in lung cancer progression.

EXPERIMENTAL DESIGN

The role of galectin-1 in lung cancer progression was evaluated both in vitro and in vivo by short hairpin RNA (shRNA)-mediated knockdown of galectin-1 in lung adenocarcinoma cell lines. To explore novel molecular mechanisms underlying galectin-1-mediated tumor progression, we analyzed gene expression profiles and signaling pathways using reverse transcription PCR and Western blotting. A tissue microarray containing samples from patients with lung cancer was used to examine the expression of galectin-1 in lung cancer.

RESULTS

We found overexpression of galectin-1 in non-small cell lung cancer (NSCLC) cell lines. Suppression of endogenous galectin-1 in lung adenocarcinoma resulted in reduction of the cell migration, invasion, and anchorage-independent growth in vitro and tumor growth in mice. In particular, COX-2 was downregulated in galectin-1-knockdown cells. The decreased tumor invasion and anchorage-independent growth abilities were rescued after reexpression of COX-2 in galectin-1-knockdown cells. Furthermore, we found that TGF-β1 promoted COX-2 expression through galectin-1 interaction with Ras and subsequent activation of p38 mitogen-activated protein kinase (MAPK), extracellular signal-regulated kinase (ERK), and NF-κB pathway. Galectin-1 knockdown sensitized lung cancer cells to platinum-based chemotherapy (cisplatin). In addition, galectin-1 and COX-2 expression was correlated with the progression of lung adenocarcinoma, and high clinical relevance of both proteins was evidenced (n = 47).

CONCLUSIONS

p38 MAPK, ERK, and COX-2 activation are novel mediators for the galectin-1-promoted tumor progression and chemoresistance in lung cancer. Galectin-1 may be an innovative target for combined modality therapy for lung cancer.

Galectin-1 and immunotherapy for brain cancer

The prognosis of patients diagnosed with high-grade glioma continues to be dismal in spite of multimodal treatment. Active specific immunotherapy by means of dendritic cell vaccination is considered to be a new promising concept that aims at generating an anti-tumoral immune response. However, it is now widely accepted that the success of immunotherapeutic strategies to promote tumor regression will rely not only on enhancing the effector arm of the immune response but also on downregulation of the counteracting tolerogenic signals. In this article, we summarize evidence that galectin-1, an evolutionarily conserved glycan-binding protein that is abundantly expressed in high-grade glioma, is an important player in glioma-mediated immune escape.

Galectin inhibitory disaccharides promote tumour immunity in a breast cancer model

High level galectin-1 expression results in cancer cell evasion of the immune response, increased tumour survival and aggressive metastases. Using a galectin-1 polyclonal antibody, high levels of galectin-1 protein were shown to be expressed by breast cancer cells established from FVB/N MMTV-c-neu mice as well as by the B16F10 melanoma cell line. In mixed lymphocyte cultures using tumour cells as antigenic stimulators, addition of recombinant galectin-1 dose-dependently inhibited lymphocyte production. Disaccharides were identified that inhibited galectin-1 function and increased growth and activation of CD8(+) CTL's killing cancer cells. X-ray crystallographic structures of human galectin-1 in complex with inhibitory disaccharides revealed their mode of binding. Combining galectin-blocking carbohydrates as adjuvants with vaccine immunotherapy in vivo to promote immune responses significantly decreased tumour progression and improved the outcomes for tumour challenged mice. This is the first report showing that suitably selected galectin-1 blocking disaccharides will act as adjuvants promoting vaccine stimulated immune responses against tumours in vivo.

Suppression of renal fibrosis by galectin-1 in high glucose-treated renal epithelial cells

Diabetic nephropathy is the most common cause of chronic kidney disease. We investigated the ability of intracellular galectin-1 (Gal-1), a prototype of endogenous lectin, to prevent renal fibrosis by regulating cell signaling under a high glucose (HG) condition. We demonstrated that overexpression of Gal-1 reduces type I collagen (COL1) expression and transcription in human renal epithelial cells under HG conditions and transforming growth factor-β1 (TGF-β1) stimulation. Matrix metalloproteinase 1 (MMP1) is stimulated by Gal-1. HG conditions and TGF-β1 treatment augment expression and nuclear translocation of Gal-1. In contrast, targeted inhibition of Gal-1 expression reduces COL1 expression and increases MMP1 expression. The Smad3 signaling pathway is inhibited, whereas two mitogen-activated protein kinase (MAPK) pathways, p38 and extracellular signal-regulated kinase (ERK), are activated by Gal-1, indicating that Gal-1 regulates these signaling pathways in COL1 production. Using specific inhibitors of Smad3, ERK, and p38 MAPK, we showed that ERK MAPK activated by Gal-1 plays an inhibitory role in COL1 transcription and that activation of the p38 MAPK pathway by Gal-1 plays a negative role in MMP1 production. Taken together, two MAPK pathways are stimulated by increasing levels of Gal-1 in the HG condition, leading to suppression of COL1 expression and increase of MMP1 expression.

Mechanism of tumor cell-induced T-cell apoptosis mediated by galectin-1

Galectin-1 (Gal-1) has been implicated in tumor progression partly via the induction of T-cell apoptosis. However the mechanism of Gal-1 induced T-cell death was mostly studied using recombinant, soluble Gal-1 producing controversial results. To explore the true mechanism of Gal-1 and hence tumor cell-induced T-cell death, we applied co-cultures of tumor cells and T-cells thus avoiding artificial circumstances generated using recombinant protein. T-cells died when co-cultured with Gal-1-expressing but survived with Gal-1 non-expressing tumor cells. Removing tumor cell surface Gal-1 or knocking down Gal-1 expression resulted in diminution of T-cell apoptosis. Gal-1 transgenic or soluble Gal-1 treated HeLa cells became cytotoxic. Stimulation of apoptosis required interaction between the tumor and T-cells, presence of p56lck and ZAP70, decrease of mitochondrial membrane potential and caspase activation. Hence tumor cell-derived Gal-1 might efficiently contribute to tumor self-defense. Moreover this system resolves the discrepancies obtained using recombinant Gal-1 in T-cell apoptosis studies.

Conveying glycan information into T-cell homeostatic programs: a challenging role for galectin-1 in inflammatory and tumor microenvironments

The immune system has evolved sophisticated mechanisms composed of several checkpoints and fail-safe processes that enable it to orchestrate innate and adaptive immunity, while at the same time limiting aberrant or unfaithful T-cell function. These multiple regulatory pathways take place during the entire life-span of T cells including T-cell development, homing, activation, and differentiation. Galectin-1, an endogenous glycan-binding protein widely expressed at sites of inflammation and tumor growth, controls a diversity of immune cell processes, acting either extracellularly through specific binding to cell surface glycan structures or intracellularly through modulation of pathways that remain largely unexplored. In this review, we highlight the discoveries that have led to our current understanding of the role of galectin-1 in distinct immune cell process, particularly those associated with T-cell homeostasis. Also, we emphasize findings emerging from the study of experimental models of autoimmunity, chronic inflammation, fetomaternal tolerance, and tumor growth, which have provided fundamental insights into the critical role of galectin-1 and its specific saccharide ligands in immunoregulation. Challenges for the future will embrace the rational manipulation of galectin-1-glycan interactions both towards attenuating immune responses in autoimmune diseases, graft rejection, and recurrent fetal loss, while at the same overcoming immune tolerance in chronic infections and cancer.

Severe preeclampsia is characterized by increased placental expression of galectin-1

OBJECTIVE

Galectin-1 is a major anti-inflammatory protein expressed by the placenta and immune cells that can bias the character of inflammatory responses toward the Th2 type. Galectin-1 is expressed in immune privileged sites, it can facilitate immune tolerance and tumor immune escape, and it has been successfully used for the suppression of experimental autoimmune diseases as well as graft-versus-host disease in murine models. We propose that an abnormal immune response in some pregnancy complications may be associated with changes in placental expression of galectin-1. To test this hypothesis, we studied placental galectin-1 mRNA and protein expression and localization in women with preeclampsia (PE) and in those who delivered a small-for-gestational age (SGA) neonate.

STUDY DESIGN

This cross-sectional study included pregnant women matched for gestational age at delivery in the following groups: (1) severe PE (n = 10), (2) severe PE complicated with SGA (n = 10), (3) SGA without PE (n = 10), and (4) controls (n = 10). Galectin-1 mRNA and protein were localized in placentas by in situ hybridization and immunofluorescence microscopy. Galectin-1 mRNA expression was determined by quantitative real-time reverse transcription-polymerase chain reaction (RT-PCR), and galectin-1 protein content by Western blot. Non-parametric statistics were used for analysis.

RESULT

(1) In normal term placentas, galectin-1 mRNA or immunofluorescence signals were detected in the trophoblasts, villous stromal cells, Hofbauer cells, endothelial cells of the villous blood vessels, and the villous stroma. (2) Placental galectin-1 mRNA expression was significantly higher in severe PE (with or without SGA) than in controls (1.47-fold, p = 0.004; 1.44-fold, p = 0.003, respectively) and in SGA (1.68-fold, p = 0.001; 1.64-fold, p = 0.001, respectively). (3) Trophoblasts in placentas of patients with severe PE had the most intense galectin-1 immunostaining.

CONCLUSIONS

(1) We report for the first time the placental expression and localization of galectin-1 mRNA and demonstrate that the protein is abundantly present in third trimester human placentas. (2) Placental galectin-1 expression is higher in severe PE than in normal pregnancy regardless of the presence of SGA. (3) However, it is not altered in SGA without PE. We propose that the increased placental expression of galectin-1 in patients with severe PE may represent a fetal response to an exaggerated systemic maternal inflammation; thus, galectin-1 may be implicated in maternal-fetal immune tolerance in humans.

AP1-dependent galectin-1 expression delineates classical hodgkin and anaplastic large cell lymphomas from other lymphoid malignancies with shared molecular features

PURPOSE

Galectin-1 (Gal1) is an immunomodulatory glycan-binding protein regulated by an AP1-dependent enhancer in Hodgkin Reed-Sternberg cells. We recently found that Reed-Sternberg cell Gal1 promotes the immunosuppressive T-helper 2/T-regulatory cell-skewed microenvironment in classical Hodgkin lymphoma (cHL). We sought to investigate whether the coordinate expression of activated AP1 pathway components and Gal1 serves as a diagnostic signature of cHL. In addition, because there are common signaling and survival pathways in cHL and additional non-Hodgkin lymphomas, we also evaluated whether the AP1/Gal1 signature is shared by other molecularly or morphologically related lymphomas.

EXPERIMENTAL DESIGN

We evaluated 225 cases of primary cHL and non-Hodgkin lymphoma for evidence of a functional AP1/Gal1 signature by immunohistochemical techniques.

RESULTS

Gal1 is selectively expressed by malignant Reed-Sternberg cells in >90% of primary cHLs, and Gal1 expression is concordant with the activated AP1 component, c-Jun. In contrast, diffuse large B-cell lymphoma, primary mediastinal large B-cell lymphoma, and another Hodgkin-related entity, nodular lymphocyte-predominant Hodgkin lymphoma, do not express Gal1. However, anaplastic large cell lymphoma (ALCL), consistently expresses both Gal1 and its transcriptional regulator, c-Jun. The presence of activated c-Jun, indicative of functional AP1 activity, was confirmed by phospho-c-Jun immunostaining in cHL and ALCL.

CONCLUSIONS

These findings establish a functional AP1 signature that includes Gal1 expression in cHL and ALCL and suggests a common mechanism for tumor immunotolerance in these diseases. In addition, the combination of Gal1 and c-Jun serve as diagnostic biomarkers that delineate cHL and ALCL from other lymphomas with shared morphologic and/or molecular features.

Dynamic cross-talk between tumor and immune cells in orchestrating the immunosuppressive network at the tumor microenvironment

Accumulating evidence indicates that a dynamic cross-talk between tumors and the immune system can regulate tumor growth and metastasis. Increased understanding of the biochemical nature of tumor antigens and the molecular mechanisms responsible for innate and adaptive immune cell activation has revolutionized the fields of tumor immunology and immunotherapy. Both the protective effects of the immune system against tumor cells (immunosurveillance) and the evasion of tumor cells from immune attack (tumor-immune escape) have led to the concept of cancer immunoediting, a proposal which infers that a bidirectional interaction between tumor and inflammatory/regulatory cells is ultimately responsible for orchestrating the immunosuppressive network at the tumor site. In this context, a major challenge is the potentiation or redirection of tumor antigen-specific immune responses. The success in reaching this goal is highly dependent on an improved understanding of the interactions and mechanisms operating during the different phases of the cancer immunoediting process. In this review, we discuss the multiple defense and counterattack strategies that tumors have devised in order to evade immune attack and to thwart the effectiveness of several immunotherapeutic approaches.

Galectin-1 mediated suppression of Epstein-Barr virus specific T-cell immunity in classic Hodgkin lymphoma

In Hodgkin lymphoma (HL), the malignant Hodgkin Reed-Sternberg cells interact with the host microenvironment to create an immunosuppressive network that protects the lymphoma from immune attack. These mechanisms are not fully understood. We examined the role of the immunomodulatory protein galectin-1 (Gal-1) on Epstein-Barr virus-specific CD8(+) T cell responses in HL. Initial studies indicated Gal-1 expression in all in vitro established Hodgkin Reed-Sternberg cell lines. In situ analysis revealed Gal-1 expression in 26 of 42 classic HL, whereas Gal-1 was uniformly negative in nodular lymphocyte predominant HL. Gal-1(hi) expression was associated with male gender, older patients, reduced CD8(+) T cell infiltration at the tumor site, and most importantly, an impaired latent membrane protein 1 and 2-specific CD8(+) T-cell responses. In vitro exposure to recombinant Gal-1 inhibited proliferation and interferon-gamma expression by Epstein-Barr virus-specific T cells. These observations provide an important link between the Gal-1-mediated immunomodulatory networks and loss of antigen-specific T-cell function in classic HL.