Autocrine galectin-1 promotes collective cell migration of squamous cell carcinoma cells through up-regulation of distinct integrins

Galectins in epithelial-mesenchymal transition: roles and mechanisms contributing to tissue repair, fibrosis and cancer metastasis

Galectins are soluble glycan-binding proteins that interact with a wide range of glycoproteins and glycolipids and modulate a broad spectrum of physiological and pathological processes. The expression and subcellular localization of different galectins vary among tissues and cell types and change during processes of tissue repair, fibrosis and cancer where epithelial cells loss differentiation while acquiring migratory mesenchymal phenotypes. The epithelial-mesenchymal transition (EMT) that occurs in the context of these processes can include modifications of glycosylation patterns of glycolipids and glycoproteins affecting their interactions with galectins. Moreover, overexpression of certain galectins has been involved in the development and different outcomes of EMT. This review focuses on the roles and mechanisms of Galectin-1 (Gal-1), Gal-3, Gal-4, Gal-7 and Gal-8, which have been involved in physiologic and pathogenic EMT contexts.

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.

Chemical inhibition of LSD1 leads to epithelial to mesenchymal transition in vitro of an oral squamous cell carcinoma OM-1 cell line via release from LSD1-dependent suppression of ZEB1

The epigenetic regulation for gene expression determines cell plasticity. Oral squamous cell carcinoma (SCC) exhibits bidirectional cell plasticity, i.e. epithelial differentiation and epithelial to mesenchymal transition (EMT). The epigenetic regulator LSD1 is a histone H3-specific demethylase to which chemical inhibitors for its activity had been developed as an anti-cancer therapeutics. The bidirectional plasticity of the oral SCC cell line OM-1 had been characterized, but it remained unclear how chemical LSD1 inhibitors affect cell plasticity. Here we reported an adverse effect against cancer therapeutics, which was EMT induction in vitro by the chemical LSD1 inhibitor. The LSD1 inhibitor caused EMT-TF ZEB1 in OM-1 to undergo EMT. Furthermore, an additional EMT-TF Snail-dependent partial EMT phenotype in OM-1 progressed to complete EMT in conjunction with LSD1 inhibitor-dependent ZEB1 induction. The promotor activity of ZEB1 was up-regulated under LSD1 inhibition. The regulatory chromatin regions of ZEB1 accumulated histone H3 methylation under the chemical inhibition of LSD1. The LSD1 inhibitor also upregulates epithelial gene expression in vitro; however, the bidirectional effect of LSD1 inhibitor should be considered in cancer therapeutics.

Dexamethasone resets stable association of nuclear Snail with LSD1 concomitant with transition from EMT to partial EMT

Cancer cells utilize epithelial to mesenchymal transition (EMT) during invasion and metastasis. This program has intermediate cell states with retained epithelial and gained mesenchymal features together, referred to as partial EMT. Histone demethylase LSD1 forms a complex with the EMT master transcription factor Snail to modify histone marks and regulate target gene expression. However, little is known about the formation of this complex during the Snail-dependent transition between partial EMT and EMT. Here we visualized the nuclear complex of Snail and LSD1 as foci signals using proximity ligation assay. We demonstrated that the nuclear foci numbers varied with the transition of exogenous Snail-dependent partial EMT to EMT. Furthermore, we found that long exposure to dexamethasone could revert exogenous Snail-dependent EMT to partial EMT. In this reversion, the nuclear foci numbers also returned to previous levels. Therefore, we concluded that Snail might select partial EMT or EMT by altering its association with LSD1.

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Nuclear complexes of Snail was visualized by PLA.

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Exogenous Snai1 differently induced pEMT and EMT in OM-1.

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Dexamethasone reverted Snail-induced EMT to pEMT.

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Nuclei showed distinct foci numbers of Snail/LSD1 and Snail/methylated H3 in EMT and pEMT.

Partial EMT in Squamous Cell Carcinoma: A Snapshot

In the process of cancer EMT, some subgroups of cancer cells simultaneously exhibit both mesenchymal and epithelial characteristics, a phenomenon termed partial EMT (pEMT). pEMT is a plastic state in which cells coexpress epithelial and mesenchymal markers. In squamous cell carcinoma (SCC), pEMT is regulated, and the phenotype is maintained via the HIPPO pathway, NOTCH pathway and TGF-β pathways and by microRNAs, lncRNAs and the cancer microenvironment (CME); thus, SCC exhibits aggressive tumorigenic properties and high stemness, which leads collective migration and therapy resistance. Few studies have reported therapeutic interventions to address cells that have undergone pEMT, and this approach may be an effective way to inhibit the plasticity, drug resistance and metastatic potential of SCC.

Glycobiology of the Epithelial to Mesenchymal Transition

Glycosylation consists in the covalent, enzyme mediated, attachment of sugar chains to proteins and lipids. A large proportion of membrane and secreted proteins are indeed glycoproteins, while glycolipids are fundamental component of cell membranes. The biosynthesis of sugar chains is mediated by glycosyltransferases, whose level of expression represents a major factor of regulation of the glycosylation process. In cancer, glycosylation undergoes profound changes, which often contribute to invasion and metastasis. Epithelial to mesenchymal transition (EMT) is a key step in metastasis formation and is intimately associated with glycosylation changes. Numerous carbohydrate structures undergo up- or down-regulation during EMT and often regulate the process. In this review, we will discuss the relationship with EMT of the N-glycans, of the different types of O-glycans, including the classical mucin-type, O-GlcNAc, O-linked fucose, O-linked mannose and of glycolipids. Finally, we will discuss the role in EMT of galectins, a major class of mammalian galactoside-binding lectins. While the expression of specific carbohydrate structures can be used as a marker of EMT and of the propensity to migrate, the manipulation of the glycosylation machinery offers new perspectives for cancer treatment through inhibition of EMT.

The squamous cell carcinoma cell line OM-1 retains both p75-dependent stratified epithelial progenitor potential and cancer stem cell properties

The low-affinity nerve growth factor receptor p75 is a stratified epithelial stem/progenitor marker of human epithelia. We found OM-1, a human squamous cell carcinoma (SCC) cell line, showed distinct cells with p75 cluster, especially located at the center of a growing colony in a monolayer culture. A cell with p75 cluster was surrounded by cytokeratin 14- and cytokeratin 13-expressing cells that settled at the outer margin of the colony. OM-1 cells were also capable of forming tumor spheres in a cell suspension culture, an ability which was attenuated by the inhibition of p75-signaling. Intriguingly, we also found a p75-negative cell population from a growing culture of OM-1 that re-committed to become p75-clustering cells. These results indicated the possibility that SCC with epithelial multi-layering capacity can exploit the p75-dependent stratified epithelial progenitor property for the cancer stemness.

Plasticity of cancer cell invasion: Patterns and mechanisms

Cancer cell migration and invasion are integral components of metastatic disease, which is the major cause of death in cancer patients. Cancer cells can disseminate and migrate via several alternative mechanisms including amoeboid cell migration, mesenchymal cell migration, and collective cell migration. These diverse movement strategies display certain specific and distinct hallmarks in cell-cell junctions, actin cytoskeleton, matrix adhesion, and protease activity. During tumor progression, cells pass through complex microenvironments and adapt their migration strategies by reversible mesenchymal-amoeboid and individual-collective transitions. This plasticity in motility patterns enables cancer cells disseminate further and thus limit the efficiency of anti-metastasis therapies. In this review, we discuss the modes and mechanisms of cancer cell migration and focus on the plasticity of tumor cell movement as well as potential emerging therapeutic options for reducing cancer cell invasion.

The Emerging Role of Galectins and O-GlcNAc Homeostasis in Processes of Cellular Differentiation

Galectins are a family of soluble β-galactoside-binding proteins with diverse glycan-dependent and glycan-independent functions outside and inside the cell. Human cells express twelve out of sixteen recognized mammalian galectin genes and their expression profiles are very different between cell types and tissues. In this review, we summarize the current knowledge on the changes in the expression of individual galectins at mRNA and protein levels in different types of differentiating cells and the effects of recombinant galectins on cellular differentiation. A new model of galectin regulation is proposed considering the change in O-GlcNAc homeostasis between progenitor/stem cells and mature differentiated cells. The recognition of galectins as regulatory factors controlling cell differentiation and self-renewal is essential for developmental and cancer biology to develop innovative strategies for prevention and targeted treatment of proliferative diseases, tissue regeneration, and stem-cell therapy.

CHIP-mediated ubiquitination of Galectin-1 predicts colorectal cancer prognosis

CHIP and Galectin-1 are associated with the development of metastasis in cancer. However, the precise roles of CHIP or Gal1 in colorectal cancer are uncertain. Here, our study explored the relationship and clinical significance of CHIP or Gal1 in CRC. CHIP or Gal1 expression was significantly decreased or up-regulated in CRC compared with adjacent noncancerous tissues by immunohistochemistry on a CRC tissue microarray, respectively. Low CHIP or high Gal1 expression significantly correlated with clinicopathological characteristics in patients, as well as with shorter overall survival. Multivariate Cox regression analysis revealed that CHIP or Gal1 expression was an independent prognostic factor for CRC patients. Moreover, CHIP associated with Gal1 has a synergistic effect on the prediction of CRC prognosis. In vitro and vivo, high CHIP or low Gal1 expression inhibit CRC growth or metastasis. Our results found that CHIP could degradate Gal1 by ubiquitination. In summary, CHIP could inhibit CRC growth or metastasis through promoting Gal1 ubiquitination and degradation by proteasome. CHIP and Gal1 expressions are novel candidate prognostic markers in CRC. A combined effect of CHIP and Gal1 as efficient prognostic indicators was found for the first time.

Galectin-8 induces partial epithelial-mesenchymal transition with invasive tumorigenic capabilities involving a FAK/EGFR/proteasome pathway in Madin-Darby canine kidney cells

Epithelial cells can acquire invasive and tumorigenic capabilities through epithelial–mesenchymal-transition (EMT). The glycan-binding protein galectin-8 (Gal-8) activates selective β1-integrins involved in EMT and is overexpressed by certain carcinomas. Here we show that Gal-8 overexpression or exogenous addition promotes proliferation, migration, and invasion in nontumoral Madin–Darby canine kidney (MDCK) cells, involving focal-adhesion kinase (FAK)-mediated transactivation of the epidermal growth factor receptor (EGFR), likely triggered by α5β1integrin binding. Under subconfluent conditions, Gal-8–overexpressing MDCK cells (MDCK-Gal-8^H) display hallmarks of EMT, including decreased E-cadherin and up-regulated expression of vimentin, fibronectin, and Snail, as well as increased β-catenin activity. Changes related to migration/invasion included higher expression of α5β1 integrin, extracellular matrix-degrading MMP13 and urokinase plasminogen activator/urokinase plasminogen activator receptor (uPA/uPAR) protease systems. Gal-8–stimulated FAK/EGFR pathway leads to proteasome overactivity characteristic of cancer cells. Yet MDCK-Gal-8^H cells still develop apical/basolateral polarity reverting EMT markers and proteasome activity under confluence. This is due to the opposite segregation of Gal-8 secretion (apical) and β1-integrins distribution (basolateral). Strikingly, MDCK-Gal-8^H cells acquired tumorigenic potential, as reflected in anchorage-independent growth in soft agar and tumor generation in immunodeficient NSG mice. Therefore, Gal-8 can promote oncogenic-like transformation of epithelial cells through partial and reversible EMT, accompanied by higher proliferation, migration/invasion, and tumorigenic properties.

Galectins and Carcinogenesis: Their Role in Head and Neck Carcinomas and Thyroid Carcinomas

Head and neck cancers are among the most frequently occurring cancers worldwide. Of the molecular drivers described for these tumors, galectins play an important role via their interaction with several intracellular pathways. In this review, we will detail and discuss this role with specific reference to galectins-1, -3, and -7 in angiogenesis, cell proliferation, and invasion as well as in cell transformation and cancer progression. Furthermore, we will evaluate the prognostic value of galectin expression in head and neck cancers including those with oral cavity, salivary gland, and nasopharyngeal pathologies. In addition, we will discuss the involvement of these galectins in thyroid cancers where their altered expression is proposed as a new diagnostic biomarker.

Inhibition of AURKA kinase activity suppresses collective invasion in a microfluidic cell culture platform

Tumor local invasion is the first step of metastasis cascade which remains the key obstacle for cancer therapy. Collective cell migration plays a critical role in tumor invading into surrounding tissues. In vitro assays fail to assess collective invasion in a real time manner. Herein we aim to develop a three-dimensional (3D) microfluidic cell invasion model to determine the dynamic process. In this model, collective invasion of breast cancer cells is induced by the concentration gradient of fetal bovine serum. We find that breast cancer cells adopt a collective movement rather than a random manner when the cells invade into extracellular matrix. The leading cells in the collective movement exhibit an increased expression of an Aurora kinase family protein - AURKA compared with the follower cells. Inhibition of AURKA kinase activity by VX680 or AKI603 significantly reduces the phosphorylation of ERK1/2 (Thr202/Tyr204) and collective cohort formation. Together, our study illustrates that AURKA acts as a potential therapeutic target for suppressing the process of tumor collective invasion. The 3D microfluidic cell invasion model is a reliable, measurable and dynamic platform for exploring potential drugs to inhibit tumor collective invasion.

TLR4-mediated galectin-1 production triggers epithelial-mesenchymal transition in colon cancer cells through ADAM10- and ADAM17-associated lactate production

Toll-like receptor 4 (TLR4) activation is a key contributor to the carcinogenesis of colon cancer. Overexpression of galectin-1 (Gal-1) also correlates with increased invasive activity of colorectal cancer. Lactate production is a critical predictive factor of risk of metastasis, but the functional relationship between intracellular lactate and Gal-1 expression in TLR4-activated colon cancer remains unknown. In this study, we investigated the underlying mechanism and role of Gal-1 in metastasis and invasion of colorectal cancer (CRC) cells after TLR4 stimulation. Exposure to the TLR4 ligand lipopolysaccharide (LPS) increased expression of Gal-1, induced EMT-related cytokines, triggered the activation of glycolysis-related enzymes, and promoted lactate production. Gene silencing of TLR4 and Gal-1 in CRC cells inhibited lactate-mediated epithelial-mesenchymal transition (EMT) after TLR4 stimulation. Gal-1-mediated activation of a disintegrin and metalloproteinase 10 (ADAM10) and ADAM 17 increased the invasion activity and expression of mesenchymal characteristics in LPS-activated CRC cells. Conversely, inhibition of ADAM10 or ADAM17 effectively blocked the generation of lactate and the migration capacity of LPS-treated CRC cells. Thus, the TLR4/Gal-1 signaling pathway regulates lactate-mediated EMT processes through the activation of ADAM10 and ADAM17 in CRC cells.

Nuclear repartitioning of galectin-1 by an extracellular glycan switch regulates mammary morphogenesis

Branching morphogenesis in the mammary gland is achieved by the migration of epithelial cells through a microenvironment consisting of stromal cells and extracellular matrix (ECM). Here we show that galectin-1 (Gal-1), an endogenous lectin that recognizes glycans bearing N-acetyllactosamine (LacNAc) epitopes, induces branching migration of mammary epithelia in vivo, ex vivo, and in 3D organotypic cultures. Surprisingly, Gal-1's effects on mammary patterning were independent of its glycan-binding ability and instead required localization within the nuclei of mammary epithelia. Nuclear translocation of Gal-1, in turn, was regulated by discrete cell-surface glycans restricted to the front of the mammary end buds. Specifically, α2,6-sialylation of terminal LacNAc residues in the end buds masked Gal-1 ligands, thereby liberating the protein for nuclear translocation. Within mammary epithelia, Gal-1 localized within nuclear Gemini bodies and drove epithelial invasiveness. Conversely, unsialylated LacNAc glycans, enriched in the epithelial ducts, sequestered Gal-1 in the extracellular environment, ultimately attenuating invasive potential. We also found that malignant breast cells possess higher levels of nuclear Gal-1 and α2,6-SA and lower levels of LacNAc than nonmalignant cells in culture and in vivo and that nuclear localization of Gal-1 promotes a transformed phenotype. Our findings suggest that differential glycosylation at the level of tissue microanatomy regulates the nuclear function of Gal-1 in the context of mammary gland morphogenesis and in cancer progression.

Sulforaphane-cysteine suppresses invasion via downregulation of galectin-1 in human prostate cancer DU145 and PC3 cells

Our previous study showed that sulforaphane (SFN) inhibits invasion in human prostate cancer DU145 cells; however, the underlying mechanisms were not profoundly investigated. In the present study, we found that sulforaphane-cysteine (SFN-Cys), as a metabolite of SFN, inhibits invasion and possesses a novel mechanism in prostate cancer DU145 and PC3 cells. The scratch and Transwell assays showed that SFN-Cys (15 µM) inhibited both migration and invasion, with cell morphological changes, such as cell shrinkage and pseudopodia shortening. The cell proliferation (MTS) assay indicated that cell viability was markedly suppressed with increasing concentrations of SFN‑Cys. Furthermore, the Transwell assay showed that inhibition of SFN‑Cys‑triggered invasion was tightly linked to the sustained extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation. Western blot analysis revealed that SFN-Cys downregulated galectin-1 protein, an invasion‑related protein, and that the galectin‑1 reduction could be blocked by ERK1/2 inhibitor PD98059 (25 µM). Moreover, immunofluorescence staining showed that the expression level of galectin-1 protein was significantly reduced in the cells treated with SFN‑Cys. Hence, SFN‑Cys‑inhibited invasion resulted from the sustained ERK1/2 phosphorylation and ERK1/2‑triggered galectin-1 downregulation, suggesting that galectin-1 is a new SFN-Cys target inhibiting invasion apart from ERK1/2, in the treatment of prostate cancer.

Osteoactivin Promotes Migration of Oral Squamous Cell Carcinomas

Nearly 50% of patients with oral squamous cell carcinoma (OSCC) die of metastases or locoregional recurrence. Metastasis is mediated by cancer cell adhesion, migration, and invasion. Osteoactivin (OA) overexpression plays a role in metastases in several malignancies. The aims were to determine how integrin interactions modulate OA-induced OSCC cell migration; and to investigate OA effects on cell survival and proliferation. We confirmed OA mRNA and protein overexpression in OSCC cell lines. We assessed OA's interactions with integrins using adhesion inhibition assays, fluorescent immunocytochemistry and co-immunoprecipitation. We investigated OA-mediated activation of mitogen-activated protein kinases (MAPKs) and cell survival. Integrin inhibition effects on OA-mediated cell migration were determined. We assessed effects of OA knock-down on cell migration and proliferation. OA is overexpressed in OSCC cell lines, and serves as a migration-promoting adhesion molecule. OA co-localized with integrin subunits, and co-immunoprecipitated with the subunits. Integrin blocking antibodies, especially those directed against the β1 subunit, inhibited cell adhesion (P = 0.03 for SCC15 cells). Adhesion to OA activated MAPKs in UMSCC14a cells and OA treatment promoted survival of SCC15 cells. Integrin-neutralizing antibodies enhanced cell migration with OA in the extracellular matrix. OA knock-down resulted in decreased proliferation of SCC15 and SCC25 cells, but did not inhibit cell migration. OA in the extracellular matrix promotes OSCC cell adhesion and migration, and may be a novel target in the prevention of HNSCC spread. J. Cell. Physiol. 231: 1761-1770, 2016. © 2015 Wiley Periodicals, Inc.

Rho GTPases in collective cell migration

The family of Rho GTPases are intracellular signal transducers that link cell surface signals to multiple intracellular responses. They are best known for their role in regulating actin dynamics required for cell migration, but in addition control cell-cell adhesion, polarization, vesicle trafficking, and the cell cycle. The roles of Rho GTPases in single mesenchymal cell migration are well established and rely on Cdc42- and Rac-dependent cell protrusion of a leading edge, coupled to Rho-dependent contractility required to move the cell body forward. In cells migrating collectively, cell-cell junctions are maintained, and migrating leader cells are mechanically coupled to, and coordinate, migration with follower cells. Recent evidence suggests that Rho GTPases provide multifunctional input to collective cell polarization, cell-cell interaction, and migration. Here, we discuss the role of Rho GTPases in initiating and maintaining front-rear, apical-basal cell polarization, mechanotransduction, and cell-cell junction stability between leader and follower cells, and how these roles are integrated in collective migration. Thereby, spatiotemporal fine-tuning of Rho GTPases within the same cell and among cells in the cell group are crucial in controlling potentially conflicting, divergent cell adhesion and cytoskeletal functions to achieve supracellular coordination and mechanocoupling.

Galectins in epithelial functions

Galectins are a family of animal lectins comprising 15 members in vertebrates. These proteins are involved in many biological processes including epithelial homeostasis and tumor progression by displaying intracellular and extracellular activities. Hence Galectins can be found either in the cytoplasm or the nucleus, associated with membranes or in the extracellular matrix. Current studies aim at understanding the roles of Galectins in cell-cell and cell-matrix adhesion, cellular polarity and motility. This review discusses recent progress in defining the specificities and mechanisms of action of Galectins as cell regulators in epithelial cells. Physiological, cellular and molecular aspects of Galectin specificities will be treated successively.