Everolimus exerts anticancer effects through inhibiting the interaction of matrix metalloproteinase-7 with syndecan-2 in colon cancer cells.

Previous work showed that matrix metalloproteinase-7 (MMP-7) regulates colon cancer activities through an interaction with syndecan-2 (SDC-2) and SDC-2-derived peptide that disrupts this interaction and exhibits anticancer activity in colon cancer. Here, to identify potential anticancer agents, a library of 1,379 Food and Drug Administration (FDA)-approved drugs that interact with the MMP-7 prodomain were virtually screened by protein-ligand docking score analysis using the GalaxyDock3 program. Among five candidates selected based on their structures and total energy values for interacting with the MMP-7 prodomain, the known mechanistic target of rapamycin kinase (mTOR) inhibitor, everolimus, showed the highest binding affinity and the strongest ability to disrupt the interaction of the MMP-7 prodomain with the SDC-2 extracellular domain in vitro. Everolimus treatment of the HCT116 human colon cancer cell line did not affect the mRNA expression levels of MMP-7 and SDC-2 but reduced the adhesion of cells to MMP-7 prodomain-coated plates and the cell-surface localization of MMP-7. Thus, everolimus appears to inhibit the interaction between MMP-7 and SDC-2. Everolimus treatment of HCT116 cells also reduced their gelatin-degradation activity and anticancer activities, including colony formation. Interestingly, cells treated with sirolimus, another mTOR inhibitor, triggered less gelatin-degradation activity, suggesting that this inhibitory effect of everolimus was not due to inhibition of the mTOR pathway. Consistently, everolimus inhibited the colony-forming ability of mTOR-resistant HT29 cells. Together, these data suggest that, in addition to inhibiting mTOR signaling, everolimus exerts anticancer activity by interfering with the interaction of MMP-7 and SDC-2, and could be a useful therapeutic anticancer drug for colon cancer.NEW & NOTEWORTHY The utility of cancer therapeutics targeting the proteolytic activities of MMPs is limited because MMPs are widely distributed throughout the body and involved in many different aspects of cell functions. This work specifically targets the activation of MMP-7 through its interaction with syndecan-2. Notably, everolimus, a known mTOR inhibitor, blocked this interaction, demonstrating a novel role for everolimus in inhibiting mTOR signaling and impairing the interaction of MMP-7 with syndecan-2 in colon cancer.

Substituted Syndecan-2-Derived Mimetic Peptides Show Improved Antitumor Activity over the Parent Syndecan-2-Derived Peptide.

We previously showed that a synthetic peptide (S2-P) corresponding to a portion of the human syndecan-2 (SDC2) sequence can bind to the pro-domain of matrix metalloproteinase-7 (MMP-7) to inhibit colon cancer activities. Since S2-P had a relatively weak binding affinity for the MMP-7 pro-domain, we herein modified the amino acid sequence of S2-P to improve the anticancer potential. On the basis of the interaction structure of S2-P and MMP-7, four peptides were generated by replacing amino acids near Tyr 51, which is critical for the interaction. The SDC2-mimetic peptides harboring an Ala-to-Asp substitution at the C-terminal side of Tyr 51 (S2-D) or with an Ala-to-Phe substitution at the N-terminal side of Tyr 51 and an Ala-to-Asp substitution at the C-terminal side of Tyr 51 (S2-FE) showed improved interaction affinities for the MMP-7 pro-domain. Compared to S2-P, S2-FE was better able to inhibit the SDC2-MMP-7 interaction, the cell surface localization of MMP-7, the gelatin degradation activity of MMP-7, and the cancer activities (cell migration, invasion, and colony-forming activity) of human HCT116 colon cancer cells in vitro. In vivo, S2-FE inhibited the primary tumor growth and lung metastasis of CT26 mouse colon cancer cells in a xenograft mouse model. Together, these data suggest that S2-FE could be useful therapeutic anticancer peptides for colon cancer.

Syndecan Transmembrane Domain Specifically Regulates Downstream Signaling Events of the Transmembrane Receptor Cytoplasmic Domain.

Despite the known importance of the transmembrane domain (TMD) of syndecan receptors in cell adhesion and signaling, the molecular basis for syndecan TMD function remains unknown. Using in vivo invertebrate models, we found that mammalian syndecan-2 rescued both the guidance defects in C. elegans hermaphrodite-specific neurons and the impaired development of the midline axons of Drosophila caused by the loss of endogenous syndecan. These compensatory effects, however, were reduced significantly when syndecan-2 dimerization-defective TMD mutants were introduced. To further investigate the role of the TMD, we generated a chimera, 2eTPC, comprising the TMD of syndecan-2 linked to the cytoplasmic domain of platelet-derived growth factor receptor (PDGFR). This chimera exhibited SDS-resistant dimer formation that was lost in the corresponding dimerization-defective syndecan-2 TMD mutant, 2eT(GL)PC. Moreover, 2eTPC specifically enhanced Tyr 579 and Tyr 857 phosphorylation in the PDGFR cytoplasmic domain, while the TMD mutant failed to support such phosphorylation. Finally, 2eTPC, but not 2eT(GL)PC, induced phosphorylation of Src and PI3 kinase (known downstream effectors of Tyr 579 phosphorylation) and promoted Src-mediated migration of NIH3T3 cells. Taken together, these data suggest that the TMD of a syndecan-2 specifically regulates receptor cytoplasmic domain function and subsequent downstream signaling events controlling cell behavior.

The melanocortin-1 receptor reversely regulates the melanin synthesis and migration of melanoma cells via dimerization-induced conformational changes.

We previously reported that the melanocortin-1 receptor (MC1R), a key regulator of melanogenesis, regulates cell migration; however, the detailed mechanism remained unknown. Since the homo-dimerization of MC1R by four inter-subunit disulfide bonds is known to be functionally important for melanogenesis, we investigated the importance of MC1R dimerization for cell migration. Unlike the wild-type MC1R, the dimerization-defective mutant MC1R in which four critical Cys residues were replaced with Ala residues (Cys35-267-273-275Ala) significantly inhibited melanin synthesis but enhanced cell migration in human MNT-1 and A375 melanoma cells. This suggests that there may be a reverse correlation between melanin synthesis and cell migration. Interestingly, melanoma cells expressing the dimerization-defective mutant exhibited enhanced expression of the cell surface heparan sulfate proteoglycan, syndecan-2, and knockdown of syndecan-2 expression decreased the mutant-mediated cell migration. Consistently, ASIP, an antagonist of MC1R, enhanced syndecan-2 expression and cell migration and reversed the α-melanocyte-stimulating hormone (α-MSH)-mediated inhibition of syndecan-2 expression. Furthermore, α-MSH reduced the cell migration of MNT1 cells expressing wild-type MC1R but not its dimerization-defective mutant. Together, these data strongly suggest that MC1R reversely regulates melanin synthesis and migration via the conformational changes induced by dimerization.

Syndecan-2 cytoplasmic domain up-regulates matrix metalloproteinase-7 expression via the protein kinase Cγ-mediated FAK/ERK signaling pathway in colon cancer.

The syndecan family of heparan sulfate proteoglycans contributes to cell adhesion and communication by serving as co-receptors for cell signaling and extracellular matrix molecules. Syndecan-2 is located at the cell surface, and we previously reported that it induces matrix metalloproteinase-7 (MMP-7) expression in colon cancer cells. However, the underlying regulatory mechanisms are unknown. Here, we report that overexpression of syndecan-2 in HT-29 colon cancer cells increases the phosphorylation of focal adhesion kinase (FAK) and ERK in parallel with up-regulated MMP-7 expression, but a syndecan-2 mutant lacking the cytoplasmic domain showed significant reductions in these effects. Consistent with this observation, FAK inhibition via FAK-related non-kinase expression or inhibition of ERK with the ERK1/2 inhibitor SCH772984 diminished the syndecan-2-mediated up-regulation of MMP-7. Activation of PKC enhanced syndecan-2-mediated MMP-7 expression, whereas inhibition of PKC had the opposite effect. Of note, the exogenous expression of syndecan-2 triggered localization of PKCγ to the membrane. Expression of syndecan-2 harboring a phosphomimetic (S198E) mutation of the variable region of the cytoplasmic domain enhanced MMP-7 expression and FAK phosphorylation. Finally, experimental suppression of shedding of the syndecan-2 extracellular domain did not significantly affect the syndecan-2-mediated up-regulation of MMP-7 in the early period after syndecan-2 overexpression. Taken together, these findings suggest that syndecan-2's cytoplasmic domain up-regulates MMP-7 expression in colon cancer cells via PKCγ-mediated activation of FAK/ERK signaling.

Syndecan-2 enhances E-cadherin shedding and fibroblast-like morphological changes by inducing MMP-7 expression in colon cancer cells.

E-cadherin plays a mechanical role in mediating cell-cell interactions and maintaining epithelial tissue integrity, and the loss of E-cadherin function has been implicated in cancer progression and metastasis. Syndecan-2, a cell-surface heparan sulfate proteoglycan, is upregulated during the development of colon cancer. Here, we assessed the functional relationship between E-cadherin and syndecan-2. We found that stable overexpression of syndecan-2 in a human colorectal adenocarcinoma cell line (HT29) enhanced the proteolytic shedding of E-cadherin to conditioned-media. Either knockdown of matrix metalloproteinase 7 (MMP-7) or inhibition of MMP-7 activity using GM6001 significantly reduced the extracellular shedding of E-cadherin, suggesting that syndecan-2 mediates E-cadherin shedding via MMP-7. Consistent with this notion, enhancement of MMP-7 expression by interleukin-1α treatment increased the shedding of E-cadherin. Conversely, the specific reduction of either syndecan-2 or MMP-7 reduced the shedding of E-cadherin. HT29 cells overexpressing syndecan-2 showed significantly lower cell-surface expression of E-cadherin, decreased cell-cell contact, a more fibroblastic cell morphology, and increased expression levels of ZEB-1. Taken together, these data suggest that syndecan-2 induces extracellular shedding of E-cadherin and supports the acquisition of a fibroblast-like morphology by regulating MMP-7 expression in a colon cancer cell line.

Antifungal Activity of Bulgarian Rose Damascena Oil against Vaginitis-Causing Opportunistic Fungi.

Since Bulgarian rose damascena oil is known for its anti-inflammatory, antioxidant, and antimicrobial properties, we investigated its antifungal activity against the species of Candida, which are among the most common opportunistic fungal pathogens. Our disk-diffusion assay revealed that Bulgarian rose damascena oil effectively inhibited the growth of Candida albicans along with various bacteria. The minimum inhibitory and fungicidal concentrations against Candida albicans and Candida glabrata were all 0.25%. Under our experimental conditions, Bulgarian rose damascena oil showed better inhibitory effects on Candida glabrata and Candida albicans than several popular essential oils reported to have antifungal activity other than Origanum vulgare oil. Interestingly, Bulgarian rose damascena oil showed better antifungal activity against Candida species at acidic pH and induced cell death of Candida species in the culture medium, with cell death seen in 25-35% of the cells exposed to 0.05% Bulgarian rose damascena oil. Furthermore, Bulgarian rose damascena oil inhibited the hyphal growth of Candida albicans cultured in the RPMI medium with fetal bovine serum. These findings collectively suggest that Bulgarian rose damascena oil has antifungal activity against Candida species and thus could potentially be developed in novel therapies for vaginitis-causing pathogenic fungi.

Synergistic Anti-Inflammatory Effects of Ethanol Extracts from Chrysanthemum zawadskii Flower and Cudrania tricuspidata Fruit Occur via Inhibition of the NF-κB Signaling Pathway.

Chrysanthemum zawadskii (CZ) and Cudrania tricuspidata (CT) are both traditional Korea herbal medicines, which is widely used to treat fever, cough, gastritis, and women's diseases that may be linked to inflammatory response. Although it has been used to treat diseases related to inflammation, there has been no case of the synergistic anti-inflammatory properties of both extracts. Our data revealed that ethanol extracts of dried whole CZ exhibited free radical-scavenging capacity in vitro, reduced LPS-induced intracellular reactive oxygen species, and decreased the LPS-induced upregulations of the mRNAs encoding iNOS, COX-2, and IL-6 in RAW 264.7 cells, without significant cytotoxicity. This anti-inflammatory effect was most evident from flower extracts: ethanol extracts from flowers significantly reduced the LPS-induced upregulations of iNOS and COX-2 at a concentration of 100 µg/ml. An ethanol extract of the fruit from CT also exerted a radical scavenging capacity and suppressed LPS-induced proinflammatory gene expression: 5.5 µg/ml of the ethanol extract significantly reduced the ability of LPS to induce the mRNA expression levels of iNOS and IL-6 without apparent cytotoxicity. Furthermore, as little as 1.0 µg/ml of the combined ethanol extracts of CZ flower and CT fruit reduced the LPS-induced changes monitored herein, decreasing the upregulations of iNOS and IL-6, and decreasing the nuclear localization of NF-κB p65. These results suggest that the observed synergistic anti-inflammatory effects may be mediated via inhibition of NF-κB signaling. Taken together, these data suggest that ethanol extracts from CZ flowers and CT fruits have synergistic anti-inflammatory effects and that a combination of the two extracts could prove useful for the treatment of inflammation-related diseases.

Shed syndecan-2 enhances colon cancer progression by increasing cooperative angiogenesis in the tumor microenvironment.

Although shed syndecan-2 potentiated the tumorigenic activities of colon cancer cells, how shed syndecan-2 increases this tumorigenic potential remains unclear. Using an orthotopic mouse model of colon cancer, we show that shed syndecan-2 increases colon cancer progression by cooperatively promoting angiogenesis. Co-administration with a synthetic peptide of shed syndecan-2 (S2LQ) enhanced the survival and tumor engraftment of luciferase-expressing CT26 colon adenocarcinoma cells orthotopically implanted into the cecum of BALB/c mice. Intravenous injection of S2LQ further enhanced the growth of orthotopic tumors in the cecum, with increases in the tissue infiltration of macrophages and the formation of blood vessels, mainly in peripheral layers of the tumor facing the stroma. Furthermore, S2LQ stabilized HIF1α and enhanced the VEGF expression in human colon cancer cell lines, and increased the migration of RAW 264.7 murine macrophage cells and bone marrow-derived macrophages. Finally, S2LQ increased the tube formation of vascular endothelial cells in vitro. Together, these data demonstrate that shed syndecan-2 enhances tumorigenic activity by increasing the crosstalk of cancer cells with tumor-associated macrophages and endothelial cells to enhance angiogenesis for colon cancer progression in the tumor microenvironment.

Colocalization with MMP-7 in the Distal Colon is Crucial for Syndecan-2 Shedding in Dextran Sulfate Sodium-Induced Colitis Mice.

INTRODUCTION: Syndecan-2 expression is elevated during chronic inflammation and cancer development, and its shedding is observed in cancer patients. However, it remained unknown whether inflammation triggers syndecan-2 shedding. METHODS: The colitis model was produced in C57BL/6 mice by oral administration of 2-3% dextran sulfate sodium (DSS) in the drinking water. Syndecan-2 and MMP-7 expression levels in tissues and cells were detected by real-time PCR, Western blotting, and immunohistochemistry. Shed syndecan-2 levels were detected by slot blotting. For tissue culture, colon tissues were divided into proximal, transverse, and distal parts, and incubated in culture media. RESULTS: In C57BL/6 mice with DSS-induced colitis, syndecan-2 shedding began to increase after week 12 of chronic inflammation and continued to increase at week 15. The level of shed syndecan-2 correlated with the colocalization of syndecan-2 and MMP-7 in distal colon tissues. The mRNA expression of IL-6 was increased specifically in trans-distal colon tissues from weeks 9 to 15. IL-6 induced syndecan-2 expression and shedding and MMP-7 expression in ex vivo-cultured distal colon tissues and adenoma cell lines derived from the distal colon. IL-6 treatment induced STAT3 phosphorylation and MMP-7 expression in DLD-1 cells. The application of MMP-7 to ex vivo-cultured colon tissues increased the shedding of syndecan-2 to the culture medium. CONCLUSION: Our findings suggest that chronic inflammation induces syndecan-2 shedding via the site-specific colocalization of syndecan-2 with MMP-7 in the distal colon.

Extracellular Vesicles from Korean Codium fragile and Sargassum fusiforme Negatively Regulate Melanin Synthesis.

Although various marine ingredients have been exploited for the development of cosmetic products, no previous study has examined the potential of seaweed extracellular vesicles (EV) in such applications. Our results revealed that EV from Codium fragile and Sargassum fusiforme effectively decreased α-MSH-mediated melanin synthesis in MNT-1 human melanoma cells, associated with downregulation of MITF (microphthalmia-associated transcription factor), tyrosinase and TRP1 (tyrosinase-related proteins 1). The most effective inhibitory concentrations of EV were 250 µg/ml for S. fusiforme and 25 µg/ml for C. fragile, without affecting the viability of MNT-1 cells. Both EV reduced melanin synthesis in the epidermal basal layer of a three-dimensional model of human epidermis. Moreover, the application of the prototype cream containing C. fragile EV (final 5 µg/ml) yielded 1.31% improvement in skin brightness in a clinical trial. Together, these results suggest that EV from C. fragile and S. fusiforme reduce melanin synthesis and may be potential therapeutic and/or supplementary whitening agents.

Emerging Role of Syndecans in Extracellular Matrix Remodeling in Cancer.

The extracellular matrix (ECM) offers a structural basis for regulating cell functions while also acting as a collection point for bioactive molecules and connective tissue cells. To perform pathological functions under a pathological condition, the involved cells need to regulate the ECM to support their altered functions. This is particularly common in the development of cancer. The ECM has been recognized as a key driver of cancer development and progression, and ECM remodeling occurs at all stages of cancer progression. Thus, cancer cells need to change the ECM to support relevant cell surface adhesion receptor-mediated cell functions. In this context, it is interesting to examine how cancer cells regulate ECM remodeling, which is critical to tumor malignancy and metastatic progression. Here, we review how the cell surface adhesion receptor, syndecan, regulates ECM remodeling as cancer progresses, and explore how this can help us better understand ECM remodeling under these pathological conditions.

The oligomerization mediated by the alanine 397 residue in the transmembrane domain is crucial to sydecan-3 functions.

Syndecans are single-pass transmembrane proteins on the cell surface that are involved in various cellular functions. Previously, we reported that both homo- and hetero-form of syndecan dimers affected their functionality. However, little is known about the structural role of the transmembrane domain of syndecan-3. A series of glutathione-S-transferase syndecan-3 proteins showed that syndecan-3 formed SDS-resistant dimers and oligomers. SDS-resistant oligomer formation was barely observed in the syndecan deletion mutants lacking the transmembrane domain. Interestingly, the presence of an alanine 397 residue in the transmembrane domain correlated with SDS-resistant oligomer, and its replacement by phenylalanine (AF mutant) significantly reduced SDS-resistant oligomer formation. Beside the AF mutant significantly reduced syndecan-3 mediated cellular processes such as cell adhesion, migration and neurite outgrowth of SH-SY5Y neuroblastoma. Furthermore, the alanine residue regulated hetero-oligomer formation of syndecan-3, and hetero-oligomer formation significantly reduced syndecan-3-mediated neurite outgrowth of SH-SY5Y cells. Taken together, all these data suggest that syndecan-3 has a specific feature of oligomerization by the transmembrane domain and this oligomerization tendency is crucial for the function of syndecan-3.

D-tyrosine adds an anti-melanogenic effect to cosmetic peptides.

D-tyrosine is known to negatively regulate melanin synthesis by inhibiting tyrosinase activity. Here, we further reveal that peptides containing terminal D-tyrosine can reduce the melanin contents of human melanocytes. The addition of D-tyrosine to the terminus of the commercial anti-wrinkle peptide, pentapeptide-18 endowed the peptide with the ability to reduce the melanin content and tyrosinase activity in human MNT-1 melanoma cells and primary melanocytes. Consistently, terminal D-tyrosine-containing pentapeptide-18 inhibited the melanogenesis induced by α-MSH treatment or UV irradiation of MNT-1 cells and reduced melanin synthesis in the epidermal basal layer of a 3D human skin model. Furthermore, the addition of D-tyrosine to an anti-aging peptide (GEKG) or an anti-inflammatory peptide (GHK) endowed these short peptides with anti-melanogenic effects without altering their intrinsic effects. Together, these data suggest that the addition of D-tyrosine at the terminus of a short cosmetic peptide adds an anti-melanogenic effect to its intrinsic cosmetic effect. Our work offers a novel means of generating dual-function cosmetic peptides.

Proteoglycans and glycosaminoglycans as regulators of cancer stem cell function and therapeutic resistance.

In contrast to the bulk of the tumor, a subset of cancer cells called cancer stem cells (CSC; or tumor-initiating cells) is characterized by self-renewal, unlimited proliferative potential, expression of multidrug resistance proteins, active DNA repair capacity, apoptosis resistance, and a considerable developmental plasticity. Due to these properties, CSCs display increased resistance to chemo- and radiotherapy. Recent findings indicate that aberrant functions of proteoglycans (PGs) and glycosaminoglycans (GAGs) contribute substantially to the CSC phenotype and therapeutic resistance. In this review, we summarize how the diverse functions of the glycoproteins and carbohydrates facilitate acquisition and maintenance of the CSC phenotype, and how this knowledge can be exploited to develop novel anticancer therapies. For example, the large transmembrane chondroitin sulfate PG NG2/CSPG4 marks stem cell (SC) populations in brain tumors. Cell surface heparan sulfate PGs of the syndecan and glypican families modulate the stemness-associated Wnt, hedgehog, and notch signaling pathways, whereas the interplay of hyaluronan in the SC niche with CSC CD44 determines the maintenance of stemness and promotes therapeutic resistance. A better understanding of the molecular mechanisms by which PGs and GAGs regulate CSC function will aid the development of targeted therapeutic approaches which could avoid relapse after an otherwise successful conventional therapy. Chimeric antigen receptor T cells, PG-primed dendritic cells, PG-targeted antibody-drug conjugates, and inhibitory peptides and glycans have already shown highly promising results in preclinical models.

Tyrosine 51 residue of the syndecan-2 extracellular domain is involved in the interaction with and activation of pro-matrix metalloproteinase-7.

Although syndecan-2 is known to interact with the matrix metalloproteinase-7 (MMP-7), the details of their interaction were unknown. Our experiments with a series of syndecan-2 extracellular domain deletion mutants show that the interaction is mediated through an interaction of the extracellular domain of syndecan-2 (residues 41 to 60) with the α2 helix-loop-α3 helix in the pro-domain of MMP-7. NMR and molecular docking model show that Glu7 of the α1 helix, Glu32 of the α2 helix, and Gly48 and Ser52 of the α2 helix-loop-α3 helix of the MMP-7 pro-domain form the syndecan-2-binding pocket, which is occupied by the side chain of tyrosine residue 51 (Tyr51) of syndecan-2. Consistent with this notion, the expression of a syndecan-2 mutant in which Tyr51 was changed to Ala diminished the interaction between the syndecan-2 extracellular domain and the pro-domain of MMP-7. Furthermore, HT-29 colon adenocarcinoma cells expressing the interaction-defective mutant exhibited reductions in the cell-surface localization of MMP-7, the processing of pro-MMP-7 into active MMP-7, the MMP-7-mediated extracellular domain shedding of both syndecan-2 and E-cadherin, and syndecan-2-mediated anchorage-independent growth. Collectively, these data strongly suggest that Tyr51 of the syndecan-2 extracellular domain mediates its interaction with and activating processing of pro-MMP-7 and regulates MMP-7-dependent syndecan-2 functions.

Syndecan transmembrane domain modulates intracellular signaling by regulating the oligomeric status of the cytoplasmic domain.

Cell surface receptors must specifically recognize an extracellular ligand and then trigger an appropriate response within the cell. Their general structure enables this, as it comprises an extracellular domain that can bind an extracellular ligand, a cytoplasmic domain that can transduce a signal inside the cell to produce an appropriate response, and a transmembrane domain that links the two and is responsible for accurately delivering specific information on a binding event from the extracellular domain to the cytoplasmic domain, to trigger the proper response. A vast body of research has focused on elucidating the specific mechanisms responsible for regulating extracellular binding events and the subsequent interactions of the cytoplasmic domain with intracellular signaling. In contrast, far less work has focused on examining how the transmembrane domain links these domains and delivers the necessary information. In this review, we propose the importance of the transmembrane domain as a signal regulator. We highlight the cell adhesion receptor, syndecan, as a special case, and propose that the transmembrane domain-mediated oligomerization of the syndecan cytoplasmic domain is a unique regulatory mechanism in syndecan signaling.

Syndecans play dual roles as cell adhesion receptors and docking receptors.

Syndecan are a family of cell surface heparan sulfate proteoglycans that act as cell surface receptors. Most cell surface receptors have a limited number and type of ligand interactions, responding only to the binding of (a) specific ligand(s). In contrast, syndecans can interact with various numbers and types of ligands, and thus play more diverse roles than others. Various syndecan functions have not yet been fully classified and categorized, but we herein review previous studies suggesting that syndecans play dual function as cell surface receptors by acting as both adhesion receptors and docking receptors. Through this dual regulatory function, syndecans are capable of regulating both intra- and extracellular activities, potentially altering a variety of cell behaviors.