Decorin, a Novel Player in the Insulin-like Growth Factor System

Cetuximab promotes epithelial to mesenchymal transition and cancer associated fibroblasts in patients with head and neck cancer

Purpose

To investigate if cetuximab induces epithelial to mesenchymal transition (EMT) and activation of cancer associated fibroblast (CAF) in the tumors of patients with squamous cell carcinoma of the head and neck (SCCHN).

Methods

Cetuximab was administered for two weeks prior to surgery to 20 treatment-naïve patients. Five untreated patients were included as controls. Tumor biopsies were performed at baseline and before surgery. Gene expression profiles and quantitative real-time PCR (qRT-PCR) analysis of the pre-and post-treatment biopsies were compared. To further investigate EMT and CAF, correlations between previously described EMT and CAF markers and our microarray data set were calculated.

Results

Gene expression profile analyses and qRT-PCR showed that some of the genes modified by cetuximab were related to CAFs and EMT (ZNF521, CXCL12, ASPN, OLFML3, OLFM1, TWIST1, LEF1, ZEB1, FAP). We identified 2 patient clusters with different EMT and CAF characteristics. Whereas one cluster showed clear upregulation of expression of genes implicated in CAF and EMT including markers of embryologic pathways like NOTCH and Wnt, the other did not.

Conclusion

Even if EMT and CAFs are implicated in cetuximab resistance in pre-clinical models, we demonstrate for the first time that these molecular processes may occur clinically early on.

Response of Hepatic Stellate Cells to TGFB1 Differs from the Response of Myofibroblasts. Decorin Protects against the Action of Growth Factor

Regardless to the exact nature of damage, hepatic stellate cells (HSCs) and other non-parenchymal liver cells transform to activated myofibroblasts, synthesizing the accumulating extracellular matrix (ECM) proteins, and transforming growth factor-β1 (TGF-β1) plays a crucial role in this process. Later it was discovered that decorin, member of the small leucin rich proteoglycan family is able to inhibit this action of TGF-β1. The aim of our present study was to clarify whether HSCs and activated myofibroblasts of portal region exert identical or different response to TGF-β1 exposure, and the inhibitory action of decorin against the growth factor is a generalized phenomenon on myofibroblast of different origin? To this end we measured mRNA expression and production of major collagen components (collagen type I, III and IV) of the liver after stimulation and co-stimulation with TGF-β1 and decorin in primary cell cultures of HSCs and myofibroblasts (MFs). Production of matrix proteins, decorin and members of the TGF-β1 signaling pathways were assessed on Western blots. Messenger RNA expression of collagens and TIEG was quantified by real-time RT-PCR. HSCs and MFs responded differently to TGF-β1 exposure. In contrast to HSCs in which TGF-β1 stimulated the synthesis of collagen type I, type III, and type IV, only the increase of collagen type IV was detected in portal MFs. However, in a combined treatment, decorin seemed to interfere with TGF-β1 and its stimulatory effect was abolished. The different mode of TGF-β1 action is mirrored by the different activation of signaling pathways in activated HSCs and portal fibroblasts. In HSCs the activation of pSMAD2 whereas in myofibroblasts the activation of MAPK pathway was detected. The inhibitory effect of decorin was neither related to the Smad-dependent nor to the Smad-independent signaling pathways.

Decorin inhibits the proliferation of HepG2 cells by elevating the expression of transforming growth factor-β receptor II

The aim of the present study was to investigate the effects of decorin (DCN) on the proliferation of human hepatoma HepG2 cells and the involvement of transforming growth factor-β (TGF-β) signaling pathway. A vector containing DCN was transfected into HepG2 cells with the use of Lipofectamine 2000. Cell proliferation was assessed with an MTT assay, and western blot analysis was used to detect the protein expression of TGF-β receptor I (TGF-βRI), phosphorylated TGF-βRI, p15 and TGF-βRII. In addition, small interfering RNA (siRNA) silencing was performed to knock down the target gene. The results indicated that, compared with the control group, cell proliferation was significantly decreased in HepG2 cells transfected with DCN. In addition, DCN transfection significantly increased the phosphorylation level of TGF-βRI in HepG2 cells. The expression of the downstream factor p15 was also significantly elevated in the DCN-transfected HepG2 cells. Furthermore, DCN transfection significantly elevated the expression level of TGF-βRII in HepG2 cells. By contrast, the silencing of TGF-βRII significantly decreased the phosphorylation of TGF-βRI in DCN-transfected HepG2 cells. In addition, TGF-βRII silencing abolished the effects of DCN on the proliferation of HepG2 cells. In conclusion, DCN elevated the expression level of TGF-βRII, increased the phosphorylation level of TGF-βRI, enhanced the expression of p15, and finally inhibited the proliferation of HepG2 cells. These findings may contribute to the understanding of the role of DCN in the pathogenesis of hepatic carcinoma and assist in the disease treatment.

Extracellular Matrix Regulation of Stem Cell Behavior

Stem cells hold great promise in treating many diseases either through promoting endogenous cell repair or through direct cell transplants. In order to maximize their potential, understanding the fundamental signals and mechanisms that regulate their behavior is essential. The extracellular matrix (ECM) is one such component involved in mediating stem cell fate. Recent studies have made significant progress in understanding stem cell-ECM interactions. Technological developments have provided greater clarity in how cells may sense and respond to the ECM, in particular the physical properties of the matrix. This review summarizes recent developments, providing illustrative examples of the different modes with which the ECM controls both embryonic and adult stem cell behavior.

Forced exercise-induced osteoarthritis is attenuated in mice lacking the small leucine-rich proteoglycan decorin

OBJECTIVE

Interterritorial regions of articular cartilage matrix are rich in decorin, a small leucine-rich proteoglycan and important structural protein, also involved in many signalling events. Decorin sequesters transforming growth factor β (TGFβ), thereby regulating its activity. Here, we analysed whether increased bioavailability of TGFβ in decorin-deficient (Dcn^-/-) cartilage leads to changes in biomechanical properties and resistance to osteoarthritis (OA).

METHODS

Unchallenged knee cartilage was analysed by atomic force microscopy (AFM) and immunohistochemistry. Active transforming growth factor β-1 (TGFβ1) content within cultured chondrocyte supernatants was measured by ELISA. Quantitative real-time (RT)-PCR was used to analyse mRNA expression of glycosaminoglycan (GAG)-modifying enzymes in C28/I2 cells following TGFβ1 treatment. In addition, OA was induced in Dcn^-/- and wild-type (WT) mice via forced exercise on a treadmill.

RESULTS

AFM analysis revealed a strikingly higher compressive stiffness in Dcn^-/- than in WT cartilage. This was accompanied by increased negative charge and enhanced sulfation of GAG chains, but not by alterations in the levels of collagens or proteoglycan core proteins. In addition, decorin-deficient chondrocytes were shown to release more active TGFβ1. Increased TGFβ signalling led to enhanced Chst11 sulfotransferase expression inducing an increased negative charge density of cartilage matrix. These negative charges might attract more water resulting in augmented compressive stiffness of the tissue. Therefore, decorin-deficient mice developed significantly less OA after forced exercise than WT mice.

CONCLUSIONS

Our study demonstrates that the disruption of decorin-restricted TGFβ signalling leads to higher stiffness of articular cartilage matrix, rendering joints more resistant to OA. Therefore, the loss of an important structural component can improve cartilage homeostasis.

Antitumor effect and safety profile of systemically delivered oncolytic adenovirus complexed with EGFR-targeted PAMAM-based dendrimer in orthotopic lung tumor model

Adenovirus (Ad)-mediated cancer gene therapy has been proposed as a promising alternative to conventional therapy for cancer. However, success of systemically administered naked Ad has been limited due to the immunogenicity of Ad and the induction of hepatotoxicity caused by Ad's native tropism. In this study, we synthesized an epidermal growth factor receptor (EGFR)-specific therapeutic antibody (ErbB)-conjugated and PEGylated poly(amidoamine) (PAMAM) dendrimer (PPE) for complexation with Ad. Transduction of Ad was inhibited by complexation with PEGylated PAMAM (PP) dendrimer due to steric hindrance. However, PPE-complexed Ad selectively internalized into EGFR-positive cells with greater efficacy than either naked Ad or Ad complexed with PP. Systemically administered PPE-complexed oncolytic Ad elicited significantly reduced immunogenicity, nonspecific liver sequestration, and hepatotoxicity than naked Ad. Furthermore, PPE-complexed oncolytic Ad demonstrated prolonged blood retention time, enhanced intratumoral accumulation of Ad, and potent therapeutic efficacy in EGFR-positive orthotopic lung tumors in comparison with naked Ad. We conclude that ErbB-conjugated and PEGylated PAMAM dendrimer can efficiently mask Ad's capsid and retarget oncolytic Ad to be efficiently internalized into EGFR-positive tumor while attenuating toxicity induced by systemic administration of naked oncolytic Ad.

Inhibition of the myostatin/Smad signaling pathway by short decorin-derived peptides

Myostatin, also known as growth differentiation factor 8, is a member of the transforming growth factor-beta superfamily that has been shown to play a key role in the regulation of the skeletal muscle mass. Indeed, while myostatin deletion or loss of function induces muscle hypertrophy, its overexpression or systemic administration causes muscle atrophy. Since myostatin blockade is effective in increasing skeletal muscle mass, myostatin inhibitors have been actively sought after. Decorin, a member of the small leucine-rich proteoglycan family is a metalloprotein that was previously shown to bind and inactivate myostatin in a zinc-dependent manner. Furthermore, the myostatin-binding site has been shown to be located in the decorin N-terminal domain. In the present study, we investigated the anti-myostatin activity of short and soluble fragments of decorin. Our results indicate that the murine decorin peptides DCN48-71 and 42-65 are sufficient for inactivating myostatin in vitro. Moreover, we show that the interaction of mDCN48-71 to myostatin is strictly zinc-dependent. Binding of myostatin to activin type II receptor results in the phosphorylation of Smad2/3. Addition of the decorin peptide 48-71 decreased in a dose-dependent manner the myostatin-induced phosphorylation of Smad2 demonstrating thereby that the peptide inhibits the activation of the Smad signaling pathway. Finally, we found that mDCN48-71 displays a specificity towards myostatin, since it does not inhibit other members of the transforming growth factor-beta family.

Chondrogenesis of Human Infrapatellar Fat Pad Stem Cells on Acellular Dermal Matrix

Acellular dermal matrix (ADM) has been in clinical use for decades in numerous surgical applications. The ability for ADM to promote cellular repopulation, revascularisation and tissue regeneration is well documented. Adipose stem cells have the ability to differentiate into mesenchymal tissue types, including bone and cartilage. The aim of this study was to investigate the potential interaction between ADM and adipose stem cells in vitro using TGFβ3 and BMP6. Human infrapatellar fat pad-derived adipose stem cells (IPFP-ASC) were cultured with ADM derived from rat dermis in chondrogenic (TGFβ3 and BMP6) medium in vitro for 2 and 4 weeks. Histology, qPCR, and immunohistochemistry were performed to assess for markers of chondrogenesis (collagen Type II, SOX9 and proteoglycans). At 4 weeks, cell-scaffold constructs displayed cellular changes consistent with chondrogenesis, with evidence of stratification of cell layers and development of a hyaline-like cartilage layer superficially, which stained positively for collagen Type II and proteoglycans. Significant cell–matrix interaction was seen between the cartilage layer and the ADM itself with seamless integration between each layer. Real time qPCR showed significantly increased COL2A1, SOX9, and ACAN gene expression over 4 weeks when compared to control. COL1A2 gene expression remained unchanged over 4 weeks. We believe that the principles that make ADM versatile and successful for tissue regeneration are applicable to cartilage regeneration. This study demonstrates in vitro the ability for IPFP-ASCs to undergo chondrogenesis, infiltrate, and interact with ADM. These outcomes serve as a platform for in vivo modelling of ADM for cartilage repair.

Mechanisms of trophoblast migration, endometrial angiogenesis in preeclampsia: The role of decorin

The objective of the present review is to synthesize the information on the cellular and molecular players responsible for maintaining a homeostatic balance between a naturally invasive human placenta and the maternal uterus in pregnancy; to review the roles of decorin (DCN) as a molecular player in this homeostasis; to list the common maladies associated with a break-down in this homeostasis, resulting from a hypo-invasive or hyper-invasive placenta, and their underlying mechanisms. We show that both the fetal components of the placenta, represented primarily by the extravillous trophoblast, and the maternal component represented primarily by the decidual tissue and the endometrial arterioles, participate actively in this balance. We discuss the process of uterine angiogenesis in the context of uterine arterial changes during normal pregnancy and preeclampsia. We compare and contrast trophoblast growth and invasion with the processes involved in tumorigenesis with special emphasis on the roles of DCN and raise important questions that remain to be addressed. Decorin (DCN) is a small leucine-rich proteoglycan produced by stromal cells, including dermal fibroblasts, chondrocytes, chorionic villus mesenchymal cells and decidual cells of the pregnant endometrium. It contains a 40 kDa protein core having 10 leucine-rich repeats covalently linked with a glycosaminoglycan chain. Biological functions of DCN include: collagen assembly, myogenesis, tissue repair and regulation of cell adhesion and migration by binding to ECM molecules or antagonising multiple tyrosine kinase receptors (TKR) including EGFR, IGF-IR, HGFR and VEGFR-2. DCN restrains angiogenesis by binding to thrombospondin-1, TGFβ, VEGFR-2 and possibly IGF-IR. DCN can halt tumor growth by antagonising oncogenic TKRs and restraining angiogenesis. DCN actions at the fetal-maternal interface include restraint of trophoblast migration, invasion and uterine angiogenesis. We demonstrate that DCN overexpression in the decidua is associated with preeclampsia (PE); this may have a causal role in PE by compromising endovascular differentiation of the trophoblast and uterine angiogenesis, resulting in poor arterial remodeling. Elevated DCN level in the maternal blood is suggested as a potential biomarker in PE.

Decorin: A Growth Factor Antagonist for Tumor Growth Inhibition

Decorin (DCN) is the best characterized member of the extracellular small leucine-rich proteoglycan family present in connective tissues, typically in association with or “decorating” collagen fibrils. It has substantial interest to clinical medicine owing to its antifibrotic, anti-inflammatory, and anticancer effects. Studies on DCN knockout mice have established that a lack of DCN is permissive for tumor development and it is regarded as a tumor suppressor gene. A reduced expression or a total disappearance of DCN has been reported to take place in various forms of human cancers during tumor progression. Furthermore, when used as a therapeutic molecule, DCN has been shown to inhibit tumor progression and metastases in experimental cancer models. DCN affects the biology of various types of cancer by targeting a number of crucial signaling molecules involved in cell growth, survival, metastasis, and angiogenesis. The active sites for the neutralization of different growth factors all reside in different parts of the DCN molecule. An emerging concept that multiple proteases, especially those produced by inflammatory cells, are capable of cleaving DCN suggests that native DCN could be inactivated in a number of pathological inflammatory conditions. In this paper, we review the role of DCN in cancer.

Decorin-Mediated Inhibition of Human Trophoblast Cells Proliferation, Migration, and Invasion and Promotion of Apoptosis In Vitro

Preeclampsia (PE) is a unique complication of pregnancy, the pathogenesis of which has been generally accepted to be associated with the dysfunctions of extravillous trophoblast (EVT) including proliferation, apoptosis, and migration and invasion. Decorin (DCN) has been proved to be a decidua-derived TGF-binding proteoglycan, which negatively regulates proliferation, migration, and invasiveness of human extravillous trophoblast cells. In this study, we identified a higher expression level of decorin in severe PE placentas by both real-time reverse transcription-polymerase chain reaction (qRT-PCR) and immunohistochemistry (IHC). And an inhibitory effect of decorin on proliferation, migration, and invasion and an enhanced effect on apoptosis in trophoblast cells HTR-8/SVneo and JEG-3 were validated in vitro. Also the modulations of decorin on trophoblast cells' metastasis and invasion functions were detected through regulating the matrix metalloproteinases (MMP2 and MMP9). Thus, we suggested that the contribution of decorin to the modulation of trophoblast cells might have implications for the pathogenesis of preeclampsia.

Decoding the Matrix: Instructive Roles of Proteoglycan Receptors

The extracellular matrix is a dynamic repository harboring instructive cues that embody substantial regulatory dominance over many evolutionarily conserved intracellular activities, including proliferation, apoptosis, migration, motility, and autophagy. The matrix also coordinates and parses hierarchical information, such as angiogenesis, tumorigenesis, and immunological responses, typically providing the critical determinants driving each outcome. We provide the first comprehensive review focused on proteoglycan receptors, that is, signaling transmembrane proteins that use secreted proteoglycans as ligands, in addition to their natural ligands. The majority of these receptors belong to an exclusive subset of receptor tyrosine kinases and assorted cell surface receptors that specifically bind, transduce, and modulate fundamental cellular processes following interactions with proteoglycans. The class of small leucine-rich proteoglycans is the most studied so far and constitutes the best understood example of proteoglycan-receptor interactions. Decorin and biglycan evoke autophagy and immunological responses that deter, suppress, or exacerbate pathological conditions such as tumorigenesis, angiogenesis, and chronic inflammatory disease. Basement membrane-associated heparan sulfate proteoglycans (perlecan, agrin, and collagen XVIII) represent a unique cohort and provide proteolytically cleaved bioactive fragments for modulating cellular behavior. The receptors that bind the genuinely multifactorial and multivalent proteoglycans represent a nexus in understanding basic biological pathways and open new avenues for therapeutic and pharmacological intervention.

The absence of the embryo in the pseudopregnant uterus alters the deposition of some ECM molecules during decidualization in mice

The embryo-implantation promotes deep changes in the uterus resulting in the formation of a new structure at the maternal-fetal interface, the decidua. Decidualization can also be induced in pseudopregnant rodents resulting in a structure called deciduoma that is morphologically and functionally similar to the decidua. Previous studies from our and other laboratories demonstrate that in rodents, decidualization of the endometrium requires remarkable remodeling of the endometrial extracellular matrix (ECM) that is mainly coordinated by estradiol and progesterone. The influence of the embryo in this process, however, has not yet been investigated. To enlarge the knowledge on this subject, the present study investigates the behavior of a set of ECM molecules, in the absence of paracrine cues originated from the embryo. For that deciduoma was induced in pseudopregnant Swiss mice, and the distribution of collagen types I, III, IV, V and the proteoglycans decorin and biglycan was investigated by immunolabeling from the fifth to the eighth day of pseudopregnancy. It was observed the deposition of collagen types III and IV as well as decorin and biglycan was similar to that previously described by our group in the decidua. However, in the absence of the embryo, some differences occur in the distribution of collagen types I and V, suggesting that beside the major role of ovarian hormones on the endometrial ECM remodeling, molecular signals originated from the conceptus may influence this process.

Role of extracellular matrix in development of skeletal muscle and postmortem aging of meat

The integrity of skeletal muscle is maintained by the intramuscular connective tissues (IMCTs) that are composed of extracellular matrix (ECM) molecules such as collagens, proteoglycans, and glycoproteins. The ECM plays an important role not only in providing biomechanical strength of the IMCT, but also in regulating muscle cell behavior. Some ECM molecules, such as decorin and laminin, modulate the activity of myostatin that regulates skeletal muscle mass. Furthermore, it has been shown that decorin activates Akt downstream of insulin-like growth factor-I receptor (IGF-IR) and enhances the differentiation of myogenic cells, suggesting that decorin acts as a signaling molecule to myogenic cells. With animal growth, the structural integrity of IMCT increases; collagen fibrils within the endomysium associate more closely with each other, and the collagen fibers in the perimysium become increasingly thick and their wavy pattern grows more regular. These changes increase the mechanical strength of IMCT, contributing to the toughening of meat. However, in highly marbled beef cattle like Wagyu, intramuscular fat deposits mainly in the perimysium between muscle fiber bundles during the fattening period. The development of adipose tissues appears to disorganize the structure of IMCT and contributes to the tenderness of Wagyu beef. The IMCT was considered to be rather immutable compared to myofibrils during postmortem aging of meat. However, several studies have shown that collagen networks in the IMCT are disintegrated and proteoglycan components are degraded during postmortem aging. These changes in ECM appear to reduce the mechanical strength of IMCT and contribute to the tenderness of uncooked meat or cooked meat at low temperature. Thus, the ECM plays a multifunctional role in skeletal muscle development and postmortem aging of meat.

MicroRNA 181b regulates decorin production by dermal fibroblasts and may be a potential therapy for hypertrophic scar

Hypertrophic scarring is a frequent fibroproliferative complication following deep dermal burns leading to impaired function and lifelong disfigurement. Decorin reduces fibrosis and induces regeneration in many tissues, and is significantly downregulated in hypertrophic scar and normal deep dermal fibroblasts. It was hypothesized that microRNAs in these fibroblasts downregulate decorin and blocking them would increase decorin and may prevent hypertrophic scarring. Lower decorin levels were found in hypertrophic scar as compared to normal skin, and in deep as compared to superficial dermis. A decorin 3' un-translated region reporter assay demonstrated microRNA decreased decorin in deep dermal fibroblasts, and microRNA screening predicted miR- 24, 181b, 421, 526b, or 543 as candidates. After finding increased levels of mir-181b in deep dermal fibroblasts, it was demonstrated that TGF-β1 stimulation decreased miR-24 but increased miR-181b and that hypertrophic scar and deep dermis contained increased levels of miR-181b. By blocking miR-181b with an antagomiR, it was possible to increase decorin protein expression in dermal fibroblasts. This suggests miR-181b is involved in the differential expression of decorin in skin and wound healing. Furthermore, blocking miR-181b reversed TGF-β1 induced decorin downregulation and myofibroblast differentiation in hypertrophic scar fibroblasts, suggesting a potential therapy for hypertrophic scar.

Proteoglycan form and function: A comprehensive nomenclature of proteoglycans

We provide a comprehensive classification of the proteoglycan gene families and respective protein cores. This updated nomenclature is based on three criteria: Cellular and subcellular location, overall gene/protein homology, and the utilization of specific protein modules within their respective protein cores. These three signatures were utilized to design four major classes of proteoglycans with distinct forms and functions: the intracellular, cell-surface, pericellular and extracellular proteoglycans. The proposed nomenclature encompasses forty-three distinct proteoglycan-encoding genes and many alternatively-spliced variants. The biological functions of these four proteoglycan families are critically assessed in development, cancer and angiogenesis, and in various acquired and genetic diseases where their expression is aberrant.

Oncosuppressive functions of decorin

The extracellular matrix is rapidly emerging as a prominent contributor to various fundamental processes of tumorigenesis. In particular, decorin, a member of the small leucine-rich proteoglycan gene family, is assuming a central role as a potent soluble tumor repressor. Decorin binds and antagonizes various receptor tyrosine kinases and inhibits downstream oncogenic signaling in several solid tumors. Among other functions, decorin evokes cell cycle arrest, apoptosis, and antimetastatic, and antiangiogenic programs. Recent work has revealed a paradigmatic shift in our understanding of the molecular mechanisms underlying its tumoricidal properties. Decorin adversely compromises the genetic signature of the tumor microenvironment and induces endothelial cell autophagy downstream of VEGFR2. Moreover, decorin selectively evokes destruction of tumor cell mitochondria downstream of Met through mitophagy. Acting as a partial agonist, decorin signals via proautophagic receptors and triggers procatabolic processes that parallel the classical tumoricidal properties of this multifaceted proteoglycan.

Pivotal role for decorin in angiogenesis

Angiogenesis, the formation of new blood vessels from preexisting vessels, is a highly complex process. It is regulated in a finely-tuned manner by numerous molecules including not only soluble growth factors such as vascular endothelial growth factor and several other growth factors, but also a diverse set of insoluble molecules, particularly collagenous and non-collagenous matrix constituents. In this review we have focused on the role and potential mechanisms of a multifunctional small leucine-rich proteoglycan decorin in angiogenesis. Depending on the cellular and molecular microenvironment where angiogenesis occurs, decorin can exhibit either a proangiogenic or an antiangiogenic activity. Nevertheless, in tumorigenesis-associated angiogenesis and in various inflammatory processes, particularly foreign body reactions and scarring, decorin exhibits an antiangiogenic activity, thus providing a potential basis for the development of decorin-based therapies in these pathological situations.

Decorin in human oral cancer: a promising predictive biomarker of S-1 neoadjuvant chemosensitivity

We reported previously that decorin (DCN) is significantly up-regulated in chemoresistant cancer cell lines. DCN is a small leucine-rich proteoglycan that exists and functions in stromal and epithelial cells. Accumulating evidence suggests that DCN affects the biology of several types of cancer by directly/indirectly targeting the signaling molecules involved in cell growth, survival, metastasis, and angiogenesis, however, the molecular mechanisms of DCN in chemoresistance and its clinical relevance are still unknown. Here we assumed that DCN silencing cells increase chemosusceptibility to S-1, consisted of tegafur, prodrug of 5-fluorouracil. We first established DCN knockdown transfectants derived from oral cancer cells for following experiments including chemosusceptibility assay to S-1. In addition to the in vitro data, DCN knockdown zenografting tumors in nude mice demonstrate decreasing cell proliferation and increasing apoptosis with dephosphorylation of AKT after S-1 chemotherapy. We also investigated whether DCN expression predicts the clinical responses of neoadjuvant chemotherapy (NAC) using S-1 (S-1 NAC) for oral cancer patients. Immunohistochemistry data in the preoperative biopsy samples was analyzed to determine the cut-off point for status of DCN expression by receiver operating curve analysis. Interestingly, low DCN expression was observed in five (83%) of six cases with complete responses to S-1 NAC, and in one (10%) case of 10 cases with stable/progressive disease, indicating that S-1 chemosensitivity is dramatically effective in oral cancer patients with low DCN expression compared with high DCN expression. Our findings suggest that DCN is a key regulator for chemoresistant mechanisms, and is a predictive immunomarker of the response to S-1 NAC and patient prognosis.

Cell-matrix interactions: focus on proteoglycan-proteinase interplay and pharmacological targeting in cancer

Proteoglycans are major constituents of extracellular matrices, as well as cell surfaces and basement membranes. They play key roles in supporting the dynamic extracellular matrix by generating complex structural networks with other macromolecules and by regulating cellular phenotypes and signaling. It is becoming evident, however, that proteolytic enzymes are required partners for matrix remodeling and for modulating cell signaling via matrix constituents. Proteinases contribute to all stages of diseases, particularly cancer development and progression, and contextually participate in either the removal of damaged products or in the processing of matrix molecules and signaling receptors. The dynamic interplay between proteoglycans and proteolytic enzymes is a crucial biological step that contributes to the pathophysiology of cancer and inflammation. Moreover, proteoglycans are implicated in the expression and secretion of proteolytic enzymes and often modulate their activities. In this review, we describe the emerging biological roles of proteoglycans and proteinases, with a special emphasis on their complex interplay. We critically evaluate this important proteoglycan-proteinase interactome and discuss future challenges with respect to targeting this axis in the treatment of cancer.

Soluble biglycan as a biomarker of inflammatory renal diseases

Chronic renal inflammation is often associated with a progressive accumulation of various extracellular matrix constituents, including several members of the small leucine-rich proteoglycan (SLRP) gene family. It is becoming increasingly evident that the matrix-unbound SLRPs strongly regulate the progression of inflammation and fibrosis. Soluble SLRPs are generated either via partial proteolytic processing of collagenous matrices or by de novo synthesis evoked by stress or injury. Liberated SLRPs can then bind to and activate Toll-like receptors, thus modulating downstream inflammatory signaling. Preclinical animal models and human studies have recently identified soluble biglycan as a key initiator and regulator of various inflammatory renal diseases. Biglycan, generated by activated macrophages, can enter the circulation and its elevated levels in plasma and renal parenchyma correlate with unfavorable renal function and outcome. In this review, we will focus on the critical role of soluble biglycan in inflammatory signaling in various renal disorders. Moreover, we will provide new data implicating proinflammatory effects of soluble decorin in unilateral ureteral obstruction. Finally, we will critically evaluate the potential application of soluble biglycan vis-à-vis other SLRPs (decorin, lumican and fibromodulin) as a promising target and novel biomarker of inflammatory renal diseases.

Complex influence of dermatan sulphate on breast cancer cells

Tumor transformation and progression both lead to extracellular matrix remodeling, which is also reflected in an alteration in the proportion of dermatan sulphate (DS) and chondroitin sulphate (CS) and an accumulation of the latter. In addition, a significant increase in the 6-O-sulphated disaccharide contribution to the structure of both glycosaminoglycans has been observed. It is commonly accepted that CS is more permissive for tumor growth than DS. However, the detailed role of DS in tumor progression is poorly known. We tested the effects of structurally different DSs on the behavior of cultured breast cancer cells. At a high dose (10 µg/mL), all of the DSs significantly reduced cancer cell growth, although some differences in the efficiency of action were apparent. In contrast, when used at a concentration of 1 µg/mL, the examined DSs evoked different responses ranging from the stimulation to the inhibition of cancer cell proliferation. The highest stimulatory activity was associated with fibrosis-affected fascia decorin DS, which is characterized by a particularly high content of 6-O-sulphated disaccharides. Further reduction in DS concentration to 0.5 µg/mL preserved majority of biological effects which were apparent at a dose of 1 µg/mL. The enzymatic fragmentation of the DSs, particularly by chondroitinase AC I, abolished the impact exerted by 1 µg/mL of the intact DS chains and sometimes resulted in the opposite effect. In contrast to DSs, highly sulphated C-6-S exhibited no effect on the cancer cells. Our data revealed the complexity of the effects of DSs on breast cancer cells, which include both co-receptor activity and the prevention of vascular endothelial growth factor action. In addition, the biological effect of DSs is strongly dependent not only on the glycosaminoglycan structure but also on its content in the cancer environment.

Decorin-induced proliferation of avian myoblasts involves the myostatin/Smad signaling pathway

Decorin, a small leucine-rich proteoglycan as a component of the extracellular matrix, plays an important role in the skeletal muscle development. It has been reported that decorin promoted proliferation and differentiation of muscle cells by restraining myostatin activity in rodents. However, the effects and mechanisms of decorin on avian myoblast proliferation are not understood clearly. Thus, in our research, decorin overexpressing and knocking-down quail myoblast-7 (QM7) myoblasts were established to explore the effects of decorin on avian myoblast proliferation by flow cytometry. The results showed that overexpression of decorin enhanced the proliferation of QM7 myoblasts, which was accompanied by the upregulation of follistatin and primary muscle regulatory factors (i.e., myogenic factor 5, myogenic factor 1, myogenin), and downregulation of myostatin expression, as well as the decreased phosphorylation level of SMAD family member 3 (Smad3). In line with expectations, decorin RNAi displayed an opposite effect on the proliferation and gene expression pattern of QM7 cells. In conclusion, our in vitro studies suggested the decorin-mediated myostatin/Smad signaling pathway might be involved in the regulation of avian myoblast proliferation.

Maternal bias and escape from X chromosome imprinting in the midgestation mouse placenta

To investigate the epigenetic landscape at the interface between mother and fetus, we provide a comprehensive analysis of parent-of-origin bias in the mouse placenta. Using F1 interspecies hybrids between mus musculus (C57BL/6J) and mus musculus castaneus, we sequenced RNA from 23 individual midgestation placentas, five late stage placentas, and two yolk sac samples and then used SNPs to determine whether transcripts were preferentially generated from the maternal or paternal allele. In the placenta, we find 103 genes that show significant and reproducible parent-of-origin bias, of which 78 are novel candidates. Most (96%) show a strong maternal bias which we demonstrate, via multiple mathematical models, pyrosequencing, and FISH, is not due to maternal decidual contamination. Analysis of the X chromosome also reveals paternal expression of Xist and several genes that escape inactivation, most significantly Alas2, Fhl1, and Slc38a5. Finally, sequencing individual placentas allowed us to reveal notable expression similarity between littermates. In all, we observe a striking preference for maternal transcription in the midgestation mouse placenta and a dynamic imprinting landscape in extraembryonic tissues, reflecting the complex nature of epigenetic pathways in the placenta.

Decorin induces mitophagy in breast carcinoma cells via peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) and mitostatin

Tumor cell mitochondria are key biosynthetic hubs that provide macromolecules for cancer progression and angiogenesis. Soluble decorin protein core, hereafter referred to as decorin, potently attenuated mitochondrial respiratory complexes and mitochondrial DNA (mtDNA) in MDA-MB-231 breast carcinoma cells. We found a rapid and dynamic interplay between peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) and the decorin-induced tumor suppressor gene, mitostatin. This interaction stabilized mitostatin mRNA with concurrent accumulation of mitostatin protein. In contrast, siRNA-mediated abrogation of PGC-1α-blocked decorin-evoked stabilization of mitostatin. Mechanistically, PGC-1α bound MITOSTATIN mRNA to achieve rapid stabilization. These processes were orchestrated by the decorin/Met axis, as blocking the Met-tyrosine kinase or knockdown of Met abrogated these responses. Furthermore, depletion of mitostatin blocked decorin- or rapamycin-evoked mitophagy, increased vascular endothelial growth factor A (VEGFA) production, and compromised decorin-evoked VEGFA suppression. Collectively, our findings underscore the complexity of PGC-1α-mediated mitochondrial homeostasis and establish mitostatin as a key regulator of tumor cell mitophagy and angiostasis.

Decorin differentially modulates the activity of insulin receptor isoform A ligands

The proteoglycan decorin, a key component of the tumor stroma, regulates the action of several tyrosine-kinase receptors, including the EGFR, Met and the IGF-IR. Notably, the action of decorin in regulating the IGF-I system differs between normal and transformed cells. In normal cells, decorin binds with high affinity to both the natural ligand IGF-I and the IGF-I receptor (IGF-IR) and positively regulates IGF-IR activation and downstream signaling. In contrast, in transformed cells, decorin negatively regulates ligand-induced IGF-IR activation, downstream signaling and IGF-IR-dependent biological responses. Whether decorin may bind another member of the IGF-I system, the insulin receptor A isoform (IR-A) and its cognate ligands, insulin, IGF-II and proinsulin, have not been established. Here we show that decorin bound with high affinity insulin and IGF-II and, to a lesser extent, proinsulin and IR-A. We utilized as a cell model system mouse embryonic fibroblasts homozygous for a targeted disruption of the Igf1r gene (designated R(-) cells) which were stably transfected with a human construct harboring the IR-A isoform of the receptor. Using these R(-)/IR-A cells, we demonstrate that decorin did not affect ligand-induced phosphorylation of the IR-A but enhanced IR-A downregulation after prolonged IGF-II stimulation without affecting insulin and proinsulin-dependent effects on IR-A stability. In addition, decorin significantly inhibited IGF-II-mediated activation of the Akt pathways, without affecting insulin and proinsulin-dependent signaling. Notably, decorin significantly inhibited IGF-II-mediated cell proliferation of R(-)/IR-A cells but affected neither insulin- nor proinsulin-dependent mitogenesis. Collectively, these results suggest that decorin differentially regulates the action of IR-A ligands. Decorin preferentially inhibits IGF-II-mediated biological responses but does not affect insulin- or proinsulin-dependent signaling. Thus, decorin loss may contribute to tumor initiation and progression in malignant neoplasms which depend on an IGF-II/IR-A autocrine loop.

More than skin deep: connecting melanocyte pigmentation and angiogenic diseases

Epidemiological studies have identified racial differences in susceptibility to numerous diseases, including several ocular and skin diseases characterized by increased vascular growth. In most cases, the specific mechanisms and genetic variants responsible for these differences have remained elusive. In this issue of the JCI, Adini et al. explore a direct connection between skin pigmentation and susceptibility to angiogenic diseases and identify an extracellular matrix protein that is regulated by melanogenesis and potently modulates angiogenesis.

Decorin deficiency promotes hepatic carcinogenesis

Hepatocellular carcinoma represents one of the most-rapidly spreading cancers in the world. In the majority of cases, an inflammation-driven fibrosis or cirrhosis precedes the development of the tumor. During malignant transformation, the tumor microenvironment undergoes qualitative and quantitative changes that modulate the behavior of the malignant cells. A key constituent for the hepatic microenvironment is the small leucine-rich proteoglycan decorin, known to interfere with cellular events of tumorigenesis mainly by blocking various receptor tyrosine kinases (RTK) such as EGFR, Met, IGF-IR, PDGFR and VEGFR2. In this study, we characterized cell signaling events evoked by decorin deficiency in two experimental models of hepatocarcinogenesis using thioacetamide or diethyl nitrosamine as carcinogens. Genetic ablation of decorin led to enhanced tumor occurrence as compared to wild-type animals. These findings correlated with decreased levels of the cyclin-dependent kinase inhibitor p21(WAF1/CIP1) and a concurrent elevation in retinoblastoma protein phosphorylation via cyclin dependent kinase 4. Decreased steady state p21(Waf1/Cip1) levels correlated with enhanced expression of transcription factor AP4, a known transcriptional repressor of p21(Waf1/Cip1), and enhanced c-Myc protein levels. In addition, translocation of β-catenin was a typical event in diethyl nitrosamine-evoked tumors. In parallel, decreased phosphorylation of both c-Myc and β-catenin was observed in Dcn(-/-) livers likely due to the hindered GSK3β-mediated targeting of these proteins to proteasomal degradation. We discovered that in a genetic background lacking decorin, four RTKs were constitutively activated (phosphorylated), including three known targets of decorin such as PDGFRα, EGFR, IGF-IR, and a novel RTK MSPR/RON. Our findings provide powerful genetic evidence for a crucial in vivo role of decorin during hepatocarcinogenesis as lack of decorin in the liver and hepatic stroma facilitates experimental carcinogenesis by providing an environment devoid of this potent pan-RTK inhibitor. Thus, our results support future utilization of decorin as an antitumor agent in liver cancer.

Lumican binds ALK5 to promote epithelium wound healing

Lumican (Lum), a small leucine-rich proteoglycan (SLRP) family member, has multiple matricellular functions both as an extracellular matrix component and as a matrikine regulating cell proliferation, gene expression and wound healing. To date, no cell surface receptor has been identified to mediate the matrikine functions of Lum. This study aimed to identify a perspective receptor that mediates Lum effects on promoting wound healing. Transforming growth factor-β receptor 1 (ALK5) was identified as a potential Lum-interacting protein through in silico molecular docking and molecular dynamics. This finding was verified by biochemical pull-down assays. Moreover, the Lum function on wound healing was abrogated by an ALK5-specific chemical inhibitor as well as by ALK5 shRNAi. Finally, we demonstrated that eukaryote-specific post-translational modifications are not required for the wound healing activity of Lum, as recombinant GST-Lum fusion proteins purified from E. coli and a chemically synthesized LumC₁₃ peptide (the last C-terminal 13 amino acids of Lum) have similar effects on wound healing in vitro and in vivo.

Decorin-mediated inhibition of cholangiocarcinoma cell growth and migration and promotion of apoptosis are associated with E-cadherin in vitro

Emerging evidences have shown that decorin expression is significantly reduced in many cancer tissues and cancer cells. However, its biological role and clinical significance in cholangiocarcinoma development and progression are unknown. In this study, immunohistochemistry was conducted to investigate the expression of decorin in cholangiocarcinomas. The results showed that decorin levels markedly decreased in 44 cholangiocarcinoma tissues compared to 40 adjacent normal tissues. The analysis between decorin expression and clinicopathological characteristics in cholangiocarcinoma patients showed that patients with low levels of decorin expression had a relatively poor prognosis. Moreover, recombinant human decorin treatment and overexpression of decorin in cholangiocarcinoma cells could inhibit cell proliferation, migration, and invasion and promote apoptosis. Furthermore, the E-cadherin expression significantly increased after decorin overexpression or use of recombinant human decorin in cholangiocarcinoma cells. Our findings indicated that downregulation of decorin may be identified as a poor prognostic biomarker in cholangiocarcinomas. Also, decorin-mediated inhibition of cholangiocarcinoma cell growth, migration, and invasion and promotion of cell apoptosis might be through regulation of the expression of E-cadherin in vitro.

Glycoconjugates and related molecules in human vascular endothelial cells

Vascular endothelial cells (ECs) form the inner lining of blood vessels. They are critically involved in many physiological functions, including control of vasomotor tone, blood cell trafficking, hemostatic balance, permeability, proliferation, survival, and immunity. It is considered that impairment of EC functions leads to the development of vascular diseases. The carbohydrate antigens carried by glycoconjugates (e.g., glycoproteins, glycosphingolipids, and proteoglycans) mainly present on the cell surface serve not only as marker molecules but also as functional molecules. Recent studies have revealed that the carbohydrate composition of the EC surface is critical for these cells to perform their physiological functions. In this paper, we consider the expression and functional roles of endogenous glycoconjugates and related molecules (galectins and glycan-degrading enzymes) in human ECs.

Decorin activates Akt downstream of IGF-IR and promotes myoblast differentiation

Decorin, a small leucine-rich proteoglycan, plays an important role in cellular activities through modification of growth factors. It also acts as a signaling molecule to non-muscle cells through epidermal growth factor receptor or insulin-like growth factor I receptor (IGF-IR). However, it is unclear if decorin acts as a signaling molecule to myogenic cells. In this study, we investigated the effect of decorin on the differentiation of myoblasts and the signaling via IGF-IR to myogenic cells. C2C12 myoblasts cultured in media containing decorin for 72 h showed more extensive formation of multinucleated myotubes than control cells cultured in the same media without decorin. The protein expressions of myogenin and myosin heavy chian were higher in decorn-treated cells than in control cells. These results suggest that decorin enhances the differentiation of myoblasts. Western blot analysis and immunocytochemistry showed that IGF-IR was expressed in myoblasts and myotubes. Furthermore, Akt, which is downstream of IGF-IR, was more phosphorylated in myoblasts cultured in media containing decorin than those in media without decorin. These results suggest that decorin activates Akt downstream of IGF-IR and enhances the differentiation of myogenic cells.

Decorin interferes with platelet-derived growth factor receptor signaling in experimental hepatocarcinogenesis

Decorin, a secreted small leucine-rich proteoglycan, acts as a tumor repressor in a variety of cancers, mainly by blocking the action of several receptor tyrosine kinases such as the receptors for hepatocyte, epidermal and insulin-like growth factors. In the present study we investigated the effects of decorin in an experimental model of thioacetamide-induced hepatocarcinogenesis and its potential role in modulating the signaling of platelet-derived growth factor receptor-α (PDGFRα). Genetic ablation of decorin in mice led to enhanced tumor prevalence and a higher tumor count compared with wild-type mice. These findings correlated with decreased levels of the cyclin-dependent kinase inhibitor p21(Waf1/Cip1) and concurrent activation (phosphorylation) of PDGFRα in the hepatocellular carcinomas generated in the decorin-null vis-à-vis wild-type mice. Notably, in normal liver PDGFRα localized primarily to the membrane of nonparenchymal cells, whereas in the malignant counterpart PDGFRα was expressed by the malignant cells at their cell surfaces. This process was facilitated by a genetic background lacking endogenous decorin. Double immunostaining of the proteoglycan and the receptor revealed only minor colocalization, leading to the hypothesis that decorin would bind to the natural ligand PDGF rather than to the receptor itself. Indeed, we found, using purified proteins and immune-blot assays, that decorin binds to PDGF. Collectively, our findings support the idea that decorin acts as a secreted tumor repressor during hepatocarcinogenesis by hindering the action of another receptor tyrosine kinase, such as the PDGFRα, and could be a novel therapeutic agent in the battle against liver cancer.

Biological interplay between proteoglycans and their innate immune receptors in inflammation

An emerging body of evidence indicates that secreted proteoglycans act as signaling molecules, in addition to their canonical function in maintaining and regulating the architecture of various extracellular matrices. Proteoglycans interact with a number of receptors that regulate growth, motility and immune response. In part, as a consequence of their complex structure, proteoglycans can induce crosstalk among various families of receptors and can also interact with natural receptor ligands, often blocking and sequestering their bioactivity. In their soluble form, originating from either partial proteolytic processing or through de novo synthesis by activated cells, some proteoglycans can become potent danger signals, denoting tissue stress and injury. Recently, it has been shown that proteoglycans, especially those belonging to the small leucine-rich and hyaluronan-binding gene families as well as the glycosaminoglycan hyaluronan, act as endogenous ligands of the toll-like receptors, a group of central receptors regulating innate immunity. Furthermore, proteoglycans can activate intracellular inflammasomes and trigger sterile inflammation. In this review, we critically assess the signaling events induced by the proteoglycans biglycan, decorin, lumican and versican as well as hyaluronan during inflammation. We discuss the intriguing emerging notion that, in spite of structural diversity of biglycan, decorin, versican and hyaluronan, all of them signal through the same toll-like receptors, albeit triggering differential responses and biological outcomes. Finally, we review the modes of action of these endogenous ligands of toll-like receptors and their ability to specifically modify the final signaling events and the inflammatory response.

Decorin induces rapid secretion of thrombospondin-1 in basal breast carcinoma cells via inhibition of Ras homolog gene family, member A/Rho-associated coiled-coil containing protein kinase 1

Pathological neovascularization relies on an imbalance between potent proangiogenic agents and equally effective antiangiogenic cues. Collectively, these factors contribute to an angiogenic niche within the tumor microenvironment. Oncogenic events and hypoxia contribute to augmented levels of angiokines, and thereby activate the so-called angiogenic switch to promote aggressive tumorigenic and metastatic growth. Soluble decorin functions as a paracrine pan-inhibitor of receptor tyrosine kinases, such as Met and epidermal growth factor receptor, and thus is capable of suppressing angiogenesis under normoxia. This leads to noncanonical repression of hypoxia-inducible factor 1-alpha and vascular endothelial growth factor A (VEGFA), and concurrent induction of thrombospondin-1. The substantial induction of endogenous tumor cell-derived thrombospondin-1, a potent antiangiogenic effector, led us to the discovery of an unexpected secretory phenotype occurring very rapidly (within 5 min) after decorin treatment of the triple-negative basal breast carcinoma cell line MDA-MB-231. Surprisingly, the effect was not mediated by Met receptor antagonism, as initially hypothesized, but required epidermal growth factor receptor signaling to achieve swift and robust thrombospondin-1 release. Furthermore, this effect was ultimately dependent on the prompt degradation of Ras homolog gene family member A, via the 26S proteasome, leading to direct inactivation of Rho-associated coiled-coil containing protein kinase 1. The latter led to derepression of thrombospondin-1 secretion. Collectively, these data provide a novel mechanistic role for Rho-associated coiled-coil containing protein kinase 1, in addition to providing the first conclusive evidence of decorin exclusively targeting a receptor tyrosine kinase to achieve a specific effect. The overall effects of soluble decorin on the tumor microenvironment would cause an immediately-early as well as a sustained antiangiogenic response in vivo.

Dichotomy of decorin activity on the insulin-like growth factor-I system

The stromal-specific proteoglycan decorin has emerged in recent years as a critical regulator of tumor initiation and progression. Decorin regulates the biology of various types of cancer by modulating the activity of several receptor tyrosine kinases coordinating growth, survival, migration, and angiogenesis. Decorin binds to surface receptors for epidermal growth factor and hepatocyte growth factor with high affinity, and negatively regulates their activity and signaling via robust internalization and eventual degradation. The insulin-like growth factor (IGF)-I system plays a critical role in the regulation of cell growth both in vivo and in vitro. The IGF-I receptor (IGF-IR) is also essential for cellular transformation, owing to its ability to enhance cell proliferation and protect cancer cells from apoptosis. Recent data have pointed to a role of decorin in regulating the IGF-I system in both nontransformed and transformed cells. Significantly, there is a surprising dichotomy in the mechanism of decorin action on IGF-IR signaling, which differs considerably between physiological and pathological cellular models. In this review, we summarize the current knowledge on decorin regulation of the IGF-I system in normal and transformed cells, and discuss possible decorin-based therapeutic approaches to target IGF-IR-driven tumors.

Human renal stem/progenitor cells repair tubular epithelial cell injury through TLR2-driven inhibin-A and microvesicle-shuttled decorin

Acute kidney injury (AKI) is emerging as a worldwide public health problem. Recent studies have focused on the possibility of using human adult renal stem/progenitor cells (ARPCs) to improve the repair of AKI. Here we studied the influence of ARPCs on the healing of cisplatin-injured renal proximal tubular epithelial cells. Tubular, but not glomerular, ARPCs provided a protective effect promoting proliferation of surviving tubular cells and inhibiting cisplatin-induced apoptosis. The recovery effect was specific to tubular ARPCs, occurred only after damage sensing, and was completely cancelled by TLR2 blockade on tubular ARPCs. Moreover, tubular, but not glomerular, ARPCs were resistant to the apoptotic effect of cisplatin. Tubular ARPCs operate mainly through the engagement of TLR2, the secretion of inhibin-A protein, and microvesicle-shuttled decorin, inhibin-A, and cyclin D1 mRNAs. These factors worked synergistically and were essential to the repair process. The involvement of tubular ARPC-secreted inhibin-A and decorin mRNA in the pathophysiology of AKI was also confirmed in transplant patients affected by delayed graft function. Hence, identification of this TLR2-driven recovery mechanism may shed light on new therapeutic strategies to promote the recovery capacity of the kidney in acute tubular damage. Use of these components, derived from ARPCs, avoids injecting stem cells.

The dermatan sulfate proteoglycan decorin modulates α2β1 integrin and the vimentin intermediate filament system during collagen synthesis

Decorin, a small leucine-rich proteoglycan harboring a dermatan sulfate chain at its N-terminus, is involved in regulating matrix organization and cell signaling. Loss of the dermatan sulfate of decorin leads to an Ehlers-Danlos syndrome characterized by delayed wound healing. Decorin-null (Dcn^−/−) mice display a phenotype similar to that of EDS patients. The fibrillar collagen phenotype of Dcn^−/− mice could be rescued in vitro by decorin but not with decorin lacking the glycosaminoglycan chain. We utilized a 3D cell culture model to investigate the impact of the altered extracellular matrix on Dcn^−/− fibroblasts. Using 2D gel electrophoresis followed by mass spectrometry, we identified vimentin as one of the proteins that was differentially upregulated by the presence of decorin. We discovered that a decorin-deficient matrix leads to abnormal nuclear morphology in the Dcn^−/− fibroblasts. This phenotype could be rescued by the decorin proteoglycan but less efficiently by the decorin protein core. Decorin treatment led to a significant reduction of the α2β1 integrin at day 6 in Dcn^−/− fibroblasts, whereas the protein core had no effect on β1. Interestingly, only the decorin core induced mRNA synthesis, phosphorylation and de novo synthesis of vimentin indicating that the proteoglycan decorin in the extracellular matrix stabilizes the vimentin intermediate filament system. We could support these results in vivo, because the dermis of wild-type mice have more vimentin and less β1 integrin compared to Dcn^−/−. Furthermore, the α2β1 null fibroblasts also showed a reduced amount of vimentin compared to wild-type. These data show for the first time that decorin has an impact on the biology of α2β1 integrin and the vimentin intermediate filament system. Moreover, our findings provide a mechanistic explanation for the reported defects in wound healing associated with the Dcn^−/− phenotype.

More than matrix: the multifaceted role of decorin in cancer

The small leucine-rich proteoglycan, decorin, has incrementally been shown to be a powerful inhibitor of growth in a wide variety of tumour cells, an effect specifically mediated by the interaction of decorin core protein with the epidermal growth factor receptor (EGFR) and other ErbB family proteins. Nowadays, this matrikine has become the main focus of various cancer studies. Decorin is an important component of the cellular microenvironment or extracellular matrix (ECM). Its interactions with matrix and cell membrane components have been implicated in many physiological and pathophysiological processes including matrix organisation, signal transduction, wound healing, cell migration, inhibition of metastasis, and angiogenesis. This review summarises recent findings on decorin's interactions and behaviour related to cancer. Highlighted are key functions of decorin such as interaction with cell surface receptors, as well as with ECM components, and the therapeutic potential of this multifunctional molecule.

Decorin protein core affects the global gene expression profile of the tumor microenvironment in a triple-negative orthotopic breast carcinoma xenograft model

Decorin, a member of the small leucine-rich proteoglycan gene family, exists and functions wholly within the tumor microenvironment to suppress tumorigenesis by directly targeting and antagonizing multiple receptor tyrosine kinases, such as the EGFR and Met. This leads to potent and sustained signal attenuation, growth arrest, and angiostasis. We thus sought to evaluate the tumoricidal benefits of systemic decorin on a triple-negative orthotopic breast carcinoma xenograft model. To this end, we employed a novel high-density mixed expression array capable of differentiating and simultaneously measuring gene signatures of both Mus musculus (stromal) and Homo sapiens (epithelial) tissue origins. We found that decorin protein core modulated the differential expression of 374 genes within the stromal compartment of the tumor xenograft. Further, our top gene ontology classes strongly suggests an unexpected and preferential role for decorin protein core to inhibit genes necessary for immunomodulatory responses while simultaneously inducing expression of those possessing cellular adhesion and tumor suppressive gene properties. Rigorous verification of the top scoring candidates led to the discovery of three genes heretofore unlinked to malignant breast cancer that were reproducibly found to be induced in several models of tumor stroma. Collectively, our data provide highly novel and unexpected stromal gene signatures as a direct function of systemic administration of decorin protein core and reveals a fundamental basis of action for decorin to modulate the tumor stroma as a biological mechanism for the ascribed anti-tumorigenic properties.

The biology of small leucine-rich proteoglycans in bone pathophysiology

The class of small leucine-rich proteoglycans (SLRPs) is a family of homologous proteoglycans harboring relatively small (36-42 kDa) protein cores compared with the larger cartilage and mesenchymal proteoglycans. SLRPs have been localized to most skeletal regions, with specific roles designated during all phases of bone formation, including periods relating to cell proliferation, organic matrix deposition, remodeling, and mineral deposition. This is mediated by key signaling pathways regulating the osteogenic program, including the activities of TGF-β, bone morphogenetic protein, Wnt, and NF-κB, which influence both the number of available osteogenic precursors and their subsequent development, differentiation, and function. On the other hand, SLRP depletion is correlated with degenerative diseases such as osteoporosis and ectopic bone formation. This minireview will focus on the SLRP roles in bone physiology and pathology.

The galactosaminoglycan-containing decorin and its impact on diseases

Decorin, a member of the small leucine-rich proteoglycans, is involved in many physiological and pathological processes. Decorin functions not only as structural molecule in organizing the extracellular matrix but also as signaling molecule controlling cell growth, morphogenesis and immunity. Mutations in decorin or alterations in the post-translational modifications of the glycosaminoglycan (GAG) chain lead to connective tissue disorders such as the congenital stromal corneal dystrophy and the Ehlers-Danlos syndrome. The summarized data reveal that decorin has a large impact on biological processes also because of the complex structure of the GAG chain. The complexity of decorin also covers the binding and sequestering of growth factors and their signaling. This shows that the decorin protein and the dermatan sulfate chain of decorin have both a structural function and a signaling function. Since defects in the biosynthesis of either the protein core or the GAG chain lead to structural alterations in the extracellular matrix and changes in the protein expression profile of the cells embedded in the matrix, this review focuses on the insights of structural function of decorin and includes data about dermatan sulfate.

Identification of decorin derived peptides with a zinc dependent anti-myostatin activity

Decorin is a member of the small leucine-rich proteoglycan family and it is a component of the extracellular matrix. Decorin was previously shown to bind different molecules, including myostatin, in a zinc-dependent manner. Here, we investigated in detail the anti-myostatin activity of decorin and fragments thereof. We show that this protein displays in vitro anti-myostatin activities with an IC(50) of 2.3 × 10(-8)M. After intramuscular injection of decorin in dystrophic mdx and γ-sarcoglycan(-/-) mice, we observed a significant increase of the muscle mass and this effect was maximal 18 days after administration. Further, we show that the myostatin-binding site is located in the N-terminal domain of decorin. In fact, a peptide encompassing the 31-71 sequence retains full myostatin binding capacity and intramuscular injection of the peptide induces muscle hypertrophy. The evaluation of three additional peptides suggests a crucial role of the four cysteines within the conserved CX3CXCX6C motif of class I of the small leucine-rich proteoglycans. Altogether, our results show that the N-terminal domain of decorin is sufficient for the binding to myostatin and they underscore the crucial role for this interaction of zinc and the cysteine cluster.

Decorin: a guardian from the matrix

Decorin, an archetypal member of the small leucine-rich proteoglycan gene family, has a broad binding repertoire that encompasses matrix structural components, such as collagens, and growth factors, particularly those that belong to the transforming growth factor-β ligand superfamily. Within the tumor microenvironment, stromal decorin has an inherent proclivity to directly bind and down-regulate several receptor tyrosine kinases, which are often overexpressed in cancer cells. The decorin interactome commands a powerful antitumorigenic signal by potently repressing and attenuating tumor cell proliferation, survival, migration, and angiogenesis. This collection of interacting molecules also regulates key downstream signaling processes indirectly via the sequestration of growth factors or directly via the antagonism of receptor tyrosine kinases. We propose that decorin can be considered a "guardian from the matrix" because of its innate ability to oppose pro-tumorigenic cues.