Glypican-3 inhibits Hedgehog signaling during development by competing with patched for Hedgehog binding

Convergent chemoenzymatic synthesis and biological evaluation of a heparan sulfate proteoglycan syndecan-1 mimetic

A new convergent chemoenzymatic synthesis strategy, integrating enzymatic synthesis of heparan sulfate, sortase A ligation, copper(i)-catalyzed alkyne-azide cycloaddition, and solid phase peptide synthesis, has been established to efficiently synthesize a mimetic of heparan sulfate proteoglycan syndecan-1 glyco-polypeptide at a milligram scale. The mimic was able to bind with αvβ3 integrin faster and exhibit stronger inhibition of breast cancer cell migration compared to the glycan or the polypeptide alone. This novel approach could serve as a general approach for heparan sulfate proteoglycan mimetic synthesis.

Emerging Roles of Heparan Sulfate Proteoglycans in Viral Pathogenesis

Heparan sulfate is a glycosaminoglycan present in nearly all mammalian tissues. Heparan sulfate moieties are attached to the cell surface via heparan sulfate proteoglycans (HSPGs) which are composed of a protein core bound to multiple heparan sulfate chains. HSPGs contribute to the structural integrity of the extracellular matrix and participate in cell signaling by releasing bound cytokines and chemokines once cleaved by an enzyme, heparanase. HSPGs are often exploited by viruses during infection, particularly during attachment and egress. Loss or inhibition of HSPGs initially during infection can yield significant decreases in viral entry and infectivity. In this review, we provide an overview of HSPGs in the lifecycle of multiple viruses, including herpesviruses, human immunodeficiency virus, dengue virus, human papillomavirus, and coronaviruses.

Generation of extracellular morphogen gradients: the case for diffusion

Cells within developing tissues rely on morphogens to assess positional information. Passive diffusion is the most parsimonious transport model for long-range morphogen gradient formation but does not, on its own, readily explain scaling, robustness and planar transport. Here, we argue that diffusion is sufficient to ensure robust morphogen gradient formation in a variety of tissues if the interactions between morphogens and their extracellular binders are considered. A current challenge is to assess how the affinity for extracellular binders, as well as other biophysical and cell biological parameters, determines gradient dynamics and shape in a diffusion-based transport system. Technological advances in genome editing, tissue engineering, live imaging and in vivo biophysics are now facilitating measurement of these parameters, paving the way for mathematical modelling and a quantitative understanding of morphogen gradient formation and modulation.

Prognostic impact of the glypican family of heparan sulfate proteoglycans on the survival of breast cancer patients

Purpose

Dysregulated expression of proteoglycans influences the outcome and progression of numerous cancers. Several studies have investigated the role of individual glypicans in cancer, however, the impact of the whole glypican family of heparan sulfate proteoglycans on prognosis of a large patient cohort of breast cancer patients has not yet been investigated. In the present study, our aim was to investigate the prognostic power of the glypicans in breast cancer patients.

Methods

We used a public database including both gene expression data and survival information for 3951 breast cancer patients to determine the prognostic value of glypicans on relapse-free survival using Cox regression analysis. Moreover, we performed quantitative Real-Time PCR to determine glypican gene expression levels in seven representative breast cancer cell lines.

Results

We found that high GPC3 levels were associated with a better prognosis in overall breast cancer patients. When stratified by hormone receptor status, we found that in worse prognosis subtypes low GPC1 levels correlate with a longer relapse-free survival, and in more favorable subtypes low GPC6 was associated with longer survival.

Conclusion

Our study concludes that glypicans could act as subtype-specific biomarkers for the prognosis of breast cancer patients and sparks hope for future research on glypicans possibly eventually providing targets for the treatment of the disease.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00432-021-03597-4.

Glypican-1, -3, -5 (GPC1, GPC3, GPC5) and Hedgehog Pathway Expression in Oral Squamous Cell Carcinoma

Proteoglycans are involved in tumor development and may regulate the Hedgehog (HH) pathway. This study aimed to investigate the gene and protein expression of glypican-1 (GPC1), -3 (GPC3), and -5 (GPC5) in oral squamous cell carcinoma (OSCC) and tumor-free lateral margins (TM) and their association with the HH pathway. Quantitative PCR was performed for GPC1, GPC3, GPC5, SHH, PTCH1, SMO, and GLI1 genes in samples of OSCC (n=31), TM (n=12), and non-neoplastic oral mucosa (NNM) of healthy patients (n=6), alongside an immunohistochemical evaluation of GPC1, GPC3, and GPC5 proteins and HH proteins SHH and glioma-associated oncogene homolog 1 (GLI1). Double staining for GPC3/SHH, GPC5/SHH, GPC3/tubulin [ac Lys40], GPC5/Tubulin [ac Lys40], and GPC5/GLI1 was also performed. Overexpression of GPC1 and GPC5 in tumor samples and underexpressed levels of GPC3 gene transcripts were observed when compared with TM (standard sample). HH pathway mRNA aberrant expression in OSCC samples and a negative correlation between GPC1 and GPC5 at transcription levels were detected. GPC1 staining was rare in OSCC, but positive cells were found in NNM and TM. Otherwise positive immunostaining for GPC3 and GPC5 was observed in OSCCs, but not in NNM and TM. Blood vessels adjacent to tumor islands were positive for GPC1 and GPC5. Co-localization of GPC3-positive and GPC5-positive cells with SHH and Tubulin [ac Lys40] proteins was noted, as well as of GPC5 and GLI1. The absence of the GPC1 protein in neoplastic cells, underexpression of the GPC3 gene, and co-localization of GPCs and HH proteins may indicate the maintenance of aberrant HH pathway activation in OSCC.

Association between microRNA-527 and glypican-3 in hepatocellular carcinoma

The present study aimed to identify the specific microRNAs (miRNAs/miRs) and their corresponding target genes involved in hepatocellular carcinomas (HCCs). Microarray analysis was performed to examine the miRNA expression profiles of four paired HCC and corresponding non-cancerous (N) liver tissues using 985 miRNA probes. The Human miRNA Target database was used to identify the target genes of differentially expressed miRNAs between the HCC and N tissues. The protein expression levels of target genes in the HCC tissues and cell lines were evaluated using western blotting. miRNA-mediated suppression of target gene expression was evaluated by transiently transfecting the miRNA into the HCC cell lines. Of the 985 miRNAs evaluated, four miRNAs were differentially expressed (three upregulated and one downregulated miRNAs). Of these four miRNAs, miRNA-527 was highly downregulated in the HCC tissues. Glypican-3 (GPC-3) was predicted as a target gene of miRNA-527. Western blotting revealed that GPC-3 protein is highly expressed in the HCC tissues and HCC cell lines compared with N and normal cell lines. Transfection with miR-527 resulted in suppression of GPC-3 protein expression in the Cos7 cells. Furthermore, transfection with miR-527 also inhibited the intrinsic expression of GPC-3 in the Huh-7 cell line. This indicated that miR-527 in the HCC tissues may be an important novel miRNA that targets the GPC-3 gene expression. GPC-3, whose expression is regulated by miR-527, may be involved in the development and progression of HCC.

Proteoglycans as Mediators of Cancer Tissue Mechanics

Proteoglycans are a diverse group of molecules which are characterized by a central protein backbone that is decorated with a variety of linear sulfated glycosaminoglycan side chains. Proteoglycans contribute significantly to the biochemical and mechanical properties of the interstitial extracellular matrix where they modulate cellular behavior by engaging transmembrane receptors. Proteoglycans also comprise a major component of the cellular glycocalyx to influence transmembrane receptor structure/function and mechanosignaling. Through their ability to initiate biochemical and mechanosignaling in cells, proteoglycans elicit profound effects on proliferation, adhesion and migration. Pathologies including cancer and cardiovascular disease are characterized by perturbed expression of proteoglycans where they compromise cell and tissue behavior by stiffening the extracellular matrix and increasing the bulkiness of the glycocalyx. Increasing evidence indicates that a bulky glycocalyx and proteoglycan-enriched extracellular matrix promote malignant transformation, increase cancer aggression and alter anti-tumor therapy response. In this review, we focus on the contribution of proteoglycans to mechanobiology in the context of normal and transformed tissues. We discuss the significance of proteoglycans for therapy response, and the current experimental strategies that target proteoglycans to sensitize cancer cells to treatment.

Assembling custom side chains on proteoglycans to interrogate their function in living cells

Proteoglycans (PGs) are composed of a core protein and one or more chains of glycosaminoglycans (GAGs). The highly heterogeneous GAG chains play an irreplaceable role in the functions of PGs. However, the lack of an approach to control the exact structure of GAG chains conjugated to PGs tremendously hinders functional studies of PGs. Herein, by using glypican-3 as a model, we establish an aldehyde tag-based approach to assemble PGs with specific GAG chains on the surface of living cells. We show that the engineered glypican-3 can regulate Wnt and Hedgehog signaling like the wild type. Furthermore, we also present a method for studying the interaction of PGs with their target glycoproteins by combining the assembly of PGs carrying specific GAG chains with metabolic glycan labeling, and most importantly, we obtain evidence of GPC3 directly interacting with Frizzled. In conclusion, this study provides a very useful platform for structural and functional studies of PGs with specific GAG chains.

Currently, it is not possible to generate proteoglycans displaying glycosaminoglycan chains with specific structures. Here the authors show that by using an aldehyde tag-based methodology it is possible to insert these specific chains onto proteoglycans expressed on the cell surface.

Cell-surface heparan sulfate proteoglycans as multifunctional integrators of signaling in cancer

Proteoglycans (PGs) represent a large proportion of the components that constitute the extracellular matrix (ECM). They are a diverse group of glycoproteins characterized by a covalent link to a specific glycosaminoglycan type. As part of the ECM, heparan sulfate (HS)PGs participate in both physiological and pathological processes including cell recruitment during inflammation and the promotion of cell proliferation, adhesion and motility during development, angiogenesis, wound repair and tumor progression. A key function of HSPGs is their ability to modulate the expression and function of cytokines, chemokines, growth factors, morphogens, and adhesion molecules. This is due to their capacity to act as ligands or co-receptors for various signal-transducing receptors, affecting pathways such as FGF, VEGF, chemokines, integrins, Wnt, notch, IL-6/JAK-STAT3, and NF-κB. The activation of those pathways has been implicated in the induction, progression, and malignancy of a tumor. For many years, the study of signaling has allowed for designing specific drugs targeting these pathways for cancer treatment, with very positive results. Likewise, HSPGs have become the subject of cancer research and are increasingly recognized as important therapeutic targets. Although they have been studied in a variety of preclinical and experimental models, their mechanism of action in malignancy still needs to be more clearly defined. In this review, we discuss the role of cell-surface HSPGs as pleiotropic modulators of signaling in cancer and identify them as promising markers and targets for cancer treatment.

The Role of Glypicans in Cancer Progression and Therapy

Glypicans are a family of heparan sulfate proteoglycans that are attached to the cell membrane via a glycosylphosphatidylinositol anchor. Glypicans interact with multiple ligands, including morphogens, growth factors, chemokines, ligands, receptors, and components of the extracellular matrix through their heparan sulfate chains and core protein. Therefore, glypicans can function as coreceptors to regulate cell proliferation, cell motility, and morphogenesis. In addition, some glypicans are abnormally expressed in cancers, possibly involved in tumorigenesis, and have the potential to be cancer-specific biomarkers. Here, we provide a brief review focusing on the expression of glypicans in various cancers and their potential to be targets for cancer therapy.

Development of Glypican-3 Targeting Immunotoxins for the Treatment of Liver Cancer: An Update

Hepatocellular carcinoma (HCC) accounts for most liver cancers and represents one of the deadliest cancers in the world. Despite the global demand for liver cancer treatments, there remain few options available. The U.S. Food and Drug Administration (FDA) recently approved Lumoxiti, a CD22-targeting immunotoxin, as a treatment for patients with hairy cell leukemia. This approval helps to demonstrate the potential role that immunotoxins can play in the cancer therapeutics pipeline. However, concerns have been raised about the use of immunotoxins, including their high immunogenicity and short half-life, in particular for treating solid tumors such as liver cancer. This review provides an overview of recent efforts to develop a glypican-3 (GPC3) targeting immunotoxin for treating HCC, including strategies to deimmunize immunotoxins by removing B- or T-cell epitopes on the bacterial toxin and to improve the serum half-life of immunotoxins by incorporating an albumin binding domain.

Dlp-mediated Hh and Wnt signaling interdependence is critical in the niche for germline stem cell progeny differentiation

Although multiple signaling pathways work synergistically in various niches to control stem cell self-renewal and differentiation, it remains poorly understood how they cooperate with one another molecularly. In the Drosophila ovary, Hh and Wnt pathways function in the niche to promote germline stem cell (GSC) progeny differentiation. Here, we show that glypican Dlp-mediated Hh and Wnt signaling interdependence operates in the niche to promote GSC progeny differentiation by preventing BMP signaling. Hh/Wnt-mediated dlp repression is essential for their signaling interdependence in niche cells and for GSC progeny differentiation by preventing BMP signaling. Mechanistically, Hh and Wnt downstream transcription factors directly bind to the same dlp regulatory region and recruit corepressors composed of transcription factor Croc and Egg/H3K9 trimethylase to repress Dlp expression. Therefore, our study reveals a novel mechanism for Hh/Wnt signaling-mediated direct dlp repression and a novel regulatory mechanism for Dlp-mediated Hh/Wnt signaling interdependence in the GSC differentiation niche.

Association of common variation in ADD3 and GPC1 with biliary atresia susceptibility

Biliary atresia (BA) is an idiopathic neonatal cholestatic disease. Recent genome-wide association study (GWAS) revealed that common variation of ADD3, GPC1, ARF6, and EFEMP1 gene was associated with BA susceptibility. We aimed to evaluate the association of these genes with BA in Chinese population. Twenty single nucleotide polymorphisms (SNPs) in these four genes were genotyped in 340 BA patients and 1,665 controls. Three SNPs in ADD3 were significantly associated with BA, and rs17095355 was the top SNP (P_Allele = 3.23×10^-6). Meta-analysis of published data and current data indicated that rs17095355 was associated with BA susceptibility in Asians and Caucasians. Three associated SNPs were expression quantitative trait loci (eQTL) for ADD3. Two GPC1 SNPs in high linkage disequilibrium (LD) showed nominal association with BA susceptibility (P_Allele = 0.03 for rs6707262 and P_Allele = 0.04 for rs6750380), and were eQTL of GPC1. Haplotype harboring these two SNPs almost reached the study-wide significance (P = 0.0035). No association for ARF6 and EFEMP1 was found with BA risk in the current population. Our study validated associations of ADD3 and GPC1 SNPs with BA risk in Chinese population and provided evidence of epistatic contributions of genetic factors to BA susceptibility.

A Membranome-Centered Approach Defines Novel Biomarkers for Cellular Subtypes in the Intervertebral Disc

OBJECTIVE

Lack of specific marker-sets prohibits definition and functional distinction of cellular subtypes in the intervertebral disc (IVD), such as those from the annulus fibrosus (AF) and the nucleus pulposus (NP).

DESIGN

We recently generated immortalized cell lines from human NP and AF tissues; these comprise a set of functionally distinct clonal subtypes. Whole transcriptome analyses were performed of 12 phenotypically distinct clonal cell lines (4× NP-Responder, 4× NP-nonResponder, 2× AF-Sheet forming, and 2× AF-nonSheet forming). Data sets were filtered for membrane-associated marker genes and compared to literature.

RESULTS

Comparison of our immortal cell lines to published primary NP, AF, and articular chondrocytes (AC) transcriptome datasets revealed preservation of AF and NP phenotypes. NP-specific membrane-associated genes were defined by comparison to AF cells in both the primary dataset (46 genes) and immortal cell-lines (161 genes). Definition of AF-specific membrane-associated genes yielded 125 primary AF cell and 92 immortal cell-line markers. Overlap between primary and immortal NP cells yielded high-confidence NP-specific marker genes for NP-R (CLDN11, TMEFF2, CA12, ANXA2, CD44) and NP-nR (EFNA1, NETO2, SLC2A1). Overlap between AF and immortal AF subtypes yielded specific markers for AF-S (COLEC12, LPAR1) and AF-nS (CHIC1).

CONCLUSIONS

The current study provides a reference platform for preclinical evaluation of novel membrane-associated cell type-specific markers in the IVD. Future research will focus on their biological relevance for IVD function in development, homeostasis, and degenerate conditions.

MetaOmGraph: a workbench for interactive exploratory data analysis of large expression datasets

The diverse and growing omics data in public domains provide researchers with tremendous opportunity to extract hidden, yet undiscovered, knowledge. However, the vast majority of archived data remain unused. Here, we present MetaOmGraph (MOG), a free, open-source, standalone software for exploratory analysis of massive datasets. Researchers, without coding, can interactively visualize and evaluate data in the context of its metadata, honing-in on groups of samples or genes based on attributes such as expression values, statistical associations, metadata terms and ontology annotations. Interaction with data is easy via interactive visualizations such as line charts, box plots, scatter plots, histograms and volcano plots. Statistical analyses include co-expression analysis, differential expression analysis and differential correlation analysis, with significance tests. Researchers can send data subsets to R for additional analyses. Multithreading and indexing enable efficient big data analysis. A researcher can create new MOG projects from any numerical data; or explore an existing MOG project. MOG projects, with history of explorations, can be saved and shared. We illustrate MOG by case studies of large curated datasets from human cancer RNA-Seq, where we identify novel putative biomarker genes in different tumors, and microarray and metabolomics data from Arabidopsis thaliana. MOG executable and code: http://metnetweb.gdcb.iastate.edu/ and https://github.com/urmi-21/MetaOmGraph/.

Glypican-3: A New Target for Diagnosis and Treatment of Hepatocellular Carcinoma

Liver cancer is the second leading cause of cancer-related deaths worldwide, and hepatocellular carcinoma is the most common type. The pathogenesis of hepatocellular carcinoma is concealed, its progress is rapid, its prognosis is poor, and the mortality rate is high. Therefore, novel molecular targets for hepatocellular carcinoma early diagnosis and development of targeted therapy are critically needed. Glypican-3, a cell-surface glycoproteins in which heparan sulfate glycosaminoglycan chains are covalently linked to a protein core, is overexpressed in HCC tissues but not in the healthy adult liver. Thus, Glypican-3 is becoming a promising candidate for liver cancer diagnosis and immunotherapy. Up to now, Glypican-3 has been a reliable immunohistochemical marker for hepatocellular carcinoma diagnosis, and soluble Glypican-3 in serum has becoming a promising marker for liquid biopsy. Moreover, various immunotherapies targeting Glypican-3 have been developed, including Glypican-3 vaccines, anti- Glypican-3 immunotoxin and chimeric-antigen-receptor modified cells. In this review, we summarize and analyze the structure and physicochemical properties of Glypican-3 molecules, then review their biological functions and applications in clinical diagnosis, and explore the diagnosis and treatment strategies based on Glypican-3.

Heparanase: A Potential Therapeutic Target in Sarcomas

Sarcomas comprise a heterogeneous group of rare malignancies of mesenchymal origin including more than 70 subtypes. They may arise in muscle, bone, cartilage and other connective tissues. Their high histological and genetic heterogeneity makes diagnosis and treatment very challenging. Deregulation of heparanase has been found in several sarcoma subtypes and high expression levels have been correlated with poor prognosis in Ewing's sarcoma and osteosarcoma. Altered expression of specific heparan sulfate proteoglycans and heparan sulfate biosynthetic enzymes has also been observed. Advances in molecular pathogenesis of sarcomas have evidenced the critical role of several heparan sulfate binding growth factors and receptor tyrosine kinases, highly interconnected with the microenvironment, in sustaining tumor growth and progression. Interference with heparanase/heparan sulfate functions represents a potential therapeutic approach in sarcoma. In this chapter, we summarize the current knowledge about the biological significance of heparanase expression and its potential as a therapeutic target in subtypes of both soft tissue and bone sarcomas. Particular emphasis is given to the involvement of heparan sulfate proteoglycans and their synthesizing and modifying enzymes in bone physiology and disorders leading up to the pathobiology of bone sarcomas. The chapter also describes the cooperation between exostin loss-of-function and heparanase upregulation in hereditary Multiple Osteochondroma syndrome as a paradigmatic example of constitutive alteration of the heparanase/heparan sulfate proteoglycan system which may contribute to progression to malignant secondary chondrosarcoma. Preclinical evidence of the role of heparanase as a promising therapeutic target in various sarcoma subtypes is finally resumed.

Glypican-6 stimulates intestinal elongation by simultaneously regulating Hedgehog and non-canonical Wnt signaling

We report here that Glypican-6 (GPC6)-null mice display at birth small intestines that are 75% shorter than those of normal littermates. Notably, we demonstrate that the role of GPC6 in intestinal elongation is mediated by both Hedgehog (Hh) and non-canonical Wnt signaling. Based on results from in vitro experiments, we had previously proposed that GPC6 stimulates Hh signaling by interacting with Hh and Patched1 (Ptc1), and facilitating/stabilizing their interaction. Here we provide strong support to this hypothesis by showing that GPC6 binds to Ptc1 in the mesenchymal layer of embryonic intestines. This study also provides experimental evidence that strongly suggests that GPC6 inhibits the activity of Wnt5a on the intestinal epithelium by binding to this growth factor, and reducing its release from the surrounding mesenchymal cells. Finally, we show that whereas the mesenchymal layer of GPC6-null intestines displays reduced cell proliferation and a thinner smooth muscle layer, epithelial cell differentiation is not altered in the mutant gut.

Hedgehog Signal and Genetic Disorders

The hedgehog (Hh) family comprises sonic hedgehog (Shh), Indian hedgehog (Ihh), and desert hedgehog (Dhh), which are versatile signaling molecules involved in a wide spectrum of biological events including cell differentiation, proliferation, and survival; establishment of the vertebrate body plan; and aging. These molecules play critical roles from embryogenesis to adult stages; therefore, alterations such as abnormal expression or mutations of the genes involved and their downstream factors cause a variety of genetic disorders at different stages. The Hh family involves many signaling mediators and functions through complex mechanisms, and achieving a comprehensive understanding of the entire signaling system is challenging. This review discusses the signaling mediators of the Hh pathway and their functions at the cellular and organismal levels. We first focus on the roles of Hh signaling mediators in signal transduction at the cellular level and the networks formed by these factors. Then, we analyze the spatiotemporal pattern of expression of Hh pathway molecules in tissues and organs, and describe the phenotypes of mutant mice. Finally, we discuss the genetic disorders caused by malfunction of Hh signaling-related molecules in humans.

Simpson-Golabi-Behmel syndrome type 1 with subclinical hypothyroidism: A case report

RATIONALE

Simpson-Golabi-Behmel syndrome type 1 (SGBS1) is caused by mutations in GPC3 or in both GPC3 and GPC4. Physical manifestations of SGBS1 include fetal overgrowth and macrostomia, macroglossia. Subclinical hypothyroidism has never been reported in SGBS1 cases.

PATIENT CONCERNS

An 8-days-old boy was referred to our hospital with persistent hypoglycemia and special facies. And the infant showed elevated levels of thyroid-stimulating hormone (TSH). Free T4 and free T3 were normal.

DIAGNOSES

Definitive diagnosis of SGBS1 depends on clinical features and genetic testing. A nonsense mutation (c.1515C > A, p. Cys505*) was tested by whole-exome sequencing.

INTERVENTIONS

Normal blood glucose levels were maintained with glucose infusions. Levothyroxine was given to the patient for treating subclinical hypothyroidism.

OUTCOMES

The parents decided to abandon the treatment of the patient. We learned that the patient died of a lung infection by a telephone follow-up.

LESSONS

Subclinical hypothyroidism could be added to the known clinical manifestations of SGBS1.

Identification and characterization of a novel heparan sulfate-binding domain in Activin A longest variants and implications for function

Activins regulate numerous processes including inflammation and are synthesized as precursors consisting of a long N-terminal pro-region and a mature protein. Genomic human databases currently list three activin A (Act A) variants termed X1, X2 and X3. The X3 variant is the shortest, lacks N-terminal segments present in X1 and X2, and has been the focus of most past literature. Here, we asked whether these variants are expressed by human cells and tissues and what structural features are contained within their pro-regions. Human monocytic-like cells THP1 and U937 expressed X1 and X2 variants after exposure to phorbol ester or granulocyte-macrophage colony-stimulating factor, while X2 transcripts were present in placenta. Expression vectors encoding full length X2 or X3 variants resulted in production and secretion of biologically active Act A from cultured cells. Previous studies reported a putative HS-binding domain (HBD) in the X3 pro-region. Here, we identified a novel HBD with consensus HS-binding motifs near the N-terminal end of X1 and X2 pro-regions. Peptides encompassing this new domain interacted with substrate-bound HS with nanomolar affinity, while peptides from putative X3 HBD did not. In good agreement, full length X2 pro-region interacted with heparin-agarose, while the X3 pro-region did not. In sum, our study reveals that Act A variants are expressed by inflammatory cells and placenta and yield biological activity. The high affinity HBD in X1 and X2 pro-region and its absence in X3 could greatly influence overall Act A distribution, availability and activity in physiological and pathological circumstances.

Yttrium-90-Labeled Anti-Glypican 3 Radioimmunotherapy Halts Tumor Growth in an Orthotopic Xenograft Model of Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is the second most lethal malignancy globally and is increasing in incidence in the United States. Unfortunately, there are few effective systemic treatment options, particularly for disseminated disease. Glypican-3 (GPC3) is a proteoglycan cell surface receptor overexpressed in most HCCs and provides a unique target for molecular therapies. We have previously demonstrated that PET imaging using a 89Zr-conjugated monoclonal anti-GPC3 antibody (αGPC3) can bind to minute tumors and allow imaging with high sensitivity and specificity in an orthotopic xenograft mouse model of HCC and that serum alpha-fetoprotein (AFP) levels are highly correlated with tumor size in this model. In the present study, we conjugated 90Y, a high-energy beta-particle-emitting radionuclide, to our αGPC3 antibody to develop a novel antibody-directed radiotherapeutic approach for HCC. Luciferase-expressing HepG2 human hepatoblastoma cells were orthotopically implanted in the livers of athymic nude mice, and tumor establishment was verified at 6 weeks after implantation by bioluminescent imaging and serum AFP concentration. Tumor burden by bioluminescence and serum AFP concentration was highly correlated in our model. Yttrium-90 was conjugated to αGPC3 using the chelating agent 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) and injected via the tail vein into the experimental mice at a dose of 200 μCi/mouse or 300 μCi/mouse. Control mice received DOTA-αGPC3 without radionuclide. At 30 days after a single dose of the radioimmunotherapy agent, mean serum AFP levels in control animals increased dramatically, while animals treated with 200 μCi only experienced a minor increase, indicating cessation of tumor growth, and animals treated with 300 μCi experienced a reduction in serum AFP concentration, indicating tumor shrinkage. Mean tumor-bearing liver weight in control animals was also significantly greater than that in animals that received either dose of 90Y-αGPC3. These results were achieved without significant toxicity as measured by body condition scoring and body weight. The results of this preclinical pilot demonstrate that GPC3 can be used as a target for radioimmunotherapy in an orthotopic mouse model of HCC and may be a target of clinical significance, particularly for disseminated HCC.

Glypican 3-Targeted Therapy in Hepatocellular Carcinoma

Glypican-3 (GPC3) is an oncofetal glycoprotein attached to the cell membrane by a glycophosphatidylinositol anchor. GPC3 is overexpressed in some kinds of tumors, particularly hepatocellular carcinoma (HCC). The prognostic significance of serum GPC3 levels and GPC3 immunoreactivity in tumor cells has been defined in patients with HCC. In addition to its usefulness as a biomarker, GPC3 has attracted attention as a novel therapeutic target molecule, and clinical trials targeting GPC3 are in progress. The major mechanism of anti-GPC3 antibody (GPC3Ab) against cancer cells is antibody-dependent cellular cytotoxicity and/or complement-dependent cytotoxicity. Since GPC3Ab is associated with immune responses, a combination of protocols with immune checkpoint inhibitors has also been investigated. Moreover, some innovative approaches for GPC3-targeting therapy have emerged in recent years. This review introduces the results of recent clinical trials targeting GPC3 in HCC and summarizes the latest knowledge regarding the role of GPC3 in HCC progression and clinical application targeting GPC3.

Heparan sulfate proteoglycans: The sweet side of development turns sour in mucopolysaccharidoses

Heparan sulfate proteoglycans (HSPGs) are complex carbohydrate-modified proteins ubiquitously expressed on cell surfaces, extracellular matrix and basement membrane of mammalian tissues. Beside to serve as structural constituents, they regulate multiple cellular activities. A critical involvement of HSPGs in development has been established, and perturbations of HSPG-dependent pathways are associated with many human diseases. Recent evidence suggest a role of HSPGs in the pathogenesis of mucopolysaccharidoses (MPSs) where the accumulation of undigested HS results in the loss of cellular functions, tissue damage and organ dysfunctions accounting for clinical manifestations which include central nervous system (CNS) involvement, degenerative joint disease and reduced bone growth. Current therapies are not curative but only ameliorate the disease symptoms. Here, we highlight the link between HSPG functions in the development of CNS and musculoskeletal structures and the etiology of some MPS phenotypes, suggesting that HSPGs may represent potential targets for the therapy of such incurable diseases.

Therapeutic Potential of Neurotrophins for Repair After Brain Injury: A Helping Hand From Biomaterials

Stroke remains the leading cause of long-term disability with limited options available to aid in recovery. Significant effort has been made to try and minimize neuronal damage following stroke with use of neuroprotective agents, however, these treatments have yet to show clinical efficacy. Regenerative interventions have since become of huge interest as they provide the potential to restore damaged neural tissue without being limited by a narrow therapeutic window. Neurotrophins, such as brain-derived neurotrophic factor (BDNF), and their high affinity receptors are actively produced throughout the brain and are involved in regulating neuronal activity and normal day-to-day function. Furthermore, neurotrophins are known to play a significant role in both protection and recovery of function following neurodegenerative diseases such as stroke and traumatic brain injury (TBI). Unfortunately, exogenous administration of these neurotrophins is limited by a lack of blood-brain-barrier (BBB) permeability, poor half-life, and rapid degradation. Therefore, we have focused this review on approaches that provide a direct and sustained neurotrophic support using pharmacological therapies and mimetics, physical activity, and potential drug delivery systems, including discussion around advantages and limitations for use of each of these systems. Finally, we discuss future directions of biomaterial drug-delivery systems, including the incorporation of heparan sulfate (HS) in conjunction with neurotrophin-based interventions.

The Role of Glypican-3 in Regulating Wnt, YAP, and Hedgehog in Liver Cancer

Glypican-3 (GPC3) is a cell-surface glycoprotein consisting of heparan sulfate glycosaminoglycan chains and an inner protein core. It has important functions in cellular signaling including cell growth, embryogenesis, and differentiation. GPC3 has been linked to hepatocellular carcinoma and a few other cancers, however, the mechanistic role of GPC3 in cancer development remains elusive. Recent breakthroughs including the structural modeling of GPC3 and GPC3-Wnt complexes represent important steps toward deciphering the molecular mechanism of action for GPC3 and how it may regulate cancer signaling and tumor growth. A full understanding of the molecular basis of GPC3-mediated signaling requires elucidation of the dynamics of partner receptors, transducer complexes, and downstream players. Herein, we summarize current insights into the role of GPC3 in regulating cancer development through Wnt and other signaling pathways, including YAP and hedgehog cascades. We also highlight the growing body of work which underlies deciphering how GPC3 is a key player in liver oncogenesis.

Whole exome sequencing aids the diagnosis of Simpson-Golabi-Behmel syndrome in two male fetuses

Objective

To diagnose and explore the genetic aetiology of Simpson–Golabi–Behmel syndrome type 1 (SGBS1) in two male fetuses.

Methods

Prenatal ultrasound scans and further genetic analysis using karyotype analysis, chromosomal microarray analysis, whole exome sequencing (WES) and Sanger sequencing were conducted.

Results

Prenatal ultrasound scans of two fetuses showed multiple congenital anomalies and hydramnios. Subsequent to termination of the pregnancies, a novel nonsense variant (c.892G>T, p.E298*) in the glypican 3 (GPC3) gene of the two fetuses was identified by WES and further confirmed by Sanger sequencing. The two fetuses were diagnosed with SGBS1. The mother was heterozygous for the c.892G>T variant.

Conclusion

This study describes the prenatal sonographic features of SGBS1, emphasizes the role of WES in the diagnosis of SGBS1 and expands the known mutation spectrum of the GPC3 gene.

Loss of the Heparan Sulfate Proteoglycan Glypican5 Facilitates Long-Range Sonic Hedgehog Signaling

As a morphogen, Sonic Hedgehog (Shh) mediates signaling at a distance from its sites of synthesis. After secretion, Shh must traverse a distance through the extracellular matrix (ECM) to reach the target cells and activate the Hh response. ECM proteins, in particular, the heparan sulfate proteoglycans (HSPGs) of the glypican family, have both negative and positive effects on Shh signaling, all attributed to their ability to bind Shh. Using mouse embryonic stem cell-derived mosaic tissues with compartments that lack the glycosyltransferases Exostosin1 and Exostosin2, or the HSPG core protein Glypican5, we show that Shh accumulates around its source cells when they are surrounded by cells that have a mutated ECM. This accumulation of Shh is correlated with an increased noncell autonomous Shh response. Our results support a model in which Shh presented on the cell surface accumulates at or near ECM that lacks HSPGs, possibly due to the absence of these Shh sequestering molecules. Stem Cells 2019;37:899-909.

Role of glypicans in regulation of the tumor microenvironment and cancer progression

Glypicans are evolutionary conserved, cell surface heparan sulfate (HS) proteoglycans that are attached to the cell membrane via a glycosylphosphatidylinositol (GPI) anchor. Glypicans interact with a broad class of soluble and insoluble ligands, such as morphogens, growth factors, chemokines, receptors and components of the extracellular matrix (ECM). Such versatility comes from their ability to interact through both their HS chains and core protein. Glypicans are involved in cellular and tissue development, morphogenesis and cell motility. They exhibit differential expression in several cancers, acting as both tumor promoters and inhibitors in a cancer type-specific manner. They also influence tumor stroma by facilitating angiogenesis, ECM remodeling and alteration of immune cell functions. Glypicans have emerged as a new therapeutic moiety, whose functions can be exploited in the field of targeted therapies and precision medicine in cancer. This is demonstrated by the emergence of several anti-glypican antibody-based immunologics that have been recently developed and are being evaluated in clinical trials. This review will focus on glypican structure and function with an emphasis on their expression in various cancers. Discussion will also center on the potential of glypicans to be therapeutic targets for inhibition of cancer cell growth.

Glycosylphosphatidylinositol biosynthesis and remodeling are required for neural tube closure, heart development, and cranial neural crest cell survival

Glycosylphosphatidylinositol (GPI) anchors attach nearly 150 proteins to the cell membrane. Patients with pathogenic variants in GPI biosynthesis genes develop diverse phenotypes including seizures, dysmorphic facial features and cleft palate through an unknown mechanism. We identified a novel mouse mutant (cleft lip/palate, edema and exencephaly; Clpex) with a hypo-morphic mutation in Post-Glycophosphatidylinositol Attachment to Proteins-2 (Pgap2), a component of the GPI biosynthesis pathway. The Clpex mutation decreases surface GPI expression. Surprisingly, Pgap2 showed tissue-specific expression with enrichment in the brain and face. We found the Clpex phenotype is due to apoptosis of neural crest cells (NCCs) and the cranial neuroepithelium. We showed folinic acid supplementation in utero can partially rescue the cleft lip phenotype. Finally, we generated a novel mouse model of NCC-specific total GPI deficiency. These mutants developed median cleft lip and palate demonstrating a previously undocumented cell autonomous role for GPI biosynthesis in NCC development.

Overgrowth syndromes - clinical and molecular aspects and tumour risk

Overgrowth syndromes are a heterogeneous group of rare disorders characterized by generalized or segmental excessive growth commonly associated with additional features, such as visceromegaly, macrocephaly and a large range of various symptoms. These syndromes are caused by either genetic or epigenetic anomalies affecting factors involved in cell proliferation and/or the regulation of epigenetic markers. Some of these conditions are associated with neurological anomalies, such as cognitive impairment or autism. Overgrowth syndromes are frequently associated with an increased risk of cancer (embryonic tumours during infancy or carcinomas during adulthood), but with a highly variable prevalence. Given this risk, syndrome-specific tumour screening protocols have recently been established for some of these conditions. Certain specific clinical traits make it possible to discriminate between different syndromes and orient molecular explorations to determine which molecular tests to conduct, despite the syndromes having overlapping clinical features. Recent advances in molecular techniques using next-generation sequencing approaches have increased the number of patients with an identified molecular defect (especially patients with segmental overgrowth). This Review discusses the clinical and molecular diagnosis, tumour risk and recommendations for tumour screening for the most prevalent generalized and segmental overgrowth syndromes.

Novel immunotherapeutic approaches for hepatocellular carcinoma treatment

INTRODUCTION

The introduction of immune checkpoint inhibitors has been lately proposed for the treatment of hepatocellular carcinoma (HCC) with respect to other cancer types. Several immunotherapeutic approaches are now under evaluation for HCC treatment including: i) antibodies acting as immune checkpoint inhibitors; ii) antibodies targeting specific tumor-associated antigens; iii) chimeric antigen receptor redirected T (CAR-T) cells targeting specific tumor-associated antigens; iv) vaccination strategies with tumor-specific epitopes. Areas covered: The review provides a wide description of the clinical trials investigating the efficacy of the main immunotherapeutic approaches proposed for the treatment of patients affected by HCC. Expert opinion: The balancing between immunostimulative and immunosuppressive factors in the context of HCC tumor microenvironment results in heterogeneous response rates to immunotherapeutic approaches such as checkpoint inhibitors, among HCC patients. In this context, it becomes crucial the identification of predictive factors determining the treatment response. A multiple approach using different biomarkers could be useful to identify the subgroup of HCC patients responsive to the treatment with a checkpoint inhibitor (as an example, nivolumab) as single agent, and to identify those patients in which other treatment regimens, such as the combination with sorafenib, or with locoregional therapies, could be more effective.

The extracellular matrix as a multitasking player in disease

Extracellular matrices (ECMs) are highly specialized and dynamic three-dimensional (3D) scaffolds into which cells reside in tissues. ECM is composed of a variety of fibrillar components, such as collagens, fibronectin, and elastin, and non-fibrillar molecules as proteoglycans, hyaluronan, and glycoproteins including matricellular proteins. These macromolecular components are interconnected forming complex networks that actively communicate with cells through binding to cell surface receptors and/or matrix effectors. ECMs exert diverse roles, either providing tissues with structural integrity and mechanical properties essential for tissue functions or regulating cell phenotype and functions to maintain tissue homeostasis. ECM molecular composition and structure vary among tissues, and is markedly modified during normal tissue repair as well as during the progression of various diseases. Actually, abnormal ECM remodeling occurring in pathologic circumstances drives disease progression by regulating cell-matrix interactions. The importance of matrix molecules to normal tissue functions is also highlighted by mutations in matrix genes that give rise to genetic disorders with diverse clinical phenotypes. In this review, we present critical and emerging issues related to matrix assembly in tissues and the multitasking roles for ECM in diseases such as osteoarthritis, fibrosis, cancer, and genetic diseases. The mechanisms underlying the various matrix-based diseases are also discussed. Research focused on the highly dynamic 3D ECM networks will help to discover matrix-related causative abnormalities of diseases as well as novel diagnostic tools and therapeutic targets.

Structure, function and disease relevance of Wnt inhibitory factor 1, a secreted protein controlling the Wnt and hedgehog pathways

Wnts and Hedgehogs (Hh) are large, lipid-modified extracellular morphogens that play key roles in embryonic development and stem cell proliferation of Metazoa. Both morphogens signal through heptahelical Frizzled-type receptors of the G-Protein Coupled Receptor family and there are several other similarities that suggest a common evolutionary origin of the Hh and Wnt pathways. There is evidence that the secreted protein, Wnt inhibitory factor 1 (WIF1) modulates the activity of both Wnts and Hhs and may thus contribute to the intertwining of these pathways. In this article, we review the structure, evolution, molecular interactions and functions of WIF1 with major emphasis on its role in carcinogenesis.

Improving the Detection of Hepatocellular Carcinoma Using Serum AFP Expression in Combination with GPC3 and Micro-RNA MiR-122 Expression

Early diagnosis of hepatocellular carcinoma (HCC) greatly improves the survival and prognosisfor patients. In this study weevaluate the diagnostic promise of combining serum alpha-fetoprotein (AFP) expression with two potential biomarkers, serum glypican-3 (GPC3) and expression of the micro-RNA miR-122 for hepatitis C virus (HCV) related early-stage HCC. For this study serum samples from 47 patients with early-stage HCC, 54 chronic HCV (CH) carriers, 35 patients with liver cirrhosis (LC) and 54 health controls (HC) were collected. In addition to routine laboratory investigations, serum AFP, GPC3 and miR-122 were measured in all patients and healthy controls. Receiver operating characteristic (ROC) curves were used to present sensitivity and specificity for the biomarkers. The three markers were all significantly elevated in the serum samples from HCC patients. ROC curves showed the three markers had similar diagnostic capacities for distinguishing early-stage HCC from HCV-positive controls (LC + CH). In order to distinguish early-stage HCC from high-risk LC patients, the expression of miR-122 was superior to GPC3. Combination of the three markers as a panel showed a better diagnostic performance than any of the single markers (P <0.05). Overall, this study revealed that serum expression of GPC3 and miR-122 may be useful biomarkers to combine with serum AFP expression for the diagnosis of HCV related early-stage HCC.

Low Density Receptor-Related Protein 1 Interactions With the Extracellular Matrix: More Than Meets the Eye

The extracellular matrix (ECM) is a biological substrate composed of collagens, proteoglycans and glycoproteins that ensures proper cell migration and adhesion and keeps the cell architecture intact. The regulation of the ECM composition is a vital process strictly controlled by, among others, proteases, growth factors and adhesion receptors. As it appears, ECM remodeling is also essential for proper neuronal and glial development and the establishment of adequate synaptic signaling. Hence, disturbances in ECM functioning are often present in neurodegenerative diseases like Alzheimer’s disease. Moreover, mutations in ECM molecules are found in some forms of epilepsy and malfunctioning of ECM-related genes and pathways can be seen in, for example, cancer or ischemic injury. Low density lipoprotein receptor-related protein 1 (Lrp1) is a member of the low density lipoprotein receptor family. Lrp1 is involved not only in ligand uptake, receptor mediated endocytosis and lipoprotein transport—functions shared by low density lipoprotein receptor family members—but also regulates cell surface protease activity, controls cellular entry and binding of toxins and viruses, protects against atherosclerosis and acts on many cell signaling pathways. Given the plethora of functions, it is not surprising that Lrp1 also impacts the ECM and is involved in its remodeling. This review focuses on the role of Lrp1 and some of its major ligands on ECM function. Specifically, interactions with two Lrp1 ligands, integrins and tissue plasminogen activator are described in more detail.

Immunotherapeutic Targeting of GPC3 in Pediatric Solid Embryonal Tumors

Glypican 3 (GPC3) is a heparan sulfate proteoglycan and cell surface oncofetal protein which is highly expressed on a variety of pediatric solid embryonal tumors including the majority of hepatoblastomas, Wilms tumors, rhabdoid tumors, certain germ cell tumor subtypes, and a minority of rhabdomyosarcomas. Via both its core protein and heparan sulfate side chains, GPC3 activates the canonical Wnt/β-catenin pathway, which is frequently overexpressed in these malignancies. Loss of function mutations in GPC3 lead to Simpson-Golabi-Behmel Syndrome, an X-linked overgrowth condition with a predisposition to GPC3-expressing cancers including hepatoblastoma and Wilms tumor. There are several immunotherapeutic approaches to targeting GPC3, including vaccines, monoclonal antibodies, antibody-drug conjugates, bispecific antibodies, cytolytic T lymphocytes, and CAR T cells. These therapies offer a potentially novel means to target these pediatric solid embryonal tumors. A key pediatric-specific consideration of GPC3-targeted immunotherapeutics is that GPC3 can be physiologically expressed in normal tissues during the first year of life, particularly in the liver and kidney. In summary, this article reviews the current evidence for targeting childhood cancers with GPC3-directed immunotherapies.

Simpson-Golabi-Behmel syndrome in a 39-year-old male patient with suspected acromegaly-A case study

Simpson-Golabi-Behmel syndrome (SGBS) is a rare genetic condition and is inherited in an X-linked recessive manner. The disease is caused by a change in the nucleotide sequence of an X-linked gene encoding glypican 3, a protein belonging to the heparan-sulfate membrane proteoglycan family. SGBS case studies are almost entirely restricted to the pediatric population. Scarce literature describing SGBS course in adults may be due to both the high mortality of SGBS patients in childhood and low rate of SGBS diagnosis in adults. We present a case of a 39-year-old man with an initial diagnosis of acromegaly. Genetic tests revealed a hitherto unreported deletion in the GPC3 gene. SGBS manifestations in our patient included tall stature, dysmorphic features, and central nervous system (CNS) anatomical pathology. MRI of the head visualized abnormalities of median line structures, a feature consistent with SGBS: an unclosed craniopharyngeal canal, a sellar-suprasellar cyst, dysmorphic pituitary gland, and a cyst of the septum pellucidum. Moreover, cardiomyopathy complicated by life-threatening paroxysmal ventricular tachycardia was diagnosed. Although various cardiac anomalies are often found in SGBS, their pathogenesis is unclear and may be multifactorial. We believe that the presented case contributes to a better understanding of SGBS and may help clinicians in introducing prophylaxis and treatment for its comorbidities.

Signaling network involved in the GPC3-induced inhibition of breast cancer progression: role of canonical Wnt pathway

PURPOSE

We have shown that GPC3 overexpression in breast cancer cells inhibits in vivo tumor progression, by acting as a metastatic suppressor. GPC3-overexpressing cells are less clonogenic, viable and motile, while their homotypic adhesion is increased. We have presented evidences indicating that GPC3 inhibits canonical Wnt and Akt pathways, while non-canonical Wnt and p38MAPK cascades are activated. In this study, we aimed to investigate whether GPC3-induced Wnt signaling inhibition modulates breast cancer cell properties as well as to describe the interactions among pathways modulated by GPC3.

METHODS

Fluorescence microscopy, qRT-PCR microarray, gene reporter assay and Western blotting were performed to determine gene expression levels, signaling pathway activities and molecule localization. Lithium was employed to activate canonical Wnt pathway and treated LM3-GPC3 cell viability, migration, cytoskeleton organization and homotypic adhesion were assessed using MTS, wound healing, phalloidin staining and suspension growth assays, respectively.

RESULTS

We provide new data demonstrating that GPC3 blocks-also at a transcriptional level-both autocrine and paracrine canonical Wnt activities, and that this inhibition is required for GPC3 to modulate migration and homotypic adhesion. Our results indicate that GPC3 is secreted into the extracellular media, suggesting that secreted GPC3 competes with Wnt factors or interacts with them and thus prevents Wnt binding to Fz receptors. We also describe the complex network of interactions among GPC3-modulated signaling pathways.

CONCLUSION

GPC3 is operating through an intricate molecular signaling network. From the balance of these interactions, the inhibition of breast metastatic spread induced by GPC3 emerges.

Heparan sulfate proteoglycan - A common receptor for diverse cytokines

Heparan sulfate proteoglycans (HSPG) are macromolecular glyco-conjugates expressed ubiquitously on the cell surface and in the extracellular matrix where they interact with a wide range of ligands to regulate many aspects of cellular function. The capacity of the side glycosaminoglycan chain heparan sulfate (HS) being able to interact with diverse protein ligands relies on its complex structure that is generated by a controlled biosynthesis process, involving the actions of glycosyl-transferases, sulfotransferases and the glucuronyl C5-epimerase. It is believed that activities of the modification enzymes control the HS structures that are designed to serve the biological functions in a given cell or biological status. In this review, we briefly discuss recent understandings on the roles of HSPG in cytokine stimulated cellular signaling, focusing on FGF, TGF-β, Wnt, Hh, HGF and VEGF.

Glypicans as Cancer Therapeutic Targets

Glypicans are a group of cell-surface glycoproteins in which heparan sulfate (HS) glycosaminoglycan chains are covalently linked to a protein core. The glypican gene family is broadly conserved across animal species and plays important roles in biological processes. Glypicans can function as coreceptors for multiple signaling molecules known for regulating cell growth, motility, and differentiation. Some members of the glypican family, including glypican 2 (GPC2) and glypican 3 (GPC3), are expressed in childhood cancers and liver cancers, respectively. Antibody-based therapies targeting glypicans are being investigated in preclinical and clinical studies, with the goal of treating solid tumors that do not respond to standard therapies. These studies may establish glypicans as a new class of therapeutic targets for treating cancer.

Proteoglycans Are Attractive Biomarkers and Therapeutic Targets in Hepatocellular Carcinoma

Proteoglycans, which consist of a protein core and glycosaminoglycan chains, are major components of the extracellular matrix and play physiological roles in maintaining tissue homeostasis. In the carcinogenic tissue microenvironment, proteoglycan expression changes dramatically. Altered proteoglycan expression on tumor and stromal cells affects cancer cell signaling pathways, which alters growth, migration, and angiogenesis and could facilitate tumorigenesis. This dysregulation of proteoglycans has been implicated in the pathogenesis of diseases such as hepatocellular carcinoma (HCC) and the underlying mechanism has been studied extensively. This review summarizes the current knowledge of the roles of proteoglycans in the genesis and progression of HCC. It focuses on well-investigated proteoglycans such as serglycin, syndecan-1, glypican 3, agrin, collagen XVIII/endostatin, versican, and decorin, with particular emphasis on the potential of these factors as biomarkers and therapeutic targets in HCC regarding the future perspective of precision medicine toward the "cure of HCC".

Roles of glycosaminoglycans as regulators of ligand/receptor complexes

Glycosaminoglycans (GAGs) play a widespread role in embryonic development, as deletion of enzymes that contribute to GAG synthesis lead to deficiencies in cell migration and tissue modelling. Despite the biochemical and structural characterization of individual protein/GAG interactions, there is no concept available that links the molecular mechanisms of GAG/protein engagements to tissue development. Here, we focus on the role of GAG polymers in mediating interactions between cell surface receptors and their ligands. We categorize several switches that lead to ligand activation, inhibition, selection and addition, based on recent structural studies of select receptor/ligand complexes. Based on these principles, we propose that individual GAG polymers may affect several receptor pathways in parallel, orchestrating a cellular response to an environmental cue. We believe that it is worthwhile to study the role of GAGs as molecular switches, as this may lead to novel drug candidates to target processes such as angiogenesis, neuroregeneration and tumour metastasis.

Dynamic Expression of Genes Involved in Proteoglycan/Glycosaminoglycan Metabolism during Skin Development

Glycosaminoglycans are important for cell signaling and therefore for proper embryonic development and adult homeostasis. Expressions of genes involved in proteoglycan/glycosaminoglycan (GAG) metabolism and of genes coding for growth factors known to bind GAGs were analyzed during skin development by microarray analysis and real time quantitative PCR. GAG related genes were organized in six categories based on their role in GAG homeostasis, viz. (1) production of precursor molecules, (2) production of core proteins, (3) synthesis of the linkage region, (4) polymerization, (5) modification, and (6) degradation of the GAG chain. In all categories highly dynamic up- and downregulations were observed during skin development, including differential expression of GAG modifying isoenzymes, core proteins, and growth factors. In two mice models, one overexpressing heparanase and one lacking C5 epimerase, differential expression of only few genes was observed. Data show that during skin development a highly dynamic and complex expression of GAG-associated genes occurs. This likely reflects quantitative and qualitative changes in GAGs/proteoglycans, including structural fine tuning, which may be correlated with growth factor handling.

miR-324-5p is up regulated in end-stage osteoarthritis and regulates Indian Hedgehog signalling by differing mechanisms in human and mouse

The Hedgehog (Hh) signalling pathway plays important roles during embryonic development and in adult tissue homeostasis, for example cartilage, where its deregulation can lead to osteoarthritis (OA). microRNAs (miRNAs) are important regulators of gene expression, and have been implicated in the regulation of signalling pathways, including Hh, thereby impacting upon development and disease. Our aim was to identify the function of miRNAs whose expression is altered in OA cartilage. Here we identified an increase in miR-324-5p expression in OA cartilage and hypothesised that, as in glioma, miR-324-5p would regulate Hh signalling. We determined that miR-324-5p regulates osteogenesis in human mesenchymal stem cells (MSCs) and in mouse C3H10T1/2 cells. Luciferase reporter assays demonstrated that miR-324-5p directly regulated established targets GLI1 and SMO in human but not in mouse, suggesting species-dependent mechanism of Hh pathway regulation. Stable Isotope Labelling with Amino acids in Cell culture (SILAC), mass spectrometry and whole genome transcriptome analysis identified Glypican 1 (Gpc1) as a novel miR-324-5p target in mouse, which was confirmed by real-time RT-PCR, immunoblotting and 3′UTR-luciferase reporters. Knockdown of Gpc1 reduced Hh pathway activity, and phenocopied the effect of miR-324-5p on osteogenesis, indicating that miR-324-5p regulates Hh signalling in mouse via direct targeting of Gpc1. Finally, we showed that human GPC1 is not a direct target of miR-324-5p. Importantly, as well as identifying novel regulation of Indian Hedgehog (Ihh) signalling, this study demonstrates how a miRNA can show conserved pathway regulation in two species but by distinct mechanisms and highlights important differences between human diseases and mouse models.