The Tumor Microenvironment: Focus on Extracellular Matrix

The extracellular matrix (ECM) regulates the development and maintains tissue homeostasis. The ECM is composed of a complex network of molecules presenting distinct biochemical properties to regulate cell growth, survival, motility, and differentiation. Among their components, proteoglycans (PGs) are considered one of the main components of ECM. Its composition, biomechanics, and anisotropy are exquisitely tuned to reflect the physiological state of the tissue. The loss of ECM's homeostasis is seen as one of the hallmarks of cancer and, typically, defines transitional events in tumor progression and metastasis. In this chapter, we discuss the types of proteoglycans and their roles in cancer. It has been observed that the amount of some ECM components is increased, while others are decreased, depending on the type of tumor. However, both conditions corroborate with tumor progression and malignancy. Therefore, ECM components have an increasingly important role in carcinogenesis and this leads us to believe that their understanding may be a key in the discovery of new anti-tumor therapies. In this book, the main ECM components will be discussed in more detail in each chapter.

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.

A Frizzled-Like Cysteine-Rich Domain in Glypican-3 Mediates Wnt Binding and Regulates Hepatocellular Carcinoma Tumor Growth in Mice

Wnt signaling is one of the key regulators of hepatocellular carcinoma (HCC) tumor progression. In addition to the classical receptor frizzled (FZD), various coreceptors including heparan sulfate proteoglycans (HSPGs) are involved in Wnt activation. Glypican-3 (GPC3) is an HSPG that is overexpressed in HCC and functions as a Wnt coreceptor that modulates HCC cell proliferation. These features make GPC3 an attractive target for liver cancer therapy. However, the precise interaction of GPC3 and Wnt and how GPC3, Wnt, and FZD cooperate with each other are poorly understood. In this study, we established a structural model of GPC3 containing a putative FZD-like cysteine-rich domain at its N-terminal lobe. We found that F41 and its surrounding residues in GPC3 formed a Wnt-binding groove that interacted with the middle region located between the lipid thumb domain and the index finger domain of Wnt3a. Mutating residues in this groove significantly inhibited Wnt3a binding, β-catenin activation, and the transcriptional activation of Wnt-dependent genes. In contrast with the heparan sulfate chains, the Wnt-binding groove that we identified in the protein core of GPC3 seemed to promote Wnt signaling in conditions when FZD was not abundant. Specifically, blocking this domain using an antibody inhibited Wnt activation. In HCC cells, mutating residue F41 on GPC3 inhibited activation of β-catenin in vitro and reduced xenograft tumor growth in nude mice compared with cells expressing wild-type GPC3. Conclusion: Our investigation demonstrates a detailed interaction of GPC3 and Wnt3a, reveals the precise mechanism of GPC3 acting as a Wnt coreceptor, and provides a potential target site on GPC3 for Wnt blocking and HCC therapy.

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.

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.

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.

Glypican 6 is a putative biomarker for metastatic progression of cutaneous melanoma

Due to the poor prognosis of advanced metastatic melanoma, it is crucial to find early biomarkers that help identify which melanomas will metastasize. By comparing the gene expression data from primary and cutaneous melanoma samples from The Cancer Genome Atlas (TCGA), we identified GPC6 among a set of genes whose expression levels can distinguish between primary melanoma and regional cutaneous/subcutaneous metastases. Glypicans are thought to play a role in tumor growth by regulating the signaling pathways of Wnt, Hedgehogs, fibroblast growth factors (FGFs), and bone morphogenetic proteins (BMPs). We showed that GPC6 expression was up-regulated in a melanoma cell line compared to normal melanocytes and in metastatic melanoma compared to primary melanoma. Furthermore, GPC6 expression was positively correlated with genes largely involved in cell adhesion and migration in both melanoma samples and in RNA-seq samples from other TCGA tumors. Our results suggest that GPC6 may play a role in tumor metastatic progression. In TCGA melanoma samples, we also showed that GPC6 expression was negatively correlated with miR-509-3p, which has previously been shown to function as a tumor suppressor in various cancer cell lines. We overexpressed miR-509-3p in A375 melanoma cells and showed that GPC6 expression was significantly suppressed. This result suggested that GPC6 was a putative target of miR-509-3p in melanoma. Together, our findings identified GPC6 as an early biomarker for melanoma metastatic progression, one that can be regulated by miR-509-3p.

rs2267531, a promoter SNP within glypican-3 gene in the X chromosome, is associated with hepatocellular carcinoma in Egyptians

Hepatocellular carcinoma (HCC) is a major health concern in Egypt owing to the high prevalence of hepatitis C virus (HCV) infection. HCC incidence is characterized by obvious male predominance, yet the molecular mechanisms behind this gender bias are still unidentified. Functional variations in X-linked genes have more impact on males than females. Glypican-3 (GPC3) gene, located in the Xq26 region, has lately emerged as being potentially implicated in hepatocellular carcinogenesis. The current study was designed to examine the association of -784 G/C single nucleotide polymorphism (SNP) in GPC3 promoter region (rs2267531) with HCC susceptibility in male and female Egyptian HCV patients. Our results revealed a significant association between GPC3 and HCC risk in both males and females, evidenced by higher C allele and CC/C genotype frequencies in HCC patients when compared to controls. However, no such association was found when comparing HCV patients to controls. Moreover, GPC3 gene and protein expression levels were significantly higher in CC/C than in GG/G genotype carriers in males and females. The CC/C genotype exhibited a significant shorter overall survival than GG/G genotype in HCC patients. In conclusion, GPC3 rs2267531 on the X chromosome is significantly associated with HCC, but not with HCV infection, in the Egyptian population.

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.

Preparation of a monoclonal antibody against the carcinoembryonic antigen, glypican‑3

The carcinoembryonic antigen, glypican‑3 (GPC3), is a putative therapeutic target and diagnostic marker of hepatoma. In the present study, a monoclonal antibody (mAb) specifically against GPC3 was obtained via cloning the sequence of GPC3 via polymerase chain reaction and inserting it into a pET16b vector prior to transfection into Escherichia coli (E. coli) BL21. BALB/c mice were immunized with 20 µg purified antigen by intrasplenic embedding. Splenocytes and mouse myeloma cells SP2/0 were fused; then, the hybridoma cells were screened by an indirect ELISA. The properties of the mAb were examined by western blotting and immunofluorescence analysis against the purified protein. The results revealed that the prokaryotic expression vector of GPC3 had been successfully generated and GPC3 was stably expressed in E. coli BL21. A stable hybridoma cell line, 2F3, was generated in the present study, which produced mAbs against GPC3. The mAb 2F3 had a high antibody titer and the isotype was identified as IgG1/κ; 2F3 hybridomas had a median chromosome number of 98. Western blot and immunofluorescence analyses revealed that 2F3 specifically recognized recombinant and native GPC3. The 2F3 clone was proposed as a stable secretor of this mAb against GPC3. The results of present study indicated that the successful preparation of recombinant GPC3 protein and an anti‑human GPC3 mouse mAb may be provide a basis for developments in the diagnosis and treatment of liver cancer.

The Selection of a Hepatocyte Cell Line Susceptible to Plasmodium falciparum Sporozoite Invasion That Is Associated With Expression of Glypican-3

In vitro studies of liver stage (LS) development of the human malaria parasite Plasmodium falciparum are technically challenging; therefore, fundamental questions about hepatocyte receptors for invasion that can be targeted to prevent infection remain unanswered. To identify novel receptors and to further understand human hepatocyte susceptibility to P. falciparum sporozoite invasion, we created an optimized in vitro system by mimicking in vivo liver conditions and using the subcloned HC-04.J7 cell line that supports mean infection rates of 3-5% and early development of P. falciparum exoerythrocytic forms-a 3- to 5-fold improvement on current in vitro hepatocarcinoma models for P. falciparum invasion. We juxtaposed this invasion-susceptible cell line with an invasion-resistant cell line (HepG2) and performed comparative proteomics and RNA-seq analyses to identify host cell surface molecules and pathways important for sporozoite invasion of host cells. We identified and investigated a hepatocyte cell surface heparan sulfate proteoglycan, glypican-3, as a putative mediator of sporozoite invasion. We also noted the involvement of pathways that implicate the importance of the metabolic state of the hepatocyte in supporting LS development. Our study highlights important features of hepatocyte biology, and specifically the potential role of glypican-3, in mediating P. falciparum sporozoite invasion. Additionally, it establishes a simple in vitro system to study the LS with improved invasion efficiency. This work paves the way for the greater malaria and liver biology communities to explore fundamental questions of hepatocyte-pathogen interactions and extend the system to other human malaria parasite species, like P. vivax.

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.

Diffuse and canalicular patterns of glypican-3 expression reflect malignancy of hepatocellular carcinoma

Glypican-3 (GPC3) is expressed in most hepatocellular carcinomas (HCCs). To investigate the significance of various GPC3 staining patterns in HCC, we classified 134 HCC patients into three groups: those with diffuse GPC3 staining, canalicular GPC3 staining, and others (including negative staining). HCCs with diffuse staining were correlated with poor differentiation, high Ki-67 indices, high serum α-fetoprotein (AFP) levels, and early recurrence. In contrast, HCCs with canalicular staining were well differentiated with lower AFP levels. Overall survival in this group was better than that of the other two groups. Comparative analysis of GPC3 staining patterns with markers for HCC subclassification showed that diffuse staining was correlated with the expression of biliary/stem cell markers, whereas canalicular staining was correlated with expression of the markers of WNT-activated HCCs. Induction of leucine-rich repeat-containing G-protein-coupled receptor 5 (LGR5), known as a target of the WNT signaling pathway, in HCC cells resulted in reduced GPC3 expression in vitro. The LGR5-induced cells formed tumors with canaliculus-like structures in mice and showed canalicular GPC3 staining. The current findings showed the significance of recognizing distinct GPC3 staining patterns, i.e., diffuse and canalicular, which may reflect different carcinogenetic mechanisms and indicate the level of malignancy of HCC.

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".

Phosphorothioate-Modified AP613-1 Specifically Targets GPC3 when Used for Hepatocellular Carcinoma Cell Imaging

Glypican-3 (GPC3), the cellular membrane proteoglycan, has been established as a tumor biomarker for early diagnosis of hepatocellular carcinoma (HCC). GPC3 is highly expressed in more than 70% HCC tissues detected by antibody-based histopathological systems. Recently, aptamers, a short single-strand DNA or RNA generated from systematic evolution of ligands by exponential enrichment (SELEX), were reported as potential alternatives in tumor-targeted imaging and diagnosis. In this study, a total of 19 GPC3-bound aptamers were successfully screened by capillary electrophoresis (CE)-SELEX technology. After truncated, AP613-1 was confirmed to specifically target GPC3 with a dissociation constant (K_D) of 59.85 nM. When modified with a phosphorothioate linkage, APS613-1 targeted GPC3 with a K_D of 15.48 nM and could be used as a specific probe in living Huh7 and PLC/PRF/5 imaging, GPC3-positive cell lines, but not in L02 or A549, two GPC3-negative cell lines. More importantly, Alexa Fluor 750-conjugated APS613-1 could be used as a fluorescent probe to subcutaneous HCC imaging in xenograft nude mice. Our results indicated that modified AP613-1, especially APS613-1, was a potential agent in GPC3-positive tumor imaging for HCC early diagnosis.

HCCDB: A Database of Hepatocellular Carcinoma Expression Atlas

Hepatocellular carcinoma (HCC) is highly heterogeneous in nature and has been one of the most common cancer types worldwide. To ensure repeatability of identified gene expression patterns and comprehensively annotate the transcriptomes of HCC, we carefully curated 15 public HCC expression datasets that cover around 4000 clinical samples and developed the database HCCDB to serve as a one-stop online resource for exploring HCC gene expression with user-friendly interfaces. The global differential gene expression landscape of HCC was established by analyzing the consistently differentially expressed genes across multiple datasets. Moreover, a 4D metric was proposed to fully characterize the expression pattern of each gene by integrating data from The Cancer Genome Atlas (TCGA) and Genotype-Tissue Expression (GTEx). To facilitate a comprehensive understanding of gene expression patterns in HCC, HCCDB also provides links to third-party databases on drug, proteomics, and literatures, and graphically displays the results from computational analyses, including differential expression analysis, tissue-specific and tumor-specific expression analysis, survival analysis, and co-expression analysis. HCCDB is freely accessible at http://lifeome.net/database/hccdb.

Mechanisms of Wnt signaling and control

The Wnt signaling pathway is a highly conserved system that regulates complex biological processes across all metazoan species. At the cellular level, secreted Wnt proteins serve to break symmetry and provide cells with positional information that is critical to the patterning of the entire body plan. At the organismal level, Wnt signals are employed to orchestrate fundamental developmental processes, including the specification of the anterior-posterior body axis, induction of the primitive streak and ensuing gastrulation movements, and the generation of cell and tissue diversity. Wnt functions extend into adulthood where they regulate stem cell behavior, tissue homeostasis, and damage repair. Disruption of Wnt signaling activity during embryonic development or in adults results in a spectrum of abnormalities and diseases, including cancer. The molecular mechanisms that underlie the myriad of Wnt-regulated biological effects have been the subject of intense research for over three decades. This review is intended to summarize our current understanding of how Wnt signals are generated and interpreted. This article is categorized under: Biological Mechanisms > Cell Signaling Developmental Biology > Stem Cell Biology and Regeneration.

Heparan Sulfate Proteoglycans in Human Colorectal Cancer

Colorectal cancer is the third most common cancer worldwide, accounting for more than 610,000 mortalities every year. Prognosis of patients is highly dependent on the disease stage at diagnosis. Therefore, it is crucial to investigate molecules involved in colorectal cancer tumorigenesis, with possible use as tumor markers. Heparan sulfate proteoglycans are complex molecules present in the cell membrane and extracellular matrix, which play vital roles in cell adhesion, migration, proliferation, and signaling pathways. In colorectal cancer, the cell surface proteoglycan syndecan-2 is upregulated and increases cell migration. Moreover, expression of syndecan-1 and syndecan-4, generally antitumor molecules, is reduced. Levels of glypicans and perlecan are also altered in colorectal cancer; however, their role in tumor progression is not fully understood. In addition, studies have reported increased heparan sulfate remodeling enzymes, as the endosulfatases. Therefore, heparan sulfate proteoglycans are candidate molecules to clarify colorectal cancer tumorigenesis, as well as important targets to therapy and diagnosis.

New tumor suppressor microRNAs target glypican-3 in human liver cancer

Glypican-3 (GPC3) is an oncogene, frequently upregulated in liver malignancies such as hepatocellular carcinoma (HCC) and hepatoblastoma and constitutes a potential molecular target for therapy in liver cancer. Using a functional screening system, we identified 10 new microRNAs controlling GPC3 expression in malignant liver cells, five of them e.g. miR-4510, miR-203a-3p, miR-548aa, miR-376b-3p and miR-548v reduce GPC3 expression. These 5 microRNAs were significantly downregulated in tumoral compared to non-tumoral liver and inhibited tumor cell proliferation. Interestingly, miR-4510 inversely correlated with GPC3 mRNA and protein in HCC samples. This microRNA also induced apoptosis of hepatoma cells and blocked tumor growth in vivo in the chick chorioallantoic membrane model. We further show that the tumor suppressive effect of miR-4510 is mediated through direct targeting of GPC3 mRNA and inactivation of Wnt/β-catenin transcriptional activity and signaling pathway. Moreover, miR-4510 up-regulated the expression of several tumor suppressor genes while reducing the expression of other pro-oncogenes. In summary, we uncovered several new microRNAs targeting the oncogenic functions of GPC3. We provided strong molecular, cellular and in vivo evidences for the tumor suppressive activities of miR-4510 bringing to the fore the potential value of this microRNA in HCC therapy.

Dually modified transmembrane proteoglycans in development and disease

Aberrant cell signaling in response to secreted growth factors has been linked to the development of multiple diseases, including cancer. As such, understanding mechanisms that control growth factor availability and receptor-growth factor interaction is vital. Dually modified transmembrane proteoglycans (DMTPs), which are classified as cell surface macromolecules composed of a core protein decorated with covalently linked heparan sulfated (HS) and/or chondroitin sulfated (CS) glycosaminoglycan (GAG) chains, provide one type of regulatory mechanism. Specifically, DMTPs betaglycan and syndecan-1 (SDC1) play crucial roles in modulating key cell signaling pathways, such as Wnt, transforming growth factor-β and fibroblast growth factor signaling, to affect epithelial cell biology and cancer progression. This review outlines current and potential functions for betaglycan and SDC1, with an emphasis on comparing individual roles for HS and CS modified DMTPs. We highlight the mutual dependence of DMTPs' GAG chains and core proteins and provide comprehensive knowledge on how these DMTPs, through regulation of ligand availability and receptor internalization, control cell signaling pathways involved in development and disease.

Roles of two types of heparan sulfate clusters in Wnt distribution and signaling in Xenopus

Wnt proteins direct embryonic patterning, but the regulatory basis of their distribution and signal reception remain unclear. Here, we show that endogenous Wnt8 protein is distributed in a graded manner in Xenopus embryo and accumulated on the cell surface in a punctate manner in association with “N-sulfo-rich heparan sulfate (HS),” not with “N-acetyl-rich HS”. These two types of HS are differentially clustered by attaching to different glypicans as core proteins. N-sulfo-rich HS is frequently internalized and associated with the signaling vesicle, known as the Frizzled/Wnt/LRP6 signalosome, in the presence of Wnt8. Conversely, N-acetyl-rich HS is rarely internalized and accumulates Frzb, a secreted Wnt antagonist. Upon interaction with Frzb, Wnt8 associates with N-acetyl-rich HS, suggesting that N-acetyl-rich HS supports Frzb-mediated antagonism by sequestering Wnt8 from N-sulfo-rich HS. Thus, these two types of HS clusters may constitute a cellular platform for the distribution and signaling of Wnt8.

Wnt proteins mediate embryonic development but how protein localization and patterning is regulated is unclear. Here, the authors show that distinct structures with different heparan sulfate modifications (‘N-sulfo-rich’ and ‘N-acetyl-rich’) regulate cellular localization and signal transduction of Wnt8 in Xenopus.

Development of an Affimer-antibody combined immunological diagnosis kit for glypican-3

Glypican-3 (GPC3) is a promising new marker for hepatocellular carcinoma, but the reported values for serum GPC3 differ markedly between currently available kits. Here we isolated Affimer non-antibody binding proteins against GPC3 by phage display and developed a new sandwich chemiluminescence immunoassay (CLIA) combining an Affimer with a monoclonal antibody (Affimer-MAb CLIA). The proposed CLIA assay demonstrated a wide linear range  0.03–600 ng/mL) with a good linear correlation coefficient (0.9999), a high detection limitation (0.03 ng/mL) and specificity (0–0.002%) for detection of GPC3. The accuracy, hook effect and stability were demonstrated to be satisfactory. The mean level of GPC3 in serum was higher (>8.5 fold, P < 0.001) in hepatocellular carcinoma patients compared to healthy and other liver disease individuals. A poor correlation (correlation coefficients ranged from −0.286 to 0.478) was observed through pairwise comparison within different kits. However, only this newly developed CLIA test showed high specificity and correlated with the “gold standard” GPC3-immunohistochemistry. This study indicates that Affimer-MAb CLIA can be used to generate a sensitive immunodiagnostic kit, which offers the potential for a highly specific clinically-relevant detection system.

Preeclampsia: novel insights from global RNA profiling of trophoblast subpopulations

BACKGROUND

The maternal signs of preeclampsia, which include the new onset of high blood pressure, can occur because of faulty placentation. We theorized that transcriptomic analyses of trophoblast subpopulations in situ would lend new insights into the role of these cells in preeclampsia pathogenesis.

OBJECTIVE

Our goal was to enrich syncytiotrophoblasts, invasive cytotrophoblasts, or endovascular cytotrophoblasts from the placentas of severe preeclampsia cases. Total RNA was subjected to global transcriptional profiling to identify RNAs that were misexpressed compared with controls.

STUDY DESIGN

This was a cross-sectional analysis of placentas from women who had been diagnosed with severe preeclampsia. Gestational age-matched controls were placentas from women who had a preterm birth with no signs of infection. Laser microdissection enabled enrichment of syncytiotrophoblasts, invasive cytotrophoblasts, or endovascular cytotrophoblasts. After RNA isolation, a microarray approach was used for global transcriptional profiling. Immunolocalization identified changes in messenger RNA expression that carried over to the protein level. Differential expression of non-protein-coding RNAs was confirmed by in situ hybridization. A 2-way analysis of variance of non-coding RNA expression identified particular classes that distinguished trophoblasts in cases vs controls. Cajal body foci were visualized by coilin immunolocalization.

RESULTS

Comparison of the trophoblast subtype data within each group (severe preeclampsia or noninfected preterm birth) identified many highly differentially expressed genes. They included molecules that are known to be expressed by each subpopulation, which is evidence that the method worked. Genes that were expressed differentially between the 2 groups, in a cell-type-specific manner, encoded a combination of molecules that previous studies associated with severe preeclampsia and those that were not known to be dysregulated in this pregnancy complication. Gene ontology analysis of the syncytiotrophoblast data highlighted the dysregulation of immune functions, morphogenesis, transport, and responses to vascular endothelial growth factor and progesterone. The invasive cytotrophoblast data provided evidence of alterations in cellular movement, which is consistent with the shallow invasion often associated with severe preeclampsia. Other dysregulated pathways included immune, lipid, oxygen, and transforming growth factor-beta responses. The data for endovascular cytotrophoblasts showed disordered metabolism, signaling, and vascular development. Additionally, the transcriptional data revealed the differential expression in severe preeclampsia of 2 classes of non-coding RNAs: long non-coding RNAs and small nucleolar RNAs. The long non-coding RNA, urothelial cancer associated 1, was the most highly up-regulated in this class. In situ hybridization confirmed severe preeclampsia-associated expression in syncytiotrophoblasts. The small nucleolar RNAs, which chemically modify RNA structure, also correlated with severe preeclampsia. Thus, we enumerated Cajal body foci, sites of small nucleolar RNA activity, in primary cytotrophoblasts that were isolated from control and severe preeclampsia placentas. In severe preeclampsia, cytotrophoblasts had approximately double the number of these foci as the control samples.

CONCLUSION

A laser microdissection approach enabled the identification of novel messenger RNAs and non-coding RNAs that were misexpressed by various trophoblast subpopulations in severe preeclampsia. The results suggested new avenues of investigation, in particular, the roles of PRG2, Kell blood group determinants, and urothelial cancer associated 1 in syncytiotrophoblast diseases. Additionally, many of the newly identified dysregulated molecules might have clinical utility as biomarkers of severe preeclampsia.

Glypican-6 promotes the growth of developing long bones by stimulating Hedgehog signaling

Autosomal-recessive omodysplasia (OMOD1) is caused by mutations in glypican-6. Capurro et al. show that glypican-6 stimulates Hedgehog (Hh) signaling, and reduced Hh signaling may contribute to the pathogenesis of OMOD1.

Autosomal-recessive omodysplasia (OMOD1) is a genetic condition characterized by short stature, shortened limbs, and facial dysmorphism. OMOD1 is caused by loss-of-function mutations of glypican 6 (GPC6). In this study, we show that GPC6-null embryos display most of the abnormalities found in OMOD1 patients and that Hedgehog (Hh) signaling is significantly reduced in the long bones of these embryos. The Hh-stimulatory activity of GPC6 was also observed in cultured cells, where this GPC increased the binding of Hh to Patched 1 (Ptc1). Consistent with this, GPC6 interacts with Hh through its core protein and with Ptc1 through its glycosaminoglycan chains. Hh signaling is triggered at the primary cilium. In the absence of Hh, we observed that GPC6 is localized outside of the cilium but moves into the cilium upon the addition of Hh. We conclude that GPC6 stimulates Hh signaling by binding to Hh and Ptc1 at the cilium and increasing the interaction of the receptor and ligand.

Heparin antagonizes cisplatin resistance of A2780 ovarian cancer cells by affecting the Wnt signaling pathway

Low molecular weight heparin (LMWH), the guideline based drug for prophylaxis and treatment of cancer-associated thrombosis, was recently shown to sensitize cisplatin resistant A2780cis human ovarian cancer cells for cisplatin cytotoxicity upon 24 h pretreatment with 50 μg × mL⁻¹ of the LMWH tinzaparin in vitro, equivalent to a therapeutic dosage. Thereby, LMWH induced sensitization by transcriptional reprogramming of A2780cis cells via not yet elucidated mechanisms that depend on cellular proteoglycans. Here we aim to illuminate the underlying molecular mechanisms of LMWH in sensitizing A2780cis cells for cisplatin. Using TCF/LEF luciferase promotor assay (Top/Flash) we show that resistant A2780cis cells possess a threefold higher Wnt signaling activity compared to A2780 cells. Furthermore, Wnt pathway blockade by FH535 leads to higher cisplatin sensitivity of A2780cis cells. Glypican-3 (GPC3) is upregulated in A2780cis cells in response to LMWH treatment, probably as counter-regulation to sustain the high Wnt activity against LMWH. Hence, LMWH reduces the cisplatin-induced rise in Wnt activity and TCF-4 expression in A2780cis cells, but keeps sensitive A2780 cells unaffected. Consequently, Wnt signaling pathway appears as primary target of LMWH in sensitizing A2780cis cells for cisplatin toxicity. Considering the outstanding role of LMWH in clinical oncology, this finding appears as promising therapeutic option to hamper chemoresistance.

Glypican-3: A promising biomarker for hepatocellular carcinoma diagnosis and treatment

Liver cancer is the second leading cause of cancer-related deaths, and hepatocellular carcinoma (HCC) is the most common type. Therefore, molecular targets are urgently required for the early detection of HCC and the development of novel therapeutic approaches. Glypican-3 (GPC3), an oncofetal proteoglycan anchored to the cell membrane, is normally detected in the fetal liver but not in the healthy adult liver. However, in HCC patients, GPC3 is overexpressed at both the gene and protein levels, and its expression predicts a poor prognosis. Mechanistic studies have revealed that GPC3 functions in HCC progression by binding to molecules such as Wnt signaling proteins and growth factors. Moreover, GPC3 has been used as a target for molecular imaging and therapeutic intervention in HCC. To date, GPC3-targeted magnetic resonance imaging, positron emission tomography, and near-infrared imaging have been investigated for early HCC detection, and various immunotherapeutic protocols targeting GPC3 have been developed, including the use of humanized anti-GPC3 cytotoxic antibodies, treatment with peptide/DNA vaccines, immunotoxin therapies, and genetic therapies. In this review, we summarize the current knowledge regarding the structure, function, and biology of GPC3 with a focus on its clinical potential as a diagnostic molecule and a therapeutic target in HCC immunotherapy.

Can glypican-3 be a disease-specific biomarker?

Background

Glypican-3 (GPC3) is a cell surface-bound proteoglycan which has been identified as a potential biomarker candidate in hepatocellular carcinoma, lung carcinoma, severe pneumonia, and acute respiratory distress syndrome (ARDS). The aim of our review is to evaluate whether GPC3 has utility as a disease-specific biomarker, to discuss the potential involvement of GPC3 in cell biology, and to consider the changes of GPC3 gene and protein expression and regulation in hepatocellular carcinoma, lung cancer, severe pneumonia, and ARDS.

Results

Immunohistochemical studies have suggested that over-expression of GPC3 is associated with a poorer prognosis for hepatocellular carcinoma patients. Expression of GPC3 leads to an increased apoptosis response in human lung carcinoma tumor cells, and is considered to be a candidate lung tumor suppressor gene. Increased serum levels of GPC3 have been demonstrated in ARDS patients with severe pneumonia.

Conclusions

Glypican-3 could be considered as a clinically useful biomarker in hepatocellular carcinoma, lung carcinoma, and ARDS, but further research is needed to confirm and expand on these findings.

Detailed expression profile of all six Glypicans and their modifying enzyme Notum during chick embryogenesis and their role in dorsal-ventral patterning of the neural tube

Vertebrate development is orchestrated by secreted signalling molecules that regulate cell behaviour and cell fate decisions during early embryogenesis. The activity of key signalling molecules including members of Hedgehog, Bone Morphogenetic Proteins and Wnt families are regulated by Glypicans, a family of GPI linked polypeptides. Glypicans either promote or inhibit the action of signalling molecules and add a layer of complexity that needs to be understood in order to fully decipher the processes that regulate early vertebrate development. Here we present a detailed expression profile of all six Glypicans and their modifying enzyme Notum during chick embryogenesis. Our results strongly suggest that these proteins have many as yet undiscovered roles to play during early embryogenesis. Finally, we have taken an experimental approach to investigate their role during the patterning of a key embryonic structure - the neural tube. In particular, we show that over-expression of Notum leads to the dorsalisation of this structure.

Advances in the study of oncofetal antigen glypican-3 expression in HBV-related hepatocellular carcinoma

Early specific diagnosis and effective treatment of hepatocellular carcinoma (HCC) are crucial. Expression of membrane-associated heparan sulfate proteoglycan glypican-3 (GPC-3) was recently found to increase as part of the malignant transformation of hepatocytes, and this increase is especially marked in patients with hepatitis B virus (HBV) infection, periportal cancerous embolus, or extra-hepatic metastasis. According to data from basic and clinical studies, the oncofetal antigen GPC-3 is a highly specific diagnostic biomarker of HCC and an indicator of its prognosis, and GPC-3 is also a promising target molecule for HCC gene therapy since it may play a crucial role in cell proliferation, metastasis, and invasion and it may mediate oncogenesis and oncogenic signaling pathways. This review summarizes recent advances in the use of oncofetal antigen GPC-3 to diagnose HBV-related HCC, estimate its prognosis, and its targeted therapy.

Altering the Proteoglycan State of Transforming Growth Factor β Type III Receptor (TβRIII)/Betaglycan Modulates Canonical Wnt/β-Catenin Signaling

Hyperactive Wnt/β-catenin signaling is linked to cancer progression and developmental abnormalities, making identification of mechanisms controlling Wnt/β-catenin signaling vital. Transforming growth factor β type III receptor (TβRIII/betaglycan) is a transmembrane proteoglycan co-receptor that exists with or without heparan and/or chondroitin sulfate glycosaminoglycan (GAG) modifications in cells and has established roles in development and cancer. Our studies here demonstrate that TβRIII, independent of its TGFβ co-receptor function, regulates canonical Wnt3a signaling by controlling Wnt3a availability through its sulfated GAG chains. Our findings revealed, for the first time, opposing functions for the different GAG modifications on TβRIII suggesting that Wnt interactions with the TβRIII heparan sulfate chains result in inhibition of Wnt signaling, likely via Wnt sequestration, whereas the chondroitin sulfate GAG chains on TβRIII promote Wnt3a signaling. These studies identify a novel, dual role for TβRIII/betaglycan and define a key requirement for the balance between chondroitin sulfate and heparan sulfate chains in dictating ligand responses with implications for both development and cancer.

The Heparan Sulfate Proteoglycan Glypican-6 Is Upregulated in the Failing Heart, and Regulates Cardiomyocyte Growth through ERK1/2 Signaling

Pressure overload is a frequent cause of heart failure. Heart failure affects millions of patients worldwide and is a major cause of morbidity and mortality. Cell surface proteoglycans are emerging as molecular players in cardiac remodeling, and increased knowledge about their regulation and function is needed for improved understanding of cardiac pathogenesis. Here we investigated glypicans (GPC1-6), a family of evolutionary conserved heparan sulfate proteoglycans anchored to the extracellular leaflet of the cell membrane, in experimental and clinical heart failure, and explored the function of glypican-6 in cardiac cells in vitro. In mice subjected to pressure overload by aortic banding (AB), we observed elevated glypican-6 levels during hypertrophic remodeling and dilated, end-stage heart failure. Consistently, glypican-6 mRNA was elevated in left ventricular myocardium from explanted hearts of patients with end-stage, dilated heart failure with reduced ejection fraction. Glypican-6 levels correlated negatively with left ventricular ejection fraction in patients, and positively with lung weight after AB in mice. Glypican-6 mRNA was expressed in both cardiac fibroblasts and cardiomyocytes, and the corresponding protein displayed different sizes in the two cell types due to tissue-specific glycanation. Importantly, adenoviral overexpression of glypican-6 in cultured cardiomyocytes increased protein synthesis and induced mRNA levels of the pro-hypertrophic signature gene ACTA1 and the hypertrophy and heart failure signature genes encoding natriuretic peptides, NPPA and NPPB. Overexpression of GPC6 induced ERK1/2 phosphorylation, and co-treatment with the ERK inhibitor U0126 attenuated the GPC6-induced increase in NPPA, NPPB and protein synthesis. In conclusion, our data suggests that glypican-6 plays a role in clinical and experimental heart failure progression by regulating cardiomyocyte growth through ERK signaling.

Glycerophosphodiesterase GDE2 Promotes Neuroblastoma Differentiation through Glypican Release and Is a Marker of Clinical Outcome

Neuroblastoma is a pediatric embryonal malignancy characterized by impaired neuronal differentiation. A better understanding of neuroblastoma differentiation is essential for developing new therapeutic approaches. GDE2 (encoded by GDPD5) is a six-transmembrane-domain glycerophosphodiesterase that promotes embryonic neurogenesis. We find that high GDPD5 expression is strongly associated with favorable outcome in neuroblastoma. GDE2 induces differentiation of neuroblastoma cells, suppresses cell motility, and opposes RhoA-driven neurite retraction. GDE2 alters the Rac-RhoA activity balance and the expression of multiple differentiation-associated genes. Mechanistically, GDE2 acts by cleaving (in cis) and releasing glycosylphosphatidylinositol-anchored glypican-6, a putative co-receptor. A single point mutation in the ectodomain abolishes GDE2 function. Our results reveal GDE2 as a cell-autonomous inducer of neuroblastoma differentiation with prognostic significance and potential therapeutic value.

An Unbiased Mass Spectrometry Approach Identifies Glypican-3 as an Interactor of Proprotein Convertase Subtilisin/Kexin Type 9 (PCSK9) and Low Density Lipoprotein Receptor (LDLR) in Hepatocellular Carcinoma Cells

The mechanism of LDL receptor (LDLR) degradation mediated by the proprotein convertase subtilisin/kexin type 9 (PCSK9) has been extensively studied; however, many steps within this process remain unclear and still require characterization. Recent studies have shown that PCSK9 lacking its Cys/His-rich domain can still promote LDLR internalization, but the complex does not reach the lysosome suggesting the presence of an additional interaction partner(s). In this study we carried out an unbiased screening approach to identify PCSK9-interacting proteins in the HepG2 cells' secretome using co-immunoprecipitation combined with mass spectrometry analyses. Several interacting proteins were identified, including glypican-3 (GPC3), phospholipid transfer protein, matrilin-3, tissue factor pathway inhibitor, fibrinogen-like 1, and plasminogen activator inhibitor-1. We then validated these interactions by co-immunoprecipitation and Western blotting. Furthermore, functional validation was examined by silencing each candidate protein in HepG2 cells using short hairpin RNAs to determine their effect on LDL uptake and LDLR levels. Only GPC3 and phospholipid transfer protein silencing in HepG2 cells significantly increased LDL uptake in these cells and displayed higher total LDLR protein levels compared with control cells. Moreover, our study provides the first evidence that GPC3 can modulate the PCSK9 extracellular activity as a competitive binding partner to the LDLR in HepG2 cells.

Novel insights into Notum and glypicans regulation in colorectal cancer

The connection between colorectal cancer (CRC) and Wnt signaling pathway activation is well known, but full elucidation of the underlying regulation of the Wnt/β-catenin pathway and its biological functions in CRC pathogenesis is still needed. Here, the azoxymethane/dextran sulfate sodium salt (AOM/DSS) murine model has been used as an experimental platform able to mimic human sporadic CRC development with predictable timing. We performed genome-wide expression profiling of AOM/DSS-induced tumors and normal colon mucosa to identify potential novel CRC biomarkers. Remarkably, the enhanced expression of Notum, a conserved feedback antagonist of Wnt, was observed in tumors along with alterations in Glypican-1 and Glypican-3 levels. These findings were confirmed in a set of human CRC samples. Here, we provide the first demonstration of significant changes in Notum and glypicans gene expression during CRC development and present evidence to suggest them as potential new biomarkers of CRC pathogenesis.

"Fibrous nests" in human hepatocellular carcinoma express a Wnt-induced gene signature associated with poor clinical outcome

Hepatocellular carcinoma (HCC) is the 3rd cause of cancer-related death worldwide. Most cases arise in a background of chronic inflammation, extracellular matrix (ECM) remodeling, severe fibrosis and stem/progenitor cell amplification. Although HCCs are soft cellular tumors, they may contain fibrous nests within the tumor mass. Thus, the aim of this study was to explore cancer cell phenotypes in fibrous nests. Combined anatomic pathology, tissue microarray and real-time PCR analyses revealed that HCCs (n=82) containing fibrous nests were poorly differentiated, expressed Wnt pathway components and target genes, as well as markers of stem/progenitor cells, such as CD44, LGR5 and SOX9. Consistently, in severe liver fibroses (n=66) and in HCCs containing fibrous nests, weighted correlation analysis revealed a gene network including the myofibroblast marker ACTA2, the basement membrane components COL4A1 and LAMC1, the Wnt pathway members FZD1; FZD7; WNT2; LEF1; DKK1 and the Secreted Frizzled Related Proteins (SFRPs) 1; 2 and 5. Moreover, unbiased random survival forest analysis of a transcriptomic dataset of 247 HCC patients revealed high DKK1, COL4A1, SFRP1 and LAMC1 to be associated with advanced tumor staging as well as with bad overall and disease-free survival. In vitro, these genes were upregulated in liver cancer stem/progenitor cells upon Wnt-induced mesenchymal commitment and myofibroblast differentiation. In conclusion, fibrous nests express Wnt target genes, as well as markers of cancer stem cells and mesenchymal commitment. Fibrous nests embody the specific microenvironment of the cancer stem cell niche and can be detected by routine anatomic pathology analyses.

Redirecting T Cells to Glypican-3 with 4-1BB Zeta Chimeric Antigen Receptors Results in Th1 Polarization and Potent Antitumor Activity

T cells engineered to express CD19-specific chimeric antigen receptors (CARs) have shown breakthrough clinical successes in patients with B-cell lymphoid malignancies. However, similar therapeutic efficacy of CAR T cells in solid tumors is yet to be achieved. In this study we systematically evaluated a series of CAR constructs targeting glypican-3 (GPC3), which is selectively expressed on several solid tumors. We compared GPC3-specific CARs that encoded CD3ζ (Gz) alone or with costimulatory domains derived from CD28 (G28z), 4-1BB (GBBz), or CD28 and 4-1BB (G28BBz). All GPC3-CARs rendered T cells highly cytotoxic to GPC3-positive hepatocellular carcinoma, hepatoblastoma, and malignant rhabdoid tumor cell lines in vitro. GBBz induced the preferential production of Th1 cytokines (interferon γ/granulocyte macrophage colony-stimulating factor) while G28z preferentially induced Th2 cytokines (interleukin-4/interleukin-10). Inclusion of 4-1BB in G28BBz could only partially ameliorate the Th2-polarizing effect of CD28. 4-1BB induced superior expansion of CAR T cells in vitro and in vivo. T cells expressing GPC3-CARs incorporating CD28, 4-1BB, or both induced sustained tumor regressions in two xenogeneic tumor models. Thus, GBBz CAR endows T cells with superior proliferative potential, potent antitumor activity, and a Th1-biased cytokine profile, justifying further clinical development of GBBz CAR for immunotherapy of GPC3-positive solid tumors.

Randomized phase II placebo controlled study of codrituzumab in previously treated patients with advanced hepatocellular carcinoma

BACKGROUND & AIMS

Codrituzumab, a humanized monoclonal antibody against Glypican-3 (GPC3) that is expressed in hepatocellular carcinoma (HCC), interacts with CD16/FcγRIIIa and triggers antibody-dependent cytotoxicity. Codrituzumab was studied vs. placebo in a randomized phase II trial in advanced HCC patients who had failed prior systemic therapy.

METHODS

Patients with advanced HCC who had failed prior systemic therapy, ⩾18years, Eastern cooperative oncology group (ECOG) 0-1, Child-Pugh A were randomized 2:1 to biweekly codrituzumab 1600mg vs. placebo. Patients were stratified based on GPC3 immunohistochemical expression: 2+/3+, 1+, and 0. Primary endpoint was progression free survival. Secondary endpoints include overall survival (OS), tolerability, pharmacokinetics, and an exploratory endpoint in biomarkers analysis.

RESULTS

185 patients were enrolled: 125 received codrituzumab and 60 placebo: Median age 64/63, 85/75% male, 46/42% Asian, ECOG 0 65/63%, 74/77% having vascular invasion and/or extra-hepatic metastasis. 84%/70% had prior sorafenib. Drug exposure was 98.4% of planned dose, with an identical adverse events profile between the 2 groups. The median progression free survival and overall survival in the codrituzumab vs. placebo groups in months were: 2.6 vs. 1.5 (hazard ratios 0.97, p=0.87), and 8.7 vs. 10 (hazard ratios 0.96, p=0.82). Projected Ctrough at cycle 3day 1 based exposure, high CD16/FcγRIIIa on peripheral immune cells, and GPC3 expression in the tumor, were all associated with prolonged progression free survival and overall survival.

CONCLUSIONS

Codrituzumab did not show clinical benefit in this previously treated HCC population. Whether higher codrituzumab drug exposure or the use of CD16 and GPC3 as potential biomarkers would improve outcome remain unanswered questions.

LAY SUMMARY

Codrituzumab is a manufactured antibody against a liver cancer protein called glypican-3. In this clinical trial, codrituzumab was not found be effective against liver cancer. It was suggested though that a higher dose of codrituzumab or selecting patients with high level of glypican-3 or its mediator CD16 might improve outcome.

CLINICAL TRIAL REGISTRATION

This trial is registered at Clinicaltrials.gov (NCT01507168).

Recent Insights into Cell Surface Heparan Sulphate Proteoglycans and Cancer

A small group of cell surface receptors are proteoglycans, possessing a core protein with one or more covalently attached glycosaminoglycan chains. They are virtually ubiquitous and their chains are major sites at which protein ligands of many types interact. These proteoglycans can signal and regulate important cell processes, such as adhesion, migration, proliferation, and differentiation. Since many protein ligands, such as growth factors, morphogens, and cytokines, are also implicated in tumour progression, it is increasingly apparent that cell surface proteoglycans impact tumour cell behaviour. Here, we review some recent advances, emphasising that many tumour-related functions of proteoglycans are revealed only after their modification in processes subsequent to synthesis and export to the cell surface. These include enzymes that modify heparan sulphate structure, recycling of whole or fragmented proteoglycans into exosomes that can be paracrine effectors or biomarkers, and lateral interactions between some proteoglycans and calcium channels that impact the actin cytoskeleton.

Epitope mapping by a Wnt-blocking antibody: evidence of the Wnt binding domain in heparan sulfate

Heparan sulfate (HS) is a polysaccharide known to modulate many important biological processes, including Wnt signaling. However, the biochemical interaction between HS and Wnt molecules is not well characterized largely due to the lack of suitable methods. To determine the Wnt binding domain in HS, we used a Wnt signaling-inhibitory antibody (HS20) and a panel of synthetic HS oligosaccharides with distinct lengths and sulfation modifications. We found that the binding of HS20 to heparan sulfate required sulfation at both the C2 position (2-O-sulfation) and C6 position (6-O-sulfation). The oligosaccharides with the greatest competitive effect for HS20 binding were between six and eight saccharide residues in length. Additionally, a four residue-long oligosaccharide could also be recognized by HS20 if an additional 3-O-sulfation modification was present. Furthermore, similar oligosaccharides with 2-O, 6-O and 3-O-sulfations showed inhibition for Wnt activation. These results have revealed that HS20 and Wnt recognize a HS structure containing IdoA2S and GlcNS6S, and that the 3-O-sulfation in GlcNS6S3S significantly enhances the binding of both HS20 and Wnt. This study provides the evidence for identifying the Wnt binding domain in HS and suggests a therapeutic approach to target the interaction of Wnt and HS in cancer and other diseases.

Glypican1/2/4/6 and sulfated glycosaminoglycans regulate the patterning of the primary body axis in the cnidarian Nematostella vectensis

Glypicans are members of the heparan sulfate (HS) subfamily of proteoglycans that can function in cell adhesion, cell crosstalk and as modulators of the major developmental signalling pathways in bilaterians. The evolutionary origin of these multiple functions is not well understood. In this study we investigate the role of glypicans in the embryonic and larval development of the sea anemone Nematostella vectensis, a member of the non-bilaterian clade Cnidaria. Nematostella has two glypican (gpc) genes that are expressed in mutually exclusive ectodermal domains, NvGpc1/2/4/6 in a broad aboral domain, and NvGpc3/5 in narrow oral territory. The endosulfatase NvSulf (an extracellular modifier of HS chains) is expressed in a broad oral domain, partially overlapping with both glypicans. Morpholino-mediated knockdown of NvGpc1/2/4/6 leads to an expansion of the expression domains of aboral marker genes and a reduction of oral markers at gastrula stage, strikingly similar to knockdown of the Wnt receptor NvFrizzled5/8. We further show that treatment with sodium chlorate, an inhibitor of glycosaminoglycan (GAG) sulfation, phenocopies knockdown of NvGpc1/2/4/6 at gastrula stage. At planula stage, knockdown of NvGpc1/2/4/6 and sodium chlorate treatment result in alterations in aboral marker gene expression that suggest additional roles in the fine-tuning of patterning within the aboral domain. These results reveal a role for NvGpc1/2/4/6 and sulfated GAGs in the patterning of the primary body axis in Nematostella and suggest an ancient function in regulating Frizzled-mediated Wnt signalling.