Isolation of a cDNA corresponding to a developmentally regulated transcript in rat intestine

Novel Nanotechnology Approaches to Overcome Drug Resistance in the Treatment of Hepatocellular Carcinoma: Glypican 3 as a Useful Target for Innovative Therapies

Hepatocellular carcinoma (HCC) is the second most lethal tumor, with a 5-year survival rate of 18%. Early stage HCC is potentially treatable by therapies with curative intent, whereas chemoembolization/radioembolization and systemic therapies are the only therapeutic options for intermediate or advanced HCC. Drug resistance is a critical obstacle in the treatment of HCC that could be overcome by the use of targeted nanoparticle-based therapies directed towards specific tumor-associated antigens (TAAs) to improve drug delivery. Glypican 3 (GPC3) is a member of the glypican family, heparan sulfate proteoglycans bound to the cell surface via a glycosylphosphatidylinositol anchor. The high levels of GPC3 detected in HCC and the absence or very low levels in normal and non-malignant liver make GPC3 a promising TAA candidate for targeted nanoparticle-based therapies. The use of nanoparticles conjugated with anti-GPC3 agents may improve drug delivery, leading to a reduction in severe side effects caused by chemotherapy and increased drug release at the tumor site. In this review, we describe the main clinical features of HCC and the common treatment approaches. We propose the proteoglycan GPC3 as a useful TAA for targeted therapies. Finally, we describe nanotechnology approaches for anti-GPC3 drug delivery systems based on NPs for HCC treatment.

The prognostic value of arginase-1 and glypican-3 expression levels in patients after surgical intrahepatic cholangiocarcinoma resection

Background

The aim of this study was to investigate the prognostic value of arginase-1 (Arg-1) and glypican-3 (GPC-3) in patients with intrahepatic cholangiocarcinoma (ICC).

Methods

Two hundred and thirty-seven patients with ICC were included in this study. All patients had undergone radical surgery and had complete clinical information. Immunohistochemistry was used to assess the levels of Arg-1 and GPC-3 in ICC tissues. Univariate and multivariate analyses were conducted to identify independent risk factors in ICC. The relationship between Arg-1 and GPC-3 levels and patient survival was determined using the Kaplan-Meier method.

Results

High Arg-1 and GPC-3 expression levels were associated with poor prognosis in patients with ICC, and they could be as new prognostic biomarkers in ICC.

Conclusion

Arg-1 and GPC-3 can serve as independent prognostic biomarkers in ICC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12957-021-02426-9.

Glypicans and Heparan Sulfate in Synaptic Development, Neural Plasticity, and Neurological Disorders

Heparan sulfate proteoglycans (HSPGs) are components of the cell surface and extracellular matrix, which bear long polysaccharides called heparan sulfate (HS) attached to the core proteins. HSPGs interact with a variety of ligand proteins through the HS chains, and mutations in HSPG-related genes influence many biological processes and cause various diseases. In particular, recent findings from vertebrate and invertebrate studies have raised the importance of glycosylphosphatidylinositol-anchored HSPGs, glypicans, as central players in the development and functions of synapses. Glypicans are important components of the synapse-organizing protein complexes and serve as ligands for leucine-rich repeat transmembrane neuronal proteins (LRRTMs), leukocyte common antigen-related (LAR) family receptor protein tyrosine phosphatases (RPTPs), and G-protein-coupled receptor 158 (GPR158), regulating synapse formation. Many of these interactions are mediated by the HS chains of glypicans. Neurexins (Nrxs) are also synthesized as HSPGs and bind to some ligands in common with glypicans through HS chains. Therefore, glypicans and Nrxs may act competitively at the synapses. Furthermore, glypicans regulate the postsynaptic expression levels of ionotropic glutamate receptors, controlling the electrophysiological properties and non-canonical BMP signaling of synapses. Dysfunctions of glypicans lead to failures in neuronal network formation, malfunction of synapses, and abnormal behaviors that are characteristic of neurodevelopmental disorders. Recent human genetics revealed that glypicans and HS are associated with autism spectrum disorder, neuroticism, and schizophrenia. In this review, we introduce the studies showing the roles of glypicans and HS in synapse formation, neural plasticity, and neurological disorders, especially focusing on the mouse and Drosophila as potential models for human diseases.

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.

Apatinib-loaded lipid nanobubbles combined with ultrasound-targeted nanobubble destruction for synergistic treatment of HepG2 cells in vitro

Purpose

Apatinib, an oral small-molecule antiangiogenetic medicine, is used to treat patients with advanced hepatocellular carcinoma. However, its systemic toxic side effects cannot be ignored. The ultrasound (US)-targeted nanobubble destruction technology can minimize systemic drug exposure and maximize therapeutic efficacy. The aim of this study was to develop novel GPC3-targeted and drug-loaded nanobubbles (NBs) and further assess the associated therapeutic effects on hepatocellular carcinoma cells in vitro.

Materials and methods

Apatinib-loaded NBs were prepared by a mechanical vibration method. GPC3, a liver tumor homing peptide, was coated onto the surface of apatinib-loaded NBs through biotin–avidin interactions to target liver cancer HepG2 cells. The effects of different treatment groups on cell proliferation, cell cycle, and apoptosis of HepG2 cells were tested.

Results

The NBs could achieve 68% of optimal drug encapsulation. In addition, ligand binding assays demonstrated that attachment of targeted NBs to human HepG2 liver cancer cells was highly efficient. Furthermore, cell proliferation assays indicated that the antiproliferative activities of GPC3-targeted and apatinib-loaded NBs in combination with US (1 MHz, 1 W/cm², 30 s) were, respectively, 44.11%±2.84%, 57.09%±6.38%, and 67.51%±2.89% after 24, 48, and 72 h of treatment. Treatment with GPC3-targeted and apatinib-loaded NBs also resulted in a higher proportion of cells in the G1 phase compared with other treatment groups such as apatinib only and nontargeted apatinib-loaded NBs when US was utilized.

Conclusion

US-targeted and drug-loaded nanobubble destruction successfully achieved selective growth inhibition and apoptosis in HepG2 cells in vitro. Therefore, GPC3-targeted and apatinib-loaded NBs can be considered a novel chemotherapeutic approach for treating liver cancer in combination with US.

Evaluating clinical and prognostic implications of Glypican-3 in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most deadly cancers worldwide. In patients with HCC, histopathogical differentiation is an important indicator of prognosis; however, because determination of HCC differentiation is difficult, the recently described immunohistochemical (IHC) marker glypican3 (GPC3) might assist in HCC prognostication.The goal of our study was to investigate GPC3's IHC staining pattern and define the relationship between its expression and patients' clinicopathologic features and overall survival. We retrieved clinical parameters from 101 pathologically diagnosed HCC patients' medical records and classified these patients into 4 clinical score categories (0–3) based on increasing GPC3 staining intensity and the percentage of stained tumor cells in their resection and biopsy specimens. Histopathological samples were well, moderately, and poorly differentiated in 33, 22, and 12 patients, respectively, and the GPC3 expression rate was 63%, 86%, and 92%,respectively. The median overall survival was 49.9 months (confidence interval (CI): 35.3–64.6 months) for clinical scores 0–1 and 30.7 months (CI: 19.4–41.9 months) for clinical scores 2–3. This difference was not statistically significant (P = .06) but showed a strong trend. In conclusion, a greater GPC3 expression is associated with a worse HCC prognosis and may be a promising prognostic marker.

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.

Glypican-3-mediated inhibition of CD26 by TFPI: a novel mechanism in hematopoietic stem cell homing and maintenance

Directional migration determines hematopoietic stem/progenitor cell (HSPC) homing, which depends upon the interaction between the chemokine CXCL12 and its receptor CXCR4. CD26 is a widely expressed membrane-bound ectopeptidase that cleaves CXCL12 thereby depleting its chemokine activity. We identified tissue-factor pathway inhibitor (TFPI) as a biological inhibitor of CD26 in murine and human HSPCs. We observed low-level TFPI expression in endothelial cells in the bone marrow (BM), which did not increase following radiation injury. Treatment of HSPCs with TFPI in vitro led to enhanced HSPC migration toward CXCL12, as well as homing and engraftment in the BM upon transplantation. We found that Glypican-3 (GPC3), a heparan sulfate proteoglycan expressed on murine as well as human HSPCs, mediated this effect. TFPI did not affect CD26 activity, migration, or homing of GPC3(-/-) HSPCs, while it affected GPC1(-/-) HSPCs similar to wild-type HSPCs. Moreover, proliferation of GPC3(-/-) but not GPC1(-/-) BM HSPCs was significantly increased, which was associated with a decrease in the primitive HSC pool in BM and an increase in proportion of the circulating HSPCs in the peripheral blood. Hence, we present a novel role for TFPI and GPC3 in regulating HSC homing as well as retention in the BM.

Biomarkers for hepatocellular carcinoma

Hepatocellular carcinoma (HCC) ranks high among the most common and fatal cancers in the world. HCC develops from chronic liver diseases, especially from hepatitis C virus-related and hepatitis B virus (HBV)-related liver diseases. In this sense, useful biomarkers for HCC detection for the patients at risk of HCC are quite important. Recently, new therapies for HCC have been developed, and the prognosis of the patients has improved. However, considering the recurrence rate of HCC after treatment is very high, biomarkers that detect recurrence at an early stage are also required. In addition, since new drugs such as multikinase inhibitors have been introduced to the clinical scene, surrogate biomarkers to predict the effectiveness of treatment will be required in the near future. So far, many biomarkers for HCC have been developed, and their clinical usefulness has been assessed. As a result, several biomarkers for HCC are widely used. However, investigations to discover more useful biomarkers that fit in clinical settings are under way. In this review article, biomarkers for HCC are overviewed to examine their clinical usefulness.

Advances in liver cancer antibody therapies: a focus on glypican-3 and mesothelin

Liver cancer is one of the most common malignancies worldwide. Hepatocellular carcinoma (HCC) and cholangiocarcinoma (CCA) are the two most common primary liver cancers, yet there have been no significant advances in effective therapeutics. There is an urgent need to identify molecular targets for the development of novel therapeutic approaches. In this review, glypican-3 (GPC3) and mesothelin are discussed, with a focus on their potential as targets for antibody therapy in liver cancer. GPC3 and mesothelin are glycosylphosphatidylinositol-anchored proteins present on the cell surface. They are attractive candidates for liver cancer therapy given that GPC3 and mesothelin show high expression in HCC and CCA, respectively. Antibody drugs targeting GPC3 or mesothelin have shown anti-cancer activity in mice. Humanized or chimeric IgG molecules based on first-generation murine monoclonal antibodies against these antigens are being evaluated in clinical studies. Recently, fully human monoclonal antibodies against GPC3 and mesothelin have been isolated by antibody phage display technology that may provide opportunities for novel cancer therapy.

Therapeutic potential of targeting glypican-3 in hepatocellular carcinoma

Glypican-3 (GPC3) is a developmentally-regulated oncofetal protein that has been established as a clinically-relevant biomarker for early hepatocellular carcinoma (HCC). It is one of the first transcripts to appear during malignant hepatocyte transformation, and is expressed at the protein level in approximately half of high-grade dysplastic macronodules in cirrhotic liver. Several studies show it is expressed in most (75 to 100%) of HCCs confirmed by histopathology. The protein is anchored to the hepatocyte membrane by a glycosyl-phosphatidylinositol (GPI) anchor and shows consistent membrane immunostaining pattern, making it a viable target for immunotherapeutic approaches. Targeting GPC3 for therapeutic intervention is a promising approach for the clinical management of HCC and selected other tumors that express the marker.

Points of therapeutic intervention along the Wnt signaling pathway in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the third leading cause of cancer mortality worldwide. However, there is little known about targeted therapeutics for the treatment of this devastating tumor. Among the growth factor signaling cascades deregulated in HCC, evidences suggest that the WNT/Frizzled-mediated signaling pathway plays a key role in the hepatic carcinogenesis. Aberrant activation of the signaling in HCC is mostly due to deregulated expression of the Wnt/β-catenin signaling components. This leads to the activation of the β-catenin/TCF dependent target genes, which controls cell proliferation, cell cycle, apoptosis or motility. It has been shown that disruption of the Wnt/β-catenin signaling cascade displayed anti-cancer properties in HCC. Currently, no therapeutic molecules targeting the WNT pathway are available or under clinical evaluation for the treatment of HCC. This review will discuss the identified potential molecular targets related to the canonical WNT signaling pathway and their potential therapeutic usefulness.

Glypican-3: a new target for cancer immunotherapy

Hepatocellular carcinoma (HCC) remains a common malignant cancer worldwide. There is an urgent need to identify new molecular targets for the development of novel therapeutic approaches. Herein, we review the structure, function and biology of glypican-3 (GPC3) and its role in human cancer with a focus on its potential as a therapeutic target for immunotherapy. GPC3 is a cell-surface protein that is over-expressed in HCC. Loss-of-function mutations of GPC3 cause Simpson-Golabi-Behmel syndrome (SGBS), a rare X-linked overgrowth condition. GPC3 binds Wnt and Hedgehog (Hh) signalling proteins. GPC3 is also able to bind basic growth factors such as fibroblast growth factor 2 through its heparan sulphate glycan chains. GPC3 is a promising candidate for liver cancer therapy given that it shows high expression in HCC. An anti-GPC3 monoclonal antibody has shown anti-cancer activity in mice and its humanised IgG molecule is currently undergoing clinical evaluation in patients with HCC. There is also evidence that soluble GPC3 may be a useful serum biomarker for HCC.

Glypicans

The glypican family of cell-surface heparan sulfate proteoglycans modulate the actions of many developmentally important signal proteins.

Glypicans are heparan sulfate proteoglycans that are bound to the outer surface of the plasma membrane by a glycosyl-phosphatidylinositol anchor. Homologs of glypicans are found throughout the Eumetazoa. There are six family members in mammals (GPC1 to GPC6). Glypicans can be released from the cell surface by a lipase called Notum, and most of them are subjected to endoproteolytic cleavage by furin-like convertases. In vivo evidence published so far indicates that the main function of membrane-attached glypicans is to regulate the signaling of Wnts, Hedgehogs, fibroblast growth factors and bone morphogenetic proteins (BMPs). Depending on the context, glypicans may have a stimulatory or inhibitory activity on signaling. In the case of Wnt, it has been proposed that the stimulatory mechanism is based on the ability of glypicans to facilitate and/or stabilize the interaction of Wnts with their signaling receptors, the Frizzled proteins. On the other hand, GPC3 has recently been reported to inhibit Hedgehog protein signaling during development by competing with Patched, the Hedgehog receptor, for Hedgehog binding. Surprisingly, the regulatory activity of glypicans in the Wnt, Hedgehog and BMP signaling pathways is only partially dependent on the heparan sulfate chains.

Methylation analysis of the glypican 3 gene in embryonal tumours

We have previously shown that the glypican 3 (GPC3) gene was expressed in neuroblastoma (NB) and Wilms' tumour (WT), two embryonal tumours. GPC3 is an X-linked gene that has its peak expression during development and that is downregulated in all investigated tissues after birth. GPC3 expression could be involved in the aetiology of embryonal tumours such as NB and WT. Methylation is known to play a role in gene silencing, notably in chromosome X inactivation. Southern blot- and PCR-based methylation assays were used to assess the methylation status of the GPC3 promoter on genomic DNA from both normal and embryonal tumour cells. In normal cells, the promoter was not methylated in males and partially methylated in females. Our results suggest that DNA methylation of the promoter region is not essential for the transcriptional repression of the GPC3 gene and that the methylation observed in females is probably linked to the inactive X chromosome. In tumour samples, methylation abnormalities have been found exclusively in female NB samples (loss of methylation) and mainly in male WT samples (gain of methylation). Overall, methylation did not significantly correlate with the expression status of GPC3. Although promoter methylation is likely to affect the expression status of the gene, our results suggest that the deregulation of GPC3 transcriptional expression seen in NB and WT involves other regulatory levels.

Identification of Soluble NH2-Terminal Fragment of Glypican-3 as a Serological Marker for Early-Stage Hepatocellular Carcinoma

For detection of hepatocellular carcinoma (HCC) in patients with liver cirrhosis, serum alpha-fetoprotein has been widely used, but its sensitivity has not been satisfactory, especially in small, well-differentiated HCC, and complementary serum marker has been clinically required. Glypican-3 (GPC3), a heparan sulfate proteoglycan anchored to the plasma membrane, is a good candidate marker of HCC because it is an oncofetal protein overexpressed in HCC at both the mRNA and protein levels. In this study, we demonstrated that its NH(2)-terminal portion [soluble GPC3 (sGPC3)] is cleaved between Arg(358) and Ser(359) of GPC3 and that sGPC3 can be specifically detected in the sera of patients with HCC. Serum levels of sGPC3 were 4.84 +/- 8.91 ng/ml in HCC, significantly higher than the levels seen in liver cirrhosis (1.09 +/- 0.74 ng/ml; P < 0.01) and healthy controls (0.65 +/- 0.32 ng/ml; P < 0.001). In well- or moderately-differentiated HCC, sGPC3 was superior to alpha-fetoprotein in sensitivity, and a combination measurement of both markers improved overall sensitivity from 50% to 72%. These results indicate that sGPC3 is a novel serological marker essential for the early detection of HCC.

Glypican-3 is involved in cellular protection against mitoxantrone in gastric carcinoma cells

Elevated expression of the heparan sulphate proteoglycan glypican-3 (GPC3) was found on mRNA and protein levels in the atypical multidrug-resistant gastric carcinoma cell line EPG85-257RNOV, which was established by in vitro selection against mitoxantrone. In order to elucidate a putative role of GPC3 in the drug-resistant phenotype, the mitoxantrone-resistant cell line EPG85-257RNOV was transfected with an expression vector construct carrying an anti-GPC3 hammerhead ribozyme. It could be demonstrated that in anti-GPC3 ribozyme-transfected cell clones, the GPC3-specific mRNA and corresponding protein expression levels were decreased to levels that are similar to those observed in nonresistant, parental cells. The anti-GPC3 ribozyme-containing clones reduced the mitoxantrone resistance level up to 21% of the original resistance and the crossresistance against etoposide to 33% of the original value. This reversal of drug resistance was accompanied by an increased cellular mitoxantrone accumulation in the anti-GPC3 ribozyme-expressing cells. In conclusion, it was verified that GPC3 is involved in the cellular protection against mitoxantrone in the atypical multidrug-resistant gastric carcinoma cell line EPG85-257RNOV.

GPC5 is a possible target for the 13q31-q32 amplification detected in lymphoma cell lines

Comparative genomic hybridization (CGH) analyses have detected gains of copy number on 13q, especially at 13q31-q32, in cell lines and primary cases of various types of lymphoma. Since amplification of chromosomal DNA is one of the mechanisms that can activate tumor-associated genes, and because 13q amplification had been reported in various other types of tumors as well, we attempted to define by fluorescence in situ hybridization (FISH) a common region at 13q31-q32 in which to explore genes that might be targets for the amplification events. Although the commonly amplified region we defined was relatively large (approximately 4 Mb), only one true gene, GPC5, was found there. GPC5 was over-expressed in lymphoma cell lines that had shown amplification, in comparison with those that had not. Our findings suggest that GPC5 is a likely target for amplification, and that over-expression of this gene may contribute to development and/or progression of lymphomas and other tumors.

The contribution of in vivo manipulation of gene expression to the understanding of the function of glypicans

The name glypican identifies a family of heparan sulfate proteoglycans that are linked to the cell surface by a glycosylphosphatidylinositol anchor. Members of this family have been identified in Drosophila, zebrafish, and mammals. The interest in the study of glypicans has increased in the last few years as a result of the discovery that the glypican-3 gene (GPC-3) is mutated in an overgrowth and dysmorphic syndrome. Despite the increased interest, our knowledge about the function of glypicans is still limited, since the molecular basis for the role of glypican-3 in the regulation of body size remains unknown. The in vivo manipulation of glypican expression in lower organisms, however, has demonstrated that these proteoglycans can modulate cellular responses to Wnts and bone morphogenetic factors. Future studies should investigate whether the phenotype of GPC-3-deficient individuals is also due to altered modulation of cellular responses to these factors.

Expression of GPC3, an X-linked recessive overgrowth gene, is silenced in malignant mesothelioma

Gene expression changes in rat asbestos-induced malignant mesothelioma (MM) cells were investigated by differential mRNA display. A mRNA transcript identified by this approach was abundant in normal rat mesothelial cells but not expressed in rat MM cell lines. Northern blot analysis confirmed that this transcript is uniformly silenced in rat MM cell lines and primary tumors. Nucleotide sequence analysis revealed that this transcript is encoded by the rat glypican 3 gene (GPC3), whose human homolog is mutated in the Simpson-Golabi-Behmel overgrowth syndrome. Allelic loss at the GPC3 locus was infrequent (6.9%) in MM cell lines, and no mutations were found. GPC3 transcript levels were markedly decreased in 16 of 18 primary tumors and 17 of 22 human MM cell lines. Most of the cell lines were shown to have aberrant methylation of the GPC3 promoter region. In two of four human MM cell lines tested, GPC3 expression was restored after 2-deoxy 5-azacytidine (DAC)-mediated demethylation of its promoter region. Ectopic expression of GPC3 inhibited in vitro colony formation of human MM cells. Collectively, these data suggest that down-regulation of GPC3 is a common occurrence in MM and that GPC3, an X-linked recessive overgrowth gene, may encode a negative regulator of mesothelial cell growth.

The cell-surface heparan sulfate proteoglycan glypican-1 regulates growth factor action in pancreatic carcinoma cells and is overexpressed in human pancreatic cancer

Heparan sulfate proteoglycans (HSPGs) play diverse roles in cell recognition, growth, and adhesion. In vitro studies suggest that cell-surface HSPGs act as coreceptors for heparin-binding mitogenic growth factors. Here we show that the glycosylphosphatidylinositol- (GPI-) anchored HSPG glypican-1 is strongly expressed in human pancreatic cancer, both by the cancer cells and the adjacent fibroblasts, whereas expression of glypican-1 is low in the normal pancreas and in chronic pancreatitis. Treatment of two pancreatic cancer cell lines, which express glypican-1, with the enzyme phosphoinositide-specific phospholipase-C (PI-PLC) abrogated their mitogenic responses to two heparin-binding growth factors that are commonly overexpressed in pancreatic cancer: fibroblast growth factor 2 (FGF2) and heparin-binding EGF-like growth factor (HB-EGF). PI-PLC did not alter the response to the non-heparin-binding growth factors EGF and IGF-1. Stable expression of a form of glypican-1 engineered to possess a transmembrane domain instead of a GPI anchor conferred resistance to the inhibitory effects of PI-PLC on growth factor responsiveness. Furthermore, transfection of a glypican-1 antisense construct attenuated glypican-1 protein levels and the mitogenic response to FGF2 and HB-EGF. We propose that glypican-1 plays an essential role in the responses of pancreatic cancer cells to certain mitogenic stimuli, that it is relatively unique in relation to other HSPGs, and that its expression by pancreatic cancer cells may be of importance in the pathobiology of this disorder.

OCI-5/GPC3, a glypican encoded by a gene that is mutated in the Simpson-Golabi-Behmel overgrowth syndrome, induces apoptosis in a cell line-specific manner

OCI-5/GPC3 is a member of the glypican family. Glypicans are heparan sulfate proteoglycans that are bound to the cell surface through a glycosyl-phosphatidylinositol anchor. It has recently been shown that the OCI-5/GPC3 gene is mutated in patients with the Simpson-Golabi-Behmel Syndrome (SGBS), an X-linked disorder characterized by pre- and postnatal overgrowth and various visceral and skeletal dysmorphisms. Some of these dysmorphisms could be the result of deficient growth inhibition or apoptosis in certain cell types during development. Here we present evidence indicating that OCI-5/GPC3 induces apoptosis in cell lines derived from mesothelioma (II14) and breast cancer (MCF-7). This induction, however, is cell line specific since it is not observed in NIH 3T3 fibroblasts or HT-29 colorectal tumor cells. We also show that the apoptosis-inducing activity in II14 and MCF-7 cells requires the anchoring of OCI-5/GPC3 to the cell membrane. The glycosaminoglycan chains, on the other hand, are not required. MCF-7 cells can be rescued from OCI-5/GPC3-induced cell death by insulin-like growth factor 2. This factor has been implicated in Beckwith-Wiedemann, an overgrowth syndrome that has many similarities with SGBS. The discovery that OCI-5/GPC3 is able to induce apoptosis in a cell line- specific manner provides an insight into the mechanism that, at least in part, is responsible for the phenotype of SGBS patients.

Cell adhesion and the integrin-linked kinase regulate the LEF-1 and beta-catenin signaling pathways

The integrin-linked kinase (ILK) is an ankyrin repeat containing serine-threonine protein kinase that can interact directly with the cytoplasmic domains of the beta1 and beta3 integrin subunits and whose kinase activity is modulated by cell-extracellular matrix interactions. Overexpression of constitutively active ILK results in loss of cell-cell adhesion, anchorage-independent growth, and tumorigenicity in nude mice. We now show that modest overexpression of ILK in intestinal epithelial cells as well as in mammary epithelial cells results in an invasive phenotype concomitant with a down-regulation of E-cadherin expression, translocation of beta-catenin to the nucleus, formation of a complex between beta-catenin and the high mobility group transcription factor, LEF-1, and transcriptional activation by this LEF-1/beta-catenin complex. We also find that LEF-1 protein expression is rapidly modulated by cell detachment from the extracellular matrix, and that LEF-1 protein levels are constitutively up-regulated at ILK overexpression. These effects are specific for ILK, because transformation by activated H-ras or v-src oncogenes do not result in the activation of LEF-1/beta-catenin. The results demonstrate that the oncogenic properties of ILK involve activation of the LEF-1/beta-catenin signaling pathway, and also suggest ILK-mediated cross-talk between cell-matrix interactions and cell-cell adhesion as well as components of the Wnt signaling pathway.

Syndecan-1 is up-regulated in ras-transformed intestinal epithelial cells

The syndecans, a family of cell-surface heparan sulphate proteoglycans, have been proposed to mediate cellular interactions with extracellular effector molecules, such as growth factors and components of the extracellular matrix, during critical phases of development. Transcripts of all four syndecans are expressed at varying levels in the developing rat intestine and in a series of immature rat intestinal epithelial cell lines. In addition, we report the novel finding that, in the intestinal epithelial cell lines, expression of syndecan-1 transcript is up-regulated by transformation with activated H-ras. This is in contrast to other cell lines in which ras transformation is associated with a decrease in syndecan-1 levels. The observed increase in the syndecan-1 occurs as a result of increased transcription and can be correlated with the degree of transformation of the IEC-18 cells. Transformation is also associated with a decrease in apparent molecular weight and increased shedding of the proteoglycan into the culture medium. Increased shedding of syndecan-1 into the culture medium after transformation with H-ras may contribute to the disruption of proteoglycan interactions with the extracellular matrix, leading to alterations in cell adhesion and organization.

Glypican-3 is a binding protein on the HepG2 cell surface for tissue factor pathway inhibitor

Tissue factor pathway inhibitor (TFPI) is a primary regulator of the initiation of blood coagulation. TFPI is internalized and degraded by HepG2 cells through the low-density-lipoprotein receptor-related protein (LRP) but also binds another molecule present on the cell surface at approx. 10-fold the abundance of LRP [Warshawsky, Broze and Schwartz (1994) Proc. Natl. Acad. Sci. U.S.A. 91, 6664-6668]. When HepG2 cells are washed with heparin or dextran sulphate, a substance that binds TFPI is removed from the cell surface and can be detected in a slot-blot assay. Preincubation with trypsin destroys the reactivity of the TFPI-binding component in the slot-blot assay, suggesting that it is a protein. In addition, when the sulphation of glycosaminoglycans (GAGs) is prevented by growing the HepG2 cells in the presence of 30 mM sodium chlorate, TFPI binding is unaffected, whereas the binding of bovine lipoprotein lipase, a protein known to associate with cell-surface GAGs, falls to 50% of control levels. Dextran sulphate washes of HepG2 cells grown in sodium chlorate have an equal reactivity in slot-blot experiments to that of non-treated cells, suggesting that GAGs are not totally responsible for the binding activity observed. By using the slot blot to follow binding activity and conventional protein purification techniques, a protein species that migrates at 40 kDa after reduction was identified in the HepG2 cell wash. The binding of this protein to TFPI was confirmed with immobilized TFPI. Amino acid sequence analysis identified this protein species as a proteolytic fragment of glypican-3 (also called OCI-5), a member of the glypican family of glycosylphosphatidylinositol-anchored proteoglycans.

Heparan sulfate expression in polarized epithelial cells: the apical sorting of glypican (GPI-anchored proteoglycan) is inversely related to its heparan sulfate content

Several processes that occur in the luminal compartments of the tissues are modulated by heparin-like polysaccharides. To identify proteins responsible for the expression of heparan sulfate at the apex of polarized cells, we investigated the polarity of the expression of the cell surface heparan sulfate proteoglycans in CaCo-2 cells. Domain-specific biotinylation of the apical and basolateral membranes of these cells identified glypican, a GPI-linked heparan sulfate proteoglycan, as the major source of apical heparan sulfate. Yet, most of this proteoglycan was expressed at the basolateral surface, an unexpected finding for a glypiated protein. Metabolic labeling and chase experiments indicated that sorting mechanisms, rather than differential turnover, accounted for this bipolar expression of glypican. Chlorate treatment did not affect the polarity of the expression of glypican in CaCo-2 cells, and transfectant MDCK cells expressed wild-type glypican and a syndecan-4/glypican chimera also in an essentially unpolarized fashion. Yet, complete removal of the heparan sulfate glycanation sites from the glypican core protein resulted in the nearly exclusive apical targeting of glypican in the transfectants, whereas two- and one-chain mutant forms had intermediate distributions. These results indicate that glypican accounts for the expression of apical heparan sulfate, but that glycanation of the core protein antagonizes the activity of the apical sorting signal conveyed by the GPI anchor of this proteoglycan. A possible implication of these findings is that heparan sulfate glycanation may be a determinant of the subcellular expression of glypican. Alternatively, inverse glycanation-apical sorting relationships in glypican may insure near constant deliveries of HS to the apical compartment, or "active" GPI-mediated entry of heparan sulfate into apical membrane compartments may require the overriding of this antagonizing effect of the heparan sulfate chains.

Identification of a new membrane-bound heparan sulphate proteoglycan

The morphological changes that occur during intestinal development have been extensively described, but the molecular basis of these changes is largely unknown. As a result of our efforts to identify molecules that play a role in intestinal morphogenesis during development, we have previously isolated a cDNA that is developmentally regulated in the intestine. This cDNA, named OCI-5, was recently shown to have 20-25% identity at the protein-sequence level with glypican and cerebroglycan, two heparan sulphate proteoglycans (HSPG) that are attached to the cell membrane by a glycosyl-phosphatidylinositol (GPI) anchor. Here we provide experimental evidence indicating that OCI-5 is also a GPI-linked HSPG. We demonstrate this by showing that OCI-5 can be labelled with radioactive sulphate and can be digested by heparitinase, but not by chondroitinase. We also show that treatment with phosphatidylinositol-specific phospholipase C releases OCI-5 from the cell surface of COS cells transfected with an OCI-5 expression vector. The identification of OCI-5 as a GPI-linked HSPG confirms that this proteoglycan belongs to the same family of HSPGs that include glypican and cerebroglycan.

K-glypican: a novel GPI-anchored heparan sulfate proteoglycan that is highly expressed in developing brain and kidney

Glypicans are a family of glycosylphosphatidylinositol (GPI)-anchored cell surface heparan sulfate proteoglycans (HSPGs). The glypican family, which currently includes glypican, the developmentally regulated rat intestinal transcript OCI-5, and cerebroglycan, is characterized by a similar core protein size and almost complete conservation of cysteine residues. By RT-PCR using degenerate oligonucleotide primers based on the sequence homologies, we isolated mouse cDNA encoding a novel member of the glypican family as well as mouse homologues of glypican and OCI-5. The novel molecule, named K-glypican, has a predicted molecular mass of 57.5 kD and potential attachment sites for heparan sulfate chains and a GPI anchor in its COOH-terminal region, like other members of the glypican family. Transfection of an epitope-tagged full-length K-glypican cDNA into MDCK cells demonstrated that K-glypican is indeed expressed as a GPI-anchored HSPG. Northern blot analyses with K-glypican, glypican, and OCI-5 probes demonstrated that kidney and developing brain, and that these three molecules show remarkable patterns of cell type- and developmental stage-specific expression. In situ hybridization revealed that the major sites of K-glypican expression in developing embryo are tubular epithelial cells in the kidney and proliferating neuroepithelial cells in the brain. These results indicate that K-glypican is a novel GPI-anchored HSPG involved in embryonic development.

Cerebroglycan: an integral membrane heparan sulfate proteoglycan that is unique to the developing nervous system and expressed specifically during neuronal differentiation

Heparan sulfate proteoglycans (HSPGs) are found on the surface of all adherent cells and participate in the binding of growth factors, extracellular matrix glycoproteins, cell adhesion molecules, and proteases and antiproteases. We report here the cloning and pattern of expression of cerebroglycan, a glycosylphosphatidylinositol (GPI)-anchored HSPG that is found in the developing rat brain (previously referred to as HSPG M13; Herndon, M. E., and A. D. Lander. 1990. Neuron. 4:949-961). The cerebroglycan core protein has a predicted molecular mass of 58.6 kD and five potential heparan sulfate attachment sites. Together with glypican (David, G., V. Lories, B. Decock, P. Marynen, J.-J. Cassiman, and H. Van den Berghe. 1990. J. Cell Biol. 111:3165-3176), it defines a family of integral membrane HSPGs characterized by GPI linkage and conserved structural motifs, including a pattern of 14 cysteine residues that is absolutely conserved. Unlike other known integral membrane HSPGs, including glypican and members of the syndecan family of transmembrane proteoglycans, cerebroglycan is expressed in only one tissue: the nervous system. In situ hybridization experiments at several developmental stages strongly suggest that cerebroglycan message is widely and transiently expressed by immature neurons, appearing around the time of final mitosis and disappearing after cell migration and axon outgrowth have been completed. These results suggest that cerebroglycan may fulfill a function related to the motile behaviors of developing neurons.

Activated T cells express a novel gene on chromosome 8 that is closely related to the murine ecotropic retroviral receptor

A novel cDNA clone (20.5) which is differentially expressed between two closely related T-lymphoma cell clones was isolated by subtraction-enriched differential screening. SL12.4 cells, from which the cDNA was isolated, have characteristics of thymocytes at an intermediate stage in development. A sister cell clone derived from the same tumor, SL12.3, does not express this mRNA, has a distinct phenotype, and expresses fewer genes required for mature T-cell function. The cDNA sequence predicts a highly hydrophobic protein (approximately 49.5 kilodaltons) which contains seven putative membrane spanning domains. The gene was expressed on concanavalin A-activated T lymphocytes and was designated Tea (T-cell early activation gene). The Tea gene mapped to chromosome 8 and appeared to be conserved among mammalian and avian species. The Tea gene is distinct from, but bears extensive amino acid and DNA sequence similarity with, the murine ecotropic retroviral receptor which is encoded by the Rec-1 gene. Neither gene product displayed significant homology with other known transmembrane-spanning proteins. Thus, the Tea and Rec-1 genes establish a new family encoding multiple membrane-spanning proteins.

Activated T cells express a novel gene on chromosome 8 that is closely related to the murine ecotropic retroviral receptor

A novel cDNA clone (20.5) which is differentially expressed between two closely related T-lymphoma cell clones was isolated by subtraction-enriched differential screening. SL12.4 cells, from which the cDNA was isolated, have characteristics of thymocytes at an intermediate stage in development. A sister cell clone derived from the same tumor, SL12.3, does not express this mRNA, has a distinct phenotype, and expresses fewer genes required for mature T-cell function. The cDNA sequence predicts a highly hydrophobic protein (approximately 49.5 kilodaltons) which contains seven putative membrane spanning domains. The gene was expressed on concanavalin A-activated T lymphocytes and was designated Tea (T-cell early activation gene). The Tea gene mapped to chromosome 8 and appeared to be conserved among mammalian and avian species. The Tea gene is distinct from, but bears extensive amino acid and DNA sequence similarity with, the murine ecotropic retroviral receptor which is encoded by the Rec-1 gene. Neither gene product displayed significant homology with other known transmembrane-spanning proteins. Thus, the Tea and Rec-1 genes establish a new family encoding multiple membrane-spanning proteins.