Glypican-3-mediated oncogenesis involves the Insulin-like growth factor-signaling pathway

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.

Silencing glypican-3 expression induces apoptosis in human hepatocellular carcinoma cells

Hepatocellular carcinoma (HCC) is one of the most common internal malignant tumors. Glypican-3 (GPC3) is involved in the biological and molecular events in the tumorigenesis of HCC. We used RNA interference to evaluate the molecular effects of GPC3 suppression at the translational level and demonstrated for the first time that GPC3 silencing results in a significant elevation of the Bax/Bcl-2 ratio, the release of cytochrome c from mitochondria and the activation of caspase-3. The results suggest that GPC3 regulates cell proliferation by enhancing the resistance to apoptosis through the dysfunction of the Bax/Bcl-2/cytochrome c/caspase-3 signaling pathway and therefore plays a critical role in the tumorigenesis of HCC. Thus, the knockdown of GPC3 should be further investigated as an attractive novel approach for the targeted gene therapy of HCC.

Crystal structure of N-glycosylated human glypican-1 core protein: structure of two loops evolutionarily conserved in vertebrate glypican-1

Glypicans are a family of cell-surface proteoglycans that regulate Wnt, hedgehog, bone morphogenetic protein, and fibroblast growth factor signaling. Loss-of-function mutations in glypican core proteins and in glycosaminoglycan-synthesizing enzymes have revealed that glypican core proteins and their glycosaminoglycan chains are important in shaping animal development. Glypican core proteins consist of a stable α-helical domain containing 14 conserved Cys residues followed by a glycosaminoglycan attachment domain that becomes exclusively substituted with heparan sulfate (HS) and presumably adopts a random coil conformation. Removal of the α-helical domain results in almost exclusive addition of the glycosaminoglycan chondroitin sulfate, suggesting that factors in the α-helical domain promote assembly of HS. Glypican-1 is involved in brain development and is one of six members of the vertebrate family of glypicans. We expressed and crystallized N-glycosylated human glypican-1 lacking HS and N-glycosylated glypican-1 lacking the HS attachment domain. The crystal structure of glypican-1 was solved using crystals of selenomethionine-labeled glypican-1 core protein lacking the HS domain. No additional electron density was observed for crystals of glypican-1 containing the HS attachment domain, and CD spectra of the two protein species were highly similar. The crystal structure of N-glycosylated human glypican-1 core protein at 2.5 Å, the first crystal structure of a vertebrate glypican, reveals the complete disulfide bond arrangement of the conserved Cys residues, and it also extends the structural knowledge of glypicans for one α-helix and two long loops. Importantly, the loops are evolutionarily conserved in vertebrate glypican-1, and one of them is involved in glycosaminoglycan class determination.

Suppression of glypican 3 inhibits growth of hepatocellular carcinoma cells through up-regulation of TGF-β2

Glypican 3 (GPC3) is a valuable diagnostic marker and a potential therapeutic target in hepatocellular carcinoma (HCC). To evaluate the efficacy of targeting GPC3 at the translational level, we used RNA interference to examine the biologic and molecular effects of GPC3 suppression in HCC cells in vitro and in vivo. Transfection of Huh7 and HepG2 cells with GPC3-specific small interfering RNA (siRNA) inhibited cell proliferation (P < .001) together with cell cycle arrest at the G(1) phase, down-regulation of antiapoptotic protein (Bcl-2, Bcl-xL, and Mcl-1), and replicative senescence. Gene expression analysis revealed that GPC3 suppression significantly correlated with transforming growth factor beta receptor (TGFBR) pathway (P = 4.57e-5) and upregulated TGF-β2 at both RNA and protein levels. The effects of GPC3 suppression by siRNA can be recapitulated by addition of human recombinant TGF-β2 to HCC cells in culture, suggesting the possible involvement of TGF-β2 in growth inhibition of HCC cells. Cotransfection of siRNA-GPC3 with siRNA-TGF-β2 partially attenuated the effects of GPC3 suppression on cell proliferation, cell cycle progression, apoptosis, and replicative senescence, confirming the involvement of TGF-β2 in siRNA-GPC3-mediated growth suppression. In vivo, GPC3 suppression significantly inhibited the growth of orthotopic xenografts of Huh7 and HepG2 cells (P < .05), accompanied by increased TGF-β2 expression, reduced cell proliferation (observed by proliferating cell nuclear antigen staining), and enhanced apoptosis (by TUNEL staining). In conclusion, molecular targeting of GPC3 at the translational level offers an effective option for the clinical management of GPC3-positive HCC patients.

Oncofetal antigen glypican-3 as a promising early diagnostic marker for hepatocellular carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) is characterized by a multi-cause, multi-stage and multi-focus process of tumor progression. Its prognosis is poor and early diagnosis is of utmost importance. This study was undertaken to investigate the dynamic expression of oncofetal antigen glypican-3 (GPC-3) and GPC-3 mRNA in hepatocarcinogenesis and to explore their early diagnostic value for HCC.

METHODS

A hepatoma model was induced in male Sprague-Dawley rats with 0.05% 2-fluorenylacetamide and confirmed by hematoxylin and eosin staining and gamma-glutamyltransferase (GGT) expression. Total RNA was purified and transcribed into cDNA by reverse transcription. Fragments of the GPC-3 gene were amplified by nested RT-PCR, and confirmed by sequencing. GPC-3 was analyzed by immunohistochemistry, Western blotting or ELISA.

RESULTS

Positive GPC-3 expression showed as brown granule-like staining localized in the cytoplasm. Histological examination of hepatocytes revealed three morphological stages of granule-like degeneration, atypical hyperplasia (precancerous), and cancer formation, with a progressive increase of liver total RNA and GGT expression. The incidence of liver GPC-3 mRNA and GPC-3, and serum GPC-3 was 100%, 100% and 77.8% in the HCC group, 100%, 100%, and 66.7% in the precancerous group, 83.3%, 83.3%, and 38.9% in the degeneration group, and no expression in the liver or blood of the control group, respectively. There was a positive correlation between liver GPC-3 mRNA and total RNA level (r=0.475, P<0.05) or liver GPC-3 (r=1.0, P<0.001) or serum GPC-3 (r=0.994, P<0.001).

CONCLUSION

Abnormal oncofetal antigen GPC-3 and GPC-3 mRNA expression in hepatocarcinogenesis may be promising molecular markers for early diagnosis of HCC.

Proteoglycans in cancer biology, tumour microenvironment and angiogenesis

Proteoglycans, key molecular effectors of cell surface and pericellular microenvironments, perform multiple functions in cancer and angiogenesis by virtue of their polyhedric nature and their ability to interact with both ligands and receptors that regulate neoplastic growth and neovascularization. Some proteoglycans such as perlecan, have pro- and anti-angiogenic activities, whereas other proteoglycans, such as syndecans and glypicans, can also directly affect cancer growth by modulating key signalling pathways. The bioactivity of these proteoglycans is further modulated by several classes of enzymes within the tumour microenvironment: (i) sheddases that cleave transmembrane or cell-associated syndecans and glypicans, (ii) various proteinases that cleave the protein core of pericellular proteoglycans and (iii) heparanases and endosulfatases which modify the structure and bioactivity of various heparan sulphate proteoglycans and their bound growth factors. In contrast, some of the small leucine-rich proteoglycans, such as decorin and lumican, act as tumour repressors by physically antagonizing receptor tyrosine kinases including the epidermal growth factor and the Met receptors or integrin receptors thereby evoking anti-survival and pro-apoptotic pathways. In this review we will critically assess the expanding repertoire of molecular interactions attributed to various proteoglycans and will discuss novel proteoglycan functions modulating cancer progression, invasion and metastasis and how these factors regulate the tumour microenvironment.

Construction of expression plasmids carrying miRNA targeting IGF-II and detection of their inhibitory effect on IGF-II expression in human HepG2 cells

AIM: To investigate inhibitory effect of transfection of eukaryotic expression plasmids carrying specific microRNA (miRNA) on insulin-like growth factor II (IGF-II) gene and protein expression in human HepG2 cells.

METHODS: Four miRNAs targeting the IGF-II gene were synthesized and inserted into the pcDNATM6.2-GW/EmGFPmiR vector. The recombinant plasmids were identified and transiently transfected into HepG2 cells. Their inhibitory efficiency on IGF-II expression was determined at gene level by real time-PCR and at protein level by ELISA.

RESULTS: Four eukaryotic expression plasmids carrying miRNA targeting IGF-II were constructed successfully and confirmed by sequencing. HepG2 cells were then transfected with these plasmids (MR-IGF-II-1 to 4). The highest transfection efficiency was up to 50%. The reduced rates of IGF-II gene expression were 33%, 43%, 0% and 3% in cells transfected with MR-IGF-II-1 to 4, respectively. Transfection of the MR-IGF-II-2 plasmid for 72 h reduced IGF-II protein expression by 44% in HepG2 cells.

CONCLUSION: The expression plasmids carrying miRNA targeting IGF-II have been successfully constructed. Transfection of these plamsids can efficiently inhibit IGF-II expression in HepG2 cells.

Glypican 3 binds to GLUT1 and decreases glucose transport activity in hepatocellular carcinoma cells

Glypican 3 (GPC3), a member of heparin sulfate proteoglycans, is attached to the cell surface by a glycosylphosphatidylinositol anchor and is reported to be overexpressed in liver cancers. In order to identify GPC3 binding proteins on the cell surface, we constructed a cDNA containing the C-terminal cell surface-attached form of GPC3 (GPC3c) in a baculoviral vector. The GPC3c bait protein was produced by expressing the construct in Sf21 insect cells and double purified using a His column and Flag immunoprecipitation. Purified GPC3c was used to uncover GPC3c-interacting proteins. Using an LC-MS/MS proteomics strategy, we identified glucose transporter 1 (GLUT1) as a novel GPC3 interacting protein from the HepG2 hepatoma cell lysates. The interaction was confirmed by immunoprecipitation (IP)-WB analysis and surface plasmon resonance (SPR). SPR result showed the interaction of GLUT1 to GPC3c with equilibrium dissociation constants (K(D) ) of 1.61 nM. Moreover, both incubation with GPC3c protein and transfection of Gpc3c cDNA into HepG2 cells resulted in reduced glucose uptake activity. Our results indicate that GPC3 plays a role in glucose transport by interacting with GLUT1.

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.

Characteristics of hepatic igf-ii expression and monitored levels of circulating igf-ii mRNA in metastasis of hepatocellular carcinoma

The prognosis of hepatocellular carcinoma (HCC) remains dismal. Insulin-like growth factor II (IGF-II), a fetal growth factor, is highly expressed during HCC development. We examined serum IGF-II levels and circulating IGF-II messenger RNA (mRNA) expression and analyzed the clinicopathologic characteristics in patients with liver diseases. The higher IGF-II level in the serum of patients with HCC could be correlated with hepatitis B virus infection but not with patient sex, age, tumor size, or α-fetoprotein (AFP) level. Total RNAs were extracted from liver tissues or peripheral blood mononuclear cells, and IGF-II complementary DNA (cDNA) and AFP cDNA were synthesized through random primers and reverse transcriptase; gene fragments were amplified by nested polymerase chain reaction and confirmed by sequencing. The incidence of the hepatic IGF-II gene was 100% in HCC, 54.3% in paracancerous tissues, and none in noncancerous tissues. The incidence rates for circulating IGF-II and AFP genes were 34.3% and 52.7%, respectively, and for both, 61.6% in patients with HCC. They were 100% in cases with extrahepatic metastasis. The IGF-II abnormality associates with HCC, and circulating IGF-II and IGF-II mRNA are useful molecular markers for HCC differential diagnosis and hematogenous metastasis.

Glypican-3-Expressing Hepatocellular Carcinoma in a Non-Cirrhotic Patient with Nonalcoholic Steatohepatitis: Case Report and Literature Review

Hepatocellular carcinoma (HCC) is one of the most common cancers worldwide. Nonalcoholic steatohepatitis (NASH) is now considered as the major cause of cryptogenic cirrhosis, which can progress to HCC. Glypican-3 is a member of the Heparan Sulfate Proteoglycan (HSP) family that plays a role in cell growth, differentiation, and migration. Glypican-3 is significantly up-regulated in a majority of HCCs compared to normal and benign liver samples. Glypican-3 protein is detectable in around 40-53% of HCC patients whereas it is not detectable in the serum of healthy individuals. There are several reports of HCC arising in the setting of non-cirrhotic NASH. This report describes a case of HCC that expressed Glypican-3 and arose in a 47-year-old female with noncirrhotic NASH.

Association of glypican-3 expression with growth signaling molecules in hepatocellular carcinoma

AIM: To clarify the association of glypican-3 (GPC3) expression with Wnt and other growth signaling molecules in hepatocellular carcinoma (HCC).

METHODS: Expression of GPC3, Wnt, matrix metalloproteinases (MMPs), sulfatase (SULF)1, SULF2, and other growth signaling molecules was analyzed in HCC cell lines and tissue samples by real-time reverse transcription-polymerase chain reaction, immunoblotting, and/or immunostaining. Expression of various genes in GPC3 siRNA-transfected HCC cells was analyzed.

RESULTS: GPC3 was overexpressed in most HCCs at mRNA and protein levels and its serum levels were significantly higher in patients with HCC than in non-HCC subjects (P < 0.05). Altered expressions of various MMPs and growth signaling molecules, some of which were correlated with GPC3 expression, were observed in HCCs. Down-regulation of GPC3 expression by siRNA in GPC3-overexpressing HCC cell lines resulted in a significant decrease in expressions of MMP2, MMP14, fibroblast growth factor receptor 1, insulin-like growth factor 1 receptor. GPC3 expression was significantly correlated with nuclear/cytoplasmic localization of β-catenin.

CONCLUSION: These results suggest that GPC3, in conjunction with MMPs and growth signaling molecules, might play an important role in the progression of HCC.

Advances in the relationship between glypican-3 and primary hepatic carcinoma

Glypican-3 (GPC3) is a membrane heparin sulfate proteoglycan that is expressed abundantly in the fetal liver, inactive in the normal adult liver and frequently reactivated in hepatocellular carcinoma (HCC). Serum soluble GPC3 is a new diagnostic and prognostic biomarker for HCC. GPC3 is also a potential target for targeted therapy of HCC. The expression of GPC3 is upregulated at the early stage of HCC, which is associated with sulfatase-2, zinc-fingers and homeoboxes 2 (ZHX2) and alpha-fetoprotein regulator 2 (AFR2). GPC3 overexpression can activate integrin, insulin-like growth factor and Wnt signaling to promote HCC development.

On the origin of serum CD26 and its altered concentration in cancer patients

Dipeptidyl peptidase IV (DPP-IV), assigned to the CD26 cluster, is expressed on epithelial cells and lymphocytes and is a multifunctional or pleiotropic protein. Its peptidase activity causes degradation of many biologically active peptides, e.g. some incretins secreted by the enteroendocrine system. DPP-IV has, therefore, become a novel therapeutic target for inhibitors that extend endogenously produced insulin half-life in diabetics, and several reviews have appeared in recent months concerning the clinical significance of CD26/DPP-IV. Biological fluids contain relatively high levels of soluble CD26 (sCD26). The physiological role of sCD26 and its relation, if any, to CD26 functions, remain poorly understood because whether the process for CD26 secretion and/or shedding from cell membranes is regulated or not is not known. Liver epithelium and lymphocytes are often cited as the most likely source of sCD26. It is important to establish which tissue or organ is the protein source as well as the circumstances that can provoke an abnormal presence/absence or altered levels in many diseases including cancer, so that sCD26 can be validated as a clinical marker or a therapeutic target. For example, we have previously reported low levels of sCD26 in the blood of colorectal cancer patients, which indicated the potential usefulness of the protein as a biomarker for this cancer in early diagnosis, monitoring and prognosis. Through this review, we envisage a role for sCD26 and the alteration of normal peptidase capacity (in clipping enteroendocrine or other peptides) in the complex crosstalk between the lymphoid lineage and, at least, some malignant tumours.

Glypican-3 expression and its correlation with clinicopathological parameters in hepatocellular carcinoma

AIM: To investigate the expression of human glypican-3 (GPC-3) and analyze its correlation with clinicopathological parameters in hepatocellular carcinoma (HCC).

METHODS: Tumor specimens and matched tumor-adjacent and -distant specimens were taken from 36 HCC patients. The expression of GPC-3 in these specimens was detected by immunohistochemistry.

RESULTS: Positive GPC-3 signal was localized in both cell membrane and cytoplasm in HCC, and only in cytoplasm in tumor-adjacent tissue. No positive staining was found in tumor-distant tissue. The positive rate of GPC-3 expression was 80.6% in HCC and 41.7% in tumor-adjacent tissue. The intensity of GPC-3 expression was significantly higher in HCC than in tumor-adjacent and -distant tissues (χ² = 11.445, P < 0.01).

CONCLUSION: GPC-3 expression may be closely associated with the development and progression of HCC and can be used as a molecular marker for HCC diagnosis.

Diagnosis of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the commonest cancers worldwide, particularly in parts of the developing world, and is increasing in incidence. This article reviews the current modalities employed for the diagnosis of HCC, including serum markers, radiological techniques and histological evaluation, and summarises international guidelines for the diagnostic approach to HCC.

Heparin-degrading sulfatases in hepatocellular carcinoma: roles in pathogenesis and therapy targets

Hepatocellular carcinoma (HCC) is often diagnosed at an advanced stage at which there are limited treatment options. Two recently identified human heparin-degrading endosulfatases, named sulfatase 1 (SULF1) and sulfatase 2 (SULF2), have been found to be involved in liver carcinogenesis. SULF1 and SULF2 desulfate cell surface and extracellular matrix heparan sulfate proteoglycans and modulate heparin-binding growth factor signaling in multiple cancers, including HCCs. SULF1 inhibits HCC tumor cell growth in vitro and in nude mice in vivo, partially through effects on gene expression mediated through histone H4 acetylation. While SULF1 is downregulated in the majority of HCC cell lines and approximately 30% of primary HCCs, SULF2 is upregulated in almost all HCC cell lines and in 60% of primary HCCs. In contrast to the tumor suppressor effect of SULF1, expression of SULF2 activates MAPK and Akt pathways, promotes HCC cell growth in vitro and in vivo, and is associated with decreased survival of HCC patients. Targeting SULF2 or the interaction between SULF2 and SULF1 may lead to novel therapeutics for the treatment of HCCs.