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

Current and Future States of Natural Killer Cell-Based Immunotherapy in Hepatocellular Carcinoma

Natural killer (NK) cells are innate lymphoid cells that exhibit high levels of cytotoxicity against NK-specific targets. NK cells also produce various cytokines, and interact with T cells, B cells, and dendritic cells to effectively serve as frontliners of the innate immune system. Produce various cytokines, and interact with T cells, B cells, and dendritic cells to effectively serve as frontliners of the innate immune system. Moreover, NK cells constitute the second most common immune cell in the liver. These properties have drawn significant attention towards leveraging NK cells in treating liver cancer, especially hepatocellular carcinoma (HCC), which accounts for 75% of all primary liver cancer and is the fourth leading cause of cancer-related death worldwide. Notable anti-cancer functions of NK cells against HCC include activating antibody-dependent cell cytotoxicity (ADCC), facilitating Gasdermin E-mediated pyroptosis of HCC cells, and initiating an antitumor response via the cGAS-STING signaling pathway. In this review, we describe how these mechanisms work in the context of HCC. We will then discuss the existing preclinical and clinical studies that leverage NK cell activity to create single and combined immunotherapies.

Oncofetal protein glypican-3 is a biomarker and critical regulator of function for neuroendocrine cells in prostate cancer

Neuroendocrine (NE) cells comprise ~1% of epithelial cells in benign prostate and prostatic adenocarcinoma (PCa). However, they become enriched in hormonally treated and castration-resistant PCa (CRPC). In addition, close to 20% of hormonally treated tumors recur as small cell NE carcinoma (SCNC), composed entirely of NE cells, which may be the result of clonal expansion or lineage plasticity. Since NE cells do not express androgen receptors (ARs), they are resistant to hormonal therapy and contribute to therapy failure. Here, we describe the identification of glypican-3 (GPC3) as an oncofetal cell surface protein specific to NE cells in prostate cancer. Functional studies revealed that GPC3 is critical to the viability of NE tumor cells and tumors displaying NE differentiation and that it regulates calcium homeostasis and signaling. Since our results demonstrate that GPC3 is specifically expressed by NE cells, patients with confirmed SCNC may qualify for GPC3-targeted therapy which has been developed in the context of liver cancer and displays minimal toxicity due to its tumor-specific expression. © 2023 The Pathological Society of Great Britain and Ireland.

Inhibition of Glypican-3 Cleavage Results in Reduced Cell Proliferation in a Liver Cancer Cell Line

INTRODUCTION

Glypican-3 (GPC3) is a surface-bound proteoglycan overexpressed in pediatric liver cancer and utilized clinically as an immunohistochemical tumor marker. Furin is a proprotein convertase that is ubiquitously expressed and shown to modify GPC3 post-translationally. In experimental models of epithelial-based cancers, furin inhibition decreased tumor cell migration and proliferation representing a potential therapeutic target.

METHODS

Using a synthetic furin inhibitor, we evaluated proliferation, migration, protein, and RNA expression in two liver cancer cell lines, HepG2 (GPC3-positive) and SKHep1 cells (GPC3-negative). Total furin protein and GPC3 protein expression were assessed to evaluate functional levels of furin.

RESULTS

There was a reduction in HepG2 proliferation with addition of furin inhibitor at the 48-h timepoint, however there was an increase in HepG2 migration.

CONCLUSIONS

GPC3 cleavage in hepatoblastoma (HB) has a role in cell proliferation with therapeutic potential, however furin inhibition is not an appropriate target for GPC3-expressing HB due to increased migration which may enhance metastatic potential.

Role of glypican-1 in regulating multiple cellular signaling pathways

Glypican-1 (GPC1) is one of the six glypican family members in humans. It is composed of a core protein with three heparan sulfate chains and attached to the cell membrane by a glycosyl-phosphatidylinositol anchor. GPC1 modulates various signaling pathways including fibroblast growth factors (FGF), vascular endothelial growth factor-A (VEGF-A), transforming growth factor-β (TGF-β), Wnt, Hedgehog (Hh), and bone morphogenic protein (BMP) through specific interactions with pathway ligands and receptors. The impact of these interactions on signaling pathways, activating or inhibitory, is dependent upon specific GPC1 domain interaction with pathway components, as well as cell surface context. In this review, we summarize the current understanding of the structure of GPC1, as well as its role in regulating multiple signaling pathways. We focus on the functions of GPC1 in cancer cells and how new insights into these signaling processes can inform its translational potential as a therapeutic target in cancer.

T-Cell Receptor Mimic Antibodies for Cancer Immunotherapy

Antibody-based immunotherapies show clinical effectiveness in various cancer types. However, the target repertoire is limited to surface or soluble antigens, which are a relatively small percentage of the cancer proteome. Most proteins of the human proteome are intracellular. Short peptides from intracellular targets can be presented by MHC class I (MHC-I) molecules on cell surface, making them potential targets for cancer immunotherapy. Antibodies can be developed to target these peptide/MHC complexes, similar to the recognition of such complexes by the T-cell receptor (TCR). These antibodies are referred to as T-cell receptor mimic (TCRm) or TCR-like antibodies. Ongoing preclinical and clinical studies will help us understand their mechanisms of action and selection of target epitopes for immunotherapy. The present review will summarize and discuss the selection of intracellular antigens, production of the peptide/MHC complexes, isolation of TCRm antibodies for therapeutic applications, limitations of TCRm antibodies, and possible ways to advance TCRm antibody-based approaches into the clinic.

Identification of a Glypican-3 Binding Peptide From a Phage-Displayed Peptide Library for PET Imaging of Hepatocellular Carcinoma

Tumor-targeting peptides functioned as molecular probes are essential for multi-modality imaging and molecular-targeting therapy in caner theronostics. Here, we performed a phage-displayed bio-panning to identify a specific binding peptide targeting Glypican-3 (GPC-3), a promising biomarker in hepatocellular carcinoma (HCC). After screening in the cyclic peptide library, a candidate peptide named F3, was isolated and showed specific binding to HCC cell lines. In a bio-distribution study, higher accumulation of F3 peptide was observed in HepG-2 tumors compared to PC-3 tumors in xenograft models. After labeling with radioactive ⁶⁸Ga, the F3 peptide tracer enabled the specific detection of tumors in HCC tumor models with PET imaging. More importantly, the expression of GPC-3 in human tissue samples may be distinguished by an F3 fluorescent peptide probe indicating its potential for clinical application. This cyclic peptide targeting GPC-3 has been validated, and may be an alternative to serve as an imaging probe or a targeting domain in the drug conjugate.

C/EBPβ enhances efficacy of sorafenib in hepatoblastoma

Hepatoblastoma (HB) is the predominant hepatic neoplasm in infants and young children. Sorafenib has been used to treat adult and pediatric hepatocellular carcinoma. However, efficacy of monotherapy of sorafenib in HB is not sustained. In this study, we tested a possible combinatory therapy of sorafenib with the CCAAT/enhancer-binding proteins (C/EBP) overexpression in HB cell line. Firstly, we evaluated the expression level of C/EBPβ in the patients with HB by analyzing The Cancer Genome Atlas data. Lower level of C/EBPβ was observed in tumor tissues in comparison with matched normal tissues. Next, we observed that combination of sorafenib and C/EBPβ overexpression led to dramatic growth and migration inhibition of live tumor cells which implied promising probability for clinical trial. Mechanistically, C/EBPβ which can be downregulated by Ras v12, augmented messenger RNA and protein levels of p53. These data suggested that a combination of sorafenib and C/EBPβ overexpression inhibited tumor growth synergistically and provided a promising approach to treat HB.

Combination of NK-based immunotherapy and sorafenib against hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the most frequent malignancy of the liver, which is considered the fourth leading cause of cancer-related death in the United States. Liver transplant and surgical resection are curative treatments for HCC, but only 10-15% of HCC patients are eligible candidates. The FDA-approved sorafenib is a multi-kinase inhibitor systemic therapy for advanced HCC that extends the overall survival by over 3 months when compared with placebo. Adoptive transfer of Natural Killer (NK) cells holds great promise for clinical cancer treatment. However, only limited clinical benefit has been achieved in cancer patients. Therefore, there is currently considerable interest in development of the combination of sorafenib and NK cells for the treatment of HCC patients. However, the mechanism of how sorafenib affects the function of NK cells remains to be comprehensively clarified. In this paper, we will discuss NK cell-based immunotherapies that are currently under preclinical and clinical investigation and its potential combination with sorafenib for improving the survival of HCC patients.

Identification of the atypical cadherin FAT1 as a novel glypican-3 interacting protein in liver cancer cells

Glypican-3 (GPC3) is a cell surface heparan sulfate proteoglycan that is being evaluated as an emerging therapeutic target in hepatocellular carcinoma (HCC). GPC3 has been shown to interact with several extracellular signaling molecules, including Wnt, HGF, and Hedgehog. Here, we reported a cell surface transmembrane protein (FAT1) as a new GPC3 interacting protein. The GPC3 binding region on FAT1 was initially mapped to the C-terminal region (Q14517, residues 3662-4181), which covered a putative receptor tyrosine phosphatase (RTP)-like domain, a Laminin G-like domain, and five EGF-like domains. Fine mapping by ELISA and flow cytometry showed that the last four EGF-like domains (residues 4013-4181) contained a specific GPC3 binding site, whereas the RTP domain (residues 3662-3788) and the downstream Laminin G-2nd EGF-like region (residues 3829-4050) had non-specific GPC3 binding. In support of their interaction, GPC3 and FAT1 behaved concomitantly or at a similar pattern, e.g. having elevated expression in HCC cells, being up-regulated under hypoxia conditions, and being able to regulate the expression of EMT-related genes Snail, Vimentin, and E-Cadherin and promoting HCC cell migration. Taken together, our study provides the initial evidence for the novel mechanism of GPC3 and FAT1 in promoting HCC cell migration.

Heparan sulfate proteoglycans and their modification as promising anticancer targets in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common types of primary liver cancer. Despite advancements in the treatment strategies of HCC, there is an urgent requirement to identify and develop novel therapeutic drugs that do not lead to resistance. These novel agents should have the potential to influence the primary mechanisms participating in the pathogenesis of HCC. Heparan sulfate proteoglycans (HSPGs) are major elements of the extracellular matrix that perform structural and signaling functions. HSPGs protect against invasion of tumor cells by preventing cell infiltration and intercellular adhesion. Several enzymes, such as heparanase, matrix metalloproteinase-9 and sulfatase-2, have been reported to affect HSPGs, leading to their degradation and thus enhancing tumor invasion. In addition, some compounds that are produced from the degradation of HSPGs, including glypican-3 and syndecan-1, enhance tumor progression. Thus, the identification of enzymes that affect HSPGs or their degradation products in HCC may lead to the development of novel therapeutic targets. The present review discusses the main enzymes and compounds associated with HSPGs, and their involvement with the pathogenicity of HCC.

GPI-AP: Unraveling a New Class of Malignancy Mediators and Potential Immunotherapy Targets

With millions of cases diagnosed annually and high economic burden to cover expensive costs, cancer is one of the most difficult diseases to treat due to late diagnosis and severe adverse effects from conventional therapy. This creates an urgent need to find new targets for early diagnosis and therapy. Progress in research revealed the key steps of carcinogenesis. They are called cancer hallmarks. Zooming in, cancer hallmarks are characterized by ligands binding to their cognate receptor and so triggering signaling cascade within cell to make response for stimulus. Accordingly, understanding membrane topology is vital. In this review, we shall discuss one type of transmembrane proteins: Glycosylphosphatidylinositol-Anchored Proteins (GPI-APs), with specific emphasis on those involved in tumor cells by evading immune surveillance and future applications for diagnosis and immune targeted therapy.

MALAT-1: LncRNA ruling miR-182/PIG-C/mesothelin triad in triple negative breast cancer

Breast cancer (BC) remains a major health problem, despite the remarkable advances in cancer research setting. BC is the most common cancer affecting women worldwide. In the context of triple negative breast cancer (TNBC) treatment, major obstacles include late diagnoses and detrimental side effects of chemotherapy and radiotherapy. Research effort was rewarded with the discovery of mesothelin (MSLN), an oncogenic Glycosyl-Phosphatidyl-Inositol (GPI) anchored protein, over-expressed in TNBC. GPI pathway is a post-translational modification that attaches proteins to cellular membrane. MSLN targeted therapy succeeded in early clinical trials, nevertheless, to date, the epigenetic regulation of MSLN and GPI pathway by non-coding RNAs (nc-RNAs) in BC remains an untouched area. Accordingly, our aim is to investigate-for the first time- the impact of simultaneous targeting of MSLN and its associated GPI pathway member, PIG-C, by non-coding-RNAs. Expression profiling of PIG-C, MSLN in BC was performed. Using bioinformatics tools, MALAT-1 and miR-182 were found to target MSLN and PIG-C. MDA-MB-231 cells were transfected with synthetic nc-RNAs. Expression profiling of MSLN, miR-182 and MALAT-1 showed a dramatic over-expression in BC samples. MiR-182 ectopic expression and MALAT-1 silencing increased MSLN and PIG-C transcript levels. However, miR-182 inhibition and miR-182/si-MALAT-1 co-transfection lowered MSLN and PIG-C levels. Finally, si-PIG-C decreased MSLN and PIG-C levels. To conclude, our investigation unravels a new axis in TNBC, where miR-182 can manipulate MSLN and PIG-C. Meanwhile, MALAT-1 is the culprit lncRNA in this novel axis, possibly a sponge for miR-182. Altogether, this sheds light on new targets for BC immune-therapy.

hGC33-Modified and Sorafenib-Loaded Nanoparticles have a Synergistic Anti-Hepatoma Effect by Inhibiting Wnt Signaling Pathway

Delivery of tumor-specific inhibitors is a challenge in cancer treatment. Antibody-modified nanoparticles can deliver their loaded drugs to tumor cells that overexpress specific tumor-associated antigens. Here, we constructed sorafenib-loaded polyethylene glycol-b-PLGA polymer nanoparticles modified with antibody hGC33 to glypican-3 (GPC3 +), a membrane protein overexpressed in hepatocellular carcinoma. We found that hGC33-modified NPs (hGC33-SFB-NP) targeted GPC3⁺ hepatocellular carcinoma (HCC) cells by specifically binding to GPC3 on the surface of HCC cells, inhibited Wnt-induced signal transduction, and inhibited HCC cells in G0/1 by down-regulating cyclin D1 expression, thus attenuating HCC cell migration by inhibiting epithelial-mesenchymal transition. hGC33-SFB-NP inhibited the migration, cycle progression, and proliferation of HCC cells by inhibiting the Ras/Raf/MAPK pathway and the Wnt pathway in tandem with GPC3 molecules, respectively. hGC33-SFB-NP inhibited the growth of liver cancer in vivo and improved the survival rate of tumor-bearing mice. We conclude that hGC33 increases the targeting of SFB-NP to HCC cells. hGC33-SFB-NP synergistically inhibits the progression of HCC by blocking the Wnt pathway and the Ras/Raf/MAPK pathway.

The Role of Glypicans in Cancer Progression and Therapy

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

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

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

Next-Generation Antibody Therapeutics: Discovery, Development and Beyond: highlights of the third annual conference of the Chinese Antibody Society

The Chinese Antibody Society (CAS) convened the third annual conference in Cambridge, Massachusetts, USA on April 7, 2019. More than 600 global members attended the meeting. The theme of this conference was Next-Generation Antibody Therapeutics: Discovery, Development and Beyond. The meeting covered a vast variety of topics including cancer immunotherapy, single-domain antibodies as well as bispecific antibodies, immunotoxins, transgenic mouse platforms for next-generation monoclonal antibody discovery and antibody chemistry, manufacturing and controls (CMCs). Two hot topics were comprehensively discussed by the prestigious panelists and hosts at the panel discussions during the conferences, i.e., bispecific antibodies and antibody CMC.

Statement of Significance: The Chinese Antibody Society convened the third annual conference in Cambridge, Massachusetts, USA on 7 April 2019. The meeting covered a variety of topics, including cancer immunotherapy, single-domain antibody, bispecific antibody, immunotoxin, transgenic mouse platforms for next-generation monoclonal antibody discovery and antibody CMC.

Highlights of 2019 Protein Engineering Summit (PEGS) in Boston, USA: Advancing Antibody-Based Cancer Therapies to the Clinic

The 15^th Annual Protein Engineering Summit (PEGS) organized by Cambridge Healthtech Institute was held in Boston, USA, from 8 to 12 April 2019. This report highlights the presentations in the Oncology Stream of this meeting with a focus on bispecific antibodies (BsAbs). A variety of BsAb formats with different target antigens (CD3, CTLA4, PD-1, PD-L1, EGFR, HER2, BCMA, CD19, CD20, CD38, CD123, TGFβ, PSMA, etc.) have been discussed, in which the T-cell engaging (anti-CD3) BsAb is the most studied construct to exhibit promising immunotherapeutic activities. The BsAb formats include IgG-like structures or antibody fragments composed of antigen-binding sites only. Preclinical and clinical data from different BsAbs demonstrated the potential therapeutic applications in various solid tumors and hematological malignancies. The ongoing development of BsAb formats will help overcome current clinical issues, such as tumor selectivity and antigen coverage. This report also covers several presentations about emerging targets (e.g. mesothelin, CD47) and new technologies in the field of antibody engineering and therapeutics.

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.

Natural Killer Cell Dysfunction in Hepatocellular Carcinoma: Pathogenesis and Clinical Implications

Hepatocellular carcinoma (HCC) is currently the third leading cause of malignancy-related mortalities worldwide. Natural killer (NK) cells are involved in the critical role of first line immunological defense against cancer development. Defects in NK cell functions are recognized as important mechanisms for immune evasion of tumor cells. NK cell function appears to be attenuated in HCC, and many previous reports suggested that NK cells play a critical role in controlling HCC, suggesting that boosting the activity of dysfunctional NK cells can enhance tumor cell killing. However, the detailed mechanisms of NK cell dysfunction in tumor microenvironment of HCC remain largely unknown. A better understanding of the mechanisms of NK cell dysfunction in HCC will help in the NK cell-mediated eradication of cancer cells and prolong patient survival. In this review, we describe the various mechanisms underlying human NK cell dysfunction in HCC. Further, we summarize current advances in the approaches to enhance endogenous NK cell function and in adoptive NK cell therapies, to cure this difficult-to-treat cancer.

Frontiers and Opportunities: Highlights of the 2nd Annual Conference of the Chinese Antibody Society

The Chinese Antibody Society (CAS) convened the second annual conference in Cambridge, MA, USA on 29 April 2018. More than 600 members from around the world attended the meeting. Invited speakers discussed the latest advancements in therapeutic antibodies with an emphasis on the progress made in China. The meeting covered a vast variety of topics including the current status of therapeutic antibodies, the progress of immuno-oncology, and biosimilars in China. The conference presentations also included the development of several novel antibodies such as antibodies related to weight loss, T-cell receptor-mimicking antibodies that target intracellular antigens, and tumor-targeting antibodies that utilize both innate and adaptive immune pathways. At the meeting, the CAS announced the launch of its official journal-Antibody Therapeutics-in collaboration with Oxford University Press. The conference was concluded by a panel discussion on how to bring a therapeutic drug developed in China to the USA for clinical trials.

Hepatocellular carcinoma: Prospects for natural killer cell immunotherapy

Liver disease is a growing cause of death in the United Kingdom and the incidence of hepatocellular carcinoma (HCC) is rising (http://www.cancerresearchuk.org/). The combination of an immunosuppressive environment within the liver and suboptimal host anti-tumour immune responses may account for the poor survival outcome of HCC. Understanding how tumours evade immune recognition coupled with new insights into the unique immunological environment within the liver will be critical to developing liver-specific immunotherapies.

Construction of an immunotoxin, HN3-mPE24, targeting glypican-3 for liver cancer therapy

Glypican-3 (GPC3) is overexpressed in hepatocellular carcinoma (HCC). We constructed a recombinant immunotoxin, HN3-mPE24, which contains a truncated form of Pseudomonas exotoxin A. The toxin portion lacks most of domain II and has seven point mutations in domain III to remove the B-cell epitopes thought to be responsible for causing off-target side effects and immunogenicity. We also fused a bivalent HN3 to mPE24. We tested these two molecules for GPC3 binding and cytotoxicity in HCC cell models. The K_D values of HN3-mPE24 and HN3-HN3-mPE24 for GPC3-expressing tumor cells were 12 nM and 1.4 nM, respectively. The IC₅₀ values of HN3-mPE24 and HN3-HN3-mPE24 for HCC cells were 0.2 nM and 0.4 nM, respectively. We also evaluated their toxicity and anti-tumor efficacy in mice. The maximum tolerated doses of HN3-mPE24 and HN3-HN3-mPE24 were 7 mg kg⁻¹ and 3.6 mg kg⁻¹, respectively. We treated mice with 5 mg kg⁻¹ of HN3-mPE24 intravenously every other day for ten injections. The alpha-fetoprotein level of HN3-mPE24 treated group was approximately 700 fold less than that of the untreated group (1.1 μg ml⁻¹ vs. 692.1 μg ml⁻¹). In addition, 25% of the mice treated with HN3-mPE24 survived to the end of this study, which was 105 days after HCC tumor implantation. In conclusion, the HN3-mPE24 immunotoxin caused liver tumor regressions and extended survival with no significant side effects in mice. It is a promising candidate for the treatment of liver cancer that may be readily translated to humans.

Role of Glypican-3 in the growth, migration and invasion of primary hepatocytes isolated from patients with hepatocellular carcinoma

BACKGROUND

Recently, Glypican-3 (GPC3) has been identified as a potential hepatocellular carcinoma (HCC) diagnostic and/or therapeutic target. GPC3 has been found to be up-regulated in HCC and to be absent in normal and cirrhotic liver. As yet, however, the molecular characteristics of GPC3 and its role in HCC cell physiology and development are still undefined.

METHODS

Human hepatocyte cultures were established from 10 HCC patients. Additional liver samples were obtained from 5 patients without cirrhosis and/or HCC. Soft agar colony formation, (co-)immunofluorescence and Western blot assays were used to characterize the hapatocyte cultures. The expression of GPC3 in the hepatocytes was silenced using siRNA, after which, apoptosis, scratch wound migration and transwell invasion assays were performed.

RESULTS

We found that in HCC precursor hepatocytes GPC3 is increasingly expressed in different forms and at different locations, i.e., a non-cleaved form (70 kDa) was found to be localized in the cytoplasm while a N-terminal cleaved form (N-GPC3: 40 kDa) was fond to be localized in the cytoplasm and at the extracellular side of hepatocyte membranes. In addition, we found that the non-cleaved form of GPC3 co-localizes with Furin-Convertase in the Golgi apparatus. We also found that, similar to GPC3, Furin-Convertase is expressed in HCC precursor cells, suggesting a role in GPC3 processing. Subsequent siRNA-mediated GPC3 silencing resulted in a temporary inhibition of cell proliferation, migration and ivasion, while inducing apoptosis in transformed hepatocytes.

CONCLUSION

Our data reveal new aspects of the role of GPC3 in early hepatocyte transformation. In addition we conclude that GPC3 may serve as a new HCC immune-therapeutic target.

Hep88 mAb-mediated paraptosis-like apoptosis in HepG2 cells via downstream upregulation and activation of caspase-3, caspase-8 and caspase-9

Hepatocellular carcinoma (HCC) is a leading cause of cancer death worldwide. Presently, targeted therapy via monoclonal antibodies to specific tumor-associated antigens is being continuously developed. Hep88 mAb has proven to exert tumoricidal effects on the HepG2 cell via a paraptosis-like morphology. To verify the pathway, we then demonstrated downstream up-regulation of caspase-3, caspase-8 and caspase-9, assessingmRNA expression by real-time PCR and associated enzyme activity by colorimetric assay. Active caspase-3 determination was also accomplished by flow cytometry. Active caspase-3 expression was increased by Hep88 mAb treatment in a dose-and time-dependent manner. All of the results indicated that Hep88 mAb induced programmed cell death in the HepG2 cell line from paraptosis-like to apoptosis by downstream induction of caspases. These conclusions imply that Hep88mAb might be a promising tool for the effective treatment of HCC in the future.

Carbohydrate-based materials for targeted delivery of drugs and genes to the liver

The insult to liver by toxic materials leads to cirrhosis, hepatitis and cancer. Upon administration, drugs accumulate in liver, which is systemically cleared by reticuloendothelial system. However, specific targeting of drugs to liver is a serious challenge. Specific delivery of molecules to hepatocytes is accomplished by targeting cell surface lectins, asialoglycoprotein receptors. Asialofetuin, N-acetyl glucosamine and galactose are high-affinity ligands of asialoglycoprotein receptors. The bioconjugation of drugs, fluorescent molecules and gene delivery vectors with lectin-targeting agents, and their delivery in liver hepatocytes, is discussed. Mannose and N-acetyl glucosamine conjugates are evaluated for their delivery to hepatic stellate and kupffer cells. The glycosylated gene and drug delivery vectors in clinical trials are outlined.

Effect of taurine on the proliferation and apoptosis of human hepatocellular carcinoma HepG2 cells

The aim of the present study was to observe the effect and molecular mechanism of taurine (Tau) on the cell proliferation and apoptosis of human hepatocellular carcinoma (HHCC) HepG2 cells. HHCC HepG2 cells were used as target cells, and the cell survival rate was assessed using a multi-time-step method. The p53 upregulated modulator of apoptosis (PUMA) gene was transiently transfected by lipofection and subsequently silenced with specific small interfering (si)RNA. The cell apoptosis rate was detected by flow cytometry, and protein expression levels were analyzed with western blotting. Addition of 20-160 mM Tau was shown to have a significant inhibitory effect on cell proliferation, while promoting the induction of HHCC HepG2 cell apoptosis (P<0.05). Transfection of the PUMA gene significantly enhanced the ability of Tau to inhibit proliferation and induce apoptosis of HepG2 cells. In addition, transfection of the PUMA gene increased the protein expression of B-cell lymphoma-2-associated X and reduced the expression of B-cell lymphoma-2 (P<0.05). Silencing the PUMA gene with specific siRNA was demonstrated to significantly reduce the ability of Tau to inhibit proliferation and induce the apoptosis of HHCC HepG2 cells (P<0.01). Therefore, the PUMA gene was shown to have an important role in mechanism underlying the effect that Tau exerts on cell proliferation and apoptosis in HHCC HepG2 cells.

Immunotoxin targeting glypican-3 regresses liver cancer via dual inhibition of Wnt signalling and protein synthesis

Glypican-3 is a cell surface glycoprotein that associates with Wnt in liver cancer. We develop two antibodies targeting glypican-3, HN3 and YP7. The first antibody recognizes a functional epitope and inhibits Wnt signalling, whereas the second antibody recognizes a C-terminal epitope but does not inhibit Wnt signalling. Both are fused to a fragment of Pseudomonas exotoxin A (PE38) to create immunotoxins. Interestingly, the immunotoxin based on HN3 (HN3-PE38) has superior antitumor activity as compared with YP7 (YP7-PE38) both in vitro and in vivo. Intravenous administration of HN3-PE38 alone, or in combination with chemotherapy, induces regression of Hep3B and HepG2 liver tumour xenografts in mice. This study establishes glypican-3 as a promising candidate for immunotoxin-based liver cancer therapy. Our results demonstrate immunotoxin-induced tumour regression via dual mechanisms: inactivation of cancer signalling via the antibody and inhibition of protein synthesis via the toxin.

Evaluation of antiglypican-3 therapy as a promising target for amelioration of hepatic tissue damage in hepatocellular carcinoma

In Egypt, hepatocellular carcinoma (HCC) was predicted to continue to rise over the next few decades causing a national problem. Meanwhile, glypican-3 (GPC3), a highly expressed glypican, has emerged as a potential target for HCC immunotherapy. Therefore, we aimed to identify the impact of blocking GPC3 on liver damage in HCC as well as a possible mechanism. Fifty four HCC patients, 20 cirrhotic patients and 10 healthy subjects were recruited. Serum levels of GPC3, sulfatase-2 (SULF-2), heparan sulfate proteoglycan (HSPG), insulin-like growth factor-II (IGF-II) were measured by ELISA. In parallel, HCC was induced in 40 male Sprague-Dawley rats in presence/absence of antiGPC-3. Liver impairment was detected by investigating liver sections stained with hematoxylin/eosin and serum α-fetoprotein (AFP). Liver homogenates of GPC3, SULF-2, and HSPG were measured by ELISA. Gene expression of caspase-3 and IGF-II were assayed by RT-PCR. HCC patients showed significant elevated serum levels of GPC3, IGF-II and SULF-2 accompanied by decreased HSPG. However, treatment of HCC rats with antiGPC-3 significantly reduced serum AFP and showed nearly normal hepatocytes. In addition, antiGPC-3 significantly reduced elevated liver homogenates protein levels of GPC3 and SULF-2 and gene expression of IGF-II and caspase-3. antiGPC-3 restored the reduced hepatic HSPG. antiGPC-3 showed anti-tumor activity as well as hepatoprotective effects. antiGPC-3-chemoprotective effect can be explained by forced reduction of IGF-II expression, restoration of HSPGs, deactivation of SULF-2 and reduction of gene expression of caspase-3. Targeting GPC3 is a promising therapeutic approach for HCC.

Hep88 mAb-initiated paraptosis-like PCD pathway in hepatocellular carcinoma cell line through the binding of mortalin (HSPA9) and alpha-enolase

Background

Hepatocellular carcinoma (HCC) is the most prevalent hepatic cancer worldwide. Currently, a targeted therapy via monoclonal antibodies (mAbs) specific to tumor-associated antigen is undergoing continual development in HCC treatment.

Methods

In this regard, after establishing and consequently exploring Hep88 mAb’s tumoricidal effect on hepatocellular carcinoma cell line (HepG2 cell line), the Hep88 mAb’s specific antigens from both membrane and cytoplasmic fractions of HepG2 cell line were identified by 2-D gel electrophoresis and western blot analysis. After in-gel digestion and subsequent analysis by liquid chromatography-mass spectrometry (LC-MS), mortalin (HSPA9) and alpha-enolase were identified. The recombinant proteins specific to Hep88 mAb were cloned and expressed in E. coli BL21(DE3). Moreover, alteration of HepG2 and Chang liver cell line after being induced by Hep88 mAb for 1–3 days was investigated using a transmission electron microscope.

Results

The result demonstrated that Hep88 mAb can bind to the recombinant mortalin (HSPA9) and alpha-enolase. In addition, the gradual appearing of mitochondria vacuolization and endoplasmic reticulum dilatation were observed. Those characteristics might be explained by the paraptosis-like program cell death (PCD), which is induced by the binding of Hep88 mAb to mortalin (HSPA9). Mortalin depletion resulting from the formation of Hep88 mAb-mortalin (HSPA9) complex might initiate transcription-independence of p53-mediated apoptosis. Additionally, Hep88mAb-alpha-enolase complex might initiate HepG2 cells energy exhaustion by glycolysis pathway obstruction.

Conclusion

These fascinating results imply that Hep88 mAb might be a promising tool for the development of an effective treatment of HCC in the next decade.

Integrated analysis of mutation data from various sources identifies key genes and signaling pathways in hepatocellular carcinoma

BACKGROUND

Recently, a number of studies have performed genome or exome sequencing of hepatocellular carcinoma (HCC) and identified hundreds or even thousands of mutations in protein-coding genes. However, these studies have only focused on a limited number of candidate genes, and many important mutation resources remain to be explored.

PRINCIPAL FINDINGS

In this study, we integrated mutation data obtained from various sources and performed pathway and network analysis. We identified 113 pathways that were significantly mutated in HCC samples and found that the mutated genes included in these pathways contained high percentages of known cancer genes, and damaging genes and also demonstrated high conservation scores, indicating their important roles in liver tumorigenesis. Five classes of pathways that were mutated most frequently included (a) proliferation and apoptosis related pathways, (b) tumor microenvironment related pathways, (c) neural signaling related pathways, (d) metabolic related pathways, and (e) circadian related pathways. Network analysis further revealed that the mutated genes with the highest betweenness coefficients, such as the well-known cancer genes TP53, CTNNB1 and recently identified novel mutated genes GNAL and the ADCY family, may play key roles in these significantly mutated pathways. Finally, we highlight several key genes (e.g., RPS6KA3 and PCLO) and pathways (e.g., axon guidance) in which the mutations were associated with clinical features.

CONCLUSIONS

Our workflow illustrates the increased statistical power of integrating multiple studies of the same subject, which can provide biological insights that would otherwise be masked under individual sample sets. This type of bioinformatics approach is consistent with the necessity of making the best use of the ever increasing data provided in valuable databases, such as TCGA, to enhance the speed of deciphering human cancers.

Expression and diagnostic values of calretinin and CK5/6 in cholangiocarcinoma

BACKGROUND

Mesothelin, a mesothelial marker, has been found expressed in and as a potential treatment target of cholangioacarcinoma (CC). It is possible that CC may be derived from the cells sharing mesothelial markers. However, the expression of other mesothelial markers in CC is largely unknown.

METHODS

Thirty CC cases (10 extrahepatic and 20 intrahepatic) were retrieved from our institutional archive. The immunohistochemical study of Calretinin (DC8), WT1 (6F-H2), Lymphatic Endothelial Marker (D2-40), CK5/6 (D5/16 B4) and CK19 (b170) was done on formalin fixed paraffin embedded sections for 2-3 blocks of each case. We compared the expression levels between CC and normal bile duct (NBD) on the same block.

RESULTS

All of the CC and NBD are positive for CK19 (23/23) and negative for WT1 (0/23) and D2-40 (0/23), except one CC positive for D2-40(1/30, 3.3%) and one NBD positive for WT1 (1/23, 4.3%). Calretinin immunoreactivity was detected in 52.2% (12/23) of CC, but none in NBD (0/23). CK5/6 was also detectable in 73.3% (22/30) of CC and all NBD (30/30). Increased expression of calretinin and reduced expression of CK5/6 were more likely associated with CC than NBD (P < 0.001 and P = 0.002, respectively). The sequential staining pattern of positive calretinin and negative CK5/6 in calretinin negative cases has a sensitivity of 69.57% and a specificity of 100% for differentiating CC from NBD. CK5/6 expression was also more likely associated with well-differentiated CC (7/7 versus 12/20 in moderately differentiated, and 9/10 in poorly differentiated, P = 0.019) and extrahepatic CC (10/10 versus 12/20 in intrahepatic, P = 0.029), but there was no association between the calretinin expression and the CC grade or location.

CONCLUSION

Calretinin and CK5/6 immunohistochemical stains may be useful for diagnosing a CC. Their immunohistochemical results should be interpreted with caution in the cases with differential diagnoses of mesothelioma and CC. A full mesothelioma panel, including WT1 and/or D2-40, is recommended to better define a mesothelial lineage. The biology of calretinin and CK5/6 expression in CC is unclear, but might shed light on identifying therapeutic targets for CC.

Suramin inhibits hepatic tissue damage in hepatocellular carcinoma through deactivation of heparanase enzyme

Hepatocellular carcinoma (HCC) is resistant to conventional chemotherapy, and is rarely amenable to radiotherapy. Heparanase, enzyme attacks heparan sulfate proteoglycans (HSPGs), is preferentially expressed in human tumors and its overexpression in low-metastatic tumor confers a highly invasive phenotype in experimental animals. Meanwhile, high doses of suramin dramatically increase tissue glycosaminoglycans due, in part, to inhibition of heparanase enzymes. Therefore, the following study was conducted to evaluate the chemopreventive and hepatoprotective effects of suramin in in-vivo model of HCC. Therefore, HCC was induced in SD rats by thioacetamide (200mg/kg) in presence/absence of suramin (20mg/kg). Liver impairment was assessed by measuring serum α-fetoprotein and investigating liver sections stained with Hematoxylin/Eosin. Hepatic HSPGs and heparanse were measured by ELISA. Glucosamine and glucuronic acid were measured by chemical methods. Gene expression of fibroblast growth factor (FGF)-2 and caspase-3 was measured. Apoptotic pathway was evaluated by measuring the activity of caspase-3/8/9. Suramin increased the animal survival and decreased serum α-fetoprotein. In addition, suramin ameliorated fibrosis and massive hepatic tissue breakdown. Suramin restored hepatic HSPGs and reduced the activity of hepatic heparanase leading to decreased hepatic levels of glucosamine and glucuronic acid. Moreover, suramin reduced the gene expression of FGF-2 and caspase-3. Finally, suramin blocked the elevated activity of caspase-3/8/9. In conclusion, surmain showed antitumor activity as well as hepatoprotective effects. Besides its antioxidant activity, other mechanisms are involved including restoration of HSPGs and inhibition of heparanase and FGF-2. Suramin inhibits intrinsic and extrinsic apoptotic pathway. Targeting HSPGs expression is potential therapeutic target for HCC.

The glypican 3 hepatocellular carcinoma marker regulates human hepatic stellate cells via Hedgehog signaling

BACKGROUND

Hepatocellular carcinoma (HCC) frequently represents two diseases as it often arises in the setting of cirrhosis caused by the proliferation and activation of hepatic stellate cells (HSCs). Previously, we identified that Hedgehog (Hh) signaling regulates HSC viability and fibrinogenesis, as well as HCC tumorigenesis. Although it is increasingly recognized that HSCs and HCCs communicate via paracrine signaling, Hh's role in this process is just emerging. We hypothesized that a secreted HCC tumor marker and Hh mediator, glypican 3 (GPC3), may regulate HSC.

METHODS

Using three human HCC lines (Hep3B, PLC/PRF/5 and SK-Hep-1) and one Hh-responsive human HSC line (LX-2), we developed two in vitro models of HCC-to-HSC paracrine signaling using a Transwell coculture system and HCC-conditioned media. We then evaluated the effects of these models, as well as GPC3, on HSC viability and gene expression.

RESULTS

Using our coculture and conditioned media models, we demonstrate that the three HCC lines decrease HSC viability. Furthermore, we demonstrate that recombinant GPC3 dose-dependently decreases the LX-2 viability while inhibiting the expression of Hh target genes that regulate HSC viability. Finally, GPC3's inhibitory effects on cell viability and Hh target gene expression are partially abrogated by heparin, a competitor for GPC3 binding.

CONCLUSIONS

For the first time, we show that GPC3, an HCC biomarker and Hh mediator, regulates human HSC viability by regulating Hh signaling. This expands on existing data suggesting a role for tumor-stroma interactions in the liver and suggests that GPC3 plays a role in this process.

Mass spectrometric identification of glycosylphosphatidylinositol-anchored peptides

Glycosylphosphatidylinositol (GPI) anchoring is a post-translational modification widely observed among eukaryotic membrane proteins. GPI anchors are attached to proteins via the carboxy-terminus in the outer leaflet of the cell membrane, where GPI-anchored proteins (GPI-APs) perform important functions as coreceptors and enzymes. Precursors of GPI-APs (Pre-GPI-APs) contain a C-terminal hydrophobic sequence that is involved in cleavage of the signal sequence from the protein and addition of the GPI anchor by the transamidase complex. In order to confirm that a given protein contains a GPI anchor, it is essential to identify the C-terminal peptide containing the GPI-anchor modification site (ω-site). Previously, efficient identification of GPI-anchored C-terminal peptides by mass spectrometry has been difficult, in part because of complex structure of the GPI-anchor moiety. We developed a method to experimentally identify GPI-APs and their ω-sites. In this method, a part of GPI-anchor moieties are removed from GPI-anchored peptides using phosphatidylinositol-specific phospholipase C (PI-PLC) and aqueous hydrogen fluoride (HF), and peptide sequence is then determined by mass spectrometry. Using this method, we successfully identified 10 GPI-APs and 12 ω-sites in the cultured ovarian adenocarcinoma cells, demonstrating that this method is useful for identifying efficiently GPI-APs.

A human single-domain antibody elicits potent antitumor activity by targeting an epitope in mesothelin close to the cancer cell surface

Monoclonal antibodies against mesothelin are being evaluated for the treatment of mesothelioma and multiple forms of cancers, and show great promise for clinical development for solid cancers. Antibodies against mesothelin have been shown to act via immunotoxin-based inhibition of tumor growth and induction of antibody-dependent cell-mediated cytotoxicity (ADCC). However, complement-dependent cytotoxicity (CDC), considered an important additional mechanism of therapeutic antibodies against tumors, is inactive for such antibodies. Here, we used phage display antibody engineering technology and synthetic peptide screening to identify SD1, a human single-domain antibody to mesothelin. SD1 recognizes a conformational epitope at the C-terminal end (residues 539-588) of mesothelin close to the cell surface. To investigate SD1 as a potential therapeutic agent, we generated a recombinant human Fc (SD1-hFc) fusion protein. Interestingly, the SD1-hFc protein exhibits strong CDC activity, in addition to ADCC, against mesothelin-expressing tumor cells. Furthermore, it causes growth inhibition of human tumor xenografts in nude mice as a single agent. SD1 is the first human single-domain antibody targeting mesothelin-expressing tumors, shows potential as a cancer therapeutic candidate, and may improve current antibody therapy targeting mesothelin-expressing tumors.

p53 codon 72 polymorphism and hepatocellular carcinoma: a meta-analysis

BACKGROUND

Hepatocellular carcinoma (HCC) is one of the most common malignant neoplasms worldwide. The p53 gene is frequently mutated in some histological subtypes of HCC. The role of p53 mutations and polymorphic variant of codon 72 in the prognosis of disease is still unclear. The p53 tumor suppressor gene Arg72Pro polymorphism has been associated with HCC. However, results were inconsistent. This meta-analysis was performed to estimate the association between p53 Arg72Pro polymorphism and HCC or HCC infected by HBV/HCV.

METHODS

Electronic search of PubMed was conducted to select studies. Studies containing available genotype frequencies of Arg72Pro were chosen, and pooled odds ratio (OR) with 95 % confidence interval (CI) was used to assess the association.

RESULTS

Ten published studies, including 1,371 HCC cases and 2,517 controls were identified. The overall results suggested that the variant genotypes were associated with the HCC risk (Pro/Pro vs. Pro/Arg + Arg/Arg: OR 1.355, 95 % CI 1.041-1.764, p = 0.024). In the stratified analysis, individuals with the Pro/Pro in the recessive model had increased risk of HCC (OR 1.927, 95 % CI 1.127-3.297, p = 0.017) in Caucasian. A symmetric funnel plot, the Begg's test, was suggestive of the lack of publication bias. There was no association between the p53 codon 72 polymorphism and HBV/HCV-positive HCC.

CONCLUSION

This meta-analysis suggests that p53 condon 72 Pro/Progenotypes are associated with increased risk of HCC in Caucasian. To validate this association, further studies with larger participants worldwide are needed to examine the associations between this polymorphism and HCC.

Clinical significance of circulating sICAM-1 and GPC-3 mRNA expression in the diagnosis and prognostic evaluation of hepatocellular carcinoma

AIM: To quantitatively detect the levels of circulating soluble intercellular adhesion molecule-1 (sICAM-1) and glypican-3 (GPC-3) mRNA expression in peripheral blood mononuclear cells (PBMCs) in patients with liver diseases for exploring their significance in the diagnosis and prognostic evaluation for hepatocellular carcinoma (HCC).

METHODS: Total RNA was extracted from circulating PBMCs collected from patients with liver diseases. GPC-3 cDNA was synthetized by reverse transcription and amplified by fluorescent quantitative PCR. The levels of circulating ICAM-1 were quantitatively detected by enzyme-linked immunosorbent assay.

RESULTS: The levels of sICAM-1 were increasing during the development of liver diseases, significantly higher in HCC patients than in those with liver cirrhosis (t = 3.184, P = 0.002) or chronic hepatitis (t = 3.962, P < 0.001). sICAM-1 levels were significantly associated with periportal cancerous embolus (t = 2.941, P = 0.005) and extrahepatic metastasis (t = 3.282, P = 0.002), but not with patients' age, sex, AFP level, HBsAg positivity, or tumor size. The positive expression of GPC-3 mRNA in PBMCs was found only in HCC patients (70.9%, 39 of 55), and not in patients with liver cirrhosis, chronic hepatitis, metastatic liver cancer, non-liver tumors, or normal controls (χ² = 26.773, P < 0.001). The expression of GPC-3mRNA in PBMCs was associated with HBV infection (χ² = 14.601, P < 0.001), TNM stage (χ² = 17.732, P < 0.001), periportal cancerous embolus, and extrahepatic metastasis (χ² = 22.271, P < 0.001), and not with tumor size, tumor number, AFP level or differentiation degree. Combined detection of GPC-3 mRNA and serum AFP level could improve the detection rate of HCC.

CONCLUSION: Detection of circulating sICAM-1 and GPC-3 mRNA in PBMCs could be used for the diagnosis and metastasis monitoring of HCC, especially in AFP-negative patients with HCC.

High-affinity monoclonal antibodies to cell surface tumor antigen glypican-3 generated through a combination of peptide immunization and flow cytometry screening

Isolating high-affinity antibodies against native tumor antigens on the cell surface is not straightforward using standard hybridoma procedures. Here, we describe a combination method of synthetic peptide immunization and high-throughput flow cytometry screening to efficiently isolate hybridomas for cell binding. Using this method, we identified high-affinity monoclonal antibodies specific for the native form of glypcian-3 (GPC3), a target heterogeneously expressed in hepatocellular carcinoma (HCC) and other cancers. We isolated a panel of monoclonal antibodies (YP6, YP7, YP8, YP9 and YP9.1) for cell surface binding. The antibodies were used to characterize GPC3 protein expression in human liver cancer cell lines and tissues by flow cytometry, immunoblotting and immunohistochemistry. The best antibody (YP7) bound cell surface-associated GPC3 with equilibrium dissociation constant, KD = 0.3 nmol/L and was highly specific for HCC, not normal tissues or other forms of primary liver cancers (such as cholangiocarcinoma). Interestingly, the new antibody was highly sensitive in that it detected GPC3 in low expression ovarian clear cell carcinoma and melanoma cells. The YP7 antibody exhibited significant HCC xenograft tumor growth inhibition in nude mice. These results describe an improved method for producing high-affinity monoclonal antibodies to cell surface tumor antigens and represent a general approach to isolate therapeutic antibodies against cancer. The new high-affinity antibodies described here have significant potential for GPC3-expressing cancer diagnostics and therapy.