Generation of a humanized anti-glypican 3 antibody by CDR grafting and stability optimization. Anticancer Drugs. 2010;21:907-916. [PMID: 20847643 DOI: 10.1097/cad.0b013e32833f5d68]

Immunotherapy and liver transplantation for hepatocellular carcinoma: Current and future challenges

Despite existing curative options like surgical removal, tissue destruction techniques, and liver transplantation for early-stage hepatocellular carcinoma (HCC), the rising incidence and mortality rates of this global health burden necessitate continuous exploration of novel therapeutic strategies. This review critically assesses the dynamic treatment panorama for HCC, focusing specifically on the burgeoning role of immunotherapy in two key contexts: early-stage HCC and downstaging advanced HCC to facilitate liver transplant candidacy. It delves into the unique immunobiology of the liver and HCC, highlighting tumor-mediated immune evasion mechanisms. Analyzing the diverse immunotherapeutic approaches including checkpoint inhibitors, cytokine modulators, vaccines, oncolytic viruses, antigen-targeting antibodies, and adoptive cell therapy, this review acknowledges the limitations of current diagnostic markers alpha-fetoprotein and glypican-3 and emphasizes the need for novel biomarkers for patient selection and treatment monitoring. Exploring the rationale for neoadjuvant and adjuvant immunotherapy in early-stage HCC, current research is actively exploring the safety and effectiveness of diverse immunotherapeutic approaches through ongoing clinical trials. The review further explores the potential benefits and challenges of combining immunotherapy and liver transplant, highlighting the need for careful patient selection, meticulous monitoring, and novel strategies to mitigate post-transplant complications. Finally, this review delves into the latest findings from the clinical research landscape and future directions in HCC management, paving the way for optimizing treatment strategies and improving long-term survival rates for patients with this challenging malignancy.

Engineered E. coli OMVs Carrying the Membrane-Binding hGC33 Fragment Precisely Target Liver Cancer and Effectively Treat Tumor

Background

Glypican-3 (GPC3), which is a membrane-associated antigen that is overexpressed in hepatocellular carcinoma (HCC). hGC33, a humanized anti-GPC3 antibody, has been validated as a potential antibody drug with good antitumor activity by preclinical studies and the Phase II clinical trial. However, free drug usually lack good tumor penetration. Outer membrane vesicles (OMVs) that are secreted by Escherichia coli function as natural vectors for molecule delivery and mediators of biological signals across tissues. Our study aimed to engineer E. coli for use as a platform to precisely deliver the hGC33 single-chain variable fragment (hGC33-scFv) for the targeted treatment of HCC.

Methods

In this study, we utilized E. coli BL21(DE3) to express Hbp-hGC33-scFv fusion protein and generated E. coli hGC33-OMVs. After isolation and characterization, we assessed their chemotaxis toward HepG2  cells by Transwell, coimmunoprecipitation (co-IP) to confirm hGC33-GPC3 binding, and immunofluorescence (IF) to evaluate the localization of hGC33 on OMV membranes. The in vivo efficacy was assessed in BALB/c nude mice harboring HepG2  cell-derived xenografts, and tumor targeting was analyzed with Cy7-labeled OMVs and live imaging. Proliferation assays, cell cycle analysis, and Wnt pathway expression analysis were performed to elucidate the underlying mechanisms.

Results

hGC33-OMVs exhibited spherical bilayered nanostructures and displayed hGC33-scFv on their surface. hGC33-OMVs preferentially accumulated in tumors, significantly reducing tumor volume compared with controls and downregulating the proliferation markers Ki67 and PCNA. Transwell assays revealed increased tropism of hGC33-OMVs toward HepG2 cells, while Co-IP confirmed the direct interaction between hGC33 and GPC3. Meanwhile, hGC33-OMVs suppressed HepG2 cell proliferation, induced G1-phase arrest, and reduced Wnt3a, β-catenin, Cyclin D1, and C-myc expression.

Conclusion

Engineered E. coli hGC33-OMVs effectively target HCC via the hGC33-GPC3 interaction, inhibit tumor growth by suppressing Wnt signaling, and demonstrate potential for use as a versatile platform for antibody delivery.

Development of glypican-3-specific chimeric antigen receptor-modified natural killer cells and optimization as a therapy for hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a highly malignant tumor characterized by insidious onset and rapid progression, with limited treatment choices. One treatment modality, chimeric antigen receptor (CAR)-modified natural killer (NK) cell immunotherapy, has shown promise for various cancers. However, the treatment efficacy of CAR-NK cells for HCC remain inferior. In this study, we developed two glypican-3 (GPC3)-specific CAR-NK-92 cell lines (GPC3-CAR-NK) and explored their antitumor efficacy for the treatment of HCC. Significant levels of cytokine production and in vitro cytotoxicity were produced following co-culture of GPC3+ HCC cells with the developed GPC3-CAR-NK cells. GC33-G2D-NK cells with NK cell-specific signaling domains showed better activation and killing abilities than GC33-CD28-NK cells containing T-cell-specific signaling domains. Moreover, GC33-G2D-NK cells efficiently eliminated tumors in cell-derived xenograft and patient-derived xenograft mouse models. In an abdominal metastasis model, intraperitoneally delivered GC33-G2D-NK cells showed better antitumor ability than intravenously injected cells. Finally, the combination of microwave ablation (MWA) with GC33-G2D-NK cell administration showed greater CAR-NK infiltration and tumor regression in ablated tumors than monotherapy alone. These findings indicate that administration of GPC3-CAR-NK cells may be a potential strategy for the treatment of HCC, and regional delivery or their combination with MWA may optimize their efficacy against HCC and may have translational value.

A Pair of Fluorescent Probes Enabling Precise Diagnosis of Liver Cancer by Complementary Imaging

Hepatocellular carcinoma (HCC) is by far the predominant malignant liver cancer, with both high morbidity and mortality. Early diagnosis and surgical resections are imperative for improving the survival of HCC patients. However, limited by clinical diagnosis methods, it is difficult to accurately distinguish tumor tissue and its boundaries in the early stages of cancer. Herein, we report two fluorescent probes, cLG and hLR, for the detection of cancer and healthy cells, respectively, enabling the precise diagnosis of liver cancer by providing complementary imaging. These two fluorescent probes could selectively stain the target cells in the liver tissue imaging, which is confirmed by H&E and antibody staining. Moreover, for the first time, the cancerous area and healthy area are clearly identified by the cocktail of these two probes, suggesting its potential to be used in fluorescence-guided surgery. Finally, we identify transporter SLC27A2 as the gating target of cLG through a systematic transporter screen using a CRISPR activation library. SMPD1 was identified as the target of hLR through a thermal proteome profiling. Therefore, the development of these two highly specific probes offers complementary imaging and provides a unique diagnostic tool for cancer disease, even for fluorescence-guided surgery.

Glypican-3 deficiency in liver cancer upregulates MAPK/ERK pathway but decreases cell proliferation

Glypican-3 (GPC3) is overexpressed in hepatocellular carcinomas and hepatoblastomas and represents an important therapeutic target but the biologic importance of GPC3 in liver cancer is unclear. To date, there are limited data characterizing the biological implications of GPC3 knockout (KO) in liver cancers that intrinsically express this target. Here, we report on the development and characterization of GPC3-KO liver cancer cell lines and compare to them to parental lines. GPC3-KO variants were established in HepG2 and Hep3B liver cancer cell lines using a lentivirus-mediated CRISPR/Cas9 system. We assessed the effects of GPC3 deficiency on oncogenic properties in vitro and in murine xenograft models. Downstream cellular signaling pathway changes induced by GPC3 deficiency were examined by RNAseq and western blot. To confirm the usefulness of the models for GPC3-targeted drug development, we evaluated the target engagement of a GPC3-selective antibody, GC33, conjugated to the positron-emitting zirconium-89 (89Zr) in subcutaneous murine xenografts of wild type (WT) and KO liver cancer cell lines. Deletion of GPC3 significantly reduced liver cancer cell proliferation, migration, and invasion compared to the parental cell lines. Additionally, the tumor growth of GPC3-KO liver cancer xenografts was significantly slower compared with control xenografts. RNA sequencing analysis also showed GPC3-KO resulted in a reduction in the expression of genes associated with cell cycle regulation, invasion, and migration. Specifically, we observed the downregulation of components in the AKT/NFκB/WNT signaling pathways and of molecules related to cell cycle regulation with GPC3-KO. In contrast, pMAPK/ERK1/2 was upregulated, suggesting an adaptive compensatory response. KO lines demonstrated increased sensitivity to ERK (GDC09994), while AKT (MK2206) inhibition was more effective in WT lines. Using antibody-based positron emission tomography (immunoPET) imaging, we confirmed that 89Zr-GC33 accumulated exclusively in GPC3-expression xenografts but not in GPC3-KO xenografts with high tumor uptake and tumor-to-liver signal ratio. We show that GPC3-KO liver cancer cell lines exhibit decreased tumorigenicity and altered signaling pathways, including upregulated pMAPK/ERK1/2, compared to parental lines. Furthermore, we successfully distinguished between GPC3+ and GPC3- tumors using the GPC3-targeted immunoPET imaging agent, demonstrating the potential utility of these cell lines in facilitating GPC3-selective drug development.

The TOPK Inhibitor HI-TOPK-032 Enhances CAR T-cell Therapy of Hepatocellular Carcinoma by Upregulating Memory T Cells

Chimeric antigen receptor (CAR) T cells are emerging as an effective antitumoral therapy. However, their therapeutic effects on solid tumors are limited because of their short survival time and the immunosuppressive tumor microenvironment. Memory T cells respond more vigorously and persist longer than their naïve/effector counterparts. Therefore, promoting CAR T-cell development into memory T cells could further enhance their antitumoral effects. HI-TOPK-032 is a T-LAK cell-originated protein kinase (TOPK)-specific inhibitor that moderately represses some types of tumors. However, it is unknown whether HI-TOPK-032 works on hepatocellular carcinoma (HCC) and whether it impacts antitumoral immunity. Using both subcutaneous and orthotopic xenograft tumor models of two human HCC cell lines, Huh-7 and HepG2, we found that HI-TOPK-032 significantly improved proliferation/persistence of CD8+ CAR T cells, as evidenced by an increase in CAR T-cell counts or frequency of Ki-67+CD8+ cells and a decrease in PD-1+LAG-3+TIM-3+CD8+ CAR T cells in vivo. Although HI-TOPK-032 did not significantly suppress HCC growth, it enhanced the capacity of CAR T cells to inhibit tumor growth. Moreover, HI-TOPK-032 augmented central memory CD8+ T cell (TCM) frequency while increasing eomesodermin expression in CD8+ CAR T cells in tumor-bearing mice. Moreover, it augmented CD8+ CAR TCM cells in vitro and reduced their expression of immune checkpoint molecules. Finally, HI-TOPK-032 inhibited mTOR activation in CAR T cells in vitro and in tumors, whereas overactivation of mTOR reversed the effects of HI-TOPK-032 on CD8+ TCM cells and tumor growth. Thus, our studies have revealed mechanisms underlying the antitumoral effects of HI-TOPK-032 while advancing CAR T-cell immunotherapy.

SCD1 inhibition enhances the effector functions of CD8+ T cells via ACAT1-dependent reduction of esterified cholesterol

We previously reported that the inhibition of stearoyl-CoA desaturase 1 (SCD1) enhances the antitumor function of CD8+ T cells indirectly via restoring production of DC recruiting chemokines by cancer cells and subsequent induction of antitumor CD8+ T cells. In this study, we investigated the molecular mechanism of direct enhancing effects of SCD1 inhibitors on CD8+ T cells. In vitro treatment of CD8+ T cells with SCD1 inhibitors enhanced IFN-γ production and cytotoxic activity of T cells along with decreased oleic acid and esterified cholesterol, which is generated by cholesterol esterase, acetyl-CoA acetyltransferase 1 (ACAT1), in CD8+ T cells. The addition of oleic acid or cholesteryl oleate reversed the enhanced functions of CD8+ T cells treated with SCD1 inhibitors. Systemic administration of SCD1 inhibitor to MCA205 tumor-bearing mice enhanced IFN-γ production of tumor-infiltrating CD8+ T cells, in which oleic acid and esterified cholesterol, but not cholesterol, were decreased. These results indicated that SCD1 suppressed effector functions of CD8+ T cells through the increased esterified cholesterol in an ACAT1-dependent manner, and SCD1 inhibition enhanced T cell activity directly through decreased esterified cholesterol. Finally, SCD1 inhibitors or ACAT1 inhibitors synergistically enhanced the antitumor effects of anti-PD-1 antibody therapy or CAR-T cell therapy in mouse tumor models. Therefore, the SCD1-ACAT1 axis is regulating effector functions of CD8+ T cells, and SCD1 inhibitors, and ACAT1 inhibitors are attractive drugs for cancer immunotherapy.

A New Combination: Anti Glypican-3 scFv and Diphtheria Toxin with the Best Flexible Linker

Along with all cancer treatments, including chemotherapy, radiotherapy, and surgery, targeting therapy is a new treatment manner. Immunotoxins are new recombinant structures that kill cancer cells by targeting specific antigens. Immunotoxins are composed of two parts: toxin moiety, which disrupts protein synthesis process, and antigen binding moiety that bind to antigens on the surface of cancer cells. Glypican 3 (GPC3) is an oncofetal antigen on the surface of Hepatocellular carcinoma (HCC) cells. In this study, truncated Diphtheria toxin (DT389) was fused to humanized scFv YP7 by one, two and three repeats of GGGGS linkers (DT389-(GGGGS)_1-3YP7). In-silico and experimental investigation were performed to find out how many repeats of linker between toxin and scFv moieties are sufficient. Results of in-silico investigations revealed that the difference in the number of linkers does not have a significant effect on the main structures of the immunotoxin; however, the three-dimensional structure of two repeats of linker had a more appropriate structure compared to others with one and three linker replications. In addition, with enhancing the number of linkers, the probability of protein solubility has increased. Generally, the bioinformatics results of DT389-(GGGGS)₂-YP7 structure showed that expression and folding is suitable; and YP7 scFv has appropriate orientation to bind GPC3. The experimental investigations indicated that the fusion protein was expressed as near to 50% soluble. Due to the high binding affinity of YP7 scFv and the proven potency of diphtheria in inhibiting protein synthesis, the proposed DT389-(GGGGS)₂-YP7 immunotoxin is expected to function well in inhibiting HCC.

Nanomedicine in Hepatocellular Carcinoma: A New Frontier in Targeted Cancer Treatment

Hepatocellular carcinoma (HCC) is the third leading cause of cancer-related death and is associated with a dismal median survival of 2-9 months. The fundamental limitations and ineffectiveness of current HCC treatments have led to the development of a vast range of nanotechnologies with the goal of improving the safety and efficacy of treatment for HCC. Although remarkable success has been achieved in nanomedicine research, there are unique considerations such as molecular heterogeneity and concomitant liver dysfunction that complicate the translation of nanotheranostics in HCC. This review highlights the progress, challenges, and targeting opportunities in HCC nanomedicine based on the growing literature in recent years.

Radiomics, Radiogenomics, and Next-Generation Molecular Imaging to Augment Diagnosis of Hepatocellular Carcinoma

Ultrasound, computed tomography, magnetic resonance imaging, and [F]F-fluorodeoxyglucose positron emission tomography are invaluable in the clinical evaluation of human cancers. Radiomics and radiogenomics tools may allow clinicians to standardize interpretation of these conventional imaging modalities, while better linking radiographic hallmarks to disease biology and prognosis. These advances, coupled with next-generation positron emission tomography imaging tracers capable of providing biologically relevant tumor information, may further expand the tools available in our armamentarium against human cancers. We present current imaging methods and explore emerging research that may improve diagnosis and monitoring of local, oligometastatic, and disseminated cancers exhibiting heterogeneous uptake of [F]F-fluorodeoxyglucose, using hepatocellular carcinoma as an example.

Recombinant immunotoxin targeting GPC3 is cytotoxic to H446 small cell lung cancer cells

Glypican-3 (GPC3) is a cell membrane glycoprotein that regulates cell growth and proliferation. Aberrant expression or distribution of GPC3 underlies developmental abnormalities and the development of solid tumours. The strongest evidence for the participation of GPC3 in carcinogenesis stems from studies on hepatocellular carcinoma and lung squamous cell carcinoma. To the best of our knowledge, the role of the GPC3 protein and its potential therapeutic application have never been studied in small cell lung carcinoma (SCLC), despite the known involvement of associated pathways and the high mortality caused by this disease. Therefore, the aim of the present study was to examine GPC3 targeting for SCLC immunotherapy. An immunotoxin carrying an anti-GPC3 antibody (hGC33) and Pseudomonas aeruginosa exotoxin A 38 (PE38) was generated. This hGC33-PE38 protein was overexpressed in E. coli and purified. ADP-ribosylation activity was tested in vitro against eukaryotic translation elongation factor 2. Cell internalisation ability was confirmed by confocal microscopy. Cytotoxicity was analysed by treating liver cancer (HepG2, SNU-398 and SNU-449) and lung cancer (NCI-H510A, NCI-H446, A549 and SK-MES1) cell lines with hGC33-PE38 and estimating viable cells number. A BrdU assay was employed to verify anti-proliferative activity of hGC33-PE38 on treated cells. Fluorescence-activated cell sorting was used for the detection of cell membrane-bound GPC3. The hGC33-PE38 immunotoxin displayed enzymatic activity comparable to native PE38. The protein was efficiently internalised by GPC3-positive cells. Moreover, hGC33-PE38 was cytotoxic to HepG2 cells but had no effect on known GPC3-negative cell lines. The H446 cells were sensitive to hGC33-PE38 (IC₅₀, 70.6±4.6 ng/ml), whereas H510A cells were resistant. Cell surface-bound GPC3 was abundant on the membranes of H446 cells, but absent on H510A. Altogether, the present findings suggested that GPC3 could be considered as a potential therapeutic target for SCLC immunotherapy.

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.

Glypican-3: A molecular marker for the detection and treatment of hepatocellular carcinoma☆

Hepatocellular carcinoma (HCC) is a malignant tumor with a fairly poor prognosis (5-year survival of less than 50%). Using sorafenib, the only food and drug administration (FDA)-approved drug, HCC cannot be effectively treated; it can only be controlled at most for a couple of months. There is a great need to develop efficacious treatment against this debilitating disease. Glypican-3 (GPC3), a member of the glypican family that attaches to the cell surface by a glycosylphosphatidylinositol anchor, is overexpressed in HCC cases and is elevated in the serum of a large proportion of patients with HCC. GPC3 expression contributes to HCC growth and metastasis. Furthermore, several different types of antibodies targeting GPC3 have been developed. The aim of this review is to summarize the current literatures on the GPC3 expression in human HCC, molecular mechanisms of GPC3 regulation and antibodies targeting GPC3.

Generation of fully human anti-GPC3 antibodies with high-affinity recognition of GPC3 positive tumors

The acceleration of therapeutic antibody development has been motivated by the benefit to and their demand for human health. In particular, humanized transgenic antibody discovery platforms, combined with immunization, hybridoma fusion and/or single cell DNA sequencing are the most reliable and rapid methods for mining the human monoclonal antibodies. Human GPC3 protein is an oncofetal antigen, and it is highly expressed in most hepatocellular carcinomas and some types of squamous cell carcinomas. Currently, no fully human anti-GPC3 therapeutic antibodies have been reported and evaluated in extensive tumor tissues. Here, we utilized a new humanized transgenic mouse antibody discovery platform (CAMouse) that contains large V(D)J -regions and human gamma-constant regions of human immunoglobulin in authentic configurations to generate fully human anti-GPC3 antibodies. Our experiments resulted in four anti-GPC3 antibodies with high-specific binding and cytotoxicity to GPC3 positive cancer cells, and the antibody affinities are in the nanomolar range. Immunohistochemistry analysis demonstrated that these antibodies can recognize GPC3 protein on many types of solid tumors. In summary, the human anti-human GPC3 monoclonal antibodies described here are leading candidates for further preclinical studies of cancer therapy, further, the CAMouse platform is a robust tool for human therapeutic antibody discovery.

DNAM1 and 2B4 Costimulatory Domains Enhance the Cytotoxicity of Anti-GPC3 Chimeric Antigen Receptor-Modified Natural Killer Cells Against Hepatocellular Cancer Cells in vitro

Purpose

Hepatocellular cancer (HCC) is the sixth most prevalent cancer and the third leading cause of cancer-related death worldwide. Cellular immunotherapy against glypican 3 (GPC3) has recently been used in the treatment of HCC, following the success of chimeric antigen receptor (CAR)-T therapy in treatment of B cell malignancy. However, CAR-T cells are not “off-the-shelf” and always cause cytokine release syndrome, which can be eliminated by using natural killer (NK) cells as effector cells. Since a costimulatory signal is necessary for the activation, persistence, or cytotoxicity of CAR-T cells, we speculated that the costimulatory signal is also required for CAR-NK cells in HCC treatment.

Methods

Five anti-GPC3 CAR plasmids containing different costimulatory domains were constructed. They included Z (only the CD3ζ domain, no costimulatory domain), CD28.Z (T-cell costimulatory domain CD28), DNAM1/2B4.Z (NK-cell-associated costimulatory domain DNAM1 or 2B4), and DNAM1.2B4.Z (both NK-cell-associated costimulatory domains). Respective CAR-NK-92 cells were generated. The MTT viability assay was performed to evaluate the effect of the different costimulatory domains on CAR-NK-cell proliferation. The effect on persistence was analyzed using an apoptosis assay and flow cytometry. Special cytotoxicity against normal hepatocellular cells and GPC3⁺ malignant cells was investigated in vitro. The concentration of cytokines (TNF-α and IFN-γ) released by CAR-NK-92 cells was also measured by ELISA.

Results

NK-cell-associated costimulatory signal was necessary for CAR-NK-92 cells. CAR-NK-92 cells with DNAM1 and/or 2B4 expanded more quickly and persisted with a lower apoptotic ratio, compared to the presence of CD28 or no costimulatory signal. All CAR-NK-92 cells showed special cellular cytotoxicity in vitro. CAR-NK-92 cells with NK-cell-associated costimulatory domains exhibited higher cytotoxic ability compared with those without any costimulatory domain or with T-cell costimulatory domain. CAR-NK-92 cells with both DNAM1 and 2B4 displayed the highest cytotoxicity. The cytokine release assay results were consistent with those of the cytotoxicity assay.

Conclusion

We provided the first evidence supporting a strategy using DNAM1 and 2B4 costimulatory domains to generate anti-GPC3 CAR-NK-92 cells, which exhibits enhanced cytotoxicity against hepatocellular cancer cells in vitro.

A method to induce hen egg lysozyme-specific humoral immune tolerance in mice by pre-exposition with the protein's oligomers

During treatment with protein therapeutics, such as monoclonal antibodies, the development of anti-drug antibodies is a serious side-effect of modern pharmacology. Anti-drug antibodies are produced as the number and exposure to therapeutic proteins increase. In this context, less immunogenic responses could diminish these noxious effects. Biophysical characterization of antigens, that is size, chemical composition, physical form, and degrability, are known to influence the outcome of immune responses. Here, using chemical modification, we have prepared oligomers of hen egg lysozyme (HEL), 3- to 5-mer, as a typical antigen in immunology and evaluated the efficacy as a tolerogen in HEL-specific antibody responses. Our results clearly demonstrated that pre-exposed the HEL-oligomers into mice effectively suppressed HEL-specific IgG responses regardless of the cross-linking mode. Therefore, the oligomerization is a method to induce tolerogenicity of proteins and may emerge as a promising strategy to control the production of undesirable anti-protein drug antibodies.

Engineering an anti-CD52 antibody for enhanced deamidation stability

Deamidation evaluation and mitigation is an important aspect of therapeutic antibody developability assessment. We investigated the structure and function of the Asn-Gly deamidation in a human anti-CD52 IgG1 antibody light chain complementarity-determining region 1, and risk mitigation through protein engineering. Antigen binding affinity was found to decrease about 400-fold when Asn³³ was replaced with an Asp residue to mimic the deamidation product, suggesting significant impacts on antibody function. Other variants made at Asn³³ (N33H, N33Q, N33H, N33R) were also found to result in significant loss of antigen binding affinity. The co-crystal structure of the antigen-binding fragment bound to a CD52 peptide mimetic was solved at 2.2Å (PDB code 6OBD), which revealed that Asn³³ directly interacts with the CD52 phosphate group via a hydrogen bond. Gly³⁴, but sits away from the binding interface, rendering it more amendable to mutagenesis without affecting affinity. Saturation mutants at Gly³⁴ were prepared and subjected to forced deamidation by incubation at elevated pH and temperature. Three mutants (G34R, G34K and G34Q) showed increased resistance to deamidation by LC-MS peptide mapping, while maintaining high binding affinity to CD52 antigen measured by Biacore. A complement -dependent cytotoxicity assay indicated that these mutants function by triggering antibody effector function. This study illustrates the importance of structure-based design and extensive mutagenesis to mitigate antibody developability issues.

Vesicular Antibodies: A Bioactive Multifunctional Combination Platform for Targeted Therapeutic Delivery and Cancer Immunotherapy

The ability to selectively kill cancerous cell populations while leaving healthy cells unaffected is a key goal in oncology. The use of nanovesicles (NVs) as chemotherapeutic delivery vehicles has been recently proven successful, yet monotherapy with monomodalities remains a significant limitation for solid tumor treatment. Here, as a proof of principle, a novel cell-membrane-derived NVs that can display full-length monoclonal antibodies (mAbs) is engineered. The high affinity and specificity of mAb for tumor-specific antigens allow these vesicular antibodies (VAs) to selectively deliver a cytotoxic agent to tumor cells and exert potent inhibition effects. These VAs can also regulate the tumor immune microenvironment. They can mediate antibody-dependent cellular cytotoxicity to eradicate tumor cells via recruitment and activation of natural killer cells in the tumor. Upon further encapsulation with chemotherapeutic agents, the VAs show unequaled cooperative effects in chemotherapy and immunotherapy in tumor-bearing mice. As far as it is known, this is the first report of a VA-based multifunctional combination therapy platform. This might lead to additional applications of vesicular antibodies in cancer theranostics.

Immunotherapy: Current Status and Future Perspectives

Hepatocellular carcinoma (HCC) has an increasing incidence and dismal prognosis, with few systemic treatments approved, including several small molecule tyrosine kinase inhibitors. The application of immune checkpoint inhibitors (ICIs) to HCC has resulted in durable activity, and further evaluation is ongoing. In this review, we discuss the immunologic principles and the mechanism of action of the ICIs and present the relevant clinical data. Furthermore, we provide an overview of the current and emerging immunotherapeutic approaches for HCC, such as combination treatments, vaccines, and cellular therapies.

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

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

Generation of an anti-desmoglein 3 antibody without pathogenic activity of pemphigus vulgaris for therapeutic application to squamous cell carcinoma

It is ideal for the target antigen of a cytotoxic therapeutic antibody against cancer to be cancer-specific, but such antigens are rare. Thus an alternative strategy for target selection is necessary. Desmoglein 3 (DSG3) is highly expressed in lung squamous cell carcinoma, while it is well-known that anti-DSG3 antibodies cause pemphigus vulgaris, an autoimmune disease. We evaluated DSG3 as a novel target by selecting an epitope that exerts efficacy against cancer with no pathogenic effects in normal tissues. Pathogenic anti-DSG3 antibodies induce skin blisters by inhibiting the cell–cell interaction in a Ca²⁺-dependent manner. We screened anti-DSG3 antibodies that bind DGS3 independent of Ca²⁺ and have high antibody-dependent cell cytotoxicity (ADCC) activity against DSG3-expressing cells. These selected antibodies did not inhibit cell–cell interaction and showed ADCC activity against squamous cell carcinoma cell lines. Furthermore, one of the DSG3 antibodies showed anti-tumour activity in tumour mouse models but did not induce adverse effects such as blister formation in the skin. Thus it was possible to generate an antibody against DSG3 by using an appropriate epitope that retained efficacy with no pathogenicity. This approach of epitope selection may expand the variety of druggable target molecules.

Engineering a bispecific antibody with a common light chain: Identification and optimization of an anti-CD3 epsilon and anti-GPC3 bispecific antibody, ERY974

The antibody drug market is rapidly expanding, and various antibody engineering technologies are being developed to create antibodies that can provide better benefit to patients. Although bispecific antibody drugs have been researched for more than 30 years, currently only a limited number of bispecific antibodies have achieved regulatory approval. Of the few successful examples of industrially manufacturing a bispecific antibody, the "common light chain format" is an elegant technology that simplifies the purification of a whole IgG-type bispecific antibody. Using this IgG format, the bispecific function can be introduced while maintaining the natural molecular shape of the antibody. In this article, we will first introduce the outline, prospects, and limitations of the common light chain format. Then, we will describe the identification and optimization process for ERY974, an anti-glypican-3 × anti-CD3ε T cell-redirecting bispecific antibody with a common light chain. This format includes one of Chugai's proprietary technologies, termed ART-Ig technology, which consists of a method to identify a common light chain, isoelectric point (pI) engineering to purify the desired bispecific IgG antibody from byproducts, and Fc heterodimerization by an electrostatic steering effect. Furthermore, we describe some tips for de-risking the antibody when engineering a T cell redirecting antibody.

I-124 codrituzumab imaging and biodistribution in patients with hepatocellular carcinoma

Background

I-124 codrituzumab (aka GC33), an antibody directed at Glypican 3, was evaluated in patients with hepatocellular carcinoma (HCC). Fourteen patients with HCC underwent baseline imaging with I-124 codrituzumab (~ 185 MBq, 10 mg). Seven of these patients undergoing sorafenib/immunotherapy with 2.5 or 5 mg/kg of cold codrituzumab had repeat imaging, with co-infusion of I-124 codrituzumab, as part of their immunotherapy treatment. Three patients who progressed while on sorafenib/immunotherapy were re-imaged after a 4-week washout period to assess for the presence of antigen. Serial positron emission tomography (PET) imaging and pharmacokinetics were performed following I-124 codrituzumab. An ELISA assay was used to determine “cold” codrituzumab serum pharmacokinetics and compare it to that of I-124 codrituzumab. Correlation of imaging results was performed with IHC. Short-term safety assessment was also evaluated.

Results

Thirteen patients had tumor localization on baseline I-124 codrituzumab; heterogeneity in tumor uptake was noted. In three patients undergoing repeat imaging while on immunotherapy/sorafenib, evidence of decreased I-124 codrituzumab uptake was noted. All three patients who underwent imaging after progression while on immunotherapy continued to have I-124 codrituzumab tumor uptake. Pharmacokinetics of I-124 codrituzumab was similar to that of other intact IgG. No significant adverse events were observed related to the I-124 codrituzumab.

Conclusions

I-124 codrituzumab detected tumor localization in most patients with HCC. Pharmacokinetics was similar to that of other intact iodinated humanized IgG. No visible cross-reactivity with normal organs was observed.

Electronic supplementary material

The online version of this article (10.1186/s13550-018-0374-8) contains supplementary material, which is available to authorized users.

Characterization of a new monoclonal anti-glypican-3 antibody specific to the hepatocellular carcinoma cell line, HepG2

AIM

To characterize the antigen on HepG2 cell that is specifically recognized by a new monoclonal antibody raised against human liver heparan sulfate proteoglycan (HSPG), clone 1E4-1D9.

METHODS

The antigen recognized by mAb 1E4-1D9 was immunoprecipitated and its amino acid sequence was analyzed LC/MS. The transmembrane domain, number of cysteine residues, and glycosylation sites were predicted from these entire sequences. Data from amino acid analysis was aligned with glypican-3 (https://www.ebi.ac.uk/Tools/msa/clustalo/). The competitive reaction of mAb 1E4-1D9 and anti-glypican-3 on HepG2 cells was demonstrated by indirect immunofluorescence and analyzed by flow cytometry. Moreover, co-immunoprecipitation of mAb 1E4-1D9 and anti-glypican-3 was performed in HepG2 cells by Western immunoblotting. The recognition by mAb 1E4-1D9 of a specific epitope on solid tumor and hematopoietic cell lines was studied using indirect immunofluorescence and analyzed by flow cytometry.

RESULTS

Monoclonal antibody 1E4-1D9 reacted with an HSPG isolated from human liver and a band of 67 kD was detected under both reducing and non-reducing conditions. The specific antigen pulled down by mAb 1E4-1D9, having a MW of 135 kD, was analyzed. The results showed two sequences of interest, gi30722350 (1478 amino acid) and gi60219551 (1378 amino acid). In both sequences no transmembrane regions were observed. Sequence number gi30722350 was 99.7% showed a match to FYCO1, a molecule involved in induction of autophagy. Sequence number gi60219551 contained 15 cysteines and 11 putative glycosylation sites with 6 predicted N-glycosylation sites. It was also matched with all PDZ domain proteins. Moreover, it showed an 85.7% match to glypican-3. Glypican-3 on HepG2 cells competitively reacted with both phycoerythrin-conjugated anti-glypican-3 and mAb 1E4-1C2 and resulted in an increase of double-stained cell population when higher concentration of mAb 1E4-1D9 was used. Moreover, antigens precipitated from HepG2 cell by anti-glypican-3 could be detected by mAb 1E4-1D9 and vice versa. The recognition of antigens, on other solid tumor cell lines, by mAb 1E4-1D9 was studied. The results demonstrated that mAb 1E4-1D9 reacted with Huh7, HepG2, HT29, MCF7, SW620, Caco2, B16F1, U937, K562 and Molt4 cells. It was also found to be weakly positive to SW1353 and HL60 and negative to H460 and Hela cell lines.

CONCLUSION

All findings show that mAb 1E4-1D9 specifically recognizes glypican-3. Moreover, a new partner molecule of glypican-3, FYCO1 is proposed based on the results from co-precipitation studies.

N+1 Engineering of an Aspartate Isomerization Hotspot in the Complementarity-Determining Region of a Monoclonal Antibody

Aspartate (Asp) isomerization is a common degradation pathway and a potential critical quality attribute that needs to be well characterized during the optimization and development of therapeutic antibodies. A putative Asp-serine (Ser) isomerization motif was identified in the complementarity-determining region of a humanized monoclonal antibody and shown to be a developability risk using accelerated stability analyses. To address this issue, we explored different antibody engineering strategies. Direct engineering of the Asp residue resulted in a greater than 5× loss of antigen-binding affinity and bioactivity, indicating a critical role for this residue. In contrast, rational engineering of the Ser residue at the n+1 position had a negligible impact on antigen binding affinity and bioactivity compared with the parent molecule. Furthermore, the n+1 engineering strategy effectively eliminated Asp isomerization as determined by accelerated stability analysis. This outcome affirms that the rate of Asp isomerization is strongly dependent on the identity of the n+1 residue. This report highlights a systematic antibody engineering strategy for mitigating an Asp isomerization developability risk during lead optimization.

Activity-based assessment of an engineered hyperthermophilic protein as a capture agent in paper-based diagnostic tests

Antibodies have traditionally served as the affinity reagents of choice in point-of-care diagnostic biosensors. However, this class of proteins is not ideally suited for this use, being poorly characterized and prone to thermal denaturation. Here, we present an activity-based assessment of an alternative engineered binding protein in a cellulose-based assay.

GPC-3 in hepatocellular carcinoma: current perspectives

Glypican-3 (GPC3), a member of heparan sulfate proteoglycans, attaches to the cell membrane and is frequently observed to be elevated in hepatocellular carcinoma (HCC). However, GPC3 is not detected in normal liver tissues and benign liver lesions. Consequently, GPC3 is currently being used as a diagnostic biomarker and HCC-specific positron emission computed tomography probe to identify HCCs in normal liver tissues and benign liver lesions. The overexpression of GPC-3 in serum or liver tissue also predicts poor prognosis for HCC patients. In addition, GPC3 promotes HCC growth and metastasis by activating the canonical Wnt and other signaling pathways. Targeting of GPC3, including GC33, HN3 and YP7, might offer new immunotherapeutic tools for HCC treatment.

Oxidation in the complementarity-determining regions differentially influences the properties of therapeutic antibodies

Therapeutic antibodies can undergo a variety of chemical modification reactions in vitro. Depending on the site of modification, either antigen binding or Fc-mediated functions can be affected. Oxidation of tryptophan residues is one of the post-translational modifications leading to altered antibody functionality. In this study, we examined the structural and functional properties of a therapeutic antibody construct and 2 affinity matured variants thereof. Two of the 3 antibodies carry an oxidation-prone tryptophan residue in the complementarity-determining region of the V_L domain. We demonstrate the differences in the stability and bioactivity of the 3 antibodies, and reveal differential degradation pathways for the antibodies susceptible to oxidation.

Aptamers against Cells Overexpressing Glypican 3 from Expanded Genetic Systems Combined with Cell Engineering and Laboratory Evolution

Laboratory in vitro evolution (LIVE) might deliver DNA aptamers that bind proteins expressed on the surface of cells. In this work, we used cell engineering to place glypican 3 (GPC3), a possible marker for liver cancer theranostics, on the surface of a liver cell line. Libraries were then built from a six-letter genetic alphabet containing the standard nucleobases and two added nucleobases (2-amino-8H-imidazo[1,2-a][1,3,5]triazin-4-one and 6-amino-5-nitropyridin-2-one), Watson-Crick complements from an artificially expanded genetic information system (AEGIS). With counterselection against non-engineered cells, eight AEGIS-containing aptamers were recovered. Five bound selectively to GPC3-overexpressing cells. This selection-counterselection scheme had acceptable statistics, notwithstanding the possibility that cells engineered to overexpress GPC3 might also express different off-target proteins. This is the first example of such a combination.

Novel therapeutic targets and predictive markers for hepatocellular carcinoma

INTRODUCTION

Following the approval of sorafenib as the first systemic agent for treatment of advanced hepatocellular carcinoma (HCC), there have been an increasing number of targeted treatments under testing for the cancer. However, most of the recently published drug trials in HCC failed to produce remarkable results. The researchers are actively pursuing novel therapeutic targets as well as predictive biomarker for treatment of HCC.

AREAS COVERED

This review discusses a number of potential novel targets for drug development of HCC. Focus is put on the underlying rationale for therapeutic development of the target and the possibility of using a predictive biomarker to select patients for drug testing.

EXPERT OPINION

Future direction of drug development will be discussed. Notably, a clinical trial on drug testing in HCC should be shifted from all-comers approach to selected populations based on underlying viral etiology and molecular targets. A study to evaluate predictive biomarker is crucial to the development of targeted agents for HCC. Design of clinical trials on HCC should introduce measures to encourage acquisition of tumor and plasma samples for biomarker development.

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.

Critical analysis of the potential of targeting GPC3 in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a leading cause of cancer-related deaths worldwide. The treatment options for patients with advanced HCC are limited, and novel treatment strategies are required urgently. Glypican-3 (GPC3), a member of the glypican family of heparan sulfate proteoglycans, is overexpressed in 72%−81% of HCC cases, and is correlated with a poor prognosis. GPC3 regulates both stimulatory and inhibitory signals, and plays a key role in regulating cancer cell growth. GPC3 is released into the serum, and so might be a useful diagnostic marker for HCC. GPC3 is also used as an immunotherapeutic target in HCC. A Phase I study of a humanized anti-GPC3 monoclonal antibody, GC33, revealed a good safety profile and potential antitumor activity, and a Phase II trial is currently ongoing. In addition, the authors’ investigator-initiated Phase I study of a GPC3-derived peptide vaccine showed good safety and tolerability, and demonstrated that the GPC3 peptide-specific cytotoxic T-lymphocyte frequency in peripheral blood correlated with overall survival in HCC patients. A sponsor-initiated Phase I clinical trial of a three-peptide cocktail vaccine, which includes a GPC3-derived peptide, is also underway. GPC3 is currently recognized as a promising therapeutic target and diagnostic marker for HCC. This review introduces the recent progress in GPC3 research, from biology to clinical impact.

Glypican-3 antibodies: a new therapeutic target for liver cancer

Glypican-3 (GPC3) is an emerging therapeutic target in hepatocellular carcinoma (HCC), even though the biological function of GPC3 remains elusive. Currently human (MDX-1414 and HN3) and humanized mouse (GC33 and YP7) antibodies that target GPC3 for HCC treatment are under different stages of preclinical or clinical development. Humanized mouse antibody GC33 is being evaluated in a phase II clinical trial. Human antibodies MDX-1414 and HN3 are under different stages of preclinical evaluation. Here, we summarize current evidence for GPC3 as a new target in liver cancer, discuss both its oncogenic function and its mode of actions for current antibodies, and evaluate potential challenges for GPC3-targeted anti-cancer therapies.

New targets for glycosaminoglycans and glycosaminoglycans as novel targets

Biological functions of a variety of proteins are mediated via their interaction with glycosaminoglycans (GAGs). The structural diversity within the wide GAG landscape provides individual interaction sites for a multitude of proteins involved in several pathophysiological processes. This 'GAG angle' of such proteins as well as their specific GAG ligands give rise to novel therapeutic concepts for drug development. Current glycomic technologies to elucidate the glycan structure-function relationships, methods to investigate the selectivity and specificity of glycan-protein interactions and existing therapeutic approaches to interfere with GAG-protein interactions are discussed.

Structure-based design of decoy chemokines as a way to explore the pharmacological potential of glycosaminoglycans

Glycosaminoglycans (GAGs) are a class of highly negatively charged, unbranched, O-linked polysaccharides that are involved in many diseases. Their role as a protein-binding matrix on cell surfaces has long been recognized, but therapeutic approaches to interfere with protein-GAG interactions have been limited due to the complex chemistry of GAGs, on one hand, and due to the lack of specific antibodies against GAGs, on the other hand. We have developed a protein engineering platform (the so-called CellJammer(®) technology), which enables us to introduce higher GAG-binding affinity into wild-type GAG-binding proteins and to combine this with impaired biological, receptor-binding function. Chemokines are among the prototypic GAG-binding proteins and here we present selected results of our CellJammer technology applied to several of these proinflammatory proteins. An overview is given of our lead decoy protein, PA401, which is a CXCL8-based mutant protein with increased GAG-binding affinity and decreased CXCR1/2 binding and activation. Major results from our CCL2 and CCL5 programmes are also summarized and the potential for clinical application of these decoy proteins is presented.

Therapeutically targeting glypican-3 via a conformation-specific single-domain antibody in hepatocellular carcinoma

Glypican-3 (GPC3) has emerged as a candidate therapeutic target in hepatocellular carcinoma (HCC), but the oncogenic role of GPC3 in HCC is poorly understood. Here, we report a human heavy-chain variable domain antibody, HN3, with high affinity (Kd = 0.6 nM) for cell-surface-associated GPC3 molecules. The human antibody recognized a conformational epitope that requires both the amino and carboxy terminal domains of GPC3. HN3 inhibited proliferation of GPC3-positive cells and exhibited significant inhibition of HCC xenograft tumor growth in nude mice. The underlying mechanism of HN3 action may involve cell-cycle arrest at G1 phase through Yes-associated protein signaling. This study suggests a previously unrecognized mechanism for GPC3-targeted cancer therapy.

Engineering a therapeutic IgG molecule to address cysteinylation, aggregation and enhance thermal stability and expression

Antibodies can undergo a variety of covalent and non-covalent degradation reactions that have adverse effects on efficacy, safety, manufacture and storage. We had identified an antibody to Angiopoietin 2 (Ang2 mAb) that neutralizes Ang2 binding to its receptor in vitro and inhibits tumor growth in vivo. Despite favorable pharmacological activity, the Ang2 mAb preparations were heterogeneous, aggregated rapidly and were poorly expressed. Here, we report the engineering of the antibody variable and constant domains to generate an antibody with reduced propensity to aggregate, enhanced homogeneity, 11°C elevated T(m), 26-fold improved level of expression and retained activity. The engineered molecule, MEDI-3617, is now compatible with the large scale material supply required for clinical trials and is currently being evaluated in Phase 1 in cancer patients. This is the first report to describe the stability engineering of a therapeutic antibody addressing non canonical cysteine residues and the design strategy reported here is generally applicable to other therapeutic antibodies and proteins.

First-in-man phase I study of GC33, a novel recombinant humanized antibody against glypican-3, in patients with advanced hepatocellular carcinoma

PURPOSE

GC33 is a novel recombinant fully humanized monoclonal antibody that binds to human glypican-3 (GPC3). The antitumor activity of GC33 was shown in preclinical models of hepatocellular carcinoma (HCC). This first-in-man clinical trial was conducted to evaluate the safety, pharmacokinetic characteristics, and preliminary efficacy of GC33 in patients with advanced HCC.

EXPERIMENTAL DESIGN

Patients with measurable, histologically proven, advanced HCC were enrolled to a dose-escalation study of GC33 (2.5-20 mg/kg) given intravenously weekly. The primary endpoint was to determine the maximum tolerated dose of GC33 for further development. Pharmacokinetic characteristics were measured in serum samples. Immunohistochemistry was conducted on tumor biopsies to evaluate GPC3 expression. Tumor response was assessed every 8 weeks using Response Evaluation Criteria in Solid Tumors criteria.

RESULTS

Twenty patients were enrolled and treated with GC33. A maximum tolerated dose was not reached as there were no dose-limiting toxicities (DLT) up to the highest planned dose level. Common adverse events with all grades included fatigue (50%), constipation (35%), headache (35%), and hyponatremia (35%). The incidence of adverse events seemed not to be dose dependent. Trough serum concentrations at steady state were in excess of target concentration at doses of 5 mg/kg or greater. Median time to progression (TTP) was 26.0 weeks in the GPC3 high expression group and 7.1 weeks in the low expression group (P = 0.033).

CONCLUSION

This study shows that GC33 was well tolerated in advanced HCC and provides preliminary evidence that GPC3 expression in HCC may be associated with the clinical benefit to GC33 that warrants prospective evaluation.

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.

Gene expression profiling of liver cancer stem cells by RNA-sequencing

BACKGROUND

Accumulating evidence supports that tumor growth and cancer relapse are driven by cancer stem cells. Our previous work has demonstrated the existence of CD90(+) liver cancer stem cells (CSCs) in hepatocellular carcinoma (HCC). Nevertheless, the characteristics of these cells are still poorly understood. In this study, we employed a more sensitive RNA-sequencing (RNA-Seq) to compare the gene expression profiling of CD90(+) cells sorted from tumor (CD90(+)CSCs) with parallel non-tumorous liver tissues (CD90(+)NTSCs) and elucidate the roles of putative target genes in hepatocarcinogenesis.

METHODOLOGY/PRINCIPAL FINDINGS

CD90(+) cells were sorted respectively from tumor and adjacent non-tumorous human liver tissues using fluorescence-activated cell sorting. The amplified RNAs of CD90(+) cells from 3 HCC patients were subjected to RNA-Seq analysis. A differential gene expression profile was established between CD90(+)CSCs and CD90(+)NTSCs, and validated by quantitative real-time PCR (qRT-PCR) on the same set of amplified RNAs, and further confirmed in an independent cohort of 12 HCC patients. Five hundred genes were differentially expressed (119 up-regulated and 381 down-regulated genes) between CD90(+)CSCs and CD90(+)NTSCs. Gene ontology analysis indicated that the over-expressed genes in CD90(+)CSCs were associated with inflammation, drug resistance and lipid metabolism. Among the differentially expressed genes, glypican-3 (GPC3), a member of glypican family, was markedly elevated in CD90(+)CSCs compared to CD90(+)NTSCs. Immunohistochemistry demonstrated that GPC3 was highly expressed in forty-two human liver tumor tissues but absent in adjacent non-tumorous liver tissues. Flow cytometry indicated that GPC3 was highly expressed in liver CD90(+)CSCs and mature cancer cells in liver cancer cell lines and human liver tumor tissues. Furthermore, GPC3 expression was positively correlated with the number of CD90(+)CSCs in liver tumor tissues.

CONCLUSIONS/SIGNIFICANCE

The identified genes, such as GPC3 that are distinctly expressed in liver CD90(+)CSCs, may be promising gene candidates for HCC therapy without inducing damages to normal liver stem cells.

Validation of glypican-3-specific scFv isolated from paired display/secretory yeast display library

BACKGROUND

Glypican-3 (GPC3) is a heparan-sulfate proteoglycan frequently expressed on the cell membrane of malignant hepatocytes in hepatocellular carcinoma. The capacity for screening potential antibodies in vitro using human hepatocellular lines is critical to ensure binding to this highly post-translationally modified glycophosphatidylinositiol-linked protein. We hypothesized that we could utilize a recently described paired display/secretory yeast library to isolate human-derived scFv against glypican-3 for potential diagnostic and/or therapeutic application.

RESULTS

Using two different biotinylated antigen targets, a synthesized 29mer fragment GPC3(550-558) and a truncated GPC3(368-548) fused with glutathione S-transferase (GST) we enriched the yeast display library to greater than 30% target-specific yeast with both positive selection and depletion of streptavidin- and GST-specific clones. After cloning of scFv cDNA from the enriched sub-library, scFv specificity was validated by ELISA for binding to recombinant protein from prokaryotic and eukaryotic sources and ultimately naturally presented human protein on the cell membrane of human hepatocellular cell lines. Specificity was confirmed using non-expressing cell lines and shRNA knockdown. Ultimately, five unique scFv with affinity EC(50) ranging from 5.0-110.9 nM were identified.

CONCLUSIONS

Using a paired display/secretory yeast library, five novel and unique scFvs for potential humoral or chimeric therapeutic development in human hepatocellular carcinoma were isolated and characterized.

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.

Targeting of hepatocellular carcinoma with glypican-3-targeting peptide ligand

Hepatocellular carcinoma is a common malignancy. The carcinoma cells express glypican-3 (GPC-3) on the cell membrane. GPC-3 is also expressed in melanoma cells. Therefore, GPC-3 might be a potential target for tumor imaging or therapy. Here, proteomic mass spectrometry was used to identify peptides that target GPC-3-expressing tumors. A mammalian expression vector expressing a FLAG-GPC-3 fusion protein was cloned for immunoprecipitation. With the use of liposomes, the vector was transfected into HepG2 (HepG2/FLAG-GPC-3) and HEK 293 cells, and the transfected cell lines were selected with geneticin. HepG2/FLAG-GPC-3 cells were used for immunoprecipitation of FLAG-GPC-3 fusion protein. Seven peptide candidates (L1-L7) were selected for GPC-3-targeting ligands by mass spectrometric analysis. The L5 peptide with 14 amino acids (Arg-Leu-Asn-Val-Gly-Gly-Thr-Tyr-Phe-Leu-Thr-Thr-Arg-Gln) showed selective binding to the GPC-3-expressing tumor cells, as did a shortened L5 peptide (L5-2) with seven amino acids (Tyr-Phe-Leu-Thr-Thr-Arg-Gln). These peptide ligands have potential as targeting moieties to GPC-3-expressing tumors for diagnostic and/or therapeutic purposes.

Engineering the variable region of therapeutic IgG antibodies

Since the first generation of humanized IgG1 antibodies reached the market in the late 1990s, IgG antibody molecules have been extensively engineered. The success of antibody therapeutics has introduced severe competition in developing novel therapeutic monoclonal antibodies, especially for promising or clinically validated targets. Such competition has led researchers to generate so-called second or third generation antibodies with clinical differentiation utilizing various engineering and optimization technologies. Parent IgG antibodies can be engineered to have improved antigen binding properties, effector functions, pharmacokinetics, pharmaceutical properties and safety issues. Although the primary role of the antibody variable region is to bind to the antigen, it is also the main source of antibody diversity and its sequence affects various properties important for developing antibody therapeutics. Here we review recent research activity in variable region engineering to generate superior antibody therapeutics.

GPC3 fused to an alpha epitope of HBsAg acts as an immune target against hepatocellular carcinoma associated with hepatitis B virus

BACKGROUND

The incidence of hepatocellular carcinoma (HCC) in China is closely related to the population infected with hepatitis B virus (HBV). HCC cells with HBV secrete soluble HBsAg into blood but do not express it on the cell membrane. This study aimed to construct and investigate a new glycosyl-phosphatidylinositol (GPI)-anchored protein (GPC3+alpha+EGFP) as a DNA vaccine against HCC associated with HBV.

METHODS

A recombinant plasmid (pcDNA3.1(+)/GPC3+ alpha+EGFP) was constructed and verified by restriction endonuclease digestion and sequencing. pcDNA3.1(+)/GPC3+alpha+EGFP was transfected into HepG2 cells (experimental group) using lipofectamine 2000. pEGFP-N1-transfected HepG2 cells were used as a negative control, and non-transfected HepG2 cells served as a blank control. HepG2 cells that steadily expressed the fusion protein GPC3+alpha+EGFP were screened by G418, propagated, and co-cultured with lymphocytes from healthy donors. Cell proliferation was measured by the classic sulforhodamine B assay. Apoptosis was assessed by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL), and Fas gene transcription was determined by quantitative fluorescent PCR.

RESULTS

The pcDNA3.1(+)/GPC3+alpha+EGFP plasmid was successfully constructed. In the experimental group, green fluorescence was observed at the cell periphery and in the cytoplasm, whereas in the negative control group, fluorescence was evenly distributed throughout the cell. Proliferation of the experimental group significantly decreased after 72 hours compared to the negative and blank control groups. Furthermore, the number of apoptotic cells was statistically different among the three groups as determined by a contingency table Chi-square test; the experimental group had the highest incidence of apoptosis. Fas gene transcription in the experimental group was higher than in the two control groups, and an increasing trend with time in the experimental group was observed.

CONCLUSION

A chimeric, membrane-anchored protein, GPC3+alpha+EGFP, localized to the membrane of HepG2 cells and inhibited proliferation and accelerated apoptosis through a Fas-FasL pathway after co-cultivation with lymphocytes.