Binding activities and antitumor properties of a new mouse/human chimeric antibody specific for GD2 ganglioside antigen

F77 antigen is a promising target for adoptive T cell therapy of prostate cancer

Adoptive immunotherapy using chimeric antigen receptor (CAR) T cells has made significant success in treating hematological malignancies, paving the way for solid tumors like prostate cancer. However, progress is impeded by a paucity of suitable target antigens. A novel carbohydrate antigen, F77, is expressed on both androgen-dependent and androgen-independent prostate cancer cells, making it a potential immunotherapy target. This study entails the generation and evaluation of a second-generation CAR against a carbohydrate antigen on malignant prostate cancer cells. Using a single chain fragment variable (scFv) from an F77-specific mouse monoclonal antibody, we created second-generation CARs with CD28 and CD137 (4-1BB) costimulatory signals. F77 expressing lentiviral CAR T cells produce cytokines and kill tumor cells in a F77 expression-dependent manner. These F77-specific CAR T cells eradicate prostate tumors in a human xenograft model employing PC3 cells. These findings validate F77 as a promising immunotherapeutic target for prostate cancer and other malignancies with this aberrant carbohydrate structure.

Therapeutic efficacy of antibody-drug conjugates targeting GD2-positive tumors

Background

Both ganglioside GD2-targeted immunotherapy and antibody-drug conjugates (ADCs) have demonstrated clinical success as solid tumor therapies in recent years, yet no research has been carried out to develop anti-GD2 ADCs against solid tumors. This is the first study to analyze cytotoxic activity of clinically relevant anti-GD2 ADCs in a wide panel of cell lines with varying GD2 expression and their effects in mouse models of GD2-positive solid cancer.

Methods

Anti-GD2 ADCs were generated based on the GD2-specific antibody ch14.18 approved for the treatment of neuroblastoma and commonly used drugs monomethyl auristatin E (MMAE) or F (MMAF), conjugated via a cleavable linker by thiol-maleimide chemistry. The antibody was produced in a mammalian expression system, and its specific binding to GD2 was analyzed. Antigen-binding properties and biodistribution of the ADCs in mice were studied in comparison with the parent antibody. Cytotoxic effects of the ADCs were evaluated in a wide panel of GD2-positive and GD2-negative tumor cell lines of neuroblastoma, glioma, sarcoma, melanoma, and breast cancer. Their antitumor effects were studied in the B78-D14 melanoma and EL-4 lymphoma syngeneic mouse models.

Results

The ch14.18-MMAE and ch14.18-MMAF ADCs retained antigen-binding properties of the parent antibody. Direct dependence of the cytotoxic effect on the level of GD2 expression was observed in cell lines of different origin for both ADCs, with IC50 below 1 nM for the cells with high GD2 expression and no cytotoxic effect for GD2-negative cells. Within the analyzed cell lines, ch14.18-MMAF was more effective in the cells overexpressing GD2, while ch14.18-MMAE had more prominent activity in the cells expressing low GD2 levels. The ADCs had a similar biodistribution profile in the B78-D14 melanoma model compared with the parent antibody, reaching 7.7% ID/g in the tumor at 48 hours postinjection. The average tumor size in groups treated with ch14.18-MMAE or ch14.18-MMAF was 2.6 times and 3.8 times smaller, respectively, compared with the control group. Antitumor effects of the anti-GD2 ADCs were also confirmed in the EL-4 lymphoma model.

Conclusion

These findings validate the potential of ADCs targeting ganglioside GD2 in treating multiple GD2-expressing solid tumors.

Monoclonal Antibody Therapies for High Risk Neuroblastoma

Monoclonal antibodies (mAbs) are part of the standard of care for the treatment of many adult solid tumors. Until recently none have been approved for use in children with solid tumors. Neuroblastoma (NB) is the most common extracranial solid tumor in children. Those with high-risk disease, despite treatment with very intensive multimodal therapy, still have poor overall survival. Results of treatment with an immunotherapy regimen using a chimeric (human/mouse) mAb against a cell surface disialoganglioside (GD2) have changed the standard of care for these children and resulted in the first approval of a mAb for use in children with solid tumors. This article will review the use of the various anti-GD2 mAbs in children with NB, methods that have been or are being evaluated for enhancing their efficacy, as well as review other promising antigenic targets for the therapeutic use of mAbs in children with NB.

Antiganglioside Antibodies and Inflammatory Response in Cutaneous Melanoma

INTRODUCTION

Endogenously produced antiganglioside antibodies could affect the evolution of cutaneous melanoma. Epidemiological and experimental evidence suggest "chronic inflammation" to be one of the hallmarks in skin cancers. The aim of the study was to characterize the relation between antiganglioside antibodies and inflammation in cutaneous melanoma focusing on gangliosides GM1, GM2, GM3, GD1a, GD1b, GT1b, GQ1b. Material and Method. We performed an observational study that included 380 subjects subdivided into three groups: patients with metastatic melanoma (170 cases), patients with primary melanoma (160 cases), and healthy subjects (50 subjects). The assessment of antiganglioside antibodies, IgG, and IgM classes, against -GM1, -GM2, -GM3, -GD1a, -GD1b, -GT1b, -GQ1b was performed using immunoblot technique (EUROLine kit).

RESULTS

The presence of IgG and IgM antiganglioside antibodies in primary melanoma was (%), as follows: anti-GM1 (5.0 and 13.1), -GM2 (1.8 and 18.1), -GM3 (0.6 and 5.6), -GD1a (0.6 and 15.0), -GD1b (3.7 and 10.7), -GT1b (0.0 and 13.1), -GQ1b (0.0 and 5.0). In metastatic melanoma, the level of antiganglioside antibodies was significantly lower compared with primary melanoma (p < 0.05), while in the control group they were absent. Antiganglioside antibodies anti-GM1 and -GD1a were positively correlated, while anti-GM3, -GD1b, and -GT1b were negatively associated with the inflammatory markers, interleukin 8 (IL-8), and C reactive protein (CRP).

CONCLUSIONS

Tumour ganglioside antigens generate an immune response in patients with primary melanomas. The host's ability to elaborate an early antiganglioside response could be considered as a defence mechanism, directed toward eliminating a danger signal from the tumour microenvironment. Antiganglioside antibodies associated with inflammation markers could be used as diagnostic, monitoring, and treatment tools in patients with cutaneous melanoma.

Spotlight on dinutuximab in the treatment of high-risk neuroblastoma: development and place in therapy

Neuroblastoma (NB) is a pediatric cancer of the sympathetic nervous system which accounts for 8% of childhood cancers. Most NBs express high levels of the disialoganglioside GD2. Several antibodies have been developed to target GD2 on NB, including the human/mouse chimeric antibody ch14.18, known as dinutuximab. Dinutuximab used in combination with granulocyte-macrophage colony-stimulating factor, interleukin-2, and isotretinoin (13-cis-retinoic acid) has a US Food and Drug Administration (FDA)-registered indication for treating high-risk NB patients who achieved at least a partial response to prior first-line multi-agent, multimodality therapy. The FDA registration resulted from a prospective randomized trial assessing the benefit of adding dinutuximab + cytokines to post-myeloablative maintenance therapy for high-risk NB. Dinutuximab has also shown promising antitumor activity when combined with temozolomide and irinotecan in treating NB progressive disease. Clinical activity of dinutuximab and other GD2-targeted therapies relies on the presence of the GD2 antigen on NB cells. Some NBs have been reported as GD2 low or negative, and such tumor cells could be nonresponsive to anti-GD2 therapy. As dinutuximab relies on complement and effector cells to mediate NB killing, factors affecting those components of patient response may also decrease dinutuximab effectiveness. This review summarizes the development of GD2 antibody-targeted therapy, the use of dinutuximab in both up-front and salvage therapy for high-risk NB, and the potential mechanisms of resistance to dinutuximab.

Ganglioside GD2 in reception and transduction of cell death signal in tumor cells

BACKGROUND

Ganglioside GD2 is expressed on plasma membranes of various types of malignant cells. One of the most promising approaches for cancer immunotherapy is the treatment with monoclonal antibodies recognizing tumor-associated markers such as ganglioside GD2. It is considered that major mechanisms of anticancer activity of anti-GD2 antibodies are complement-dependent cytotoxicity and/or antibody-mediated cellular cytotoxicity. At the same time, several studies suggested that anti-GD2 antibodies are capable of direct induction of cell death of number of tumor cell lines, but it has not been investigated in details. In this study we investigated the functional role of ganglioside GD2 in the induction of cell death of multiple tumor cell lines by using GD2-specific monoclonal antibodies.

METHODS

Expression of GD2 on different tumor cell lines was analyzed by flow cytometry using anti-GD2 antibodies. By using HPTLC followed by densitometric analysis we measured the amount of ganglioside GD2 in total ganglioside fractions isolated from tumor cell lines. An MTT assay was performed to assess viability of GD2-positive and -negative tumor cell lines treated with anti-GD2 mAbs. Cross-reactivity of anti-GD2 mAbs with other gangliosides or other surface molecules was investigated by ELISA and flow cytometry. Inhibition of GD2 expression was achieved by using of inhibitor for ganglioside synthesis PDMP and/or siRNA for GM2/GD2 and GD3 synthases.

RESULTS

Anti-GD2 mAbs effectively induced non-classical cell death that combined features of both apoptosis and necrosis in GD2-positive tumor cells and did not affect GD2-negative tumors. Anti-GD2 mAbs directly induced cell death, which included alteration of mitochondrial membrane potential, induction of apoptotic volume decrease and cell membrane permeability. This cytotoxic effect was mediated exclusively by specific binding of anti-GD2 antibodies with ganglioside GD2 but not with other molecules. Moreover, the level of GD2 expression correlated with susceptibility of tumor cell lines to cytotoxic effect of anti-GD2 antibodies.

CONCLUSIONS

Results of this study demonstrate that anti-GD2 antibodies not only passively bind to the surface of tumor cells but also directly induce rapid cell death after the incubation with GD2-positive tumor cells. These results suggest a new role of GD2 as a receptor that actively transduces death signal in malignant cells.

Determination of carbohydrate structure recognized by prostate-specific F77 monoclonal antibody through expression analysis of glycosyltransferase genes

This study reports the determination of the carbohydrate epitope of monoclonal antibody F77 previously raised against human prostate cancer PC-3 cells (Zhang, G., Zhang, H., Wang, Q., Lal, P., Carroll, A. M., de la Llera-Moya, M., Xu, X., and Greene, M. I. (2010) Proc. Natl. Acad. Sci. U. S. A. 107, 732–737). We performed a series of co-transfections using mammalian expression vectors encoding specific glycosyltransferases. We thereby identified branching enzymes and FUT1 (required for Fucα1→2Gal linkage) as being essential for F77 antigen formation. When immortalized normal prostate 267B1 cells were transfected with FUT1 alone, cells showed weak expression of F77 antigen. By contrast, cells co-transfected with FUT1 plus either GCNT1, GCNT2, or GCNT3 (an enzyme required to form GlcNAcβ1→6Gal/GalNAc) showed robust F77 antigen expression, suggesting that F77 specifically binds to Fucα1→2Galβ1→4GlcNAcβ1→6Gal/GalNAc. RT-PCR for FUT1, GCNT1, GCNT2, and GCNT3 showed that F77-positive cell lines indeed express transcripts encoding FUT1 plus one GCNT. F77-positive prostate cancer cells transfected with siRNAs targeting FUT1, GCNT2, and GCNT3 showed significantly reduced F77 antigen, confirming the requirement of these enzymes for epitope synthesis. We also found that hypoxia induces F77 epitope expression in immortalized prostate RWPE1 cells, which express F77 antigen moderately under normoxia but at an elevated level under hypoxia. Quantitative RT-PCR demonstrated up-regulation of FUT1, GCNT2, and GCNT3 transcripts in RWPE1 cells under hypoxia, suggesting that hypoxia up-regulates glycosyltransferase expression required for F77 antigen synthesis. These results define the F77 epitope and provide a potential mechanism for F77 antigen synthesis in malignant prostate cancer.

Chimeric antibody c.8B6 to O-acetyl-GD2 mediates the same efficient anti-neuroblastoma effects as therapeutic ch14.18 antibody to GD2 without antibody induced allodynia

Background

Anti-GD2 antibody is a proven therapy for GD2-postive neuroblastoma. Monoclonal antibodies against GD2, such as chimeric mAb ch14.18, have become benchmarks for neuroblastoma therapies. Pain, however, can limit immunotherapy with anti-GD2 therapeutic antibodies like ch14.18. This adverse effect is attributed to acute inflammation via complement activation on GD2-expressing nerves. Thus, new strategies are needed for the development of treatment intensification strategies to improve the outcome of these patients.

Methodology/Principal Findings

We established the mouse-human chimeric antibody c.8B6 specific to OAcGD2 in order to reduce potential immunogenicity in patients and to fill the need for a selective agent that can kill neuroblastoma cells without inducing adverse neurological side effects caused by anti-GD2 antibody immunotherapy. We further analyzed some of its functional properties compared with anti-GD2 ch14.18 therapeutic antibody. With the exception of allodynic activity, we found that antibody c.8B6 shares the same anti-neuroblastoma attributes as therapeutic ch14.18 anti-GD2 mAb when tested in cell-based assay and in vivo in an animal model.

Conclusion/Significance

The absence of OAcGD2 expression on nerve fibers and the lack of allodynic properties of c.8B6–which are believed to play a major role in mediating anti-GD2 mAb dose-limiting side effects–provide an important rationale for the clinical application of c.8B6 in patients with high-risk neuroblastoma.

Tumor targeting of the IL-15 superagonist RLI by an anti-GD2 antibody strongly enhances its antitumor potency

Immunocytokines (ICKs) targeting cytokines to the tumor environment using antibodies directed against a tumor-associated antigen often have a higher therapeutic index than the corresponding unconjugated cytokines. Various ICKs displaying significant antitumoral effects in several murine tumor models have already been developed, and some of them, in particular interleukin (IL)-2-based ICKs, are in Phase II clinical trials. Although sharing common biological activities with IL-2 in vitro, IL-15 is now considered as having a better potential in antitumor immunotherapeutical strategies and has been shown to be less toxic than IL-2 in preclinical studies. We previously developed the fusion protein RLI, linking a soluble form of human IL-15Rα-sushi+ domain to human IL-15. RLI showed better biological activities than IL-15 in vitro as well as higher antitumoral effects in vivo in murine and human cancer models. Here, we investigated, in the context of an ICK, the effect of associating RLI with an antibody targeting the GD2 ganglioside, a validated tumoral target expressed on many neurectodermal tumors. Anti-GD2-RLI fully retained the cytokine potential of RLI and the antibody effector functions (antibody-dependent cellular cytotoxicity and complement-dependent cytotoxicity). It displayed strong antitumor activities in two syngeneic cancer models in immunocompetent mice (subcutaneous EL4 and metastatic NXS2). Its therapeutic potency was higher than those of RLI and anti-GD2 alone or in combination. We suggest that this is related to its bifunctional (cytokine and antibody) nature.

Cell cycle arrest and apoptosis induced by O-acetyl-GD2-specific monoclonal antibody 8B6 inhibits tumor growth in vitro and in vivo

O-Acetyl-GD2 ganglioside is suitable antigen for tumor immunotherapy with specific therapeutic antibody. Here, we investigate the anti-tumor activity of O-acetyl-GD2-specific monoclonal antibody 8B6 on O-acetyl-GD2-positive tumor cells. The results indicated that mAb 8B6 induced growth inhibition of O-acetyl-GD2-expressing tumor cell lines in vitro with features of cell cycle arrest and apoptosis. Monoclonal antibody 8B6 treatment was also very effective in suppression of tumor growth in mice by reducing the proliferation index and increasing the apoptotic index. Such a study represents a useful framework to optimize immunotherapy with O-acetyl-GD2-specific antibody in combination with chemotherapeutic agents.

Anti-Gb3 monoclonal antibody inhibits angiogenesis and tumor development

Inhibiting the growth of tumor vasculature represents one of the relevant strategies against tumor progression. Between all the different pro-angiogenic molecular targets, plasma membrane glycosphingolipids have been under-investigated. In this present study, we explore the anti-angiogenic therapeutic advantage of a tumor immunotherapy targeting the globotriaosylceramide Gb3. In this purpose, a monoclonal antibody against Gb3, named 3E2 was developed and characterized. We first demonstrate that Gb3 is over-expressed in proliferative endothelial cells relative to quiescent cells. Then, we demonstrate that 3E2 inhibits endothelial cell proliferation in vitro by slowing endothelial cell proliferation and by increasing mitosis duration. Antibody 3E2 is further effective in inhibiting ex vivo angiogenesis in aorta ring assays. Moreover, 3E2 treatment inhibits NXS2 neuroblastoma development and liver metastases spreading in A/J mice. Immunohistology examination of the NXS2 metastases shows that only endothelial cells, but not cancer cells express Gb3. Finally, 3E2 treatment diminishes tumor vessels density, proving a specific therapeutic action of our monoclonal antibody to tumor vasculature. Our study demonstrates that Gb3 is a viable alternative target for immunotherapy and angiogenesis inhibition.

The sweet side of tumor immunotherapy

Carbohydrate signatures on tumor cells have functional implications in tumor growth and metastasis and constitute valuable tools in cancer diagnosis and immunotherapy. Increasing data regarding the mechanisms by which they are recognized by the immune system are facilitating the design of more efficient immunotherapeutic protocols based on cancer-associated glycan structures. Recent molecular and proteomic studies revealed that carbohydrates are recognized, not only by B cells and antibodies, but also by cells from the innate arm of immunity, as well as by T cells, and are able to induce specific T-cell immunity and cytotoxicity. In this review, we discuss and update the different strategies targeting tumor-associated carbohydrate antigens that are being evaluated for antitumor immunotherapy, an approach that will be highly relevant, especially when combined with other strategies, in the future fight against cancer.

Immunology in the clinic review series; focus on cancer: glycolipids as targets for tumour immunotherapy

Research into aberrant glycosylation and over-expression of glycolipids on the surface of the majority of cancers, coupled with a knowledge of glycolipids as functional molecules involved in a number of cellular physiological pathways, has provided a novel area of targets for cancer immunotherapy. This has resulted in the development of a number of vaccines and monoclonal antibodies that are showing promising results in recent clinical trials.

A monoclonal antibody to O-acetyl-GD2 ganglioside and not to GD2 shows potent anti-tumor activity without peripheral nervous system cross-reactivity

Background

Monoclonal antibodies (mAb) against GD2 ganglioside have been shown to be effective for the treatment of neuroblastoma. Beneficial actions are, however, associated with generalized pain due to the binding of anti- GD2 mAbs to peripheral nerve fibers followed by complement activation. Neuroblastoma cells that express GD2 also express its O-acetyl derivative, O-acetyl- GD2 ganglioside (OAcGD2). Hence, we investigated the distribution of OAcGD2 in human tissues using mAb 8B6 to study the cross-reactivity of mAb 8B6 with human tissues.

Methodology/Principal Findings

The distribution of OAcGD2 was performed in normal and malignant tissues using an immunoperoxydase technique. Anti-tumor properties of mAb 8B6 were studied in vitro and in vivo in a transplanted tumor model in mice. We found that OAcGD2 is not expressed by peripheral nerve fibers. Furthermore, we demonstrated that mAb 8B6 was very effective in the in vitro and in vivo suppression of the growth of tumor cells. Importantly, mAb 8B6 anti-tumor efficacy was comparable to that of mAb 14G2a specific to GD2.

Conclusion/Significance

Development of therapeutic antibodies specific to OAcGD2 may offer treatment options with reduced adverse side effects, thereby allowing dose escalation of antibodies.

Human recombinant anti-thyroperoxidase autoantibodies: in vitro cytotoxic activity on papillary thyroid cancer expressing TPO

Background:

Thyroid cancers are difficult to treat due to their limited responsiveness to chemo- and radiotherapy. There is thus a great interest in and a need for alternative therapeutic approaches.

Results:

We studied the cytotoxic activity of anti-thyroperoxidase autoantibodies (anti-TPO aAbs, expressed in baculovirus/insect cell (B4) and CHO cells (B4′) or purified from patients' sera) against a papillary thyroid cancer (NPA) cell line. Anti-TPO aAbs from patients' sera led to a partial destruction of NPA cell line by complement-dependent cytotoxicity (CDC) and antibody-dependent cell-mediated cytotoxicity (ADCC) and exhibited an anti-proliferative activity. Comparison of the cytotoxic activity of anti-TPO aAbs shows that B4′ induced an anti-proliferative effect and a better ADCC than B4, but a lower one than anti-TPO aAbs from patients' sera. Antibody-dependent cell-mediated cytotoxicity was increased when human peripheral blood mononuclear cells were used as effector cells, suggesting that FcγRs, CD64, CD32 and CD16 are involved. Indeed, anti-TPO aAbs from patients' sera, but not B4 and B4′, exhibited CDC activity.

Conclusions:

These data indicate that anti-TPO aAbs display moderate ADCC and anti-proliferative activities on NPA cells; IgG glycosylation appears to be important for cytotoxic activity and ADCC efficiency depends on FcγR-bearing cells. Finally, recombinant human anti-TPO aAbs cannot yet be considered as an optimal tool for the development of a novel therapeutic approach for thyroid cancer.

The GD2-specific 14G2a monoclonal antibody induces apoptosis and enhances cytotoxicity of chemotherapeutic drugs in IMR-32 human neuroblastoma cells

Neuroblastoma (NB) is the most common extracranial solid tumor of childhood. The majority of children suffers from high risk neuroblastoma and has disseminated disease at the time of diagnosis. Despite recent advances in chemotherapy, the prognoses for children with high risk NB remain poor. Therefore, new treatment modalities are urgently needed. GD2 ganglioside is an antigen that is highly expressed on NB cells with only limited distribution on healthy tissues. Consequently, it appears to be an ideal target for both active and passive immunotherapy. The immunological effector mechanisms mediated by anti-GD2 monoclonal antibodies (mAbs) have been already well characterized. However, a growing number of reports suggest that GD2-specific antibodies may exhibit anti-proliferative effects without the immune system involvement. Here, we have shown that anti-GD2 14G2a mAb is capable of decreasing survival of IMR-32 human neuroblastoma cells in a dose-dependent manner. Death induced by this antibody exhibited several characteristics typical for apoptosis such as increased number of Annexin V- and propidium iodide-positive cells, cleavage of caspase 3 and prominent rise in caspase activity. The use of a pan caspase inhibitor Z-VAD-fmk suggested that the killing potential of this mAb is partially caspase-dependent. 14G2a mAb was rapidly endocytosed upon antigen binding. Employment of chloroquine, an inhibitor of lysosomal degradation, did not rescue IMR-32 cells from antibody-induced cell death suggesting lack of ceramide involvement in the observed effect. Most importantly, our studies showed that at particular drug concentrations 14G2a mAb exerts a synergistic effect with doxorubicin and topotecan, as well as an additive effect with carboplatin in killing IMR-32 cells in vitro. Our results provide guidance regarding how to best combine GD2-specific 14G2a antibody with existing cancer therapeutic agents to improve available treatment modalities for neuroblastoma.