Expression of the gangliosides GM3, GD3 and GD2 in tissue sections of normal skin, naevi, primary and metastatic melanoma

Ganglioside GM3-based anticancer vaccines: Reviewing the mechanism and current strategies

Ganglioside GM3 is one of the most common membrane-bound glycosphingolipids. The over-expression of GM3 on tumor cells makes it defined as a tumor-associated carbohydrate antigen (TACA). The specific expression property in cancers, especially in melanoma, make it become an important target to develop anticancer vaccines or immunotherapies. However, in the manner akin to most TACAs, GM3 is an autoantigen facing with problems of low immunogenicity and easily inducing immunotolerance, which means itself only cannot elicit a powerful enough immune response to prevent or treat cancer. With a comparative understanding of the mechanisms that how immune system responses to the carbohydrate vaccines, this review summarizes the studies on the recent efforts to development GM3-based anticancer vaccines.

GD2-targeting therapy: a comparative analysis of approaches and promising directions

Disialoganglioside GD2 is a promising target for immunotherapy with expression primarily restricted to neuroectodermal and epithelial tumor cells. Although its role in the maintenance and repair of neural tissue is well-established, its functions during normal organism development remain understudied. Meanwhile, studies have shown that GD2 plays an important role in tumorigenesis. Its functions include proliferation, invasion, motility, and metastasis, and its high expression and ability to transform the tumor microenvironment may be associated with a malignant phenotype. Structurally, GD2 is a glycosphingolipid that is stably expressed on the surface of tumor cells, making it a suitable candidate for targeting by antibodies or chimeric antigen receptors. Based on mouse monoclonal antibodies, chimeric and humanized antibodies and their combinations with cytokines, toxins, drugs, radionuclides, nanoparticles as well as chimeric antigen receptor have been developed. Furthermore, vaccines and photoimmunotherapy are being used to treat GD2-positive tumors, and GD2 aptamers can be used for targeting. In the field of cell therapy, allogeneic immunocompetent cells are also being utilized to enhance GD2 therapy. Efforts are currently being made to optimize the chimeric antigen receptor by modifying its design or by transducing not only αβ T cells, but also γδ T cells, NK cells, NKT cells, and macrophages. In addition, immunotherapy can combine both diagnostic and therapeutic methods, allowing for early detection of disease and minimal residual disease. This review discusses each immunotherapy method and strategy, its advantages and disadvantages, and highlights future directions for GD2 therapy.

Biology of GD2 ganglioside: implications for cancer immunotherapy

Part of the broader glycosphingolipid family, gangliosides are composed of a ceramide bound to a sialic acid-containing glycan chain, and locate at the plasma membrane. Gangliosides are produced through sequential steps of glycosylation and sialylation. This diversity of composition is reflected in differences in expression patterns and functions of the various gangliosides. Ganglioside GD2 designates different subspecies following a basic structure containing three carbohydrate residues and two sialic acids. GD2 expression, usually restrained to limited tissues, is frequently altered in various neuroectoderm-derived cancers. While GD2 is of evident interest, its glycolipid nature has rendered research challenging. Physiological GD2 expression has been linked to developmental processes. Passing this stage, varying levels of GD2, physiologically expressed mainly in the central nervous system, affect composition and formation of membrane microdomains involved in surface receptor signaling. Overexpressed in cancer, GD2 has been shown to enhance cell survival and invasion. Furthermore, binding of antibodies leads to immune-independent cell death mechanisms. In addition, GD2 contributes to T-cell dysfunction, and functions as an immune checkpoint. Given the cancer-associated functions, GD2 has been a source of interest for immunotherapy. As a potential biomarker, methods are being developed to quantify GD2 from patients' samples. In addition, various therapeutic strategies are tested. Based on initial success with antibodies, derivates such as bispecific antibodies and immunocytokines have been developed, engaging patient immune system. Cytotoxic effectors or payloads may be redirected based on anti-GD2 antibodies. Finally, vaccines can be used to mount an immune response in patients. We review here the pertinent biological information on GD2 which may be of use for optimizing current immunotherapeutic strategies.

The biological role and immunotherapy of gangliosides and GD3 synthase in cancers

Gangliosides are a large subfamily of glycosphingolipids that broadly exist in the nervous system and interact with signaling molecules in the lipid rafts. GD3 and GD2 are two types of disialogangliosides (GDs) that include two sialic acid residues. The expression of GD3 and GD2 in various cancers is mostly upregulated and is involved in tumor proliferation, invasion, metastasis, and immune responses. GD3 synthase (GD3S, ST8SiaI), a subclass of sialyltransferases, regulates the biosynthesis of GD3 and GD2. GD3S is also upregulated in most tumors and plays an important role in the development and progression of tumors. Many clinical trials targeting GD2 are ongoing and various immunotherapy studies targeting gangliosides and GD3S are gradually attracting much interest and attention. This review summarizes the function, molecular mechanisms, and ongoing clinical applications of GD3, GD2, and GD3S in abundant types of tumors, which aims to provide novel targets for future cancer therapy.

Using a combination of gangliosides and cell surface vimentin as surface biomarkers for isolating osteosarcoma cells in microfluidic devices

Background

Osteosarcoma (OS) is the most common primary bone tumor and the third leading cause of pediatric cancer deaths. Liquid biopsies are an alternative to current diagnostic imaging modalities that can be used to monitor treatment efficacy and the development of metastases. This study addresses the use of novel biomarkers to detect circulating osteosarcoma cells.

Procedures

Flow cytometry was used to evaluate the relative expression of epithelial cell adhesion molecule (EpCAM), ganglioside 2 and 3 (GD2/3), and cell surface vimentin (CSV) on a panel of OS cell lines. A microfluidic device was used to affirm the efficacy of GD2/3 and CSV to capture CTCs. Once captured, CTCs on the device are enumerated and the capture efficiency for each marker is measured. Patient samples were captured using the LFAM chip.

Results

We report the evaluation of GD2, GD3, and CSV as markers for OS cell capture in cell lines and in patient samples. The results of our capture studies correlate with our flow cytometry data and have shown a low capture efficiency of OS cells using EpCAM antibodies, while showing a moderate capture efficiency of OS cells using the GD2, GD3, and CSV antibodies independently. The combination of biomarkers demonstrate a high capture efficiency of approximately 80%. This is further supported by the detection of 1-1.5 CTCs per mL of blood using GD2 + CSV in OS patient samples.

Conclusions

The combination of GD2 + CSV significantly increased the capture efficacy of OS cells. The detection of CTCs through routine blood sampling may be used clinically for earlier detection of metastases and monitoring the therapeutic effect of treatments in metastatic osteosarcomas.

GD2-specific chimeric antigen receptor-modified T cells targeting retinoblastoma - assessing tumor and T cell interaction

A novel disialoganglioside 2 (GD2)-specific chimeric antigen receptor (CAR)-modified T cell therapy against retinoblastoma (RB) were generated. GD2-CAR consists of a single-chain variable fragment (scFv) derived from a monoclonal antibody, hu3F8, that is linked with the cytoplasmic signaling domains of CD28, 41BB, a CD3ζ, and an inducible caspase 9 death fusion partner. GD2 antigen is highly expressed in Y79RB cell line and in several surgical RB tumor specimens. In vitro co-culture experiments revealed the effective killing of Y79RB cells by GD2-CAR T cells, but not by control CD19-CAR T cells. The killing activities of GD2-CAR T cells were diminished when repeatedly exposed to the tumor, due to an attenuated expression of GD2 antigen on tumor cells and upregulation of inhibitory molecules of the PD1 and PD-L1 axis in the CAR T cells and RB tumor cells respectively. This is the first report to describe the potential of GD2-CAR T cells as a promising therapeutic strategy for RB with the indication of potential benefit of combination therapy with immune checkpoint inhibitors.

GD2-targeted chimeric antigen receptor T cells prevent metastasis formation by elimination of breast cancer stem-like cells

Expression of the disialoganglioside GD2 has been identified as a marker antigen associated with a breast cancer stem-like cell (BCSC) phenotype. Here, we report on the evaluation of GD2 as a BCSC-specific target antigen for immunotherapy. GD2 expression was confirmed at variable degree in a set of breast cancer cell lines, predominantly in triple-negative breast cancer (TNBC). To target GD2, we have generated novel anti-GD2 chimeric antigen receptors (GD2-CAR), based on single-chain variable fragments (scFv) derived from the monoclonal antibody (mAb) ch14.18, also known as dinutuximab beta. Expressed on T cells, GD2-CARs mediated specific GD2-dependent T-cell activation and target cell lysis. In contrast to previously described GD2-CARs, no signs of exhaustion by tonic signaling were found. Importantly, application of GD2-CAR expressing T cells (GD2-CAR-T) in an orthotopic xenograft model of TNBC (MDA-MB-231) halted local tumor progression and completely prevented lung metastasis formation. In line with the BCSC model, GD2 expression was only found in a subpopulation (4-6%) of MDA-MB-231 cells before injection. Significant expansion of GD2-CAR-T in tumor-bearing mice as well as T-cell infiltrates in the primary tumor and the lungs were found, indicating site-specific activation of GD2-CAR-T. Our data strongly support previous findings of GD2 as a BCSC-associated antigen. GD2-targeted immunotherapies have been extensively studied in human. In conclusion, GD2-CAR-T should be considered a promising novel approach for GD2-positive breast cancer, especially to eliminate disseminated tumor cells and prevent metastasis formation.

Ganglioside GM3 and Its Role in Cancer

Ganglioside GM3 is strongly related with human tumors, such as lung, brain cancers and melanomas, and more and more evidences have revealed that GM3 possesses powerful effects on cancer development and progression. GM3 is over expressed on several types of cancers, and can be as a tumor-associated carbohydrate antigen, used for immunotherapy of cancers. GM3 can also inhibit tumor cells growth by anti-angiogenesis or motility and so on. Especially, GM3 has effects on the EGFR tyrosine kinase signaling, uPAR-related signaling and glycolipid-enriched microdomains, which are essential for cancer signaling conduction. It is obvious that GM3 will be a promising target for cancer treatment.

Differential roles of gangliosides in malignant properties of melanomas

Ganglioside GD3 is widely expressed in human malignant melanomas, and has been reported to be involved in the increased cell proliferation and invasion. In this study, we established GM3-, GM2-, GM1-, GD3-, or GD2-expressing melanoma cell lines by transfecting cDNAs of glyscosyltransferases, and effects of individual gangliosides on the cell phenotypes and signals were examined. The phenotypes of established ganglioside-expressing cells were quite different, i.e. cell growth increased as following order; GD2+, GD3+ > GM1+, GM2+, GM3+ cells. Cell invasion activity increased as GD3+ ≧ GM2+ > GM1+, GM3+, GD2+ cells. Intensity of cell adhesion to collagen I (CL-I) and spreading increased as GD2+ >> GD3+, GM1+ > GM2+, GM3+ cells. In particular, cell adhesion of GD2+ cells was markedly strong. As for cell migration velocity, GD2+ cells were slower than all other cells. The immunocytostaining revealed close localization of gangliosides and F-actin in lamellipodia. Immunoblotting of phosphorylated p130Cas and paxillin by serum treatment reveled that these phosphorylations were more increased in GD3+ cells than in GD2+ or GM3+ cells, while phosphorylation of Akt underwent similarly increased phosphorylation between GD3+ and GD2+ cells compared with GM3+ cells. While GD2 and GD3 enhanced cell growth, GD3 might also contribute in cell invasion. On the other hand, GD2 might contribute in the solid fixation of melanoma cells at metastasized sites. These results suggested that individual gangliosides exert distinct roles in the different aspects of melanomas by differentially regulating cytoskeletons and signaling molecules.

Carbohydrate Targets for CAR T Cells in Solid Childhood Cancers

Application of the CAR targeting strategy in solid tumors is challenged by the need for adequate target antigens. As a consequence of their tissue origin, embryonal cancers can aberrantly express membrane-anchored gangliosides. These are carbohydrate molecules consisting of a glycosphingolipid linked to sialic acids residues. The best-known example is the abundant expression of ganglioside G_D2 on the cell surface of neuroblastomas which derive from G_D2-positive neuroectoderm. Gangliosides are involved in various cellular functions, including signal transduction, cell proliferation, differentiation, adhesion and cell death. In addition, transformation of human cells to cancer cells can be associated with distinct glycosylation profiles which provide advantages for tumor growth and dissemination and can serve as immune targets. Both gangliosides and aberrant glycosylation of proteins escape the direct molecular and proteomic screening strategies currently applied to identify further immune targets in cancers. Due to their highly restricted expression and their functional roles in the malignant behavior, they are attractive targets for immune engineering strategies. G_D2-redirected CAR T cells have shown activity in clinical phase I/II trials in neuroblastoma and next-generation studies are ongoing. Further carbohydrate targets for CAR T cells in preclinical development are O-acetyl-G_D2, NeuGc-GM3 (N-glycolyl GM3), G_D3, SSEA-4, and oncofetal glycosylation variants. This review summarizes knowledge on the role and function of some membrane-expressed non-protein antigens, including gangliosides and abnormal protein glycosylation patterns, and discusses their potential to serve as a CAR targets in pediatric solid cancers.

Anti-GD2/4-1BB chimeric antigen receptor T cell therapy for the treatment of Chinese melanoma patients

Background

Chimeric antigen receptor (CAR)-engineered T cells have demonstrated promising clinical efficacy in patients with B cell lymphoma. However, the application of CAR-T cell therapy in the treatment of other solid tumors has been limited. We incorporated 4-1BB into the anti-GD2 CAR-T cells to test their cytotoxicity in melanoma in vitro and in vivo. Moreover, we reported the expression of ganglioside GD2 in non-Caucasian melanoma populations for the first time, thus providing a basis for future clinical research.

Methods

This study included tumor samples from 288 melanoma patients at the Peking University Cancer Hospital & Institute. Clinical data were collected. Immunohistochemical assays using antibodies against ganglioside GD2 were performed on formalin-fixed, paraffin-embedded specimens. The ability of ganglioside GD2 CAR-T cells to kill ganglioside GD2⁺ melanoma cells was evaluated in vitro and in a patient-derived xenograft (PDX) model.

Results

Among the 288 samples, 49.3% of cases (142/288) demonstrated positive staining with ganglioside GD2. The median survival time in patients exhibiting ganglioside GD2 expression was significantly shorter than that in patients without ganglioside GD2 expression (31 vs. 47.1 months, P < 0.001). In the present study, CAR was constructed using a GD2-specific scFv (14.G2a), T cell receptor CD3ζ chain, and the CD137 (4-1BB) costimulatory motif. In addition, the GD2.BBζ CAR-T cells demonstrated specific lysis of ganglioside GD2-expressing melanoma cells in vitro. In two PDX models, mice that received intravenous or local intratumor injections of GD2.BBζ CAR-T cells experienced rapid tumor regression.

Conclusions

These data demonstrate that the rate of GD2 expression in Chinese patients is 49.3%. GD2.BBζ CAR-T cells can both efficiently lyse melanoma in a GD2-specific manner and release Th1 cytokines in an antigen-dependent manner in vitro and in vivo. Anti-GD2/4-1BB CAR-T cells represent a clinically appealing treatment strategy for Chinese melanoma patients exhibiting GD2 expression and provide a basis for future studies of the clinical application of immunotherapy for melanoma.

Electronic supplementary material

The online version of this article (10.1186/s13045-017-0548-2) contains supplementary material, which is available to authorized users.

Nanomedicine as a potent strategy in melanoma tumor microenvironment

Melanoma originated from melanocytes is the most aggressive type of skin cancer. Despite considerable progresses in clinical treatment with the discovery of BRAF or MEK inhibitors and monoclonal antibodies, the durability of response to treatment is often limited to the development of acquired resistance and systemic toxicity. The limited success of conventional treatment highlights the importance of understanding the role of melanoma tumor microenvironment in tumor developement and drug resistance. Nanoparticles represent a promising strategy for the development of new cancer treatments able to improve the bioavailability of drugs and increase their penetration by targeting specifically tumors cells and/or tumor environment. In this review, we will discuss the main influence of tumor microenvironment in melanoma growth and treatment outcome. Furthermore, third generation loaded nanotechnologies represent an exciting tool for detection, treatment, and escape from possible mechanism of resistance mediated by tumor microenvironment, and will be highlighted in this review.

Immunological Outcomes of Antibody Binding to Glycans Shared between Microorganisms and Mammals

Glycans constitute basic cellular components of living organisms across biological kingdoms, and glycan-binding Abs participate in many cellular interactions during immune defense against pathogenic organisms. Glycan epitopes are expressed as carbohydrate-only entities or as oligomers or polymers on proteins and lipids. Such epitopes on glycoproteins may be formed by posttranslational modifications or neoepitopes resulting from metabolic-catabolic processes and can be altered during inflammation. Pathogenic organisms can display host-like glycans to evade the host immune response. However, Abs to glycans, shared between microorganisms and the host, exist naturally. These Abs are able to not only protect against infectious disease, but also are involved in host housekeeping functions and can suppress allergic disease. Despite the reactivity of these Abs to glycans shared between microorganisms and host, diverse tolerance-inducing mechanisms permit the B cell precursors of these Ab-secreting cells to exist within the normal B cell repertoire.

Oncotargets GD2 and GD3 are highly expressed in sarcomas of children, adolescents, and young adults

BACKGROUND

GD2 and GD3 are the tumor-associated glycolipid antigens found in a broad spectrum of human cancers. GD2-specific antibody is currently a standard of care for high-risk neuroblastoma therapy. In this study, the pattern of GD2 and GD3 expression among pediatric/adolescent or young adult tumors was determined, providing companion diagnostics for targeted therapy.

METHODS

Ninety-two specimens of human osteosarcoma (OS), rhabdomyosarcoma (RMS), Ewing family of tumors, desmoplastic small round cell tumor (DSRCT), and melanoma were analyzed for GD2/GD3 expression by immunohistochemistry. Murine monoclonal antibody 3F8 was used for GD2 staining, and R24 for GD3. Staining was scored according to both intensity and percentage of positive tumor cells from 0 to 4.

RESULTS

Both gangliosides were highly prevalent in OS and melanoma. Among other tumors, GD3 expression was higher than GD2 expression. Most OS samples demonstrated strong staining for GD2 and GD3, whereas expression for other tumors was highly variable. Mean intensity of GD2 expression was significantly more heterogeneous (P < 0.001) when compared to GD3 across tumor types. When assessing the difference between GD2 and GD3 expression in all tumor types combined, GD3 expression had a significantly higher score (P = 0.049). When analyzed within each cancer, GD3 expression was significantly higher only in DSRCT (P = 0.002). There was no statistical difference in either GD2 or GD3 expression between primary and recurrent sarcomas.

CONCLUSION

GD2/GD3 expression among pediatric solid tumors is common, albeit with variable level of expression. Especially for patients with sarcoma, these gangliosides can be potential targets for antibody-based therapies.

Anti-proliferative and pro-apoptotic activity of GD2 ganglioside-specific monoclonal antibody 3F8 in human melanoma cells

The beneficial clinical effects of immunotherapy with GD2-specific monoclonal antibodies (mAbs) in melanoma and neuroblastoma patients have stimulated interest in characterizing the mechanisms underlying their antitumor effects. Previous studies have shown that GD2-specific mAbs mediate complement- and cell-dependent cytotoxicity and induce caspase-dependent apoptosis of tumor cells. In this study, we showed that GD2-specific mAb 3F8, which is undergoing clinical evaluation, inhibited the in vitro growth and induced apoptosis of melanoma cells. This effect was dose- and time-dependent, mediated by the interaction of mAb 3F8 combining site with GD2 ganglioside, associated with GD2 expression level on the cell surface, mAb internalization and increase of GD2 containing endosomes triggered by mAb 3F8. The induction of apoptosis by mAb 3F8 was mediated by caspase 3-, 7-, and 8-dependent pathways, downregulation of the anti-apoptotic molecules survivin and cytochrome c, and caspase 9 independent-AIF release from mitochondria. In addition, analyses of signaling pathway components demonstrated that mAb 3F8 strongly inhibited AKT and FAK activation and increased cleaved PARP expression. These results indicated that multiple mechanisms played a role in the antitumor activity of mAb 3F8 in melanoma cells. This information should provide a mechanistic basis for the optimization of the rational design of immunotherapeutic strategies in the mAb-based treatment of GD2 positive tumors.

Structural design of disialoganglioside GD2 and CD3-bispecific antibodies to redirect T cells for tumor therapy

Antibody-based immunotherapy has proven efficacy for patients with high-risk neuroblastoma. However, despite being the most efficient tumoricidal effectors, T cells are underutilized because they lack Fc receptors. Using a monovalent single-chain fragment (ScFv) platform, we engineered tandem scFv bispecific antibodies (BsAbs) that specifically target disialoganglioside (GD2) on tumor cells and CD3 on T cells. Structural variants of BsAbs were constructed and ranked based on binding to GD2, and on competency in inducing T-cell-mediated tumor cytotoxicity. In vitro thermal stability and binding measurements were used to characterize each of the constructs, and in silico molecular modeling was used to show how the orientation of the variable region heavy (VH) and light (VL) chains of the anti-GD2 ScFv could alter the conformations of key residues responsible for high affinity binding. We showed that the VH-VL orientation, the (GGGGS)3 linker, disulfide bond stabilization of scFv, when combined with an affinity matured mutation provided the most efficient BsAb to direct T cells to lyse GD2-positive tumor cells. In vivo, the optimized BsAb could efficiently inhibit melanoma and neuroblastoma xenograft growth. These findings provide preclinical validation of a structure-based method to assist in designing BsAb for T-cell-mediated therapy.

Ganglioside GD2 as a therapeutic target for antibody-mediated therapy in patients with osteosarcoma

BACKGROUND

Survival outcomes for patients with osteosarcoma have remained stagnant over the past 30 years. Targeting of ganglioside GD2, a glycosphingolipid on the cell surface of some tumors, with immunotherapy has resulted in improved outcomes for patients with neuroblastoma. In the current study, the expression pattern of GD2 was examined in osteosarcoma.

METHODS

Immunohistochemistry was performed on osteosarcoma samples from patients at the time of initial biopsy, definitive surgery, and disease recurrence. The intensity and location of staining were scored. Cell-based enzyme-linked immunoadsorbent assay was performed on osteosarcoma cell lines to quantitate the level of GD2 expression.

RESULTS

Forty-four osteosarcoma samples were evaluated by immunohistochemistry, including 8 samples from the initial biopsy, 28 samples from the definitive surgery, and 8 samples from the time of disease recurrence. GD2 was expressed on all 44 osteosarcoma samples. Osteosarcoma tissue obtained at the time of disease recurrence demonstrated a higher intensity of staining compared with samples obtained at initial biopsy and definitive surgery (P = .016). The majority of osteosarcoma cell lines expressed GD2 at higher levels than the neuroblastoma cell line BE(2)-C.

CONCLUSIONS

Ganglioside GD2 is highly expressed on osteosarcomas. Clinical trials are needed to assess the efficacy of targeting GD2 in patients with osteosarcoma.

Reassessing target antigens for adoptive T-cell therapy

Adoptive T cell therapy can target and kill widespread malignant cells thereby inducing durable clinical responses in melanoma and selected other malignances. However, many commonly targeted tumor antigens are also expressed by healthy tissues, and T cells do not distinguish between benign and malignant tissues if both express the target antigen. As such, autoimmune toxicity from T-cell-mediated destruction of normal tissue has limited the development and adoption of this otherwise promising type of cancer therapy. A review of the unique biology of T-cell therapy and of recent clinical experience compels a reassessment of target antigens that traditionally have been viewed from the perspective of weaker immunotherapeutic modalities. In selecting target antigens for adoptive T-cell therapy, expression by tumors and not by essential healthy tissues is of paramount importance. The risk of autoimmune adverse events can be further mitigated by generating antigen receptors using strategies that reduce the chance of cross-reactivity against epitopes in unintended targets. In general, a circumspect approach to target selection and thoughtful preclinical and clinical studies are pivotal to the ongoing advancement of these promising treatments.

Immunotherapy of metastatic melanoma using genetically engineered GD2-specific T cells

PURPOSE

Genetic engineering of human T lymphocytes to express tumor-directed chimeric antigen receptors (CAR) can produce antitumor effector cells that bypass tumor immune escape mechanisms that are due to abnormalities in protein-antigen processing and presentation. Moreover, these transgenic receptors can be directed to tumor-associated antigens that are not protein-derived, such as the ganglioside GD2, which is expressed in a high proportion of melanoma cells.

EXPERIMENTAL DESIGN

We generated chimeric T cells specific for the ganglioside GD2 by joining an extracellular antigen-binding domain derived from the GD2-specific antibody sc14.G2a to cytoplasmic signaling domains derived from the T-cell receptor zeta-chain, with the endodomains of the costimulatory molecules CD28 and OX40. We expressed this CAR in human T cells and assessed the targeting of GD2-positive melanoma tumors in vitro and in a murine xenograft.

RESULTS

Upon coincubation with GD2-expressing melanoma cells, CAR-GD2 T lymphocytes incorporating the CD28 and OX40 endodomains secreted significant levels of cytokines in a pattern comparable with the cytokine response obtained by engagement of the native CD3 receptor. These CAR-T cells had antimelanoma activity in vitro and in our xenograft model, increasing the survival of tumor-bearing animals.

CONCLUSION

Redirecting human T lymphocytes to the tumor-associated ganglioside GD2 generates effector cells with antimelanoma activity that should be testable in subjects with disease.

Recombinant human hexamer-dominant IgM monoclonal antibody to ganglioside GM3 for treatment of melanoma

PURPOSE

L612, a human IgM monoclonal antibody produced by an EBV-transformed human B-cell line, binds to ganglioside GM3 and kills GM3-positive human melanoma cells in the presence of complement. It has been shown to be effective in some patients with late-stage melanoma. L612 consists of hexameric IgM (about 20%), pentameric IgM (about 74%), and other minor IgM molecules. Because hexameric IgM activates complement more effectively than pentameric IgM, we developed and evaluated a hexamer-dominant recombinant IgM for clinical applications.

EXPERIMENTAL DESIGN

Chinese hamster ovary (CHO) cells were transfected with heavy- and light-chain genes of L612, with or without the joining-chain gene. Antitumor effects of the recombinant IgM secreted from CHO cells were evaluated in vitro and in vivo.

RESULTS

Recombinant IgM secreted from CHO cells without the joining chain (designated CA19) was approximately 80% hexameric, whereas recombinant IgM from CHO cells transfected with heavy-, light-, and joining-chain genes (designated CJ45) was about 90% pentameric. Both CA19 and CJ45 recombinant IgMs caused complement-dependent cytotoxicity against human and mouse melanoma cell lines, but the amount of CA19 required for 50% specific cytotoxicity was 5 to 10 times smaller. I.v. injection of CA19 compared with CJ45 or native L612 elicited more profound antitumor activity in nude rats bearing a GM3-positive mouse melanoma xenograft.

CONCLUSIONS

A hexamer-dominant human IgM against GM3 may provide a more potent treatment option for patients with GM3-positive melanoma.

Analysis of a murine anti-ganglioside GD2 monoclonal antibody expressing both IgG2a and IgG3 isotypes: monoclonality, apoptosis triggering, and activation of cellular cytotoxicity on human melanoma cells

In this study we have documented a hybridoma secreting an unusual MAb, which expresses both IgG3 and IgG2a subclasses with a lambda-light chain. How this dual expression of isotypes was exactly brought about is not clear. To resolve this problem, it will have to wait the complete sequence analysis the heavy chain gene of MAb 9C4. Although the expression of IgG2a was about 50% that of IgG3, antibody titration studies showed the major binding affinity of MAb 9C4 to GD3-positive cells being mostly contributed by the IgG3 rather than IgG2a part of the antibody. This antibody could induce apoptosis in melanoma cells in 10-15% of cells in vitro, but the generality of this phenomenon is yet to be confirmed by the use of different cell targets and different anti-GD2 MAbs other than 9C4. Aside from the demonstrated indirect killing mechanisms of many anti-GD2 MAbs through CDC and ADCC, MAb 9C4 induction of apoptosis represents an alternative mechanism of tumor cell killing, by which direct killing of anti-GD2 antibody takes its effect. This apoptotic effect was demonstrated for the first time with an anti-ganglioside monoclonal antibody. From the therapeutic point of view, the cytolytic activity of MAb 9C4-targeted ADCC/LAK killing against GD2-positive tumor cells to be more effective than that of LAK alone and a possibility for dendritic cells to effectively acquire antigen through pulsing with MAb-induced apoptotic cells are both of great clinical importance. Further studies are warranted aiming at elucidating the molecular basis of bi-isotypic specificity and aberrant isotype switching, molecular pathway of anti-GD2 antibody-induced apoptosis, and ways to improve clinical utility of this unusual hybridoma/MAb 9C4.

Culture medium induced morphological changes of melanoma cells associated with change in sensitivity to lysis by lymphokine-activated killer cells

Three sublines (Clones 1, 2 and 7) of the human melanoma CaCL 73-36 cell line with different cellular morphology, growth patterns, melanin content and surface antigenic profile were maintained in RPMI-1640 medium plus 10% fetal bovine serum (abbreviated as RPMI). Each subline was divided into two groups: one grown in RPMI and the other in Dulbecco's modified Eagle's medium plus 10% fetal bovine serum (abbreviated as DMEM) for 96 h. Phenotypically, Clone 2 expressed Class I and II MHC and ICAM-1 on the surface and in the cytoplasm, while Clones 1 and 7 failed to express these antigens in both the cytoplasm and on the cell surface. Melanotic Clones 1 and 7 cells became even more pigmented, had slower growth rates, and exhibited lower saturation densities when incubated in DMEM than when they were incubated in RPMI. On the other hand, Clone 2 cells maintained in RPMI were grossly amelanotic, contained defective-like melanosomes detected ultrastructurally, and had distinct clusters of microvilli polarly located in most of the cells. Such specialized ultrastructures were not affected by medium conditions. Analysis of sensitivity of the clonal sublines to cytolysis by allogeneic effector cells revealed that in spite of low levels of natural killer (NK) cytotoxicity noted, DMEM produced a 2- to 14-fold increase in sensitivity to NK cells, irrespective of which medium was used. Different levels of lymphokine-activated killer (LAK) cytolytic activity were clearly observed in sublines maintained in RPMI, with Clone 2 being the most sensitive and both Clones 1 and 7 being less sensitive. Cells grown in DMEM exhibited significantly higher levels of sensitivity to LAK cytolysis than cells grown in RPMI as revealed by their differences in lytic units (p < 0.05). This was likely due to the high levels of surface ICAM-1 expression in cells incubated in DMEM vs little expression of this adhesion molecule by cells grown in RPMI. Taken together, these results demonstrate the presence of heterogeneous subpopulations within the CaCL 73-36 melanoma cell line regarding their pigmentary status, antigenic profile, growth pattern and responsiveness to NK/LAK cytolysis. The results also call attention to the importance of utilizing a same medium in short- and long-term cultures of melanomas for biological studies and response evaluations of therapeutic agents such as LAK cells, when multiple cell targets from different patients or multi-metastatic cell lines from individual patients are to be compared. Finally, these melanoma sublines may be valuable for further elucidation of the relationship between MHC expression, and increased sensitivity to LAK cytolysis, and the role of the components of DMEM in the mechanism for the observed induction of cell differentiation and enhanced LAK cytolysis.

Expression of GD3 disialoganglioside antigen on peripheral T-lymphocytes in patients with disseminated malignant melanoma

Disialoganglioside antigens GD2 and GD3 are expressed on most melanoma cells. On melanoma surrounding T-cells in immunohistological sections, disialogangliosides can also be found, as well as in a small % of T-lymphocytes in peripheral blood from healthy persons. In order to find out if there is a difference in ganglioside expression on peripheral T-lymphocytes between melanoma patients and healthy persons, we examined the expression of CD3 as T-lymphocytic antigen and GD2 or GD3 antigens, respectively, by flow cytometry. We used peripheral mononuclear blood cells of 12 patients with advanced disseminated malignant melanoma and of 12 healthy control donors. For immunostaining, murine monoclonal antibodies Leu-4, 14G2a and MB3.6 were used, recognizing CD3, GD2 and GD3. GD2 expression was found on only a low proportion of T-lymphocytes in patients and healthy persons (pat.: mean = 1.2% +/- 0.7%, co.: mean = 0.4% +/- 0.4%). Disialoganglioside antigen GD3, however, could be demonstrated on an average of 8.4% +/- 4.6% of patients' and on 4.0% +/- 2.1% of healthy persons' T-cells. There is a statistically significant difference (P < 0.01) between the data of patients' and control group. We conclude that there is a correlation between advanced malignant melanoma and expression of GD3 antigen on patients' peripheral T-lymphocytes. The immunological relevance of our findings is discussed.

Expression of the co-stimulatory molecule B7 on melanoma cells

The induction of T-cell responses against tumor cells is believed to depend on both recognition of antigen and receipt of co-stimulatory signals from interaction of ligands such as B7 with its receptors CD28 or CTLA-4 on T cells. In the present study the expression of B7 on cultured human melanoma cells was studied at the mRNA level by reverse PCR analysis and surface expression by flow cytometric analysis with monoclonal antibodies (MAbs). PCR analysis revealed mRNA for B7 in 3 of 6 (50%) cultured primary melanoma and 8 of 19 (42%) cultures of metastatic melanoma. Analysis of B7 expression by flow cytometry using the BB1 MAb revealed low levels of expression in 3 of 10 melanoma that had mRNA for B7. In 2 of the latter (but not 4 other PCR+ lines) expression could be increased by culture in GM-CSF, IL-2, IFN-gamma and IFN-alpha 2. Our results indicate that although mRNA for B7 is present in 40-50% of melanoma cell lines, expression at the protein level is at low or undetectable levels in the majority of the cell lines. Expression of B7 protein was also not detected in studies on tissue sections from 11 primary and 9 metastatic melanomas.

Cellular and molecular biology of melanoma

Melanoma cells have surface markers that are expressed differently than in normal melanocytes and nevus cells. Monoclonal antibodies may define a phenotypic map of the various melanocytic lesions and can be used in immunohistopathology and immunoscintigraphy. Monoclonal antibodies directed against melanoma-associated glycoproteins and glycolipids are being tested for therapy. Rearrangements or deletions on chromosome 1, 6, and 7 are the most frequently observed cytogenetic abnormalities. Molecular studies have not given a clear picture. A subset of HRAS alleles has been reported to be associated with melanoma. NRAS activation by point mutation has been found in one fourth of the cases. Allele losses at different loci have been reported. Genetic linkage studies have given conflicting results on the presence of a gene for the melanoma-dysplastic nevus syndrome on the short arm of chromosome 1.

GD3-reactive antibodies can inhibit the lysis of autologous tumor cells by tumor-infiltrating lymphocytes

GD3 is expressed in high concentrations on melanoma cells and may serve as a useful target antigen for mAb-mediated immunotherapy. Monoclonal antibodies (mAbs) against GD3 stimulate cell-mediated immune responses against tumor cells in vitro and this activity may contribute to antitumor effects in patients with melanoma treated with GD3-reactive mAbs. In the present study the effects of GD3-reactive mAbs on autologous tumor cell lysis by a human melanoma-derived tumor-infiltrating lymphocyte (TIL) population were examined. Unlike results reported for other GD3+ T cells isolated from melanoma patients, the tumor-specific lytic activity of the TIL line was inhibited by incubation with mAbs against GD3. Other melanoma-reactive mAbs, including those against GD2 and the high-molecular-weight melanoma-associated Ag, had no effect on the TIL lytic activity. Overall, these results indicate that mAbs against GD3 may have different effects on T cell/tumor cell interactions.

Lipid modulators of epidermal proliferation and differentiation

The importance of lipids within the skin as components of the permeability barrier has been appreciated for quite some time. However, the more recent work reviewed here suggests numerous alternative bioactive functions for lipid molecules within the skin and other tissues. The precise roles of lipids in epidermal proliferation and differentiation have only begun to be studied and are far from being defined.

GD3 expression by cultured human tumor cells of neuroectodermal origin

Seven monoclonal antibodies (mAbs) reactive with ganglioside II3(NeuAc)2-LacCer (GD3) were generated; four of these mAbs (DMAb-21, DMAb-22, DMAb-23, and DMAb-24) by immunizing mice with GD3 adsorbed to Salmonella minnesota and the remaining three (DMAb-7, DMAb-8, and DMAb-17) with melanoma line SK-MEL 28, which contains 1.4 nmol sialic acid of GD3 per mg protein. The specificities of the mAbs were defined by high-performance thin-layer chromatography (HPTLC) immunostain and solid-phase radioimmunoassay (SP-RIA) with a panel of purified gangliosides. DMAb-7 and DMAb-8 reacted with GD3, IV3(NeuAc)2nLcOse4Cer(3',8'-LD1), and very weakly with IV3(NeuAc)2II3NeuAcGgOse4Cer (GT1a), but not with II3NeuAc-LacCer (GM3), II3NeuAcGgOse3Cer(GM2), II3NeuAcGgOse4Cer (GM1), II3NeuAc, IV3NeuAcGgOse4Cer (GD1a), II3(NeuAc)2GgOse3(GD2), II3(NeuAc)2GgOse4Cer (GD1b), IV3NeuAcII3(NeuAc)2, GgOse4Cer(GT1b), suggesting the binding epitope to be a terminal tetrasaccharide NeuAc alpha 2-8NeuAc alpha 2-3Gal beta 1-4(Glc or GlcNAc). DMAb-7 and DMAb-8 were used to investigate the expression of GD3 on cultured human tumor cells of neuroectodermal origin. Thirteen of 19 gliomas, 3 of 5 medulloblastomas, 5 of 5 neuroblastomas, 2 of 2 melanomas, and 1 of 3 teratomas were shown to react with DMAb-8 and/or DMAb-7 by cell surface-RIA (CS-RIA) and immunofluorescence (IF) assays. HPTLC and densitometric analysis confirmed these results, as positive immunostains in the GD3 region were obtained with oligoganglioside fractions from 9 glioma, 1 medulloblastoma, 2 neuroblastoma, 1 melanoma, and 1 teratoma cell line. Glioma cell line U-105 MG and medulloblastoma cell line Daoy contain GD3 as shown by HPTLC immunostain analysis of extracts, although GD3 was undetectable on the cell surface as determined by CS-RIA and IF.(ABSTRACT TRUNCATED AT 250 WORDS)

Preclinical and phase I studies of monoclonal antibodies in melanoma: application to boron neutron capture therapy of melanoma

Monoclonal antibodies (MAbs) provide an attractive method of selectively localizing sufficient boron atoms around tumour cells to capture neutrons. Assuming that 10(8)-10(10) 10B atoms are needed for one capture event and that 10(3)-10(4) atoms can be coupled to each antibody molecule, then 10(5)-10(6) antibody molecules gathered on an individual cell will destroy that cell. Binding to normal tissues, on the other hand, would need to be at least 20-fold less than that to tumour tissues to avoid toxic effects of neutrons on surrounding tissues. Preclinical studies in animals show that several MAbs may bind to melanoma cells in sufficient quantities in vitro to localize the required amount of Boron per cell. Whether this will occur in vivo, however, may depend not only on antigen density but a variety of other properties of the tumour cells and MAbs. These include the Ig class and affinity of the antibody and whether the antibody is internalized into the tumour cell. The ratio of uptake between tumour and normal tissue is governed by such factors as the percentage of tumour cells within a tumour expressing the antigen and whether the MAb react with normal tissues. Use of Fab or F(ab)2 preparations of the MAb may increase the uptake ratio by preventing uptake of MAb by cells with Fc receptors. In contrast to preclinical animal studies, tumour/normal tissue uptake ratios in phase I studies in humans have been disappointingly low.(ABSTRACT TRUNCATED AT 250 WORDS)

Augmentation of lymphocyte responses by monoclonal antibodies to the gangliosides GD3 and GD2: the role of protein kinase C, cyclic nucleotides, and intracellular calcium

Previous studies have shown that MAb's against the gangliosides GD3 and GD2 may augment T cell responses to a variety of stimuli. We present evidence that antiganglioside MAb's, like PHA, increase intracellular cGMP and protein kinase C yet have no effect on intracellular Ca2+. Stimulation of T cells with MAb's to GD3 was associated with increased cGMP levels, particularly in the CD8+ T cell subset which showed the highest degree of potentiation by the MAb's. Augmentation of T cell responses by the MAb's to GD3 and GD2 was also mimicked by activation of PKC with phorbol esters but both agents together produced marked synergistic effects on cell division, suggesting they had different but complementary modes of action. Furthermore, use of neomycin to inhibit PKC activation only partially reversed the augmentation of proliferative responses by the antiganglioside MAb's. It did however inhibit the MAb-induced increase in IL2 production and IL2 receptor (Tac) expression. These studies suggest therefore that the potentiation of IL2 production by the MAb's against GD2 and GD3 was due to enhanced activation of PKC whereas their augmentation of proliferative responses appeared to be due to effects on late events in T cell activation and was associated with both increased cGMP levels and activation of PKC.

Potentiation of interleukin-2 production and its binding by monoclonal antibodies to the gangliosides GD3 and GD2

Previous studies have shown that monoclonal antibodies (mAbs) against certain gangliosides, which induced remissions in patients with melanoma, also potentiated the response of lymphocytes to a variety of stimuli, including lectins, interleukin-2 (IL-2) and antigens. The present studies have investigated the mechanism of these effects on lymphocytes. Although the mAbs potentiated phytohemagglutinin(PHA)-induced IL-2 production at high concentrations of mAbs and of PHA, this did not appear to explain their potentiation of the proliferative responses of lymphocytes. Hence, although IL-2 production was minimal or absent from the CD8+ subset the latter showed the highest degree of augmentation. Furthermore, addition of IL-2 to PHA-stimulated cultures did not produce similar augmentation of mitogenic responses to that produced by the mAb to GD3 or GD2. The augmented and normal mitogenic responses were, however, dependent on IL-2, as shown by their inhibition with mAbs against IL-2. The antiganglioside mAbs did not have significant effects on IL-2 receptor expression measured by mAbs to Tac. However, the mAbs appeared to increase the affinity of binding of radiolabelled IL-2 to IL-2 receptor and increased internalization of the latter. These results suggest that the effects of the mAbs on IL-2 production may be distinguished from their effects on the proliferative responses of T cells and that the latter were associated with changes in affinity and internalization of 125I-IL-2. Whether the latter is a direct cause of the increased proliferative response remains unknown. The ability of mAbs to GD2 and GD3 to increase IL-2 production and to "enhance" IL-2-dependent proliferative responses suggests the may have valuable clinical roles as immunopotentiating agents.