Localization of the gangliosides GD2 and GD3 in adhesion plaques and on the surface of human melanoma cells

Glycosyltransferase B4GALNT1 promotes immunosuppression in hepatocellular carcinoma via the HES4-SPP1-TAM/Th2 axis

β-1,4-N-acetylgalactosaminyltransferase I (B4GALNT1) is a key glycosyltransferase for gangliosides. Its aberrant expression has been observed in various cancers, and its potential roles in tumor immunity were suggested recently. However, how B4GALNT1 regulate tumor progression and tumor immunity remains largely unknown. In this study, we aimed to investigate the roles of B4GALNT1 in hepatocellular carcinoma (HCC), particularly in reshaping the tumor immune microenvironment, and evaluate the potential beneficial effects of targeting B4GALNT1 in immunotherapy. Our data verified the aberrant upregulation of B4GALNT1 in HCC tumor tissues and tumor cells, which could be utilized as an independent prognostic factor and improve the predicting performance of traditional tumor node metastasis (TNM) system. We also demonstrated that B4GALNT1 increased the phosphorylation of Hes Family BHLH Transcription Factor 4 (HES4) via p38 mitogen-activated protein kinase (p38)/ c-Jun N-terminal kinase (JNK) signaling in tumor cells, thus increasing the transcriptional activity of HES4, which upregulated the synthesis and secretion of secreted phosphoprotein 1 (SPP1), modulated the composition of tumor-associated macrophages (TAMs) and T helper type 2 (Th2) cells, and eventually reshaped the immunosuppressive microenvironment. In addition, silencing B4GALNT1 was proved to enhance the tumor-killing efficiency of the programmed cell death protein 1 (PD-1)-targeting strategy in mouse model. In conclusion, this study evaluated B4GALNT1 as a prognostic predictor for HCC patients and revealed the mechanism of B4GALNT1 in microenvironmental remodeling, which extends the understanding of HCC progression and provides a novel auxiliary strategy for HCC immunotherapy.

Action Mechanisms of Exosomes Derived from GD3/GD2-Positive Glioma Cells in the Regulation of Phenotypes and Intracellular Signaling: Roles of Integrins

Extracellular vesicles (EVs) play important roles in intercellular communication in various biological events. In particular, EVs released from cancer cells have attracted special attention. Although it has been reported that cancer-associated glycosphingolipids play important roles in the enhancement of malignant properties of cancer cells, the presence, behavior, and roles of glycosphingolipids in EVs have not been elucidated. Recently, we reported crucial roles of EVs expressing gangliosides, GD2, and/or GD3 in the enhancement of cancer properties in malignant melanomas and gliomas. However, how EVs containing cancer-associated glycosphingolipids play their roles has not been reported to date. Here, we studied spatio-temporal mechanisms for GD3/GD2-containing EVs released from gliomas in the actions toward target cells. Proteome analyses of EVs with/without GD3/GD2 revealed an equally high concentration of integrin isoforms in both GD3/GD2+ and GD3/GD2- EVs. PKH26-labeled EVs attached, invaded, and distributed to/in the target cells within 1 h. GD3/GD2 formed molecular complexes with integrins on EVs as elucidated by immunoprecipitation/immunoblotting and immunocytostaining. The addition of antibodies reactive with GD3, GD2, or integrins resulted in the suppression of the enhancing effects of EVs in the cell adhesion assay. The addition of GD3/GD2 + EVs to GD3/GD2- cells clearly increased the phosphorylation levels of the PDGF receptor, FAK, and Erk1/2 in immunoblotting, suggesting GD3/GD2+ EVs activate the signaling pathway in the target cells within 15 min after addition. Anti-ganglioside antibodies clearly blocked signaling with EVs. In conclusion, EVs released from GD3/GD2-expressing glioma cells enhance cancer phenotypes and malignant signals via the cluster formation of integrins and GD3/GD2 on EVs, leading to the regulation of the cancer microenvironment.

A Chitosan Scaffold Supports the Enhanced and Prolonged Differentiation of HiPSCs into Nucleus Pulposus-like Cells

Intervertebral disc degeneration (IDD) is a progressive condition and stands as one of the primary causes of low back pain. Cell therapy that uses nucleus pulposus (NP)-like cells derived from human induced pluripotent stem cells (hiPSCs) holds great promise as a treatment for IDD. However, the conventional two-dimensional (2D) monolayer cultures oversimplify cell-cell interactions, leading to suboptimal differentiation efficiency and potential loss of phenotype. While three-dimensional (3D) culture systems like Matrigel improve hiPSC differentiation efficiency, they are limited by animal-derived materials for translation, poorly defined composition, short-term degradation, and high cost. In this study, we introduce a new 3D scaffold fabricated using medical-grade chitosan with a high degree of deacetylation. The scaffold features a highly interconnected porous structure, near-neutral surface charge, and exceptional degradation stability, benefiting iPSC adhesion and proliferation. This scaffold remarkably enhances the differentiation efficiency and allows uninterrupted differentiation for up to 25 days without subculturing. Notably, cells differentiated on the chitosan scaffold exhibited increased cell survival rates and upregulated gene expression associated with extracellular matrix secretion under a chemically defined condition mimicking the challenging microenvironment of intervertebral discs. These characteristics qualify the chitosan scaffold-cell construct for direct implantation, serving as both a structural support and a cellular source for enhanced stem cell therapy for IDD.

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.

Extracellular vesicles released from ganglioside GD2-expressing melanoma cells enhance the malignant properties of GD2-negative melanomas

Exosomes (small extracellular vesicles: EVs) have attracted increasing attention from basic scientists and clinicians since they play important roles in cell-to-cell communication in various biological processes. Various features of EVs have been elucidated regarding their contents, generation and secretion mechanisms, and functions in inflammation, regeneration, and cancers. These vesicles are reported to contain proteins, RNAs, microRNAs, DNAs, and lipids. Although the roles of individual components have been rigorously studied, the presence and roles of glycans in EVs have rarely been reported. In particular, glycosphingolipids in EVs have not been investigated to date. In this study, the expression and function of a representative cancer-associated ganglioside, GD2, in malignant melanomas was investigated. Generally, cancer-associated gangliosides have been shown to enhance malignant properties and signals in cancers. Notably, EVs derived from GD2-expressing melanomas enhanced the malignant phenotypes of GD2-negative melanomas, such as cell growth, invasion, and cell adhesion, in a dose-dependent manner. The EVs also induced increased phosphorylation of signaling molecules such as EGF receptor and focal adhesion kinase. These results suggest that EVs released from cancer-associated ganglioside-expressing cells exert many functions that have been reported as a function of these gangliosides and regulate microenvironments, including total aggravation of heterogeneous cancer tissues, leading to more malignant and advanced cancer types.

Emerging phagocytosis checkpoints in cancer immunotherapy

Cancer immunotherapy, mainly including immune checkpoints-targeted therapy and the adoptive transfer of engineered immune cells, has revolutionized the oncology landscape as it utilizes patients' own immune systems in combating the cancer cells. Cancer cells escape immune surveillance by hijacking the corresponding inhibitory pathways via overexpressing checkpoint genes. Phagocytosis checkpoints, such as CD47, CD24, MHC-I, PD-L1, STC-1 and GD2, have emerged as essential checkpoints for cancer immunotherapy by functioning as "don't eat me" signals or interacting with "eat me" signals to suppress immune responses. Phagocytosis checkpoints link innate immunity and adaptive immunity in cancer immunotherapy. Genetic ablation of these phagocytosis checkpoints, as well as blockade of their signaling pathways, robustly augments phagocytosis and reduces tumor size. Among all phagocytosis checkpoints, CD47 is the most thoroughly studied and has emerged as a rising star among targets for cancer treatment. CD47-targeting antibodies and inhibitors have been investigated in various preclinical and clinical trials. However, anemia and thrombocytopenia appear to be formidable challenges since CD47 is ubiquitously expressed on erythrocytes. Here, we review the reported phagocytosis checkpoints by discussing their mechanisms and functions in cancer immunotherapy, highlight clinical progress in targeting these checkpoints and discuss challenges and potential solutions to smooth the way for combination immunotherapeutic strategies that involve both innate and adaptive immune responses.

Ganglioside GD2 Enhances the Malignant Phenotypes of Melanoma Cells by Cooperating with Integrins

Gangliosides have been considered to modulate cell signals in the microdomain of the cell membrane, lipid/rafts, or glycolipid-enriched microdomain/rafts (GEM/rafts). In particular, cancer-associated gangliosides were reported to enhance the malignant properties of cancer cells. In fact, GD2-positive (GD2+) cells showed increased proliferation, invasion, and adhesion, compared with GD2-negative (GD2-) cells. However, the precise mechanisms by which gangliosides regulate cell signaling in GEM/rafts are not well understood. In order to analyze the roles of ganglioside GD2 in the malignant properties of melanoma cells, we searched for GD2-associating molecules on the cell membrane using the enzyme-mediated activation of radical sources combined with mass spectrometry, and integrin β1 was identified as a representative GD2-associating molecule. Then, we showed the physical association of GD2 and integrin β1 by immunoprecipitation/immunoblotting. Close localization was also shown by immuno-cytostaining and the proximity ligation assay. During cell adhesion, GD2+ cells showed multiple phospho-tyrosine bands, i.e., the epithelial growth factor receptor and focal adhesion kinase. The knockdown of integrin β1 revealed that the increased malignant phenotypes in GD2+ cells were clearly cancelled. Furthermore, the phosphor-tyrosine bands detected during the adhesion of GD2+ cells almost completely disappeared after the knockdown of integrin β1. Finally, immunoblotting to examine the intracellular distribution of integrins during cell adhesion revealed that large amounts of integrin β1 were localized in GEM/raft fractions in GD2+ cells before and just after cell adhesion, with the majority being localized in the non-raft fractions in GD2- cells. All these results suggest that GD2 and integrin β1 cooperate in GEM/rafts, leading to enhanced malignant phenotypes of melanomas.

Targeting glycosphingolipids for cancer immunotherapy

Aberrant expression of glycosphingolipids (GSLs) is a unique feature of cancer and stromal cells in tumor microenvironments. Although the impact of GSLs on tumor progression remains largely unclear, anticancer immunotherapies directed against GSLs are attracting growing attention. Here, we focus on GD2, a disialoganglioside expressed in tumors of neuroectodermal origin, and Globo H ceramide (GHCer), the most prevalent cancer-associated GSL overexpressed in a variety of epithelial cancers. We first summarize recent advances on our understanding of GD2 and GHCer biology and then discuss the clinical development of the first immunotherapeutic agent targeting a glycolipid, the GD2-specific antibody dinutuximab, its approved indications, and new strategies to improve its efficacy for neuroblastoma. Next, we review ongoing clinical trials on Globo H-targeted immunotherapeutics. We end with highlighting how these studies provide sound scientific rationales for targeting GSLs in cancer and may facilitate a rational design of new GSL-targeted anticancer therapeutics.

Mechanosensitivity Occurs along the Adhesome's Force Train and Affects Traction Stress

Herein, we consider the process of force development along the adhesome within cell focal adhesions. Our model adhesome consists of the actin cytoskeleton-vinculin-talin-integrin-ligand-extracellular matrix-substrate force train. We specifically consider the effects of substrate stiffness on the force levels expected along the train and on the traction stresses they create at the substrate. We find that significant effects of substrate stiffness are manifest within each constitutive component of the force train and on the density and distribution of integrin/ligand anchorage points with the substrate. By following each component of the force train, we are able to delineate specific gaps in the quantitative descriptions of bond survival that must be addressed so that improved quantitative forecasts become possible. Our analysis provides, however, a rational description for the various levels of traction stresses that have been reported and of the effect of substrate stiffness. Our approach has the advantage of being quite clear as to how each constituent contributes to the net development of force and traction stress. We demonstrate that to provide truly quantitative forecasts for traction stress, a far more detailed description of integrin/ligand density and distribution is required. Although integrin density is already a well-recognized important feature of adhesion, our analysis places a finer point on it in the manner of how we evaluate the magnitude of traction stress. We provide mechanistic insight into how understanding of this vital element of the adhesion process may proceed by addressing mechanistic causes of integrin clustering that may lead to patterning.

Enhanced Ordering in Monolayers Containing Glycosphingolipids: Impact of Carbohydrate Structure

The influence of carbohydrate structure on the ordering of glycosphingolipids (GSLs) and surrounding phospholipids was investigated in monolayers at the air-water interface. Binary mixtures composed of GSLs, chosen to span a range of carbohydrate complexity, and zwitterionic dipalmitoylphosphatidylcholine phospholipid, were studied. X-ray reflectivity was used to measure the out-of-plane structure of the monolayers and characterize the extension and conformation of the GSL carbohydrates. Using synchrotron grazing incidence x-ray diffraction, the in-plane packing of the lipid acyl chains and the area per molecule within ordered domains were characterized at different mole ratios of the two components. Our findings indicate that GSL-containing mixtures, regardless of the carbohydrate size, enhance the ordering of the surrounding lipids, resulting in a larger fraction of ordered phase of the monolayer and greater dimensions of the ordered domains. Reduction of the averaged area per molecule within the ordered domains was also observed but only in the cases where there was a size mismatch between the phospholipid headgroups and GSL components, suggesting that the condensation mechanism involves the relief of steric interactions between headgroups in mixtures.

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.

GD3 ganglioside-enriched extracellular vesicles stimulate melanocyte migration

Melanomas often accumulate gangliosides, sialic acid-containing glycosphingolipids found in the outer leaflet of plasma membranes, as disialoganglioside G_D3 and its derivatives. Here, we have transfected the G_D3 synthase gene (ST8Sia I) in a normal melanocyte cell line in order to evaluate changes in the biological behavior of non-transformed cells. G_D3-synthase expressing cells converted G_M3 into G_D3 and accumulated both G_D3 and its acetylated form, 9-O-acetyl-G_D3. Melanocytes were rendered more migratory on laminin-1 surfaces. Cell migration studies using the different transfectants, either treated or not with the glucosylceramide synthase inhibitor d-1-threo-1-phenyl-2-palmitoylamino-3-pyrrolidino-1-propanol (PPPP), allowed us to show that while G_M3 is a negative regulator of melanocyte migration, G_D3 increases it. We showed that gangliosides were shed to the matrix by migrating cells and that G_D3 synthase transfected cells shed extracellular vesicles (EVs) enriched in G_D3. EVs enriched in G_D3 stimulated cell migration of G_D3 negative cells, as observed in time lapse microscopy studies. Otherwise, EVs shed by G_M3^+veG_D3^-ve cells impaired migration and diminished cell velocity in cells overexpressing G_D3. The balance of antimigratory G_M3 and promigratory G_D3 gangliosides in melanocytes could be altered not only by the overexpression of enzymes such as ST8Sia I, but also by the horizontal transfer of ganglioside enriched extracellular vesicles. This study highlights that extracellular vesicles transfer biological information also through their membrane components, which include a variety of glycosphingolipids remodeled in disease states such as cancer.

Glycosphingolipid dynamics in human embryonic stem cell and cancer: their characterization and biomedical implications

Glycosphingolipids (GSLs) are composed of complex glycans linked to sphingosines and various fatty acid chains. Antibodies against several GSLs designated as stage-specific embryonic antigens (SSEAs), have been widely used to characterize differentiation of embryonic stem (ES) cells. In view of the cross-reactivities of these antibodies with multiple glycans, a few laboratories have employed advanced mass spectrometry (MS) technologies to define the dynamic changes of surface GSLs upon ES differentiation. However, the amphiphilic nature and heterogeneity of GSLs make them difficult to decipher. In our studies, systematic survey of GSL expression profiles in human ES cells and differentiated derivatives was conducted, primarily with matrix-assisted laser desorption/ionization MS (MALDI-MS) and MS/MS analyses. In addition to the well-known ES-specific markers, SSEA-3 and SSEA-4, several previously undisclosed globo- and lacto-series GSLs, including Gb4Cer, Lc4Cer, fucosyl Lc4Cer, Globo H, and disialyl Gb5Cer were identified in the undifferentiated human ES and induced pluripotent stem cells. Furthermore, during differentiation to embryoid body outgrowth, the core structures of GSLs switched from globo- and lacto- to ganglio-series. Lineage-specific differentiation was also marked by alterations of specific GSLs. During differentiation into neural progenitors, core structures shifted to primarily ganglio-series dominated by GD3. GSL patterns shifted to prominent expression of Gb4Cer with little SSEA-3 and- 4 or GD3 during endodermal differentiation. Several issues relevant to MS analysis and novel GSLs in ES cells were discussed. Finally, unique GSL signatures in ES and cancer cells are exploited in glycan-targeted anti-cancer immunotherapy and their mechanistic investigations were discussed using anti-GD2 mAb and Globo H as examples.

Number of sialic acid residues in ganglioside headgroup affects interactions with neighboring lipids

Monolayers of binary mixtures of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and asialo-(GA1), disialo-(GD1b) and trisialo-(GT1b) gangliosides were used to determine the effect of ganglioside headgroup charge and geometry on its interactions with the neighboring zwitterionic lipid. Surface pressure versus molecular area isotherm measurements along with concurrent fluorescence microscopy of the monolayers at the air-water interface were complemented with atomic force microscopy imaging of monolayers deposited on solid substrates. Results were used to further develop a proposed geometric packing model that the complementary geometry of DPPC and monosialoganglioside GM1 headgroups affects their close molecular packing, inducing condensation of the layer at small mol % of ganglioside. For GA1, GD1b, and GT1b, a similar condensing effect, followed by a fluidizing effect is seen that varies with glycosphingolipid concentration, but results do not directly follow from geometric arguments because less DPPC is needed to condense ganglioside molecules with larger cross-sectional areas. The variations in critical packing mole ratios can be explained by global effects of headgroup charge and resultant dipole moments within the monolayer. Atomic force microscopy micrographs further support the model of ganglioside-induced DPPC condensation with condensed domains composed of a striped phase of condensed DPPC and DPPC/ganglioside geometrically packed complexes at low concentrations.

Re-configuration of sphingolipid metabolism by oncogenic transformation

The sphingolipids are one of the major lipid families in eukaryotes, incorporating a diverse array of structural variants that exert a powerful influence over cell fate and physiology. Increased expression of sphingosine kinase 1 (SPHK1), which catalyses the synthesis of the pro-survival, pro-angiogenic metabolite sphingosine 1-phosphate (S1P), is well established as a hallmark of multiple cancers. Metabolic alterations that reduce levels of the pro-apoptotic lipid ceramide, particularly its glucosylation by glucosylceramide synthase (GCS), have frequently been associated with cancer drug resistance. However, the simple notion that the balance between ceramide and S1P, often referred to as the sphingolipid rheostat, dictates cell survival contrasts with recent studies showing that highly potent and selective SPHK1 inhibitors do not affect cancer cell proliferation or survival, and studies demonstrating higher ceramide levels in some metastatic cancers. Recent reports have implicated other sphingolipid metabolic enzymes such as acid sphingomyelinase (ASM) more strongly in cancer pathogenesis, and highlight lysosomal sphingolipid metabolism as a possible weak point for therapeutic targeting in cancer. This review describes the evidence implicating different sphingolipid metabolic enzymes and their products in cancer pathogenesis, and suggests how newer systems-level approaches may improve our overall understanding of how oncogenic transformation reconfigures sphingolipid metabolism.

Ganglioside influence on phospholipid films investigated with single molecule fluorescence measurements

Single molecule fluorescence measurements are used to probe the effects of GM1 in DPPC monolayers. Langmuir-Blodgett films of GM1 and DPPC were doped with ~10(-8) mol % of the fluorescent lipid probe, BODIPY-PC, and transferred onto glass substrates at 23 mN/m. As shown previously, the individual orientation of each BODIPY-PC probe in the membrane can be measured using defocused polarized total internal reflection fluorescence microscopy, revealing changes in film properties at the molecular level. Here, BODIPY-PC tilt angle histograms are used to characterize the effects of GM1 in DPPC films from 0.05 to 100 mol % GM1. At high GM1 levels (>5 mol % GM1), trends in the single molecule measurements agree with previous bulk measurements showing the turnover from condensing to expanding influence of GM1 at 15-20 mol %, thus validating the single molecule approach. At biologically relevant, low concentrations of GM1 (<5 mol % GM1), where bulk fluorescence measurements are less informative, the single molecule measurements reveal a marked influence of GM1 on film properties. The addition of trace amounts of GM1 to DPPC films leads to an expansion of the film which continues to 0.10 mol % GM1, above which the trend reverses and the condensing effect previously noted is observed.

64Cu-p-NH2-Bn-DOTA-hu14.18K322A, a PET radiotracer targeting neuroblastoma and melanoma

The hu14.18K322A variant of the GD2-targeting antibody hu14.18 has been shown to elicit a level of antibody-dependent cell-mediated cytotoxicity toward human neuroblastoma cells similar to that of the parent antibody. However, hu14.18K322A exhibited a decreased complement activation and associated pain, the dose-limiting toxicity in neuroblastoma immunotherapy. PET with a radiolabeled analog of the same antibody used in treatment will provide insight into the ability of hu14.18K322A to reach its target, as well as nontarget uptake that may cause side effects. Such antibody radiotracers might also provide a method for measuring GD2 expression in tumors, thus enabling the prediction of response to anti-GD2 therapy for individual patients.

METHODS

The conjugation of hu14.18K322A with p-NH(2)-Bn-DOTA was accomplished using N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide with subsequent (64)Cu radiolabeling at 37°C for 30 min. Immunoreactivity of the conjugate was assessed by a dose-escalation blocking experiment measuring binding to purified GD2 versus GD1b as a negative control. Cell uptake and biodistribution studies in M21 (GD2-positive) and PC-3 (GD2-negative) tumor models were performed, as was small-animal PET/CT of M21 and PC-3 tumor-bearing mice.

RESULTS

The labeling of (64)Cu-p-NH(2)-Bn-DOTA-hu14.18K322A was achieved at more than 95% radiochemical purity and a specific activity of 127-370 MBq/mg (3.4-10 mCi/mg) after chromatographic purification. Preliminary in vitro data demonstrated a greater than 6-fold selectivity of binding to GD2 versus GD1b and dose-dependent inhibition of binding by unmodified hu14.8K322A. In vivo data, including small-animal PET/CT, showed significant GD2-positive tumor-targeting ability, with a persistent 2-fold-higher uptake of radiotracer than in GD2-negative tumors.

CONCLUSION

(64)Cu-p-NH(2)-Bn-DOTA-hu14.18K322A represents a novel PET radiotracer to facilitate clinical investigations of anti-GD2 immunotherapies and to complement other imaging modalities in the staging and treatment of neuroblastoma.

Fine specificity and cross-reactions of monoclonal antibodies to group B streptococcal capsular polysaccharide type III

Group B streptococcus (GBS) is a major cause of neonatal sepsis and meningitis. Despite aggressive campaigns using antenatal prophylactic antibiotic therapy, infections continue. Developing an effective maternal vaccine is a public health priority. Antibody (Ab) to the capsular polysaccharide (CPS) is considered the dominant "protective" immune mediator. Here we study the fine specificity and potential host reactivity of a panel of well-characterized murine monoclonal Abs against the type III CPS by examining the binding of the Abs to intact and neuraminidase-digested GBS, purified CPS, synthetic carbohydrate structures, and cells. The results showed marked differences in the fine specificity among these mAbs to a single carbohydrate structure. Cross-reactions with synthetic GD3 and GT3 carbohydrates, representing structures found on surfaces of neural and developing cells, were demonstrated using carbohydrate array technology. The anti-CPS(III) mAbs did not react with cells expressing GD3 and GT3, nor did mAbs specific for the host carbohydrates cross-react with GBS, raising questions about the physiological relevance of this cross-reaction. But in the process of these investigations, we serendipitously demonstrated cross-reactions of some anti-CPS(III) mAbs with antigens, likely carbohydrates, found on human leukocytes. These studies suggest caution in the development of a maternal vaccine to prevent infection by this important human pathogen.

Neuroblastoma-targeted nanoparticles entrapping siRNA specifically knockdown ALK

RNA interference molecules have some advantages as cancer therapeutics, including a proved efficacy on both wild-type (WT) and mutated transcripts and an extremely high sequence-specificity. The most significant hurdle to be overcome if exogenous small interfering RNAs (siRNA) is to be used therapeutically is the specific, effective, nontoxic delivery of siRNA to its intracellular site of action. At present, human applications are confined almost exclusively to targets within the liver, where the delivery systems naturally accumulate, and extra-hepatic targets remain a challenge. Anaplastic lymphoma kinase (ALK) is a receptor tyrosine kinase that has recently been shown to contribute to the cell growth and progression of human neuroblastoma (NB). We investigated its potential as a therapeutic target in NB by generating anti-GD₂-targeted nanoparticles that carry ALK-directed siRNA, which are specifically and efficiently delivered to GD₂-expressing NB cells. Relative to free ALK-siRNA, anti-GD₂-targeted liposomal formulations of ALK-siRNA had low plasma clearance, increased siRNA stability, and improved binding, uptake, silencing and induction of cell death, and specificity for NB cells. In NB xenografts, intravenous (i.v.) injection of the targeted ALK-siRNA liposomes showed gene-specific antitumor activity with no side effects. ALK-selective siRNA entrapped in anti-GD₂-targeted nanoparticles is a promising new modality for NB treatment.

Cancer vaccine with mimotopes of tumor-associated carbohydrate antigens

The GD2 ganglioside, displayed by five carbohydrate Neu5Acalpha2-8Neu5Acalpha2-3(GalNAcbeta1-4)Galbeta1-4Glcbeta residues attached to a ceramide chain that anchors the ganglioside in the cell membrane, is expressed on neuroectodermally derived tumors. GD2 has been used as a target for passive and active immunotherapy in patients with malignant melanoma and neuroblastoma. We have generated 47-LDA mimotope of GD2 by screening a phage display peptide library with anti-GD2 mAb 14G2a and reported that vaccination with the 47-LDA mimotope elicited GD2 cross-reactive IgG antibody responses as well as MHC class I-restricted CD8(+) T cells to syngeneic neuroblastoma tumor cells. The cytotoxic activity of the vaccine-induced CTLs was independent of GD2 expression, suggesting recognition of a novel tumor-associated antigen cross-reacting with 47-LDA. Immunoblotting studies using 14G2a mAb demonstrated that this antibody cross-reacts with a 105 kDa glycoprotein expressed by GD2(+) and GD2(-) neuroblastoma and melanoma cells. Functional studies of tumor cells grown in three-dimensional (3D) collagen cultures with 14G2a mAb showed decreases in matrix metalloproteinase-2 activation, a process regulated by 105 kDa activated leukocyte cell adhesion molecules (ALCAM/CD166). The CD166 glycoprotein was shown to be recognized by 14G2a antibody, and inhibition of CD166 expression by RNA interference ablated the cell sensitivity to lysis by 47-LDA-induced CD8(+) T cells in vitro and in vivo. These results suggest that the vaccine-induced CTLs recognize a 47-LDA cross-reactive epitope expressed by CD166 and reveal a novel mechanism of induction of potent tumor-specific cellular responses by mimotopes of tumor-associated carbohydrate antigens.

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.

RESEARCH ADVANCES IN NEUROBLASTOMA IMMUNOTHERAPY

Neuroblastoma is the third most common pediatric cancer in the United States and is responsible for 15% of pediatric cancer-related deaths. Despite major advances in multimodal therapy, the clinical outcome for several patients remains poor. Due to the desperate need for innovativation and improved success in the treatment and management of neuroblastoma, research interests in immunotherapy have been on the rise in recent years. Current immunotherapeutic approaches under investigation include antibodies targeting the neuroblastoma antigen GD2, cytokine stimulation of immune cells, use of immunocytokine conjugates, radioimmunotherapy, and tumor-primed dendritic cells. Immunotherapy could serve as a safe alternative or adjunct to current therapeutic protocols and would presumptively have fewer deleterious effects making it more favorable to patients.

Immunization with a mimotope of GD2 ganglioside induces CD8+ T cells that recognize cell adhesion molecules on tumor cells

The GD2 ganglioside expressed on neuroectodermal tumor cells has been used as a target for passive and active immunotherapy in patients with malignant melanoma and neuroblastoma. We have reported that immunization of mice with a 47-LDA mimotope of GD2, isolated from a phage display peptide library with anti-GD2 mAb 14G2a, induces MHC class I-restricted CD8(+) T cell responses to syngeneic neuroblastoma tumor cells. The cytotoxic activity of the vaccine-induced CTLs was independent of GD2 expression, suggesting recognition of a novel tumor-associated Ag cross-reacting with 47-LDA. Glycan microarray and immunoblotting studies using 14G2a mAb demonstrated that this Ab is highly specific for the entire carbohydrate motif of GD2 but also cross-reacts with a 105 kDa glycoprotein expressed by GD2(+) and GD2(-) neuroblastoma and melanoma cells. Functional studies of tumor cells grown in three-dimensional collagen cultures with 14G2a mAb showed decreases in matrix metalloproteinase-2 activation, a process regulated by the 105 kDa-activated leukocyte cell adhesion molecule (ALCAM/CD166). A recombinant CD166 glycoprotein was shown to be recognized by 14G2a Ab and inhibition of CD166 expression by RNA interference ablated the cell sensitivity to lysis by 47-LDA-induced CD8(+) T cells in vitro and in vivo. The binding of 14G2a to CD166 was not disruptable by a variety of exo- and endo-glycosidases, implying recognition of a non-glycan epitope on CD166. These results suggest that the vaccine-induced CTLs recognize a 47-LDA cross-reactive epitope expressed by CD166, and reveal a novel mechanism of induction of potent tumor-specific cellular responses by mimotopes of tumor-associated carbohydrate Ags.

Electrochemical and PM-IRRAS a glycolipid-containing biomimetic membrane prepared using Langmuir-Blodgett/Langmuir-Schaefer deposition

Differential capacitance, chronocoulometry, and polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS) measurements were used to characterize the structure and orientation of a DMPC + cholesterol + GM 1 (60:30:10 mol %) bilayer supported at a Au(111) electrode surface prepared using combined Langmuir-Blodgett/Langmuir-Schaefer (LB/LS) deposition. The electrochemical measurements indicate that the incorporation of ganglioside GM 1 into the membrane significantly improves the quality of the bilayer, reflected in the very low capacitance value of approximately 0.8 microF cm (-2). An analysis of the infrared data suggests that the incorporation of the glycolipid into the membrane changes both the orientation of the lipid acyl chains in the membrane and the hydration of the membrane, particularly with respect to the interfacial region of the lipids.

A phase I clinical study of vaccination of melanoma patients with dendritic cells loaded with allogeneic apoptotic/necrotic melanoma cells. Analysis of toxicity and immune response to the vaccine and of IL-10 -1082 promoter genotype as predictor of disease progression

BACKGROUND

Sixteen melanoma patients (1 stage IIC, 8 stage III, and 7 stage IV) were treated in a Phase I study with a vaccine (DC/Apo-Nec) composed of autologous dendritic cells (DCs) loaded with a mixture of apoptotic/necrotic allogeneic melanoma cell lines (Apo-Nec), to evaluate toxicity and immune responses. Also, IL-10 1082 genotype was analyzed in an effort to predict disease progression.

METHODS

PBMC were obtained after leukapheresis and DCs were generated from monocytes cultured in the presence of GM-CSF and IL-4 in serum-free medium. Immature DCs were loaded with gamma-irradiated Apo-Nec cells and injected id without adjuvant. Cohorts of four patients were given four vaccines each with 5, 10, 15, or 20 x 106 DC/Apo-Nec cell per vaccine, two weeks apart. Immune responses were measured by ELISpot and tetramer analysis. Il-10 genotype was measured by PCR and corroborated by IL-10 production by stimulated PBMC.

RESULTS

Immature DCs efficiently phagocytosed melanoma Apo-Nec cells and matured after phagocytosis as evidenced by increased expression of CD83, CD80, CD86, HLA class I and II, and 75.2 +/- 16% reduction in Dextran-FITC endocytosis. CCR7 was also up-regulated upon Apo-Nec uptake in DCs from all patients, and accordingly DC/Apo-Nec cells were able to migrate in vitro toward MIP-3 beta. The vaccine was well tolerated in all patients. The DTH score increased significantly in all patients after the first vaccination (Mann-Whitney Test, p < 0.05). The presence of CD8+T lymphocytes specific to gp100 and Melan A/MART-1 Ags was determined by ELISpot and tetramer analysis in five HLA-A*0201 patients before and after vaccination; one patient had stable elevated levels before and after vaccination; two increased their CD8 + levels, one had stable moderate and one had negligible levels. The analysis of IL-10 promoter -1082 polymorphism in the sixteen patients showed a positive correlation between AA genotype, accompanied by lower in vitro IL-10 production by stimulated PBMC, and faster melanoma progression after lymph nodes surgery (p = 0.04). With a mean follow-up of 49.5 months post-surgery, one stage IIC patient and 7/8 stage III patients remain NED but 7/7 stage IV patients have progressed.

CONCLUSION

We conclude that DC/Apo-Nec vaccine is safe, well tolerated and it may induce specific immunity against melanoma Ags. Patients with a low-producing IL-10 polymorphism appear to have a worst prognosis.

TRIAL REGISTRATION

Clinicaltrials.gov (NHI) NCT00515983.

Condensing and fluidizing effects of ganglioside GM1 on phospholipid films

Mixed monolayers of the ganglioside G(M1) and the lipid dipalmitoylphosphatidlycholine (DPPC) at air-water and solid-air interfaces were investigated using various biophysical techniques to ascertain the location and phase behavior of the ganglioside molecules in a mixed membrane. The effects induced by G(M1) on the mean molecular area of the binary mixtures and the phase behavior of DPPC were followed for G(M1) concentrations ranging from 5 to 70 mol %. Surface pressure isotherms and fluorescence microscopy imaging of domain formation indicate that at low concentrations of G(M1) (<25 mol %), the monolayer becomes continually more condensed than DPPC upon further addition of ganglioside. At higher G(M1) concentrations (>25 mol %), the mixed monolayer becomes more expanded or fluid-like. After deposition onto a solid substrate, atomic force microscopy imaging of these lipid monolayers showed that G(M1) and DPPC pack cooperatively in the condensed phase domain to form geometrically packed complexes that are more ordered than either individual component as evidenced by a more extended total height of the complex arising from a well-packed hydrocarbon tail region. Grazing incidence x-ray diffraction on the DPPC/G(M1) binary mixture provides evidence that ordering can emerge when two otherwise fluid components are mixed together. The addition of G(M1) to DPPC gives rise to a unit cell that differs from that of a pure DPPC monolayer. To determine the region of the G(M1) molecule that interacts with the DPPC molecule and causes condensation and subsequent expansion of the monolayer, surface pressure isotherms were obtained with molecules modeling the backbone or headgroup portions of the G(M1) molecule. The observed concentration-dependent condensing and fluidizing effects are specific to the rigid, sugar headgroup portion of the G(M1) molecule.

Shed gangliosides provide detergent-independent evidence for Type-3 glycosynapses

Membrane microdomains, or rafts, at the plasma membrane have been invoked to explain many cellular processes. Protein-protein interactions within such microdomains including, for example, the tetraspanin web are reported to provide a scaffold for signal transduction. However, the nature of such protein-protein interactions is not fully elucidated. Hakomori [S.I. Hakomori, The glycosynapse, Proc. Natl. Acad. Sci. USA 99 (2002) 225-232] has advanced the concept that glycosphingolipids, particularly gangliosides, provide the intermediary link between transmembrane receptors and signal transducers and has redefined membrane rafts as Type-1, -2 or -3 glycosynapses. Here, using simple immunofluorescent analysis of the ganglioside complexes naturally released from cellular microprocesses (termed "footprints") we show that the ganglioside can determine the nature of protein-protein associations. Specifically, we demonstrate that CD36 and the tetraspanin CD151, both of which interact with beta1 integrins, associate together only in the presence of the gangliosides GD2/GD3. These results substantiate the glycosynapse hypothesis and suggest that the nature of the tetraspanin web may be determined by gangliosides.

A Phase I Study of an Anti-GD3 Monoclonal Antibody, KW-2871, in Patients with Metastatic Melanoma

PURPOSE

KW-2871 (IgG1 kappa chimeric antibody) targets GD3, which is upregulated in melanomas. We conducted a phase I trial of KW-2871 in patients with metastatic melanoma.

METHODS

Seventeen (17) patients were enrolled and received an initial test dose (10 mg/m2) intravenously. Two 2 weeks later, patients were stratified into 4 cohorts to receive 4 doses of KW-2871 (infused over 1 hour) at 2-week intervals (20, 40, 60, and 80 mg/m2). No premedications were administered for the test or first therapeutic doses.

RESULTS

Dose-limiting toxicities were Grade 3 laryngospasm and chest tightness with the initial therapeutic infusion at doses of 80 and 60 mg/m2. The maximum tolerated dose (MTD) was established at 40 mg/m2 of KW2871. The most common side-effect was urticaria (Grades 1-3) in 16 of 16 patients during an initial therapeutic infusion without premedication. The mean terminal half-life, clearance, and area under the concentration-time curve (AUC(0-t)) at a dose of 40 mg/m2 for course 1 were 146 +/- 31 hours, 28 +/- 6 ml/hour, and 1922 +/- 491 mcg*hour/mL, respectively. Anti-human chimeric antibody was not detected. Two (2) patients in the 40 mg/m2 cohort had stable disease.

CONCLUSIONS

An MTD of 40 mg/m2 without premedication was established for KW-2871, with urticaria being the most common side-effect and dose-limiting anaphylactoid infusion reactions.

Induction of IgG antibodies against the GD2 carbohydrate tumor antigen by vaccination with peptide mimotopes

The disialoganglioside GD2, a carbohydrate antigen, is expressed on all tumors of neuroectodermal origin, including melanoma, neuroblastoma, sarcoma and small cell lung cancer. Due to its specific expression on tumor surfaces, GD2 is an attractive target for immunotherapies. The mouse/human chimeric anti-GD2 mAb ch14.18 is already applied in melanoma and neuroblastoma trials as a passive immunotherapy. To establish an active immunotherapy alternative, we aimed to replace the poorly immunogenic ganglioside with immunogenic peptides. Previously, we used the ch14.18 antibody to select GD2 peptide mimics from a phage display library. In the present study, two mimics of the ch14.18 epitope were coupled to keyhole limpet hemocyanin and used for immunizing BALB/c mice. Induction of a specific humoral immune response towards the original antigen GD2, both purified and expressed on neuroblastoma and melanoma cells, could be demonstrated in ELISA, Western blot, and immunofluorohistochemistry. As the elicited antibodies were of the IgG isotype, the mimotope conjugates were capable of recruiting T cell help and inducing memory phenomena. In conclusion, we show that an epitope of the carbohydrate antigen GD2 can successfully be translated into immunogenic peptide mimotopes. Our immunization experiments indicate that GD2 mimotopes are suitable for active immunotherapy of GD2-expressing tumors.

Mechanisms for the apoptosis of small cell lung cancer cells induced by anti-GD2 monoclonal antibodies: roles of anoikis

Anti-GD2 ganglioside antibodies could be a promising, novel therapeutic approach to the eradication of human small cell lung cancers, as anti-GD2 monoclonal antibodies (mAbs) induced apoptosis of small cell lung cancer cells in culture. In this study, we analyzed the mechanisms for the apoptosis of these cells by anti-GD2 mAbs and elucidated the mechanisms by which apoptosis signals were transduced via reduction in the phosphorylation levels of focal adhesion kinase (FAK) and the activation of a MAPK family member, p38, upon the antibody binding. Knock down of FAK resulted in apoptosis and p38 activation. The inhibition of p38 activity blocked antibody-induced apoptosis, indicating that p38 is involved in this process. Immunoprecipitation-immunoblotting analysis of immune precipitates with anti-FAK or anti-integrin antibodies using an anti-GD2 mAb revealed that GD2 could be precipitated with integrin and/or FAK. These results suggested that GD2, integrin, and FAK form a huge molecular complex across the plasma membrane. Taken together with the fact that GD2+ cells showed marked detachment from the plate during apoptosis, GD2+ small cell lung cancer cells seemed to undergo anoikis through the conformational changes of integrin molecules and subsequent FAK dephosphorylation.

Gangliosides regulate tumor cell adhesion to collagen

The ability of tumor cells to adhere to extracellular matrix proteins is critical for migration and invasion. The factors that regulate tumor cell adhesion are poorly characterized. Gangliosides promote platelet adhesion and may also play a role in the adhesion of other cell types. We hypothesized that pharmacological depletion of membrane gangliosides from adherent cells would abrogate adhesion to collagen and promote migration and invasion. To test these hypotheses, LA-N1 neuroblastoma cells, which avidly adhere to collagen and are rich with membrane gangliosides (43.69 nmol/10(8) cells), were cultured in the presence of D-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol-HCl. Endogenous gangliosides were reduced by 98% (0.76 nmol/10(8) cells) and adhesion to collagen decreased by 67%. There were no changes in cell morphology, viability, proliferation rate or apoptosis. Pre-incubation of ganglioside-depleted cells in conditioned medium from control cells restored adhesion to collagen (0.45 +/- 0.002), comparable to that of control cells (0.49 +/- 0.035). Similarly, pre-incubation of ganglioside-depleted cells with purified GD2 completely restored adhesion in a concentration-dependent manner. When LA-N1 cells were cultured with retinoic acid, a biological response modifier known to increase endogenous gangliosides, adhesion to collagen increased. Next, we questioned whether changes in adhesion would be reflected as changes in migration and invasion. Cells depleted of endogenous cellular gangliosides migrated more than control cells. Finally, control cells replete with their endogenous gangliosides demonstrated less invasive potential than control cells. The data demonstrate that endogenous tumor gangliosides increase neuroblastoma cell adhesion to collagen and reduce migration and invasion in vitro.

Enhanced serine palmitoyltransferase expression in proliferating fibroblasts, transformed cell lines, and human tumors

Metastatic processes, including cell invasion, extracellular matrix degradation, and tissue remodeling, require cellular reorganization and proliferation. The cell signaling molecules required and the proteins involved in cell restructuring have not been completely elucidated. We have been studying the role of sphingolipids in normal cell activity and in several pathophysiological states. In this study we used immunohistochemistry to observe the presence of the two known subunits of serine palmitoyltransferase (SPT) in proliferating cells, in an in vitro model of wound repair, and in human malignant tissue. We report increased expression of the two subunits, SPT1 and SPT2, in the proliferating cells in these models. We also demonstrate a change in subcellular localization of the SPT subunits from predominantly cytosolic in quiescent cells to nuclear in proliferating cells. In addition, we observed SPT1 and SPT2 immunoreactivity in reactive stromal fibroblasts surrounding the carcinoma cells of some of the tumors. This enhanced SPT expression was absent in the stromal fibroblasts surrounding normal epithelial cells. Our results suggest a potential role for overexpression of SPT in the processes of cell metastasis.

Molecular dynamics simulation of GM1 in phospholipid bilayer

We report molecular dynamics simulation of fully hydrated lipid bilayer of dimyristoyl phosphatidyl choline (DMPC) at room temperature with ganglioside GM1 attached to it in the upper layer under periodic boundary conditions. The simulation results indicate that the presence of a single GM1 molecule has local effects on the bilayer. Three sugar residues (GalNAc-Gal-Glc) of the pentasaccharide head group of GM1 remain on the lipid surface where as the NeuNAc residue extends out in the aqueous layer. The radial distribution functions suggest ordering of water molecules near the glycerol and carboxyl group of the sialic acid in the upper layer. One of the ceramide chains of GM1, the sphingosine chain, folds up and is stacked under the sugar residues lying on the surface. The other ceramide chain is inserted into the lipid bilayer. The arrangement of the polar head group as well as the acyl chains of the lipids which are immediate neighbours of the GM1 are modified compared to the non-neighbour ones and others at the lower layer. The time average conformation of GM1-pentasaccharide is stabilized by a number of inter residue hydrogen bonds that were observed experimentally. The trajectory average conformation of GM1-pentasaccharide was docked on to the cholera toxin molecule and the minimized complex reveals alternative binding modes between the toxin and the GM1-pentasaccharide moiety. The results of these simulation studies might help to understand the structure and nature of the effects of GM1 on the membrane at atomic resolution.

Lactosylceramide is essential for the osteoclastogenesis mediated by macrophage-colony-stimulating factor and receptor activator of nuclear factor-kappa B ligand

Glycosphingolipids and their metabolites play important roles in a variety of biological processes. Several signal molecules are localized in a glycolipid-enriched microdomain on the cell surface, and their signals are regulated by the glycolipid composition. However, the function of glycolipids in osteoclastogenesis has not been clearly understood. We found that D-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol (D-PDMP), a glucosylceramide synthase inhibitor, completely inhibits the osteoclast formation induced by macrophage-colony-stimulating factor and receptor activator of nuclear factor-kappa B ligand (RANKL) in a dose-dependent manner. Expression of RANK, the receptor of RANKL, induced by macrophage colony-stimulating factor, was reduced markedly in D-PDMP-treated cells. d-PDMP also inhibited the phosphorylation of the inhibitor of nuclear factor-kappa B and extracellular signal-regulated kinase 1/2 induced by RANKL. In several experiments with the addition of glycolipids to D-PDMP-treated purified bone marrow cells, lactosylceramide (LacCer) strongly affected the differentiation into tartrate-resistant acid phosphatase mononucleated cells, but not positive multinucleated cells. GM3 and GM1 also recovered, but less effectively compared with LacCer. Moreover, exogenous LacCer recovered the reduced expression of RANK and the phosphorylation of inhibitor of NF-kappa B and extracellular signal-regulated kinase 1/2 after stimulation by RANKL at the same level of cells without D-PDMP treatment. Our data suggest that glycosphingolipids, especially LacCer, are necessary for the initiation step of RANKL-induced osteoclastogenesis.

Specific targeting, biodistribution, and lack of immunogenicity of chimeric anti-GD3 monoclonal antibody KM871 in patients with metastatic melanoma: results of a phase I trial

PURPOSE

KM871 is a chimeric monoclonal antibody against the ganglioside antigen GD3, which is highly expressed on melanoma cells. We conducted an open-label, dose escalation phase I trial of KM871 in patients with metastatic melanoma.

PATIENTS AND METHODS

Seventeen patients were entered onto one of five dose levels (1, 5, 10, 20, and 40 mg/m2). Patients received three infusions of KM871 at 2-week intervals, with the first infusion of KM871 trace-labeled with indium-111 (111In) to enable assessment of biodistribution in vivo. Biopsies of metastatic melanoma sites were performed on days 7 to 10.

RESULTS

Fifteen of 17 patients completed a cycle of three infusions of KM871. No dose-limiting toxicity was observed during the trial; the maximum-tolerated dose was therefore not reached. Three patients (at the 1-, 5-, and 40-mg/m2 dose levels) developed pain and/or erythema at tumor sites consistent with an inflammatory response. No normal tissue uptake of 111In-KM871 was observed, and tumor uptake of 111In-KM871 was observed in all lesions greater than 1.5 cm (tumor biopsy 111KM871 uptake results: range, 0.001% to 0.026% injected dose/g). The ratio of maximum tumor to normal tissue was 15:1. Pharmacokinetic analysis revealed a 111In-KM871 terminal half-life of 7.68 +/- 2.94 days. One patient had a clinical partial response that lasted 11 months. There was no serologic evidence of human antichimeric antibody in any patient, including one patient who received 16 infusions over a 12-month period.

CONCLUSION

This study is the first to demonstrate the biodistribution and specific targeting of an anti-GD3 antibody to metastatic melanoma in patients. The long half-life and lack of immunogenicity of KM871 makes this antibody an attractive potential therapy for patients with metastatic melanoma.

Myelin-associated glycoprotein interacts with ganglioside GT1b. A mechanism for neurite outgrowth inhibition

Myelin-associated glycoprotein (MAG) is expressed on myelinating glia and inhibits neurite outgrowth from post-natal neurons. MAG has a sialic acid binding site in its N-terminal domain and binds to specific sialylated glycans and gangliosides present on the surface of neurons, but the significance of these interactions in the effect of MAG on neurite outgrowth is unclear. Here we present evidence to suggest that recognition of sialylated glycans is essential for inhibition of neurite outgrowth by MAG. Arginine 118 on MAG is known to make a key contact with sialic acid. We show that mutation of this residue reduces the potency of MAG inhibitory activity but that residual activity is also a result of carbohydrate recognition. We then go on to investigate gangliosides GT1b and GD1a as candidate MAG receptors. We show that MAG specifically binds both gangliosides and that both are expressed on the surface of MAG-responsive neurons. Furthermore, antibody cross-linking of cell surface GT1b, but not GD1a, mimics the effect of MAG, in that neurite outgrowth is inhibited through activation of Rho kinase. These data strongly suggest that interaction with GT1b on the neuronal cell surface is a potential mechanism for inhibition of neurite outgrowth by MAG.

Recognition of cell surface GD3 by monoclonal antibody anti-6C2 in rheumatoid arthritis synovial fluid: expression on human T cells with transendothelial migratory activity

OBJECTIVE

We have previously reported that the anti-6C2 monoclonal antibody (mAb) defines a subset of human CD4+ memory T cells. The present study sought to determine the nature of the 6C2 molecule and the function associated with 6C2+ T cells, and to examine whether this T cell subset is involved in the pathophysiology of rheumatoid arthritis (RA).

METHODS

Cytofluorographic analysis was performed for identification of T cell surface molecules displaying a distribution similar to that of the 6C2 molecule. T cells in the synovial fluid of RA patients were examined for expression of the 6C2 molecule. Transendothelial migratory activity was assessed by assay using monolayers of human endothelial cells. Specific reactivity of the anti-6C2 mAb was determined by immunoblotting on gangliosides separated by thin-layer chromatography, and flow cytometric analysis of the cells transfected with complementary DNA (cDNA) was performed for determination of the glycosyltransferases involved in biosynthesis of the gangliosides.

RESULTS

On human peripheral T cells, the 6C2 molecule was distributed, by and large, in a pattern similar to that of CDw60, or O-acetyl-GD3. The majority (>70%) of synovial fluid T cells from patients with RA were found to be 6C2 positive, and those 6C2+ T cells exhibited a transendothelial migratory capacity that was inhibited by pretreatment of T cells with anti-6C2 mAb. Moreover, treatment of T cells with neuraminidase resulted in a loss of 6C2 expression as well as a reduction in the transendothelial migratory activity. Anti-6C2 mAb reacted specifically with GD3, but not with O-acetyl-GD3. The reactivity of anti-6C2 mAb was induced on the cell surface only by transfection with cDNA for GD3 synthase.

CONCLUSION

The 6C2 molecule is a disialoganglioside, GD3, and is present on a subset of T cells with transendothelial migratory capacity. The 6C2/GD3 molecules, as well as 6C2/GD3+ T cells, appear to play a role in T cell migration and in the inflammation of RA.

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.

Participation of the GM1 ganglioside in the gastrulation of anuran amphibian Bufo arenarum

In the present paper we established the ganglioside composition of the blastula and gastrula stages of the anuran amphibian Bufo arenarum, two relevant stages characterized by dynamic changes in morphology and cellular rearrangements. Densitometric studies evidenced that GD1a and GT1b were the more abundant gangliosides of the blastula embryos whereas GM1 and GM2 were the predominant species in gastrula embryos. Analysis of ganglioside abundance indicates that the "a" and "b" synthesis pathways perform similar biosynthetic activities in the blastula stage, in contrast to the gastrula stage in which a marked predominance of the "a" pathway occurred. The spatio-temporal expression of GM1 and of polygangliotetraosyl ceramides (pGTC) was investigated by wholemount immunocytochemistry using cholera toxin B subunit (CTB) and an affinity purified human anti-GM1 antibody. The pGTC were detected as GM1 after treatment with neuraminidase. Blastomeres from the inner surface of the blastocoelic roof (BCR) of blastula embryos were GM1 and pGTC positive. At midgastrula stage, embryos showed an increased labeling on the inner surface of BCR. To establish whether the GM1 ganglioside was involved in the gastrulation processes, CTB, anti-GM1 antibodies and anti-GM1 Fab' fragments were microinjected into the blastocoel cavity of blastula embryos. Treatment with the probes blocked gastrulation. Scanning electron microscopy analysis of blocked embryos revealed that mesodermal cell migration, radial interdigitation, and convergent extension movements were affected. The blocking of gastrulation was correlated with the absence of fibronectin and EP3/EP4 on the inner surface of blastocoelic roof of CTB- or anti-GM1 treated embryos. Results show that the GM1 ganglioside is differentially expressed by embryonic cells and participates in the morphogenetic processes of amphibian gastrulation. J. Exp. Zool. 286:457-472, 2000.

Tenascin-R interferes with integrin-dependent oligodendrocyte precursor cell adhesion by a ganglioside-mediated signalling mechanism

Oligodendrocyte (OL) lineage progression is characterized by the transient expression of the disialoganglioside GD3 by OL precursor (preOL) cells followed by the sequential expression of myelin-specific lipids and proteins. Whereas GD3+ preOLs are highly motile cells, the migratory capacity of OLs committed to terminal differentiation is strongly reduced, and we have recently shown that the extracellular matrix protein tenascin-R (TN-R) promotes the stable adhesion and differentiation of O4+ OLs by a sulphatide-mediated autocrine mechanism (O4 is a monoclonal antibody recognizing sulphatides/seminolipids expressed by OLs and in myelin). Using culture conditions that allow the isolation of mouse OLs at distinct lineage stages, here we demonstrate that TN-R is antiadhesive for GD3+ preOLs and inhibits their integrin-dependent adhesion to fibronectin (FN) by a disialoganglioside-mediated signalling mechanism affecting the tyrosine phosphorylation of the focal adhesion kinase. This responsive mechanism appears to be common to various cell types expressing disialogangliosides as: (i) disialogangliosides interfered with the inhibition of cell adhesion of different neural and non-neural cells on substrata containing TN-R and FN or RGD-containing FN fragments. TN-R interacted specifically with disialoganglioside-expressing cells or immobilized gangliosides, and ganglioside treatment of TN-R substrata resulted in a delayed preOL cell detachment as a function of time. We conclude that OL response to one and the same signal in the extracellular matrix critically depends on the molecular repertoire expressed by OLs at different lineage stages and could thus define their final positioning.

Endogenous galectins and effect of galectin hapten inhibitors on the differentiation of the chick mesonephros

Galectins are galactoside-binding lectins. In the mesonephros of the chick embryo, the 16-kDa galectin is abundant in the glomerular and tubular basement membranes where it colocalizes with fibronectin and laminin. To test whether galectin-glycoprotein interactions could play a role in mesonephric development, the effects of the galectin hapten inhibitors thiodigalactoside (TDG) and lactose on the differentiation of the cultured mesonephros were investigated. When compared to control saccharide-free or maltose-treated cultures, mesonephroi cultured in the presence of TDG and lactose exhibited defects in tissue organization. These included a distorted tubule shape, pseudo-stratification of the tubular epithelium, and detachment of glomerular podocytes from the basement membrane. The presence of molecular differentiation markers in the developing mesonephros was investigated. In vivo, expression of the epithelial-specific cell adhesion molecule E-cadherin is restricted to differentiated tubular epithelial cells, whereas the intermediate filament protein vimentin is present in mesonephrogenic mesenchyme and is undetectable in tubular epithelial cells. In mesonephroi cultured in the absence of sugars or in the presence of maltose, the expression pattern of these two marker molecules resembles that found in the mesonephros in vivo. In contrast, in the mesonephroi cultured in the presence of TDG and lactose, the epithelial tubular cells expressing E-cadherin also express vimentin. Re-expression of vimentin in the tubular epithelial cells could indicate a partial reversal to a mesenchymal phenotype. Results suggest that galectin-glycoprotein interactions in the basement membrane are important in the maintenance of the renal epithelial phenotype. Dev Dyn 1999;215:248-263.

Tenascin-C inhibits beta1 integrin-dependent cell adhesion and neurite outgrowth on fibronectin by a disialoganglioside-mediated signaling mechanism

We have previously shown that the extracellular matrix molecule tenascin-C inhibits fibronectin-mediated cell adhesion and neurite outgrowth by an interaction with a cellular RGD-independent receptor which interferes with the adhesion and neurite outgrowth promoting activities of the fibronectin receptor(s). Here we demonstrate that the inhibitory effect of tenascin-C on beta1integrin-dependent cell adhesion and neurite outgrowth is mediated by the interaction of the protein with membrane-associated disialogangliosides, which interferes with protein kinase C-related signaling pathways. First, in substratum mixtures with fibronectin, an RGD sequence-containing fragment of the molecule or synthetic peptide, tenascin-C inhibited cell adhesion and spreading by a disialoganglioside-dependent, sialidase-sensitive mechanism leading to an inhibition of protein kinase C. Second, the interaction of intact or trypsinized, i.e., cell surface glycoprotein-free, cells with immobilized tenascin-C was strongly inhibited by gangliosides or antibodies to gangliosides and tenascin-C. Third, preincubation of immobilized tenascin-C with soluble disialogangliosides resulted in a delayed cell detachment as a function of time. Similar to tenascin-C, immobilized antibody to GD2 (3F8) or sphingosine, a protein kinase C inhibitor, strongly inhibited RGD-dependent cell spreading. Finally, the degree of tenascin-C-induced inhibition of cell adhesion was proportional to the degree of disialoganglioside levels of expression by different cells suggesting the relevance of such mechanism in modulating integrin-mediated cell-matrix interactions during pattern formation or tumor progression.

Molecular mimicry of phage displayed peptides mimicking GD3 ganglioside

We have analyzed sequence homologies between nonimmunogenic phage displayed peptides mimicking GD3 ganglioside and human/mouse self-proteins. The GD3 ganglioside phagotopes showed homology to proteins involved in carbohydrate metabolism/transport. Besides this expected homology, molecular mimicry of critical regulatory proteins was found. These data contribute to our understanding of the structural relatedness of antigenic determinants defined by specific anti-GD3 monoclonal antibodies and, in addition, suggest that molecular mimicry might explain the nonimmunogenicity of these peptides otherwise characterized by specificity to the mAb counterpart. We conclude that construction of peptides harboring motifs absent or scarcely represented in endogenous self-proteins might be a useful approach in melanoma immunotherapy.

Chimeric antibodies with specificity for tumor antigens: demonstration of in situ localization to tumors after antibody therapy

In this study, we compare various methods for the detection of a tumor-associated target antigen and deposition of the bound therapeutic monoclonal antibody in patients enrolled in two separate trials, one involving the administration of two radiolabeled monoclonal antibodies and the other involving an unlabeled antibody. In the first trial, patients with TAG-72 expressing metastatic colon cancer scheduled for surgical intervention received radiolabeled murine and chimeric B72.3 antibody followed by radioimmune imaging and subsequent laparotomy. Normal and tumor tissues obtained at surgery were processed for routine histology, immunohistochemistry, radiometry, and autoradiography. Both anti-TAG-72 antibodies localized to known tumor sites as evidenced by radioimmune imaging. Resected tissue revealed a high tumor-to-normal radiolocalization ratio, and autoradiography demonstrated even deposition of the radiolabeled antibodies throughout the entire tumor deposit with sparing of surrounding normal tissue. In contrast, immunohistochemistry on the same sections revealed comparatively weak antigen expression and patchy antibody localization. In the second trial, patients with GD2 antigen expressing metastatic melanoma received the unlabeled chimeric anti-GD2 antibody C14.18. Immunologic detection of the GD2 antigen and C14.18 deposition was performed on biopsy section as well as on single cell suspension. FACS analysis of the single cell suspension proved more sensitive for the detection of bound antibody than immunohistochemistry, although both methods yielded comparable results for GD2 antigen expression. Our findings demonstrate that the optimal method for the detection of tumor-associated antigen and bound therapeutic antibody can vary depending upon the nature of the antibody (radiolabeled vs. unlabeled and murine vs. chimeric), fixation stability of the target antigen, and the type of pathologic material available for study.

Characterization of human IgG1 monoclonal antibody against gangliosides expressed on tumor cells

A human IgG1.k monoclonal antibody (MAb) designated GMA1 was developed by fusing pooled lymph node lymphocytes from cancer patients with the human lymphoblastoid cell line, SHFP-1. The GMA1 MAb reacted with several melanoma and neuroblastoma cell lines. Normal tissue derived from human brain and tumor-cell lines derived from colon, ovary, and breast were not reactive. FACS analysis performed using live cells demonstrated that the antibody recognizes a cell-surface antigen. Enzyme immunoassay (EIA) and thin layer chromatography (TLC) immunostaining with purified gangliosides indicated that the antibody has specificity for the major tumor associated gangliosides GD3, GM3, and GD2. GMA1 heavy and light chain genes were isolated by RT-PCR and a recombinant derivative of this human antibody was expressed in Chinese hamster ovary (CHO) cells. High-level antibody synthesis and secretion was achieved using a vector designed to maximize expression. FACS analysis and TLC immunostaining indicated recombinant GMA1 reacted with human tumor cell lines and gangliosides GD3, GM3, GD2 in a manner similar to the antibody produced by the hybridoma cell line, demonstrating that the specificity of the antibody was not altered during molecular cloning.