Monoclonal antibodies against epitopes on ganglioside GD2 and its lactones. Markers for gliomas and neuroblastomas

Alkali-labile gangliosides

The structure and properties of a group of gangliosides modified by mild alkaline treatment are discussed. We will present the occurrence and the structure of gangliosides carrying the N-acetyneuraminic acid O-acetylated in position 9, the Neu5,9Ac₂, and of gangliosides carrying a sialic acid that forms a lactone ring. Starting from biochemical data we will discuss the possible biochemical role played by these gangliosides in the processes of cell signaling and maintenance of brain functions.

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.

Immunohistochemically visualized localisation of gangliosides Glac2 (GD3) and Gtri2 (GD2) in cells of human intracranial tumors

Antibodies against two major gangliosides detected in human brain and brain tumors--Glac2 (GD3) and Gtri2 (GD2)--were tested by immunohistochemistry in an unselected sample of intracranial tumors during the years 1986 through 1991. Two groups emerged as evaluable samples, namely gliomas of different grades and meningiomas. In a pilot series, it was shown that these gangliosides could be visualized in frozen sections of cells of gliomas and meningiomas (as well as neurinomas) and in some structures of the normal brain. It was however not possible in frozen sections to further analyze the cellular or subcellular expression pattern of the mentioned components and paraffin sections with conventional processing were only weakly and diffusely stained. A modified protocol therefore was created that replaced alcohol processing by acetone. With this protocol, interpretable results in paraffin sections were obtained. With this method, 133 single intracranial tumors were investigated as to their immunohistologically detectable ganglioside expression. The most consistent result was that the whole cytoplasm of highly fibrillary (gemistocytic) astrocytes in all grades of gliomas was stained by Gtri2 (GD2) and Glac2 (GD3) with high preponderance of Gtri2 (GD2) expression. In all meningiomas, Glac2 (GD3) had a higher expression than Gtri2. No constant pattern in the other entities emerged. By comparison with GFAP expression in gliomas and vimentin in meningiomas, the colocalisation of gangliosides and intermediary filament proteins is supposed.

Human anti-CD30 recombinant antibodies by guided phage antibody selection using cell panning

In various clinical studies, Hodgkin's patients have been treated with anti-CD30 immunotherapeutic agents and have shown promising responses. One of the problems that appeared from these studies is the development of an immune response against the nonhuman therapeutics, which limits repeated administration and reduces efficacy. We have set out to make a recombinant, human anti-CD30 single-chain variable fragment (scFv) antibody, which may serve as a targeting moiety with reduced immunogenicity and more rapid tumour penetration in similar clinical applications. Rather than selecting a naive phage antibody library on recombinant CD30 antigen, we used guided selection of a murine antibody in combination with panning on the CD30-positive cell line L540. The murine monoclonal antibody Ki-4 was chosen as starting antibody, because it inhibits the shedding of the extracellular part of the CD30 antigen. This makes the antibody better suited for CD30-targeting than most other anti-CD30 antibodies. We have previously isolated the murine Ki-4 scFv by selecting a mini-library of hybridoma-derived phage scFv-antibodies via panning on L540 cells. Here, we report that phage display technology was successfully used to obtain a human Ki-4 scFv version by guided selection. The murine variable heavy (VH) and light (VL) chain genes of the Ki-4 scFv were sequentially replaced by human V gene repertoires, while retaining only the major determinant for epitope-specificity: the heavy-chain complementarity determining region 3 (CDR3) of murine Ki-4. After two rounds of chain shuffling and selection by panning on L540 cells, a fully human anti-CD30 scFv was selected. It competes with the parental monoclonal antibody Ki-4 for binding to CD30, inhibits the shedding of the extracellular part of the CD30 receptor from L540 cells and is thus a promising candidate for the generation of anti-CD30 immunotherapeutics.

Induction of antibodies against GD3 ganglioside in melanoma patients by vaccination with GD3-lactone-KLH conjugate plus immunological adjuvant QS-21

The gangliosides GD3, GD2 and GM2 are expressed on the cell surface of malignant melanomas, GD3 being the most abundant. We have shown that immunization of melanoma patients with GM2 adherent to Bacillus Calmette-Guerin (GM2/BCG) induced an IgM antibody response. Vaccines containing GM2-keyhole limpet hemocyanin (KLH) conjugate and the immunological adjuvant QS-21 induced a higher titer IgM response and consistent IgG antibodies. Patients with antibodies against GM2 survived longer than patients without antibody. On the other hand, our previous trials with GD3/BCG, GD3 derivatives including GD3-lactone (GD3-L)/BCG failed to induce antibodies against GD3. In our continuing efforts to induce antibody against GD3, we have immunized groups of 6 melanoma patients with GD3-KLH or GD3-L-KLH conjugates containing 30 microg of ganglioside plus 100 microg of QS-21 at 0, 1, 2, 3, 7 and 19 weeks. Prior to vaccination, no serological reactivity against GD3 or GD3-L was detected. After immunization, IgM and IgG antibodies were detected against both GD3 and GD3-L in the GD3-L group exclusively. The GD3-L-KLH vaccine induced IgM titers against GD3-L of 1:40-1/1,280 in all patients and IgG titers of 1/160-1/1,280 in 4 patients. These antibodies also strongly cross-reacted with GD3. ELISA reactivity was confirmed by immune thin-layer chromatography on GD3 and melanoma extracts. Sera obtained from 4 of these 6 patients showed cell surface reactivity by FACS and from 2 showed strong cell surface reactivity by immune adherence (IA) assay and complement lysis against the GD3 positive cell line SK-Mel-28.

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.

Normal human serum contains a natural IgM antibody cytotoxic for human neuroblastoma cells

Neuroblastoma (NB) is characterized by the second highest spontaneous regression of any human malignant disorder, a phenomenon that remains to be elucidated. In this study, a survey of 94 normal human adult sera revealed a considerable natural humoral cytotoxicity against human NB cell lines in approximately one-third of the tested sera of both genders. Specific cell killing by these sera was in the range of 40% to 95%. Serum cytotoxicity was dependent on an intact classical pathway of complement. By several lines of evidence, IgM antibodies were identified as the cytotoxic factor in the sera. Further analyses revealed that a 260-kDa protein was recognized by natural IgM of cytotoxic sera in Western blots of NB cell extracts. The antigen was expressed on the surface of seven human NB cell lines but not on human melanoma or other control tumor cell lines derived from kidney, pancreas, colon, bone, skeletal muscle, lymphatic system, and bone marrow. Furthermore, no reactivity was observed with normal human fibroblasts, melanocytes, and epidermal keratinocytes. The antigen was expressed in vivo as detected by immunohistochemistry in both the tumor of a NB patient and NB tumors established in nude rats from human NB cell lines. Most interestingly, the IgM anti-NB antibody was absent from the sera of 11 human NB patients with active disease. The anti-NB IgM also could not be detected in tumor tissue obtained from a NB patient. Collectively, our data suggest the existence of a natural humoral immunological tumor defense mechanism, which could account for the in vivo phenomenon of spontaneous NB tumor regression.

Generation of monoclonal antibodies specific for ganglioside lactones: evidence of the expression of lactone on human melanoma cells

We generated 3 murine monoclonal antibodies (MAbs) specific for ganglioside lactones by immunizing C3H/HeN mice with purified lactones adsorbed to Salmonella minnesota followed by fusion with mouse myeloma cells. The use of a wide variety of glycolipids, including ganglioside lactones, enabled the precise structures recognized by these MAbs to be elucidated through an ELISA and by immunostaining on thin-layer chromatography. MAb AMR38, which was generated with GM1 lactone, showed restricted specificity, detecting only the GM1 lactone used for immunization. None of the other ganglioside lactones, intact gangliosides (including GM1) or neutral glycolipids tested were recognized. In contrast, MAbs AMR40 and AMR19, which were generated with GD1a lactone and GD3 lactone, respectively, showed broader specificities, recognizing several ganglioside lactones. However, the precise epitopes were different. MAb AMR40 reacted intensely with ganglioside lactones having an external NeuAc alpha 2-->3Gal-sequence (GD1a, GM3, GM1b, GT1b, and IV3NeuAc alpha-nLc4Cer), but not with those having a NeuAc alpha 2-->8NeuAc alpha 2-->3Gal- sequence. On the other hand, MAb AMR19 reacted with ganglioside lactones having a NeuAc alpha 2-->8NeuAc alpha 2-->3Gal- sequence (GD3, O-Ac-GD3, GD2, GDlb, GTlb, GQlb and GTla), but not with those having a NeuAc alpha 2-->3Gal- sequence. None of the intact gangliosides or neutral glycolipids tested were recognized by the MAbs. We also determined the expression of ganglioside lactones on human melanoma cells grown in athymic nude mice by means of an immunofluorescence technique.

Expression of GD2-epitopes in human intracranial tumors and normal brain

Two monoclonal antibodies (mabs) were raised against ganglioside GD2 (Gtri2) and tested on human intracranial tumors and normal brain by immunohistochemical methods both in frozen and paraffin embedded sections. In normal brain structures, astrocytes were visualized with both mabs (BW 625 and BW 704) almost exclusively in the subventricular and subpial layer. A minor amount of myelin sheaths in well defined localisation was only recognized in frozen sections. Consequently in astrocytic tumors of different grades of malignancy (WHO I-IV), astrocytes were depicted in their characteristic shape and arrangement around vessels. In addition, staining was observed in meningiomas and schwannomas, but not in pituitary adenomas or metastatic carcinomas. In meningioma und schwannoma the staining was restricted to the cellular periphery and was again present in frozen section material and absent in paraffin embedded tissue. In astrocytes, reactive and neoplastic, obviously fibrous processes and cytoplasm were distinctly stained both in frozen and paraffin embedded sections. It is concluded that some neuroectodermal derived cells as well as myelin of defined localisation express GD2 on the membrane surfaces and in the cytoplasm. The latter may primarily be the case in fibrous astrocytes, which were stained in reactive and pathologic conditions. The reaction can be used as diagnostic tool in astrocytic tumors; its positive therapeutic significance is hampered by the fact that (1) not all cells in heterogeneous tumor populations express the epitope and (2) there are normal structures which do so.

Gangliosides in meningiomas: correlation of Glac2 to intermediary filament

Human meninges and 29 meningiomas were analyzed as to their glycosphingolipid composition. In the neutral fraction GSL, a mostly even distribution of mono-, di-, tri-and tetrahexoside was demonstrated. In the group of the gangliosides, Glac1 in one broad band in chromatograms occurred in almost all meningiomas; Glac2 was present in 84% of tumours. Members of the Gtn-family were only found in a small minority of tumours while various Gtet-gangliosides were detectable in nearly half of them. No constant pattern or patterns emerged and no correlation to either morphological subtype or malignancy grade could be established. Immunohistochemistry revealed focal presence of Glac2 in a pattern similar to that of vimentin expression. Semiquantitative evaluation showed good correlation between both parameters.

Disialoganglioside GD2 in human neuroectodermal tumor cell lines and gliomas

Monoclonal antibodies (mAbs) recognizing the disialoganglioside II3(NeuAc)2GgOse3Cer (GD2) were produced by immunizing mice with the GD2-expressing neuroblastoma cell line LAN-1 and a prefusion boost with purified GD2 coupled to Salmonella minnesota. Two IgM mAbs were isolated which demonstrated high levels of reactivity (binding ratios in excess of 100) with GD2 by solid-phase radioimmunoassay and positivity in high-performance thin-layer chromatography (HPTLC) immunostain; only one (DMAb-20) was subsequently shown by analysis with a panel of defined ganglioside species to be specific for the minimum epitope of GD2 GalNAc beta 1-4(NeuAc alpha 2-8-NeuAc alpha 2-3)Gal-, DMAb-20 was used to evaluate the expression of GD2 by malignant glioma and medulloblastoma cell lines using cell surface radioimmunoassay. indirect membrane immunofluorescence. HPTLC immunostain, and densitometric analysis of extracted gangliosides from selected cell lines. Sixteen of 20 (80%) malignant glioma and 5 of 5 medulloblastoma cell lines reacted with DMAb-20; in agreement with previous studies, 5 of 5 neuroblastoma and 2 of 3 melanoma cell lines also reacted with DMAb-20, GD2 was proportionally increased in the glioma and medulloblastoma cell lines relative to levels in normal brain, as determined by densitometric analysis. In a phenotypic survey of malignant glioma biopsies, tumor cells in 24 of 30 (80%) cases stained positively with DMAb-20. Reactive astrocytes, both within the adjacent to tumors, were frequently intensely stained. Among the morphological variants of glioblastoma examined, the most intense staining with DMAb-20 was observed in neoplastic gemistocytes, with the weakest or absent staining in small cell glioblastomas. As GD2 is a commonly expressed surface antigen of gliomas and medulloblastomas, expression of which is retained in tissue culture. DMAb-20 will be useful in determining the functional role of GD2 in cell-cell interaction, adhesion, and invasion, and in defining altered growth control mechanisms of central nervous system neoplasms in in vitro models.

Antibody response to immunization with ganglioside GD3 and GD3 congeners (lactones, amide and gangliosidol) in patients with malignant melanoma

GD3 is the ganglioside most abundantly expressed on the cell surface of human melanoma, and treatment with a murine MAb recognizing GD3 has induced major responses in a small proportion of patients with melanoma. We have therefore attempted to induce production of GD3 antibodies in melanoma patients by active immunization. We found, however, that vaccination with GD3-expressing melanoma cells or purified GD3 does not result in antibody production. We describe here attempts to overcome the poor immunogenicity of GD3 in patients with melanoma by chemical modification. GD3 lactones, GD3 amide and GD3 gangliosidol were synthesized, and the humoral immune response to these derivatives was analyzed. Immunization of melanoma patients with these GD3 derivatives resulted in production of IgM antibodies and, in the case of GD3 amide, also of IgG antibodies. The antibodies to the GD3 derivatives did not cross-react with GD3. This is in contrast to observations in the mouse, where GD3 lactone I induced antibodies that showed cross-reactivity with GD3. Thus, the human immune response was specifically directed toward the modified epitope, rather than to the native structure.

Gangliosides: the relevance of current research to neurosurgery

Gangliosides are complex glycolipids found on the outer surface of most cell membranes: they are particularly concentrated in tissues of the nervous system. Gangliosides form part of the immunological identity of mammalian cells and are involved in a variety of cell-surface phenomena such as cell-substrate binding and receptor functions. In tumorous tissue, the ganglioside composition is altered, sometimes in direct proportion to the degree of malignancy. The literature on the glycosphingolipid composition and immunology of intracranial tumors is reviewed. Some gangliosides induce neuritogenesis and exhibit a trophic effect on nerve cells grown in vitro. In vivo, a particular ganglioside, GM1, reduces cerebral edema and accelerates recovery from injury (traumatic and ischemic) to the peripheral and central nervous systems of laboratory animals. Preliminary clinical studies have shown that treatment with gangliosides may have corresponding effects on lesions of the human peripheral nervous system. Gangliosides have not been tested in human subjects with brain injury.

Tissue architecture and glycosphingolipid content in human gliomas II-IV

Contradictory results have been reported claiming either none, partial or almost complete correlation between the complexity of GSL compound profiles and the assumed glial tumor differentiation. Therefore an attempt was made to compare GSL patterns with both the general (final) tumor diagnosis and malignancy grade (WHO) as well as the regional evaluation of the histology and the grading in the tumor tissue pieces directly subjected to biochemical analysis. Regional and general (final) diagnosis did not always correspond, especially when more than one tissue sample of a given tumor was analyzed. Four GSL component patterns were identified by TLC: GSL-type I with gangliosides primarily of the simple Glac-family lacking sulfatide and the more complex Gtri- and Gtet-gangliosides, GSL-type II with ganglioside of the Glac- and Gtri-families, also without sulfatide, and GSL-type III, with more complex gangliosides of the Gtri- and Gtet-families in addition to Glac-gangliosides and sulfatide, similar to the normal brain pattern, and the pattern of normal brain. There was only insufficient correlation between these GSL-type patterns and final diagnoses. However, between regional diagnosis of astrocytoma II and GSL-type III on the one hand and glioblastoma multiforme IV and GSL-type I on the other hand, a coincidence of more than 85% was found. In only 50% the intermediate GSL-type II and glioma III were associated. There was no relation between GFAP or vimentin expression and histology or GSL-type both with regard to final and regional diagnoses. Regional astrocytoma architectures exhibiting GSL-type III were mostly fibrillary, whilst glioblastomas with GSL component pattern I had often a giant cell make up.(ABSTRACT TRUNCATED AT 250 WORDS)

Cystic meningioma with unusual histopathological features

A parasagittal meningioma of an eighty year old female patient showed by light and electron microscopy cystic architecture (forme humide) as well as nuclear vacuoles (indentations) and cytoplasmic inclusions. The latter are the known pseudopsammoma bodies or hyaline inclusions as demonstrated by light and electron microscopy. Light microcopy on paraffin sections and cytological smear preparations revealed, in addition to the cells of endotheliomatous meningioma and those containing the inclusions a third type with small granular cytoplasmic content. Electron microscopy showed characteristic features of meningioma such as folded double membranes, desmosomes and filaments and thus gave evidence of the meningiomatous nature of the tumor. By immunohistochemistry tumor cells in slightly focal distribution contained vimentin, whereas small clusters of cells with hyaline inclusions were strongly positive for cytokeratin. The dispersed cells of granular cytoplasmic content were positive for fibronectin. These findings, especially of the inclusion containing cytokeratin positive cell clusters may shed new light upon the concept of histogenesis and classification.