Developments in the biology of neuroblastoma: implications for diagnosis and treatment

Cellular cytotoxicity mediated by isotype-switch variants of a monoclonal antibody to human neuroblastoma

The biological property of an antibody is determined by its antigen binding characteristics and its isotype-related effector functions. We have established monoclonal antibodies of different isotypes by stepwise selection and cloning of the hybridoma CE7. The original CE7 secretes an IgG1/kappa (CE7 gamma 1) antibody that recognises a 185 kD cell surface glycoprotein expressed on all human sympatho-adrenomedullary cells. Isotype-switch variants were isolated in the following sequence: from the original CE7 gamma 1, CE7 gamma 2b variants were isolated, and from a CE7 gamma 2b variant CE7 gamma 2a variants were isolated. The antibodies of three different isotype variant cell lines possess identical antigen binding characteristics, but display distinct effector functions as demonstrated by antibody dependent cell-mediated cytotoxicity (ADCC). ADCC was performed with the neuroblastoma line IMR-32 as the target cells, and different FcR gamma positive cells were either freshly isolated from human peripheral blood leukocytes or cultured for 6-10 days and tested as potential effector cells. Tumour lysis mediated by monocyte-derived macrophages depended on the presence of CE7 gamma 2a antibodies; antibodies from the CE7 hybridomas of gamma 2b and gamma 1 isotypes were virtually inactive in ADCC assay. Pre-exposure of macrophages to rIFN-gamma enhanced their ADCC activity, a result that is compatible with the notion that the high affinity Fc IgG receptor (FcR gamma I/CD64) is involved in the triggering of ADCC in macrophages. In contrast to macrophages, mononuclear cells, nonadherent cells and monocytes displayed considerable non-specific lytic activity, which was little influenced by the presence of antibody regardless of the isotype added.

Immunological detection and definition of minimal residual neuroblastoma disease in bone marrow samples obtained during or after therapy

Immunological staining by the alkaline phosphatase/anti-alkaline phosphatase (APAAP) technique has been used to recognize low levels of neuroblastoma cells in bone marrow mononuclear cells. Immunological phenotyping with 11 well characterized monoclonal antibodies was performed on 16 children with neuroblastoma and BM involvement during or after therapy. Neuroblasts were detected in 11 of 16 patients (0.1-5%), whereas BM biopsies on six of these patients were classified as normal. Aspirates, stained conventionally, were positive for pathological cells in three patients only. The comparison of the phenotype of the neuroblastoma cells at the time of diagnosis to the phenotype of the residual cells within one patient revealed differences. The phenotype of residual disease in different patients on the other hand showed a unique pattern. The above mentioned results lead to the conclusion that the immunological procedure is particularly suitable for the analysis of minimal residual neuroblastoma since the technique allows very minor cell populations to be identified in BM samples.

Immunohistochemical performance testing of monoclonal antibodies to neuroblastoma cells on normal adrenals, spinal and sympathetic ganglia, and neural crest tumours

Tissue specimens of neural crest-derived structures like normal spinal and sympathetic ganglia and adrenals of adults, infants and fetuses were used as immunohistochemical test substrates for a panel of 10 monoclonal antibodies to neuroblastoma cells raised by immunization with a variety of immunogens (fetal brain, neuroblastoma cell lineages, chick retinal cells or purified Thy-1 antigen). Antigen expression varied among normal structures such as ganglion cells, satellite cells, various nerve fibres, and different cells in the adrenal cortex. This variability in immunoreactivity shown by different cell types and structures was comparable to that seen when the same panel of monoclonal antibodies was applied to neuroblastomas and to ganglioneuroblastomas of different degrees of maturation and differentiation. The neoplasms thus seemed to reflect the normal maturation in the neuroectodermally-derived structures. Also, the studies give indications as to the cell of origin of the undifferentiated neuroblastomas.

Immunohistochemical differentiation of neuroblastomas from other small round cell neoplasms of childhood using a panel of mono- and polyclonal antibodies

A panel of monoclonal antibodies to neuroblastoma cells, leucocyte common antigen, vimentin and MHC class II antigens (HLA-DR) and a polyclonal antibody to epidermal keratin were used for immunohistochemistry on sections of ethanol fixed and paraffin embedded specimens from 40 undifferentiated small cell tumours and 10 neural crest neoplasms. With the exception of central nervous system neoplasms and two embryonal rhabdomyosarcomas, immunohistochemical examination discriminated between the neural crest neoplasms and the other small cell tumours. Moreover, the staining pattern of neoplastic cells and structures in the neural crest neoplasms obtained with antibodies to neuroblastoma cells seemed, in part, to reflect the degree of tumour differentiation.

Production and characterization of monoclonal antibodies against human neuroblastoma

MAb were derived from mice immunized with cells of the human neuroblastoma line IMR-32. Five hybridomas were selected according to their selective binding to human cell lines, tumors and normal tissues. One of them, CE7, reacted with all sympatho-adrenomedullary cells (neuroblastoma, ganglioneuroblastoma, ganglioneuroma, pheochromocytoma, adrenal medulla, sympathetic ganglion cells). Weak cross-reactivities were observed with melanocytes and with some human melanoma and glioma cell lines. The antigen recognized by CE7 was markedly expressed on neuroblastoma tumors of all histological grades, independently of the adrenergic or cholinergic nature of these cells. MAb derived from clones AD2, BC1, BC4 and CB10 bound variably to some, but not to all, neuroblastoma cells. By using these MAb, 3 phenotypes of neuroblastoma lines could be distinguished. The binding profiles of these types, however, showed no correlation with origin of the cell lines or stage of the disease.

Distinguishing characteristics of a new neuroblastoma cell line

The characteristics of a new neuroblastoma cell line (MC-NB-1) established from the bone marrow of a 2-year-old male are described. Morphologically, the cells appear as flattened and epithelial-like or as small and spherical. Electron microscopy demonstrated microtubules and dense core secretory granules. The doubling time was approximately 35 hr. Isoenzyme patterns and catecholamine secretion indicated a human line of neuronal origin. The soft agar tumor colony forming system demonstrated drug resistance in vitro comparable to in vivo nonresponsiveness. The stemline karyotype of MC-NB-1 is 44,Y,del(1) (p22:), -4, -7, +del(7)(q22:), -16, +t(7;16)(16pter leads to 16q24::7q22 leads to 7q32), -17. Additionally, double-minute bodies were observed. However, no evidence of homogeneous staining regions (HSRs) were detected.

Monoclonal antibody UJ 127:11 detects a 220,000-240,000 kdal. glycoprotein present on a sub-set of neuroectodermally derived cells

The monoclonal antibody UJ 127-11 was raised following immunization of mice with human foetal brain and subsequent somatic cell hybridization of spleen cells with the mouse myeloma cell line P3-X63-Ag8-653. Studies on normal foetal and adult tissues show that, by indirect immunofluorescence, the antigen recognized by UJ 127:11 is restricted in its expression to cells of neural rather than glial origin. Neural tumours such as neuroblastoma, medulloblastoma and ganglioglioma (neural component) bind the monoclonal antibody whereas malignancies originating from glial cells do not bind UJ 127:11. Biochemically the monoclonal antibody has been shown to bind to a glycoprotein of 220,000-240,000 mol. wt. under reducing and non-reducing conditions. Despite similarities in the molecular weight between human fibronectin and the antigen recognized by UJ 127:11, they have different serological and biochemical characteristics, suggesting that the monoclonal antibody is not binding to either cell or plasma fibronectin.

Human Thy-1: expression on the cell surface of neuronal and glial cells

The Thy-1 antigen is a cell surface glycoprotein found in neural tissue of all mammalian species so far studied. The distribution and amount of this antigen has been measured on 4 human neuronal and 2 neuroglial cell lines and on fresh tumour cells of neuronal origin. In 3 out of 4 neuronal lines (LAN-1, TR14, CHP 212) more than 90% of cells were Thy-1+, however, LAN-1 cells showed only weak immunofluorescence and bore on average 2.4 times fewer molecules of Thy-1 per cell than those of either TR14 or CHP 212. The mean number of Thy-1 molecules per TR14 cell was shown to be approximately 2.25 x 10(5). In contrast, only 66% of cells in the fourth neuronal line (CHP 100) were Thy-1+, although these showed strong immunofluorescence. Both glial cell lines, UCH-203 and H314/123, showed strong Thy-1 immunofluorescence on more than 90% of cells. Similarly, with fresh neuronal tumour cells, although approximately 80% of tumours were Thy-1+ (essentially 100% of cells in these being positive) there were considerable differences in the intensity of labelling by immunofluorescence between different tumours. Such heterogeneity in cell lines and malignancy may reflect normal in vivo variation. Different phenotypes might therefore represent separate neural cell lineages, or simply differences in maturational status within a lineage. The very low frequency of Thy-1+ cells in normal bone marrow (less than 0.1% of nucleated cells) indicates that anti-Thy-1 antibodies may be valuable in both the diagnosis and subsequent treatment of neuroblastoma.

Distribution of Thy-1 in human brain: immunofluorescence and absorption analyses with a monoclonal antibody

A monoclonal antibody to human Thy-1 has been used to study the anatomical localization of Thy-1 in human brain and to quantitate the relative amounts of Thy-1 in different brain subregions. Quantitative absorption analyses using homogenates of carefully dissected brain subregions, together with an [125I]anti-immunoglobulin binding assay using brain homogenate as target, established that Thy-1 was present in large amounts throughout human brain, but the grey matter of cerebrum (cortical grey matter, caudate nucleus, putamen and thalamus) had 5-10 times as much Thy-1 as white matter. Grey matter of cerebellum (cerebellar cortex and dentate nucleus) also had higher amounts of Thy-1 than white matter, but the total amount of Thy-1 in cerebellum was less than in the cerebrum. Immunofluorescence studies gave interesting results and demonstrated in particular: (a) the outlining of some neuronal cell bodies and their processes (particularly the Purkinje cells of the cerebellar cortex) by spots of fluorescence; (b) staining of what appeared to be cell bodies of satellite cells in areas of grey matter; (c) granular staining in grey but not white matter; (d) staining of what appeared to be fibre tracts in the basal ganglia and thalamus, the tracts appearing duller than the surrounding grey matter of the nuclei; (e) staining of only some fibres in sciatic nerve; and (f) absence of staining of the adrenal gland.

Monoclonal antibody to ganglioside GQ discriminates between haemopoietic cells and infiltrating neuroblastoma tumour cells in bone marrow

An immunological approach has been sought for the identification of minimal metastatic spread of neuroblastoma to bone marrow. Here we describe the reactivity of the monoclonal antibody A2B5 to human neuroblastoma cell lines and fresh tumour tissue. This reagent, raised against chick retinal cells, reacts with all human neuroblastoma lines assayed although quantitative differences in antigenic expression exist between cultures. Analysis of tumour cells in heavily infiltrated bone marrow aspirates indicates that only 70% of the samples reacted with A2B5, suggesting that the heterogeneity seen in the expression of antigen on cell lines is paralleled in fresh tumour material. A2B5 showed no reactivity to either a panel of human leukaemic cell lines or normal human bone marrow, although reactivity to an occasional leukaemic marrow aspirate was detected. We suggest that A2B5 could form part of a panel of monoclonal reagents necessary for detecting metastatic spread of all neuroblastoma cells to bone marrow. Such a group of reagents may be useful therapeutically in a programmed of autologous bone marrow transplantation for the removal of tumour cells prior to reinfusion of haemopoietic cells to patients receiving high-dose chemotherapy.