New anti-GD2 monoclonal antibodies produced from gamma-interferon-treated neuroblastoma cells

The noradrenergic profile of plasma metanephrine in neuroblastoma patients is reproduced in xenograft mice models and arise from PNMT downregulation

Metanephrines (MNs; normetanephrine (NMN), metanephrine (MN) and methoxytyramine (MT)) detected in urine or plasma represent the best biomarker for neuroblastoma (NB) diagnosis, however the metabolism of both catecholamine (CAT) and MNs remains enigmatic in NB. Using patient-derived xenograft (PDX) models derived from primary NB cells, we observed that the plasma levels of MNs in NB-PDX-bearing mice were comparable as in patients. Interestingly, murine plasma displayed an elevated fraction of glucuronidated forms of MNs relative to human plasma where sulfonated forms prevail. In tumors, the concentration ranges of MNs and CAT and the expression levels of the main genes involved in catecholamine metabolism were similar between NB-PDX and human NB tissues. Likewise, plasma and intratumoral profiles of individual MNs, with increased levels of MT and NMN relative to MN, were also conserved in mouse models as in patients. We further demonstrated the downregulation of the Phenylethanolamine N-Methyltransferase gene in NB biopsies and in NB-PDX explaining this biochemical phenotype, and giving a rational to the low levels of epinephrine and MN measured in NB affected patients. Thus, our subcutaneous murine NB-PDX models not only reproduce the phenotype of primary NB tumors, but also the metabolism of catecholamine as observed in patients. This may potentially open new avenues in preclinical studies for the follow up of novel therapeutic options for NB through the quantification of plasma MNs.

The p140Cap adaptor protein as a molecular hub to block cancer aggressiveness

The p140Cap adaptor protein is a scaffold molecule encoded by the SRCIN1 gene, which is physiologically expressed in several epithelial tissues and in the neurons. However, p140Cap is also strongly expressed in a significant subset of cancers including breast cancer and neuroblastoma. Notably, cancer patients with high p140Cap expression in their primary tumors have a lower probability of developing a distant event and ERBB2-positive breast cancer sufferers show better survival. In neuroblastoma patients, SRCIN1 mRNA levels represent an independent risk factor, which is inversely correlated to disease aggressiveness. Consistent with clinical data, SRCIN1 gain or loss of function mouse models demonstrated that p140Cap may affect tumor growth and metastasis formation by controlling the signaling pathways involved in tumorigenesis and metastatic features. This study reviews data showing the relevance of SRCIN1/p140Cap in cancer patients, the impact of SRCIN1 status on p140Cap expression, the specific mechanisms through which p140Cap can limit cancer progression, the molecular functions regulated by p140Cap, along with the p140Cap interactome, to unveil its key role for patient stratification in clinics.

The SRCIN1/p140Cap adaptor protein negatively regulates the aggressiveness of neuroblastoma

Neuroblastoma is the most common extra-cranial pediatric solid tumor, responsible for 13–15% of pediatric cancer death. Its intrinsic heterogeneity makes it difficult to target for successful therapy. The adaptor protein p140Cap/SRCIN1 negatively regulates tumor cell features and limits breast cancer progression. This study wish to assess if p140Cap is a key biological determinant of neuroblastoma outcome. RNAseq profiles of a large cohort of neuroblastoma patients show that SRCIN1 mRNA levels are an independent risk factor inversely correlated to disease aggressiveness. In high-risk patients, CGH+SNP microarray analysis of primary neuroblastoma identifies SRCIN1 as frequently altered by hemizygous deletion, copy-neutral loss of heterozygosity, or disruption. Functional experiments show that p140Cap negatively regulates Src and STAT3 signaling, affects anchorage-independent growth and migration, in vivo tumor growth and spontaneous lung metastasis formation. p140Cap also increases sensitivity of neuroblastoma cells to doxorubicin and etoposide treatment, as well as to a combined treatment with chemotherapy drugs and Src inhibitors. Our functional findings point to a causal role of p140Cap in curbing the aggressiveness of neuroblastoma, due to its ability to impinge on specific molecular pathways, and to sensitize cells to therapeutic treatment. This study provides the first evidence that the SRCIN1/p140Cap adaptor protein is a key player in neuroblastoma as a new independent prognostic marker for patient outcome and treatment. Altogether, these data highlight the potential clinical impact of SRCIN1/p140Cap expression in neuroblastoma tumors, in terms of reducing cytotoxic effects of chemotherapy, one of the main issues for pediatric tumor treatment.

Impersonalized medicine

Research reported in this issue of Science Translational Medicine illustrates the benefits of short-term food withdrawal (fasting) in the treatment of cancer. Fasting exploited fundamental differences in the way tumor cells and normal cells respond to stress, simultaneously strengthening normal cell function and weakening tumor cell survival in the presence of toxic doses of chemotherapeutic drugs.

Functional sphere profiling reveals the complexity of neuroblastoma tumor-initiating cell model

Neuroblastoma (NB) is a neural crest-derived childhood tumor characterized by a remarkable phenotypic diversity, ranging from spontaneous regression to fatal metastatic disease. Although the cancer stem cell (CSC) model provides a trail to characterize the cells responsible for tumor onset, the NB tumor-initiating cell (TIC) has not been identified. In this study, the relevance of the CSC model in NB was investigated by taking advantage of typical functional stem cell characteristics. A predictive association was established between self-renewal, as assessed by serial sphere formation, and clinical aggressiveness in primary tumors. Moreover, cell subsets gradually selected during serial sphere culture harbored increased in vivo tumorigenicity, only highlighted in an orthotopic microenvironment. A microarray time course analysis of serial spheres passages from metastatic cells allowed us to specifically "profile" the NB stem cell-like phenotype and to identify CD133, ABC transporter, and WNT and NOTCH genes as spheres markers. On the basis of combined sphere markers expression, at least two distinct tumorigenic cell subpopulations were identified, also shown to preexist in primary NB. However, sphere markers-mediated cell sorting of parental tumor failed to recapitulate the TIC phenotype in the orthotopic model, highlighting the complexity of the CSC model. Our data support the NB stem-like cells as a dynamic and heterogeneous cell population strongly dependent on microenvironmental signals and add novel candidate genes as potential therapeutic targets in the control of high-risk NB.

Metastatic melanomas express inhibitory low affinity fc gamma receptor and escape humoral immunity

Our research, inspired by the pioneering works of Isaac Witz in the 1980s, established that 40% of human metastatic melanomas express ectopically inhibitory Fc gamma receptors (FcγRIIB), while they are detected on less than 5% of primary cutaneous melanoma and not on melanocytes. We demonstrated that these tumoral FcγRIIB act as decoy receptors that bind the Fc portion of antimelanoma IgG, which may prevent Fc recognition by the effector cells of the immune system and allow the metastatic melanoma to escape the humoral/natural immune response. The FcγRIIB is able to inhibit the ADCC (antibody dependent cell cytotoxicity) in vitro. Interestingly, the percentage of melanoma expressing the FcγRIIB is high (70%) in organs like the liver, which is rich in patrolling NK (natural killer) cells that exercise their antitumoral activity by ADCC. We found that this tumoral FcγRIIB is fully functional and that its inhibitory potential can be triggered depending on the specificity of the anti-tumor antibody with which it interacts. Together these observations elucidate how metastatic melanomas interact with and potentially evade humoral immunity and provide direction for the improvement of anti-melanoma monoclonal antibody therapy.

Chemokines in neuroectodermal cancers: the crucial growth signal from the soil

Although chemokines and their receptors were initially identified as regulators of cell trafficking during inflammation and immune response, they have emerged as crucial players in all stages of tumor development, primary growth, migration, angiogenesis, and establishment as metastases in distant target organs. Neuroectodermal tumors regroup neoplasms originating from the embryonic neural crest cells, which display clinical and biological similarities. These tumors are highly malignant and rapidly progressing diseases that disseminate to similar target organs such as bone marrow, bone, liver and lungs. There is increasing evidence that interaction of several chemokine receptors with corresponding chemokine ligands are implicated in the growth and invasive characteristics of these tumors. In this review we summarize the current knowledge on the role of CXCL12 chemokine and its CXCR4 and CXCR7 receptors in the progression and survival of neuroectodermal tumors, with particular emphasis on neuroblastoma, the most typical and enigmatic neuroectodermal childhood tumor.

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

PURPOSE

We previously generated a mouse monoclonal antibody (mAb) specific for the tumor-associated GD2 ganglioside antigen. Here, we describe the development of a chimeric anti-GD2 mAb for more effective tumor immunotherapy.

EXPERIMENTAL DESIGN

We cloned the cDNA encoding the immunoglobulin light and heavy chains of the 60C3 anti-GD2 mAb, and constructed chimeric genes by linking the cDNA fragments of the variable regions of the murine light and heavy chains to cDNA fragments of the human kappa and gamma1 constant regions, respectively.

RESULTS

The resultant chimeric anti-GD2 mAb, c.60C3, showed identical binding affinity and specificity to that of its murine counterpart. Both c.60C3 and 60C3 were rapidly internalized by tumor cells at 37 degrees C. When human serum and human natural killer cells were used as effectors in complement-mediated cytotoxicity and antibody-dependent cell cytotoxicity, respectively, c.60C3 was more effective in killing GD2-expressing tumor cells. However, c.60C3 was ineffective at inducing cell death by apoptosis, although binding of 60C3 induced apoptotic death in vitro. In an in vivo, GD2-expressing, syngeneic tumor model, i.v. injection of c.60C3, but not of 60C3, significantly suppressed tumor growth in mice (P<0.0005).

CONCLUSION

Immune effector functions mediated by this antibody and its potentially reduced immunogenicity make chimeric c.60C3 a promising therapeutic agent against neuroectodermic tumors.

The FN13 peptide inhibits human tumor cells invasion through the modulation of αvβ3 integrins organization and the inactivation of ILK pathway

We report the effect of the stable expression of a 13 amino acid human fibronectin (FN) peptide (FN13) on the organization of the FN extracellular matrix (ECM) and of FN integrin receptors (FNRs), in relationship with the inhibition of cellular invasion, in three FN-ECM defective human tumor-derived cell lines: SK-Hep1C3, hepatoma, ACN, neuroblastoma, and SK-OV-3, ovary carcinoma. All these cell lines stably expressing the FN13 peptide, organized an FN-ECM, disorganized alpha v beta 1 integrins and inactivated the ILK pathway, with the loss of secretion of MMP-9. This was associated with the inhibition of cell invasion in Matrigel matrix only in SK-Hep1C3 and ACN, but not in SK-OV-3 cells. Analysis of the integrin receptors organization showed that the FN13 expressing cells SK-Hep1C3 and ACN organized alpha v beta 3 integrins, whereas SK-OV-3 organized alpha v beta 5 dimers. The functional block of alpha v beta 5 integrins, with an inactivating anti-alpha v beta 5 antibody, led to the induction of alpha v beta 3 integrins also in SK-OV-3 cells, and to the inhibition of cell invasion. These data show that in the human tumor cells studied FN13 inhibits the in vitro invasion through the dissociation of alpha v beta 1 dimers, leading to ILK pathway inactivation, only when the organization of alpha v beta 3 integrins is induced in the plasma membrane.

Modulation of tumor growth by inhibitory Fc(gamma) receptor expressed by human melanoma cells

The efficacy of anti-tumor IgG reflects the balance between opposing signals mediated by activating and inhibitory Fc(gamma) receptors (Fc(gamma)Rs) expressed by effector cells. Here, we show that human malignant melanoma cells express the inhibitory low-affinity Fc(gamma) receptor Fc(gamma)RIIB1 in 40% of tested metastases. When melanoma cells were grafted in nude mice, a profound inhibition of Fc(gamma)RIIB1 tumor growth that required the intracytoplasmic region of the receptor was observed. IgG immune complexes (ICs) may be required for this inhibition, since sera from nude mice bearing tumors contained IgG that decreased the proliferation of Fc(gamma)RIIB1-positive cells in vitro, and tumor development of Fc(gamma)RIIB1-positive melanoma lines was not inhibited in antibody-defective severe combined immunodeficiency (SCID) mice. Passive immunization of SCID mice with anti-ganglioside G(D2) antibody resulted in significant inhibition of growth of Fc(gamma)RIIB1-positive tumors in an intracytoplasmic-dependent manner. Altogether, these data suggest that human melanoma cells express biologically active inhibitory Fc(gamma)RIIB1, which regulates their development upon direct interaction with anti-tumor antibodies. Therefore, Fc(gamma)R expression on human tumors may be one component of the efficacy of antibody-mediated therapies, and Fc(gamma)R-positive tumors could be the most sensitive candidates for such treatments.

Targeting of G(D2)-positive tumor cells by human T lymphocytes engineered to express chimeric T-cell receptor genes

Genetic engineering of human T lymphocytes to express tumor antigen-specific chimeric immune receptors is an attractive means for providing large numbers of effector cells for adoptive immunotherapy while bypassing major mechanisms of tumor escape from immune recognition. We have applied this strategy to the targeting of a G(D2)-positive tumor, neuroblastoma, which is the commonest extracranial solid tumor of childhood. Chimeric immune receptors were generated by joining an extracellular antigen-binding domain derived from either of the 2 ganglioside G(D2)-specific antibodies sc7A4 and sc14.G2a to a cytoplasmic signaling domain. The variable domains of hybridoma antibody 14.G2a were cloned and selected using a phage display approach. Upon coincubation with G(D2)-expressing tumor cell targets, human T lymphocytes transduced with recombinant retroviruses encoding chimeric receptors based on sc14.G2a, but not sc7A4, secreted significant levels of cytokines in a pattern comparable to the cytokine response obtained by engagement of the CD3 receptor. T cells transduced with the sc14.G2a-based chimeric T-cell receptors also displayed specific lysis of G(D2)-positive neuroblastoma cells, which was blocked in the presence of monoclonal antibody 14.G2a. In the absence of nonspecific stimulation of transduced cells, their functionality declined over time and antigenic stimulation of the chimeric receptor alone did not induce commitment to proliferation. These results support the feasibility of redirecting human T lymphocytes to a tumor-associated ganglioside epitope but emphasize that successful chimeric receptor-mediated adoptive immunotherapy will require additional strategies that overcome functional inactivation of gene-modified primary T lymphocytes.

In vivo induction of functional Fc gammaRI (CD64) on neutrophils and modulation of blood cytokine mRNA levels in cancer patients treated with G-CSF (rMetHuG-CSF)

Neutrophils from 13 children who received G-CSF for the collection of peripheral blood progenitors while they were in haematological steady state were studied at various times after G-CSF injection for Fc gammaR expression (Fc gammaRI or CD64, Fc gammaRII or CD32, and Fc gammaRIII or CD16) and for their ability to exert antibody-dependent cell cytotoxicity (ADCC) through Fc gammaRI. Changes in IFNgamma, IL8, IL10, MCP1 and TNF alpha mRNA levels in peripheral blood cells were also studied 4 h and 24 h after the first G-CSF injection. Fc gammaRI expression increased strongly after 24 h and then remained at the same level throughout treatment. In contrast, Fc gammaRIII expression sharply decreased at day 1 and diminished even further thereafter. No change in Fc gammaRII was observed. ADCC exerted by neutrophils through Fc gammaRI started to increase after 24 h with the peak level at day 5. Cytokine mRNA analyses indicated a reproducible and strong increase of IL8 mRNA (11/13 children) after 24 h, whereas the changes in the mRNA levels of the other cytokines tested were more heterogenous (TFNgamma: three; IL10: six; MCP1: five: TNF alpha: four, of the 13 children). Therefore this study opens the way to an optimized therapeutic schedule for the combined use of G-CSF and monoclonal antibodies in adjuvant immuno-intervention.

Variable region gene segments of nine monoclonal antibodies specific to disialogangliosides (GD2, GD3) and their O-acetylated derivatives

Despite the weak immunogenicity of gangliosides, a limited number of highly specific murine monoclonal antibodies (MAbs) were elicited. This study investigated the reactivity and the structure of the VH and V kappa genes of nine hybridomas obtained from independent fusions producing antibodies against disialogangliosides GD2 and GD3 and their O-acetylated derivatives. These antibodies depended on four types of V kappa genes. They were also encoded by VH genes of the J558 family (5 out of 9) and occasionally by VH genes of the S107, 7183, and 3609 families, rearranged with a variety of DH and JH genes. The 8B6 and 7H2 MAbs specific for GD2-O-acetylated, respectively, used the VH gene of the S107 and 7183 families. The length of H chain CDR3 ranged from 8 to 11 amino acids. A set of S107 and 3609 germline genes closed from A/J murine fetal liver and matched with the VH segment of hybridomas 8B6 and 10B8 revealed somatic mutations. Although the relative number of sequences does not preclude any formal conclusions regarding the preferential use of V genes in the immune recognition of carbohydrate structures, our results clearly indicate that MAbs directed to very similar structures as GD2 and GD3 were encoded by different VH and V kappa genes.

Generation and characterization of a mouse single-chain antibody fragment specific for disialoganglioside (GD2)

Anti-disialoganglioside (GD2) monoclonal antibodies (MAbs) have been used in vivo for immunolocalization and in phase I and II trials to target disseminated neuroblastoma, the most common extracranial solid tumor in children. However, the efficacy of these first-generation MAbs is likely to be improved by using engineered anti-GD2 antibodies. The generation of single-chain antibody fragments (scFv) could be very helpful as these molecules can be further modified to produce recombinant molecules with pre-defined properties such as immunotoxins, chimeric, or bispecific antibodies. Thus, a scFv directed against GD2 (scFv 7A4) was cloned, sequenced, and expressed. Its binding properties were characterized and compared to that of the parental MAb 7A4. Nucleotide sequence analysis of the scFv 7A4 indicated that its VH region belongs to the V region IIID subgroup and the V kappa to the V region II subgroup. The scFv 7A4 bound to GD2+ neuroblastoma cell lines but not to GD2- cell lines or to GD2- cells isolated from peripheral blood. ELISA and thin-layer chromatography (TLC) indicated that it retained the anti-GD2 specificity, and exhibited a slight cross-reaction with GD3 as the parental MAb. This scFv makes it possible to develop new useful reagents through genetic engineering for adjuvant tumor therapy.

Structural characterization and in vivo immunosuppressive activity of neuroblastoma GD2

Shedding of neuroblastoma gangliosides is positively correlated with tumour progression in patients with neuroblastoma. In assessing the biological activity of these ganglioside molecules, we recently found that total human neuroblastoma gangliosides inhibit cellular immune responses. Here, we have studied the major neuroblastoma ganglioside, GD2. GD2 was purified by high performance liquid chromatography and structurally characterized by mass spectrometry. Immunoregulatory effects of GD2 in vivo were then determined in an established murine model. GD2 significantly downregulated the local cellular immune response to an allogeneic cell challenge; the usual increase in mass of the lymph node draining the injection site was reduced by 88%, from 1.52 to 0.19 mg (control versus GD2-treated mice; p < 0.01). In parallel, lymphocyte recovery from each node was also reduced from 2.4 to 1.2 x 10(6) cells, and lymphocyte DNA synthesis was reduced to half of the control level. These results show that certain shed tumour gangliosides, such as GD2, function as intercellular signalling molecules, downregulate the cellular immune response, and may thereby enhance tumour formation and progression.

In vivo targeting of human neuroblastoma xenograft by anti-GD2/anti-Fc gamma RI (CD64) bispecific antibody

Antidisialoganglioside (GD2) monoclonal antibodies can target in vitro and in vivo neuroblastoma cells. However, their in vivo use is limited by the presence of high levels of circulating IgG which hamper the recruitment of effector cells through the high affinity Fc gamma RI (CD64). A bispecific Fab' x Fab' antiGD2/antiFc gamma RI antibody (7A4 bis 22), which binds outside the IgG binding site of Fc gamma RI, was therefore developed. This antibody binds both human GD2+ neuroblastoma and Fc gamma RI+ activated macrophages in vitro. It can localise a GD2 positive neuroblastoma xenografted on Nu/Nu mice. Scintigraphy tumour/muscle ratios showed that targeting with this antibody has an excellent selectivity for the tumour over normal tissues. Furthermore, although its whole body clearance is more rapid than that of the 7A4 parental antibody over the first 48 h, its selective tumour uptake is similar, as shown by immunoscintigraphy imaging. Thus, such a bispecific antibody may represent an efficient tool for in vivo therapy of neuroblastoma through its ability to recruit Fc gamma RI+ effector cells even in presence of circulating IgG and to bind concomitantly GD2+ tumour cells.

Characterization of gangliosides from normal and osteoarthritic human articular cartilage

OBJECTIVE

Glycosphingolipids (GSLs) are biologically active molecules in the physiology and pathology of cells. Since changes in GSLs might be associated with the impaired metabolism of articular cartilage in osteoarthritis (OA), we investigated gangliosides from normal and OA human cartilage.

METHODS

OA and control cartilage was obtained from patients with hip OA and femoral neck fracture, respectively. Gangliosides were extracted and quantified by determining their lipid-bound sialic acid concentration. Major gangliosides were identified by immuno-detection on thin-layer plates, purified by high performance liquid chromatography, and analyzed for their carbohydrate, fatty acid, and long-chain base composition.

RESULTS

The total ganglioside content of OA cartilage was decreased by 40% (per mg of DNA). Major gangliosides, GM3 and GD3, separated into 3 on thin-layer chromatography bands. All were decreased except for the lowest migrating band of GM3, which was increased 5-fold. This ganglioside had the same carbohydrate moiety and fatty acids as the other two, but differed by a long-chain base composed mainly of C20-sphingosine.

CONCLUSION

OA cartilage is characterized by a decrease in all gangliosides except GM3, which demonstrates a large increase in the lowest band. These results indicate that there are changes in the biochemical composition of chondrocyte membranes in OA. The causes and roles of these changes remain to be determined.

Shedding of GD2 ganglioside in patients with retinoblastoma

Retinoblastoma is a rare tumor of the young child with an intraocular localization that leads to certain problems of diagnosis. With the aim of defining a biochemical marker--which is still lacking for this disease--the gangliosides of a pool of fresh retinoblastoma tumors were analyzed. The ganglioside pattern was shown to have GM3, GM2, GM1, GD3, GD2, GD1b and GT1b as the major components. The occurrence of a high concentration of GD2 in the tumors led us to investigate the possibility of changes in the level of GD2 in the sera of retinoblastoma patients, using quantitative immunostaining with GD2-specific mouse monoclonal antibodies (MAbs). In 9 out of 10 tumor-bearing patients, the serum level of GD2 ganglioside was significantly higher than the average value found in normal individuals. A 2-year follow-up of patients showed that successful treatment resulted in a rapid decrease in the serum level of GD2 down to the normal range, from which a subsequent elevation was seen only in relapsing patients. Although the clinical study needs further development, the results obtained to date suggest that GD2 is shed in the serum of tumor-bearing patients and that the level of GD2 could be a potential serum marker of human retinoblastoma.

Monoclonal antibodies against neuroblastoma. Production and preliminary characterization of their specificity

Neuroblastoma (NB) is a common childhood tumor that originates from neuroblasts of the neural crest. In this paper we will describe the production of murine monoclonal antibodies (mAbs) to human NB cell lines. The hybridomas were selected by ELISA and immunofluorescence for antibody binding to multiple human neuroblastoma cultured cell lines, but not to hematopoietic cells and leukemic cells. The mAbs were characterized in terms of their ability to bind to human cell lines and tissues. The IgG2a and IgG2b mAbs may prove useful in the diagnosis of therapy of neuroblastoma.

Humoral immune response in disease-free advanced melanoma patients after vaccination with melanoma-associated gangliosides. EORTC Cooperative Melanoma Group

Several studies have shown that melanoma-associated gangliosides are immunogenic in melanoma patients and that antibodies against them have a favorable prognostic effect. Our study aims at characterizing the humoral immune response in disease-free, advanced melanoma patients vaccinated with a total ganglioside fraction extracted from pooled metastases of human melanoma, containing as major gangliosides GM3 and GD3, and as minor ones GM2 and GD2. Prior to vaccination, all patients were made disease-free by surgical removal of skin, lymph-node or other distant metastases. Repeated vaccinations were carried out intradermally with gangliosides either in the native form in buffered solution, or in the form of liposomes. Serum samples were collected at regular intervals and assayed by ELISA for the presence of specific IgG and IgM antiganglioside antibodies. Selected samples were tested by immunostaining on thin-layer plates to specify the ganglioside species involved in the reactivity. Out of 32 evaluable patients, 17 presented a significant increase in antibody titer, mostly of the IgG isotype, which was maximal between 2 and 4 months after starting injections of gangliosides, and gradually disappeared within 1 year. No significant difference could be seen between the group of 20 patients treated with native gangliosides and the group of 12 vaccinated with the gangliosides in liposomes. All gangliosides seemed to be immunogenic, but GM2 and GD2 were somewhat more reactive. The disease-free intervals for the patients who showed an antibody response to the treatment were significantly higher (p less than 0001) than those of the non-responding group, as compared by the Kaplan-Meier method.

Imaging and therapy with monoclonal antibodies in non-hematopoietic tumors

Although radiolabelled monoclonal antibodies are useful in tumor imaging, in our opinion their most important role is in the evaluation of the capacity of newly developed monoclonal antibodies to localize in tumors specifically. Intravenous injections of monoclonal antibody fragments, labelled with beta-emitting radionuclides, can completely eradicate large human colon carcinoma xenografts in nude mice whereas this is not achieved by unconjugated monoclonal antibodies. New strategies are being developed to make radioimmunotherapy applicable to carcinoma patients.

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.

Polymorphic effects of exogenous gangliosides on antigen-induced lymphoproliferation and generation of MHC unrestricted cell mediated cytotoxicity

Cell membrane gangliosides have been shown to be involved in a number of biological processes including cell adhesion, signal transduction and ligand receptor interactions. In this paper we analyzed the effects of a mixture of bovine brain gangliosides, currently in clinical use, on cell mediated immune responses in vitro. We show here that exogenous gangliosides inhibit mitogen and alloantigen induced lymphoproliferation. On the other hand effects on antigen induced blastogenesis were exquisitely dose dependent in that while high doses of gangliosides inhibited lymphoproliferation, probably by interfering in interleukin 2 receptor interactions, lower doses significantly enhanced antigen induced responsiveness. We also report that gangliosides inhibit the generation of lymphokine activated killer cells. Altogether, these data underline the immunoregulatory potential and the polymorphism of effects of exogenous gangliosides.

Epidermal growth factor responsiveness of a new human neuroblastoma cell line

A human neuroblastoma cell line, CA-2E, has been established from a bone-marrow aspirate of a 16-month-old boy with progressive disease. The karyotype and antigen phenotype of the cells correspond to those of a neuroblastoma. This cell line grows well in liquid cultures supplemented with 5% fetal calf serum; conversely, colony formation in semi-solid medium by cells from early passages is dependent upon exogenous EGF. With time in continuous culture, the cloning efficiency in the absence of EGF increases, but the line remains sensitive to EGF, as evidenced by an enhancement of the number and size of colonies. A relative dependence upon EGF in liquid cultures has also been clearly demonstrated by limiting the concentration of serum. Long-term (over 2 weeks) treatment with EGF results in a decreased rate of proliferation, a decreased proportion of clonogenic cells, and the appearance of flat, epithelial-type cells. In some experiments, EGF also has a remarkable effect in inducing neurite outgrowth and process branching. Our results suggest that EGF may have both proliferation- and differentiation-inducing effects on this neuroblastoma cell line. We have also shown that EGF induces increased proliferation in 7 out of 8 other human neuroblastoma cell lines. Functional response of neuroblastoma cells to EGF appears to be a general phenomenon which may be related to a block in the normal maturation pathway of the neural crest cells from which this tumor originates.