A monoclonal antibody (ERIC-1), raised against retinoblastoma, that recognizes the neural cell adhesion molecule (NCAM) expressed on brain and tumours arising from the neuroectoderm

Tumoricidal Activity and Side Effects of Radiolabeled Anti-NCAM [131I]-Iodine-ERIC1 in Neuroblastoma-Bearing Mice

Preliminary studies on a radioactive antibody against the neural cell adhesion molecule (NCAM) demonstrated a significant accumulation of [131I]I-ERIC1 in neuroblastoma tumor cells in mice. This study aims to validate the therapeutic efficacy and potential adverse effects of these radioactive immunoconjugates (RICs) in neuroblastoma-bearing mice. To determine the highest tolerated dose, healthy SCID mice received 1 to 22 MBq of [131I]I-ERIC1, with the survival time measured. Tumor response was evaluated by administering 0.8 to 22 MBq of [131I]I-ERIC1 to neuroblastoma-bearing mice and assessing tumor size and systemic toxicity through body weight, blood counts, and survival. It was observed that doses up to approximately 3 MBq per animal (150 MBq/kg) were well tolerated, whereas higher doses resulted in systemic toxicity and death. The neuroblastomas exhibited a dose-dependent response, with optimal therapeutic efficacy achieved at 1.8-2.5 MBq per animal (90-125 MBq/kg), significantly extending survival by a factor of five. The antibody ERIC1 is a promising vehicle for the transport of beta emitters into NCAM-positive tumor tissue. An optimal dosage of the [131I]I-ERIC1 antibody can be established with a balance of tumor-static effects and adverse effects, resulting in a marked extension of survival time.

Localization and Tumor Growth Inhibition of I-131-Labeled Monoclonal Antibody ERIC1 in a Subcutaneous Xenograft Model of Small Cell Lung Cancer in SCID Mice

This study evaluates the efficacy of [131I]I-ERIC1 in targeting and inhibiting the growth of SCLC tumors in mice, focusing on tumor accumulation and regression and potential side effects. NCAM-positive NCI-H69 SCLC cells were implanted in CB 17 SCID mice, and [131I]I-ERIC1 biokinetics were measured in organs and tissues at four post-injection time points (24, 72, 96, and 120 h). The experimental series compared tumor growth, survival, and changes in blood counts among three treatment groups (1, 2, or 3 MBq) and a control group, with treatments initiated either two or five days post implantation. [131I]I-ERIC1 was synthesized with >95% radiochemical purity and a specific activity of 15 TBq/mmol. Tumor activity peaked at 31.5 ± 6.6% ID/g after four days, demonstrating significant antitumor efficacy, which resulted in sustained remission and extended survival. Hematological toxicity was observed, with the optimal dose identified as 2 MBq per animal administered two days post implantation. [131I]I-ERIC1 shows promise as a theranostic agent for personalized cancer treatment by effectively targeting SCLC tumors with manageable side effects. However, further studies are required to optimize dosing strategies and minimize toxicity.

PEGylated dendritic polyglycerol conjugate targeting NCAM-expressing neuroblastoma: Limitations and challenges

Neural cell adhesion molecule (NCAM) is found to be a stem-cell marker in several tumor types and its overexpression is known to correlate with increased metastatic capacity. To combine extravasation- and ligand-dependent targeting to NCAM overexpressing-cells in the tumor microenvironment, we developed a PEGylated NCAM-targeted dendritic polyglycerol (PG) conjugate. Here, we describe the synthesis, physico-chemical characterization and biological evaluation of a PG conjugate bearing the mitotic inhibitor paclitaxel (PTX) and an NCAM-targeting peptide (NTP). PG-NTP-PTX-PEG was evaluated for its ability to inhibit neuroblastoma progression in vitro and in vivo as compared to non-targeted derivatives and free drug. NCAM-targeted conjugate inhibited the migration of proliferating endothelial cells, suggesting it would be able to inhibit tumor angiogenesis. The targeting conjugate provided an improved binding and uptake on IMR-32 cells compared to non-targeted control. However, these results did not translate to our in vivo model on orthotopic neuroblastoma bearing mice.

Ossifying Fibromyxoid Tumor May Express CD56 and CD99: A Case Report

Ossifying fibromyxoid tumor (OFMT) is an uncommon soft tissue neoplasm characterized by a combination of myxoid and/or fibrous stroma with areas of ossification. Although most authors postulate a neuroectodermal origin for this peculiar tumor, there is no agreement in the literature regarding its histogenesis. In this article, we present the immunohistochemical findings of a case of a 39-year-old white male with an OFMT of the soft tissue in the mandibular region. The tumor was positive to S-100 protein, glial fibrillary acidic protein, CD99, CD56 and negative to smooth muscle actin, cytokeratins AE1/AE3, epithelial membrane antigen, and CD68. To the best of our knowledge, this is the first case reported to be positive to CD56 and CD99. Immunoreactivity to these two antibodies, together with reactivity for S-100 protein and glial fibrillary acidic protein, suggests that OFMT is of a neuroectodermal origin. In our opinion, in the absence of reactivity to at least one neuroectodermal marker one should seriously question a diagnosis of OFMT.

Initial testing (Stage 1) of the antibody-maytansinoid conjugate, IMGN901 (Lorvotuzumab mertansine), by the pediatric preclinical testing program

BACKGROUND

IMGN901 (lorvotuzumab mertansine) is an antibody-drug conjugate composed of a humanized antibody that specifically binds to CD56 (NCAM, neural cell adhesion molecule) and that is conjugated to the maytansinoid, DM1 (a microtubule targeting agent).

PROCEDURES

IMGN901 and DM1-SMe (unconjugated DM1 as a mixed disulfide with thiomethane to cap its sulfhydryl group) were tested in vitro at concentrations ranging from 0.01 nM to 0.1 µM and 0.3 pM to 3 nM, respectively. IMGN901 was tested against a subset of PPTP solid tumor xenografts focusing on those with high CD56 expression.The combination of IMGN901 with topotecan was also evaluated.

RESULTS

Neuroblastoma models expressed CD56 at or above the median expression level for all PPTP xenografts and cell lines. Neuroblastoma cell lines demonstrated relatively low sensitivity to DM1-SMe compared to other cell lines, but the sensitivity of neuroblastoma cell lines to IMGN901 was comparable to that of non-neuroblastoma cell lines. In vivo, objective responses were observed in 9 of 24 (38%) models including, three of seven neuroblastoma xenografts, and two of seven rhabdomyosarcoma xenografts. All xenografts with objective responses showed homogeneous high-level staining by IHC for CD56, but not all xenografts with homogenous high-level staining had objective responses. Combined with topotecan, IMGN901 demonstrated therapeutic enhancement against two of four neuroblastoma models.

CONCLUSIONS

IMGN901 has anti-tumor activity against some CD56 expressing pediatric cancer models. High expression of CD56 is a biomarker for in vivo response, but resistance mechanisms to IMGN901 in some high CD56 expressing lines need to be defined.

Functional inhibition of transitory proteins by intrabody-mediated retention in the endoplasmatic reticulum

Intrabodies are recombinantly expressed intracellular antibody fragments that can be used to specifically bind and inhibit the function of cellular proteins of interest. Intrabodies can be targeted to various cell compartments by attaching an appropriate localization peptide sequence to them. An efficient strategy with a high success rate is to anchor intrabodies in the endoplasmatic reticulum where they can inhibit transitory target proteins by binding and preventing them to reach their site of action. Intrabodies can be assembled from antibody gene fragments from various sources into dedicated expression vectors. Conventionally, antibody cDNA sequences are derived from selected hybridoma cell clones that express antibodies with the desired specificity. Alternatively, appropriate clones can be isolated by affinity selection from an antibody in vitro display library. Here an evaluation of endoplasmatic reticulum targeted intrabodies with respect to other knockdown approaches is given and the characteristics of various intrabody expression vectors are discussed. A step by step protocol is provided that was repeatedly used to construct intrabodies derived from diverse antibody isotypes producing hybridoma cell clones. The inactivation of the cell surface receptor neural cell adhesion molecule (NCAM) by a highly efficacious novel endoplasmatic reticulum-anchored intrabody is demonstrated.

Hepatocellular carcinoma with progenitor cell features distinguishable by the hepatic stem/progenitor cell marker NCAM

We analyzed hepatocellular carcinoma (HCC) with progenitor cell features using hepatic stem/progenitor cell marker neural cell adhesion molecule (NCAM). Approximately 8.3% of the operated HCC cases expressed NCAM, and 22.3% of the HCC patients had soluble NCAM levels >1000ng/ml (the "highly soluble" NCAM group). Soluble NCAM status was a significant independent factor predictive of long-term survival in patients with HCC, and high levels of soluble NCAM were significantly related to intrahepatic metastasis. The 140-kDa NCAM isoform was specifically detected in the "highly soluble" NCAM group of HCC patients andits related signals are potential drug targets for NCAM+ HCC.

Absence of polysialylated NCAM is an unfavorable prognostic phenotype for advanced stage neuroblastoma

Background

The expression of a neural crest stem cell marker, polysialic acid (polySia), and its main carrier, neural cell adhesion molecule (NCAM), have been detected in some malignant tumors with high metastatic activity and unfavorable prognosis, but the diagnostic and prognostic value of polySia-NCAM in neuroblastoma is unclear.

Methods

A tumor tissue microarray (TMA) of 36 paraffin-embedded neuroblastoma samples was utilized to detect polySia-NCAM expression with a polySia-binding fluorescent fusion protein, and polySia-NCAM expression was compared with clinical stage, age, MYCN amplification status, histology (INPC), and proliferation index (PI).

Results

PolySia-NCAM-positive neuroblastoma patients had more often metastases at diagnosis, and polySia-NCAM expression associated with advanced disease (P = 0.047). Most interestingly, absence of polySia-NCAM-expressing tumor cells in TMA samples, however, was a strong unfavorable prognostic factor for overall survival in advanced disease (P = 0.0004), especially when MYCN was not amplified. PolySia-NCAM-expressing bone marrow metastases were easily detected in smears, aspirates and biopsies.

Conclusion

PolySia-NCAM appears to be a new clinically significant molecular marker in neuroblastoma, hopefully with additional value in neuroblastoma risk stratification.

Universal expression of cell adhesion molecule NCAM in neuroblastoma in contrast to L1: implications for different roles in tumor biology of neuroblastoma?

PURPOSE

Neuroblastoma is a biological, genetic and morphological heterogeneous tumor with a variable clinical course. NCAM is a cell adhesion molecule belonging to the immunoglobulin superfamily with structural similarities to cell adhesion molecule L1. The aim of this study was to determine the expression of NCAM in neuroblastoma and to compare the results to the findings of a previous study which examined L1 expression in the same group of patients.

MATERIALS AND METHODS

NCAM expression was investigated on a tissue array with 66 surgically resected neuroblastoma samples by immunohistochemistry with a monoclonal antibody clone 1B6 and peroxidase method.

RESULTS

Strong expression of NCAM was detected in all of the 66 (100%) neuroblastoma tumors in contrast to L1 which was not expressed in all tumors.

CONCLUSION

In contrast to L1, which was found to predict favorable outcome, NCAM is universally expressed in neuroblastoma. Therefore NCAM represents a marker for neuroblastomas irrespectively of their stages whereas L1 as an indicator for developing neuronal cells seems to identify more mature stages of this tumor. The high grade of NCAM expression might present a prerequisite for establishment of antibody-based therapies.

Site-directed antibodies to low-voltage-activated calcium channel CaV3.3 (alpha1I) subunit also target neural cell adhesion molecule-180

Synthetic peptides of defined amino acid sequence are commonly used as unique antigens for production of antibodies to more complex target proteins. We previously showed that an affinity-purified, site-directed polyclonal antibody (CW90) raised against a peptide antigen (CNGRMPNIAKDVFTKM) anticipated to be specific to a T-type voltage-dependent Ca(2+) channel subunit identified recombinant rat alpha1I/Ca(V)3.3 and two endogenous mouse proteins distinct in their developmental expression and apparent molecular mass (neonatal form 260 kDa, mature form 190 kDa) [Yunker AM, Sharp AH, Sundarraj S, Ranganathan V, Copeland TD, McEnery MW (2003) Immunological characterization of T-type voltage-dependent calcium channel Ca(V)3.1 (alpha 1G) and Ca(V)3.3 (alpha 1I) isoforms reveal differences in their localization, expression, and neural development. Neuroscience 117:321-335]. In the present study, we further characterize the biochemical properties of the CW90 antigens. We show for the first time that recombinant alpha1I/Ca(V)3.3 is modified by N-glycosylation. Using peptide:N-glycosidase F (PNGase F), an enzyme that removes polysaccharides attached at Asn residues, and endoneuraminidase-N (Endo-N), which specifically removes polysialic acid modifications, we reveal that differential glycosylation fully accounts for the large difference in apparent molecular mass between neonatal and adult CW90 antigens and that the neonatal form is polysialylated. As very few proteins are substrates for Endo-N, we carried out extensive analyses and herein present evidence that CW90 reacts with recombinant alpha1I/Ca(V)3.3 as well as endogenous neural cell adhesion molecule-180 (NCAM-180). We demonstrate the basis for CW90 cross-reactivity is a five amino acid epitope (AKDVF) present in both alpha1I/Ca(V)3.3 and NCAM-180. To extend these findings, we introduce a novel polyclonal anti-peptide antibody (CW678) that uniquely recognizes NCAM-180 and a new antibody (CW109) against alpha1I/Ca(V)3.3. Western blot analyses obtained with CW678, CW109 and CW90 on a variety of samples confirm that the endogenous CW90 signals are fully attributed to the two developmental forms of NCAM-180. Using CW678, we present novel data on differentiation-dependent NCAM-180 expression in human neuroblastoma IMR32 cells. These results strongly suggest the need for careful analyses to validate anti-peptide antibodies when targeting membrane proteins of low abundance.

The Fibroblast Growth Factor Receptor Acid Box Is Essential for Interactions with N-Cadherin and All of the Major Isoforms of Neural Cell Adhesion Molecule

Interactions between the neural cell adhesion molecules NCAM and N-cadherin with the fibroblast growth factor receptor (FGFR) are important for a number of developmental events and have also been implicated in tumor progression. The factors regulating these interactions are not known. We have used co-immunoprecipitation and co-clustering paradigms to show that both adhesion molecules can interact with the 3Ig IIIC isoform of the FGFR1 in a number of cell types. Interestingly, whereas the interaction can be seen over most of the cell surface, it is not seen at points of cell-cell contact where the adhesion molecules accumulate at stable junctions. We also demonstrate for the first time that all of the major isoforms of NCAM can interact with the FGFR. Using deletion mutagenesis we have found that the adhesion molecule/FGFR interaction can withstand the removal of most of any one of the FGFR immunoglobulin-like domains (D1-D3). In contrast, the FGFR interaction with N-cadherin and NCAM (but not FGF) is absolutely dependant on the presence of the acid box motif that can be found in the linker region between D1 and D2. As this motif can be spliced out of all four FGFRs, it suggests that this is one mechanism that can regulate the interaction of the receptor with different ligand classes.

Localization of 131I-labelled monoclonal antibody ERIC1 in a subcutaneous xenograft model of neuroblastoma in SCID mice

PURPOSE

To evaluate a novel strategy of immunolocalization of human neuroblastoma by targeting the neural cell adhesion molecule (NCAM), which is over-expressed on neuroblastoma.

METHODS

NCAM expression on the cell surface of established neuroblastoma cells was shown by flow cytometry. A SCID mouse model using IMR5-75 neuroblastoma cells to induce subcutaneous tumour growth was established. 131I was used to label monoclonal NCAM specific ERIC1 antibodies generating the 131I-ERIC1 antibody, which showed a high affinity to NCAM also after labelling (KD=9 x 10(-8) mol . l(-1)).

RESULTS

Measurement of organ-specific radioactivity showed low organ-specific uptake (5.33%ID/g (percent of injected dose per gram of tissue) after 72 h), which continuously decreased over the 96 h investigation period, demonstrating clearance of radioactivity. In contrast, tumours accumulated radioactivity continuously up to a peak of 42.07%ID/g at the 96 h time point (31.07%ID/g at 72 h). This specific uptake could be blocked by application of unlabelled ERIC1 antibodies. Measurement of blood specific radioactivity revealed a characteristic clearance over the first 72 h. With 37 Gy, tumour-specific radioactivity reached therapeutic doses after 96 h.

CONCLUSIONS

These results indicate that 131I-labelled ERIC1 has the ability to probe NCAM-expressing tumour cells in vivo with high efficiency and is a promising reagent for the diagnosis and treatment of NCAM-positive human tumours, especially for neuroblastoma.

The role of extracellular spacer regions in the optimal design of chimeric immune receptors: evaluation of four different scFvs and antigens

Human peripheral blood lymphocytes can be transduced to express antigen-dependent CD3zeta chimeric immune receptors (CIRs), which function independently of the T-cell receptor (TCR). Although the exact function of these domains is unclear, previous studies imply that an extracellular spacer region is required for optimal CIR activity. In this study, four scFvs (in the context of CIRs with or without extracellular spacer regions) were used to target the human tumor-associated antigens carcinoembryonic antigen (CEA), neural cell adhesion molecule (NCAM), the oncofetal antigen 5T4, and the B-cell antigen CD19. In all cases human T-cell populations expressing the CIRs were functionally active against their respective targets, but the anti-5T4 and anti-NCAM CIRs showed enhanced specific cytokine release and cytotoxicity only when possessing an extracellular spacer region. In contrast, the anti-CEA and anti-CD19 CIRs displayed optimal cytokine release activity only in the absence of an extracellular spacer. Interestingly, mapping of the scFv epitopes has revealed that the anti-CEA scFv binds close to the amino-terminal of CEA, which is easily accessible to the CIR. In contrast, CIRs enhanced by a spacer domain appear to bind to epitopes residing closer to the cell membrane, suggesting that a more flexible extracellular domain may be required to permit the efficient binding of such epitopes. These results show that a spacer is not necessary for optimal activity of CIRs but that the optimal design varies.

The bi-specific CD3 x NCAM antibody: a model to preactivate T cells prior to tumour cell lysis

To target the neural cell adhesion molecule (NCAM, CD56) on neuroblastoma by T cell-based immunotherapy we have generated a bi-specific CD3 x NCAM antibody (OE-1). This antibody can be used to redirect T cells to NCAM+ cells. Expectedly, the antibody binds specifically to NCAM+ neuroblastoma cells and CD3+ T cells. OE-1 induces T cell activation, expansion and effector function in peripheral blood mononuclear cell (PBMC)-derived CD4+ and CD8+ T cells. T cell activation was shown to depend on the presence of normal natural killer (NK) cells in the culture. Interestingly, while PBMC- derived T cells were activated by OE-1, NK cells were almost completely depleted, suggesting that T cells activated by OE-1 deleted the NK cells. Activated CD4+ and CD8+ T cells differentiate into a larger CCR7+ central memory and a smaller CCR7- effector memory cell population. Most importantly, preactivated T cells were highly cytotoxic for neuroblastoma cells. In eight of 11 experiments tumour-directed cytotoxicity was enhanced when NK cells were present during preactivation with OE-1. These data strongly support a bi-phasic therapeutic concept of primarily stimulating T cells with the bi-specific antibody in the presence of normal NCAM+ cells to induce T cell activation, migratory capacity and finally tumour cell lysis.

Peripheral primitive neuroectodermal tumor of the jugular foramen: case report

OBJECTIVE AND IMPORTANCE

Peripheral primitive neuroectodermal tumor (pPNET) is a rare type of tumor, most commonly found in the limbs of children and young adults. The authors report an extremely rare case of pPNET located at the jugular foramen whose clinical course demonstrated rapid progression.

CLINICAL PRESENTATION

A 23-year-old man presented with a 2-month history of progressive hoarseness and dysphagia. The neuroradiological appearance of the lesion was a jugular foramen tumor.

INTERVENTION

The patient underwent a partial resection of the tumor through a far lateral suboccipital craniotomy. After surgery, the patient experienced an unexpected deterioration in consciousness. Magnetic resonance images on postoperative Day 18 revealed rapid and large expansion of the residual tumor into the posterior fossa. No adjuvant therapy was administered, and the patient died 6 weeks after diagnosis.

CONCLUSION

The pathological diagnosis of the surgical specimen was pPNET, according to the findings of hematoxylin and eosin and immunohistochemical stainings. To the best of our knowledge, this is the first reported case of pPNET at the jugular foramen.

Effect of polysialic acid on the tumor xenografts implanted into nude mice

Polysialic acid (PSA), which is abundantly expressed in the embryonic brain, plays important roles in neural development and plasticity. PSA is also expressed in tumors of neural crest origin such as neuroblastoma. However, the biologic significance of PSA in these tumors has not been elucidated. In this study, we examined the expression of PSA as well as 2 polysialyltransferases, PST and STX, in various tumor cell lines. PST and STX were simultaneously expressed in all the tumor cells positive for PSA. However, even in the tumor cells negative for PSA, they expressed PSA after transfection of neural cell adhesion molecule (NCAM) cDNA when these cells expressed PST, suggesting that the presence of NCAM was critical for PSA expression. To determine the role of PSA in tumor growth and development, we established tumor sublines expressing or lacking PSA from PC-14 or NCI-H146 cells. Although significant differences of growth rates between the PSA-positive and -negative tumor cells were not detected in vitro, the PSA-positive tumor cells hardly produced detectable tumors when injected into nude mice subcutaneously or intravenously. In addition, the PSA-positive tumor cells adhered less to a basement membrane matrix Matrigel than did the PSA-negative tumor cells. These results altogether suggested that PSA significantly reduced tumor formation in the transplanted xenografts through attenuation of cell-cell or cell-matrix interactions by its large, negatively charged glycans in this particular animal model system.

Polysialyltransferase ST8Sia II (STX) polysialylates all of the major isoforms of NCAM and facilitates neurite outgrowth

The neural cell adhesion molecule (NCAM) has different isoforms due to different sizes in its polypeptide and plays a significant role in neural development. In neural development, the function of NCAM is modified by polysialylation catalyzed by two polysialyltransferases, ST8Sia II and ST8Sia IV. Previously, it was reported by others that ST8Sia II polysialylates only transmembrane isoforms of the NCAM, such as NCAM-140 and NCAM-180, but not NCAM-120 and NCAM-125 anchored by a glycosylphosphotidylinositol. In the present study, we first discovered that ST8Sia II polysialylates all isoforms of the NCAM examined, and we demonstrated that polysialylation of NCAM expressed on 3T3 cells facilitates neurite outgrowth regardless of isoforms of NCAM, where polysialic acid is attached. We then show that neurite outgrowth is significantly facilitated only when polysialylated NCAM is present in cell membranes. Moreover, the soluble NCAM coated on plates did not have an effect on neurite outgrowth exerted by soluble L1 adhesion molecule coated on plates. These results, taken together, indicate that ST8Sia II plays critical roles in modulating the function of all major isoforms of NCAM. The results also support previous studies showing that a signal cascade initiated by NCAM differs from that initiated by L1 molecule.

Generation of a humanised single chain Fv (Scfv) derived from the monoclonal Eric-1 recognising the human neural cell adhesion molecule

BACKGROUND

Murine monoclonal antibody (MoAb) ERIC-1 recognises an epitope on the neural cell adhesion molecule (NCAM) whose expression in paediatric and adult tissues is confined mainly to the brain, peripheral nerve, and adrenal medulla. Anti-NCAM antibodies have been used for the treatment and diagnosis of a number of tumours, including neuroblastoma. However, whole antibody exhibits poor penetration into solid tumour deposits and rapid systemic clearance upon repeated administration due to development of a human antimouse antibody (HAMA) response.

PROCEDURE

To overcome these problems, recombinant DNA techniques have been used to humanise and assemble the ERIC-1 immunoglobulin variable heavy (VH) and light (VL) chains into a single chain Fv (scFv).

RESULTS

Three humanised scFv clones were identified which differ from the predicted humanised sequence by occasional amino acid changes, but these maintain the same specificity as the original ERIC-1 MoAb.

CONCLUSIONS

The humanised scFv may prove to be a useful reagents in the treatment and diagnosis of a variety of neuroectodermal tumours and can clearly form a suitable template for the generation of a fully humanised ERIC-1 MoAb.

Differential and cooperative polysialylation of the neural cell adhesion molecule by two polysialyltransferases, PST and STX

PST and STX are polysialyltransferases that form polysialic acid in the neural cell adhesion molecule (NCAM), and these two polysialyltransferases often exist together in the same tissues. To determine the individual and combined roles of PST and STX in polysialic acid synthesis, in the present study we asked if PST and STX differ in the acceptor requirement and if PST and STX act together in polysialylation of NCAM. We first examined whether PST and STX differ in the requirement of sialic acid and core structures of N-glycans attached to NCAM. Polysialic acid was formed well on Lec4 and Lec13 cells, which are defective in N-acetylglucosaminyltransferase V and GDP-fucose synthesis, respectively, demonstrating that a side chain elongating from GlcNAcbeta1-->6Manalpha1-->6R and alpha-1,6-linked fucose are not required. PST and STX were found to add polysialic acid on NCAM.Fc molecules sialylated by alpha-2,3- or alpha-2,6-linkage in vitro, but not on NCAM.Fc lacking either sialic acid. These results indicate that both PST and STX have relatively broad specificity on N-glycan core structures in NCAM and no remarkable difference exists between PST and STX for the requirement of core structures and sialic acid attached to the N-glycans of NCAM. We then, using various N-glycosylation site mutants of NCAM, discovered that PST strongly prefer the sixth N-glycosylation site, which is the closest to the transmembrane domain, over the fifth site. STX slightly prefer the sixth N-glycosylation site over the fifth N-glycosylation site. The results also demonstrated that polysialic acid synthesized by PST is larger than that synthesized by STX in vitro. Moreover, a mixture of PST and STX more efficiently synthesized polysialic acid on NCAM than PST or STX alone. These results suggest that polysialylation of NCAM is influenced by the difference between PST and STX in their preference for N-glycosylation sites on NCAM. The results also suggest that PST and STX form polysialylated NCAM in a synergistic manner.

Expression of the neural cell adhesion molecule in astrocytic tumors: an inverse correlation with malignancy

BACKGROUND

Cell adhesion molecules are among the key factors in the development of the malignant potential of brain tumors. The aim of this study was to investigate the expression of the neural cell adhesion molecule (NCAM) in human astrocytic tumors and assess any relationship between NCAM expression and the degree of malignancy.

METHODS

The expression of NCAM was examined in 52 astrocytic tumors by Western blot analysis. From them the authors selected 23 adult supratentorial ordinary astrocytic tumors and performed quantitative Western blot analysis for each isoform (NCAM 172-180, NCAM 145, NCAM 125-130) to investigate any correlation between the expression of each NCAM isoform and the histologic and biologic malignancy (histology, proliferating cell indices [PCIs] determined by MIB-1 immunohistochemistry, and manifestation on magnetic resonance images [MRIs]). Immunohistochemistry with antihuman NCAM monoclonal antibody was also performed on the tumors from which cryostat sections were available.

RESULTS

Most of the astrocytomas and anaplastic astrocytomas revealed 3 bands at 180, 145, and 125-130kD, whereas in glioblastomas the bands tended to diminish. The expression of each NCAM isoform in astrocytic tumors decreased in proportion to the progression of the histologic malignancy, and the results were also corroborated by immunohistochemical evaluation. An inverse correlation was also observed between the amount of NCAM expression and MIB-1 PCIs. NCAM expression was hardly detectable in those tumors with highly invasive manifestation on MRIs.

CONCLUSIONS

To the authors' knowledge, this study provides the first direct evidence that NCAM is down-regulated in the development of the malignancy of astrocytic tumors; and it is suggested that reduced NCAM expression might be involved in the development of biologic malignancy.

Antitumor killer lymphocytes in the peripheral blood of a patient with transitional cell carcinoma of the bladder

BACKGROUND

Peripheral blood lymphocytes (PBL) from patients with bladder cancer also contain cells possessing cytotoxic activity against autologous tumor cells. These cells are phenotypically heterogenous and include natural killer (NK) and cytotoxic T cells. This study investigated the role of cytotoxic lymphocytes directed against autologous bladder cancer cells.

METHODS

PBL were obtained at intervals before and after surgery and analyzed for cytotoxic activity against autologous bladder cancer cells in 4-hour 51Cr release assay. PBL stimulated with autologous tumor cells were also transformed with human T-lymphotropic virus type-1, establishing a cell line (KB31) which was analyzed for phenotype and cytotoxic activity against the autologous tumor cells.

RESULTS

PBL preoperative cytotoxic activity was low, but increased after surgery. Cytotoxic activity was found not only against autologous bladder cancer cells, but also against heterologous bladder cancer (KK-47) and myeloid leukemia (K562) cells, with the highest activity against the heterologous cell lines. The cytotoxic activity of KB31 was 40% against autologous tumor cells 6 weeks after initiation of the cell line, but decreased to 5% by 6 months. This activity was lower than that against the other cell lines, and was similar to that of PBL in short-term culture. Fluorescence-activated cell sorter (FACS) analysis demonstrated that in KB31 cells at 6 weeks, CD8+ cells were dominant, but CD56+ cells predominated at 6 months.

CONCLUSION

These results suggest that the presence of cytotoxic activity in the peripheral blood of the patient was due to both cytotoxic T cells and NK cells. The cytotoxic activity was lowest prior to surgery and increased postoperatively.

Expression cloning of a human sulfotransferase that directs the synthesis of the HNK-1 glycan on the neural cell adhesion molecule and glycolipids

The HNK-1 carbohydrate is expressed on various adhesion molecules in the nervous system and is suggested to play a role in cell-cell and cell-substratum interactions. Here we describe the isolation and functional expression of a cDNA encoding a human sulfotransferase that synthesizes the HNK-1 carbohydrate epitope. A mutant Chinese hamster ovary cell line, Lec2, which stably expresses human neural cell adhesion molecule (N-CAM) (Lec2-NCAM), was first established. Lec2-NCAM was co-transfected with a human fetal brain cDNA library, a cDNA encoding the rat glucuronyltransferase that forms a precursor of the HNK-1 carbohydrate, and a vector encoding the polyoma large T antigen. The transfected Lec2-NCAM cells expressing the HNK-1 glycan were enriched by fluorescence-activated cell sorting. Sibling selection of recovered plasmids resulted in a cDNA encoding a sulfotransferase, HNK-1ST, that directs the expression of the HNK-1 carbohydrate epitope on the cell surface. The deduced amino acid sequence indicates that the enzyme is a type II membrane protein. Sequence analysis revealed that there is a short amino acid sequence in the presumed catalytic domain, which is highly homologous to the corresponding sequence in other Golgi-associated sulfotransferases so far cloned. The amount of HNK-1ST transcript is high in fetal brain compared with fetal lung, kidney, and liver. Expression of HNK-1ST resulted in the formation of the HNK-1 epitope on N-CAM and a soluble chimeric form of HNK-1ST was shown to add a sulfate group to a precursor, GlcAbeta1-->3Galbeta1-->4GlcNAcbeta1-->R, forming sulfo-->3GlcAbeta1-->3Galbeta1-->4GlcNAcbeta1-->R. The results combined together indicate that the cloned HNK-1ST directs the synthesis of the HNK-1 carbohydrate epitope on both glycoproteins and glycolipids in the nervous tissues.

Structural mosaicism on the submicron scale in the plasma membrane

The lateral mobility of the neural cell adhesion molecule (NCAM) was examined using single particle tracking (SPT). Various isoforms of human NCAM, differing in their ectodomain, their membrane anchorage mode, or the size of their cytoplasmic domain, were expressed in National Institutes of Health 3T3 cells and C2C12 muscle cells. On a 6.6-s time scale, SPT measurements on both transmembrane and glycosylphosphatidylinositol (GPI) anchored isoforms of NCAM expressed in 3T3 cells could be classified into mobile (Brownian diffusion), slow diffusion, corralled diffusion, and immobile subpopulations. On a 90-s time scale, SPT studies in C2C12 cells revealed that 40-60% of transfected NCAM was mobile, whereas a smaller fraction (approximately 10-30%) experienced much slower diffusion. In addition, a fraction of approximately 30% of both transfected GPI and transmembrane isoforms and endogenous NCAM isoforms in C2C12 cells experienced transient confinement for approximately 8 s within regions of approximately 300-nm diameter. Diffusion within both these and the slow diffusion regions was anomalous, consistent with movements through a dense field of obstacles, whereas diffusion outside these regions was normal. Thus the membrane appears as a mosaic containing regions that permit free diffusion as well as regions in which NCAM is transiently confined to small or more extended domains. These results, including a large, freely diffusing fraction, similar confinement of transmembrane and GPI isoforms, a significant slowly diffusing fraction, and relatively large interdomain distances, are at some variance with the membrane skeleton fence model (Kusumi and Sako, 1996). Possible revisions to the model that incorporate these data are discussed.

Cellular determinants of the lateral mobility of neural cell adhesion molecules

The lateral mobility of the neural cell adhesion molecule (NCAM) was examined using fluorescence recovery after photobleaching (FRAP). Various isoforms of human NCAM, differing in their ectodomain, their membrane anchorage mode or in the size of their cytoplasmic domain, were expressed in NIH 3T3 cells and C2C12 muscle cells. When the various isoforms were compared in 3T3 cells, FRAP studies showed both GPI-anchored and transmembrane isoforms diffused rapidly and only small differences in either the diffusion coefficients (D) or the mobile fractions (mf) were measured, suggesting the importance of the ectodomain in regulating lateral diffusion. However, the mobility of all NCAM isoforms was greatly reduced in regions of cell-cell contact, presumably due to homophilic trans interactions between NCAMs on adjacent cells. NCAM isoforms transfected into C2C12 cells which express NCAM naturally usually displayed a significantly lower D compared to the same isoforms transfected into 3T3 cells. Thus, NCAM lateral mobility is modulated in regions where cells interact and by the structure of the host cell membrane.

Altered secondary myogenesis in transgenic animals expressing the neural cell adhesion molecule under the control of a skeletal muscle alpha-actin promoter

The majority of skeletal muscle fibers are generated through the process of secondary myogenesis. Cell adhesion molecules such as NCAM are thought to be intricately involved in the cell-cell interactions between developing secondary and primary myotubes. During secondary myogenesis, the expression of NCAM in skeletal muscle is under strict spatial and temporal control. To investigate the role of NCAM in the regulation of primary-secondary myotube interactions and muscle fusion in vivo, we have examined muscle development in transgenic mice expressing the 125-kD muscle-specific, glycosylphosphatidylinositol-anchored isoform of human NCAM, under the control of a human skeletal muscle alpha-actin promoter that is active from about embryonic day 15 onward. Analysis of developing muscle from transgenic animals revealed a significantly lower number of myofibers encased by basal lamina at postnatal day 1 compared with nontransgenic littermates, although the total number of developing myofibers was similar. An increase in muscle fiber size and decreased numbers of VCAM-1-positive secondary myoblasts at postnatal day 1 was also found, indicating enhanced secondary myoblast fusion in the transgenic animals. There was also a significant decrease in myofiber number but no increase in overall muscle size in adult transgenic animals; other measurements such as the number of nuclei per fiber and the size of individual muscle fibers were significantly increased, again suggesting increased secondary myoblast fusion. Thus the level of NCAM in the sarcolemma is a key regulator of cell-cell interactions occurring during secondary myogenesis in vivo and fulfills the prediction derived from transfection studies in vitro that the 125-kD NCAM isoform can enhance myoblast fusion.

The selection of antibodies for targeted therapy of small-cell lung cancer (SCLC) using a human tumour spheroid model to compare the uptake of cluster 1 and cluster w4 antibodies

Spheroids of a small-cell lung cancer (SCLC) cell line POC were used to evaluate the uptake and penetration of two antibodies recognising different SCLC antigens. Spheroids approximately 300-400 microns in diameter were incubated with 1 microgram ml-1 125I-labelled NY.3D11, an antibody which reacts with the cluster 1 group antigen (neural cell adhesion molecule; NCAM) and [125I]SWA11, which binds to the cluster w4 antigen. The rate of uptake of both antibodies was similar; an initially rapid phase was seen during the first 8 h and maximum uptake occurred by 24 h. The mean uptake per spheroid at 24 h was 0.97 ng for [125I]NY.3D11 and 0.45 ng for [125I]SWA11. An objective measurement of antibody penetration into spheroids was developed using a computerised image analysis of immunostained sections of spheroids. The concentration of antibody and incubation times were varied. Both antibodies penetrated the spheroids to a depth of 50 microns after 30 min. This increased to about 100 microns after 4 h incubation with 1 or 100 micrograms ml-1 SWA11. The results with 1 microgram ml-1 NY.3D11 were similar, but in the presence of 100 micrograms ml-1 NY.3D11 penetration into the spheroid was deep and diffuse. These results demonstrate a major concentration-dependent difference in the uptake and penetration of cluster 1 and cluster w4 antibodies in this spheroid model and they have implications for the selection of antibodies for targeted therapy of SCLC.

Monoclonal antibodies specific for endoplasmic membranes of mammalian cochlear outer hair cells

Monoclonal antibodies were raised in vitro against an antigen associated with the lateral cisternal membranes of outer hair cells. Two of the antibodies were class IgM and one of these retained its specific reactivity in tissue fixed with aldehydes and embedded in the resin LR White. Immunogold labelling for electron microscopy showed that the antigen was closely associated with the membranes rather than the cytoplasmic or lumenal regions of the cisternae. The third antibody was an IgG. All three weakly labelled a protein band with an apparent molecular weight of about 60 kD on a Western blot. The antibodies did not cross-react with any other cell in the organ of Corti, including the inner hair cells. Furthermore, they showed no cross-reactivity with skeletal muscle, kidney, gut, brain, skin, blood or retina from the guinea pig. The results suggest that the lateral cisternae in outer hair cells may be functionally different from those of inner hair cells. The antibodies may provide useful markers for outer hair cells in studies of hair cell regeneration.

Expression of adhesion molecules by endovascular trophoblast and decidual endothelial cells: implications for vascular invasion during implantation

During the process of implantation, maternal spiral arteries within the decidua are invaded by trophoblast cells that adhere to and migrate along the luminal surface of the vascular endothelial cells. This phenomenon resembles the events that occur during the migration of neutrophils into an acute inflammatory site, therefore it is possible that similar mechanisms are involved. Indeed, previous observations have shown that endovascular trophoblast expresses the blood group-related antigen sialyl Le(x). In this study, we show, by immunohistology, the expression of both E- and P-selectin by vascular endothelial cells only in the decidua basalis and not in decidua parietalis. In contrast, ICAM-1 is expressed by all vascular endothelium throughout the decidua. Expression of VCAM-1 is variable at the implantation site, and is not expressed by vascular endothelial cells in decidua parietalis. Interestingly, we demonstrate the strong expression of a polysialylated form of NCAM by endovascular trophoblast. Our data suggests that vascular invasion by trophoblast is regulated by the expression of appropriate adhesion molecules which permit interaction between endovascular trophoblast and decidual endothelial cells.

Differential effects of over-expressed neural cell adhesion molecule isoforms on myoblast fusion

We have used a transfection based approach to analyze the role of neural cell adhesion molecule (NCAM) in myogenesis at the stage of myoblast fusion to form multinucleate myotubes. Stable cell lines of myogenic C2 cells were isolated that express the transmembrane 140- or 180-kD NCAM isoforms or the glycosylphosphatidylinositol (GPI) linked isoforms of 120 or 125 kD. We found that expression of the 140-kD transmembrane isoform led to a potent enhancement of myoblast fusion. The 125-kD GPI-linked NCAM also enhanced the rate of fusion but less so when a direct comparison of cell surface levels of the 140-kD transmembrane form was carried out. While the 180-kD transmembrane NCAM isoform was effective in promoting C2 cell fusion similar to the 140-kD isoform, the 120-kD isoform did not have an effect on fusion parameters. It is possible that these alterations in cell fusion are associated with cis NCAM interactions in the plane of the membrane. While all of the transfected human NCAMs (the transmembrane 140- and 180-kD isoforms and the 125- and 120-kD GPI isoforms) could be clustered in the plane of the plasma membrane by species-specific antibodies there was a concomitant clustering of the endogenous mouse NCAM protein in all cases except with the 120-kD human isoform. These studies show that different isoforms of NCAM can undergo specific interactions in the plasma membrane which are likely to be important in fusion. While the transmembrane and the 125-kD GPI-anchored NCAMs are capable of enhancing fusion the 120-kD GPI NCAM is not. Thus it is likely that interactions associated with NCAM intracellular domains and also the muscle specific domain (MSD) region in the extracellular domain of the GPI-linked 125-kD NCAM are important. In particular this is the first role ascribed to the O-linked carbohydrate containing MSD region which is specifically expressed in skeletal muscle.

Applications of monoclonal antibodies in the investigation, diagnosis, and treatment of retinoblastoma

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Vase mini-exon usage by NCAM is not restricted to tumours of neuroectodermal origin

The neural cell adhesion molecule (NCAM) plays an important role in normal development. Many variants of NCAM are generated through post-transcriptional and post-translational modifications. These variants are tissue-specific and their expression is developmentally regulated. NCAM is also re-expressed in a number of human tumours, including neuroblastoma, rhabdomyosarcoma, Wilms' tumour and Ewing's sarcoma. We have characterized the NCAM variants associated with rhabdomyosarcoma. Polysialylated NCAMs are present in this tumour and, after neuraminidase treatment, they resolve into 2 bands of 140 and 120 kDa. These data were corroborated by Northern-blot analysis where mRNA species of 6.7 and 5.5 kb are detected. These mRNA code for the 140- and 120-kDa NCAM proteins respectively. PCR analysis shows that the previously described VASE mini-exon is also present in NCAM found in rhabdomyosarcoma. The VASE mini-exon, spliced at exon 7-8 junctions, has previously been detected in neural and heart NCAM, as well as in NCAMs found in human small-cell lung carcinoma (SCLC). DNA sequencing confirmed that the VASE mini-exon in rhabdomyosarcoma is identical to that found in neuroblastoma and SCLC.

Treatment of recurrent and cystic malignant gliomas by a single intracavity injection of 131I monoclonal antibody: feasibility, pharmacokinetics and dosimetry

A pilot study was undertaken to determine the feasibility of infusing 131I labelled monoclonal antibodies (MoAbs) into either the cavity remaining after resection of malignant glioma or into glioma cysts. Of the seven patients recruited into the study, two had cystic lesions and five resection cavities. Six of the seven were treated after relapse from primary therapy. All patients apart from one, were given a single injection of 131I conjugated to a MoAb (ERIC-1) recognising the human neural cell adhesion molecule (NCAM). One patient received a further injection of 131I-MoAb after regrowth of their disease. Pharmacokinetic studies revealed that the MoAb remained predominantly in the tumour cavity with little leakage into the systemic compartment. This resulted in a high calculated dose of radiation being delivered to the tumour cells either lining or within close proximity to the cavity/cyst wall. In such a small study, it is not possible to determine accurately response rates, but individual patient responses were observed. This, along with the low toxicity noted, demonstrates the feasibility of using 131I-MoAbs in this way. With 131I, radiation dose is deposited in tissue to a depth of 1 mm from the source. The possibility of applying isotopes such as 90Yttrium which will irradiate tumour/tissue to a greater depth (6 mm) is discussed in context with the biology of glioma infiltration into normal brain parenchyma.

Progress review: intrathecal and intratumoral injection of radiolabelled monoclonal antibodies (MoAbs) for the treatment of central nervous system (CNS) malignancies

The systemic administration of monoclonal antibodies (MoAbs) as delivery vehicles for targeted radiation therapy is associated with many problems. Most studies show that insufficient isotope is taken up into the tumour to elicit a tumoricidal effect. This has led several groups to explore the administration of radiolabelled MoAbs into body compartments, specifically for the treatment of minimal tumour deposits that present either as malignant ascites or small nodules on the lining of body cavities. The use of 131Iodine (131I) labelled MoAbs in the treatment of disseminated disease in the central nervous system (CNS) is described and the possibility of administering radiolabelled MoAbs to a cavity generated after debulking surgery for malignant glioma in order to overcome the problem of poor MoAb uptake into solid tumour deposits is discussed together with the rationale for substituting 90Yttrium (90Y) for 131I.

A study of adhesion molecules as markers of progression in malignant melanoma

Adhesion molecules are substances which are involved in the interactions between cells, and between cells and the extracellular matrix in both benign and malignant tissues. Two members of this group--intercellular adhesion molecule-1 (ICAM-1) and MUC18--have previously been found to be expressed on melanoma; however, studies seeking a correlation between expression and metastatic behaviour have yielded conflicting results. In this study we investigated the expression of these two antigens and that of a number of other adhesion molecules [VCAM-1, ELAM, and the neural cell adhesion molecule (NCAM)] on a range of benign and malignant melanocytic lesions. Both ICAM-1 and MUC18 were found on a high percentage of all melanocytic lesions including benign naevi. VCAM-1 was found to be expressed on 79 per cent of benign naevi, 62 per cent of primary melanomas less than 1.5 mm in depth, and 6 per cent of thick primaries. The antigen was present on 14 per cent of lymph node metastases and on no extranodal deposits. This suggests that loss of melanoma cell adhesion mediated by VCAM-1 may be important in the development of metastatic melanoma.

Retinoblastoma: messenger RNA for interphotoreceptor retinoid binding protein

Surgically excised retinoblastomas from 14 patients (age range nine months to two years) were assessed by immunocytochemistry for the expression of photoreceptor-specific proteins and neuronal and glial cell markers. Adjacent tissues were examined for messenger RNA expression of interphotoreceptor retinoid-binding protein (IRBP) using Northern blots. For immunocytochemical stains (ABC method), monoclonal and polyclonal antibodies included S-Ag, rhodopsin, neuron specific enolase (NSE), glial fibrillary acidic protein (GFAP), IRBP, neural adhesion molecule (N-CAM), and rod and cone specific transducin (TR alpha and TC alpha). Histopathology revealed mostly poorly differentiated tumors with necrosis and lack of Flexner-Wintersteiner rosettes. Immunocytochemical staining showed focal IRBP expression in one of the tumors and S-antigen in two cases. Immunoreactivity with rhodopsin was negative. N-CAM, a neural adhesive protein which appears to be involved in the regulation of adhesive interaction during neuronal differentiation, was positive except in two cases. All tumors showed immunoreactivity with NSE, whereas GFAP staining was limited to the perivascular glial tissue confirming the essential neuronal nature of retinoblastoma cells. TC alpha was detected in all tumors and TR alpha in one case. Messenger RNA for IRBP was detected in tumors in which IRBP immunoreactivity could not be detected.

Splicing of the VASE exon of neural cell adhesion molecule (NCAM) in human small-cell lung carcinoma (SCLC)

Expression of the neural cell adhesion molecule (NCAM) on small-cell lung carcinoma (SCLC) cell lines and tumour tissue has been investigated. Cell lines were found to express highly sialylated NCAM. Neuraminidase treatment revealed the presence of the 140- and 120-kDa isoforms with differential expression of a 95-kDa protein. Similar data were obtained with SCLC tumour tissues. These results were corroborated by Northern blotting where mRNA of 6.7 and 5.5 kb coding for the 140- and 120-kDa isoforms, respectively, were identified. In a few tumours, a weaker band of 7.4-kb mRNA coding for the 180-kDa NCAM was also identified. This result could not be confirmed biochemically due to shortage of material. Finally, a 5-kb transcript was identified in all SCLC samples examined. The NCAM isoform coded by this mRNA remains unknown. Using the polymerase chain reaction (PCR), we have demonstrated the presence of the VASE mini-exon in some isoforms of SCLC NCAM. The VASE mini-exon sequence in human SCLC differs from the published murine sequence by only one base change. This substitution does not result in altered amino-acid sequence.