Bispecific antibodies as targeting agents for boron neutron capture therapy of brain tumors

Boron neutron capture therapy (BNCT) is based on the nuclear reaction that occurs when boron-10, a stable isotope, is irradiated with low energy (< or = 0.025 eV) or thermal neutrons to yield alpha particles and recoiling lithium-7 nuclei. A major requirement for the success of BNCT is the selective delivery of a sufficient number of boron atoms (approximately 10(9)) to individual cancer cells to sustain a lethal 10B (n, alpha) 7Li capture reaction. A panel of BsAb reactive with polyhedral borane anions (PBA) and a tumor-associated chondroitin sulfate proteoglycan has been produced. All of these BsAb showed strong reactivity with a panel of human glioblastoma and melanoma cell lines, as demonstrated by indirect membrane immunofluorescence. Two of them (H6 and B8) also reacted with cells that had been exposed to PBA (Na2B10H10 and Na2B12H11SH) and a boronated starburst dendrimer, which contained approximately 250-400 B atoms per molecule. The affinity constant (Ka) of BsAb-B8 was 2.57 x 10(8) M-1 on M21 human melanoma cell and 3.49 x 10(8) M-1 on A172 glioblastoma cells, which were almost identical to those of the parental monoclonal antibody (mAb) 9.2.27 on the same cell lines (2.62 x 10(8) M-1). Since our BsAb recognize both human glioblastoma and melanoma-associated antigens, as well as PBA, they potentially could be used to target 10B to these tumors for BNCT.

Development of a cleavage-site-specific monoclonal antibody for detecting metalloproteinase-derived aggrecan fragments: detection of fragments in human synovial fluids

We have developed a monoclonal antibody AF-28 that specifically recognizes a neo-epitope on polypeptides with N-terminal FFGVG ... sequences. This sequence is found at the N-terminus of aggrecan fragments that have been digested with matrix metalloproteinases (MMPs). By immunoblotting, monoclonal antibody AF-28 specifically detected G2 fragments derived from an aggrecan G1-G2 substrate digested with stromelysin, collagenase, gelatinase and matrilysin, but failed to detect G2 fragments obtained from elastase, trypsin or cathepsin B digests. Undigested G1-G2 was not detected. In addition, AF-28 antibody detected fragments derived from whole aggrecan and this detection did not require prior treatment with chondroitinase or keratanase. Competition experiments confirmed that peptides containing internal ... FFGVG ... sequences were not detected by the antibody, while native MMP-digested aggrecan fragments and a synthetic 32-mer peptide with FFGVG ... N-termini were equally competitive on a molar basis. An FFGVG 5-mer, and an FGVGGEEDI9-mer which lacked the N-terminal phenylalanine residue, were 50 times and 230 times respectively less competitive than the FFGVG ... 32-mer. Two fragments from the interglobular domain, F342-F373 and F342-D441, that are predicted products of G1-G2 digestion by neutrophil collagenase but have not previously been detected, could be detected with AF-28. The epitope recognized by AF-28 was also detected in human synovial fluids by Western blot analysis. A broad band of 100-200 kDa was detected in some patients and a dominant band of 40-60 kDa was found in two patients. The size of this small fragment corresponds with that seen for the porcine F342-E373 product and may represent the natural physiological product of aggrecan cleaved in vivo at both the MMP site (... DIPEN341 decreases F342FGVG ...) and the aggrecanase site (... ITEGE373 decreases A374RGSVI ...).

Chondroitin-4-sulphate (proteoglycan), a receptor for Plasmodium falciparum-infected erythrocyte adherence on brain microvascular endothelial cells

Adherence of Plasmodium falciparum parasitized erythrocytes to the microvascular endothelium is mediated by different receptors expressed by endothelial cells. The study of the adherence of P. falciparum-infected erythrocytes to Saimiri monkey brain microvascular endothelial cells revealed the presence of an additional receptor, which was identified and further characterized. This receptor was also found on the surface of primary human lung endothelial cells (HLEC). We developed two mAbs to this receptor which very efficiently blocked the adherence of parasite strains to Saimiri brain endothelial cells (SBEC). The ability of these mAb to bind to SBEC was partially blocked by chondroitin-4-sulphate (CSA). Competitive inhibition assays on adherence of parasitized red blood cells (PRBC) showed that CSA, but not hyaluronic acid, chondroitin-6-sulphate, dermatan sulphate, keratane sulphate, heparan sulphate or chondroitin-4S-disaccharide, was able to almost completely inhibit PRBC adherence. The same effect was obtained with chondroitinase ABC and AC, but not B, hyaluronidase or heparinase. These results strongly suggest that a member of the chondroitin-glycosaminoglycan family, CSA, represents an additional receptor used by P. falciparum PRBC to cytoadhere to microvascular endothelial cells.

Antibodies to three chondroitin sulfate-containing proteoglycans in squid skin recognize hexa- or longer chondroitin oligosaccharides as major antigenic determinants

The reactivities of antibodies to three squid skin proteoglycans with (a) chondroitin-derived oligosaccharides and chondroitin sulfate-derived disaccharides, (b) the proteoglycans and their constituents, and (c) chondroitin, chondroitin sulfate, and hyaluronic acid were studied with enzyme-linked immunosorbant assay inhibition tests. Immunization of rabbits with two chondroitin proteoglycans (ChPG I and ChPG II) and an oversulfated chondroitin sulfate proteoglycan (CSSPG) gave rise to highly reactive antisera which were mainly reactive with the glycosaminoglycans, the oligosaccharides, and the core proteins obtained after digestion of proteoglycans with chondroitinase AC. Inhibition of binding of antibodies to ChPG I, ChPG II, and CSSPG with chondroitin-derived oligosaccharides revealed that the minimal antigenically active structure was the hexasaccharide of chondroitin and that the respective octasaccharide was more active. Sulfated delta-disaccharides were not reactive with antibodies to ChPG I and II, whereas some reactivities (30% maximum inhibition) were obtained with antibodies to CSSPG. Chondroitin chains (80 kDa) of ChPG I and II were responsible for most of the reactivity with proteoglycans (78-95% maximum inhibition). Chemically desulfated chondroitin sulfate (12 kDa) showed considerable cross-reactivity with all antisera tested (62-68% maximum inhibition), whereas the nonsulfated molecule of hyaluronic acid and a hyaluronic acid fraction of 16 kDa were not reactive. The reactivities of antibodies with the proteoglycans' oligosaccharides and core proteins obtained by chondroitinase AC digestion were mainly due to the presence of nonsulfated chondroitin sulfate structures. This study clearly shows that the major antigenic determinants recognized by antibodies to squid skin proteoglycans, each containing chondroitin sulfates with different sulfation patterns, involve hexa- or larger chondroitin oligosaccharides.

Phase I studies of treatment of malignant gliomas and neoplastic meningitis with 131I-radiolabeled monoclonal antibodies anti-tenascin 81C6 and anti-chondroitin proteoglycan sulfate Me1-14 F (ab')2--a preliminary report

The advent of monoclonal antibody (MAb) technology has made Ehrlich's postulate of the 'magic bullet' an attainable goal. Although specific localization of polyvalent antibodies to human gliomas was demonstrated in the 1960s, the lack of specific, high affinity antibody populations and of defined target antigens of sufficient density precluded therapeutic applications. Not until the identification of operationally specific tumor-associated antigens (present in tumor tissue but not normal central nervous system tissue); production of homogeneous, high affinity MAbs to such antigens; and the use of compartmental administration (intrathecal or intracystic), has the promise of passive immunotherapy of primary and metastatic central nervous system neoplasms been recognized. We report here preliminary data from Phase I studies of the compartmental administration of the anti-tenascin MAb 81C6 and F(ab2)2 fragments of MAb Me1-14, which recognizes the proteoglycan chondroitin sulfate-associated protein of gliomas and melanomas, to patients with primary central nervous system tumors or tumors metastatic to the central nervous system. Phase I dose escalation studies of intracystically administered 131I-labeled anti-tenascin MAb 81C6 to either spontaneous cysts of recurrent gliomas or surgically created cystic resection cavities have resulted in striking responses. Of five patients with recurrent cystic gliomas treated, four had partial responses, clinically or radiographically. Similarly, in patients with surgically created resection cavities, a partial response at the treatment site and extended stable disease status has been obtained following intracystic administration of 131I-labeled 81C6. No evidence of hematologic or neurologic toxicity has been observed in either patient population, with the exception of transient exacerbation of a pre-existing seizure disorder in a single patient. Dosimetry calculations indicated high intracystic retention for four to six weeks with little or no systemic dissemination; estimated total doses intracystically ranged from 12,700-70,290 rad. Intrathecal administration of labeled MAbs to patients with neoplastic meningitis is more difficult to assess in terms of clinical responsiveness. Of patients so treated with either 131I-labeled 81C6 or 131I-labeled Me1-14 (F(ab)2, cerebrospinal fluid and radiographic responses have been achieved, and survival prolongation through maintenance of stable disease has been observed in several cases. Initial results from pHase I dose escalation trials are encouraging in terms of the proportion of cases of disease stabilization and partial and complete responses obtained. Importantly, neurotoxicity has been virtually nonexistent, and hematologic toxicity rare and rapidly responsive to treatment.(ABSTRACT TRUNCATED AT 400 WORDS)

Multiple receptor-like protein tyrosine phosphatases in the form of chondroitin sulfate proteoglycan

The possibility that some of the brain proteoglycans are receptor-like protein tyrosine phosphatases (PTPases) was investigated. Membrane-bound proteoglycan fractions were prepared from the postnuclear membrane fraction of 8-day-old rat brain by DEAE ion-exchange chromatography and CsCl density gradient centrifugation. The isolated proteoglycan fractions showed high PTPase specific activities together with the typical PTPase characteristics. Renaturation experiments indicated that chondroitin sulfate proteoglycans with 380- and 170-kDa core proteins carried the PTPase activity. The proteoglycan with 380-kDa core protein was identified as RPTP beta/zeta bearing HNK-1 carbohydrate.

Glomerular mesangial cells in vitro synthesize an aggregating proteoglycan immunologically related to versican

Recent studies have shown that mesangial cells derived from human adult glomeruli synthesize a number of 35S-labelled proteoglycans including a large chondroitin sulphate proteoglycan (CSPG), two dermatan sulphate proteoglycans (biglycan and decorin) and two heparan sulphate proteoglycans [Thomas, Mason and Davies (1991) Biochem. J. 277, 81-88]. In the present study we have examined the interaction of these proteoglycans with hyaluronan (HA) using associative gel chromatography. Only the large CSPG bound to HA, with 60% of those molecules in the medium and 80% of those in the cell layer being able to interact. Reduction and alkylation, or treatment of the monomer CSPG with proteinases, prevented the formation of aggregates, suggesting that the core protein was involved. The aggregates formed between purified CSPG and HA could be dissociated in the presence of HA-oligosaccharides of at least 10 monosaccharides in length. The inclusion of link protein with CSPG and HA promoted the formation of aggregates. Experiments with 3H-labelled mesangial-cell proteoglycans confirmed that only the large CSPG, with core protein molecular masses of 400 kDa and 500 kDa, interacted with HA. After chondroitin ABC lyase treatment of CSPG isolated from conditioned culture medium, several bands similar to those observed with 3H-labelled core proteins were identified using a polyclonal antiserum that recognizes versican. A monoclonal antibody recognizing the 1-C-6 epitope in the G1 and G2 globular regions of aggrecan did not recognize either mesangial-cell CSPG or bovine aortic versican. Northern-blot analysis confirmed that human mesangial cells express versican. Thus human mesangial large CSPG is a member of the versican family of proteoglycans. The interaction of CSPG and HA within the glomerulus may be important in glomerular cell migration and proliferation.

Developmentally regulated expression of a brain specific species of chondroitin sulfate proteoglycan, neurocan, identified with a monoclonal antibody IG2 in the rat cerebrum

The mammalian brain contains many species of proteoglycan. To identify each proteoglycan species, we have raised monoclonal antibodies against soluble chondroitin sulfate proteoglycans purified from 10-day-old rat brains. One monoclonal antibody, named monoclonal antibody 1G2, recognized two proteoglycan species with 220,000 and 150,000 mol. wt core glycoproteins (chondroitin sulfate proteoglycan-220 and chondroitin sulfate proteoglycan-150). Partial amino acid sequences of N-termini of their core proteins coincided with those of neurocan, a brain-unique chondroitin sulfate proteoglycan species, whose complete coding sequence was recently reported [Rauch et al. (1992) J. biol. Chem. 269, 19,536-19,547]. Western blots revealed that chondroitin sulfate proteoglycan-220 became detectable in the rat cerebrum on embryonic day 14, and that it disappeared from the brain around postnatal day 30. In contrast, a fairly large amount of chondroitin sulfate proteoglycan-150 remained in the mature brain. Immunohistochemical studies revealed that 1G2 antigen was first localized in the preplate zone, then both in the marginal zone and in the subplate of the rat cerebrum on embryonic day 16, prior to arrival of the first thalamic afferents at the cortex. On embryonic day 20, immunolabeling with monoclonal antibody 1G2 began to spread from the subplate into the developing cortical plate. On postnatal day 10, the neuropil of the cerebrum, except for the barrel field, was diffusely stained with the antibody, intensely in the hippocampus and superficial layers (I-III) of the cerebral cortex and weakly elsewhere. The barrel hollows were stained very weakly compared with the barrel walls at this stage. The immunoreactivity in the hippocampus and superficial cortical layers was weakened in the mature brain, so that no particular staining pattern, but weak and diffuse staining was observed in the adult rat cerebrum. The 1G2 antigen was immunohistochemically associated largely with glial fibrillary acidic protein-positive cells in primary cultures of the neonatal rat cerebrum. Both chondroitin sulfate proteoglycan-220 and chondroitin sulfate proteoglycan-150 were detected in the conditioned media not only of highly enriched cultures of fetal rat cortical neurons but also of pure cultures of mature astrocytes; more (12- to 20-fold) in the astrocyte conditioned media. Astrocytes, in addition to neurons, may be a cellular source of neurocan in brain at least under certain physiological conditions. The spaciotemporal expression pattern of 1G2 epitope-bearing proteoglycan, or neurocan, suggests that this proteoglycan species plays some roles at least in forming the elongation pathway for early cortical afferent fibers as well as the functional barrel structure in the somatosensory cortex.

Development of enzyme immunoassays specific for keratan sulphate- and core-protein-epitopes of the large aggregating proteoglycan from human articular cartilage

In the course of chronic inflammatory and degenerative joint diseases proteoglycans are degraded by the action of proteases and oxygen radicals. Therefore, proteoglycan fragments, released from cartilage into the peripheral blood, might be useful markers of cartilage degradation. Sensitive enzyme immunoassays are useful for the detection of these proteoglycan fragments in serum. We therefore developed specific monoclonal antibodies against the large aggregating proteoglycan (aggrecan), which has been isolated and purified from human articular cartilage. Two monoclonal antibodies which recognize a novel cartilage-specific epitope on the keratan sulphate chain of aggrecan (mAb 4B3/D10) and an epitope of the core-protein of aggrecan (4G4/A10) were selected for the development of competitive enzyme-immunoassays. These assays allow the sensitive and specific detection of cartilage-derived proteoglycan fragments, not only in synovial fluid but also in serum. They can now be used for the study of inflammatory and degenerative joint diseases.

Retinal ganglion cell survival in vitro maintained by a chondroitin sulfate proteoglycan from the superior colliculus carrying the HNK-1 epitope

We recently reported evidence implicating a superior colliculus-derived chondroitin sulfate proteoglycan (SCCP) in the trophic support of cultured retinal ganglion cells (Schulz et al., 1990). In the present work we show preparations of the SCCP to be reactive with an antibody (CS-56) to chondroitin sulfate types A and C and with the HNK-1 antibody. Reaction with the HNK-1 antibody allowed us partially to purify the native proteoglycan by immunoaffinity chromatography. HNK-1 reactive material was further processed by a combination of molecular sieve chromatography in the presence of 4M guanidine HCL followed by anion exchange chromatography to yield a product that migrated electrophoretically as a single band in polyacrylamide gel with an apparent molecular weight of not less than 400 k. The SCCP, when added to a fully defined culture medium, maintained the survival of the vast majority (80%) of the ganglion cells over a 16 hr culture period with 86% of these cells showing a profusion of processes; few ganglion cells (10%) survived in the absence of the proteoglycan. Electrophoretic analysis of nonreduced preparations of the molecule did not reveal any low molecular weight silver stained components that may have remained associated with the molecule after guanidine HCL treatment. However, two bands corresponding to molecular weights of around 60 and 80 k were reproducibly observed on polyacrylamide gels following electrophoresis of the molecule in the presence of beta-mercaptoethanol. Our findings provide further evidence suggesting a role for a chondroitin sulfate proteoglycan carrying the HNK-1 epitope in the trophic support of central neurones.

Basement membrane-specific chondroitin sulfate proteoglycan is abnormally associated with the glomerular capillary basement membrane of diabetic rats

We have previously reported the production of monoclonal antibodies (MAb) recognizing the core protein of a basement membrane-specific chondroitin sulfate proteoglycan (BM-CSPG). Using immunohistochemical techniques, we have shown that BM-CSPG is present in almost every basement membrane, one exception being the normal glomerular capillary basement membrane (GBM), where it is absent. In the present study of mature kidneys we examined the distribution of BM-CSPG in streptozocin-induced diabetes mellitus in rats. We found BM-CSPG atypically associated with the GBM of diabetic animals as early as 1 month after induction of diabetes mellitus. Immunoelectron microscopy (IEM) of affected capillary loops showed BM-CSPG present in the subendothelial matrix in areas of GBM thickening and absent in areas where the GBM appears to be of normal thickness. Moreover, the association of BM-CSPG with regions of the pericapillary GBM affects the morphology of the capillary endothelial cells within these areas, directly displacing the cell body from the GBM proper and causing loss of fenestrae. These new data on BM-CSPG distribution reflect abnormal glomerular extracellular matrix protein biosynthesis/turnover in diabetes and suggest that BM-CSPG in the GBM might in turn affect normal capillary structure and/or function.

The sulphation pattern in chondroitin sulphate chains investigated by chondroitinase ABC and ACII digestion and reactivity with monoclonal antibodies

We have used progressive chondroitinase digestion of pig aggrecan in conjunction with ELISA assays and disaccharide analysis to derive information about the pattern of 4- and 6-sulphation in chondroitin sulphate chains. Digestion with chondroitinase ABC resulted in the release of mainly disaccharides from the nonreducing terminal of chondroitin sulphate chains but there was also the release of some tetra- and hexa-saccharides which were degraded to disaccharides with more extensive digestion. Chondroitinase ACII, in contrast, released only disaccharides. Analysis of the disaccharide composition of the intact and digested products at different stages of digestion showed that there was a slight increase in 6-sulphate content of the chains as they were shortened. Reaction of the partially digested proteoglycans with monoclonal antibodies 3-B-3 and 3-D-5 which recognise chains terminating in 6- or 4-sulphated disaccharides, respectively, showed major differences between chondroitinase ABC and ACII products. The results suggested that chondroitinase ABC preferentially cleaved next to 4-sulphated, rather than 6-sulphated disaccharides and this resulted in some oligosaccharides as well as disaccharide being released. Chondroitinase ACII also cleaved an additional disaccharide next to the linkage to protein of chondroitin sulphate, which was not removed by chondroitinase ABC and this disaccharide was mainly nonsulphated.

Intermittent loading induces the expression of 3-B-3(-) epitope in cultured bovine articular cartilage

OBJECTIVE

To study the effects of intermittent loading on the proteoglycans synthesized in intact cultured articular cartilage.

METHODS

Sesamoid bones carrying articular cartilage were subjected to cyclic loading in vitro for one week. A new procedure to fix and decalcify the tissue was developed and an immunohistochemical analysis of the expression of 3-B-3(-) epitope in the articular cartilage was carried out. The proteoglycans synthesized were quantified and studied using CL-2B chromatography.

RESULTS

Loading induced an increase in the synthesis of aggrecan molecules, which were larger and less polydisperse than those from control cartilage. Loading also induced the expression of 3-B-3(-) epitopes on newly synthesized proteoglycans.

CONCLUSION

These changes are similar to those found in early experimental and human osteoarthritis (OA). More variables must be studied, but our results suggest that our model might be suitable to study early events in the onset of OA.

Claustrin, an antiadhesive neural keratan sulfate proteoglycan, is structurally related to MAP1B

Our laboratory has recently identified a keratan sulfate proteoglycan (KSPG), named claustrin, that inhibits neural cell adhesion and neurite outgrowth in the chick nervous system. Antisera prepared against claustrin were used to screen a cDNA expression library from embryonic day 9 chick brain. Initial characterization of positive cDNAs revealed a high degree of homology to the mouse MAP1B gene, although these cDNAs represent a 5' truncated fragment of MAP1B. Protein sequencing of three peptides derived from a tryptic digest of purified, keratanase-treated claustrin also revealed strong homology to MAP1B, and confirmed the authenticity of the 3.4 kb claustrin cDNA. To further determine the relationship between these two proteins, we used antibodies against MAP1B and KSPGs in immunoblotting and immunohistochemical studies. These studies demonstrated cross-reactivity between MAP1B and claustrin antibodies, and that monoclonal antibodies to cartilage keratan sulfate react with MAP1B in rat nervous tissue, and with claustrin in the chick nervous system. In addition, keratanase treatment of a taxol microtubule fraction from chick or rat brain eliminated MAP1B, as detected by immunoblotting with the MAP5 monoclonal antibody. These results suggest that MAP1B and claustrin are highly related, if not identical, proteins.

A central nervous system keratan sulfate proteoglycan: localization to boundaries in the neonatal rat brain

During the development of the central nervous system (CNS), adhesive molecules promote the formation of axonal pathways and appropriate neuronal connections by facilitating cellular interactions. In addition to the interactions that bring neurons together, recent evidence suggests inhibition of neuronal interactions also plays a role by restricting axons to their appropriate pathways and forming boundaries between functional units of the developing CNS. The present study describes the distribution of a recently identified large keratan sulfate proteoglycan, ABAKAN, in the postnatal day 14 (P14) and adult rat brain. In the adult brain ABAKAN appears to be relatively evenly distributed throughout the CNS, while at P14 this proteoglycan is found at high concentrations between different functional units of the neonatal brain. For example, ABAKAN appears to separate different cortical areas and mark the boundaries between thalamic nuclei. In vitro assays demonstrate that this keratan sulfate proteoglycan is a potent inhibitor of neurite growth. The distribution of ABAKAN at P14 and the effects of this keratan sulfate proteoglycan on neurite growth suggest that ABAKAN functions as a molecular barrier to axonal growth in the developing rat brain.

The SV2 protein of synaptic vesicles is a keratan sulfate proteoglycan

We have determined that synaptic vesicles contain a vesicle-specific keratan sulfate integral membrane proteoglycan. This is a major proteoglycan in electric organ synaptic vesicles. It exists in two forms on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, i.e., the L form, which migrates like a protein with an M(r) of 100,000, and the H form, with a lower mobility that migrates with an M(r) of approximately 250,000. Both forms contain SV2, an epitope located on the cytoplasmic side of the vesicle membrane. In addition to electric organ, we have analyzed the SV2 proteoglycan in vesicle fractions from two other sources, electric fish brain and rat brain. Both the H and L forms of SV2 are present in these vesicles and all are keratan sulfate proteoglycans. Unlike previously studied synaptic vesicle proteins, this proteoglycan contains a marker specific for a single group of neurons. This marker is an antigenically unique keratan sulfate side chain that is specific for the cells innervating the electric organ; it is not found on the synaptic vesicle keratan sulfate proteoglycan in other neurons of the electric fish brain.

Expression of the chondroitin sulphate proteoglycan molecular complex in six human melanoma xenograft lines studied by flow cytometry and immunohistochemistry

The expression of the chondroitin sulphate proteoglycan (CSP) molecular complex in six human melanoma xenograft lines (BEX-t, COX-t, HUX-t, ROX-t, SAX-t, WIX-t) was studied by flow cytometry and immunohistochemistry using the monoclonal antibodies 9.2.27, ME31.3, G7A5, and NKI.M6. The two methods and the four antibodies gave consistent results. The six melanoma lines could be divided into three distinct groups of two lines each; expression was high in the HUX-t and ROX-t lines and intermediate in the BEX-t and SAX-t lines, whereas the COX-t and WIX-t lines were negative. The mean number of epitopes per cell for 9.2.27 was approximately twice as high as for ME31.3, G7A5, and NKI.M6 and was estimated to range from 0.8 +/- 0.1 x 10(5) to 1.9 +/- 0.2 x 10(5) in the positive xenograft lines. The expression of the CSP complex was heterogeneous. The immunofluorescence histograms measured by flow cytometry were therefore broad for all tumour lines. A significant fraction of the HUX-t cells was negative or weakly stained. These cells appeared as clear negative patches in the immunohistochemical preparations. Moreover, most morphologically intact tumour cells adjacent to necrotic areas did not show significant expression of the CSP complex, irrespective of tumour line. These cells were probably hypoxic and thus resistant to radiation therapy. The expression of the CSP complex in the xenograft lines was similar to that reported for melanoma in man.

Monoclonal antibodies to the large chondroitin sulphate proteoglycan from bovine temporomandibular joint disc

Four hybrid cell lines producing monoclonal antibodies (designated AC2, AH12, DB10 and DD11) were derived from mice immunized with the large chondroitin sulphate proteoglycan isolated and purified from the bovine temporomandibular joint disc. The epitopes were partially characterized by enzyme-linked immunosorbent assays and staining patterns on immunoblots of intact proteoglycans and digests made with glycosidases and proteinases. All four monoclonal antibodies appeared to recognize some form of keratan sulphate although the epitopes for two (AC2 and DD11) were probably identical. One antibody (AH12) showed almost no reactivity with corneal keratan sulphate but stained a small keratan sulphate proteoglycan extracted from the disc, in addition to the large chondroitin sulphate proteoglycan. These antibodies were used for immunohistochemical staining of sections of the disc and showed that keratan sulphate associated with the large chondroitin sulphate proteoglycan was concentrated inside and away from the periphery of the structure but close to the inferior and superior surfaces, in a pattern which may reflect the adaptation of the extracellular matrix to the mechanical stresses placed on it by mastication.

Interaction of astrochondrin with extracellular matrix components and its involvement in astrocyte process formation and cerebellar granule cell migration

We have recently characterized a chondroitin sulfate proteoglycan from the murine central nervous system which is expressed by astrocytes in vitro and carries the L2/HNK-1 and L5 carbohydrate structures. In the present study, we provide evidence that its three core proteins of different size are similar in their proteolytic peptide maps and thus designate this group of structurally related molecules astrochondrin. During development, astrochondrin and the L5 carbohydrate were hardly detectable in the brain of 14-d-old mouse embryos by Western blot analysis. Expression of astrochondrin and the L5 epitope was highest at postnatal day 8, the peak of cerebellar granule cell migration and Bergmann glial process formation, and decreased to weakly detectable levels in the adult. Immunocytochemical localization of astrochondrin in the cerebellar cortex of 6-d-old mice showed association of immunoreactivity with the cell surface of astrocytes, including Bergmann glial processes and astrocytes in the internal granular layer or prospective white matter. Endfeet of astrocytes contacting the basal lamina of endothelial and meningeal cells and contact sites between Bergmann glial processes and granule cells also showed detectable levels of astrochondrin. Furthermore, granule cell axons in the molecular layer were astrochondrin immunoreactive. In the adult, astrochondrin immunoreactivity was weakly present in the internal granular layer and white matter. Both Fab fragments of polyclonal antibodies to astrochondrin and monovalent fragments of the L5 monoclonal antibody reduced the formation of processes of mature GFAP-positive astrocytes on laminin and collagen type IV, but not on fibronectin as substrata. Interestingly, the initial attachment of astrocytic cell bodies was not disturbed by these antibodies. Antibodies to astrochondrin also reduced the migration of granule cells in the early postnatal mouse cerebellar cortex. In a solid phase radioligand binding assay, astrochondrin was shown to bind to the extracellular matrix components laminin and collagen type IV, being enhanced in the presence of Ca2+, but not to fibronectin, J1/tenascin or other neural recognition molecules. Furthermore, astrochondrin interacted with collagen types III and V, less strongly with collagen types I, II, and IX, but not with collagen type VI. The interaction of astrochondrin with collagen types III and V was saturable and susceptible to increasing ionic strength, and could be competed by chondroitin sulfate, heparin, and dextran sulfate, but not by hyaluronic acid, glucose-6-phosphate, or neuraminic acid.(ABSTRACT TRUNCATED AT 400 WORDS)

Monoclonal antibodies directed against epitopes within the core protein structure of the large aggregating proteoglycan (aggrecan) from the swarm rat chondrosarcoma

The core protein of the large hyaline cartilage proteoglycan, aggrecan, is composed of six distinct domains: globular 1 (G1), interglobular, globular 2 (G2), keratan sulfate attachment, chondroitin sulfate (CS) attachment, and globular 3 (G3). Monoclonal antibodies that recognize epitopes in these domains were raised against Swarm rat chondrosarcoma aggrecan that was either denatured through reduction and alkylation or partially deglycosylated through chondroitinase ABC digestion or alkali elimination, the latter with or without sulfite addition. Monoclonal antibodies were further characterized for reactivity to purified aggrecan substructures including rat chondrosarcoma G1 and CS attachment domains, a recombinant rat chondrosarcoma G3 domain fusion protein, bovine articular cartilage G2 domain, and rat chondrosarcoma link protein (LP). Biochemical characterization of the specificities of these monoclonal antibodies indicated that one (1C6) recognized an epitope shared by both the G1 and the G2 domains; one (5C4) recognized an epitope shared by both LP and the G1 domain; one (7D1) recognized an epitope shared by both the G1 and the CS attachment domains; two (14A1 and 15B2) recognized epitopes in the CS attachment domain; one (14B4) recognized an epitope in the G3 domain; and one (13D1) recognized a ubiquitous epitope shared by the G1, G2, G3, and CS attachment domains of aggrecan and also LP. Collectively the specificities of these antibodies confirm the occurrence of multiple repeated epitopes (both carbohydrate and protein in nature) throughout the different domain structures of aggrecan. These antibodies have been proven to be useful for identifying aggrecan-like molecules in several connective tissues other than cartilage.

Isolation and characterization of bovine gingival proteoglycans versican and decorin

1. We have isolated, chemically and immunologically characterized versican and decorin from bovine gingiva. 2. Versican was of large molecular weight and the molecular size of the core protein was estimated to be greater than 200 kDa. 3. The glycosaminoglycan chains were susceptible to chondroitinase ABC and N-linked oligosaccharides were present on the protein core of the molecule. 4. Immunological studies provided evidence that a hyaluronic acid binding region was present in the core protein of versican. 5. The overall structure was similar to that of versican isolated from bovine sclera. 6. Decorin had a molecular weight of 102 kDa and its glycosaminoglycan chain was completely digested by specific glycosidases. 7. The partially deglycosylated core protein had a molecular weight of 55 kDa and N-linked oligosaccharides were present on the molecule.

A chondroitin sulfate proteoglycan that is developmentally regulated in the cerebellar mossy fiber system

It is known that the mammalian brain contains many kinds of proteoglycans, but almost all of them remain to be characterized. In this study, we prepared a monoclonal antibody against a phosphate-buffered saline-soluble brain proteoglycan (MAb 6B4). MAb 6B4 recognized a 600- to 1000-kDa chondroitin sulfate proteoglycan with a 250-kDa core protein (6B4 proteoglycan). The core protein of 6B4 proteoglycan carried the HNK-1 epitope. Immunohistochemical analysis of the adult rat brain indicated that this proteoglycan was expressed on the cell surfaces of a subset of neurons. In the hindbrain, 6B4 proteoglycan was highly expressed on the cerebellar Purkinje cells and Golgi cells, and at particular nuclei including the pontine nuclei and lateral reticular nucleus. Almost all of these nuclei were connected to the cerebellum through the mossy fiber system. A developmental study indicated that the expression of this proteoglycan changed dramatically during the formation of the cerebellar mossy fiber system. The mossy fibers from the pontine nuclei expressed 6B4 proteoglycan transiently from Embryonic Day 20 (E20) to Postnatal Day 30 (P30), during which time the axonal outgrowth and glomerular synapse formation occurred. The Purkinje cells, glomeruli, and Golgi cells began to be stained with MAb 6B4 from P10, P16, and P20, respectively. These expression stages correspond with the onset of their synapse formation. These results suggest that 6B4 proteoglycan is closely involved in the development of the cerebellar mossy fiber system.

Characterization of a chondroitin sulfate proteoglycan synthesized by monkey arterial smooth muscle cells in vitro

A monoclonal antibody against arterial smooth muscle cell chondroitin sulfate proteoglycan has been developed. Incubation of [35S]-methionine labeled proteoglycans with MAb 941 quantitatively immunoprecipitated all the chondroitin sulfate proteoglycan (CSPG) synthesized by these cells. Digestion of the immunoprecipitate with chondroitin AC lyase revealed one major protein band (Mr 420,000) and two minor bands (Mr 509,000 and 390,000) on SDS-PAGE that are composed of very similar peptides when analyzed by limited peptide digestion by S. aureus V8 protease. Additional studies demonstrated that this monoclonal antibody recognized an epitope on the chondroitin sulfate chains. However, only a minor subpopulation (5-12%) of the alkaline-borohydride released glycosaminoglycan chains was immunoprecipitated and this subset of chains was slightly larger than the non-immunoprecipitated chains. High pressure liquid chromatography analysis of the disaccharides generated from the immunoprecipitated glycosaminoglycan chains demonstrated that these chains were enriched in chondroitin-6-sulfate relative to chondroitin-4-sulfate (2:1) while that of the non-immunoprecipitated chains had a ratio of 1:1. These studies indicate that at least two distinct pools of chondroitin sulfate chains are present on all the chondroitin sulfate proteoglycan synthesized by arterial smooth muscle cells: a major population (89-95%) containing 6-sulfate and 4-sulfate in relatively equal proportion and a minor population (5-12%) which is hydrodynamically larger with a 6-sulfate to 4-sulfate ratio of 2:1.

Generation of a monoclonal antibody against avian small dermatan sulfate proteoglycan: immunolocalization and tissue distribution of PG-II (decorin) in embryonic tissues

Chick embryonic skeletal muscle synthesizes three major types of proteoglycans: large chondroitin sulfate proteoglycans, small dermatan sulfate proteoglycans and small heparan sulfate proteoglycans. A monoclonal antibody has been raised which recognizes the small dermatan sulfate proteoglycan. Immunoblot analysis of a partially purified preparation of skeletal muscle proteoglycans indicates that the antibody reacts with a molecule which migrates with an estimated Mr of 100,000. Prior treatment of the proteoglycans with chondroitinase results in immunostaining of a species of estimated Mr 45,000. These values for the intact proteoglycan and its core protein suggest that the antibody is directed against a proteoglycan of the PG-II or decorin class. Immunohistochemistry indicates a widespread distribution of the proteoglycan, which is localized in connective tissue septa of skeletal and cardiac muscle, dermis, tendon, bone, perichondrium and cornea. Immunoblot analysis of the proteoglycan core proteins from these tissues demonstrates that the antibody recognizes the same 45,000-dalton band in each tissue. The widespread tissue distribution is also consistent with the antibody being directed against an epitope of PG-II. Neither the glycosaminoglycan chains nor N-linked oligosaccharides are required for reactivity and the antibody cross-reacts with other avian material, but not mammalian. This antibody, which has been designated CB-1, reveals developmental stage-specific changes in the deposition of PG-II in embryonic limb bud and skeletal muscle.

Correlation of chondroitin sulfate proteoglycan expression on proliferating brain capillary endothelial cells with the malignant phenotype of astroglial cells

Human glioblastomas (five of five), the most malignant astroglial-derived tumors, specifically express a chondroitin sulfate proteoglycan that is recognized by monoclonal antibody 9.2.27 and localized to the glioma cell surface, proliferating endothelial cells, and the perivascular extracellular matrix within the tumor bed. In contrast, the expression of this proteoglycan in normal adult neocortex and white matter is limited to the smooth muscle of small arteries, while normal glia, endothelial cells, and endothelial cell basement membranes are nonreactive. Moreover, two anaplastic astrocytomas, representing medium-grade astroglial-derived tumors, fail to react with monoclonal antibody 9.2.27. In culture, glioblastoma and capillary brain endothelial cells specifically synthesize a 250-kDa core protein and a high-molecular-mass chondroitin sulfate proteoglycan, recognized by monoclonal antibody 9.2.27. These data suggest a correlation between the expression of this chondroitin sulfate proteoglycan on proliferating brain capillary endothelial cells and the malignant phenotype of astroglial cells. The prominent perivascular localization of chondroitin sulfate proteoglycan makes it a marker for both proliferating brain capillary endothelial cells and the most malignant transformed astroglial cells, thus providing an ideal target for the immunotherapy of glioblastoma.