Immunochemical and biochemical characterization of a glioma-associated extracellular matrix glycoprotein

Comparison of Dynamic Contrast-Enhancement Parameters between Gadobutrol and Gadoterate Meglumine in Posttreatment Glioma: A Prospective Intraindividual Study

BACKGROUND AND PURPOSE

Differences in molecular properties between one-molar and half-molar gadolinium-based contrast agents are thought to affect parameters obtained from dynamic contrast-enhanced imaging. The aim of our study was to investigate differences in dynamic contrast-enhanced parameters between one-molar nonionic gadobutrol and half-molar ionic gadoterate meglumine in patients with posttreatment glioma.

MATERIALS AND METHODS

This prospective study enrolled 32 patients who underwent 2 20-minute dynamic contrast-enhanced examinations, one with gadobutrol and one with gadoterate meglumine. The model-free parameter of area under the signal intensity curve from 30 to 1100 seconds and the Tofts model-based pharmacokinetic parameters were calculated and compared intraindividually using paired t tests. Patients were further divided into progression (n = 12) and stable (n = 20) groups, which were compared using Student t tests.

RESULTS

Gadobutrol and gadoterate meglumine did not show any significant differences in the area under the signal intensity curve or pharmacokinetic parameters of K ^trans, V_e, V_p, or K_ep (all P > .05). Gadobutrol showed a significantly higher mean wash-in rate (0.83 ± 0.64 versus 0.29 ± 0.63, P = .013) and a significantly lower mean washout rate (0.001 ± 0.0001 versus 0.002 ± 0.002, P = .02) than gadoterate meglumine. Trends toward higher area under the curve, K ^trans, V_e, V_p, wash-in, and washout rates and lower K_ep were observed in the progression group in comparison with the treatment-related-change group, regardless of the contrast agent used.

CONCLUSIONS

Model-free and pharmacokinetic parameters did not show any significant differences between the 2 gadolinium-based contrast agents, except for a higher wash-in rate with gadobutrol and a higher washout rate with gadoterate meglumine, supporting the interchangeable use of gadolinium-based contrast agents for dynamic contrast-enhanced imaging in patients with posttreatment glioma.

Review : Glial Boundaries and Scars: Programs for Normal Development and Wound Healing in the Brain

Early studies of glial boundaries, which are composed of immature astrocytes and extracellular matrix mol ecules (which they express), initially offered insight into the partitioning that occurs in the developing nervous system. More recently, however, it has been suggested that similar "boundaries" may have important roles in other processes occurring in the brain, including repair after traumatic brain injury. As more is understood about the expression and function of boundary molecules and glia, their potential importance is becoming apparent in numerous neuropathological conditions, including neurodegeneration and neuroregeneration in Alzheimer's and Huntington's diseases as well as in brain neoplasms. Furthermore, before we can hope to fully understand and facilitate regeneration in the compromised brain, our knowledge of the glial boundary, both during development and in the adult, must be more complete. The Neuroscientist 1:142-154, 1995

Monoclonal antibody therapy for malignant glioma

Monoclonal antibody (mAb) therapy is a rapidly evolving treatment immunotherapy modality for malignant gliomas. Many studies have provided evidence that the blood brain barrier-both at baseline and in the context of malignancy-is permissive for mAbs, thus providing a rationale for their use in treating intracranial malignancy. Furthermore, techniques such as convection enhanced delivery (CED) are being implemented to maximize exposure of tumor cells to mAb therapy. The mechanisms and designs of mAbs are widely varying, including unarmed immunoglobulins as well as immunoglobulins conjugated to radioisotopes, biological toxins, boronated dendrimers and immunoliposomes. The very structure of the immunoglobulin molecule has also been manipulated to generate a diverse armamentarium including single-chain Fv, bispecific T-cell engagers and chimeric antigen receptors. The targeted neutralization capacity of mAbs has been employed to modulate the immunologic milieu in hopes of optimizing other immunotherapy platforms. Many clinical trials have evaluated these mAb strategies to treat malignant gliomas, and the implementation of mAb therapy seems imminent and optimistic.

The evolution and application of techniques in molecular biology to human brain tumors: a 25 year perspective

Since the establishment of the AANS/CNS Section on Tumors in 1984, neurosurgeons have been actively involved in basic science research of human brain tumors that has moved the field forward considerably. Here, we chronicle the major advances that have been made with respect to our understanding of the concepts guiding the biology of human malignant brain tumors. Numerous technical advances in science, such as the development of gene transfer techniques, the polymerase chain reaction, the discovery of oncogenes and tumor suppressor genes, and the refinement of approaches to cancer cytogenetics have enabled researchers to identify many of the non-random genetic alterations associated with brain tumor growth, invasion, immunology, angiogenesis and apoptosis. These data led to some astounding progress, for example with the use of gene therapy, whereby in the 1990s several human clinical trials were conducted for patients with brain tumors. More recently, the human genome project has been completed providing a blueprint for the human species. What has followed are exciting new techniques in molecular biology such as transcriptional profiling, single nucleotide polymorphism (SNP)-arrays, array comparative genomic hybridization (array-CGH), microRNA profiling, and detection of epigenetic silencing of tumor suppressor genes. The cancer genome is now being sequenced at break neck speed using advanced DNA sequencing techniques. We are on the threshold of cataloguing the major genetic alterations observed in all human brain tumors. What will follow is modeling of these genetic alterations in systems that will allow for the development of novel pharmacotherapeutics and translational research therapies.

A pilot study: 131I-antitenascin monoclonal antibody 81c6 to deliver a 44-Gy resection cavity boost

The purpose of this study was to determine the feasibility and assess the efficacy and toxicity, among newly diagnosed malignant glioma patients, of administering (131)I-labeled murine antitenascin monoclonal antibody 81C6 ((131)I-81C6) into a surgically created resection cavity (SCRC) to achieve a patient-specific, 44-Gy boost to the 2-cm SCRC margin. A radioactivity dose of (131)I-81C6 calculated to achieve a 44-Gy boost to the SCRC was administered, followed by conventional external beam radiotherapy (XRT) and chemotherapy. Twenty-one patients were enrolled in the study: 16 with glioblastoma multiforme (GBM) and 5 with anaplastic astrocytoma. Twenty patients received the targeted 44-Gy boost (+/-10%) to the SCRC. Attributable toxicity was mild and limited to reversible grade 3 neutropenia or thrombocytopenia (n = 3; 14%), CNS wound infections (n = 3; 14%), and headache (n = 2; 10%). With a median follow-up of 151 weeks, median overall survival times for all patients and those with GBM are 96.6 and 90.6 weeks, respectively; 87% of GBM patients are alive at 1 year. It is feasible to consistently achieve a 44-Gy boost dose to the SCRC margin with patient-specific dosing of (131)I-81C6. Our study regimen ((131)I-81C6 + XRT + temozolomide) was well tolerated and had encouraging survival. To determine if selection of good-prognosis patients affects outcome associated with this approach, the U.S. Food and Drug Administration has approved a trial randomizing newly diagnosed GBM patients to either our study regimen or standard XRT plus temozolomide.

Targeted therapy for malignant gliomas

The identification of markers that are associated with tumour but not normal tissue has allowed the development of highly-specific targeted therapies. Monoclonal antibodies, either alone or linked to radioisotopes or toxins, have provided a powerful tool for research, as well as the basis for promising therapeutic agents with less side effects than standard radiotherapy or chemotherapy. A new class of drugs, the tyrosine kinase inhibitors, which interfere with the function of key molecules in cancer-promoting pathways, have had a dramatic effect in haematological malignancy and are being trialled in solid tumours, including glioma. Although the problem of achieving specific, high-level delivery of these various agents to tumours in the brain remains a major issue, encouraging early results with some targeted agents support the attractive theoretical principles of this new paradigm. Further work to identify new molecular targets and to develop agents exploiting them, is needed, as well as confirmation of their safety and efficacy by clinical trials.

Antitenascin-C monoclonal antibody radioimmunotherapy for malignant glioma patients

Adults with primary malignant glioma have an unacceptably poor outcome. Most of these tumors recur at or adjacent to the site of origin, which indicates that failure to eradicate local tumor growth is a major factor contributing to poor outcome. Therefore, locoregional therapies may improve local control and overall outcome for malignant glioma patients. Malignant gliomas selectively express several factors that are not present on normal CNS tissue. Regional administration of radiolabeled monoclonal antibodies targeting tumor-specific antigens expressed by malignant gliomas offers an innovative therapeutic strategy that has recently demonstrated encouraging antitumor activity and acceptable toxicity in clinical trials at a number of centers. Most studies have utilized monoclonal antibodies against tenascin-C, an extracellular matrix glycoprotein ubiquitously expressed by malignant gliomas. This review summarizes clinical trials performed using radiolabeled antitenascin-C monoclonal antibodies for malignant glioma patients to date and highlights future plans to further develop this therapeutic strategy.

Tumor resection cavity administered iodine-131-labeled antitenascin 81C6 radioimmunotherapy in patients with malignant glioma: neuropathology aspects

INTRODUCTION

The neurohistological findings in patients treated with targeted beta emitters such as (131)I are poorly described. We report a histopathologic analysis from patients treated with combined external beam therapy and a brachytherapy consisting of a (131)I-labeled monoclonal antibody (mAb) injected into surgically created resection cavities during brain tumor resections.

METHODS

Directed tissue samples of the cavity walls were obtained because of suspected tumor recurrence from 28 patients. Samples and clinical follow-up were evaluated on all patients (Group A) based on total radiation dose received and a subset of these (n=18; Group B, proximal therapy subset) who had received external beam therapy within <or=3 months of mAb therapy and undergoing 26 biopsies over 37 months. Histologic outcomes were "proliferative glioma," "quiescent glioma" and negative for neoplasm. Statistical analysis was used to assess the casual relation between total absorbed dose ((131)I-mAb+external beam) and histologic diagnosis.

RESULTS

The lesions observed after (131)I-mAb therapy were qualitatively similar to those reported for other types of radiation therapy; however, the high localized dose rate and absorbed doses produced by the short range of (131)I beta particles seem to have resulted in an earlier necrotic reaction in the tumor bed. Among all 28 (Group A) patients, median survival from tissue analysis after mAb therapy depended on histopathology and total radiation absorbed dose. Median survival for patients with tissue classified as proliferative glioma, quiescent glioma and negative for neoplasm were 3.5, 15 and 27.5 months, respectively. Without categorization, total dose was a significant predictor of survival (P<.002) where patients with higher doses had better prognoses. For example, median survival in patients receiving a total radiation dose greater than 86 Gy was 19 months compared with 7 months for those receiving less than 86 Gy.

CONCLUSIONS

Histopathologic analysis correlated with prognosis. Among all patients (Group A) there was a significant correlation between biopsy outcome, survival, and total radiation absorbed dose. Among the Group B proximal therapy patients, the neuropathologic changes were qualitatively similar to those described for external beam therapy and interstitial brachytherapy.

Salvage radioimmunotherapy with murine iodine-131-labeled antitenascin monoclonal antibody 81C6 for patients with recurrent primary and metastatic malignant brain tumors: phase II study results

PURPOSE

To assess the efficacy and toxicity of intraresection cavity iodine-131-labeled murine antitenascin monoclonal antibody 81C6 (131I-m81C6) among recurrent malignant brain tumor patients.

PATIENTS AND METHODS

In this phase II trial, 100 mCi of 131I-m81C6 was injected directly into the surgically created resection cavity (SCRC) of 43 patients with recurrent malignant glioma (glioblastoma multiforme [GBM], n = 33; anaplastic astrocytoma [AA], n = 6; anaplastic oligodendroglioma [AO], n = 2; gliosarcoma [GS], n = 1; and metastatic adenocarcinoma, n = 1) followed by chemotherapy.

RESULTS

With a median follow-up of 172 weeks, 63% and 59% of patients with GBM/GS and AA/AO tumors were alive at 1 year. Median overall survival for patients with GBM/GS and AA/AO tumors was 64 and 99 weeks, respectively. Ten patients (23%) developed acute hematologic toxicity. Five patients (12%) developed acute reversible neurotoxicity. One patient (2%) developed irreversible neurotoxicity. No patients required reoperation for radionecrosis.

CONCLUSION

In this single-institution phase II study, administration of 100 mCi of 131I-m81C6 to recurrent malignant glioma patients followed by chemotherapy is associated with a median survival that is greater than that of historical controls treated with surgery plus iodine-125 brachytherapy. Furthermore, toxicity was acceptable. Administration of a fixed millicurie dose resulted in a wide range of absorbed radiation doses to the SCRC. We are now conducting a phase II trial, approved by the US Food and Drug Administration, using patient-specific 131I-m81C6 dosing, to deliver 44 Gy to the SCRC followed by standardized chemotherapy. A phase III multicenter trial with patient-specific dosing is planned.

The cyclooxygenase inhibitor indomethacin modulates gene expression and represses the extracellular matrix protein laminin γ1 in human glioblastoma cells

The induction of cyclooxygenase-2 (COX-2) expression is associated with more aggressive gliomas and poor survival. Nonsteroidal anti-inflammatory drugs (NSAIDs) inhibit COX activity and have antitumorigenic properties. In this report, our initial aim was to determine if indomethacin would alter gene expression as measured by suppression subtractive hybridization (SSH). Three up-regulated and four down-regulated genes by indomethacin treatment were identified. Laminin gamma1, an extracellular matrix molecule, was the most significantly repressed gene. The repression of laminin gamma1 by indomethacin was confirmed by Northern and Western blot analyses and occurred in a concentration- and time-dependent manner at the protein level. Among several NSAIDs tested, only sulindac sulfide and indomethacin suppressed laminin gamma1 protein expression, and this repression was observed in both COX-expressing and -deficient cell lines, suggesting that laminin gamma1 repression by COX inhibitors was independent of COX. Indomethacin, at a concentration that represses laminin gamma1, inhibited glioblastoma cell invasion that was partially restored with additional human laminin protein containing gamma1 chain. The repression of laminin gamma1 by NSAIDs may be related to attenuation of invasion of brain tumors. These findings are important in understanding the chemopreventive activity of some NSAIDs and could be relevant for designing therapeutic strategies against glioblastoma.

Human/murine chimeric 81C6 F(ab')(2) fragment: preclinical evaluation of a potential construct for the targeted radiotherapy of malignant glioma

We have obtained encouraging responses in recent Phase I studies evaluating (131)I-labeled human/murine chimeric 81C6 anti-tenascin monoclonal antibody (ch81C6) administered into surgically-created tumor resection cavities in brain tumor patients. However, because the blood clearance is slow, hematologic toxicity has been higher than seen with murine 81C6 (mu81C6). In the current study, a series of paired-label experiments were performed in athymic mice bearing subcutaneous D-245 MG human glioma xenografts to compare the biodistribution of the fragment ch81C6 F(ab')(2) labeled using Iodogen to a) intact ch81C6, b) mu81C6, and c) ch81C6 F(ab')(2) labeled using N-succinimidyl 3-[(131)I]iodobenzoate. Tumor retention of radioiodine activity for the F(ab')(2) fragment was comparable to that for intact ch81C6 for the first 24 h and to that for mu81C6 for the first 48 h; as expected, blood and other normal tissue levels declined faster for ch81C6 F(ab')(2.) Radiation dosimetry calculations suggest that (131)I-labeled ch81C6 F(ab')(2) may warrant further evaluation as a targeted radiotherapeutic for the treatment of brain tumors.

Divalent Cations Modulate the Inhibitory Substrate Properties of Murine Glia-derived J1-160 and J1-180 Extracellular Matrix Glycoproteins for Neuronal Adhesion

J1-160 and J1-180 are developmentally late appearing J1 extracellular matrix glycoproteins derived from oligodendrocytes. They prevent adhesion of neurons (but not of astrocytes or fibroblasts) when offered as a substrate in mixture with laminin (Pesheva et al., J. Cell Biol., 109, 1765 - 1778, 1989). In the present study we have examined the influence of divalent cations on the inhibitory substrate properties of J1-160/180 glycoproteins towards adhesion of neurons. By metal chelate affinity chromatography, we show that J1-180, but not J1-160, binds Ca2+, while both J1 components are capable of binding Zn2+ and other divalent metal ions. Divalent cation binding was observed by gel filtration, aggregation assays with coated latex beads and electron microscopic examination to elicit aggregation of the molecules. Divalent cation binding also affects their non-permissive substrate properties towards neurons from early postnatal mouse cerebellum. Without divalent cations, J1-160 and J1-180 are inhibitory for substrate adhesion of neurons independently of the adhesive substrate present (laminin or poly-l-lysine). This effect is neutralized when J1-180 is preincubated with Ca2+ or Zn2+ prior to coating as substrate. In contrast, preincubation with Ca2+ ions does not affect the inhibitory substrate properties of J1-160 under these conditions. These observations show that J1-160/180 molecules may undergo self-aggregation in a divalent cation-dependent mechanism, which correlates with the neutralization of their inhibitory effect on neuronal adhesion. The aggregation state of the molecules may thus influence the process of myelination by a homophilic binding mechanism and determine the effectiveness of neurite extension during central nervous system development and under traumatic conditions in the adult.

Clinical impact and functional aspects of tenascin-C expression during glioma progression

The extracellular matrix protein tenascin-C is expressed in processes like embryogenesis and wound healing and in neoplasia. Tenascin-C expression in gliomas has been described previously; however, the relation to clinical data remains inconsistent. Generally, analysis of tenascin-C function is difficult due to different alternatively spliced isoforms. Our studies focus on changes in tenascin-C expression in human gliomas, correlating these changes with tumor progression and elucidating the functional role of the glioma cell-specific tenascin-C isoform pool. Eighty-six glioma tissues of different World Health Organization (WHO) grades were analyzed immunohistochemically for tenascin-C expression. The influence of the specific tenascin-C isoforms produced by glioblastoma cells on proliferation and migration was examined in vitro using blocking antibodies recognizing all isoforms. In general, tenascin-C expression increased with tumor malignancy. Perivascular staining of tenascin-C around tumor-supplying blood vessels was observed in all glioblastoma tissues, whereas in WHO II and III gliomas, perivascular tenascin-C staining appeared less frequently. The appearance of perivascular tenascin-C correlated significantly with a shorter disease-free time. Analysis of proliferation and migration in the presence of blocking antibodies revealed an inhibition of proliferation by around 30% in all 3 glioblastoma cell cultures, as well as a decrease in migration of 30.6-46.7%. Thus we conclude that the endogenous pool of tenascin-C isoforms in gliomas supports both tumor cell proliferation and tumor cell migration. In addition, our data on the perivascular staining of tenascin-C in WHO II and III gliomas and its correlation with a shorter disease-free time suggest that tenascin-C may be a new and potent prognostic marker for an earlier tumor recurrence.

Tumor-derived osteopontin is soluble, not matrix associated

The secreted phosphoprotein osteopontin (OPN), when immobilized on a surface, supports cell adhesion, prevents apoptosis of endothelial cells, and is a ligand for the alpha(v)beta(3) integrin, which is important in endothelial cell biology and neovascularization. OPN synthesized by tumor cells stimulates tumor growth, but the mechanism by which the protein acts remains unclear. One possibility, therefore, is that OPN may exert its effects on tumor growth by enhancing angiogenesis. While OPN is found at high levels in bone, where it is a component of the mineralized matrix, we have asked here whether OPN present in tumors is similarly extracellular matrix associated. We have shown that OPN is detectable in tumor extracts and in serum of tumor-bearing mice, and that the protein in tumors and in serum can be synthesized by both tumor and the host cells. Biochemical fractionation of tumor tissue confirmed that there is little if any association of OPN with the insoluble fraction. Immunochemical analysis of murine mammary tumors shows no co-localization of OPN with the extracellular matrix, identified by laminin staining. Ras-transformed cells in culture produce abundant OPN, however, the protein was found to be associated with the cell fraction but not with the matrix fraction. An enzyme-linked immunosorbent assay was used to demonstrate that OPN in conditioned medium from these cells fails to associate with extracellular matrix components, including laminin and fibronectin, in vitro. Recombinant OPN (GST-OPN) when coated onto a plastic surface can support human umbilical vein endothelial cell adhesion, suppressing apoptosis and allowing cell cycle progression, at concentrations from 1 to 50 microg/ml. Soluble GST-OPN in the same concentration range has no effect on HUVECs held in suspension. Thus, we conclude that OPN associated with tumors is primarily soluble, and that soluble OPN can neither support endothelial cell proliferation nor prevent apoptosis of these cells in the absence of adhesion.

Phase II trial of murine (131)I-labeled antitenascin monoclonal antibody 81C6 administered into surgically created resection cavities of patients with newly diagnosed malignant gliomas

PURPOSE

To assess the efficacy and toxicity of intraresection cavity (131)I-labeled murine antitenascin monoclonal antibody 81C6 and determine its true response rate among patients with newly diagnosed malignant glioma.

PATIENTS AND METHODS

In this phase II trial, 120 mCi of (131)I-labeled murine 81C6 was injected directly into the surgically created resection cavity of 33 patients with previously untreated malignant glioma (glioblastoma multiforme [GBM], n = 27; anaplastic astrocytoma, n = 4; anaplastic oligodendroglioma, n = 2). Patients then received conventional external-beam radiotherapy followed by a year of alkylator-based chemotherapy.

RESULTS

Median survival for all patients and those with GBM was 86.7 and 79.4 weeks, respectively. Eleven patients remain alive at a median follow-up of 93 weeks (range, 49 to 220 weeks). Nine patients (27%) developed reversible hematologic toxicity, and histologically confirmed, treatment-related neurologic toxicity occurred in five patients (15%). One patient (3%) required reoperation for radionecrosis.

CONCLUSION

Median survival achieved with (131)I-labeled 81C6 exceeds that of historical controls treated with conventional radiotherapy and chemotherapy, even after accounting for established prognostic factors including age and Karnofsky performance status. The median survival achieved with (131)I-labeled 81C6 compares favorably with either (125)I interstitial brachy-therapy or stereotactic radiosurgery and is associated with a significantly lower rate of reoperation for radionecrosis. Our results confirm the efficacy of (131)I-labeled 81C6 for patients with newly diagnosed malignant glioma and suggest that a randomized phase III study is indicated.

Tenascin-C in the cochlea of the developing mouse

Tenascin-C is a glycoprotein of the extracellular matrix that acts in vitro as both a permissive and a nonpermissive substrate for neurite growth. We analyzed, by immunocytochemistry, the distribution of tenascin-C along neural growth pathways in the developing mouse cochlea. In the spiral lamina, tenascin-C coexists in a region where nerve bundles arborize. In the organ of Corti, tenascin-C lines the neural pathways along pillar and Deiters' cells before and during the time of nerve fiber ingrowth. By embryonic day 16, tenascin-C is abundant on the pillar side of the inner hair cell but does not accumulate on the modiolar side until about birth, a time after the arrival of afferent fibers. The synaptic zones beneath outer hair cells are strongly labeled during the time when early events in afferent synaptogenesis are progressing but not during the time of efferent synaptogenesis. At the age when most neural growth ceases, tenascin-C immunoreactivity disappears. Faint tenascin-C immunolabeling of normal hair cells, strong tenascin immunolabeling in pathological hair cells of Bronx waltzer (bv/bv) mice, and staining for beta-galactosidase, whose gene replaces tenascin in a "knockout" mouse, indicate that hair cells supply at least part of the tenascin-C. The changing composition of the extracellular matrix in the synaptic region during afferent and efferent synaptogenesis is consistent with a role for tenascin in synaptogenesis. The presence of tenascin-C along the growth routes of nerve fibers, particularly toward the outer hair cells, raises the possibility that growth cone interactions with tenascin-C helps to guide nerve fibers in the cochlea.

Tenascin expression in elastotic cuffs of invasive ductal carcinoma of the breast

We studied immunohistochemically one thousand one hundred and thirty-seven cases of primary invasive breast cancers (NST) and adjacent normal mammary glands for tenascin expression, and compared their elastic content to verify if a relationship exists between tenascin expression and elastosis. Periductal, perivascular and stromal elastosis were graded on a scale from 0 to 3 (absent to massive). All carcinomas showed tenascin expression and elastosis with various histological appearances. In the adjacent breast, teanscon was distributed around the normal ducts or with extasia and uctal hyperplasia without atypia. Digestion of the sections with elastase prior to staining resulted in a loss of the specific staining reactions in all areas where elastosis was present. Tenascin staining was observed in the mesenchyme closely surrounding the neoplastic ducts and the cancer cell nests. Stromal tenascin staining appeared stronger in those carcinomas that exhibited marked desmoplastic reactions. The highly differentiated tumours contained more elastosis in their tumour tissue than the poorly differentiated ones, whereas tenascin expression was stronger in poorly differentiated tumours than well differentiated tumours. A strong staining for tenascin was observed in the elastotic cuff. Tenascin staining did not disappear afterwards with elastase. We did not find a statistically significant correlation between tenascin expression, elastosis and prognostic factors such as size of the tumour, lymph node metastasis, tumour necrosis and age. In our study tenascin proved to be an additional element in elastotic areas even though the significance of an association between elastosis and tenascin is still unknown, as is that of elastosis itself.

Organization of F-actin filaments in human glioma cell lines cultured on extracellular matrix proteins

Extracellular matrix (ECM) constituents likely play an important role in cell proliferation and the invasion of malignant human gliomas. We examined the formation of stress fibers and the growth of the human glioblastoma cell lines A172 and T98G cultured on collagen types I, IV, and V, laminin (LN), and fibronectin (FN). A172 cells cultured on LN and FN formed complete F-actin filaments after 24 h of culture and grew logarithmically after 48 h. In contrast, T98G cells on LN and FN reorganized only short F-actin filaments after 24 h of culture and grew rapidly after 72 h. However, on the collagen preparations, neither cell line formed definite stress fibers and both showed lower rates of cellular proliferation. Significantly positive correlation was observed between the relative intensity of F-actin filaments and the cell proliferation. The results indicate that the ability of ECM components to modulate the growth and differentiation of malignant glioma cells may be mediated, in part, by the assembly and disassembly of F-actin filaments.

Distinct sites on tenascin-C mediate repellent or adhesive interactions with different neuronal cell types

In this study we have determined the binding specificities of four different neuronal cell types to tenascin-C (TN-C) and laminin using a cell adhesion assay. TN-C was repulsive for small cerebellar neurons and PC12 phaeochromocytoma cells, since after short-term adhesion to the substrate-bound molecule with a maximum of cell binding at 45 min, the cells detached from the substrate and after 22 h only about 25% of the originally adherent cells were still bound. For N2A neuroblastoma cells and retinal cells TN-C was an adhesive substrate, since the number of adherent cells did not decrease after the initial attachment period. All four cell types adhered well to laminin at all time points studied. For short-term adhesion of small cerebellar neurons and PC12 cells two binding sites were identified on TN-C, one being localized within the epidermal growth factor-like repeats three to five and the second within fibronectin type III-like repeats three and four. One binding site for N2A and retinal cells was localized within fibronectin type III-like repeat seven. Binding of small cerebellar neurons to TN-C was dependent on Ca2+, but not on Mg2+ and was inhibitable by polyclonal antibodies to beta 1 integrin. Short-term adhesion of small cerebellar neurons was also inhibitable with a mixture of recombinant fragments of TN-C encompassing the whole molecule, although the specific inhibitory activity of this mixture was ten-fold lower on a molar basis when compared to the native molecule. Our observations indicate that different neuronal cell types use distinct binding sites on TN-C for repellent or adhesive interactions and that beta 1 integrin is involved in the recognition event leading to repulsion of small cerebellar neurons.

Embryonic expression of tenascin-X suggests a role in limb, muscle, and heart development

Tenascin-X (TN-X) is the newest member of the tenascin family of extracellular matrix proteins and it is highly expressed in muscular tissues during development. To gain insight into the possible functions of TN-X during development, we evaluated its expression in the rat embryo. Using an 800 bp cDNA encoding the fibrinogen-like domain of TN-X, we show that TN-X expression begins in migrating cells of the epicardium in the E12 heart. The epicardium provides progenitors of fibrous and vascular tissue to the developing heart. After the epicardium is complete, TN-X is expressed in the sub-epicardial space in association with developing blood vessels, and later by non-myocytes dispersed through the myocardial wall. A similar pattern of TN-X expression, first in connective tissue surrounding muscle, and then by a subset of cells within muscle, was seen in para-axial, body wall, craniofacial, and appendicular muscle. This pattern suggests a role in connective tissue cell migration and late muscle morphogenesis. TN-X is also highly expressed in the interdigital space at E15 and surrounding developing tendons, suggesting an additional role in cell fate determination. Although the pattern of TN-X expression is distinct from that of tenascin C, they are frequently expressed in close proximity. Indirect genetic evidence in humans suggests an essential function for TN-X, and the pattern of TN-X expression in heart, skeletal muscle, and limb is consistent with this hypothesis.

Tenascin in cerebrospinal fluid is a useful biomarker for the diagnosis of brain tumour

Tenascin, an extracellular matrix glycoprotein, has been reported to be expressed predominantly on glioma tissue in the CNS, both in a cell associated and an excreted form. Recently, a highly sensitive sandwich type enzyme immunoassay for quantitative determination of tenascin was developed. In the present study, the amount of tenascin in CSF was measured. An increase of tenascin in CSF (> 100 ng/ml) was found in patients with an astrocytic tumour. The concentration was significantly higher (> 300 ng/ml) in high grade astrocytoma (anaplastic astrocytoma and glioblastoma) and a further increase (> 1000 ng/ml) was found in cases of CSF dissemination of high grade astrocytoma. On the other hand, tenascin concentrations were less than 100 ng/ml in non-astrocytic tumours and non-neoplastic neurological diseases, except meningeal dissemination of tumour cells, meningeal stimulation by infection, and subarachnoid haemorrhage. In cases of treated astrocytomas in remission, tenascin was negligible (< 100 ng/ml) in the CSF. The measurement of tenascin in CSF is useful for differential diagnosis of brain tumours and monitoring of astrocytic tumours.

Serum tenascin levels in chronic liver disease

To evaluate the diagnostic significance of tenascin, the extracellular matrix glycoprotein in chronic liver disease, serum tenascin levels were measured by a newly developed ELISA in 21 patients with chronic persistent hepatitis, in 55 with chronic active hepatitis, in 59 with liver cirrhosis, in 31 with hepatocellular carcinoma, in 26 with acute hepatitis and in 66 healthy subjects. The serum tenascin level was significantly elevated in the patients with chronic active hepatitis, liver cirrhosis, hepatocellular carcinoma, and acute hepatitis when compared with the healthy subjects (p < 0.001). The serum tenascin level also increased with increasing severity of chronic liver diseases. A significant correlation was observed between the serum tenascin levels and serum levels of various extracellular matrix proteins such as type III procollagen N-aminoterminal peptide (PIIIP), laminin and the 7S domain of type IV collagen (p < 0.001). A strong positive correlation was observed between the serum tenascin levels and histologic findings, particularly in the degree of hepatic fibrosis. This is the first report documenting serum tenascin level increases in patients with various chronic liver diseases. The measurement of the serum tenascin levels may provide additional information relevant to the study of connective tissue.

Role of plasminogen activator and of 92-KDa type IV collagenase in glioblastoma invasion using an in vitro matrigel model

The invasive nature of human gliomas represents a major factor in preventing their total resection. The exact nature of the underlying mechanisms of tumor cell invasion are still unclear. In this study, we have quantitatively assayed a glioblastoma cell line for its ability to migrate through a polycarbonate filter coated with matrigel which contains a complex of multiple basement membrane components. At 48 h the glioblastoma cell line (U251) showed a rate of invasiveness of 42% and also dependent on the concentration of matrigel. The U251 cell line produced a urokinase type plasminogen activator and a 92-KDa type IV collagenase. Both enzymes were inhibited by the addition of uPA and 92-KDa type IV collagenase antibodies. Those same antibodies reduced the invasion rate of U251 cells from 42% to 12 and 21%, respectively. Similarly, the addition of epsilon-aminocaproic acid (a plasmin inhibitor) or tissue inhibitor of metalloprotease (TIMP2, a collagenase inhibitor) reduced the invasiveness of U251 cells from 42% to 14% and 10%, respectively. Additionally, the other two glioblastoma cell lines (LG11, UWR1) and astrocytes showed a rate of invasiveness at 41%, 61% and 12%, respectively. Finally, the addition of hyaluronic acid to the matrigel, a constituent of brain extracellular matrix, enhanced the rate of invasion. These findings provide evidence for the role of serine proteases and metalloproteases in facilitating the invasion of extracellular matrix components by glioblastoma cell line and suggest a therapeutic role for protease inhibitors in attempting to minimize the invasive propensity of gliomas.

Development of an in vitro extracellular matrix assay for studies of brain tumor cell invasion

Invasion of brain by tumor cells is an inherent feature of the malignant phenotype. Assays to quantitate invasiveness should provide a powerful tool to investigate this phenomenon. We have developed a modified in vitro assay to measure tumor cell invasion, attachment, and chemotaxis using a barrier of the complex basement membrane Matrigel on gelatin-coated filters. Within 5 hours, 7.8% of U251MGp and 2.6% of SF126 human malignant glioma cells invaded the Matrigel and filter, compared with 0.8% of normal human leptomeningeal cells. The extent of invasion was directly proportional to incubation time and filter pore size and inversely proportional to the Matrigel concentration. Cells from exponentially growing U251MGp cultures invaded more readily (10.9%) than cells from plateau-phase cultures (2.3%); however, labeling studies with bromodeoxyuridine showed that quiescent cells and rapidly dividing cells were equally capable of invading. This suggests that the mechanisms underlying invasion by malignant glioma cells are distinct from those underlying proliferation and indicates the need for therapy aimed specifically at invasive behavior. In a practical application of this assay to test a potential anti-invasive strategy, monoclonal antibodies to the beta subunit of an integrin receptor mediating attachment to the extracellular matrix inhibited invasion by U251MGp cells in a dose-dependent manner. This assay should allow evaluation of the cellular and molecular basis of brain tumor progression and perhaps aid the development of rationally designed drugs that limit tumor invasion. It may also allow prediction of the clinical behavior of neoplasms in individual patients.

Immunolocalization of tenascin and cellular fibronectins in diverse glomerulopathies

Frozen samples of minimal change glomerulopathy (MCG), and of membranous, segmental and diffuse lupus glomerulonephritis (MGN, SGN, DLGN) were studied to assess the distribution of tenascin (Ten), and the extradomains A and B (EDA- and EDB-) and oncofetal (Onc-) isoforms of cellular fibronectin (cFn). Cryosections were immunostained by the ABC method with specific monoclonal antibodies. In MCG, mesangial Ten and EDA-cFn reactions were increased. In MGN, mesangial Ten and EDA-cFn staining was enhanced except in segmental scars; convincing reactions were seen in cases with membranous transformation; spikes stained strongly. In SGN, variably intense staining for Ten and all cFn isoforms was seen in glomerular necrosis, proliferation and crescents; parietal epithelium EDA-cFn staining was noted. In DLGN, strong and extensive mesangial Ten and EDA-cFn staining was seen as were focal EDB- and Onc-cFn reactions. Parietal cells with and without crescents stained variably with all Mabs. Obsolete glomeruli were unreactive save for rare periglomerular Ten rims. Interstitial inflammation and fibrosis in MGN, SGN and DLGN had moderate to strong Ten and EDA-cFn staining with rare traces of EDB- and Onc-cFn. We conclude that enhanced Ten and EDA-cFn is a potentially reversible response to glomerular injury whereas the expression of EDB- and Onc-cFn apparently result from necrosis and/or cellular proliferation which lead to scarring. And, while mesangial cells are the major source of these molecules, epithelial cells might also partake in their synthesis.

Differential expression of tenascin after denervation, damage or paralysis of mouse soleus muscle

The expression of the extracellular matrix molecule tenascin was studied by immunocytochemistry and Western blotting in soleus muscles of adult mice after nerve damage (denervation), muscle injury (induced by enforced running or freezing) and functional block of synaptic transmission (botulinum toxin). Enhanced expression of tenascin in the extracellular spaces around focally damaged muscle fibres was found already 10 h after onset of running on a motor-driven treadmill which causes muscle injury in soleus muscle. Tenascin expression reached a peak at 2-3 days post-exercise, after which it declined gradually and became undetectable by two weeks after injury. Similarly, cryo-damage of soleus muscles in situ led to upregulation of tenascin. Chronic muscle denervation after sciatic nerve transection caused a persistent (studied up to 31 days) expression of tenascin at denervated endplates and in intramuscular nerve branches but not in other tissue compartments. Local application of botulinum toxin Type A, which results in muscle inactivity but not in tissue degeneration, however, did not induce tenascin expression 12 h to 12 days post-injection. Expression of tenascin after denervation and muscle damage, but its absence after paralysis, were verified by SDS-PAGE and Western blot analysis. Independent of the type of injury (muscle, nerve or both) the known major isoforms of mouse tenascin, as judged by M(r) comparison, were re-expressed, with no preponderance of individual M(r) forms. These results show that tenascin expression in adult muscles is induced by both axon and muscle fibre damage but not by muscle inactivity. In contrast, NCAM, in accordance with previous observations, showed enhanced expression both as a result of inactivity and in association with tissue repair.

Localization of janusin mRNA in the central nervous system of the developing and adult mouse

Janusin (formerly termed J1-160/180) is an oligodendrocyte-derived extracellular matrix molecule which is restricted to the central nervous system and which is expressed late during development (Pesheva et al., J. Cell Biol., 1765-1778, 1989). To gain insights into the molecule's morphogenetic functions and to identify its cellular source in vivo, we have studied the localization of janusin messenger RNA in the optic nerve, retina and spinal cord and the expression of janusin protein in the spinal cord of developing and adult mice. Moreover, we have analysed optic nerve cell cultures and retinal cell suspensions in double-labelling experiments using a janusin-specific anti-sense complementary RNA probe and cell type-specific antibodies to identify the cell types containing janusin transcripts. In developing animals, oligodendrocytes were strongly labelled with the janusin anti-sense cRNA probe during the period of myelination. The number of labelled cells and intensity of the hybridization signal decreased significantly with increasing age. Interestingly, expression of janusin was not confined to oligodendrocytes. Some neuronal cell types and type-2 astrocytes present in optic nerve cell cultures also contained janusin transcripts. In contrast to oligodendrocytes, the number and labelling intensity of neurons containing janusin transcripts remained constant during postnatal development and into adulthood. Expression of janusin protein in the spinal cord was developmentally regulated, with a peak of expression in 2- or 3-week-old animals. The molecule was visible in the white and grey matter. In myelinated regions, it was associated with myelinated fibres and accumulated at nodes of Ranvier. These observations suggest that janusin may be of functional relevance for myelination.

Immunohistochemical expression of tenascin in normal human salivary glands and in pleomorphic adenomas

The presence of the extracellular matrix glycoprotein tenascin was studied immunohistochemically in normal human salivary glands and in pleomorphic adenomas. Its expression was compared to that of fibronectin, and type IV collagen. In the normal salivary gland, tenascin was found with interruptions in periductal tissues, and continuously in blood vessels, fat cells and around nerve bundles. In pleomorphic adenoma, tenascin was detected surrounding the clusters of epithelioid cells, in areas with a myxoid and a chondroid matrix, and around some myoepithelial cells as a halo. As compared to fibronectin, there is a similar location of tenascin and fibronectin around tumor cell clusters but not in myxoid and chondroid matrices. Fibronectin was found around the cells in chondroid matrix. In conclusion, tenascin is not only found in malignant tumors but also in benign tumors such as pleomorphic adenoma. The presence of tenascin as a halo around myoepithelial cells suggests a role of these cells in development of myxoid and chondroid matrices.

A novel tenascin type III repeat is part of a complex of tenascin mRNA alternative splices

Sequence analysis of two human tenascin encoding cDNA clones from a cDNA library of the U251 glioblastoma cell line revealed the presence of a novel 276 bp tenascin type III fibronectin like repeat. This alternatively spliced type III repeat designated AD1 is located between the previously identified repeats 10 and 11 and has sequence homology with human, chicken and mouse tenascin type III repeats. These results show that tenascin has at least 16 consecutive fibronectin like type III repeats. PCR amplification of random primed mRNA with specific type III repeat primers revealed a pattern of multiple alternative splices of AD1 and flanking type III repeats. The alternative splice variants were confirmed by direct sequencing. Differences were observed in the expression of the various alternative splices of tenascin mRNA between tumor and normal cells and may thus indicate differences in tenascin isoform expression and function in normal and tumor cells. PCR and Southern analysis of genomic DNA indicate that AD1 is coded by a single exon present in both human and mouse genome.

Immunocytochemical localization of cell adhesion molecules in the developing and mature olfactory system

The localization of Ca+(+)-independent cell adhesion molecules (CAMs) in the developing and mature olfactory epithelium and bulb is reviewed. The CAMs included in this article are the neural cell adhesion molecule (N-CAM), the 180 kD component of N-CAM (N-CAM 180), the embryonic form of N-CAM (E-N-CAM), L1 glycoproteins, J1 glycoproteins, and the adhesion molecule on glia (AMOG). In addition, the expression of the L2-HNK-1 carbohydrate epitope, shared by N-CAM, L1, J1 and myelin-associated glycoprotein (MAG) in the adult olfactory epithelium and bulb has also been documented. For the localization of these molecules at the light and electron microscopic levels, immunocytochemical techniques were used and are described in detail. During development and organogenesis, the olfactory system exhibits a pattern of CAM expression similar to the general pattern described for the developing nervous system. In the adult olfactory system, however, a significant retention of CAMs characteristic for developmental and morphogenetic processes, such as E-N-CAM, AMOG, as well as the high molecular weight components of J1 glycoproteins, can be observed. The retention of these embryonic features are most likely associated with the cell turnover and high plasticity of this system. Moreover, the predominance of N-CAM 180 with respect to other components of N-CAM, as well as the absence of the L2/HNK-1 carbohydrate epitope, are also particular traits of the primary olfactory system which could be associated with its exceptional properties.

Neuronal cell adhesion molecule contactin/F11 binds to tenascin via its immunoglobulin-like domains

Adhesive interactions between neurons and extracellular matrix (ECM) play a key role in neuronal pattern formation. The prominent role played by the extracellular matrix protein tenascin/cytotactin in the development of the nervous system, tied to its abundance, led us to speculate that brain may contain yet unidentified tenascin receptors. Here we show that the neuronal cell adhesion molecule contactin/F11, a member of the immunoglobulin(Ig)-superfamily, is a cell surface ligand for tenascin in the nervous system. Through affinity chromatography of membrane glycoproteins from chick brain on tenascin-Sepharose, we isolated a major cell surface ligand of 135 kD which we identified as contactin/F11 by NH2-terminal sequencing. The binding specificity between contactin/F11 and tenascin was demonstrated in solid-phase assays. Binding of immunopurified 125I-labeled contactin/F11 to immobilized tenascin is completely inhibited by the addition of soluble tenascin or contactin/F11, but not by fibronectin. When the fractionated isoforms of tenascin were used as substrates, contactin/F11 bound preferentially to the 190-kD isoform. This isoform differs in having no alternatively spliced fibronectin type III domains. Our results imply that the introduction of these additional domains in some way disrupts the contactin/F11 binding site on tenascin. To localize the binding site on contactin/F11, proteolytic fragments were generated and characterized by NH2-terminal sequencing. The smallest contactin/F11 fragment which binds tenascin is 45 kD and also begins with the contactin/F11 NH2-terminal sequence. This implies that contactin/F11 binds to tenascin through a site within the first three Ig-domains.

The role of matrix molecules in regeneration of leech CNS

Extracellular matrix (ECM) molecules extracted from the leech central nervous system (CNS) provide substrates that induce extensive growth of processes of identified leech nerve cells in culture. Two ECM molecules, laminin and tenascin, have been identified. The laminin-like molecule has been purified and shown to be a cross-shaped molecule similar to vertebrate laminin with subunits of 340, 220, 180, and 160 kD. Purified laminin as a substrate induces rapid outgrowth of Retzius (R) and Anterior Pagoda (AP) cells in culture. The tenascin molecule has been partially purified. In electronmicrographs, leech tenascin, like vertebrate tenascin, has six arms of equal size joined in a central globule. Highly enriched fractions of leech tenascin induce rapid and extensive outgrowth of Retzius and AP cells in culture. Substrate molecules not only induce outgrowth of processes but also affect the growth patterns of individual nerve cells. Neurites are straight with few branches in laminin, but curved with profuse branches on tenascin. During regeneration of the CNS in the animal, laminin appears at new sites associated with growth cones. The appearance of laminin correlates with the accumulation of microglial cells. Thus, ECM molecules with growth-promoting activity for leech nerve cells in vitro appear to be involved in inducing regeneration and allowing the neurites to reconnect with former targets.

Localization and cellular source of the extracellular matrix protein tenascin in normal and fibrotic rat liver

The distribution and the cellular source of the novel extracellular matrix glycoprotein tenascin were studied in normal and fibrotic rat liver. Cryostat sections of normal rat livers, livers of rats treated with intraperitoneal injections of CCl4 and 4-day-old and 8-day-old primary fat-storing cell cultures were stained for tenascin and desmin using an immunoperoxidase procedure or a double-label immunofluorescence technique. Fat-storing cell cultures were metabolically labeled with 3H-proline. Radiolabeled proteins were immunoprecipitated from the supernatant with antitenascin antiserum and subjected to polyacrylamide gel electrophoresis. In normal rat livers, tenascin was detected discontinuously along the sinusoids, whereas portal tracts were devoid of staining. In fibrotic rat livers, tenascin was preferentially expressed in areas of cell damage, in slender septa or at connective tissue-parenchymal interfaces. The middle region of broad septa was negative. Desmin-positive fat-storing cells accumulated in areas strongly immunoreactive for tenascin, and double-label immunofluorescence showed cells positive for both tenascin and desmin. In fat-storing cell cultures, both intracellular positivity for tenascin and staining of extracellular fibers were seen. Gel electrophoresis of immunoprecipitated proteins revealed two major and three minor bands with molecular weights consistent with tenascin. We conclude that tenascin is a component of the extracellular matrix of both normal and fibrotic rat livers. The strong expression of tenascin in areas of cell damage, in "early" septa or at septal-parenchymal interfaces, in contrast to its absence from the middle region of mature septa, suggests a role in early matrix organization. Fat-storing cells synthesize and secrete tenascin.

Tenascin expression in human glioma cell lines and normal tissues

Tenascin expression was evaluated in 21 human glioma cell lines and in normal adult tissue extracts by Western and Northern blotting. The cell lines differed in their relative expression of tenascin in the cell-associated and supernatant compartments. Glioma cell line tenascin production was not uniformly stimulated by changes in fetal bovine serum concentration in the growth media. In most glioma cell lines and normal tissue extracts, reducing Western blots and Northern blots revealed two tenascin species, respectively: a major 340 kDa polypeptide and a 9 kb RNA transcript accompanied by a less intense 250 kDa polypeptide and 7 kDa RNA species. In U-87 MG and in normal adult kidney extracts, however, the 250 kDa band and 7 kb transcript were more prominent. Quantitation of tenascin in the glioma lines revealed variable levels that were significantly higher than those in the tissue extracts.

Density-dependent regulation of cell surface ?-glutamyl transpeptidase in cultured glial cells

A decline in cell surface gamma-glutamyl transpeptidase specific activity was previously observed to be concomitant with C6 glial cell proliferation. To elucidate the underlying factor(s) mediating gamma-glutamyl transpeptidase down-regulation, the effects of C6 cell density and culture conditions on cell surface transpeptidase activity levels were investigated. After 24 h of culture, the transpeptidase specific activities were inversely related to the initial plating densities. The lower-density cultures showed an induction within 24 h of plating. As the cultures proliferated, the specific transpeptidase activities declined to a common low level at post-confluency. The gamma-glutamyl transpeptidase down-regulation was unrelated to cell growth rate and was most pronounced during logarithmic proliferation. Induction and down-regulation of gamma-glutamyl transpeptidase activity at low cell densities were not a result of trypsinization. Supplementation of low-density cultures with conditioned medium, use of matrix-coated wells, or periodic replacement of growth media to prevent conditioning had minor effects on the decline of cell surface activity. Kinetic analysis showed that the Michaelis constants and the reaction mechanism were unaltered by cell density, indicating that down-regulation was not due to allosteric factors or an alteration in enzyme character. A reduction in the maximal velocity of cell surface transpeptidation at higher cell densities suggested that gamma-glutamyl transpeptidase down-regulation is related to the concentration of enzyme at the cell surface. Immunocytochemical localization of gamma-glutamyl transpeptidase demonstrated that gamma-glutamyl transpeptidase antigen levels decrease as C6 cell density increases. These results led us to propose that cell-cell contact stimulates the disappearance of gamma-glutamyl transpeptidase from the surface of cultured C6 glial cells.

Tenascin localization in skin wounds of the adult newt Notophthalmus viridescens

Earlier studies have shown that the extracellular matrix (ECM) protein tenascin (TN) is present between uninjured epidermal cells of urodele appendages, but is absent from most of the mesenchymally derived ECM. Following appendage amputation, this distribution is reversed. TN is lost from the epidermis and appears in the ECM of the stump and the regeneration blastema. In the present study, monoclonal and polyclonal antibodies to TN were used to localize this protein immunohistochemically in limbs of the adult urodele Notophthalmus viridescens at various stages following skin removal with or without damage to underlying muscle to determine 1) if the loss of TN by the epidermis and its gain by mesenchymal tissues occurs in wounds that do not require regulation by epigenetic mechanisms, and 2) if TN is present in the provisional wound matrix beneath migrating epidermal cells. In addition, skin explants were cultured on TN-coated dishes to learn if TN possesses active sites that can support epidermal cell migration. The results indicate that simple wounding leads to the same TN patterns as occurs following limb amputation. Tenascin loss from the epidermis could be seen as early as 6 hr after wounding, a time during which migrating epidermal cells are moving over the wound bed. During this period, there was no evidence of TN in the provisional wound matrix. In contrast to collagen, which supports considerable epidermal cell migration from skin explants, TN allowed no more migration than did the inactive protein, myoglobin.

J1/tenascin in substrate-bound and soluble form displays contrary effects on neurite outgrowth

The influence of J1/tenascin adsorbed to polyornithine-conditioned plastic (substrate-bound J1/tenascin) and J1/tenascin present in the culture medium (soluble J1/tenascin) on neurite outgrowth was studied with cultured single cells from hippocampus and mesencephalon of embryonic rats. Neurons at low density grew well on J1/tenascin substrates and extended neurites that were approximately 40% longer than on the polyornithine control substrate after 24 h in vitro. The neurite outgrowth promoting effect of substrate bound J1/tenascin was largely abolished in the presence of mAb J1/tn2, but not by mAb J1/tn1. In contrast to the neurite growth-promoting effects of substrate bound J1/tenascin, neurite outgrowth on polyornithine, laminin, fibronectin, or J1/tenascin as substrates was inhibited by addition of soluble J1/tenascin to the cultures. Neither of the two mAbs neutralized the neurite outgrowth-inhibitory properties of soluble J1/tenascin. In contrast to their opposite effects on neurite outgrowth, both substrate-bound and soluble J1/tenascin reduced spreading of the neuronal cell bodies, suggesting that the neurite outgrowth-promoting and antispreading effects are mediated by two different sites on the molecule. This was further supported by the inability of the mAb J1/tn2 to neutralize the antispreading effect. The J1/tn2 epitope localizes to a fibronectin type III homology domain that is presumably distinct from the putative Tn68 cell-binding domain of chicken tenascin for fibroblasts, as shown by electronmicroscopic localization of antibody binding sites. We infer from these experiments that J1/tenascin contains a neurite outgrowth promoting domain that is distinguishable from the cell-binding site and presumably not involved in the inhibition of neurite outgrowth or cell spreading. Our observations support the notion that J1/tenascin is a multifunctional extracellular matrix molecule.

Extracellular matrix molecules in development and regeneration of the leech CNS

As neurons grow to their targets their processes elongate, branch and form specialized endings into which are inserted appropriate ion channels. Our aim has been to analyse the role of the extracellular matrix molecules laminin and tenascin in inducing growth and in determining the form and physiological properties of growing neurites. A preparation in which development and regeneration can be followed at the cellular and molecular level in the animal and in tissue culture is the central nervous system (CNS) of the leech. In leech extracellular matrix (ECM) both laminin and tenascin are present; the molecules are structurally similar but not identical to their vertebrate counterparts. Tenascin extracted from leech ECM shows a typical hexabrachial structure whereas laminin shows a typical cruciform structure in rotary shadowed preparations. Leech laminin purified by means of a monoclonal antibody is a molecule of about 1000 kDa, with a polypeptide composition of 340, 200, 180 and 160 kDa. Substrates that contain tenascin or laminin produce rapid and reliable outgrowth of neurites by identified cells. A remarkable finding is that the outgrowth pattern produced by an individual neuron depends in part on its identity, in part on the substrate upon which it is placed. For example, a Retzius cell grows in a quite different configuration and far more rapidly on laminin substrate than does another type of neuron containing the same transmitter (serotonin); and the pattern of outgrowth of the Retzius cell is different on laminin and on the plant lectin Con A (concanavalin A). Thus Con A induces the growth of processes that are shorter, thicker, more curved and contain fewer calcium channels than those grown on laminin. To determine whether laminin can also influence neurite outgrowth in the animal, immunocytological techniques have been used to follow its distribution in the extracellular matrix of normal, developing and regenerating leech CNS. In adult leeches neuronal processes in the CNS are not in contact with laminin which is confined to the surrounding extracellular matrix. In embryos however, laminin staining appears between ganglionic primordia along the pathways that neurons will follow. Similarly, after injury to the adult CNS, laminin accumulates at the very sites at which sprouting and regeneration begin. How the laminin becomes redistributed to appear in the region of injury has not yet been established. Together these findings suggest a key role for laminin and for other extracellular matrix molecules.(ABSTRACT TRUNCATED AT 250 WORDS)

Purification and partial characterization of Xenopus laevis tenascin from the XTC cell line

We report here the purification of tenascin, an extracellular matrix molecule involved in the control of morphogenesis, from the conditioned medium of the Xenopus XTC cell line. Tenascin was purified by affinity chromatography on a column of the monoclonal antibody mAb TnM1; the molecule eluted from this column has a relative molecular mass of 210 kDa after reduction. Electrophoretic analysis under non-reducing conditions shows that the purified components are oligomeric disulfide-linked complexes which barely enter a 4% polyacrylamide gel. Upon rotary shadowing these molecules appear to possess a central globular domain to which pairs or triplets of arms are attached. Polyclonal antibodies have been raised against purified Xenopus tenascin. They recognise specifically the antigen on Western blots of XTC conditioned medium and adult brain, by immunofluorescence, these antibodies reveal large amounts of tenascin in the secretory vesicles as well as in the extracellular matrix of XTC cells. In the Xenopus tadpole, they stain the developing cartilage, the basal lamina of skin epidermis, myotendinous ligaments and restricted regions of the central nervous system.

Amino acid sequence of mouse tenascin and differential expression of two tenascin isoforms during embryogenesis

We have isolated cDNA clones for mouse tenascin and analyzed expression of tenascin mRNAs during embryonic development of the kidney and gut. The deduced amino acid sequence of the mouse tenascin cDNAs shows a modular structure of repeats similar to chicken and human tenascin. In mouse there are 14.5 cysteine-rich repeats with similarity to the EGF repeat, followed by several repeats with similarity to the type III repeat of fibronectin. A longer variant contains 13 fibronectin type III repeats, whereas a shorter splice variant of mouse tenascin lacks the 5 type III repeats that occur directly after the fifth repeat in the longer variant. Contrary to the chicken and human sequences, mouse tenascin does not contain an RGD sequence in the third type III repeat implicated in cell attachment, or in any other positions. In Northern hybridizations to RNA from primary embryonic fibroblasts, the cDNA clone M 20/1 detects two mRNAs with sizes close to 6 and 8 kb. This, and the other data presented here suggest that the two major mouse tenascin polypeptides arise through an alternative RNA splicing. The two major mRNAs are differentially expressed during development. The 8-kb mRNA is more prominent than the 6-kb mRNA throughout prenatal kidney development, but during postnatal development the ratio of the two mRNAs changes. A different expression pattern is seen in the developing gut where the 6-kb mRNA predominates during embryogenesis with the 8-kb mRNA appearing later. The mRNA data of the developing gut correspond with previous protein data, which showed that the shorter Mr 210,000 polypeptide predominates during earlier developmental stages and the larger Mr 260,000 polypeptide appears later in the embryonic gut (Aufderheide, E., and P. Ekblom. 1988. J. Cell Biol. 107:2341-2349).

Nerve growth factor mediates monosialoganglioside-induced release of fibronectin and J1/tenascin from C6 glioma cells

C6 rat glioma cells incubated in serum-free medium with D-[14C]glucosamine secrete, on stimulation with nerve growth factor (NGF) or monosialogangliosides (MSGs), several glycoproteins (Gps), the most prominent of which are a 270-, 220-, and 69-kDa Gp. Several growth factors, hormones, phorbol ester, and disialo- and trisialogangliosides did not stimulate secretion. Western blot analysis of the conditioned medium from C6 cells stimulated with NGF or MSG identified one distinct band of approximately 220 kDa for fibronectin and J1/tenascin, which comigrated. Antiserum to NGF prevented NGF-stimulated release and also blocked MSG-evoked release. The 220-kDa band was labeled after pulse labeling with [35S]methionine in the presence of NGF, and by a 15-min chase period radioactively labeled J1/tenascin could be immunoprecipitated. Tunicamycin drastically inhibited almost completely release of the 220-kDa Gp labeled by D-[14C]glucosamine or [35S]methionine. These results extend the range of neurotrophic properties attributed to NGF to cells of glial origin and suggest that NGF regulates secretion of extracellular matrix proteins. MSG stimulation of fibronectin and J1/tenascin secretion may be mediated by NGF or an NGF-like molecule also secreted by the C6 glioma cells.

IgA-binding structures in dermatitis herpetiformis skin are independent of elastic-microfibrillar bundles

Dermatitis herpetiformis (DH) is characterized in part by the presence of granular deposits of IgA in the papillary dermis just beneath the dermal-epidermal junction. The nature of the structures to which IgA binds in DH skin, however, has not been clearly demonstrated. Previous immunoelectron-microscopy studies using the peroxidase-antiperoxidase technique have concluded that the IgA may bind to abnormal elastic microfibrillar bundles. Recently, antibodies have been developed against a major component of the elastic microfibril bundles, fibrillin. In addition, another dermal matrix protein, hexabrachion, has been characterized and found in normal human skin in a distribution similar to the IgA deposits of DH. Utilizing antibodies against fibrillin, hexabrachion, and human IgA and immunoelectronmicroscopy with immunogold staining techniques, we have examined the skin from patients with DH in order to localize the IgA deposits. Normal-appearing skin from five patients with DH exhibited electron-dense patches within the dermis, which were not seen in skin from normal subjects. These structures were sometimes adjacent to the basement membrane zone, but appeared amorphous and without a well-defined fibrillar structure. The electron-dense patches were labeled with anti-human IgA, but not with antibodies to fibrillin or hexabrachion. The anti-IgA antibody did not label the normal basement membrane. These studies confirm the presence of abnormal electron-dense, amorphous structures in the skin of patients with DH. Due to this lack of association with the elastic microfibril bundles and the lack of labeling with antibodies against fibrillin, we suggest that these deposits are distinct from the microfibrillar bundles of elastic tissue and may represent IgA bound to degraded basement membrane or isolated dermal deposits of IgA.

The distribution of immuno-reactive tenascin in the epithelial-mesenchymal junctional areas of benign and malignant squamous epithelia

Tenascin is an extra cellular matrix glycoprotein which is distributed in the mesenchyme surrounding various organs during embryogenesis. It has also been demonstrated in some normal adult tissues and in the matrix of human tumours. The present study has been carried out to analyse the distribution of tenascin in non malignant and malignant skin disorders, in squamous cell carcinomas of the head and neck, in squamous cell carcinoma xenografts and in a squamous cell carcinoma cell line grown on collagen gel. Immunohistochemical localisation of tenascin was performed, using a monoclonal antibody specific for tenascin, by the indirect immunoperoxidase method with silver enhancement. Tenascin was heterogeneously distributed in the extra cellular matrix of squamous cell carcinomas and in squamous cell carcinoma xenografts. It was absent in basal cell carcinoma and in the squamous cell carcinoma cell line grown on collagen gel. The distribution of tenascin in squamous cell carcinoma and basal cell carcinoma is discussed in relation to tumour invasion and differentiation.