Gene therapy of gliomas

Malignant glioma formation is associated with characteristic genetic alterations, although epigenetic mechanisms may contribute in tumorigenesis. Until recently, our knowledge has mainly been based on chromosomal and molecular studies performed in the last two decades. This has increased tremendously with the advent of new technologies, in particular expression arrays for simultaneous analysis of thousands of genes. Consequently, gene therapy of gliomas may aim at molecular interference with 'gain of function' genes (oncogenes) or replacement of 'loss of function' genes (tumor suppressor genes). Such approaches require transgene expression in whole tumor cell populations (if not other mechanisms come into play) which cannot be achieved with current vector systems. Hence other strategies have been pursued which may be independent of genes actually involved in tumorigenesis. Microbial genes (e.g. herpes simplex virus thymidine kinase) may be transferred into the tumors allowing for prodrug activation (e.g. ganciclovir). Furthermore, cytokines or other immunomodulatory genes may be used for vaccination purposes which frequently involves ex vivo transfection of autologous tumor cells with such genes. These approaches proved promising in preclinical studies performed in cell culture and different inbred rodent models. A considerable number of clinical trials have been initiated based on these approaches. Although most therapeutic strategies proved safe, clinical responses fell short of expectations raised by preclinical results. This, to a large extent, has to be attributed to a lag in the development of efficient vector systems. Although much effort has been put into this area of research, neuro-oncologists are still in await of a vector system allowing for selective and efficient tumor cell transduction. This has led to increased interest in distinct but related strategies, e.g. oncolytic viruses or direct intra-tumoral delivery of anti-sense oligonucleotides.

Intracavitary Chemotherapy for Glioblastoma: Present Status and Future Directions

Considerable efforts have been invested to improve local control of the glioma disease although its infiltrative nature leading to whole brain involvement is a fundamental characteristic and antagonistic to this endeavour. The typically local recurrence of glioblastoma in about 80% of the cases has prompted intracavitary treatments of which presently only a biodegradable wafer containing carmustine has shown statistically significant benefit regarding survival in three phase III trials. Based on that proof of principle, many new developments are attempting to improve on this concept, introducing different agents with otherwise high systemic toxicity and poor penetration. New pharmacological formulations offer longer sustained release, better adaptation to the geometry of the resection cavity, and allow repeated administration. Should local recurrence become effectively controlled, significant progress can be made to increase survival with very limited local and virtually no systemic side effects. Since all agents so far show only limited activity against solid tumor, complete resection seems to be the prerequisite for effective local therapies.

[Diagnostic and therapeutical considerations in the treatment of giant aneurysms]

The treatment of giant aneurysms requires a thorough surgical and endovascular planning as this entity is accompanied by complex vascular and blood flow particularities. Even in experienced neurovascular centers the clinical outcome varies considerably. Within a series of 1386 aneurysm patients 72 (5%) giant (>25 mm) aneurysms were treated in our institution. Their age ranged between 26 and 81 years (medium age 52 years). 22 patients were suffering of a subarachnoid hemorrhage (SAH). Additionally there were 50 patients with nerve palsies or unspecific symptoms due to unruptured giant aneurysms (UGA). Treatment modalities included surgical clipping (n = 35), balloon occlusion of the ICA (n = 12), endovascular coiling (n = 7) or a combined regimen of balloon occlusion, surgical clipping and EC-IC bypass (n = 8). 10 patients could not be treated on due to their high age or minor clinical status (H&H IV and V). 6 of 15 (40%) SAH-patients were discharged without any complaints compared to 26% (12 of 47 patients) in the group of unruptured aneurysms. 1 SAH-patients (7%) versus 13 UGA (28%) patients suffered persisting nerve palsies or minor neurological disorders. 32% (n = 15) of the UGA-patients were suffering of major neurological deficits and required further professional help. 5 patients remained in a vegetative state, 3 of these had been admitted with an incidental finding of an UGA. 6 of 15 (40%) SAH-patients died, 5 of them admitted with H&H grade IV or V. However only 3 of 47 (6%) UGA patients died. 2 of these had a fatal SAH before treatment, 1 underwent EC-IC bypass surgery with insufficient hemispheric vascularization followed by gross infarction. The clinical status and age of the patient are significant factors influencing treatment associated morbidity and mortality. The individual vascular situation may lead to a complex therapeutical regimen thereby predisposes higher complication rates. We believe that surgical clipping is the first choice of treatment allowing temporarily clipping and reconstruction of the normal anatomy by shrinking or/and reconstructive clipping while reducing the mass effect. Whereas endovascular coiling alone is less favorable due to the packing of the coils a combined endovascular and surgical approach have to be considered in selected cases.

Diffuse arachnoidal enhancement of a well differentiated choroid plexus papilloma

INTRODUCTION

The case of a 38-year old man with a histologically benign choroid plexus papilloma arising within the fourth ventricle with en plaque growth around the brain stem and medulla is described in detail. Up to this point this particular growth pattern has not been published and is a rare presentation for this tumour.

CLINICAL PRESENTATION

The patient presented with a 1.5 year history of headache, nausea, and vomiting in the morning. Additional symptoms like blurred vision and gait ataxia lead to hospital admission. MRI demonstrated a homogeneously contrast-enhancing tumour completely filling the fourth ventricle and subsequent obstructive hydrocephalus. In addition Gd enhancement encasing the brain stem, the lower aspect of the medulla and the conus medullaris was seen suggesting a disseminated ependymoma or medulloblastoma.

INTERVENTION

An extensive resection of the tumour in the fourth ventricle and CP angle was performed. Infiltrative growth into the structures of the left CP angle and into the rhomboid fossa hampered complete removal. Surprisingly histological examination revealed a well-differentiated papillary choroid plexus papilloma without signs of anaplasia. On follow up imaging the Gd enhancement encasing the pons vanished completely. A growing cyst adjacent to a small tumour residuum left behind on the floor of the fourth ventricle led to re-operation after 8 months with complete removal.

DISCUSSION

This case presents several biological, neuroradiological and surgical aspects which make it noteworthy and we hope that the informations provided add to the understanding of these tumours, expand the differential diagnostic thinking of lesions which present with diffuse arachnoid Gd enhancement upon first presentation.

Head injury by gunshots from blank cartridges

BACKGROUND

Blank cartridge handguns are generally underestimated in their capacity to inflict serious and potentially life threatening injuries. The predominant reasons for these injuries are suicide or suicide attempts, followed by accidental injuries.

METHODS

A series of 26 gas gunshots to the neurocranium is presented. The injury pattern relevant to neurosurgical practice is illustrated in a case summary of 7 selected cases and the clinical courses as well as outcomes are presented.

RESULTS

The injury pattern demonstrates that the energy density of the gas jet and the high temperatures of the exploding gas volume cause extensive soft tissue injuries. In close-range shots the gas jet takes on physical properties of a projectile. In these injuries impression fractures and dislocation of bone fragments are common.

CONCLUSIONS

Gas handguns, contrary to public opinion, are dangerous weapons and may inflict potentially fatal injuries to the neurocranium when fired at close range. These weapons are frequently used in criminal or careless activities predominantly by young males. Extensive CNS injuries including hematomas, subarachnoid hemorrhage, foreign body contamination, and increased intracranial pressure are frequently observed.

Stability of a sufentanil-ropivacaine mixture in a glass and a PVC reservoir

BACKGROUND AND OBJECTIVE

Drug mixtures containing sufentanil may be unstable owing to absorption into the drug reservoirs of patient-controlled epidural analgesia systems that contain polyvinylchloride. The stability of sufentanil in a mixture of ropivacaine 0.2% in a 750 mL reservoir was therefore investigated.

METHODS

During simulated epidural infusions of 5 mLh(-1) at 25 degrees C, sufentanil concentrations were measured for 96 h. Samples were taken from the reservoir and from the end of the epidural catheter under the following conditions: into glass or polyvinylchloride reservoirs containing ropivacaine 0.2% with sufentanil 1, 0.75 or 0.5 microg mL(-1); and into polyvinylchloride reservoirs with ropivacaine 0.2% and sufentanil 1 microg mL(-1) which were stored for 4 weeks at 8 degrees C.

RESULTS

The different solutions remained stable over the observation period of 96 h. Using the same solutions, independent samples' ANOVA showed no difference in the sufentanil concentrations between the glass and polyvinylchloride reservoirs, or between the polyvinylchloride reservoirs when stored for 4 weeks. Correlations between the concentrations at the different measurement times were extremely high for the reservoir (r(min) = 0.98, r(max) = 1.00) and the catheter end (rmin = 0.86, r(max) = 1.00).

CONCLUSIONS

Sufentanil citrate at 0.5-1.0 microg mL(-1) in an admixture of ropivacaine 0.29 for 5 days, which is the usual period for postoperative epidural analgesia, remains stable in a polyvinylchloride reservoir. There is no change in the drug concentration even if the reservoir is stored for 4 weeks at 8 degrees C.

Oncoretrovirus and lentivirus vectors pseudotyped with lymphocytic choriomeningitis virus glycoprotein: generation, concentration, and broad host range

Lymphocytic choriomeningitis virus (LCMV) is a noncytopathic arenavirus shown to infect a broad range of different cell types. Here, we combined the beneficial characteristics of the LCMV glycoprotein (LCMV-GP) and those of retroviral vectors to generate a new, safe, and efficient gene transfer system. These LCMV-GP pseudotypes were systematically compared with vectors containing the widely used amphotropic murine leukemia virus envelope (A-MLVenv) or the vesicular stomatitis virus G protein (VSV-G). Production of LCMV-GP-pseudotyped oncoretroviral and lentiviral vectors by transient transfection resulted in vector titers similar to those with A-MLVenv or VSV-G. In contrast to A-MLVenv particles, LCMV-GP pseudotypes could be efficiently concentrated by ultracentrifugation without loss of vector titer. Unlike the cell-toxic VSV-G, a stable retroviral packaging cell line constitutively expressing LCMV-GP could be established. Vectors pseudotyped with LCMV-GP efficiently transduced many cell lines from different species and tissues relevant for gene therapy. Transduction of human glioma cells was studied in detail. These cells are a major target for cancer gene therapy and were transduced more efficiently with LCMV-GP-pseudotyped vectors than with the generally used A-MLVenv particles. The high stability, low toxicity, and broad host range make LCMV-GP-pseudotyped vectors attractive for gene transfer applications. The recombinant LCMV-GP-pseudotyped vectors will also allow functional characterization of naturally occurring and recombinant LCMV-GP variants.

Thromboxane synthase inhibitors induce apoptosis in migration-arrested glioma cells

OBJECTIVE

Because of the wide dissemination of malignant glioma cells by the time that malignant glioma is diagnosed, anti-invasive strategies that are designed to limit their further spread may be of little value unless mechanisms of the invasive cascade can be used to render invasive cells susceptible to cytoreductive treatments. We recently determined that elevated thromboxane synthase gene expression and enzymatic activity are associated with a highly migratory phenotype of glioma cells in vitro and that specific inhibitors of this enzyme block cell migration. Interference with this inherent phenotype of malignant gliomas also affects glioma cell proliferation and apoptosis.

METHODS

To study the effect of thromboxane synthase inhibitors on motility, metabolic activity, and cell death, we used five human glioma cell lines, four glioblastoma-derived, low-passage cell cultures, normal human astrocytes, and fibroblasts. Motility was measured in a monolayer migration assay. Caspase activation as an early event in apoptotic cell death was assessed using a caspase 3 cleavage assay. Intracellular deoxyribonucleic acid (DNA) fragmentation was detected by enzyme-linked immunosorbent assay quantification of histone-complexed DNA. Subsequent cell death was scored by trypan blue exclusion.

RESULTS

In this study, we demonstrate that the treatment of human glioma cells with the specific thromboxane synthase inhibitor furegrelate leads first to caspase activation (detectable 6 h after treatment), then to DNA fragmentation (24-48 h after treatment) and subsequent cell death. Caspase inhibitors abrogate this effect. Furthermore, the inhibition of thromboxane synthase by furegrelate increases cells' susceptibility to the induction of DNA fragmentation by camptothecin, etoposide, N,N'-bis(2-chloroethyl)-N-nitrosourea, and anti-CD95 antibodies. No induction of apoptosis was observed in normal astrocytes and fibroblasts.

CONCLUSION

These data indicate that thromboxane synthase may represent a vortex of divergent signaling cascades that regulate motility and apoptosis in glioma cells. This paradigm may offer a novel perspective in the treatment of patients with malignant gliomas.

Tamoxifen sensitivity-testing of glioblastomas: comparison of in vitro and in vivo results

BACKGROUND

Only less than half of the patients with malignant gliomas respond to a continuous high dose Tamoxifen (TAM) and/or Carboplatin (CP)-treatment. Therefore, a method for predicting the efficacy of TAM-treatment would be desirable.

METHODS

Paralleling a clinical study, the predictive value of in vitro-sensitivity testing of TAM and TAM's metabolite 4-OH-TAM in primary cultures of tumour explants from 15 of a total of 50 patients was examined. Additionally, the influence of TAM, 4-OH-TAM, and CP on the proliferation of established glioblastoma cell lines and of those explanted from athymic nude mice and re-established in cell culture was investigated. Human glioblastomas xenotransplanted subcutaneously into athymic nude mice and subsequently treated with TAM and/or CP were examined in a parallel in vivo-study.

FINDINGS

TAM-chemosensitivity-testing of glioblastomas failed to predict the clinical response to TAM-treatment in our patients and did not correlate with the in vivo-TAM-response of tumours xenotransplanted into nude mice. TAM's and 4-OH-TAM's ability to inhibit growth of various glioblastoma cell lines in vitro in very similar concentrations was shown to be a consistent phenomenon which seems to be independent of the in vivo response in either patients or mice as previous hosts. However, CP's antiproliferative effect on glioblastomas in vivo was paralleled by respective in vitro results. Whereas TAM showed to mediate its in vitro antiproliferative effect by inducing apoptosis in most cell lines examined, CP-treatment lead to necrosis of cells.

INTERPRETATION

Combining the results obtained from our human and mouse studies, it has to be postulated that host factors other than the sensitivity to TAM of the individual cell, determine the efficacy of TAM-treatment in vivo.

The influence of tamoxifen on the secretion of transforming growth factor-beta2 (TGF-beta2) in glioblastomas: in vitro and in vivo findings

BACKGROUND

Only a minority of patients with malignant gliomas respond to continuous high-dose tamoxifen (TAM) treatment. Therefore a method to predict the efficiency of TAM-treatment would be desirable. Analogous to previous studies in breast cancer patients, we investigated whether the dynamics of TGF-beta2 plasma levels allow the prediction of response to TAM-treatment in glioblastoma patients as well.

MATERIALS AND METHODS

TGF-beta2 plasma levels of glioblastoma patients treated with 200 mg TAM/day on a continuous basis and of control patients not treated with TAM were measured by using an ELISA. In addition, the effect of TAM and 4-OH-TAM on the secretion of TGF-beta2 by established glioma cell lines as well as the effect of TGF-beta2 itself on cell proliferation were investigated in vitro.

RESULTS

The effect of TAM on TGF-beta2 plasma levels did not correlate with the clinical response to TAM-therapy in glioblastoma patients. The in vitro experiments showed that TAM and 4-OH-TAM stimulate established glioma cell lines to increase their secretion of TGF-beta2. Externally added TGF-beta2 (nM) had no effect on cell proliferation of the same cell lines.

CONCLUSION

In contrast to breast cancer patients, the clinical response to TAM in glioblastoma patients is not reflected by changes of TGF-beta2 plasma levels. It has to be assumed that, despite an increase of TGF-beta2 production by glioblastoma cells in response to TAM in vitro, such elevated production in vivo does not reach the plasma due to either the lower tumor burden in glioblastoma disease compared to breast cancer patients or due to some local sequestration process.

Cyclo-oxygenase inhibitors and thromboxane synthase inhibitors differentially regulate migration arrest, growth inhibition and apoptosis in human glioma cells

We have previously identified thromboxane synthase as an important regulator of glioma cell migration. Inhibitors of this enzyme abrogate cell motility and induce apoptosis. However, the formation rate of thromboxanes is indirectly dependent on the activity of cyclo-oxygenase, which represents the rate-limiting step in the synthesis of prostaglandins and thromboxanes. In this study we have analyzed the expression of COX-1 and COX-2 in glioma cell lines and biopsies of glial tumors. In normal glia no expression of both COX isoforms was present, however, reactive astrocytes and glial tumors of all grades demonstrated expression of both COX-1 and COX-2. In contrast to inhibitors of thromboxane synthase, selective and non-selective cyclo-oxygenase inhibitors did not block cell motility. Specific COX-2 inhibitors resulted in growth inhibition and induction of intracellular DNA fragmentation indicative of apoptotic cell death. Treatment of glioma cells with thromboxane synthase inhibitors had a synergistic effect on induction of apoptosis by camptothecin, whereas COX inhibitors had not. Furthermore, combined treatment using COX-2 inhibitors and specific thromboxane synthase inhibitors did not show a synergistic increase of apoptosis. These data indicate that COX inhibitors and thromboxane synthase inhibitors influence apoptosis in glioma cells through different pathways. We hypothesize that, in contrast to the COX-2 inhibitors, thromboxane synthase inhibitors block the invasive phenotype of glioma cells and therefore increase the pro-apoptotic disposition of the cells and increase the susceptibility to induced apoptosis. This effect may be independent of prostaglandin synthesis controlled by cyclo-oxygenases.

Multimodal fetal transesophageal echocardiography for fetal cardiac intervention in sheep

BACKGROUND

The overall performance of available mechanical intravascular ultrasound catheters for fetal transesophageal echocardiography during fetoscopic fetal cardiac interventions in sheep has been limited by radioelectronic interference, low system frame rates, and low acoustic outputs. Therefore, a more reliable device is desired for human fetoscopic surgical procedures.

METHODS AND RESULTS

We assessed the potential of a newly available 10-French phased-array intravascular ultrasound catheter for multimodal fetal transesophageal echocardiography in 5 fetal sheep between 78 and 98 days of gestation (term, 145 to 150 d). The intravascular ultrasound catheter was easily inserted through the mouth into the esophagus in all 5 sheep fetuses (mean weight, 600 g), and it permitted high-quality 2D imaging of the fetal heart in vertical imaging planes that were validated by MRI. Color Doppler and pulsed Doppler imaging permitted clear assessment of fetal cardiovascular flows and recording of velocity-time integral tracings of the fetal heart and great vessels. The vertical imaging planes were particularly useful to demonstrate interventional material inside the fetal heart and great vessels.

CONCLUSIONS

Our early experience with the phased-array intravascular ultrasound catheter indicates that multimodal fetal transesophageal echocardiography has now become possible in these smallest of patients.

Inhibition of glioma angiogenesis and growth in vivo by systemic treatment with a monoclonal antibody against vascular endothelial growth factor receptor-2

Using an orthotopic intracerebral model, we investigated whether systemic treatment with DC101, a monoclonal antibody against vascular endothelial growth factor receptor (VEGFR)-2, could inhibit angiogenesis and the growth of human glioblastoma cells in severe combined immunodeficient mice. Intraperitoneal treatment with DC101, control IgG, or PBS was initiated either on day 0 or, in another series, on day 6 after tumor cell implantation, and animals were killed approximately 2 weeks after tumor cell injection. Tumor volumes in animals treated with DC101 were reduced by 59 and 81% compared with IgG and PBS controls, respectively (P < 0.001), when treatment was initiated immediately, and similar results were obtained when treatment started on day 6. Microvessel density in tumors of DC101-treated animals was reduced by at least 40% compared with animals treated with control IgG or PBS (P < 0.01). We observed a reduction in tumor cell proliferation and an increase in apoptosis in DC101-treated animals (P < 0.001). However, in mice treated with DC101, we also noticed a striking increase in the number and total area of small satellite tumors clustered around, but distinct from, the primary. These satellites usually contained central vessel cores, and tumor cells often had migrated over long distances along the host vasculature to eventually reach the surface and spread leptomeningeally. We conclude that systemic antagonization of VEGFR-2 can inhibit glioblastoma neovascularization and growth but can lead to increased cooption of preexistent cerebral blood vessels. Therefore, a combination of different treatment modalities which also include anti-invasive therapy may be needed for an effective therapy against glioblastoma, and the use of an antibody against VEGFR-2 may be one effective component.

The IGF/IGFBP system in CNS malignancy

The insulin-like growth factor (IGF) system includes IGF-I and IGF-II, the type I and type II IGF receptors, and specific IGF binding proteins (IGFBP-1 to IGFBP-6). These factors regulate both normal and malignant brain growth. Enhanced expression of IGF-I and IGF-II mRNA transcripts has been demonstrated in gliomas, meniningiomas, and other tumours. Abnormal imprinting of IGF-II occurs in gliomas, medulloblastomas, and meningiomas. Both types of IGF receptor are expressed in gliomas and, in particular, the type I IGF receptor appears to be upregulated in malignant brain tissue. Antisense IGF-I receptor mRNA induces an antitumour response, resulting in complete brain tumour regression. Clinical trials for the treatment of brain tumours in humans based on a gene transfer protocol using IGF-I receptor antisense are under way. All six IGFBPs are expressed to a variable extent in brain tumours. High concentrations of IGFBP-2 are found in cerebrospinal fluid from patients with malignant central nervous system tumours; therefore, IGFBP-2 might be a useful marker for these tumours. IGFBP-4 appears to be a negative regulator of tumour proliferation. Both in vitro and in vivo experiments suggest that the IGF system represents an important target for the treatment of malignant central nervous system tumours and the ongoing trials should provide valuable information for future therapeutic approaches.

Dictyostelium cells' cytoplasm as an active viscoplastic body

We applied a recently developed microrheology technique based on colloidal magnetic tweezers to measure local viscoelastic moduli and active forces in cells of Dictyostelium discoideum. The active transport of nonmagnetic beads taken up by phagocytosis was analyzed by single particle tracking, which allowed us to measure the length of straight steps and the corresponding velocities of the movements. The motion consists of a superposition of nearly straight long-range steps (step length in the micrometer range) and local random walks (step widths about 0.1 microm). The velocities for the former type of motion range from 1 to 3 microm/s. They decrease with increasing bead size and are attributed to rapid active transport along microtubuli. The short-range local motions exhibit velocities of less than 0.5 microm/s and reflect the internal dynamics of the cytoplasm. Viscoelastic response curves were measured by application of force pulses with amplitudes varying between 50 pN and 400 pN. Analysis of the response curves in terms of mechanical equivalent circuits yielded cytoplasmic viscosities varying between 10 and 350 Pa s. Simultaneous analysis of the response curves and of the bead trajectories showed that the motion of the beads is determined by the local yield stress within the cytoplasmic scaffold and cisternae, which varies between sigma = 30 Pa and 250 Pa. The motion of intracellular particles is interpreted in terms of viscoplastic behavior and the apparent viscosity is a measure of the reciprocal rate of bond breakage within the cytoplasmatic network. The viscoelastic moduli are interpreted as dynamic quantities which depend sensitively on the amplitude of the forces, and the rate of bond breakage is determined by the Arrhenius-Kramers law with the activation energy being reduced by the work performed by the applied force. In agreement with previous work, we provide evidence that the myosin II-deficient cells exhibit higher yield stresses, suggesting that the function of myosin II as a cross-linker is taken over by the other (non-active) cross-linkers.

(E)-5-(2-bromovinyl)-2'-deoxyuridine potentiates ganciclovir-mediated cytotoxicity on herpes simplex virus-thymidine kinase--expressing cells

Tumor cells expressing the thymidine kinase gene of the herpes simplex virus (HSV-tk) are rendered highly susceptible to the cytotoxic effects of different antiherpes drugs. In an attempt to enhance cytotoxicity of this therapeutic approach in glioma and other tumor cell lines transduced with the HSV-tk gene, we evaluated tumor cell killing following co-administration of two different prodrugs metabolized by HSV-tk, (E)-5-(2-bromovinyl)-2'-deoxyuridine (BVDU), and ganciclovir (GCV). In 8 of 12 cell lines investigated, addition of BVDU in concentrations showing no cytotoxic effect or only limited cytotoxicity could enhance GCV-mediated cell killing by as much as one order of magnitude. In co-cultures consisting of HSV-tk(+) (9L STK) and HSV-tk(-) (9L wild-type) cells, we also observed potentiation of GCV-mediated cytotoxicity in the presence of BVDU, suggesting strongly enhanced bystander cell killing. BVDU is thought to exert its cytotoxic effect through inhibition of thymidylate synthase activity or by incorporation into replicating DNA. Both effects could be observed in all HSV-tk--expressing cells investigated, including cell lines which did not exhibit cytotoxicity after incubation with BVDU. These findings argue against current concepts of BVDU-mediated cytotoxicity in HSV-tk--expressing cells. Taken together, our data suggest that gene therapy utilizing prodrug activating enzymes may be rendered more effective by simultaneous treatment with two different prodrugs metabolized by the same enzyme.

Expression and localization of scatter factor/hepatocyte growth factor in human astrocytomas

Scatter factor/hepatocyte growth factor (SF/HGF) is a pleiotropic cytokine that has been implicated in glioma invasion and angiogenesis. The SF/HGF receptor, MET, has been found to be expressed in neoplastic astrocytes as well as in endothelial cells of the tumor vasculature. Both SF/HGF and MET expression have also been described to correlate with the malignancy grade of human gliomas. However, most glioblastoma cell lines lack SF/HGF expression, raising the question of the cellular origin of SF/HGF in vivo. Using in situ hybridization, we analyzed glioblastomas, anaplastic astrocytomas, diffuse astrocytomas, pilocytic astrocytomas, and normal brain for the expression of SF/HGF mRNA. We detected strong SF/HGF expression by the majority of the tumor cells and by vascular endothelial cells in all glioblastoma specimens analyzed. Combined use of in situ hybridization with fluorescence immunohistochemistry confirmed the astrocytic origin of the SF/HGF-expressiong cells. In contrast, CD68-immunoreactive microglia/macrophages, as well as vascular smooth muscle cells reactive to alpha-smooth muscle actin, lacked SF/HGF expression. In anaplastic, diffuse, and pilocytic astrocytomas, SF/HGF expression was confined to a subset of tumor cells, and signals were less intense than in glioblastomas. In addition, we detected SF/HGF mRNA in cortical neurons. SF/HGF expression was not up regulated around necroses or at tumor margins. MET immunoreactivity was observed in GFAP-expressing astrocytic tumor cells and endothelial cells as well as in a subset of microglia/macrophages. We conclude that in vivo, both autocrine and paracrine stimulation of tumor cells and endothelium through the SF/HGF-MET system are likely to contribute to tumor invasion and angiogenesis. Lack of SF/HGF expression by most cultured glioblastoma cells is not representative of the in vivo situation and most likely represents a culture artifact.

Treatment of malignant glioma: a problem beyond the margins of resection

The treatment of malignant glioma remains problematic. Surgical removal followed by external beam irradiation represents a standard treatment that has demonstrated a prolonged time to progression and survival. However, the capacity to locally invade normal brain invariably leads to formation of a recurrent tumor most often immediately adjacent to the site of resection. This clinical everyday experience prompts the hypothesis that improved local control of the tumor may translate into a delayed time to progression and possibly survival, specifically because systemic chemotherapy for most of these tumors has failed to significantly improve survival. Local treatment strategies including chemotherapy, gene therapy, and immunotherapy are rapidly developing and progressing to clinical trials. Several theoretical considerations suggest that these approaches may be promising in the treatment of brain tumors.

Molecular genetic alterations on chromosomes 11 and 22 in ependymomas

Ependymomas arise from the ependymal cells at different locations throughout the brain and spinal cord. These tumors have a broad age distribution with a range from less than 1 year to more than 80 years. In some intramedullary spinal ependymomas, mutations in the neurofibromatosis 2 (NF2) gene and loss of heterozygosity (LOH) on chromosome arm 22q have been described. Cytogenetic studies have also identified alterations involving chromosome arm 11q, including rearrangements at 11q13, in ependymomas. We analyzed 21 intramedullary spinal, 14 ventricular, 11 filum terminale and 6 intracerebral ependymomas for mutations in the MEN1 gene, which is located at 11q13, and mutations in the NF2 gene, which is located at 22q12, as well as for LOH on 11q and 22q. NF2 mutations were found in 6 tumors, all of which were intramedullary spinal and all of which displayed LOH 22q. Allelic loss on 22q was found in 20 cases and was significantly more frequent in intramedullary spinal ependymomas than in tumors in other locations. LOH 11q was found in 7 patients and exhibited a highly significant inverse association with LOH 22q (p<0.001). A hemizygous MEN1 mutation was identified in 3 tumors, all of which were recurrences from the same patient. Interestingly, the initial tumor corresponded to WHO grade II and displayed LOH 11q but not yet a MEN1 mutation. In 2 subsequent recurrences, the tumor had progressed to anaplastic ependymoma (WHO grade III) and exhibited a nonsense mutation in exon 10 of MEN1 (W471X) in conjunction with LOH 11q. This suggests that loss of wild-type MEN1 may be involved in the malignant progression of a subset of ependymomas. To conclude, our findings provide evidence for different genetic pathways involved in ependymoma formation and progression, which may allow to define genetically and clinically distinct tumor entities.

Ultrasound-guided surgery of deep seated brain lesions

OBJECTIVE

Computer aided navigation systems have been introduced to optimize the neurosurgical strategies minimizing the damage to the healthy brain tissue. As the loss of cerebrospinal fluid and surgical manipulation alter the position of the lesion in the external reference system, there is a risk of being misguided to deep seated brain tumors. In this context we present our experiences with intraoperative ultrasound which represents a real-time navigation system.

PATIENTS AND METHODS

45 patients with subcortical intracerebral lesions were operated on with the support of ultrasound imaging. Tumor depth from the surface measured 5 (superficial) to 68 mm. The minimum size of a cavernoma was 8 mm. Histopathological diagnoses included 17 cavernomas, 12 metastases and 16 gliomas. Ultrasound localization was achieved by two perpendicular projections and the surgical trajectory of the lesion secured by catheter placement.

RESULTS

Intraoperative ultrasound allowed an easy identification of all brain lesions. Additionally, a reliable localization of the tumor margins, including gliomas and metastases, was reached in 23 of 28 (82%) cases. The remaining 17 cavernomas were located all by intraoperative ultrasound, even the deep seated brain lesions of less than 10 mm in diameter could be easily detected. The real-time mode enabled a control of the surgical procedure. Technical problems arose from irregular and vaulted cortex surface, head positioning and surgical manipulation causing air artefacts with distal reduction of the signal intensity.

CONCLUSION

Intraoperative ultrasound is a reliable intraoperative guidance tool in the localization of deep seated brain tumors because it operates in real-time, thus increasing the safety of the surgical procedure and of the tumor resection.

Growth factors in gliomas revisited

Overexpression or untimely expression of wild-type or mutated protein growth factors and their receptors is associated with the biology of malignant gliomas and other types of cancer. It may result in unchecked tumour cell proliferation, migration/invasion into normal tissue, tumour angiogenesis, escape from immune surveillance, and decreased apoptotic cell death, i.e. after treatment with cytotoxic agents. This often involves activation of growth factor receptors either by simultaneous production of growth factors and corresponding receptors on the same or adjacent tumour cells or by constitutive receptor activation due to mutations. In several instances, the cellular genes encoding these growth factors and receptors are homologous to transforming genes/oncogenes from tumourigenic retroviruses and have thus been regarded as cellular proto-oncogenes. In recent years much progress has been made towards a better understanding of the function of these molecules and how they lead to the aggressive phenotype of malignant gliomas and its inherent resistance to adjuvant therapies. This, still insufficient, knowledge is a prerequisite for the development of novel therapies for this non-curable disease. The aim of this review is to address relevant growth factor receptor systems with emphasis on their particular role in glioma biology.

Anti-VEGF antibody treatment of glioblastoma prolongs survival but results in increased vascular cooption

Vascular endothelial growth factor (VEGF) is an important mediator of the intense angiogenesis which is characteristic of glioblastoma. While genetic manipulation of VEGF/VEGF receptor expression has previously been shown to inhibit glioblastoma growth, to date, no study has examined the efficacy of pharmacologic blockade of VEGF activity as a means to inhibit intracranial growth of human glioblastoma. Using intraperitoneal administration of a neutralizing anti-VEGF antibody, we demonstrate that inhibition of VEGF significantly prolongs survival in athymic rats inoculated in the basal ganglia with G55 human glioblastoma cells. Systemic anti-VEGF inhibition causes decreased tumor vascularity as well as a marked increase in tumor cell apoptosis in intracranial tumors. Although intracranial glioblastoma tumors grow more slowly as a consequence of anti-VEGF treatment, the histologic pattern of growth suggests that these tumors adapt to inhibition of angiogenesis by increased infiltration and cooption of the host vasculature.

Allelic losses in neurofibromatosis 2-associated meningiomas

More than 50% of patients with neurofibromatosis 2 (NF2) develop meningiomas. Recently, a higher proliferative activity, more mitotic figures, and greater nuclear pleomorphism have been described for NF2-associated meningiomas compared with sporadic ones. To analyze whether such histological differences could reflect underlying genetic differences, we examined 30 meningiomas from 22 NF2 patients for allelic losses on those chromosome arms that are frequently affected by deletions in sporadic meningiomas. In addition, we assessed the proliferative activity of the tumors and studied NF2 germline mutations. Twenty-three meningiomas corresponded to WHO grade I (10 fibrous, 6 psammomatous, 4 transitional, 3 meningothelial) and 7 to WHO grade II. The average MIB-1 index was 1.60 +/- 0.85 (WHO grade I: 1.41 +/- 0.80, WHO grade II: 2.13 +/- 0.82). When compared with several published studies of sporadic meningiomas, the MIB-1 index in NF2-associated meningiomas was not higher. Loss of heterozygosity (LOH) flanking or within the NF2 locus at 22q12 was detected in 100% of the tumors. LOH on 1p was the second most frequent abnormality (40%), followed by losses on 10q (27%), 6q and 14q (24%), 18q (23%), and 9p (17%). LOH on 19q and 17p, which is not commonly seen in sporadic meningiomas, was also only rarely detected in NF2-associated meningiomas. NF2 gene mutations were detected in 8 of 15 patients analyzed and were located in exons 2, 5, 6, 7, and 8. We conclude that sporadic and NF2-associated meningiomas share a common spectrum and frequency of allelic deletions as well as, in contrast to previous observations, a similar proliferative activity.

Clinical significance of pedicle aneurysms on feeding vessels, especially those located in infratentorial arteriovenous malformations

OBJECT

The diminishing threshold for the application of neuroimaging leads to an increasingly frequent diagnosis of previously asymptomatic arteriovenous malformations (AVMs). In such a context, it is warranted to define the criteria that make a lesion potentially hazardous so that neurosurgeons and patients reach a decision concerning how to manage the AVM. In addition to the proposed grading system for AVMs, which assesses the risk of an actual treatment procedure, several studies have been concerned with the evaluation of angioarchitectural features. The goal of the present study is to demonstrate the significance of feeding vessel pedicle aneurysms, especially those found in infratentorial AVMs.

METHODS

To determine the incidence of associated aneurysms, the authors reviewed an unselected cohort of 242 consecutive patients with AVMs managed between 1989 and 1999. Within this group were 240 patients who were treated by surgery, endovascular techniques, or a combination of both. Of these patients, 216 harbored a supratentorial and 24 an infratentorial AVM. Two additional patients with supratentorial AVMs underwent treatment of ruptured aneurysms without treatment of the AVMs. In six of the patients with supratentorial AVMs, proximal flow-related aneurysms were found on major feeding arteries, only one of which had caused hemorrhage. In only one patient were there additional distal feeding vessel pedicle aneurysms near the AVM, one of which had caused a major hemorrhage. In contrast, four of 24 patients with infratentorial AVMs had distal feeding artery pedicle aneurysms. Three of these aneurysms had caused hemorrhage.

CONCLUSIONS

Pedicle aneurysms on feeding vessels are frequently associated with hemorrhage (four of five cases in this series). In our cohort of 242 treated patients (240 treated for AVM and two for an aneurysm), feeding vessel pedicle aneurysms appear to occur more frequently in conjunction with infratentorial AVMs, which justifies aggressive management to prevent incidences of morbidity associated with rupture of the aneurysm.

Vascular endothelial growth factor, hepatocyte growth factor/scatter factor, basic fibroblast growth factor, and placenta growth factor in human meningiomas and their relation to angiogenesis and malignancy

OBJECTIVE

Angiogenesis is mediated by a number of different growth factors and appears vital for tumor growth. The understanding of angiogenic mechanisms could offer new therapeutic perspectives; in this context, the role of four potentially angiogenic growth factors was analyzed in a large series of meningiomas of different grades.

METHODS

Vascular endothelial growth factor (VEGF), placenta growth factor, hepatocyte growth factor/scatter factor, and basic fibroblast growth factor were quantified in 69 tumors by enzyme-linked immunosorbent assay. Microvessel density and proliferative activity were determined on paraffin sections, and clinical tumor invasiveness was rated. Induction of endothelial chemotaxis and capillary-like tube formation were studied in vitro using modified Boyden chamber assays and three-dimensional collagen gel assays, respectively.

RESULTS

Tumors included 40 benign (World Health Organization [WHO] Grade I), 21 atypical (WHO Grade II), and 8 anaplastic/malignant (WHO Grade III) meningiomas. We found a correlation between meningioma grade and VEGF content (r = 0.37, P = 0.002), which was 2-fold higher in atypical than in benign meningiomas (P = 0.022) and 10-fold higher in malignant than in benign meningiomas (P = 0.025). Among different subtypes of Grade I meningiomas, VEGF levels were 10-fold higher in meningothelial than in fibrous meningiomas (P = 0.015). None of the other three factors investigated showed any association with tumor grade, microvessel density, or invasiveness, and VEGF also did not correlate with vascularity or invasiveness. Moreover, vascularity did not increase with malignancy grade. Endothelial chemotaxis and capillary-like tube formation in vitro were induced by meningioma extracts and were most effectively blocked by co-addition of antibodies against basic fibroblast growth factor, followed by anti-VEGF, whereas anti-hepatocyte growth factor/scatter factor was not effective. The chemotactic activity of meningioma extracts on endothelial cells correlated with their VEGF content (r = 0.6, P = 0.003).

CONCLUSION

Meningiomas do not show an angiogenic switch involving VEGF and/or hepatocyte growth factor/scatter factor, as has previously been found in gliomas. Nevertheless, the biological activity of VEGF and basic fibroblast growth factor in meningiomas suggests that both are potential targets for antiangiogenic therapy in meningiomas of all WHO grades.

Retention of imprinting of the human apoptosis-related gene TSSC3 in human brain tumors

Genomic imprinting is the result of a gamete-specific modification leading to parental origin-specific gene expression in somatic cells of the offspring. Several embryonal tumors show loss of imprinting of genes clustered in human chromosome 11p15.5, an important tumor suppressor gene region, harboring several normally imprinted genes. TSSC3, a gene homologous to mouse TDAG51, implicated in Fas-mediated apoptosis, is also located in this region between hNAP2 and p57 (KIP2). TSSC3 is the first apoptosis-related gene found to be imprinted in placenta, liver and fetal tissues where it is expressed from the maternal allele in normal human development. This study investigated the imprinting status of TSSC3 in human normal, adult brain and in human neuroblastomas, medulloblastomas and glioblastomas. A polymorphism in exon 1 at position 54 was used to analyze the allelic expression of the TSSC3 gene by a primer oligo base extension (PROBE) assay using matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS). We found that the TSSC3 gene is not imprinted in human normal, adult brain and blood. In contrast, strong allelic bias resembling imprinting could be detected in most examined tumor specimens. The results demonstrate for the first time that the tumors under investigation are associated with a retention of imprinting of a potential growth inhibitory gene.

Genomic imprinting of IGF2 and H19 in human meningiomas

A number of genes, including IGF2 and H19, are normally imprinted with preferential expression of the paternal or maternal allele, respectively. Loss of imprinting (LOI) of IGF2 and H19 is found in a number of tumours, suggesting that LOI of IGF2 and/or H19 may play an important role in tumorigenesis. The IGF2 gene codes for a fetal growth factor and the H19 gene is likely to act as an RNA with an antitumour effect. We investigated the imprinting status of IGF2 and H19 in human meningiomas. The normally imprinted IGF2 gene lacks imprint in the leptomeninges and choroid plexus of the brain. To examine the imprinting status of IGF2 and H19 in human meningiomas we used the ApaI polymorphism in exon 9 for the IGF2 gene and the AluI polymorphism in exon 5 for the H19 gene. In total, 24 meningiomas of WHO grade I, II and III were analysed. 15 meningiomas (63%) were informative for the ApaI polymorphism in the IGF2 gene. Monoallelic expression (MAE) for IGF2 was found in 11 out of 15 tumours (73%) which is in contrast to the lack of imprinting status of IGF2 in leptomeninges. Ten cases (42%) were heterozygous for the H19 gene and biallelic expression was found in 3 out of 10 meningiomas (30%). These results indicate that modulation of the imprinting status of IGF2 and H19 may play an important role for the development of meningiomas.

Some hypothalamic hamartomas contain transforming growth factor alpha, a puberty-inducing growth factor, but not luteinizing hormone-releasing hormone neurons

Activation of LH-releasing hormone (LHRH) secretion, essential for the initiation of puberty, is brought about by the interaction of neurotransmitters and astroglia-derived substances. One of these substances, transforming growth factor alpha (TGFalpha), has been implicated as a facilitatory component of the glia-to-neuron signaling process controlling the onset of female puberty in rodents and nonhuman primates. Hypothalamic hamartomas (HH) are tumors frequently associated with precocious puberty in humans. The detection of LHRH-containing neurons in some hamartomas has led to the concept that hamartomas advance puberty because they contain an ectopic LHRH pulse generator. Examination of two HH associated with female sexual precocity revealed that neither tumor had LHRH neurons, but both contained astroglial cells expressing TGFalpha and its receptor. Thus, some HH may induce precocious puberty, not by secreting LHRH, but via the production of trophic factors--such as TGFalpha--able to activate the normal LHRH neuronal network in the patient's hypothalamus.

The contractile vacuole network of Dictyostelium as a distinct organelle: its dynamics visualized by a GFP marker protein

The contractile vacuole system is an osmoregulatory organelle composed of cisternae and interconnecting ducts. Large cisternae act as bladders that periodically fuse with the plasma membrane, forming pores to expel water. To visualize the entire network in vivo and to identify constituents of the vacuolar complex in cell fractions, we introduced a specific marker into Dictyostelium cells, GFP-tagged dajumin. The C-terminal, GFP-tagged region of this transmembrane protein is responsible for sorting to the contractile vacuole complex. Dajumin-GFP negligibly associates with the plasma membrane, indicating its retention during discharge of the bladder. Fluorescent labeled cell-surface constituents are efficiently internalized by endocytosis, while no significant cycling through the contractile vacuole is observed. Endosomes loaded with yeast particles or a fluid-phase marker indicate sharp separation of the endocytic pathway from the contractile vacuole compartment. Even after dispersion of the contractile vacuole system during mitosis, dajumin-GFP distinguishes the vesicles from endosomes, and visualizes post-mitotic re-organization of the network around the nucleus. Highly discriminative sorting and membrane fusion mechanisms are proposed to account for the sharp separation of the contractile vacuole and endosomal compartments. Evidence for a similar compartment in other eukaryotic cells is discussed.

The rate of homozygous CDKN2A/p16 deletions in glioma cell lines and in primary tumors

The rate of homozygous deletions of CDKN2A/p16 is variable between different tumor entities, and in addition it is higher in established cell lines in comparison with primary tumors. Such incongruencies may reflect statistical sampling errors, true differences depending on tissue derivatisation and CDKN2A/p16 loss under selective pressure in tissue culture. Clarification of these issues is warranted in the context of defining tumor suppressor genes such as CDKN2A/p16 as targets for gene replacement therapies. We therefore compared established cell lines derived from human glioblastomas and their corresponding primary tumors by multiplex PCR methodology. Archival early passages were included to determine the time point at which the p16 status of a cell line changes if it is different from the original tumor. It was found that in 2 of 11 cases (18%) the primary tumor had no p16 alteration whereas the corresponding cell lines had a homozygous p16 deletion. Tracking the in vitro evolution of these two cell lines we found that CDKN2A/p16 was lost already in the earliest passages. This suggests a clonal outgrowth advantage of a subpopulation of p16 deleted tumor cells rather than instability of the CDKN2A/p16 genotype in vitro. Including 20 additional glioblastoma-derived cell lines we detected that in 19 of the total 31 lines at least one exon was lost bringing the rate of p16 loss in the whole panel to 61%. This compares to a rate of 49% which was found in original glioma tissue from 47 unselected other patients. It is concluded, that in cell culture selective pressure favours the outgrowth of pre-existing CDKN2A/p16 negative clones, which account for the difference of CDKN2A/p16 status between cell lines and tumors. In no case did we see a change of the CDKN2A/p16 status during prolonged tissue culture periods of up to 8 years.

Preoperative embolization of intracranial meningiomas with a fibrin glue preparation

BACKGROUND AND PURPOSE

Preoperative embolization expands the spectrum of meningioma that can be operated on safely. Our goal was to achieve the distalmost loading of the vascular bed and confluent tumor necrosis with a fibrin glue preparation in the preoperative embolization of meningiomas.

METHODS

Between 1992 and 1997, 80 patients with a meningioma had diagnostic angiography with a standard transfemoral Seldinger technique, performed with a 6F guiding catheter and digital subtraction angiography. Preoperative embolization was carried out in the same session with an additional microcatheter system. Fibrin glue was the only component used. In all cases, CT was performed immediately after embolization; in nine patients, MR imaging was also performed.

RESULTS

Angiography verified the elimination of tumor blush in all patients. The high-density areas seen on postembolization CT scans, caused by the fibrin glue dispersed in the embolized supply area, were found to be necrotic at surgery and were easily removed by suction. Two (2.5%) of the 80 patients had complications associated with embolization that resulted in neurologic deficits.

CONCLUSION

The most effective preoperative embolization of tumors requires a distalmost loading of the vascular bed. Fibrin glue, which is easy to use and safe to handle, causes confluent tumor necrosis within the injected vascular territory.

Management of spinal dural arteriovenous fistulae using an interdisciplinary neuroradiological/neurosurgical approach: experience with 47 cases

OBJECTIVE

Spinal dural arteriovenous fistulae (SDAVFs) are frequently diagnosed after unacceptable delays and are therefore treated at a disadvantageously advanced stage. There is controversy regarding their treatment and the respective roles of interventional neuroradiologists and neurosurgeons. We present our series of 47 patients to illustrate the necessity for early treatment and the value of an interdisciplinary approach.

METHODS

All patients exhibited suspicious magnetic resonance imaging and/or myelographic findings. Subsequent spinal angiography revealed the SDAVFs. Twelve patients were treated primarily by surgical interruption of the arterialized intradural draining vein, and eight patients underwent surgery after unsuccessful embolization. Twelve patients were surgically treated several months after embolization because of the recruitment of collateral vessels. Definitive embolization was achieved for 15 patients. All patients were monitored with magnetic resonance imaging and at least one control angiographic examination. Follow-up periods ranged from 2 months to 8 years.

RESULTS

There was an obvious male prevalence, with 35 male and 12 female patients. Only six of the patients were less than 50 years of age. The SDAVFs were found twice as often on the left side, compared with the right. A total of 85% of the SDAVFs were located between T2 and L2. Presenting signs were most often progressive paraparesis, with 66% of the patients exhibiting progression to a condition in which they could not walk without support or were confined to a wheelchair. For 50% of the patients, the time at which the correct diagnosis was established was more than 15 months after the onset of the first symptoms. After treatment, 18 patients showed improvement (38%), the conditions of 26 patients (55%) were unchanged (without further deterioration), and the conditions of three patients (6%) had deteriorated.

CONCLUSION

Attempts at embolization should be made at the time of angiography, because no adverse effects were recorded in our series and there was a 30% chance of the patients being cured by that modality alone. Even if recanalization occurs, the internal labeling of a feeding vessel with radio-opaque embolization material allows exact intraoperative fluorographic localization of the origin of the draining vein, facilitating minimally invasive surgical exposure.

Dissecting glioma invasion: interrelation of adhesion, migration and intercellular contacts determine the invasive phenotype

The invasive cellular behavior of malignant gliomas is determined by receptor mediated cell-substratum contacts and cell-cell interaction as well as cellular locomotion. This study attempts to break down the complex phenomena of the invasive process into their components of attachment to neighboring cells, aggregate formation, adhesion to matrix substratum, migration and invasion into three-dimensional cellular aggregates separately analyzed in different in vitro assay systems. Using a panel of 13 glioma cell lines, adhesion to non-specifically or merosin coated surfaces was correlated to monolayer cell migration and dissemination of tumor cells from aggregates plated on these substrates. The formation kinetics of aggregates were determined and compared to the ability of these cells to rapidly attach and form mechanically stable cell-cell contacts. The motility rates in the different assay systems as well as cell-cell attachment was correlated to invasion of re-aggregated tumor cells into fetal rat brain. A tight positive correlation was found for substrate adhesion and monolayer migration. In contrast, cell-substratum contacts had little influence on dissemination of cells out of three-dimensional aggregates and no association between monolayer migration and migration of cells out of aggregates was detected. The ability of glioma cells to rapidly form aggregates was associated with enhanced migration out of aggregates. The capacity to invade fetal rat brain aggregates was correlated with the capacity to form stable intercellular adhesion as measured in a cell-cell adhesion assay. Invasion in this system was not found to be associated with migration in monolayer or with migration out of tumor aggregates. This study highlights that current in vitro assays for invasion only represent isolated aspects of the multi-cascade process which is involved in tumor cell invasion.

Two-step presurgical endovascular treatment of five arteriovenous malformations partially fed by single vessels en passage

PURPOSE

To describe a method for the preoperative embolization of arteriovenous malformations (AVM) containing vessels en passage (VeP). First, before embolization of the primary AVM, the distal portion of the VeP beyond the AVM, which supplies the parenchymal compartment, is blocked through placement of an endovascular ligature (fibered coils). This protects the post lesional parenchymal tissue and isolates malformational compartments before embolization. Thus the proximal AVM-supplying segment of the VeP can be safely embolized.

PATIENTS AND METHODS

Five of 204 AVM patients admitted for preoperative embolization between 1989 and 1997 fulfilled the following treatment criteria for the placement of an endovascular ligature in a VeP before embolization: 1. The diameter of the distal portion of the VeP behind the AVM was large whereas the parenchymal blush was poor; 2. The VeP fed a large portion of the AVM; 3. The VeP was judged to be accessible only late in the surgical procedure; 4. The VeP and its off branches were an integral part of the AVM periphery and thus not suitable for microdissection.

RESULTS

In all five cases the leptomeningeal collateral perfusion (the arterial supply to parenchymal brain areas) served to supply brain areas distal to the AVM after primary blockage of a VeP by endovascular ligature with fibered coils. Embolization and complete surgical dissection of the AVM was then achieved in all cases. No neurological deficits occurred.

CONCLUSION

Experience with our five cases indicates that a preparatory endovascular ligature of a VeP between parenchyma and the malformational compartment followed by embolization of the AVM can serve as an alternative to open surgical dissection of a vessel en passage and that it safely allows effective preoperative embolization.

Scatter factor/hepatocyte growth factor (SF/HGF) content and function in human gliomas

Scatter factor/hepatocyte growth factor (SF/HGF) is a pleiotrophic cytokine that stimulates motility and invasion of several cancer cell types and induces angiogenesis. Its receptor MET is a transmembrane tyrosine kinase encoded by the C-MET proto-oncogene. To assess the potential relevance of SF/HGF in gliomas we performed functional studies in vivo and in vitro, expression analyses and correlative studies. We showed that both SF/HGF and MET are expressed in gliomas in vivo and are upregulated during transition from low grade to malignant glioma. When SF/HGF cDNA was transfected into glioma cells that expressed the MET receptor the cells formed considerably larger and more vascularized intracranial tumors in vivo than SF/HGF negative control clones. In other glioma cells, which constitutively expressed both SF/HGF and MET, we abolished SF/HGF expression by antisense ribozyme-targeting, which led to a significant decrease in tumorigenicity and tumor growth. In vitro SF/HGF strongly stimulated glioma cell motility and to a lesser degree proliferation. SF/HGF also strongly increased endothelial cell motility in vitro and extracts of tumors derived from SF/HGF-transfected glioma cells were more mitogenic for endothelial cells and more angiogenic in the rat cornea angiogenesis assay than extracts from control tumors. In a three-dimensional in vitro angiogenesis assay basic fibroblast growth factor (bFGF) was found to synergize with either SF/HGF or vascular endothelial growth factor (VEGF) in inducing endothelial capillary-like tubes, whereas neither SF/HGF nor VEGF alone or in combination were effective. Interestingly, while both VEGF and SF/HGF levels appeared to be increased in malignant gliomas compared with low grade ones, this was not the case for bFGF of which biologically relevant levels were already present in low grade gliomas. It thus seems that bFGF alone is insufficient to induce angiogenesis in gliomas but may act synergistically with either VEGF and/or SF/HGF when these become upregulated during malignant progression. In conclusion, we showed that SF/HGF may contribute to glioma progression by stimulating tumor invasiveness, proliferation and neovascularization.

Allelic losses at 1p, 9q, 10q, 14q, and 22q in the progression of aggressive meningiomas and undifferentiated meningeal sarcomas

Meningiomas are usually benign tumors; however, they can recur after surgical resection and occasionally show histological progression to a higher malignancy grade. Five such rare cases of aggressively recurring meningiomas were present in our departmental cohort of 923 primary meningeal neoplasms operated over a 17-year period. Four other aggressively recurring meningeal tumors with a very similar clinical and histomorphological appearance (three undifferentiated meningeal sarcomas, one hemangiopericytoma) was also included in this study. We investigated whether disease progression can be traced by genetic alterations and whether a pattern of genetic alterations is specific for meningiomas. A total of 40 specimens from primary tumors and multiple recurrences of the nine patients were analyzed with 26 polymorphic allelic markers for deletions on 1p, 1q, 9q, 10q, 14q, and 22q. Loss of heterozygosity (LOH) at 22q was observed in all meningiomas cases at the earliest time point analyzed. Allelic loss at 1p was seen in the original tumor in two cases and upon meningioma recurrence in two others. Deletion on 10q occurred during tumor progression in two cases, and on 9q and 14q in one case. While allelic loss at 22q appears to be an early event in aggressive meningioma disease, there is a clear correlation of further deletions on chromosome arms 1p, 9q, 10q, and 14q with histopathological and clinical progression, as shown in these intraindividual trackings. None of these genetic findings were present in the non-meningiomatous meningeal tumors, indicating that meningothelial cells have their own lineage-specific genetic pathways towards clinical malignancy.

Levels of vascular endothelial growth factor, hepatocyte growth factor/scatter factor and basic fibroblast growth factor in human gliomas and their relation to angiogenesis

Angiogenesis is a possible target in the treatment of human gliomas. To evaluate the role of 3 growth factors, vascular endothelial growth factor (VEGF), hepatocyte growth factor/scatter factor (HGF/SF) and basic fibroblast growth factor (bFGF), in the angiogenic cascade, we determined their levels in extracts of 71 gliomas by enzyme-linked immunosorbent assay (ELISA). The levels of bFGF were only marginally different between gliomas of World Health Organization (WHO) grade II (low grade) and grades III and IV (high grade). In contrast, the mean concentrations of VEGF were 11-fold higher in high-grade tumors and those of HGF/SF 7-fold, respectively. Both were highly significantly correlated with microvessel density (p < 0.001) as determined by immunostaining for factor VIII-related antigen. In addition, VEGF and HGF/SF appeared to be independent predictive parameters for glioma microvessel density as determined by multiple regression analysis. We measured the capacity of all 3 factors to induce endothelial tube formation in a collagen gel. In this assay, bFGF was found to be an essential cofactor with which VEGF as well as HGF/SF were able to synergize independently. According to the concentrations of angiogenic factors, extracts from high-grade tumors were significantly more potent in the tube formation assay than the low-grade extracts (p = 0.02). Adding neutralizing antibodies to bFGF, VEGF and HGF/SF together with the extracts, tube formation was inhibited by up to 98%, 62% and 54%, respectively. Our findings suggest that bFGF is an essential cofactor for angiogenesis in gliomas, but in itself is insufficient as it is present already in the sparsely vascularized low-grade tumors. Upon induction of angiogenesis in high-grade tumors, bFGF may synergize with rising levels of not only VEGF but possibly also with HGF/SF, which appears here to be an independent angiogenic factor.

Preoperative functional magnetic resonance imaging (fMRI) of the motor system in patients with tumours in the parietal lobe

Intracranial lesions may compromise structures critical for motor performance, and mapping of the cortex, especially of the motor hand area, is important to reduce postoperative morbidity. We investigated nine patients with parietal lobe tumours and used functional MRI sensitized to changes in blood oxygenation to define the different motor areas, especially the primary sensorimotor cortex, in relation to the localization of the tumour. Activation was determined by pixel-by-pixel correlation of the signal intensity time course with a reference waveform equivalent to the stimulus protocol. All subjects showed significant activation of the primary sensorimotor cortex while performing a finger opposition task with the affected and unaffected side. In five patients the finger opposition task additionally activated the ipsilateral sensorimotor cortex and the supplementary motor area (SMA). Extension and flexion of the foot, additionally performed in two patients, also activated the sensorimotor cortex, in one case within the perifocal oedema of the tumour. Tumour localization near the central sulcus induced displacement of the sensorimotor cortex as compared to the unaffected side in all patients with a relevant mass effect. The results of our study demonstrate that functional MRI at 1.5 T with a clinically used tomograph can reproducibly localize critical brain regions in patients with intracranial lesions.