Clinical neurosciences in the decade of the brain: hypotheses in neuro-oncology. VEG/PF acts upon the actin cytoskeleton and is inhibited by dexamethasone: relevance to tumor angiogenesis and vasogenic edema.

HYPOTHESIS: We have proposed that VEG/PF acts by transforming the cytoskeletal architecture of microvascular endothelial cells. BACKGROUND: Evidence supporting a pivotal role for vascular endothelial growth/permeability factor (VEG/PF) in tumor angiogenesis and edemagenesis is compelling. VEG/PF exhibits specific endothelial cell mitogenicity and is expressed by brain tumors exhibiting increased vascularity and microvascular extravasation. The mechanistic cascade that follows VEG/PF-tyrosine kinase receptor binding remains uncertain, however. Actin is a cytoskeletal protein that regulates cellular motility, shape and vesicular transport. Regulation of actin stress fibers, cell-surface focal adhesions and plasmalemmal "ruffles" is mediated by tyrosine kinase activation of GTP-binding proteins that are in turn linked to intracellular calcium flux. As VEG/PF is known to induce cytosolic calcium ion transients in endothelial cells, actin microfilaments would appear to be logical candidates for study of a cytocontractile response mediated by calcium signal transduction. METHODS: VEG/PF-induced endothelial actin cytoskeletal changes were studied using rhodamine phalloidin staining and fluorescence photomicrography. RESULTS: When exposed to VEG/PF, cultured endothelial cells from human umbilical veins and rat brain microvessels exhibited a reversible, dose-related reorganization of actin stress fibers, cell contraction and rounding, and widening of the intercellular spaces. VEG/PF perturbation also induced plasmalemmal "ruffling". All VEG/PF-induced cytoskeletal changes were inhibited by preincubating endothelial cells with dexamethasone or anti-VEG/PF IgG antibody. CONCLUSION: The findings support a role for VEG/PF-induced cytoskeletal alterations in the pathophysiology of brain tumor angiogenesis and edemagenesis. These observations are likely to be directly linked to VEG/PF-induced endothelial cytosolic calcium flux. Insight into the mechanism of dexamethasone's clinical efficacy is also provided.

Expression of angiogenic factors and structural proteins in central nervous system vascular malformations.

Little is known of the molecular mechanisms mediating the genesis and subsequent biological behavior of central nervous system vascular malformations. The role of angiogenic and permeability-inducing factors in the pathogenesis of these lesions has not bee previously explored. In this study, we subject specimens from 12 cases of excised vascular malformation to a battery of immunostaining for vascular endothelial growth factor, basic fibroblast growth factor, and selected structural and matrix proteins. The lesions consisted of seven arteriovenous malformations (AVMs), including one angiographically occult AVM, one arterialized vein from a dural AVM, and five cavernous malformations (CMs). Vascular endothelial growth factor was expressed by all lesions and was localized predominantly in the subendothelial layer and in perivascular spaces. Four of seven AVMs and four of five CMs demonstrated faint basic fibroblast growth factor expression that was localized to the media of AVM vessels and the subendothelial layer and intercavernous matrix of CMs. This pattern of angiogenic factor immunostaining was correlated with the expression of structural and matrix proteins in the same lesions. Laminin was not expressed in any of the CMs, confirming previous reports from our laboratory. By contrast, fibronectin expression was more prominent in CMs than in AVMs. Collagen Type IV and alpha smooth muscle actin expression occurred in every lesion. We conclude that angiogenic growth factors are expressed in all types of vascular malformations of the central nervous system. The pattern of expression suggests diffuse activation of angiogenesis without specific relation to individual vessel types or recent clinical behavior. Defining the role of angiogenesis in vascular malformations might provide insight into their pathogenesis and suggest novel strategies for modification of their behavior.

Vascular endothelial growth/permeability factor expression in human glioma specimens: correlation with vasogenic brain edema and tumor-associated cysts.

Peritumoral vasogenic brain edema (PVBE) is a common accompaniment of malignant gliomas. It results from microvascular extravasation of plasma fluid and proteins through the interendothelial spaces. Tumor-associated cysts (TACs) are observed more commonly with benign gliomas that are not associated with PVBE. This study investigates the hypothesis that these morphologically distinct epiphenomena of microvascular extravasation are linked by a common pathophysiological mechanism involving vascular endothelial growth/permeability factor (VEG/PF), which has been implicated in vascular leak phenomena including ascites, malignant effusions, and brain edema. Furthermore, VEG/PF has been isolated from cultured glioma cells, and both VEG/PF protein and messenger RNA transcripts are expressed in brain tumor tissue. To further elucidate the relationship of VEG/PF to PVBE and TACs, the authors examined 34 pathological specimens for VEG/PF expression. Nineteen primary low-grade tumors, 11 primary high-grade tumors, and four gliosis controls were immunostained with a polyclonal anti-VEG/PF immunoglobulin G antibody. Magnetic resonance imaging was used to quantitate PVBE and to determine the presence of TACs and tumor enhancement. The study revealed that eight VEG/PF-negative specimens exhibited no significant edema, whereas 26 VEG/PF-positive tumors exhibited either significant PVBE or TACs. Notably, eight of nine benign TACs that were not associated with PVBE immunostained positive for VEG/PF. These data indicate a high degree of correlation between VEG/PF expression by gliomas and the occurrence of PVBE or TACs, irrespective of tumor grade, thus supporting VEG/PF's pivotal role as the common pathophysiological link between these processes.

Vascular permeability factor in brain metastases: correlation with vasogenic brain edema and tumor angiogenesis.

Metastatic brain tumors are almost always associated with vasogenic brain edema, which in turn plays a pivotal role in the evolution of neurological morbidity associated with these lesions. Attention has recently focused on a group of proteinaceous vascular permeability factors (VPF's) that are capable of inducing angiogenesis and promoting increased capillary permeability. To test the hypothesis that metastatic brain tumors expressing VPF's are associated with peritumoral cerebral edema, a rabbit polyclonal immunoglobulin (Ig) G anti-VPF was used to immunostain pathological specimens of metastatic cerebral tumors obtained from 22 patients who underwent surgery at Yale-New Haven Hospital. Magnetic resonance (MR) imaging was used to correlate VPF staining in tumor tissue with the occurrence of peritumoral brain edema. A histological study of the microvasculature was then conducted by immunostaining the specimens for endothelial cell factor VIII surface antigen, using two gliosis specimens as controls. Results revealed 21 of 22 tumors stained positively for VPF's; the negative-VPF tumor was a melanoma that exhibited no peritumoral edema. Twenty of 22 tumors had MR imaging-evident vasogenic edema. The presence and intensity of VPF immunostaining of microvascular features were noted and compared. Factor VIII staining demonstrated tumor vascularity to be most abundant in VPF-rich regions of tumor. The authors therefore report a high correlation between the presence of VPF's and the occurrence of peritumoral brain edema associated with cerebral metastases.

Prevention of "temporal hollowing" after fronto-orbital advancement for craniosynostosis.

Depression of profile in the temporal region is commonly seen after orbital rim advancement procedures. A newly developed temporalis musculoosseous flap has been designed with the intent to prevent this postoperative occurrence.

Massive orbital teratoma in the newborn.

Teratomas are rare germ cell tumors that comprise approximately 1% of orbital tumors in childhood. Review of the world literature revealed only 51 well-documented patients with true congenital orbital teratomas. We present a newborn girl with a massive orbital teratoma that caused significant orbital enlargement with inferior and lateral displacement of the zygoma and a thinning of the orbital roof. The ipsilateral maxilla and palate were depressed inferiorly. No bony invasion was seen despite its massive size. A craniofacial approach was used to safely and completely extirpate this tumor. Histological sections demonstrated derivatives of all three germ cell layers. Recommendations for definitive treatment and a review of the literature are presented.

The genesis of peritumoral vasogenic brain edema and tumor cysts: a hypothetical role for tumor-derived vascular permeability factor.

Cerebral edema and fluid-filled cysts are common accompaniments of brain tumors. They contribute to the mass effect imposed by the primary tumor and are often responsible for a patient's signs and symptoms. Cerebral edema significantly increases the morbidity associated with tumor biopsy, excision, radiation therapy, and chemotherapy. Both edema and cyst formation are thought to result from a deficiency in the blood-brain barrier, with consequent extravasation of water, electrolytes, and plasma proteins from altered tumor microvessels. The resultant expansion of the cerebral interstitial space contributes to the elevated intracranial pressure observed with brain tumors. Departure from the typical blood-brain barrier microvascular architecture may only partially explain the occurrence of edema and tumor cyst formation. Biochemical mediators have also been implicated in vascular extravasation. Vascular permeability factor or vascular endothelial growth factor (VPF/VEGF) is a protein that has recently been isolated from a variety of tumors including human brain tumors. VPFb is an extraordinarily potent inducer of both microvascular extravasation (edemagenesis) and the formation of new blood vessels (angiogenesis). Its role in tumor growth and progression would therefore appear pivotal. Herein, the author presents an updated account of the investigation of VPF. Historical and clinical perspectives of the study and treatment of tumor associated edema are provided. The efficacy of high-dose dexamethasone in the treatment of neoplastic brain edema is discussed. A hypothetical role for VPF in edemagenesis is presented and discussed. It is hoped that an expanded understanding of the mechanisms responsible for the genesis of edema will ultimately facilitate therapeutic intervention.

Clivus chordoma: a report of 12 recent cases and review of the literature.

Twelve patients with histologically confirmed clivus chordoma were treated at the Johns Hopkins Hospital between 1971 and 1989. Eight of the patients were men and four were women. The mean age at first operation was 51 years (range, 10 to 80). The most common presenting symptoms were headache, diplopia, dysphagia and dysarthria, and facial sensory changes. Computed tomography, with and without contrast enhancement, proved adequate for tumor identification and localization. Magnetic resonance imaging and angiography were occasionally employed to localize the tumors further and to define tumor vascular supply and proximity to vascular structures. Twenty-two resections were performed in 11 patients, and another patient underwent biopsy only. Seven were also treated with radiation therapy. Tumors recurred in eight patients, six of whom underwent further operations. The mean time to first recurrence was 22 months (range 8 to 36 months). Six of the patients are still alive, with a mean follow-up of 31 months (range, 3 to 89 months) from first surgical resection. The mean survival time from first treatment was 31 months (range, 4 to 62 months) among those patients who died. There was no operative mortality. The 5-year cumulative survival rate was 20%. Six patients with long follow-up have had fair to good results, being free of recurrences for at least a year. However, none of the patients returned to their premorbid baseline of activities. Five of the patients had tumors with the histologic diagnosis of chondroid chordoma. Three of these patients are still alive. The mean age at first treatment was 44 (compared with 62 for typical chordomas). The mean time from symptoms to diagnosis was 29 months (typical chordomas, 18 months). The mean length of survival and time to tumor recurrence were not significantly different between chondroid and typical chordomas.

Cytosolic calcium changes in endothelial cells induced by a protein product of human gliomas containing vascular permeability factor activity.

A vascular permeability factor (VPF) derived from serum-free conditioned medium of cultured human malignant gliomas (HG-VPF) has been described previously. The rapid kinetics of HG-VPF activity in an in vivo assay of vascular permeability suggests a direct action upon the vascular endothelial cell. To determine whether HG-VPF was capable of inducing a physiologically significant alteration in isolated endothelial cells, cytosolic calcium [Ca++]i was measured in vitro in these cells before and after their exposure to media containing this substance. This was accomplished by preloading cultured endothelial cells with a fluorescent intracellular Ca++ probe fura-2/AM. It was found that HG-VPF induced a rapid and transient elevation of [Ca++]i in normal endothelial cells derived from human umbilical vein, bovine adrenal medulla, bovine pulmonary artery, and rat brain. This effect was inhibited by chelating extracellular calcium [Ca++]e with ethyleneglycol-bis (beta-aminoethylether)-N,N'-tetra-acetic acid (EGTA), indicating that the HG-VPF-induced response resulted from the influx of extracellular calcium. The addition of cations that act as nonspecific calcium channel blockers (Li+, Co++, Mn++, La ) completely inhibited VPF activity, further supporting the role of [Ca++]e influx. The HG-VPF activity was not, however, blocked by verapamil, a calcium antagonist that appears to be specific for voltage-gated calcium channels. Furthermore, exposure of endothelial cells to 120 mM [K+]e did not result in a calcium transient. Coincubation of endothelial cells with dexamethasone inhibited HG-VPF-induced rises in [Ca++]i, while having no effect upon cyclic nucleotide-induced changes in calcium. The present studies indicate that vascular extravasation induced by human glioma-derived VPF may be mediated by a direct action upon vascular endothelial cells. Furthermore, the observed dexamethasone-induced inhibition of this process suggests a specific cellular action for corticosteroids. This, together with previous observations that dexamethasone suppresses both the production of VPF by tumor cells in vitro and its permeability-inducing activity in vivo, may explain the efficacy of glucocorticoids in the treatment of neoplastic vasogenic brain edema. Finally, studies with a polycationic peptide (protamine) known to induce blood-brain barrier disruption in vivo revealed similar effects upon endothelial cytosolic calcium levels. As HG-VPF is a positively charged macromolecule, a common interaction between these substances and the negatively charged endothelial cell surface in the induction of permeability is suggested. Nonspecific cross-linking of charged groups of the endothelial glycocalyx and specific HG-VPF receptor binding are both valid mechanisms of HG-VPF-mediated calcium changes. Their potential relevance in the setting of microvascular permeability is discussed.

Reversible acute and subacute myelopathy in patients with dural arteriovenous fistulas. Foix-Alajouanine syndrome reconsidered.

Acute or subacute neurological deterioration without evidence of hemorrhage in a patient with a spinal arteriovenous (AV) malformation has been referred to as "Foix-Alajouanine syndrome." This clinical entity has been considered to be the result of progressive vascular thrombosis resulting in a necrotic myelopathy; it has therefore been thought to be largely irreversible and hence untreatable. The authors report five patients with dural AV fistulas who presented in this manner, and who improved substantially after embolic and surgical therapy. The outcome of these patients indicates that acute and subacute progression of myelopathy in cases of spinal dural AV fistulas may be caused by venous congestion and not necessarily by thrombosis. Therefore, a clinical diagnosis of Foix-Alajouanine syndrome is of little practical use, as spinal cord dysfunction from venous congestion is a potentially reversible process whereas thrombotic infarction is not. This diagnosis may result in suboptimal management. The recognition of nonhemorrhagic acute or subacute myelopathy as a complication of a spinal dural AV fistula is important since what appears to be irreversible cord injury is often treatable by standard surgical techniques.

Measurement of intracranial tissue volume using computed tomographic images and a personal computer.

A software package called MacMeasure was developed previously to measure the size of intracellular structures by means of photomicrographs. We have expanded the application of this program to computed tomographic (CT) images. Using three objects of irregular shape and unequal size (phantoms), we compared volumetric determinations made with a CT mainframe computer and a widely available personal computer. The phantom objects were scanned in a GE CT/T 9800 scanner with serial, nonoverlapping slices 3.0 mm in thickness. The image data were first measured directly from the magnetic archive tape with the CT control terminal. Hard copies of the CT scans were then measured with a Macintosh SE computer and a digitizing tablet with a crosshair cursor driven by the MacMeasure software package. A third method of measuring volume was by tracing individual CT images onto paper (hard copies). The tracings were then cut out, weighed, and converted to surface area by dividing the weights by a weight/surface area standard (26.37 mg = 25 cm2) calibrated to the CT image scale (5.0 cm). The total surface area value was then converted to volume by multiplying by a single CT slice thickness (0.3 cm). Finally, the phantom objects were placed in water-filled graduated cylinders to determine their volume by fluid displacement. The technique using MacMeasure and the personal computer provides an accurate means of determining surface area and volumes using hard copies of CT images. It avoids occupying costly CT computer time and is the most rapid method of volume measurement of the three techniques tested (CT mainframe = 6.0 hours, trace/weigh = 3.5 hours, and PC = 1.25 hours).(ABSTRACT TRUNCATED AT 250 WORDS)

Further characterization of malignant glioma-derived vascular permeability factor.

The nature of vascular permeability factor (VPF) activity derived from serum-free conditioned medium containing cultured human malignant glial tumors has been further investigated. A 1000-fold purification was accomplished by sequential heparin-Sepharose affinity chromatography and high-performance liquid chromatography gel filtration chromatography steps. Vascular permeability factor activity falls into a molecular weight range of 41,000 to 56,000 D. Activity is bound to hydroxylapatite, carboxymethyl-Sepharose, phenyl-Sepharose, and heparin-Sepharose, whereas little or no activity was bound to diethylaminoethyl-Sephacel. Vascular permeability factor activity is trypsin- and pepsin-sensitive but is unaffected by treatment with ribonuclease A. This suggests that VPF is a hydrophobic, positively charged (cationic) polypeptide with a potentially biologically significant affinity for heparin. As most proteins are negatively charged (anionic) and have no affinity for heparin, a significant advantage was gained by performing these purification steps. The activity of VPF is not inhibited by coinjection of conditioned medium with soybean trypsin inhibitor; or hexadimethrine (both known antagonists of tissue plasminogen activator, Hageman factor, and serum kallikrein); or aprotinin (an antagonist of both plasmin and tissue kallikrein); or phenylmethanesulfonyl fluoride (a serine esterase (elastase) inhibitor); or pepstatin-A (an acid protease inhibitor which inactivates vascular permeability-inducing leukokinins). These data, together with the fact that VPF is produced and released into serum-free media, provides substantial evidence against it being one of the more commonly known serum-derived permeability mediators. Treatment with dithiothreitol inhibited VPF activity, indicating the presence of at least one essential disulfide bond in this molecule. Inhibition by dexamethasone of VPF expression in cultured malignant glial cells appears to be selective. Dexamethasone-induced inhibition of VPF was dose-responsive and was not associated with a parallel inhibition of cellular protein synthesis as determined by tritiated leucine incorporation into trichloroacetic acid-precipitable material. Inclusion of dexamethasone in the culture medium was not associated with altered cell viability or cell number. A series of in vivo studies confirmed the inhibition of VPF activity in test animals pretreated with dexamethasone. This steroid-induced inhibition was partially reversed by treatment of test animals with actinomycin D prior to exposure to dexamethasone.(ABSTRACT TRUNCATED AT 400 WORDS)

Vascular permeability induced by protein product of malignant brain tumors: inhibition by dexamethasone.

Serum-free conditioned medium derived from confluent monolayer cultures of malignant human astroglial tumors contains a substance that rapidly increases capillary vascular permeability after intradermal injection into guinea pigs. Accumulation of vascular permeability factor (VPF) activity occurs with increasing duration of tumor incubation in vitro. Expression of this activity is inhibited by incubation of cell cultures with cycloheximide or dexamethasone. This VPF is an acid-stable heat-labile macromolecule that is inactivated by trypsin and pepsin and binds immobilized heparin. Activity is retained by ultrafiltration with 30,000-dalton cut-off microconcentrators. Pretreatment of test animals with systemic dexamethasone prior to intradermal injection of VPF diminishes microvascular permeability. Furthermore, VPF activity is not inhibited by antihistamines. Secretion of VPF may cause the vasogenic brain edema that is frequently associated with malignant primary and metastatic intracerebral tumors. Inhibition by dexamethasone of both VPF expression in tissue culture, and VPF activity at the microvascular level in test animals, is in keeping with the known efficacy of this agent in treating the vasogenic edema associated with brain tumors.

Intraventricular meningioma. A review of 10 cases of the National Hospital, Queen Square (1974-1985) with reference to the literature.

Ten patients with histologically verified intraventricular meningiomas were treated between 1974 and 1985. There were eight female and two male patients, ranging in age from 25 to 72 years with a mean age of 45.5 years. Headache and disturbed mentation were the most common presenting symptoms whereas corticospinal disturbance, altered mentation and homonymous hemianopia were the most common signs on formal neurological examination. Papilloedema was demonstrable in 50% of cases and evidence of dysphasia was apparent in 60% of patients with lesions affecting their dominant hemisphere. A single instance of drop attack occurred in a patient harbouring a third ventricular meningioma. Computed tomography, with and without contrast enhancement, and angiography were employed in all cases and proved highly sensitive and specific for tumour localisation and tissue diagnosis. In addition, angiography proved invaluable in demonstrating both vascular supply and the effects imposed upon the surrounding cerebral vasculature by tumour mass and hydrocephalus. Nine tumours occurred in the lateral ventricular trigone of which 5 were left-sided. A tenth tumour was located in the third ventricle. Twelve resections were performed in 10 patients. One patient was found to have a highly malignant cystic meningioma which recurred within 10 weeks of the original surgery and proved fatal shortly thereafter. A second patient whose initial resection was subtotal had a recurrence 3 years postoperatively which was totally resected. Lesions were approached most commonly through the posterior middle or posterior inferior temporal gyri. On 3 occasions a right posterior middle frontal gyrus approach was used and in one case a posterior parieto-occipital cortical incision was employed.(ABSTRACT TRUNCATED AT 250 WORDS)