Exercise induced muscle blood flow is decreased in Charcot-Marie-Tooth disease type 1 polyneuropathy: a power Doppler analysis.

BACKGROUND AND PURPOSE: Intramuscular blood flow increases during physical activity and may be quantified immediately following exercise using power Doppler sonography. Post-exercise intramuscular blood flow is reduced in patients with muscular dystrophy, associated with disease severity and degenerative changes. It is not known if intramuscular blood flow is reduced in patients with neuropathy, nor if it correlates with muscle strength and structural changes. The aim was to determine whether blood flow is reduced in patients with polyneuropathy due to Charcot-Marie-Tooth disease type 1 (CMT1) and to compare more affected distal to less affected proximal muscles. METHODS: This was a cross-sectional study including 21 healthy volunteers and 17 CMT patients. Power Doppler ultrasound was used to quantify post-exercise intramuscular blood flow in distal (gastrocnemius) and proximal (elbow flexor) muscles. Intramuscular blood flow was compared to muscle echo intensity, muscle strength, disease severity score, patient age and electromyography. RESULTS: Polyneuropathy patients showed reduced post-exercise blood flow in both gastrocnemius and elbow flexors compared to controls. A more prominent reduction was seen in the gastrocnemius (2.51% vs. 10.34%, p < 0.0001) than in elbow flexors (4.48% vs. 7.03%, p < 0.0001). Gastrocnemius intramuscular blood flow correlated with muscle strength, disease severity and age. Receiver operating characteristic analysis showed that quantification of intramuscular blood flow was superior to echo intensity for detecting impairment in the gastrocnemius (area under the curve 0.962 vs. 0.738, p = 0.0126). CONCLUSION: Post-exercise intramuscular blood flow is reduced in CMT1 polyneuropathy. This reduction is present in both impaired distal and minimally affected proximal muscles, indicating it as an early marker of muscle impairment due to neuropathy.

Increased brain plasmin levels following experimental ischemic stroke in male mice.

Many coagulation factor proteases are increased in the brain during ischemic stroke. One of these proteases is plasmin. In this study we established a novel method for direct quantitative measurement of plasmin activity in male mouse brain slices using a sensitive fluorescent substrate in the presence of specific protease inhibitors. In both the ischemic and contralateral hemispheres, plasmin activity increased 3, 6, and 24 hr following stroke in comparison to healthy mice (F(3, 72) = 39.5, p < 0.0001, repeated measures ANOVA) after the induction of permanent middle cerebral artery occlusion (PMCAo). Plasmin activity was higher in the ischemic hemisphere (F(1,36) = 9.1, p = 0.005) and there was a significant interaction between time and ischemic hemisphere (F(3,36) = 4.4, p = 0.009). Plasmin activity was correlated with infarct volume (R2  = 0.5289, p = 0.0009 by Spearman). The specificity of the assay was verified utilizing tissue-type plasminogen activator (tPA)-deficient mice which, as expected, had significantly lower levels of plasmin 24 hr following ischemia compared to wild-type mice (ischemic (0.6 ± 0.23 and 1.94 ± 0.5, respectively), p = 0.049 and contralateral hemispheres (0.13 ± 0.14 and 0.75 ± 0.10, respectively), p = 0.018 by t test). There is a time-dependent increase in plasmin levels and an association of higher levels of plasmin with larger infarct volumes in an experimental stroke model. This suggests caution in the use of recombinant tPA (rtPA) and that plasmin inhibition in the brain may be a therapeutic target in acute ischemic stroke.

Autoantibodies to Annexin A2 and cerebral thrombosis: Insights from a mouse model.

INTRODUCTION: Antiphospholipid syndrome (APS) is an autoimmune disorder manifested by thromboembolic events, recurrent spontaneous abortions and elevated titers of circulating antiphospholipid antibodies. In addition, the presence of antiphospholipid antibodies seems to confer a fivefold higher risk for stroke or transient ischemic attack. Although the major antigen of APS is ß2 glycoprotein I, it is now well established that antiphospholipid antibodies are heterogeneous and bind to various targets. Recently, antibodies to Annexin A2 (ANXA2) have been reported in APS. This is of special interest since data indicated ANXA2 as a key player in fibrinolysis. Therefore, in the present study we assessed whether anti-ANXA2 antibodies play a pathological role in thrombosis associated disease. MATERIALS AND METHODS: Mice were induced to produce anti-ANXA2 antibodies by immunization with ANXA2 (iANXA2) and control mice were immunized with adjuvant only. A middle cerebral artery occlusion stroke model was applied to the mice. The outcome of stroke severity was assessed and compared between the two groups. RESULTS: Our results indicate that antibodies to ANXA2 lead to a more severe stroke as demonstrated by a significant larger stroke infarct volume (iANXA2 133.9 ± 3.3 mm3 and control 113.7 ± 7.4 mm3; p = 0.017) and a more severe neurological outcome (iANXA2 2.2 ± 0.2, and control 1.5 ± 0.18; p = 0.03). CONCLUSIONS: This study supports the hypothesis that auto-antibodies to ANXA2 are an independent risk factor for cerebral thrombosis. Consequently, we propose screening for anti-ANXA2 antibodies should be more widely used and patients that exhibit the manifestations of APS should be closely monitored by physicians.

A Novel Highly Sensitive Method for Measuring Inflammatory Neural-Derived APC Activity in Glial Cell Lines, Mouse Brain and Human CSF.

BACKGROUND: Neural inflammation is linked to coagulation. Low levels of thrombin have a neuroprotective effect, mediated by activated protein C (APC). We describe a sensitive novel method for the measurement of APC activity at the low concentrations found in neural tissue. METHODS: APC activity was measured using a fluorogenic substrate, Pyr-Pro-Arg-AMC, cleaved preferentially by APC. Selectivity was assessed using specific inhibitors and activators. APC levels were measured in human plasma, in glia cell lines, in mice brain slices following mild traumatic brain injury (mTBI) and systemic lipopolysaccharide (LPS) injection, and in cerebrospinal fluid (CSF) taken from viral meningoencephalitis patients and controls. RESULTS: Selectivity required apixaban and alpha-naphthylsulphonylglycyl-4-amidinophenylalanine piperidine (NAPAP). APC levels were easily measurable in plasma and were significantly increased by Protac and CaCl2. APC activity was significantly higher in the microglial compared to astrocytic cell line and specifically lowered by LPS. Brain APC levels were higher in posterior regions and increased by mTBI and LPS. Highly elevated APC activity was measured in viral meningoencephalitis patients CSF. CONCLUSIONS: This method is selective and sensitive for the measurement of APC activity that significantly changes during inflammation in cell lines, animal models and human CSF.

Brain Protease Activated Receptor 1 Pathway: A Therapeutic Target in the Superoxide Dismutase 1 (SOD1) Mouse Model of Amyotrophic Lateral Sclerosis.

Glia cells are involved in upper motor neuron degeneration in amyotrophic lateral sclerosis (ALS). Protease activated receptor 1 (PAR1) pathway is related to brain pathologies. Brain PAR1 is located on peri-synaptic astrocytes, adjacent to pyramidal motor neurons, suggesting possible involvement in ALS. Brain thrombin activity in superoxide dismutase 1 (SOD1) mice was measured using a fluorometric assay, and PAR1 levels by western blot. PAR1 was localized using immunohistochemistry staining. Treatment targeted PAR1 pathway on three levels; thrombin inhibitor TLCK (N-Tosyl-Lys-chloromethylketone), PAR1 antagonist SCH-79797 and the Ras intracellular inhibitor FTS (S-trans-trans-farnesylthiosalicylic acid). Mice were weighed and assessed for motor function and survival. SOD1 brain thrombin activity was increased (p < 0.001) particularly in the posterior frontal lobe (p = 0.027) and hindbrain (p < 0.01). PAR1 levels were decreased (p < 0.001, brain, spinal cord, p < 0.05). PAR1 and glial fibrillary acidic protein (GFAP) staining decreased in the cerebellum and cortex. SOD1 mice lost weight (≥17 weeks, p = 0.047), and showed shorter rotarod time (≥14 weeks, p < 0.01). FTS 40mg/kg significantly improved rotarod scores (p < 0.001). Survival improved with all treatments (p < 0.01 for all treatments). PAR1 antagonism was the most efficient, with a median survival improvement of 10 days (p < 0.0001). Our results support PAR1 pathway involvement in ALS.

Thrombin Activity in Rodent and Human Skin: Modified by Inflammation and Correlates with Innervation.

Thrombin is present in peripheral nerves and is involved in the pathogenesis of neuropathy. We evaluated thrombin activity in skin punch biopsies taken from the paws of male mice and rats and from the legs of patients with suspected small-fiber neuropathy (SFN). In mice, inflammation was induced focally by subcutaneous adjuvant injection to one paw and systemically by intraperitoneal lipopolysaccharides (LPS) administration. One day following injection, thrombin activity increased in the skin of the injected compared with the contralateral and non-injected control paws (p = 0.0009). One week following injection, thrombin increased in both injected and contralateral paws compared with the controls (p = 0.026), coupled with increased heat-sensitivity (p = 0.009). Thrombin activity in the footpad skin was significantly increased one week after systemic administration of LPS compared with the controls (p = 0.023). This was not accompanied by increased heat sensitivity. In human skin, a correlation was found between nerve fiber density and thrombin activity. In addition, a lower thrombin activity was measured in patients with evidence of systemic inflammation compared with the controls (p = 0.0035). These results support the modification of skin thrombin activity by regional and systemic inflammation as well as a correlation with nerve fiber density. Skin thrombin activity measurments may aid in the diagnosis and treatment of SFN.

Early and late manifestations of neuropathy due to HSPB1 mutation in the Jewish Iranian population.

OBJECTIVE: Mutations in the HSPB1 gene are associated with a distal hereditary motor neuropathy type 2 (dHMN2) or Charcot-Marie-Tooth disease type 2F (CMT2F), usually with autosomal dominant inheritance. This study aimed to describe the phenotype of the HSPB1 c.407G>T (p.Arg136Leu) mutation at early and late stages of the disease course. METHODS: We identified this mutation (previously reported in patients from Italy) in a heterozygous state, among 14 individuals from eight families of Jewish Iranian descent. The clinical, electrophysiological and ultrasonographic features were evaluated during early (less than 5 years, N = 9) or late disease course (N = 5). RESULTS: The majority of subjects were males with a mean age at onset of 43.4 years (range 21-67). Common initial symptoms were gait imbalance, distal (often asymmetric) lower limb weakness and feet numbness. Neurological examination in early disease course showed distal lower extremity weakness in nearly all cases, and absent Achilles tendon reflex in about half. A minority had distal loss of pain, vibration or position sensation. These findings were more prevalent in late disease stage. Electrodiagnostic studies demonstrated a length-dependent axonal motor neuropathy, with typical preferential involvement of the tibial nerve. Muscle ultrasound showed a corresponding length-dependent increase of homogeneous echo-intensity, most noticeably in the gastrocnemius. One patient had a dual diagnosis of CMT2F and CMT2W. INTERPRETATION: The HSPB1 c.407G>G (p.Arg136Leu) mutation causes an adult-onset, predominantly motor, axonal neuropathy in individuals of Jewish Iranian descent. Variable manifestations are noticed, and sensory involvement is more prominent in prolonged disease duration.

Treatment of Diabetic Neuropathy with A Novel PAR1-Targeting Molecule.

Diabetic peripheral neuropathy (DPN) is a disabling common complication of diabetes mellitus (DM). Thrombin, a coagulation factor, is increased in DM and affects nerve function via its G-protein coupled protease activated receptor 1 (PAR1). METHODS: A novel PAR1 modulator (PARIN5) was designed based on the thrombin PAR1 recognition site. Coagulation, motor and sensory function and small fiber loss were evaluated by employing the murine streptozotocin diabetes model. RESULTS: PARIN5 showed a safe coagulation profile and showed no significant effect on weight or glucose levels. Diabetic mice spent shorter time on the rotarod (p <0.001), and had hypoalgesia (p <0.05), slow conduction velocity (p <0.0001) and reduced skin innervation (p <0.0001). Treatment with PARIN5 significantly improved rotarod performance (p <0.05), normalized hypoalgesia (p <0.05), attenuated slowing of nerve conduction velocity (p <0.05) and improved skin innervation (p <0.0001). CONCLUSION: PARIN5 is a novel pharmacological approach for prevention of DPN development, via PAR1 pathway modulation.

The Effect of Neuronal Activity on Glial Thrombin Generation.

Thrombin through its receptor PAR-1 plays an important role in the peripheral nervous system. PAR-1 is located at the microvilli of Schwann cells at the node of Ranvier, and thrombin is generated by the coagulation system on these glial structures. In the present study, we examined the link between neuronal activity and modulation of thrombin generation by glial Schwann cells. Thrombin activity was assessed in sciatic nerves in reaction to high KCl as a model of neuronal activity. We demonstrated a significant transient effect of high KCL on thrombin activity (F(5, 20) = 42.65, p < 0.0001, by ANOVA) compared to normal KCl levels. Since the sciatic nerve includes components of axons and Schwann cell myelin sheath, we continued to investigate the effect of high KCl on a Schwannoma cell line as a model for nodal Schwann cell microvilli. We demonstrated a transient decrease in thrombin activity in response to high extracellular KCl (F(1, 18) = 9.56, p = 0.0063). The major neuronal inhibitor of thrombin is PN-1, and we therefore measured the effect of high KCL on PN-1 immunofluorescence intensity. We found significantly higher PN-1 staining intensity 3 min after the application of high KCL in comparison to cells exposed to high KCL for 7 min and to cells in regular KCL (F(2, 102) = 8.4737, p < 0.0004), and this effect may explain the changes in thrombin activity. The present results support an interaction between neuronal activity and the coagulation pathway as a novel mechanism for neuron-glia crosstalk at the node of Ranvier.

Thrombin and the Protease-Activated Receptor-1 in Organophosphate-Induced Status Epilepticus.

Organophosphates (OP) are a major threat to the health of soldiers and civilians due to their use as chemical weapons in war and in terror attacks. Among the acute manifestations of OP poisoning, status epilepticus (SE) is bearing the highest potential for long-term damages. Current therapies do not prevent brain damage and seizure-related brain injuries in OP-exposed humans. Thrombin is a serine protease known to have a fundamental function in the clotting cascade. It is highly expressed in the brain where we have previously found that it regulates synaptic transmission and plasticity. In addition, we have found that an excess of thrombin in the brain leads to hyperexcitability and therefore seizures through a glutamate-dependent mechanism. In the current study, we carried out in vitro, ex vivo, and in vivo experiments in order to determine the role of thrombin and its receptor PAR-1 in paraoxon-induced SE. Elevated thrombin activity was found in the brain slices from mice that were treated (in vitro and in vivo) with paraoxon. Increased levels of PAR-1 and pERK proteins and decreased prothrombin mRNA were found in the brains of paraoxon-treated mice. Furthermore, ex vivo and in vivo electrophysiological experiments showed that exposure to paraoxon causes elevated electrical activity in CA1 and CA3 regions of the hippocampus. Moreover, a specific PAR-1 antagonist (SCH79797) reduced this activity. Altogether, these results reveal the importance of thrombin and PAR-1 in paraoxon poisoning. In addition, the results indicate that thrombin and PAR-1 may be a possible target for the treatment of paraoxon-induced status epilepticus.

Blocking Thrombin Significantly Ameliorates Experimental Autoimmune Neuritis.

Thrombin and its protease-activated receptor 1 (PAR1) are potentially important in peripheral nerve inflammatory diseases. We studied the role of thrombin and PAR1 in rat experimental autoimmune neuritis (EAN), a model of the human Guillain-Barré syndrome (GBS). EAN was induced by bovine peripheral myelin with complete Freund's adjuvant (CFA). Thrombin activity in the sciatic nerves, clinical scores and rotarod performance were measured. Thrombin activity in the sciatic nerve was elevated in EAN compared to CFA control rats (sham rats) (p ≤ 0.004). The effect of blocking the thrombin-PAR1 pathway was studied using the non-selective thrombin inhibitor N-Tosyl-Lys-chloromethylketone (TLCK), and the highly specific thrombin inhibitor N-alpha 2 naphtalenesulfonylglycyl 4 amidino-phenylalaninepiperidide (NAPAP). In-vitro TLCK and NAPAP significantly inhibited specific thrombin activity in EAN rats sciatics (p<0.0001 for both inhibitors). Treatment with TLCK 4.4 mg/kg and NAPAP 69.8 mg/kg significantly improved clinical and rotarod scores starting at day 12 and 13 post immunization (DPI12, DPI13) respectively (p < 0.0001) compared to the untreated EAN rats. In nerve conduction studies, distal amplitude was significantly lower in EAN compared to sham rats (0.76 ± 0.34 vs. 9.8 ± 1.2, mV, p < 0.0001). Nerve conduction velocity was impaired in EAN rats (23.6 ± 2.6 vs. sham 43 ± 4.5, m/s p = 0.01) and was normalized by TLCK (41.2 ± 7.6 m/s, p < 0.05). PAR1 histology of the sciatic node of Ranvier indicated significant structural damage in the EAN rats which was prevented by TLCK treatment. These results suggest the thrombin-PAR1 pathway as a possible target for future intervention in GBS.

Local Regulation of Thrombin Activity by Factor Xa in Peripheral Nerve Schwann Cells.

Thrombin through its receptor plays an important role in the peripheral nervous system (PNS) but the pathways leading to its generation there are not known. In the blood, activated factor X (FXa) which is formed from factor X (FX) by tissue factor (TF) and factor VII (FVII), cleaves prothrombin into thrombin. We here studied these factors in vivo in mouse sciatic nerve and in vitro in a Schwannoma cell line and provide mRNA, immunoblot and immunohistochemistry evidence that FX and FXa are expressed in the normal and injured peripheral nerve and in Schwannoma cells. Furthermore, TF and FVII were localized histologically to the node of Ranvier in the sciatic nerve. Adding exogenous FXa increased the thrombin levels in sciatic nerve (11.6 ±â€¯1.6 mU/ml compared to 35.2 ±â€¯6 mU/ml p = 0.02) and in Schwannoma cell line (4.5 ±â€¯0.2 mU/ml compared to 18.1 ±â€¯0.5 mU/ml p < 0.001), indicating a large reserve of prothrombin. In the injured nerve, FX mRNA was upregulated 1 day after injury compared to normal nerve (103 ±â€¯38 versus 1 ±â€¯0.3 FOI p < 0.001). FXa protein levels increased 1 h after the injury and then decreased significantly at 1 and 2 days following injury despite an increase in its precursor, FX. Injecting the selective FXa inhibitor apixaban immediately upon injury decreased thrombin activation and improved motor function after nerve injury. The results localize the extrinsic coagulation pathway and FXa to the PNS, suggesting a critical role for FXa in PNS thrombin formation and the possible therapeutic use of selective FXa inhibitors in nerve injuries.

A Novel Compound Targeting Protease Receptor 1 Activators for the Treatment of Glioblastoma.

Data from human biopsies, in-vitro and in-vivo models, strongly supports the role of thrombin, and its protease-activated receptor (PAR1) in the pathology and progression of glioblastoma (GBM), a high-grade glial tumor. Activation of PAR1 by thrombin stimulates vasogenic edema, tumor adhesion and tumor growth. We here present a novel six amino acid chloromethyl-ketone compound (SIXAC) which specifically inhibits PAR1 proteolytic activation and counteracts the over-activation of PAR1 by tumor generated thrombin. SIXAC effects were demonstrated in-vitro utilizing 3 cell-lines, including the highly malignant CNS-1 cell-line which was also used as a model for GBM in-vivo. The in-vitro effects of SIXAC on proliferation rate, invasion and thrombin activity were measured by XTT, wound healing, colony formation and fluorescent assays, respectively. The effect of SIXAC on GBM in-vivo was assessed by measuring tumor and edema size as quantified by MRI imaging, by survival follow-up and brain histopathology. SIXAC was found in-vitro to inhibit thrombin-activity generated by CNS-1 cells (IC50 = 5 × 10-11M) and significantly decrease proliferation rate (p < 0.03) invasion (p = 0.02) and colony formation (p = 0.03) of these cells. In the CNS-1 GBM rat animal model SIXAC was found to reduce edema volume ratio (8.8 ± 1.9 vs. 4.9 ± 1, p < 0.04) and increase median survival (16 vs. 18.5 days, p < 0.02 by Log rank Mental-Cox test). These results strengthen the important role of thrombin/PAR1 pathway in glioblastoma progression and suggest SIXAC as a novel therapeutic tool for this fatal disease.

A Linear Temporal Increase in Thrombin Activity and Loss of Its Receptor in Mouse Brain following Ischemic Stroke.

BACKGROUND: Brain thrombin activity is increased following acute ischemic stroke and may play a pathogenic role through the protease-activated receptor 1 (PAR1). In order to better assess these factors, we obtained a novel detailed temporal and spatial profile of thrombin activity in a mouse model of permanent middle cerebral artery occlusion (pMCAo). METHODS: Thrombin activity was measured by fluorescence spectroscopy on coronal slices taken from the ipsilateral and contralateral hemispheres 2, 5, and 24 h following pMCAo (n = 5, 6, 5 mice, respectively). Its spatial distribution was determined by punch samples taken from the ischemic core and penumbra and further confirmed using an enzyme histochemistry technique (n = 4). Levels of PAR1 were determined using western blot. RESULTS: Two hours following pMCAo, thrombin activity in the stroke core was already significantly higher than the contralateral area (11 ± 5 vs. 2 ± 1 mU/ml). At 5 and 24 h, thrombin activity continued to rise linearly (r = 0.998, p = 0.001) and to expand in the ischemic hemisphere beyond the ischemic core reaching deleterious levels of 271 ± 117 and 123 ± 14 mU/ml (mean ± SEM) in the basal ganglia and ischemic cortex, respectively. The peak elevation of thrombin activity in the ischemic core that was confirmed by fluorescence histochemistry was in good correlation with the infarcts areas. PAR1 levels in the ischemic core decreased as stroke progressed and thrombin activity increased. CONCLUSION: In conclusion, there is a time- and space-related increase in brain thrombin activity in acute ischemic stroke that is closely related to the progression of brain damage. These results may be useful in the development of therapeutic strategies for ischemic stroke that involve the thrombin-PAR1 pathway in order to prevent secondary thrombin related brain damage.

Thrombin and protein C pathway in peripheral nerve Schwann cells.

Thrombin and activated protein C (aPC) bound to the endothelial protein C receptor (EPCR) both activate protease-activated receptor 1 (PAR1) generating either harmful or protective signaling respectively. In the present study we examined the localization of PAR-1 and EPCR and thrombin activity in Schwann glial cells of normal and crushed peripheral nerve and in Schwannoma cell lines. In the sciatic crush model nerves were excised 1h, 1, 4, and 7days after the injury. Schwannoma cell lines produced high levels of prothrombin which is converted to active thrombin and expressed both EPCR and PAR-1 which co-localized. In the injured sciatic nerve thrombin levels were elevated as early as 1h after injury, reached their peak 1day after injury which was significantly higher (24.4±4.1mU/ml) compared to contralateral uninjured nerves (2.6±7mU/ml, t-test p<0.001) and declined linearly reaching baseline levels by day 7. EPCR was found to be located at the microvilli of Schwann cells at the node of Ranvier and in cytoplasm surrounding the nucleus. Four days after sciatic injury, EPCR levels increased significantly (57,785±16602AU versus 4790±1294AU in the contralateral uninjured nerves, p<0.001 by t-test) mainly distal to the site of injury, where axon degeneration is followed by proliferation of Schwann cells which are diffusely stained for EPCR. EPCR seems to be located to cytoplasmic component of Schwann cells and not to compact myelin component, and is highly increased following injury.

Thrombin Activity and Thrombin Receptor in Rat Glioblastoma Model: Possible Markers and Targets for Intervention?

High-grade gliomas constitute a group of aggressive CNS cancers that have high morbidity and mortality rates. Despite extensive research, current therapeutic approaches enable survival beyond 2 years in rare cases only. Thrombin and its main CNS target, protease-activated receptor-1, have been implicated in tumor progression and brain edema. Our aim was to study protease-activated receptor-1 (PAR-1) protein expression and thrombin-like activity levels in both in vitro and in vivo models of glioblastoma and correlate them with the volume of the surrounding edema. We measured the presence of PAR-1 protein using fluorescence immunohistochemistry and assessed thrombin activity in various glial and non-glial cell lines and in a CNS-1 glioma rat model using a thrombin-specific fluorescent assay. Thrombin activity was found to be highly elevated in various high-grade glioma cell lines as well as in non-glial malignant cell lines. In the CNS-1 glioma model, the level of PAR-1 fluorescence in the tumor was significantly elevated compared to adjacent regions of reactive gliosis or distant brain areas. The elevated level of thrombin activity observed in the high-grade glioma positively correlated with tumor-induced brain edema. In conclusion, thrombin is secreted from glioma cells and PAR-1 may be a new biological marker for high-grade gliomas.