Utility of three-dimensional computed tomography for anatomical assistance in endoscopic endonasal transsphenoidal surgery.

Endoscopic endonasal transsphenoidal surgery (ETSS) has been widely applied to pituitary adenomas. However, anatomical orientation is difficult when structures of the sphenoidal sinus are complicated. This study investigated the usefulness of three-dimensional computed tomography (3D-CT) modeling in planning surgical procedures for ETSS and providing anatomical guidance during surgery. CT data from 99 consecutive patients with pituitary adenoma treated between January 2008 and March 2014 were used to reconstruct 3D-CT models. Based on these images, the architecture of sphenoidal sinus, particularly structures surrounding the sellar floor, was visualized for preoperative simulation of surgical procedures. These 3D-CT images were also compared to surgical views during ETSS to evaluate applicability of the images. These models clearly demonstrated the morphology of the nasal cavity and structures of the sphenoidal sinus, including bony prominences of the internal carotid arteries (ICAs) and optic canals by successively eliminating sphenoidal structures. The 3D-CT images permitted determination of the maximum marginal line of the opening of the sellar floor by presenting vital structures such as ICAs and optic canals. With this 3D-CT model, the surgeon could access the sella more easily, open the floor widely enough for each individual patient, and resect the tumor maximally without complications. Preoperative 3D-CT models distinctly visualized the optic canals, bilateral ICAs, and complicated structures of sphenoidal septa. The 3D-CT images were useful for preoperative planning and as a road map during endoscopic surgery for pituitary adenoma, facilitating maximum tumor resection without complications.

Oct-3/4 modulates the drug-resistant phenotype of glioblastoma cells through expression of ATP binding cassette transporter G2.

BACKGROUND: Drug resistance is a major obstacle for the efficacy of chemotherapeutic treatment of tumors. Oct-3/4, a self-renewal regulator in stem cells, is expressed in various kinds of solid tumors including glioblastoma. Although Oct-3/4 expression has been implicated in the malignancy and prognosis of glioblastomas, little is known of its involvement in drug resistances of glioblastoma. METHODS: The involvement of Oct-3/4 in drug resistance of glioblastoma cells was assessed by lactate dehydrogenase assay, efflux assay of an anticancer drug, poly ADP-ribose polymerase cleavage, and in vivo xenograft experiments. Involvement of a drug efflux pump ATP binding cassette transporter G2 in Oct-3/4-induced drug resistance was evaluated by quantitative PCR analysis and knockdown by shRNA. RESULTS: Oct-3/4 decreased the susceptibility to chemotherapeutic drugs by enhancing excretion of drugs through a drug efflux pump gene, ATP binding cassette transporter G2. Moreover, the expression of Oct-3/4 was well correlated to ATP binding cassette transporter G2 expression in clinical GB tissues. CONCLUSION: Oct-3/4 elevated the ATP binding cassette transporter G2 expression, leading to acquisition of a drug-resistant phenotype by glioblastoma cells. GENERAL SIGNIFICANCE: If the drug-resistance of glioblastoma cells could be suppressed, it should be a highly ameliorative treatment for glioblastoma patients. Therefore, signaling pathways from Oct-3/4 to ATP binding cassette transporter G2 should be intensively elucidated to develop new therapeutic interventions for better efficacy of anti-cancer drugs.

miR340 suppresses the stem-like cell function of glioma-initiating cells by targeting tissue plasminogen activator.

Glioma-initiating cells (GIC) have stem-like cell properties thought to be sufficient for recurrence, progression, and drug resistance in glioblastomas. In the present study, we defined miRNA (miR)-340 as a differentially expressed miRNA in human GICs that inhibit GIC-mediated tumorigenesis. Furthermore, we defined tissue plasminogen activator (PLAT) as a critical direct target of miR340 for inhibition. Among miRNAs screened, we found that miR340 expression was decreased in all human GICs and in human glioblastoma tissues, compared with human neural stem cells and normal brain tissues. miR340 overexpression in GICs suppressed their proliferative, invasive, and migratory properties in vitro, triggering cell senescence in vitro and inhibiting GIC-induced tumorigenesis in mouse brains. shRNA-mediated silencing of PLAT in GICs phenocopied the effects of miR340 overexpression in vitro and in vivo, suggesting a potential role for tissue factor in stem-like cell function. Taken together, our results identified miR340 as a tumor suppressor that functions in GIC to enforce PLAT blockade and ablate their stem-like functions.

Oct-3/4 promotes tumor angiogenesis through VEGF production in glioblastoma.

Accumulating evidence shows that the expression level of Oct-3/4, a self-renewal regulator in stem cells, is positively correlated with the progression of various solid tumors. However, little is known regarding the influence of Oct-3/4 in the tumor angiogenesis of glioblastomas. In the present study, we subcutaneously transplanted Oct-3/4-overexpressing human glioblastoma U251 (U251/EGFP-Oct-3/4) cells into the right thighs of nude mice to evaluate the roles of Oct-3/4 in the tumor angiogenesis. Both tumor size and the number of large vessels growing in the tumor were markedly increased. In an in vitro model of angiogenesis, the conditioned media from U251/EGFP-Oct-3/4 cells significantly accelerated capillary-like tube formation compared with that of U251/EGFP cells. In comparison with U251/EGFP cells, U251/EGFP-Oct-3/4 cells had markedly elevated the expression of vascular endothelial growth factor mRNA under the control of hypoxia-inducible factor (HIF) 1α. In U251/EGFP-Oct-3/4 cells, enhanced protein expression and nuclear translocation of HIF1α were observed. Furthermore, we demonstrated that the involvement of AKT, an oncogenic signaling molecule, in the Oct-3/4 induced upregulation of HIF1α protein. Our findings suggest that Oct-3/4-expressing glioblastoma cells have the ability to adapt to low-oxygen environments within tumor masses by promoting tumor angiogenesis through AKT-HIF1 pathway.

[A case of neurosurgery for meningioma in a chronic hemodialysis patient: perioperative management of chronic hemodialysis patients requiring neurosurgery].

Here, we report a case of primary intracranial tumor in a chronic hemodialysis patient in which neurosurgery was successful. A 50-year-old man who had been on hemodialysis for 4 years was admitted to our hospital with general fatigue. Neurological examination on admission revealed mild restless. Computed tomography and magnetic resonance imaging performed on admission revealed a large (55 mm×40 mm) tumor mass in contact with the falx. The size of this tumor rapidly increased over the next month. 201Thallium-chloride single photon emission computed tomography revealed abnormal uptake in the same location as the lesion. This suggested a malignant brain tumor and surgical excision was scheduled. Two weeks prior to surgery, frequent hemodialysis was performed using nafamostat mesilate instead of heparin to prevent bleeding and to maintain electrolyte balance, and red cell concentrates and erythropoietin were administered for the improvement of anemia. A triple lumen catheter was inserted in the right internal jugular vein in preparation for emergency continuous hemodiafiltration to maintain homeostasis of circulatory dynamics. Surgery was completed without incident and the tumor was resected totally. During surgery, cerebral edema was well controlled by hyperventilation and a slightly upturned head position. Histopathological examination of the specimen confirmed atypical meningioma. Continuous hemodiafiltration was performed for 24 hours after surgery, and hemodialysis was initiated on the third day after surgery. The postoperative course was uneventful. Three weeks after surgery, the patient was discharged with no neurological deficit and resumed his daily life on maintenance hemodialysis.

Prognosis of primary central nervous system lymphoma treated with radiotherapy alone.

PURPOSE: Standard treatment for patients with primary central nervous system (CNS) lymphoma involves combining high-dose methotrexate-based chemotherapy and radiation. However, chemotherapy is sometimes contraindicated, and radiotherapy alone becomes the only option. We retrospectively investigated the clinical outcomes of primary CNS lymphoma patients treated with radiotherapy alone. MATERIALS AND METHODS: Between 1983 and 2006, 35 patients (median age 69 years, range 37-89 years) with primary CNS lymphoma were treated with radiotherapy alone. Of these, 74 % had an Eastern Cooperative Oncology Group performance status (PS) of 2-4. Most patients (91 %) received whole-brain irradiation with or without irradiation boost to the tumor site (median dose 50 Gy, range 22-50 Gy); remaining patients received partial brain irradiation. RESULTS: Median follow-up time was 20 (range 1-152) months, median survival time was 20 months, and the 1- and 2-year overall survival rates were 65 and 32 %, respectively. Median survival in patients aged <70 and ≥ 70 years was 26 and 10 months, respectively (p = 0.01). CONCLUSION: Median survival with radiotherapy alone was 20 months. Patients aged <70 years have a better prognosis than those ≥ 70 years.

[Intraventricular cryptococcoma successfully treated with liposomal amphotericin B and voriconazole: a case report].

Cryptococcal infections of the central nervous system (CNS) are infrequent in immunocompetent hosts and usually present as meningitis. However, fungal masses called cryptococcoma can sometimes be formed. We report a case in which intraventricular cryptococcoma in an immunocompetent patient was completely cured using liposomal amphotericin B (L-AMB) and voriconazole (VRCZ). A 56-year-old previously healthy man was admitted to our hospital with fever, headache and bilateral hand tremor lasting over three weeks. Cerebrospinal fluid (CSF) studies on admission showed meningitis with a white blood cell count of 228 cells/µL: mononuclear leukocytes, 96%; polymorphonuclear leukocytes, 4%; proteins, 157 mg/dL; and glucose, 50 mg/dL. Magnetic resonance imaging (MRI) showed a small, homogeneously enhanced lesion in the right lateral ventricle, and 18F-fluoro-2-deoxy-D-glucose and 11C-methionine positron emission tomography revealed abnormal uptake corresponding to the lesion. To reach a definitive diagnosis, surgical excision of the lesion was performed. Histopathological examination of the specimen showed moderate lymphocyte infiltration and numerous fungal spores, and periodic acid-Schiff and Grocott staining revealed the presence of Cryptococcus neoformans (C.neoformans) within the granuloma, leading to a diagnosis of CNS cryptococcoma. The patient underwent treatment with intravenous L-AMB for 2 weeks and oral VRCZ for 10 months. CSF cultures were negative for C.neoformans and no recurrences were identified on MRI. CNS cryptococcoma is a rare infection that may occur in patients with no known history of immunosuppression. This pathology can be difficult to distinguish from brain tumor, so early pathological diagnosis from an excised specimen is very important. Furthermore, administration of L-AMB and VRCZ may be effective in treating cases of CNS cryptococcoma.

Oct-3/4 promotes migration and invasion of glioblastoma cells.

As a result of increased glioblastoma migration and invasion into normal brain parenchyma, treatment of local tumor recurrence following initial treatment in glioblastoma patients remains challenging. Recent studies have demonstrated increased Oct-3/4 expression, a self-renewal regulator in stem cells, in glioblastomas. However, little is known regarding the influence of Oct-3/4 in glioblastoma cell invasiveness. The present study established Oct-3/4-overexpressing glioblastoma cells, which were prepared from human glioblastoma patients, to assess migration, invasion, and mRNA expression profiles of integrins and matrix metalloproteinases (MMPs). Compared with control cells, Oct-3/4 expressing-glioblastoma cells exhibited increased migration and invasion in wound healing and Matrigel invasion assays. Oct-3/4 overexpression resulted in upregulated FAK and c-Src expression, which mediate integrin signals. Vinculin accumulated along the leading edges of Oct-3/4 expressing-glioblastoma cells and associated with membrane ruffles during cell migration. Oct-3/4 expressing-cells exhibited increased MMP-13 mRNA expression and MMP-13 knockdown by shRNA suppressed cell invasion into Matrigel and organotypic brain slices. These results suggested that Oct-3/4 enhanced degradation of surrounding extracellular matrix by increasing MMP-13 expression and altering integrin signaling. Therefore, Oct-3/4 might contribute to tumor promoting activity in glioblastomas.

Accuracy of diffusion tensor magnetic resonance imaging-based tractography for surgery of gliomas near the pyramidal tract: a significant correlation between subcortical electrical stimulation and postoperative tractography.

BACKGROUND: Diffusion tensor (DT) imaging-based fiber tracking is a noninvasive magnetic resonance technique that can delineate the course of white matter fibers. OBJECTIVE: To evaluate the accuracy and usefulness of this DT imaging-based fiber tracking for surgery in patients with gliomas near the pyramidal tract (PT). METHODS: Subjects comprised 32 patients with gliomas near the PT. DT imaging-based fiber tracks of the PT were generated before and within 3 days after surgery in all patients. A tractography-integrated navigation system was used during the operation. Cortical and subcortical motor-evoked potentials (MEPs) were also monitored during resection to maximize the preservation of motor function. The threshold intensity for subcortical MEPs was examined by searching the stimulus points and changing the stimulus intensity. Minimum distance between the resection border and the illustrated PT was measured on postoperative tractography. RESULTS: In all subjects, DT imaging-based tractography of the PT was successfully performed, preoperatively demonstrating the relationship between tumors and the PT. With the use of the tractography-integrated navigation system and intraoperative MEPs, motor function was preserved postoperatively in all patients. A significant correlation was seen between threshold intensity for subcortical MEPs and the distance between the resection border and PT on postoperative DT imaging. CONCLUSION: DT imaging-based fiber tracking is a reliable and accurate method for mapping the course of subcortical PTs. Fiber tracking and intraoperative MEPs were useful for preserving motor function in patients with gliomas near the PT.

Cancer stem-like cells of glioblastoma characteristically express MMP-13 and display highly invasive activity.

Glioblastoma is the most malignant type of primary brain tumor that has been shown to contain a small population of cancer stem cells. Recent studies have suggested that cancer stem cells cause tumor recurrence based on their resistance to radiotherapy and chemotherapy. Although the highly invasive nature of glioblastoma cells is also implicated in the failure of current therapies, it is not clear whether cancer stem cells are involved in invasiveness. In this study, we isolated tumor sphere-forming cells bearing cancer stem-like characteristics such as self-renewal, multipotency, drug-resistibility, and in vivo tumorigenicity, from the human glioblastoma cell line U251, under serum-free neural stem cell culture condition, and assessed their migratory and invasive ability. These cells showed enhanced migratory and invasive ability on both Matrigel and organotypic brain slices compared to parental U251 cells. The expression of matrix metalloproteinase (MMP)-13 was specifically expressed in tumor sphere-forming cells derived from U251 and primary human glioma cells. Knockdown of MMP-13 expression by shRNA suppressed the migration and invasion of these cells. The results suggest that the highly invasive potential of cancer stem cells depends on MMP-13 enzymatic activity, thus MMP-13 might be a potential therapeutic target for glioblastomas.

Evaluation of intraoperative brain shift using an ultrasound-linked navigation system for brain tumor surgery.

Image-guided neurosurgery using navigation systems is an essential tool to increase accuracy in brain tumor surgery. However, brain shift during surgery has remained problematic. The present study evaluated the utility of a new ultrasound (US)-linked navigation system for brain tumor surgery in 64 patients with intracranial tumors. The navigation system consisted of a StealthStation navigation system, a SonoNav system, and a standard US scanner. This system determines the orientation of the US images and reformats the images from preoperative computed tomography (CT) or magnetic resonance (MR) imaging to match the US images. The system was used intraoperatively to measure brain shift several times, using the results to guide tumor resection. US-linked navigation provided information regarding brain shift, and extent of tumor resection during surgery. Evaluation of brain shift was easily achieved in all patients, without using intraoperative CT or MR imaging. Accurate information regarding the true anatomical configuration of the patient could be obtained in all phases of the operation. Magnitude of brain shift increased progressively from pre- to post-resection and depended on the type of cranial structure. Integration of the US scanner with the navigation system allowed comparisons between the intraoperative US and preoperative images, thus improving interpretation of US images. The system also improved the rate of tumor resection by facilitating the detection of remnant tumor tissue. This US-linked navigation system provides information on brain shift, and improves the accuracy and utility of image-guided surgery.

Downregulation of SPARC expression inhibits cell migration and invasion in malignant gliomas.

The secreted protein acidic and rich in cysteine (SPARC) is a secreted glycoprotein that plays an essential role in promoting the motility of invasive tumor cells. In the present study, we investigated the role of SPARC in the motile and invasive activities of human glioma cells by silencing the SPARC gene. Introduction of SPARC-targeted small interfering RNA (siRNA) into glioma cell lines resulted in downregulation of SPARC expression, and significantly suppressed glioma cell migration in vitro. Furthermore, invasiveness was significantly reduced in the cells transfected with SPARC siRNA compared with those transfected with control siRNA. In an organotypic brain slice model, co-culture of glioma spheroids and rat brain slices showed that SPARC siRNA-transfected glioma cells failed to invade the surrounding normal brain tissue. In addition, intracerebral injection of glioma cells transfected with SPARC siRNA in nude mice resulted in the formation of a non-invasive tumor, whereas injection of cells transfected with control siRNA resulted in diffuse invasive tumors. Since SPARC was exclusively expressed in the invasive zone of the tumor margin and the area surrounding tumor necrosis, we investigated the relationship between SPARC expression and hypoxic stress. SPARC expression was upregulated under hypoxic stress of 1% oxygen concentration in glioma cells. Silencing hypoxia-inducible factor-1alpha with siRNA reduced the overexpression of SPARC induced under hypoxic conditions. These results suggest that SPARC plays an essential role in the invasive activity of human glioma cells, under hypoxic conditions. Downregulation of SPARC may be a novel anti-invasion therapeutic strategy for malignant gliomas.

Silencing hypoxia-inducible factor-1alpha inhibits cell migration and invasion under hypoxic environment in malignant gliomas.

Malignant gliomas are characterized by active invasiveness, necrosis, and vascular proliferation. These pathological features have been speculated to be caused by tissue hypoxia. Hypoxia-inducible factor-1 (HIF-1), which is controlled by rapid stabilization of the HIF-1alpha subunit, is a pivotal transcriptional factor in the cellular response to hypoxia. Although many studies have described the relationship between tumor angiogenesis and hypoxic environment, the roles of HIF-1 in cell invasion have been barely elucidated in malignant gliomas. We investigated the role of HIF-1alpha in the motile and invasive activities of human glioma cells under hypoxia. Four malignant glioma cell lines, U87MG, U251MG, U373MG, and LN18, were cultured under 21 and 1% oxygen concentration. Expression of HIF-1alpha under hypoxia was observed to be much higher than that under normoxia in all cell lines. Introducing HIF-1alpha-targeted small interfering RNA (HIF-1alpha siRNA) into the glioma cell lines resulted in downregulation of HIF-1alpha expression, and significantly suppressed glioma cell migration in vitro. Furthermore, invasiveness was significantly reduced in the cells transfected with HIF-1alpha siRNA compared with those transfected with the control siRNA. Co-culture of glioma spheroids and rat brain slices showed that HIF-1alpha siRNA-transfected glioma cells failed to invade the surrounding normal brain tissue in an organotypic brain slice model. These effects of HIF-1alpha siRNA were more conspicuous under hypoxia than under normoxia. In addition, under hypoxic conditions, the level of matrix metalloproteinase (MMP)-2 mRNA was upregulated, and that of tissue inhibitor of metalloproteinase (TIMP)-2 was downregulated in all glioma cell lines. Treatment with HIF-1alpha siRNA resulted in downregulation of MMP-2 mRNA and upregulation of TIMP-2 mRNA. Furthermore, the enzyme activities of MMP-2 and MMP-9, both of which were activated by hypoxia, decreased with the introduction of HIF-1alpha siRNA. These findings suggest that overexpression of HIF-1alpha induced by hypoxic stress is an essential event in the activation of glioma cell motility through alteration of invasion-related molecules. Targeting the HIF-1alpha molecule may be a novel therapeutic strategy for malignant gliomas.

PTEN gene transfer suppresses the invasive potential of human malignant gliomas by regulating cell invasion-related molecules.

Loss of function of the tumor suppressor gene PTEN is more frequently encountered in high-grade malignant gliomas than in low-grade gliomas. High-grade gliomas are characterized by their extremely invasive behavior, suggesting that PTEN is one of the important regulators of cell motility and that alterations of its coding gene contribute to a much more invasive tumor cell phenotype. In order to clarify a role of PTEN in glioma invasion, we introduced the wild-type PTEN gene into human malignant glioma cell lines and investigated their motile and invasive activity in a brain slice model that presents circumstances analogous to normal brain conditions in vivo. In addition, we analyzed biochemical and molecular changes resulting from the transfer of PTEN in the glioma cells. Infection of recombinant replication-defective adenovirus vector containing the wild-type PTEN cDNA (Ad5CMV-PTEN) significantly inhibited the cell migration and invasion activities of PTEN-mutated glioma cell lines in in vitro migration and chemoinvasion assays. In an organotypic brain slice model, co-culture of glioma spheroids and rat brain slices demonstrated that Ad5CMV-PTEN transfected cells failed to invade surrounding normal brain tissues. Ad5CMV-PTEN transfer into the glioma cell lines lacking the wild-type gene product decreased the levels of matrix metalloproteinase (MMP)-2 mRNA and inhibited the enzymatic activities of MMP-2 and MMP-9. In contrast, mRNA expression of tissue inhibitor of metalloproteinase (TIMP)-2 was upregulated by the PTEN gene transfer. Introduction of PTEN gene in glioma cell lines markedly reduced the levels of Rac-GTP and Cdc42-GTP, activated forms of these small GTP-binding proteins, and decreased the phosphorylation levels of focal adhesion kinase. These results suggest that PTEN inhibits glioma cell invasion in two ways: suppressing proteolysis of the extracellular matrix by MMPs and modulating the migratory activity of glioma cells to a less motile nature by inactivating two Rho-family GTP-binding proteins, Rac and Cdc42.

Downregulation of laminin alpha4 chain expression inhibits glioma invasion in vitro and in vivo.

The laminin family is a structural constituent of the extracellular matrix that plays an essential role in promoting the motility of infiltrative tumor cells. We investigated the role of laminin alpha4 chain, a subset of laminin-8, -9 and -14, in the motile and invasive activities of human glioma cells. All malignant glioma cell lines examined expressed more mRNA for the laminin alpha4 and beta1 chains than for the beta2 chain, indicating that these cells predominantly express the laminin-8 isoform. Introducing an antisense oligonucleotide for laminin alpha4 chain (AS-Ln-alpha4) into the glioma cells resulted in downregulation of laminin alpha4 expression. AS-Ln-alpha4 also significantly suppressed glioma cell adhesion and migration. Furthermore, invasiveness was significantly reduced in cells transfected with AS-Ln-alpha4 compared to those transfected with the sense oligonucleotide (S-Ln-alpha4). Indeed, when glioma spheroids were implanted into rat brain slices, AS-Ln-alpha4-transfected cells failed to invade surrounding normal brain tissues. In addition, intracerebral injection of glioma cells transfected with AS-Ln-alpha4 into nude mice resulted in the formation of a noninvasive tumor, whereas injection of cells transfected with S-Ln-alpha4 resulted in diffuse invasion of brain tissue. These results suggest that mainly laminin-8 is essential for the invasive activity of human glioma cells; thus, a novel therapeutic strategy could target this molecule to treat patients with malignant glioma.

Midkine promoter-based conditionally replicative adenovirus for malignant glioma therapy.

Little is known concerning promoters or gene therapy specific for malignant glioma. To explore the potential use of midkine promoter in gene therapy for malignant glioma, we constructed a midkine promoter-based conditionally replicating adenovirus (Ad-MK). Midkine was overexpressed in malignant glioma tissues but cyclooxygenase-2 was not. The midkine promoter activity of the 600-bp fragment was 2 orders of magnitude higher in midkine-positive glioma cells than in midkine-negative primary normal brain cells. Ad-MK showed strong oncolytic effects in midkine-positive glioma cells but did not exhibit cytotoxicity in midkine-negative primary normal brain cells. The cell-killing effect was evident in E3-intact Ad-MK more than in E3-deleted Ad-MK. In an animal experiment, Ad-MK completely eradicated midkine-positive glioma xenografts. These findings indicate that midkine promoter-based conditionally replicative adenovirus might be a promising new modality of gene therapy for malignant glioma.

Introduction of p16INK4a inhibits telomerase activity through transcriptional suppression of human telomerase reverse transcriptase expression in human gliomas.

The p16 and p53 tumor suppressor proteins, which are frequently altered in malignant gliomas, have been noted as regulators of telomerase activity. However, the link between telomerase regulation and these suppressor proteins has not been adequately clarified. In the present study, we demonstrated that p16, as well as p53, suppress telomerase activity through transcriptional regulation of human telomerase reverse transcriptase (hTERT) in malignant glioma. To examine the effect of p16 and p53 on telomerase activity, we utilized wild-type p16 or p53 expression plasmid and three human glioma cell lines differing in their p53 and p16 status. Restoring p16 significantly reduced the level of telomerase activity of glioma cells. Furthermore, cotransfection of the p16 gene with 5'-deletion constructs of the hTERT promoter carrying Sp1 binding sites, repressed the transcriptional activity of hTERT promoter in p16-deleted cells. In addition, electrophoretic mobility shift assay revealed that p16 expression inhibited the binding of Sp1 to the consensus Sp1 responsive element, indicating that the recruitment of Sp1 to the hTERT proximal core promoter is inhibited by p16 protein. These results were similar to those from a p53 transfection study in p53-mutated cells. These findings implicate p16 in the transcriptional regulation of telomerase activity by inhibiting the function of Sp1 in human malignant gliomas.

Introduction of wild-type p53 enhances thrombospondin-1 expression in human glioma cells.

Malignant gliomas are distinguished from low-grade gliomas by their intense angiogenesis. In gliomas, p53 is the most frequently altered gene and is involved in the early phase of glioma development. In contrast, homozygous p16 gene deletion is more common in high-grade gliomas. In order to understand the mechanism by which gliomas become more angiogenic during the malignant transformation, we examined the relationship between thrombospondin-1, a negative regulator in angiogenesis, and these tumor suppressor genes in malignant gliomas. Human glioma cell line U-251 MG, which has mutated p53 and deleted p16, was transduced with recombinant replication-defective adenovirus vectors containing the cDNA of wild-type p53, p16, and p21. Only the induction of wild-type p53 enhanced expression of thrombospondin-1 mRNA and the protein in U-251 MG cells. Furthermore, thrombospondin-1 that was secreted in the culture medium was significantly increased (3.8-fold) as compared with that of the viral control 36 h after infection with Ad5CMV-p53. In the presence of wild-type p53 plasmid DNA, the promoter activity was increased 7.4-fold as compared with an empty expression vector control. These studies may suggest that mutation of p53 gene endows gliomas with an angiogenic phenotype by reducing thrombospondin-1 production as well as enhancing the angiogenesis inducers in the early phase of malignant progression.

[Assessment of hemodynamics of meningioma with dynamic MR imaging].

Dynamic MR imaging provides hemodynamic information about normal and pathologic tissue of the brain. The purpose of our study was to evaluate the usefulness of dynamic MR imaging in the assessment of tumor vascularity and the tumor tissue blood flow of meningiomas. We studied 13 patients with meningiomas using dynamic spin-echo MR imaging. The histological subtypes of meningioma were confirmed by the examination of surgical specimens in all patients, and tumors were meningothelial in 9 cases, fibrous in 2, transitional in 1, and psammomatous in 1. Serial images were obtained every 18-24 sec for 8 minutes and 30 seconds after rapid injection of gadolinium diethylenetriaminepentaacetic acid. Different parameters (time to peak, maximum of signal intensity and the washout ratio) were calculated directly from signal intensity curves. As an indicator of tumor vascularity, microvessel density was counted based on immunohistochemically stained sections and tumor tissue blood flow was measured using an xenon-CT system. The maximum of signal intensity corresponded to the tumor vascularity. With dynamic MR imaging, the time intensity curves (TI curves) were divided into two patterns; type 1 had a steep increase with a peak and type 2 had a slow increase to a peak followed by plateau. The maximum of signal intensity measured from TI curve of dynamic MR imaging correlated significantly with microvessel density (R2 = 0.840, p < 0.0001). Linear regression revealed a significant positive relation between the washout ratio and the tumor tissue blood flow in group showed type 1 on TI curve (R2 = 0.961, p < 0.001). There was also a significant negative correlation between the time to peak and the tumor tissue blood flow (R2 = 0.792, p < 0.01). We suggest that dynamic MR imaging is useful for evaluating hemodynamics of meningiomas.