Vascular endothelial growth factor expression under ischemic stress in human meningiomas

Vascularity of meningiomas

Information on the vascular supply to meningiomas is critical to the neurosurgeon. Most meningiomas are supplied by the external carotid artery, though many get pial contribution as well. Angiogenesis is critical for these neoplasms to grow. Vascular endothelial growth factor (VEGF) has been a popular target of research to decrease angiogenesis. Peritumoral brain edema (PTBE) is occasionally seen in meningiomas, which makes surgical resection more challenging. The exact cause of PTBE remains unclear, but a number of factors have been postulated to contribute. Assessment of the vascularity of meningiomas is best carried out with angiography, but noninvasive techniques are improving, diminishing the need for more invasive imaging. Embolization of tumors can be performed to minimize perioperative blood loss and potentially lower surgical morbidity. However, it has not been shown to improve outcomes, and procedural risks exist. Higher grade tumors commonly have higher vascularity. Higher vascular meningiomas are more likely to recur and have higher levels of VEGF. The vascularity of meningiomas remains a topic of interest and is the focus of many research projects.

Vascular endothelial growth factor signals through platelet-derived growth factor receptor β in meningiomas in vitro

Background:

Vascular endothelial growth factor (VEGF)-mediated angiogenesis mediates tumour growth and metastasis. Meningiomas are primarily benign, slow-growing, highly vascularised tumours. Aside from VEGF, there is little data on the function of major angiogenic proteins in meningiomas.

Methods:

The VEGFA, platelet-derived growth factor B (PDGFB), and their respective receptors – VEGF receptor 2 (KDR) and PDGF receptor β (PDGFRβ) – were quantified using real-time PCR and a TaqMan Protein Assay in meningiomas in vivo and in vitro. The effect of VEGFA and PDGFB on cell proliferation and the tyrosine phosphorylation of PDGFRβ were examined.

Results:

Most meningiomas displayed no KDR protein expression but elevated PDGFRβ levels. Exogenous VEGFA stimulation significantly increased cell proliferation. The PDGFRβ inhibition before stimulation with VEGFA abolished the proliferative stimuli. The VEGFA induced concentration-dependent PDGFRβ tyrosine phosphorylation comparable to PDGFB-induced PDGFRβ tyrosine phosphorylation. The PDGFRβ inhibitors gambogic acid, sunitinib, and tandutinib equally impaired the migration of meningioma cells. In addition, gambogic acid suppressed the VEGFA-induced PDGFRβ tyrosine phosphorylation.

Conclusion:

Collectively, our data suggest that VEGFA primarily regulates VEGF-mediated migration through PDGFRβ in meningiomas. The inhibitory effect of gambogic acid and tandutinib against meningioma growth in vitro suggests that selective PDGFRβ inhibitors, in combination with VEGF inhibitors, should be evaluated further as potential therapies for recurrent and malignant meningiomas.

Angiogenesis in meningiomas

Neoangiogenesis has been correlated to biological aggressiveness and an adverse clinical course of several neoplasias. Its prognostic role in meningiomas appears to be controversial. Nonetheless, if adequately quantified with specific markers and appropriate scoring methods, angiogenesis seems to be significantly associated with a high growth fraction, development of recurrences and shorter overall survival of meningiomas. As a consequence, neoangiogenesis may represent a target for therapies aimed at reducing the growth of inoperable meningiomas or recurrence risk of totally resected tumors. Even more significantly, the identification of the factors that mediate angiogenesis in meningiomas could help us to determine appropriate novel anti-angiogenic therapies for these tumors. Herein the methods for quantification of angiogenesis as well as its regulating factors in meningiomas are reviewed.

Cardiac operations in the presence of meningioma

BACKGROUND

We investigated the effect of concomitant intracranial meningiomas on perioperative and postoperative complications after cardiac operations. Also studied was the intraoperative and perioperative management and long-term outcome of such patients.

METHODS

We retrospectively evaluated 16 cardiac surgical patients with intracranial meningiomas between January 1996 and July 2007. Neurologic outcome, incidence of transient neurologic deficits, and long-term follow-up focusing on freedom from any cardiac or neurosurgical intervention were assessed.

RESULTS

Five men and 11 women with a concomitant diagnosis of intracranial meningioma underwent cardiac operations using extracorporeal circulation. One patient received additional edema prophylaxis by intravenous dexamethasone. All patients were discharged home in good physical condition. Data on long-term survival were available on 14 patients, with 12 alive. Postoperatively, 2 patients died from myocardial infarction at 26.8 months and 2 from metastatic colon cancer at 57.9 months. Perioperative neurologic disorders were observed in 2 patients, comprising one stroke after intervention for aortic dissection and one thromboembolic event 2 weeks after biologic mitral valve replacement due to anticoagulation disorders. No meningioma-related adverse event was observed.

CONCLUSIONS

The presence of intracranial meningioma does not appear to be a risk factor for patients undergoing cardiac operations. No meningioma-related neurologic sequelae were documented postoperatively. Neurosurgical consultation should be obtained in all patients preoperatively.

Expression of vascular endothelial growth factor-A and mRNA stability factor HuR in human meningiomas

We studied the expression of vascular endothelial growth factor-A (VEGF-A) and mRNA stability factor HuR in 40 supratentorial meningiomas using RT-PCR, ELISA and immunohistochemistry, and analyzed their associations with the clinicopathological characteristics, including microvascular density (MVD), peritumoral brain edema (PTBE), histological subtypes and grades, and the performance of preoperative arterial embolization. Furthermore, we investigated the involvement of HuR in the upregulation of VEGF-A expression using primary meningioma cell cultures. The level of VEGF-A is elevated in meningiomas with PTBE and in higher grade meningiomas. Preoperative arterial embolization did not significantly increase the level of VEGF-A, but it did increase the expression of HuR in tumor tissues. HuR expression was correlated positively with VEGF-A expression in meningioma tissues. In in vitro experiments, hypoxia induced the upregulation of VEGF-A expression and the cytoplasmic translocation of HuR protein in meningioma cells, and inhibition of the cytoplasmic translocation of HuR reduced the upregulation of VEGF-A expression in meningioma cells. These findings suggest that the expression of VEGF-A relates to the development of PTBE with meningiomas and the histological grade, and that HuR is involved in the upregulation of VEGF-A expression in human meningiomas.

Meningioma

Meningiomas are mostly benign tumours originating from the arachnoid cap cells, represent 13-26% of all intracranial tumours. They are more common in older age and in females. Deletion in NF2 gene and exposure to ionizing radiation are established risk factors, while the role of sex hormones is yet not clarified. Five-year survival for typical meningiomas exceeds 80%, but is poorer (5-year survival <60%) in malignant and atypical meningiomas. Papillary and haemangiopericytic morphology, large tumour size, high mitotic index, absence of progesterone receptors, deletions and loss of heterozygosity are poor prognostic factors. Complete surgical excision is the standard treatment. Radiotherapy is currently used in the clinical practice in atypical, malignant or recurrent meningioma at a total dose of 45-60Gy. However, the role of adjuvant irradiation is still controversial and has to be compared in a randomised prospective setting with a policy of watchful waiting. Radiosurgery has gained more and more importance in the management of meningiomas, especially in meningiomas that cannot be completely resected as for many skull base meningiomas. Medical therapy for patients with recurrent, progressive and symptomatic disease after repeated surgery, radiosurgery and radiotherapy is investigational. Hormonal therapy with progesterone antagonists has shown modest results, while chemotherapy with hydroxyurea appears moderately active.

Influence of transarterial chemoembolization on angiogenesis and expression of vascular endothelial growth factor and basic fibroblast growth factor in rat with Walker-256 transplanted hepatoma: An experimental study

AIM: After transarterial chemoembolization (TACE), the residual cancer cells are under extensive hypoxic or even anoxic environment. Hypoxia can lead to adaptive responses. For example, angiogenesis will help these cells survive. In this study, we examined the effect of TACE on angiogenesis and expression of vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (b-FGF) and to assess their relevance to Walker-256 transplanted hepatoma.

METHODS: Male Wistar rats were inoculated with Walker-256 tumor in the left lobe of liver. Angiography and transarterial chemoembolization were performed at d14 after transplantation. Sixty rats bearing walker-256 transplanted hepatoma were randomly divided into control group, arterial infusion group and TACE group. Each group consisted of twenty rats. Normal saline, 5-FU, 5-FU and lipiodol were infused through hepatic artery respectively. Two weeks after the infusion, staining of factor VIII, VEGF and b-FGF was performed by immunohistochemistry method in routine paraffin-embeded sections. Microvessel density (MVD) was counted in endothelial cells with positive factor VIII. Their expression levels were analyzed in conjunction with the pathologic features.

RESULTS: While a smaller tumor volume was found in TACE group (F = 37.818, P < 0.001), no statistical differences between MVD and expression of VEGF and b-FGF were found among the 3 groups. MVD of the control group, chemotherapy group and chemoemoblization group was 80.84 ± 24.24, 83.05 ± 20.29 and 85.20 ± 23.91 (F = 0.193, P = 0.873), respectively. The positive expression of VEGF and b-FGF was 75%, 75%, 85% (χ² = 0.449, P = 0.799) and 30%, 25%, 30% (χ² = 0.141, P = 0.922), respectively. Statistical analysis revealed a positive correlation between the expression of VEGF and MVD (r = 0.552, P < 0.001).

CONCLUSION: There has been little influence of lipiodol chemoembolization on the formation of tumor angiogenesis, but the development of neovascularization and expression of VEGF play important roles in establishment of collateral circulation and reconstruction of blood supply of residual cancer tissue.

Angiogenesis in brain tumors

Angiogenesis is a complex process regulated by multiple stimulatory and inhibitory factors that are able to modulate the migration and/or proliferation of microvascular cells with the objective of formation of neovasculature from preexisting vessels. It involves well-coordinated steps including production and release of angiogenic factors, proteolytic degradation of extracellular matrix components to allow formation of capillary sprout, proliferation and directional migration of microvascular cells, and the final composition of new vessels [Senger (1996) Am. J. Pathol. 149:1-7]. Angiogenesis is present in a number of hypoxic and/or ischemic conditions in the central nervous system, in particular in infarctions and infectious processes. Angiogenesis also plays an important role in malignant primary tumors. Glioblastomas, the most malignant gliomas in adults, are among the most angiogenic of all human tumors. This review will examine recent data of the role of angiogenic growth factors in the neoplastic and reactive conditions in the brain.

Correlation of clinical and biological parameters with peritumoral edema in meningioma

Peritumoral edema (PTE) in meningioma occurs variably and can adversely affect the clinical course. Moreover, the etiology of PTE in meningioma is not well documented. To examine possible correlations with PTE, the authors investigated the clinical parameters and the expressions of vascular endothelial growth factor (VEGF), matrix metalloproteinases (MMPs), and their inhibitors (TIMPs) in 20 meningiomas. The estimation of tumor volume (V(T)) and edema volume (V(E)) was done using Osiris software with magnetic resonance images and the edema index (EI) was calculated. The expression of VEGF, MMP, and TIMP were estimated in all 20 meningiomas by immunohistochemical staining, Western blotting, zymography, and laser densitometry. Tumor location was closely related with PTE. Meningiomas of the frontal lobe or the frontotemporal base had large PTEs, whereas those of the occipitoparietal lobe, posterior fossa or petroclivus were small. The level of VEGF expression bore correlation with the extent of PTE but not with histologic malignancy. MMP-2 and -9 were detected in 100% of meningiomas by zymography. The levels of MMP-9 were significantly elevated in moderate to severe edema (EI > 1.0) group (p < 0.05) whereas those of MMP-2 were elevated in minimal to mild edema (EI < 1.0) group. TIMP-1 and -2 were detected in 19 (95%) and 12 (60%) of meningiomas respectively and their presence had no significant correlations statistically with PTE between two groups (p = 0.190 and 0.089, respectively). Meningiomas with severe PTE expressed high levels of VEGF and MMP-9 and low levels of MMP-2. The expressions of MMP-2, -9, and TIMPs as well as VEGF in meningioma suggests that they are strongly related with the presence of PTE in meiningiomas, and that they might play the important role in the formation of PTE in meningiomas.

Tenascin in meningioma: expression is correlated with anaplasia, vascular endothelial growth factor expression, and peritumoral edema but not with tumor border shape

OBJECTIVE

Tenascin is an extracellular matrix glycoprotein that is expressed during embryogenesis, inflammation, angiogenesis, and carcinogenesis. The aim of this study was to investigate how tenascin expression relates to histological grade, angiogenesis, and radiological findings in meningiomas.

METHODS

Twenty typical, 20 atypical, and 5 malignant meningiomas were studied retrospectively. Tenascin expression and vascular endothelial growth factor (VEGF) expression in the tumor tissue were investigated by immunohistochemistry. Tenascin messenger ribonucleic acid expression was also studied by comparative reverse transcriptase-polymerase chain reaction. Magnetic resonance images from each case were assessed for peritumoral edema and tumor border shape.

RESULTS

The atypical and malignant meningiomas showed higher levels of tenascin expression than the typical meningiomas. The more sensitive messenger ribonucleic acid-based methods confirmed this finding. Tenascin expression was correlated with peritumoral edema and VEGF expression but not with tumor border shape. In the 13 tumors with marked tenascin expression, peritumoral edema was Grade 0 in one, Grade 1 in three, and Grade 2 in nine specimens. In the same 13 tumors, VEGF expression was Grade 1 in five and Grade 2 in eight specimens, and the findings for tumor border shape were Grade 0 in seven, Grade 1 in four, and Grade 2 in two specimens.

CONCLUSION

In meningiomas, tenascin expression is correlated with anaplasia, tumor-associated edema, and VEGF expression but not with tumor border shape. This protein may play a role in the neoplastic and/or angiogenic processes in atypical and malignant meningiomas and may thus be a potential target for meningioma therapy.

Effect of breathing a hyperoxic hypercapnic gas mixture on the oxygenation of meningiomas; preliminary results

For meningiomas in which complete resection is impossible stereotactic radiosurgery and radiotherapy are increasingly important therapeutical options. The radiosensitivity of meningiomas may be improved by increasing tumor oxygen levels. Hyperoxygenating agents, like breathing a hyperoxic hypercapnic gas mixture, have already been applied successfully in the treatment of other tumors. The aim of this study was to explore the effect of breathing a hyperoxic hypercapnic gas mixture on tumor blood oxygenation of meningiomas using magnetic resonance imaging (MRI) methods. Three patients with convexity meningiomas were each measured twice; with and without breathing the hyperoxic hypercapnic gas mixture. Tumor blood oxygenation changes were measured using blood oxygen level dependent MR imaging. Dynamic contrast enhanced MRI was used to assess functional changes of tumor vasculature. A significant increase in tumor blood oxygenation was observed under hypercapnic hyperoxic conditions in all patients, exceeding the increase in normal brain tissue. It was concluded that the oxygenation status of meningiomas can be improved by breathing a hyperoxic hypercapnic gas mixture.