Detection and quantification of vascular endothelial growth factor/vascular permeability factor in brain tumor tissue and cyst fluid: the key to angiogenesis?

Comparative Volumetric Analyses Following Bevacizumab Therapy for a Patient With Concomitant Glioblastoma, Meningioma, and Dural Arteriovenous Fistula: A Case Report and Review of Literature

Given that glioblastoma (GBM), meningioma (Mg), and dural arteriovenous fistula (dAVF) represent angiogenic diseases mainly caused by vascular endothelial growth factor (VEGF), bevacizumab (Bev) is expected to be effective against these diseases. We report a patient with concomitant GBM, Mg, and dAVF who was treated with neoadjuvant Bev, resulting in a reduction in the volume of GBM along with an improvement of clinical symptoms. An 85-year-old male presented with aphasia, gait disturbance, and dementia. Magnetic resonance imaging (MRI) showed a ring-enhanced intra-axial tumor with perifocal edema in the left temporal lobe, a dura-attached extra-axial tumor at the left sphenoid ridge, and dAVF at the left transverse-sigmoid sinus. Due to the age of the patient and low Karnofsky Performance Status (KPS) score, pharmacotherapy with a single dose of Bev was chosen over surgical resection. Three days after the Bev administration, aphasia and gait disturbance had dramatically improved. Volume reduction rates at one and five months after three administrations of Bev were 0.34% and 95.9% for GBM and 13.7% and 6.8% for meningioma, respectively. No significant change in dAVF was seen on digital subtraction angiography (DSA) during Bev therapy. VEGF concentration in GBM is known to be the highest among all types of brain tumors, including meningioma. VEGF might not play a pivotal role in the pathogenesis of dAVF. Based on this evidence from the present rare case with concomitant GBM, meningioma, and dAVF, responsiveness to Bev might depend on the level of VEGF expression.

Unlocking Hope: Anti-VEGFR inhibitors and their potential in glioblastoma treatment

PURPOSE

This systematic review summarizes evidence of VEGFR gene mutations and VEGF/VEGFR protein expression in glioblastoma multiforme (GBM) patients, alongside the efficacy and safety of anti-VEGFR tyrosine kinase inhibitors (TKIs) for GBM treatment.

METHODS

A comprehensive literature review was conducted using PubMed up to August 2023. Boolean operators and MeSH term "glioma," along with specific VEGFR-related keywords, were utilized following thorough examination of existing literature.

RESULTS

VEGFR correlates with glioma grade and GBM progression, presenting a viable therapeutic target. Regorafenib and axitinib show promise among studied TKIs. Other multi-targeted TKIs (MTKI) and combination therapies exhibit potential, albeit limited by blood-brain barrier penetration and toxicity. Combining treatments like radiotherapy and enhancing BBB penetration may benefit patients. Further research is warranted in patient quality of life and biomarker-guided selection.

CONCLUSION

While certain therapies hold promise for GBM, future research should prioritize personalized medicine and innovative strategies for improved treatment outcomes.

Advancing Healthcare: Synergizing Biosensors and Machine Learning for Early Cancer Diagnosis

Cancer is a fatal disease and a significant cause of millions of deaths. Traditional methods for cancer detection often have limitations in identifying the disease in its early stages, and they can be expensive and time-consuming. Since cancer typically lacks symptoms and is often only detected at advanced stages, it is crucial to use affordable technologies that can provide quick results at the point of care for early diagnosis. Biosensors that target specific biomarkers associated with different types of cancer offer an alternative diagnostic approach at the point of care. Recent advancements in manufacturing and design technologies have enabled the miniaturization and cost reduction of point-of-care devices, making them practical for diagnosing various cancer diseases. Furthermore, machine learning (ML) algorithms have been employed to analyze sensor data and extract valuable information through the use of statistical techniques. In this review paper, we provide details on how various machine learning algorithms contribute to the ongoing development of advanced data processing techniques for biosensors, which are continually emerging. We also provide information on the various technologies used in point-of-care cancer diagnostic biosensors, along with a comparison of the performance of different ML algorithms and sensing modalities in terms of classification accuracy.

Liquid biomarkers in glioma

An ideal biomarker must meet several parameters to enable its successful adoption; however, the nature of glioma makes it challenging to discover valuable biomarkers. While biomarkers require simplicity for clinical implementation, anatomical features and the complexity of the brain make it challenging to perform histological examination. Therefore, compared to biomarkers from general histological examination, liquid biomarkers for brain disease offer many more advantages in these minimally invasive methods. Ideal biomarkers should have high sensitivity and specificity, especially in malignant tumors. The heterogeneous nature of glioma makes it challenging to determine useful common biomarkers, and no liquid biomarker has yet been adopted clinically. The low incidence of brain tumors also hinders research progress. To overcome these problems, clinical applications of new types of specimens, such as extracellular vesicles and comprehensive omics analysis, have been developed, and some candidate liquid biomarkers have been identified. As against previous reviews, we focused on and reviewed the sensitivity and specificity of each liquid biomarker for its clinical application. Perusing an ideal glioma biomarker would help uncover the common underlying mechanism of glioma and develop new therapeutic targets. Further multicenter studies based on these findings will help establish new treatment strategies in the future.

Perianeurysmal parenchymal cysts – Case series and literature review

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Intracranial cysts are associated with a number of vascular lesions.

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They predominantly occur in larger, partially-thrombosed aneurysms and in older patients.

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There is a trend towards enlargement over time if untreated and a likelihood of recurrence following treatment.

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We hypothesise the cysts arise either from dilated Virchow-Robin spaces and/or inflammatory processes.

Multimodal Role of PACAP in Glioblastoma

Glioblastoma multiforme (GBM) is the deadliest form of brain tumors. To date, the GBM therapeutical approach consists of surgery, radiation-therapy and chemotherapy combined with molecules improving cancer responsiveness to treatments. In this review, we will present a brief overview of the GBM classification and pathogenesis, as well as the therapeutic approach currently used. Then, we will focus on the modulatory role exerted by pituitary adenylate cyclase-activating peptide, known as PACAP, on GBM malignancy. Specifically, we will describe PACAP ability to interfere with GBM cell proliferation, as well as the tumoral microenvironment. Considering its anti-oncogenic role in GBM, synthesis of PACAP agonist molecules may open new perspectives for combined therapy to existing gold standard treatment.

Occurrence of Fibrotic Tumor Vessels in Grade I Meningiomas Is Strongly Associated with Vessel Density, Expression of VEGF, PlGF, IGFBP-3 and Tumor Recurrence

Angiogenesis is a key feature during oncogenesis and remains a potential target of antiangiogenic therapy. While commonly described in high-grade lesions, vascularization and its correlation with prognosis in grade I meningiomas is largely unexplored. In the histological classification, not only the number but also the composition of blood vessels seems to be important. Therefore, tumor vessel density and fibrosis were correlated with clinical and imaging variables and prognosis in 295 patients with intracranial grade I meningioma. Expression of pro-angiogenic proteins within the meningiomas was investigated by proteome analyses and further validated by immunohistochemical staining. Fibrotic tumor vessels (FTV) were detected in 48% of all tumors and strongly correlated with vessel density, but not with the histopathological tumor subtype. Occurrence of FTV was correlated with a 2-fold increased risk of recurrence in both univariate and multivariate analyses. Explorative proteome analyses revealed upregulation of VEGF (vascular endothelial growth factor), PlGF (placental growth factor), and IGFBP-3 (insulin-like growth factor-binding protein-3) in tumors displaying FTV. Immunohistochemical analyses confirmed strong correlations between tumor vessel fibrosis and expression of VEGF, PlGF, and IGFBP-3. Presence of FTV was strongly associated with disruption of the arachnoid layer on preoperative MRI in univariate and multivariate analyses. In summary, the occurrence of fibrotic tumor vessels in grade I meningiomas is strongly associated with vessel density, disruption of the arachnoid layer, expression of VEGF, PlGF, IGFBP-3 and tumor recurrence.

Gelfoam Padding, an innovative surgical technique improving the total resection rate of cystic gliomas

OBJECTIVE

The cystic gliomas are the special type of malignant tumors in the brain and often lead to unsatisfied prognosis, but the microsurgical resection is still the most important treatment. However, they are difficult to be totally removed with craniotomy, especially for those who have flimsy cyst walls. Recently, we attempted to resect them via an innovative surgical technique, "Gelfoam Padding", in order to improve the total resection rate of the tumors safely.

PATIENTS AND METHODS

Fifteen patients suffering intracerebral cystic gliomas underwent surgical intervention via "Gelfoam Padding" technique between 2015 and 2018, and the different histopathological results and their features of cyst walls were recorded. Then, the total resection rate of tumors as well as the complications after surgeries were analyzed to assess the applied value of this technique.

RESULTS

All the patients were improved in the clinical symptoms after the operations. According to the intraoperative assessment and MRI examinations performed within 72 h after surgery, total resection of the tumor was achieved in all patients. Besides, there were no serious postoperative complications in these cases with this technique.

CONCLUSION

The cystic glioma with the flimsy wall was the best applied indication of "Gelfoam Padding" technique, which could not only improve the total resection rate of tumors, but also be safe for the patients.

Targeting Glutamine Addiction in Gliomas

The most common malignant brain tumors are those of astrocytic origin, gliomas, with the most aggressive glioblastoma (WHO grade IV) among them. Despite efforts, medicine has not made progress in terms of the prognosis and life expectancy of glioma patients. Behind the malignant phenotype of gliomas lies multiple genetic mutations leading to reprogramming of their metabolism, which gives those highly proliferating cells an advantage over healthy ones. The so-called glutamine addiction is a metabolic adaptation that supplements oxidative glycolysis in order to secure neoplastic cells with nutrients and energy in unfavorable conditions of hypoxia. The present review aims at presenting the research and clinical attempts targeting the different metabolic pathways involved in glutamine metabolism in gliomas. A brief description of the biochemistry of glutamine transport, synthesis, and glutaminolysis, etc. will forego a detailed comparison of the therapeutic strategies undertaken to inhibit glutamine utilization by gliomas.

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.

Hypoxia and EGF Stimulation Regulate VEGF Expression in Human Glioblastoma Multiforme (GBM) Cells by Differential Regulation of the PI3K/Rho-GTPase and MAPK Pathways

Glioblastoma multiforme (GBM) is one of the most common and deadly cancers of the central nervous system (CNS). It is characterized by the presence of hypoxic regions, especially in the core, leading to an increase in vascularity. This increased vascularization is driven by the expression of the major angiogenic inducer VEGF and the indirect angiogenic inducer Epidermal growth factor (EGF), which stimulates VEGF expression. In this study, we examine the regulation of VEGF by both hypoxia and the EGF signaling pathway. We also examine the involvement of pathways downstream from EGF signaling, including the mitogen-activated protein kinase/extracellular regulated kinase (MAPK/ERK) pathway and the Phosphatidylinositol-3-kinase/RhoA/C (PI3K/RhoA/C) pathway in this regulation. Our results show that VEGF expression and secretion levels increase following either hypoxia or EGF stimulation, with the two stimuli signaling in parallel. We also observed an increase in ERK and protein kinase B (Akt) phosphorylation, in response to EGF stimulation, with kinetics that correlated with the kinetics of the effect on VEGF. Using pharmacological inhibitors against ERK and PI3K and small interfering RNAs (siRNAs) against RhoA and RhoC, we found that both the ERK and the PI3K/RhoA/C pathways have to cooperate in order to lead to an increase in VEGF expression, downstream from EGF. In response to hypoxia, however, only ERK was involved in the regulation of VEGF. Hypoxia also led to a surprising decrease in the activation of PI3K and RhoA/C. Finally, the decrease in the activation of these Rho-GTPases was found to be mediated through a hypoxia-driven overexpression of the Rho-GTPase GTPase activating protein (GAP), StarD13. Therefore, while under normoxic conditions, EGF stimulates the activation of both the PI3K and the MAPK pathways and the induction of VEGF, in glioblastoma cells, hypoxic conditions lead to the suppression of the PI3K/RhoA/C pathway and an exclusive switch to the MAPK pathway.

Effect of bevacizumab against cystic components of brain tumors

Background

Bevacizumab improves symptoms via reducing the peritumoral edema and/or normalizing blood brain barrier, and occasionally via reducing the tumor size. However, the effect against active cystic components has not been documented yet.

Materials and Methods

Between 2008 and 2018, 139 patients with primary or metastatic brain tumors were treated with bevacizumab (BEV) in our institution. The images and symptoms before and after administration of BEV were examined, and changes in size of cysts were evaluated as follows: CR (complete disappearance), PR (reduction by ≥50%), MR (reduction by ≥25%), SD (size change <25%), PD (increase by ≥25%). The effect of BEV on tumor itself was determined according to Response Assessment in Neuro‐Oncology criteria.

Results

Of the 139 patients, 21 (15.1%) had cystic components. The best responses of cysts to BEV treatment were as follows: CR 6, PR 7, MR 4, SD 4. The group of patients with progressively increasing cysts prior to BEV treatment had significant cyst size reduction compared to stable cyst size groups, at initial imaging after BEV (mean 62.6% vs 22.5%, P = .0055) and at best response timing (mean 76.3% vs 32.8%, P = .0050). Patients with cysts showed significant improvement in symptoms after the treatment with BEV compared to patients without cysts (P = .0033). However, response rate was not different between patients with or without cysts. Overall survival after starting BEV was not different between glioblastoma patients with or without cysts.

Conclusion

Bevacizumab is effective against progressively increasing cysts. Although cysts reduction effect and tumor response and/or overall survival are independent, BEV may be effective in patients who are symptomatic due to cyst enlargement.

Etiologic Role of Kinases in the Progression of Human Cancers and Its Targeting Strategies

Cancer is one of the dominant causes of death worldwide while lifelong prognosis is still inauspicious. The maturation of the cancer is seen as a process of transformation of a healthy cell into a tumor-sensitive cell, which is held entirely at the cellular, molecular, and genetic levels of the organism. Tyrosine kinases can play a major, etiologic role in the inception of malignancy and devote to the uncontrolled proliferation of cancerous cells and the progression of a tumor as well as the development of metastatic disease. Angiogenesis and oncogene activation are the major event in cell proliferation. The growth of a tumor and metastasis are fully depending on angiogenesis and lymphangiogenesis triggered by chemical signals from tumor cells in a phase of rapid growth. Tyrosine kinase inhibitors are compounds that inhibit tyrosine kinases and effective in targeting angiogenesis and blocking the signaling pathways of oncogenes. Small molecule tyrosine kinase inhibitors like afatinib, erlotinib, crizotinib, gefitinib, and cetuximab are shown to a selective cut off tactic toward the constitutive activation of an oncogene in tumor cells, and thus contemplated as promising therapeutic approaches for the diagnosis of cancer and malignancies.

Increased L1CAM (CD171) levels are associated with glioblastoma and metastatic brain tumors

L1 cell adhesion molecule (L1CAM) is a member of the immunoglobulin-like cell-adhesion molecule family that was shown to be associated with a worse prognosis in several human cancers. L1 ectodomain shedding via vesicles or exosomes has been detected in extracellular fluids after cleavage from the cell surface by metalloproteases. We evaluated the presence of L1CAM in cyst fluid and tissue from glioblastomas or brain metastases.The amount of L1CAM in cyst fluid of 9 glioblastomas and 11 brain metastases was assessed using enzyme-linked immunosorbent assay (ELISA). Corresponding tumor tissue slices were stained immunohistochemically for L1CAM. Cerebrospinal fluid of 20 non-tumor patients served as controls.Mean levels of L1CAM in tumor cyst fluid were significantly higher in glioblastoma (6118 ± 4095 ng/mL) and metastasis patients (8001 ± 6535 ng/mL) than in CSF of control patients (714 ± 22 ng/mL). The immunohistochemical expression of L1CAM in corresponding tissue was significantly higher in metastases than in glioblastomas.The present study demonstrates high levels of L1CAM in cyst fluid of glioblastoma and metastatic brain tumors. Soluble L1CAM may represent a motility promoting molecule in cancer progression, a co-factor for development of tumor cysts and a target for new treatment strategies.

Angiogenic growth factors in myocardial infarction: a critical appraisal

In the recent past, substantial advances have been made in the treatment of myocardial infarction (MI). Despite the impact of these positive developments, MI remains to be a leading cause of morbidity as well as mortality. An interesting hypothesis is that the development of new blood vessels (angiogenesis) or the remodeling of preexisting collaterals may form natural bypasses that could compensate for the occlusion of an epicardial coronary artery. A number of angiogenic factors are proven to be elicited during MI. Exogenous supplementation of these growth factors either in the form of recombinant protein or gene would enhance the collateral vessel formation and thereby improve the outcome after MI. The aim of this review is to describe the nature and potentials of different angiogenic factors, their expression, their efficacy in animal studies, and clinical trials pertaining to MI.

Cerebrospinal Fluid (Vascular Endothelial Growth Factor) and Serologic (Recoverin) Tumor Markers for Malignant Glioma

BACKGROUND

Clinically useful tumor markers have yet to be identified for malignant glioma. We report on two potential novel tumor markers, vascular endothelial growth factor (VEGF) and recoverin (protein A). VEGF is a highly specific endothelial cell activator that induces angiogenesis both in vivo and in vitro. Our study was designed to assess whether VEGF could be measured in the cerebrospinal fluid (CSF) of patients with cerebral neoplasms and used as a marker of particular tumors. We also studied serum recoverin levels in patients with various brain tumors and compared these to controls. Recoverin is a detectable serologic protein that is expressed in patients with cancer-associated retinopathy, a paraneoplastic syndrome.

METHODS

In the VEGF arm, we used a solid-phase ELISA to determine the levels of VEGF. CSF samples from patients with anaplastic astrocytoma and glioblastoma multiforme (GBM) and with metastatic and nonastrocytic brain tumors were compared with nontumor control samples. In our recoverin study, an immunoenzymetric assay was used to measure the serum recoverin levels patients with glioma and compared with controls.

RESULTS

In the VEGF arm, 89% of samples with malignant astrocytoma and 27% of nonastrocytoma samples had detectable levels of VEGF. VEGF was not detectable in normal CSF samples. The levels of VEGF were significantly higher in high-grade astrocytomas than in nonastrocytic tumors. Recoverin levels were 10-fold higher in patients with recurrent GBM relative to controls. In patients with low-grade glioma, anaplastic glioma, and GBM with no evidence of recurrence, a 3- to 5-fold increase was observed.

CONCLUSIONS

VEGF is detectable in CSF and may be a potential marker for differentiating astrocytic from nonastrocytic tumors. Recoverin is detectable in serum and may be a useful glioma tumor marker, especially for recurrent active disease. These markers may have application for tumor diagnosis, surveillance, and treatment response.

Rapid increase in cystic volume of an anaplastic astrocytoma misdiagnosed as neurocysticercosis: A case report

Reports describing a rapid increase in the cystic volume of anaplastic astrocytoma (AA) in a short time frame are rare. The present study reports the case of a 68-year-old male who was admitted to the No. 9 People's Hospital, Shanghai Jiaotong University School of Medicine (Shanghai, China), with a small cystic brain lesion and positive immunological testing for cysticercosis. Head magnetic resonance imaging (MRI) showed a cystic lesion, 6 mm in diameter, in the left frontal lobe. Neurocysticercosis was suspected and the patient was treated with a clinical trial of albendazole and steroids. A period of 25 days later, the patient's condition had deteriorated, and MRI revealed a cystic lesion in the left frontal lobe; thereafter, the cystic lesion was removed and a diagnosis of AA was established. The tumor was soft, ivory white and gelatinous due to myxoid degeneration. In this case, tumor-related angiogenesis and microvascular extravasation (blood-brain barrier disruption) may have been the main cause of the rapid increase in the cystic volume in such a short time frame. The similarity of the glioma and cysticercus antigens may have been the cause of the positive reactions in the cystic fluid. The present study reports the rare occurrence of a rapid increase of cystic volume and potential diagnostic difficulties.

Modeling of Cancer Classifier to Predict Site of Origin

Cancer classification based on site of origin is very significant research issue for prediction and treatment of cancer. This paper is addressing the problem of cancer classification for Homo Sapiens genes composed of amino acid chain. Cancer gene network is realized by equivalent electrical circuits based on hydrophilic/ hydrophobic property of amino acid and a classifier is modeled to determine the cancer origin. The phase value, peak gain value and shape of Nyquist curve of network model are investigated to characterize different types of cancer gene origins. The model achieves 81.09% of classification accuracy and proves to be more sensitive and simple, since it shows 69% better performance compare to the existing nucleotide based method. The proposed classifier successfully predicts the site of origin of 93 cancer gene samples.

VEGF and VEGFR2 in dentigerous cysts associated with impacted third molars

The aims of this study were to determine the presence and distribution of vascular endothelial growth factor (VEGF) and vascular endothelial growth factor receptor-2 (VEGFR2) in dentigerous cysts compared with normal dental follicles as a control tissue and to evaluate endothelial cells and proliferating cells as indicators of angiogenic activity in these tissues.Twenty specimens histologically diagnosed as dentigerous cysts and 20 dental follicle specimens were included. Immunohistochemistry (IHC) using anti-VEGF and anti-VEGFR2 antibodies stained for the growth factor and its receptor, while anti-CD34 and anti-CD146 antibodies were used to identify endothelial cells. Anti-proliferating cell nuclear antigen (PCNA) antibody detected proliferating cells within the specimens. Slides were examined microscopically and results evaluated using kappa statistics, negative binomial regression and ordinal logistic regression.The mean age for patients with dentigerous cysts was 23 years and they were more common in males. Proteins for VEGF, VEGFR2, PCNA, CD34, and CD146 were expressed in all dentigerous cysts and dental follicles. VEGF and VEGFR2 were expressed on several cell types within the tissues, however there was a significantly greater percentage of positive staining in dentigerous cysts compared with dental follicles (odds ratio = 31.24, p < 0.001). CD34(+), CD146(+), and PCNA(+) cells were observed in both dentigerous cysts and dental follicles but for all markers there were significantly more positive cells in dentigerous cysts (p < 0.001); this was especially evident in cases associated with inflammation. PCNA was seen in most endothelial cells lining small thin walled blood vessels suggesting endothelial proliferation. There was a high level of intra- and inter-examiner agreement (kappa 0.77 and 0.75, respectively).VEGF and VEGFR2 and angiogenic activity are present in dental follicles and dentigerous cysts and may contribute to local bone resorption for tooth eruption or the development and progression of dentigerous cysts.

Infrared-active quadruple contrast FePt nanoparticles for multiple scale molecular imaging

A single nanomaterial with multiple imaging contrasts and functions is highly desired for multiscale theragnosis. Herein, we demonstrate single 1-1.9 μm infrared-active FePt alloy nanoparticles (FePt NPs) offering unprecedented four-contrast-in-one molecular imaging - computed tomography (CT), magnetic resonance imaging (MRI), photoacoustic (PA) imaging, and high-order multiphoton luminescence (HOMPL) microscopy. The PA response of FePt NPs outperforms that of infrared-active gold nanorods by 3- to 5.6-fold under identical excitation fluence and particle concentrations. HOMPL (680 nm) of an isolated FePt NP renders spatial full-width-at-half-maximum values of 432 nm and 300 nm beyond the optical diffraction limit for 1230-nm and 920-nm excitation, respectively. The in vivo targeting function was successfully visualized using HOMPL, PA imaging, CT, and MRI, thereby validating FePt as a single nanomaterial system covering up to four types (Optical/PA/CT/MRI) of molecular imaging contrast, ranging from the microscopic level to whole-body scale investigation.

Does glioblastoma cyst fluid promote sciatic nerve regeneration?

Glioblastoma cyst fluid contains growth factors and extracellular matrix proteins which are known as neurotrophic and neurite-promoting agents. Therefore, we hypothesized that glioblastoma cyst fluid can promote the regeneration of injured peripheral nerves. To validate this hypothesis, we transected rat sciatic nerve, performed epineural anastomosis, and wrapped the injured sciatic nerve with glioblastoma cyst fluid- or saline-soaked gelatin sponges. Neurological function and histomorphological examinations showed that compared with the rats receiving local saline treatment, those receiving local glioblastoma cyst fluid treatment had better sciatic nerve function, fewer scars, greater axon area, counts and diameter as well as fiber diameter. These findings suggest that glioblastoma cyst fluid can promote the regeneration of injured sciatic nerve and has the potential for future clinical application in patients with peripheral nerve injury.

Preclinical impact of bevacizumab on brain and tumor distribution of irinotecan and temozolomide

Glioblastoma (GBM) is the most common primary malignant brain tumour in adults. Prognosis of GBM patients is poor with median overall survival around 15 months. Temozolomide is the chemotherapeutic agent used in the standard of care of newly diagnosed GBM patients relying on radiotherapy with concurrent chemotherapy followed by chemotherapy alone. Irinotecan has shown some efficacy in recurrent malignant gliomas. Bevacizumab has been combined with irinotecan in the treatment of recurrent GBM and with temozolomide in newly diagnosed GBM. As the efficacy of GBM treatments relies on their brain distribution through the blood brain barrier, the aim of the present preclinical work was to study, in in vivo models, the impact of bevacizumab on brain and tumor distribution of temozolomide and irinotecan. Our results show that bevacizumab pre-treatment was associated with a reduced temozolomide brain distribution in tumor-free mice. In tumor bearing mice, bevacizumab increased temozolomide tumor distribution, although not statistically significant. In both tumor-free and tumor-bearing mice, bevacizumab does not modify brain distribution of irinotecan and its metabolite SN-38. Bevacizumab impacts brain distribution of some anti-tumor drugs and potentially their efficacy in GBM. Further studies are warranted to investigate other therapeutic combination.

Expression of VEGF and collagen XVIII in meningiomas: correlations with histopathological and MRI characteristics

BACKGROUND

The objective of this study was to assess the possibility of predicting histological characteristics of meningiomas on the basis of preoperative MRI and the correlation of the expression of vascular endothelial growth factor (VEGF) and collagen XVIII with histological parameters already established as predictive of the course of these tumors.

METHODS

Expression of VEGF and collagen XVIII as well as other histological characteristics was examined in meningioma tissues from 20 patients. Preoperative MRI, including dynamic imaging of contrast enhancement, was analyzed. Times to maximum enhancement and maximum intensity increase were noted from dynamic imaging. The relative intensity of the tumor in fluid-attenuated inversion recovery (FLAIR), T2-weighted and contrast enhanced T1-weighted images, as well as volumes of tumor and edema, was calculated. The edema-tumor volume ratio was defined as the edema index (EI).

RESULTS

Both VEGF and collagen XVIII were expressed in all meningioma samples. Edema was present in 60 % of cases. The strongest correlation of VEGF expression was to EI. Among histological parameters, microvessel density (MVD) and cellularity correlated moderately with VEGF. Collagen XVIII expression correlated strongly with the maximal intensity increase after contrast agent administration (ρ = 0.71, P = 0.001) as well as with MVD and intensity of the meningioma on FLAIR images.

CONCLUSION

Meningiomas with faster and more intense enhancement in dynamic studies, indicative of good tumor blood supply and permeability of vasculature, are associated with high levels of collagen XVIII and VEGF expression. Occurrence of peritumoral edema in meningiomas is strongly correlated with expression of VEGF.

Drug review: Safety and efficacy of bevacizumab for glioblastoma and other brain tumors

Glioblastoma is a highly vascular tumor that expresses vascular endothelial growth factor, a key regulator of angiogenesis and tumor blood vessel permeability. Bevacizumab is a monoclonal antibody that inhibits vascular endothelial growth factor and the growth of gliomas. Bevacizumab monotherapy has proven effective for recurrent glioblastoma, and it extended progression-free survival and improved patient quality of life in various clinical trials. Some patients who receive bevacizumab experience improvements in neurological symptoms and steroid dose reductions. Bevacizumab induces a dramatic and rapid radiological response, but non-enhancing lesions are often detected on magnetic resonance imaging without enhancing lesions. Rebound phenomena such as rapid tumor regrowth are occasionally observed after the discontinuation of bevacizumab therapy. Therefore, Response Assessment in Neuro-Oncology criteria were recently devised to evaluate the efficacy and radiological response of bevacizumab treatment. Hypertension and proteinuria are characteristic adverse events associated with bevacizumab therapy. In addition, many fatal adverse events such as intracranial hemorrhage and venous thromboembolism are reported in patients treated with bevacizumab. However, these events are also associated with glioma itself, and careful attention needs to be paid to these events. Bevacizumab is used to treat various diseases including radiation necrosis and recurrent brain tumors such as brain metastases, schwannoma and meningioma, but additional clinical trials are necessary. The efficacy and current problems associated with bevacizumab in the treatment of glioblastoma and other brain tumors are reviewed.

Expression of vascular endothelial growth factor (VEGF) and its two receptors in diffusely infiltrating astrocytomas and relationship to proliferative activity of tumor cells

We studied the relationships among vascular endothelial growth factor (VEGF), its receptors (Flt1 and Flk1), and MIB-1. Their expression in 47 diffusely infiltrating astrocytomas obtained at surgery or autopsy was investigated by the ABC method and analyzed quantitatively. The positive rate of VEGF in tumor cells was higher than that in endothelial cells, and Flk1 was lower in tumor cells (P < 0.01, 0.01), whereas Flt1 in both tumor cells and endothelial cells was found at similar levels (P > 0.05). In tumor cells, VEGF became high with increased histological grades (P < 0.01). whereas both Flt1 and Flk1 were higher in grade 4 than in grades 2 and 3 (P < 0.01, 0.05). VEGF, Flt1, and Flk1 in endothelial cells were also highly expressed in grade 4 (P < 0.01). The distribution of MIB-1-positive nuclei in grade 4 was similar to VEGF, and the percent of positivity from grade 2 to grade 4 also increased (P < 0.01). There was a linear positive correlation between VEGF and both Flt1 and Flk1 in both tumor cells and endothelial cells (P < 0.01). So was the percent of positivity with VEGF, Flt1, and Flk1 in tumor cells and endothelial cells (P < 0.01). The experiment suggests that VEGF may act as a growth factor for both endothelial cells and tumor cells. VEGF, Flt1, and Flk1 can be considered as indicators of the malignancy potential of diffusely infiltrating astrocytomas. The expression of VEGF and the two receptors may be affected by the proliferative activity of tumor cells.

Intracranial Perianeurysmal Cyst: Still a Dilemma

Intracranial perianeurysmal cysts constitute an extremely rare entity with very few cases reported in the literature. These cysts present an unknown mechanism of formation and clinical significance. Several theories based on isolated cases have been proposed, without drawing a clear conclusion. It is also unknown if follow-up with imaging techniques is required or which is the most appropriate treatment. We describe an atypical case handled with a satisfactory outcome after endovascular treatment, suggesting the importance of hydrodynamic forces as the key factors in the mechanism of formation. We believe that this case can help in future analysis of this rare entity.

The levels of vascular endothelial growth factor-A and placental growth factor-2 in embryopathy associated with experimental diabetic gestation

The objective of this study was to investigate the role of vascular endothelial growth factor-A (VEGF-A) and placental growth factor-2 (PlGF-2) in fetal malformations associated with maternal diabetes. Diabetes was induced in female rats. Diabetic and control female rats were made pregnant. On Day 15 of gestation, rats were sacrificed and embryos and their placentas and membranes were dissected out of the uterine horns. Following morphological examination, embryos and their placentas and membranes were homogenized and used for assayed of VEGF-A and PlGF-2 levels. Embryos of diabetic mothers, exhibited significantly (P < 0.05) shorter crown-to-rump lengths, smaller weights, and heavier placental weights. Experimentally induced maternal diabetes was accompanied by decreased VEGF-A in embryos and associated structures. The levels of PlGF-2 in non-malformed embryos of diabetic gestation and their placentas were significantly (P < 0.05) lower than the average of controls. These results might indicate defective vascularization with a consequent morphological or anatomical anomalies or more subtle biochemical or metabolic changes. In diabetic mothers, a statistically significant (P < 0.05) decrease was noted in the level of VEGF-A in plasma of diabetic rats with a small non-significant decrease in PlGF-2. Like many other diabetic complications, diabetes-induced embryopathies might have vascular origin and correcting the disturbances in these angiogenic factors might help decrease the incidence of malformation in diabetic gestation.

Angiogenesis in gliomas

Angiogenesis, the sprouting of new blood vessels from preexisting blood vessels, is a hallmark of glioma progression. Malignant gliomas are among the most lethal tumors with a very dismal prognosis, despite advances in standard therapy, including surgery, radiation, and chemotherapy. The median survival of patients with malignant gliomas has changed little in the last few years and is still measured in months. In an attempt to develop new therapeutic strategies and identify the molecular mechanism involved in glioma growth and progression, there has been extraordinary scientific interest in the past 2 decades in angiogenic responses associated with gliomas. This chapter focuses on the molecular mechanism of glioma angiogenesis and summarizes some of the therapeutic approaches based on antiangiogenesis.

Angiogenesis and gliomas: current issues and development of surrogate markers

Despite significant improvements, current therapies have yet to cure infiltrative gliomas. Glioma progression is strongly dependent on the development of a new vascular network that occurs primarily by angiogenesis. Hypoxia and genetic anomalies within a glioma trigger the angiogenic switch, thus upregulating angiogenic factors and downregulating antiangiogenic factors. The main factors indicative of angiogenesis are now well known, and more recently, differences based on grade and subtype have been reported. New data also indicate a potential role for postnatal vasculogenesis with bone marrow endothelial progenitors in addition to angiogenesis in tumor vascular development. All of these factors may have therapeutic implications. Antiangiogenic therapies are presently being developed; more than 80 trials are ongoing. Initial results indicate that epidermal growth factor receptor inhibitors, anti-metalloproteases, and thalidomide do not demonstrate strong anti-tumor activity. Thus, antiangiogenic agents combined with conventional therapies and second-generation antiangiogenic drugs for targeting multiple molecular pathways are presently being tested. Clinical experience also demonstrates the failure of conventional imaging to monitor these new approaches accurately. New advances in the design of surrogate markers for angiogenesis have been reported for both magnetic resonance and molecular imaging techniques. This article summarizes the mechanisms of the angiogenic switch based on tumor grade and subtype, reviews completed and ongoing clinical trials, and details the present and the future of surrogate markers for angiogenesis in gliomas.

Absence of Tight Junctions between Microvascular Endothelial Cells in Human Cerebellar Hemangioblastomas

OBJECTIVE:

Endothelial tight junctions form the main barrier of the blood-brain barrier (BBB). In human hemangioblastomas, cyst formation is a common and important clinical manifestation. Although most researchers consider that the cyst formation in hemangioblastomas may be caused by the breakdown of the BBB, the underlying molecular mechanisms for cyst formation remain unknown. At present, there are few reports about the change of tight junctions in microvessel endothelium of human hemangioblastomas. The purpose of this research is to investigate the change of tight junction and its major molecular components in microvessel endothelium of human hemangioblastomas.

METHODS:

Twenty-four consecutive patients with cerebellar hemangioblastomas were studied. Tight junctions in the microvessels of hemangioblastomas and the control brain were examined by electron microscopy. Immunohistochemistry and double immunofluorescent microscopy were used to analyze the expression of CLN5 and its relationship with astrocytic endfeet in the control brain and hemangioblastomas. Quantitative real-time reverse-transcriptase polymerase chain reaction and Western blots were used to investigate the expression level of CLN5 in hemangioblastomas. Triple immunofluorescent microscopy was used to analyze the coexpression of vascular endothelial growth factor, vascular endothelial growth factor-R1, and placenta growth factor on microvessels of hemangioblastomas. Clinical and experimental data were correlated and analyzed by the one-way analysis of variance, Kruskal-Wallis test, and Spearman rank correlation test.

RESULTS:

In the control brain, the paracellular cleft between adjacent endothelial cells is sealed by continuous strands of tight junctions. In cystic hemangioblastomas, a significant paracellular cleft could be found between adjacent endothelial cells. Some endothelial cells were connected with adherens junction and no tight junction was found between them. Compared with the control brain, expression of CLN5 was decreased in cystic hemangioblastomas (P &lt; 0.05). Phosphorylated CLN5 was detected in most hemangioblastomas, but not in the control brain. Microvessels in hemangioblastomas showed a significant absence of astrocytic endfeet. Coexpression of vascular endothelial growth factor, vascular endothelial growth factor-R1, and placenta growth factor was detected in the endothelial cells. The Spearman rank correlation test showed a significant correlation between a greater degree of CLN5 expression and less morphological cystic formation in these patients studied (correlation coefficient = −0.520; P = 0.009).

CONCLUSION:

The continuity of tight junctions of the BBB is interrupted in human cerebellar hemangioblastomas. Significant absence of astrocytic endfeet and tight junctions can be found in microvessels of hemangioblastomas, which may lead to the breakdown of the BBB in these tumors. These findings suggest that the absence of tight junctions might play a role in cyst formation of hemangioblastomas.

Parenchymal Perianeurysmal Cyst in the Brain: Case Report

OBJECTIVE AND IMPORTANCE:

Parenchymal perianeurysmal cysts are rare, and only seven cases have been reported. We present a case report with a 30 month follow-up on this topic. The possible etiopathogenetic mechanisms of cyst formation are discussed.

CLINICAL PRESENTATION:

A 54-year-old man with a 5–month history of headache and a computed tomography scan showing a giant parenchymal cyst located in the right temporal lobe with a mural enhanced nodule was admitted to our neurosurgical department with the diagnosis of cystic brain tumor. Magnetic resonance imaging followed by digital subtraction angiography identified the enhancing nodule as a large right middle cerebral artery aneurysm.

INTERVENTION:

Surgical treatment was performed; the aneurysm was clipped and the cyst evacuated. Postoperative digital subtraction angiography confirmed the clipping of the aneurysm at the neck. Serial magnetic resonance imaging controls showed the permanent collapse of the cyst.

CONCLUSION:

Parenchymal perianeurysmal cysts are rare. In the presence of parenchymal cysts neighboring main vessels, the possibility of a perianeurysmal cyst should be considered. In regard to the etiopathogenetic mechanisms responsible for the cyst development, the action of multiple coexisting factors seems to be the most applicable.

Use of magnetic resonance imaging to assess blood-brain/blood-glioma barrier opening during conformal radiotherapy

PURPOSE

For chemotherapy to act synergistically and safely with radiation against high-grade gliomas, drugs must pass the endothelial junctions of the blood-tumor barrier (BTB) to reach all tumor cells, and should not pass the blood-brain barrier (BBB) to cause toxicity to normal brain. The objective of this study was to assess BBB/BTB status using magnetic resonance imaging (MRI) during a course of radiotherapy of high-grade gliomas.

PATIENTS AND METHODS

Sixteen patients with grade 3 or 4 supratentorial malignant glioma receiving conformal radiotherapy (RT) underwent contrast-enhanced MRI before, during, and after completion of RT. A gadolinium diethylenetriaminepentaacetic acid (Gd-DTPA) uptake index was analyzed with respect to the tumor and RT dose received.

RESULTS

In the nonenhanced tumor region, contrast uptake increased significantly after the receipt of approximately 10 Gy (P < .01), and reached a maximum after the receipt of approximately 30 Gy. In the initially contrast-enhanced tumor region, contrast uptake decreased over the course of RT and became significant after completion of RT in patients without progressive disease. The healthy brain showed only nonsignificant changes during and after irradiation.

CONCLUSION

Contrast MRI reveals increases in Gd-DTPA uptake in the initially nonenhanced tumor region but not in the remaining brain during the course of RT, suggesting opening of the BTB. This finding suggests that the effect of conformal radiation is more selective on the BTB than the BBB, and there may be a window extending from 1 week after the initiation of radiotherapy to 1 month after the completion of treatment during which a pharmaceutical agent has maximum access to high-grade gliomas.

Edema is a precursor to central nervous system peritumoral cyst formation

Despite the common occurrence and frequent clinical effects of peritumoral cysts in the central nervous system (CNS), the mechanism underlying their development and evolution is not understood. Because they commonly produce peritumoral cysts and because serial magnetic resonance imaging (MRI) is obtained in von Hippel-Lindau disease patients, hemangioblastomas provide an opportunity to examine the pathophysiology of CNS peritumoral cyst formation. Serial MRI was correlated with the clinical findings in 16 von Hippel-Lindau disease patients with 22 CNS hemangioblastomas (11 spinal cord; 11 cerebellar) that were associated with the appearance and evolution of peritumoral cysts. Hemangioblastoma-associated cyst wall histomorphological analysis was performed on postmortem tissues from three von Hippel-Lindau disease patients (not in the clinical series). Comparative proteomic profiling was performed on peritumoral cyst fluid and serum. Vascular endothelial growth factor levels were determined in peritumoral cysts. MRI clearly showed peritumoral edema that developed and slowly and progressively evolved into enlarging hemangioblastoma-associated cysts in all tumors (mean follow-up, 130 +/- 38 months; mean +/- standard deviation). Postcontrast MRI demonstrated convective leakage of gadolinium into cysts. Mean time required for edema to evolve into a cyst was 36 +/- 23 months (range, 8-72 months). Thirteen (59%) hemangioblastoma-cysts became symptomatic (mean time to symptom formation after cyst development, 35 +/- 32 months; range, 3-102 months) and required resection. Protein profiles of cyst fluid and serum were similar. Mean cyst fluid vascular endothelial growth factor concentration was 1.5 ng/ml (range, 0-5.4 ng/ml). Histology of the cyst walls was consistent with reactive gliosis. CNS peritumoral cyst formation is initiated by increased tumor vascular permeability, increased interstitial pressure in the tumor, and plasma extravasation with convective distribution into the surrounding tissue. When the delivery of plasma from the tumor exceeds the capacity of the surrounding tissue to absorb the extravasated fluid, edema (with its associated increased interstitial pressure) and subsequent cyst formation occur.

Angiostatin-induced inhibition of endothelial cell proliferation/apoptosis is associated with the down-regulation of cell cycle regulatory protein cdk5

Endothelial cells (ECs) are quiescent in normal blood vessels, but undergo rapid bursts of proliferation after vascular injury, hypoxia or induced by powerful angiogenic cytokines like fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF). Deregulated proliferation of ECs facilitates angiogenic processes and promotes tumor growth. In dividing cells, cell cycle-associated protein kinases, which are referred as cyclin-dependent kinases (cdks), regulate proliferation, differentiation, senescence, and apoptosis. Cyclin-dependent kinase-5 (cdk5) is expressed in neuronal cells and plays an important role in neurite outgrowth, of neuronal migration and neurogenesis, its functions in non-neuronal cells are unclear. Here, we show for the first time that the cdk5 is expressed at high levels in proliferating bovine aortic endothelial (BAE) cells, by contrast insignificant low levels of cdk5 expression in quiescent BAE cells. In addition, bFGF up-regulates cdk5 expression in a dose-dependent fashion. Interestingly, temporal expression data suggests that cdk5 expression is very low between 24-48 h, but high level of cdk5 expression was detected during 60-72 h. This later time corresponds to the time of completion of one cell cycle (doubling of cell population) of BAE cell culture. Angiostatin (AS), a powerful inhibitor of angiogenesis inhibits ECs proliferation in dose-dependent manner with concomitant down-regulation of cdk5 expression. The role of cdk5 in ECs, proliferation and apoptosis was confirmed by selective inhibition of cdk5 expression by the purine derivative roscovitine, which inhibits bFGF-stimulated BAE cells proliferation and induces apoptosis in dose-specific manner. By contrast, the roscovitine analog olomoucine, which is a specific inhibitor of cdk4, but not of cdk5 failed to affect ECs proliferation and apoptosis. These data suggest for the first time that neuron specific protein cdk5 may have significant role in the regulation of ECs proliferation, apoptosis, and angiogenesis and extends beyond its role in neurogenesis.

Angiogenesis in intracranial meningiomas: immunohistochemical and molecular study

Much of the morbidity of intracranial meningiomas is related to the degree of tumour vascularity and the extent of peritumoural vasogenic oedema. Several studies have shown that vascular endothelial growth factor (VEGF) is up-regulated in meningiomas, although its relationship with tumour vasculature is still unclear. In order to better understand the angiogenic assessment of intracranial meningiomas, we analysed its vascular pattern, both as number and as morphologic configuration of microvessels. Moreover, we investigated the mRNA-VEGF expression, relating this expression to vascular pattern. A total of 40 intracranial meningiomas, classified as benign (31 cases), atypical (7 cases), and anaplastic (2 cases) were analysed. RT-PCR analyses of mRNA-VEGF and competitive-PCR were performed. VEGF expression and microvessel density (MVD) were also immunohistochemically investigated. Grade II-III meningiomas showed numerous small microvessels (mean: 34), while the majority of Grade I showed few larger vessels (mean: 13.09) (P = 0.000003). A microvessel pattern overlapping into atypical subtype was found in eignt of the 31 (25.8%) Grade I meningiomas. A significant association was found between grading and vascular pattern (P = 0.0002), as well as between the MVD and the immunohistochemical expression of VEGF (P = 0.0005). The expression of mRNA agreed with the immunohistochemical expression of the protein (P < 0.0001). A total of 39 cases expressed the 121 VEGF isoform and, among these, 28 cases also expressed the 165 isoform. Only 9 cases expressed both isoforms 165 and 189. Grade II and III meningiomas showed a preponderant expression of soluble isoforms (121 and 165). These results prompt us to speculate that the microvessel pattern could underlie a higher metabolic demand, probably due to a rapid growth with a consequent worse clinical behaviour of the tumour. In this sense, the vascular pattern may be used as a prognostic factor, in order to mostly focus attention on those Grade I meningiomas which have a higher likelihood of either recurrence or development of perilesional oedema. The pattern of vasculature itself seems to be dependent on the types of VEGF isoforms: the Grade II-III meningiomas (that presented numerous microvessels) expressed the soluble isoforms 121 and 165, while the isoform 189 was more frequently detected in Grade I meningiomas.

Meningiomas: Updating Basic Science, Management, and Outcome

BACKGROUND

Meningiomas are biologically complex and clinically and surgically challenging. These features, combined with the rewarding potential for cure, make them of great interest to neurologists, neurosurgeons, and neuroscientists alike.

REVIEW SUMMARY

Initially, we review the clinical context of meningiomas, particularly recent changes in histopathological classification, diagnosis, and neuroimaging. Secondly, the underlying basic science as it has evolved over the last decades is summarized. The status of areas recently of intense interest, such as steroid hormone receptors and oncogenic viruses is described. Additionally, emerging areas of great promise, such as cytogenetics and molecular biology are presented. Lastly, we describe recent advances in management. In particular, skull-base surgery, image-guided surgery, and advances in radiotherapy are emphasized. The possible impact of basic research on management and outcome is also outlined.

CONCLUSIONS

Although usually benign and amenable to cure, meningiomas still present significant diagnostic and treatment challenges. Advances in basic science, surgery, and adjuvant therapy are widening the potential for safe, effective, evidence-based management leading to even better outcomes

Improving anti-angiogenic therapy via selective delivery of cationic liposomes to tumour vasculature

In the past three decades, two very important findings regarding tumour vasculature have been made. Firstly, it has been known a solid tumour has to establish an adequate blood supply to grow beyond a critical mass. Secondly, it has been proven that the tumour vasculature is relatively more aberrant, dynamic and permeable than healthy host tissue. This review discusses the potential of delivering therapeutic nucleic acids to tumour vasculature using cationic liposomes, vehicles recently demonstrated to be selectively delivered to tumour vasculature.

Angiogenesis in transgenic models of multistep angiogenesis

The histopathology and the epidemiology of human cancers, as well as studies of animal models of tumorigenesis, have led to a widely accepted notion that multiple genetic and epigenetic changes have to accumulate for progression to malignancy. Formation of new blood vessels (tumor angiogenesis) has been recognized, in addition to proliferative capabilities and ability to down-modulate cell death (apoptosis), as essential for the progressive growth and expansion of solid tumors. Mice overexpressing activated forms of oncogenes or carrying targeted mutations in tumor suppressor genes have proven extremely useful for linking the function of these genes with specific tumor features such as continuous proliferation, escape from apoptosis, invasion and neo-angiogenesis. The interbreeding of these mice allows for studying the extent of cooperativity between different genetic lesions in disease progression, leading to a greater understanding of multi-stage nature of tumorigenesis.

Models for Angiogenesis in Gliomas

During the last decades a lot of attention has been focussed on mechanisms of glioma vascularization, particularly in terms of investigating vascular growth factors and receptors. Recently, these efforts resulted in various approaches for antiangiogenic treatment strategies using in vitro cell culture systems as well as experimental orthotopic and non-orthotopic brain tumors. These basic science and preclinical trials need an assortment of models, which should allow investigating a variety of questions. Several objectives concerning basic endothelial cell (EC) characteristics can adequately be studied in vitro using EC monolayer assays. Three-dimensional spheroid techniques respect the more complex cell-cell and cell-environment interplay within a 3-dimensional culture. Recent advances in molecular genetic techniques offer a wide access to the genome of EC. Using these micro array or chip methods differences between micro- and macromolecular EC as well as variations within the gene pool of different organ specific EC can be assessed. To optimize the imitation of the crucial interaction of human gliomas with host endothelial cells, immunological cells and extracellular matrix, animal models are mandatory. An essential rule is to utilize an orthotopic model, since tumor-host-interaction is organ specific. To avoid alloimmunogenic responses, it is desirable to use weak or non-immunogenic glioma grafts, which is best accomplished in a syngeneic model. However, since rat gliomas poorly resemble human glioma growth patterns, human glioma xenografting into immunocompromized animals should be considered. In vivo-monitoring techniques like videoscopy via a cranial window or magnetic resonance imaging (MRI) allow for functional studies and improve the validity of the model employed. Finally, it is essentially to recognize the limitations of each model considered and to select that model which seems to be most appropriate for the objectives to be investigated.

Angiogenic factors in the central nervous system

The past decade has seen considerable advances in the understanding of angiogenesis. Blood vessel development and growth in the central nervous system are tightly controlled processes that are regulated by angiogenic factors. Angiogenic factors have been implicated in the pathogenesis of a wide variety of disorders, including primary and metastatic brain tumors, aneurysms, arteriovenous malformations, and cavernous malformations. The potential clinical applications of angiogenesis research include inhibition of angiogenesis to control brain tumors and therapeutic angiogenesis to promote collateral blood vessel formation among patients at risk of ischemia. This article summarizes the processes of blood vessel formation in the brain, examines the angiogenic factors that are prominent in the central nervous system, reviews the clinical use of angiogenesis inhibitors, and identifies areas for future investigation.

Influence of VEGF-R2 inhibition on MMP secretion and motility of microvascular human cerebral endothelial cells (HCEC)

Neovascularization and invasion are key features of malignant gliomas. Matrix metalloproteinases (MMPs) are supposed to play a major role mediating these processes. To analyze the expression patterns of MMPs in microvascular human cerebral endothelial cells (HCEC), we isolated endothelial cells from normal human brain microvessels. Characterization of cellular origin was performed by immunostaining, using the endothelial cell markers Ulex europaeus Agglutinin-1, von-Willebrand-Factor and Glucose-transporter-1. Contamination by other cell types was tracked by immunohistochemistry for GFAP (astrocytes), ASM (pericytes) and CD68 (macrophages). Secretion of MMPs was evaluated by ELISA and zymography. To determine whether HCEC show any difference in MMP expression compared to endothelial cells of other origin we analyzed human umbilical vein endothelial cells (HUVEC). HCEC show a decrease of MMP-3 and MMP-2 protein when treated with SU5416, a VEGF-R2 (KDR/flk-1) inhibitor, whereas MMP expression remained unchanged in HUVEC. To determine whether these findings show any effect in the motility of these cells we used a three-dimensional co-culture assay of avascular glioblastoma spheroids with primary HCEC spheroids. Untreated controls showed invasion of both cell populations into each other whereas treatment of the co-cultures with SU5416 resulted in complete inhibition of endothelial cell invasion hence indicating that flk-1 related motility of endothelial cells is critically involved in this process and can be studied with this assay. The results of different effects of anti-angiogenic treatment on proteolytic properties of two endothelial cell populations suggest that neovascularization of human brain tumors in vitro is dependent on the surrounding endothelial cell type and should therefore be studied with organ-specific human microvascular cerebral endothelial cells.

Intracavitary VEGF, bFGF, IL-8, IL-12 levels in primary and recurrent malignant glioma

Intracavitary levels of VEGF, bFGF, IL-8 and IL- 12 were evaluated by ELISA in 45 patients, 7 with recurrent anaplastic astrocytoma (rAA), 12 with glioblastoma (GBM) and 26 with recurrent glioblastoma (rGBM). In 25 patients plasma levels of the molecules were also quantitated. Twenty-three healthy controls were also studied for plasma concentrations of the same molecules. Plasma levels of VEGF (mean 33.89 +/- 6.71 pg/ml) and bFGF (mean 11.1 +/- 3.24 pg/ml) were higher in patients than in controls (mean 16.78 +/- 3.7 pg/ml for VEGF, mean 0.21 +/- 0.09 pg/ml for bFGF) (p = 0.04 and p = 0.001, respectively) while plasma IL-12 levels were lower (mean 45.6 +/- 1.5 pg/ml in patients, mean 79.7 +/- 1.3 pg/ml in controls) (p = 0.009). Intracavitary VEGF levels were 5-53.307 fold higher (mean 90,900 +/- 24,789 pg/ml) than in the corresponding plasma. Also IL-8 concentrations were higher in intracavitary fluid (mean 6,349.76 +/- 1,460.93 pg/ml) than in plasma (mean 43.44 +/- 24.82 pg/ml). Maximum VEGF levels were found in tumor fluid of recurrent glioblastoma patients (mean 147,678 +/- 39.903 pg/ml), intermediate levels in glioblastoma patients (mean 20,322 +/- 11,892 pg/ml) and lower levels in rAA patients (mean 9,111 +/- 5,789 pg/ml). The data also suggest that higher intracavitary levels of VEGF and IL-8, and lower IL-12 levels, may be correlated with shorter adjunctive survival times, but more data will need to be collected to establish this correlation clearly.

Detection of vascular endothelial growth factor/ vascular permeability factor in periapical lesions

Vascular endothelial growth factor (VEGF), also known as vascular permeability factor (VPF), is a multifunctional cytokine. It is overexpressed in several conditions, which are characterized by vascular hyperpermeability and angiogenesis. In this investigation, we have evaluated the possibility that VEGF/VPF could be expressed in periapical lesions. We studied 17 periapical granulomas and 6 periapical cysts by immunohistochemistry. An immunopositive reaction for VEGF/VPF was observed in all 23 periapical lesions; however, the intensity of immunostaining by anti-VEGF antibody varied according to histopathological findings. In periapical granulomas without epithelium, almost all of the inflammatory cells were immunoreactive to anti-VEGF/VIP antibody. In periapical granulomas, which had rests of Malassez in them, some inflammatory cells were stained. On the other hand, epithelial cells always were stained by VEGF/VPF antibody, both in periapical lesions with epithelium and in radicular cysts. This study demonstrated that periapical lesions express VEGF/VPF, although with some differences in cell immunolabeling, which correlated to the lesions' stages of development. Initially, VEGF/VPF would assure angiogenesis and vascular hyperpermeability, resulting in accumulation of inflammatory cells, later it could be involved in cyst fluid accumulation. We hypothesize, therefore, that VEGF/VPF expression plays an important role in the pathogenesis of periapical granulomas and enlargement of radicular cysts by several mechanisms.

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.

A planned combined stereotactic approach for cystic intracranial tumors

✓ Cyst-associated tumors are classified as cysts with neoplastic mural nodules and intratumoral cysts. The solid component of many of these tumors may be appropriate for gamma knife radiosurgery (GKS). At present there is no systematic protocol for GKS treatment of patients harboring tumors with a cystic component. The purpose of this paper is to suggest such a program.

Two cases are presented. One patient had a hemangioblastoma with a cyst and a mural nodule. The second patient had a craniopharyngioma with one large and two small intratumoral cysts. The course in both cases has been satisfactory in the short term. Although the 1-year follow-up period, however, does not provide a basis for determining the correct overall management of such tumors, the treatment strategy does illustrate a program for the management of tumors with associated cysts.

Cysts with tumor nodules in their walls should first be treated with GKS followed by aspiration of the cyst contents, unless special circumstances make this unsuitable. This strategy enables treatment planning to take advantage of the natural barrier a cyst may place between a tumor and important surrounding structures.

Intratumoral cysts may be aspirated and then treated with GKS, with every attempt made to cover the entire target volume including any residual cyst with the prescription dose. This form of treatment requires very careful follow up.

It is probable that in some cases reaccumulation of cyst fluid may require the insertion of an Ommaya reservoir for repeated aspiration or the installation of cytotoxic agents such as bleomycin. This form of treatment is much less traumatic than surgery and does not hinder the performance of subsequent surgery, should this become necessary.

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.

Angiogenic and astroglial responses to vascular endothelial growth factor administration in adult rat brain

The effects of exogenous vascular endothelial growth factor (VEGF) on angiogenesis, blood-brain barrier permeability and astroglial proliferation in the adult rat CNS in situ were investigated. Recombinant human VEGF(165) (25 or 50 ng/ml) was delivered for up to 1 week using either intracerebral osmotic minipumps or less traumatic subdural gelatin sponge placement. By 3 days, VEGF delivery caused significantly increased cerebral angiogenesis (25 ng/ml was most effective) in both experimental models when compared to saline controls; VEGF infusion resulted in a 100% increase in an index of vascular proliferation, and gelatin sponge delivery produced a 65% increase. The blood-brain barrier hallmark endothelial glucose transporter-1 was not present in nascent vascular sprouts. Infusion of VEGF produced extensive protein leakage that persisted after saline-induced permeability was mostly resolved, while gelatin sponge administration caused milder barrier dysfunction. Administration of the angiogenic factor had unexpected proliferative effects on astroglia in both models, resulting in an 80-85% increase in mitotically active astroglia when compared to controls. Immunohistochemical results and semi-quantitative reverse transcriptase-polymerase chain reaction indicated that the VEGF receptors flk-1 and flt-1 were up-regulated in response to the infusion trauma; flt-1 was localized to reactive astroglia, while flk-1 was expressed in vascular endothelium but predominantly in neuronal somata and processes adjacent to the delivery site. mRNA for the VEGF(121), VEGF(165) and VEGF(188) isoforms was also increased after delivery of the recombinant protein. These data show that VEGF application has substantial proliferative effects on CNS endothelium and astroglia and causes up-regulation of its own message. Flt-1 and flk-1 receptor mRNAs and proteins are up-regulated in both vascular and non-vascular cell types following infusion trauma. From these results we suggest that administered VEGF has heretofore unanticipated pleiotrophic effects in the adult CNS.

Acidic extracellular pH induces vascular endothelial growth factor (VEGF) in human glioblastoma cells via ERK1/2 MAPK signaling pathway: mechanism of low pH-induced VEGF

Overexpression of vascular endothelial growth factor (VEGF) is associated with disease progression in human glioblastomas. We recently showed that VEGF promoter activity is inversely correlated with tumor extracellular pH (pH(o)) in vivo in the human glioma (U87 MG) xenografts. Here we show that substitution of the neutral culture medium (pH 7.3) with acidic pH medium (pH 6.6) up-regulates VEGF mRNA and protein production in human glioblastoma cells as reflected by Northern blot analysis and enzyme-linked immunosorbent assay. Functional analysis of the VEGF promoter reveals that the sequence between -961 bp and -683 bp upstream of the transcription start site is responsible for the transcriptional activation of the VEGF gene by acidic pH. This region contains the binding site for AP-1. Consequently, AP-1 luciferase reporter gene was activated by acidic pH. Gel-shift analysis confirmed that AP-1 DNA binding activity is induced under acidic pH. While investigating the upstream signaling pathways, we found that ERK1/2 MAPK is activated and translocates to the nucleus to activate Elk-1, and inhibition of the activation of ERK by specific inhibitors of MEK1 blocks the up-regulation of VEGF by low pH. Dominant negative forms of Ras and Raf abolished the activation of VEGF promoter by acidic pH. These results show that acidic pH activates Ras and the ERK1/2 MAPK pathway to enhance VEGF transcription via AP-1, leading to increased VEGF production.