Vascular endothelial growth factor (VEGF) in astrocytic gliomas--a prognostic factor?

Assessment of Serum Hypoxia Biomarkers Pre- and Post-radiotherapy in Patients with Brain Tumors

Hypoxia is a prevalent hallmark of many malignant neoplasms. The aim was to assess the serum hypoxia biomarkers HIF-1α, VEGF, osteopontin, erythropoietin, caveolin-1, GLUT-1, and LDH pre- and post-radiotherapy in patients with brain tumors. The study was conducted on 120 subjects were divided into two groups: group I: 40 healthy volunteers as control group. Group II: 80 brain tumor patients were subdivided into glioblastoma subgroup: 40 glioblastoma patients, meningioma subgroup: 40 malignant meningioma patients. Two venous blood samples were collected from every patient prior to and following RT and one sample from controls. Biomarkers were assayed by ELISA. In glioblastoma subgroup, HIF-1α, VEGF, and LDH were significantly increased after RT. On the contrary, these biomarkers were significantly decreased after RT in malignant meningioma subgroup. Osteopontin was significantly increased after RT in both subgroups. Regarding erythropoietin, it was significantly decreased in both subgroups when compared to before RT. Caveolin-1 showed a significant increase in glioblastoma subgroup after RT comparing to before RT. GLUT-1 was significantly increased after RT in both subgroups comparing to before RT. Association of significant elevation of hypoxia biomarkers either pre- or post-RT with aggressive tumor such as glioblastoma indicates that, they are markers of malignancy and may have a role in tumor development and progression.

Long Term Outcome and Histologic Findings of a Retinal Astrocytic Hamartoma Treated with Intravitreal Injection of Anti-VEGF: A Case Report

Background

To our knowledge, this is the first report to describe the histologic changes of a retinal astrocytic hamartoma (RAH) in a patient with tuberous sclerosis complex (TSC) treated with antivascular endothelial growth factor (anti-VEGF), as well as the longest anti-VEGF treatment that such a patient has received (3 years). Case Presentation. We present a case of a 20-year-old female with TSC who developed progressive growth of a papillary astrocytic hamartoma that caused significant retinal edema, vitreous hemorrhage, and neovascular glaucoma. The patient was initially treated with 25 intravitreal anti-VEGF injections about every 1-3 months, but eventually developed a blind painful eye from neovascular glaucoma. Histopathologic evaluation of the enucleated globe showed a peculiar difference of the tumor according to its topography, with features reminiscent of pilocytic astrocytoma at the optic nerve head and features reminiscent of subependymal giant cell astrocytoma at the retrolaminar optic nerve. We hypothesize that these changes occurred as a secondary effect of the anti-VEGF treatment.

Conclusions

Anti-VEGF agents may decrease the ophthalmologic complications of RAH. We recommend that this treatment should be started early and continued for a protracted time at regular and frequent intervals. Moreover, a combination of therapies might prove to be superior to monotherapy and should therefore be considered in aggressive retinal astrocytic hamartomas.

Correlation of dynamic contrast-enhanced MRI derived volume transfer constant with histological angiogenic markers in high-grade gliomas

INTRODUCTION

To ascertain if the volume transfer constant (Ktrans ) derived from T1 dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) correlates with the immunohistological markers of angiogenesis in high-grade gliomas.

METHODS

Fifty-one image-guided biopsy specimens in 34 patients with newly presenting high-grade gliomas (grade III = 16; grade IV = 18) underwent preoperative imaging (conventional imaging and T1 DCE-MRI). We correlated vascular endothelial growth factor (VEGF) expression and the microvessel density (MVD) of MRI-guided biopsy specimens with the corresponding DCE-derived Ktrans . Histological sections were stained with VEGF and CD34, and examined under light microscopy. These histological and molecular markers of angiogenesis were correlated with the Ktrans of the region of interest corresponding to the biopsy specimen.

RESULTS

The Ktrans showed a significant positive correlation with VEGF expression (ρ = 0.582, P = 0.001) but not with MVD stained with CD34 antibody (ρ = 0.328, P = 0.072).

CONCLUSION

The Ktrans derived from DCE-MRI can reflect the VEGF expression of high-grade gliomas but not the MVD.

Vascular Endothelial Growth Factor, Irradiation, and Axitinib Have Diverse Effects on Motility and Proliferation of Glioblastoma Multiforme Cells

Glioblastoma multiforme (GBM) is the most common primary brain tumor. It is highly aggressive with an unfavorable prognosis for the patients despite therapies including surgery, irradiation, and chemotherapy. One important characteristic of highly vascularized GBM is the strong expression of vascular endothelial growth factor (VEGF). VEGF has become a new target in the treatment of GBM, and targeted therapies such as the VEGF-receptor blocker axitinib are in clinical trials. Most studies focus on VEGF-induced angiogenesis, but only very few investigations analyze autocrine or paracrine effects of VEGF on the tumor cells. In this study, we examined the impact of VEGF, irradiation, and axitinib on cell proliferation and cell motility in human GBM cell lines U-251 and U-373. VEGF receptor 2 was shown to be expressed within both cell lines by using PCR and immunochemistry. Moreover, we performed 24-h videography to analyze motility, and a viability assay for cell proliferation. We observed increasing effects of VEGF and irradiation on cell motility in both cell lines, as well as strong inhibiting effects on cellular motility by VEGF-receptor blockade using axitinib. Moreover, axitinib diminished irradiation induced accelerating effects. While VEGF stimulation or irradiation did not affect cell proliferation, axitinib significantly decreased cell proliferation in both cell lines. Therefore, the impairment of VEGF signaling might have a crucial role in the treatment of GBM.

The Use of Gene Therapy in Cancer Research and Treatment

Gene therapy involves identifying a gene of interest and then manipulating the expression of this gene through a variety of techniques. Here we specifically address gene therapy's role in cancer research. This paper will encompass thoroughly investigated techniques such as cancer vaccines and suicide gene therapy and the latest advancements in and applications of these techniques. It will also cover newer techniques such as Antisense Oligonucleotides and small interfering RNAs and how these technologies are being developed and used. The use of gene therapy continues to expand in cancer research and has an integral role in the advancement of cancer treatment.

Complete diagnostics and clinical approach for a female patient with unusual glioblastoma: A case study

The present study reports a case of a 44-year-old female patient with a large frontal lobe tumor who underwent surgery using a modern navigation system SonoWand that combines the advantages of a non-frame navigation system with intraoperative real-time ultrasound imaging. The right frontal lobe tumor consisted of two morphologically different sections. A diffuse astrocytoma grade II and a glioblastoma grade IV were identified. These tumors were relatively substantially separated. A 17 p deletion, including TP53, was detected in a diffuse astrocytoma but not in a glioblastoma. EGFR and MDM2 amplifications were detected only in a glioblastoma. Detection of these amplifications is typical for primary glioblastomas. These findings support our assumption of two independent tumors. The KRAS, BRAF and EGFR gene mutations were also detected in a glioblastoma. Such an accumulation of molecular mutations is rare in one tumor. Following oncological treatment the patient was cared for in the oncological center and survived for 15 months after the surgery without any signs of a disease. This is an unusual case, and to the best of our knowledge, is not frequently published in literature.

Mitotic Activity in Glioblastoma Correlates with Estimated Extravascular Extracellular Space Derived from Dynamic Contrast-Enhanced MR Imaging

BACKGROUND AND PURPOSE

A number of parameters derived from dynamic contrast-enhanced MR imaging and separate histologic features have been identified as potential prognosticators in high-grade glioma. This study evaluated the relationships between dynamic contrast-enhanced MRI-derived parameters and histologic features in glioblastoma multiforme.

MATERIALS AND METHODS

Twenty-eight patients with newly presenting glioblastoma multiforme underwent preoperative imaging (conventional imaging and T1 dynamic contrast-enhanced MRI). Parametric maps of the initial area under the contrast agent concentration curve, contrast transfer coefficient, estimate of volume of the extravascular extracellular space, and estimate of blood plasma volume were generated, and the enhancing fraction was calculated. Surgical specimens were used to assess subtype and were graded (World Health Organization classification system) and were assessed for necrosis, cell density, cellular atypia, mitotic activity, and overall vascularity scores. Quantitative assessment of endothelial surface area, vascular surface area, and a vascular profile count were made by using CD34 immunostaining. The relationships between MR imaging parameters and histopathologic features were examined.

RESULTS

High values of contrast transfer coefficient were associated with the presence of frank necrosis (P = .005). High values of the estimate of volume of the extravascular extracellular space were associated with a fibrillary histologic pattern (P < .01) and with increased mitotic activity (P < .05). No relationship was found between mitotic activity and histologic pattern, suggesting that the correlation between the estimate of volume of the extravascular extracellular space and mitotic activity was independent of the histologic pattern.

CONCLUSIONS

A correlation between the estimate of volume of the extravascular extracellular space and mitotic activity is reported. Further work is warranted to establish how dynamic contrast-enhanced MRI parameters relate to more quantitative histologic measurements, including markers of proliferation and measures of vascular endothelial growth factor expression.

Improved Treatment Efficacy of Antiangiogenic Therapy when Combined with Picornavirus Vaccination in the GL261 Glioma Model

The addition of antiangiogenic therapy to the standard-of-care treatment regimen for recurring glioblastoma has provided some clinical benefits while also delineating numerous caveats, prompting evaluation of the elicited alterations to the tumor microenvironment. Of critical importance, given the steadily increasing incorporation of immunotherapeutic approaches clinically, is an enhanced understanding of the interplay between angiogenic and immune response pathways within tumors. In the present study, the GL261 glioma mouse model was used to determine the effects of antiangiogenic treatment in an immune-competent host. Following weekly systemic administration of aflibercept, an inhibitor of vascular endothelial growth factor, tumor volume was assessed by magnetic resonance imaging and changes to the tumor microenvironment were determined. Treatment with aflibercept resulted in reduced tumor burden and increased survival compared with controls. Additionally, decreased vascular permeability and preservation of the integrity of tight junction proteins were observed. Treated tumors also displayed hallmarks of anti-angiogenic evasion, including marked upregulation of vascular endothelial growth factor expression and increased tumor invasiveness. Aflibercept was then administered in combination with a picornavirus-based antitumor vaccine and tumor progression was evaluated. This combination therapy significantly delayed tumor progression and extended survival beyond that observed for either therapy alone. As such, this work demonstrates the efficacy of combined antiangiogenic and immunotherapy approaches for treating established gliomas and provides a foundation for further evaluation of the effects of antiangiogenic therapy in the context of endogenous or vaccine-induced inflammatory responses.

Hypoxia suppresses cylindromatosis (CYLD) expression to promote inflammation in glioblastoma: possible link to acquired resistance to anti-VEGF therapy

Cylindromatosis (CYLD) is a tumor suppressor that regulates signaling pathways by acting as a deubiquitinating enzyme. CYLDdown-regulation occurred in several malignancies, with tumor-promoting effects. Although we found loss of CYLD expression in hypoxic regions of human glioblastoma multiforme (GBM), the most aggressive brain tumor, biological roles of CYLD in GBM remain unknown. This study aimed to determine the biological significance of CYLD down-regulation to GBM progression and therapy. CYLD mRNA transcription was dramatically down-regulated in hypoxic GBM cells, consistent with our clinical observations of human GBM tissues. Hypoxia enhanced both basal and tumor necrosis factor-α-induced expression of various proinflammatory cytokines, whereas CYLD overexpression strongly counteracted these responses. In addition, chronic anti-angiogenic therapy with bevacizumab, an anti-vascular endothelial growth factor (VEGF) antibody, with enhanced hypoxia produced responses similar to these CYLD-regulated proinflammatory responses in a xenograft mouse model. Histologically, CYLD clearly prevented massive immune cell infiltration surrounding necrotic regions, and pseudopalisades appeared in bevacizumab-treated control tumors. Furthermore, CYLD overexpression, which had no impact on survival by itself, significantly improved the prosurvival effect of bevacizumab. These data suggest that CYLD down-regulation is crucial for hypoxia-mediated inflammation in GBM, which may affect the long-term efficacy of anti-VEGF therapy.

Treatment of glioblastoma in elderly patients

Although glioblastoma occurs mostly in elderly patients, there is a paucity of trials addressing patients older than 70 years of age. Age, by itself, constitutes an unfavorable prognostic factor, which is probably due to unpropitious genetic features, but also due to iatrogenic defeatism. However, many retrospective studies report a survival benefit achieved by aggressive surgical resection seeking gross total removal of contrast-enhancing tumor according to preoperative MRI. Combined radiochemotherapy with concomitant and adjuvant temozolomide has not been investigated in prospective trials. Numerous retrospective studies and a meta-analysis suggest benefit from combined treatment. Prospective randomized trials only evaluated either temozolomide or radiotherapy. Single-treatment hypofractionated radiotherapy performed superior to conventional fractionation. In patients with methylated MGMT promoter, first-line dose-dense temozolomide facilitates prolonged survival. However, there is no comparison with combined radiochemotherapy as the standard-of-care in adult patients. Comorbidity is more frequent in elderly patients, but does not correlate with preterm termination of temozolomide treatment. This review article compiles data proposing a straightforward glioblastoma treatment, irrespective of age.

Prognostic and predictive biomarkers in adult and pediatric gliomas: toward personalized treatment

It is increasingly clear that both adult and pediatric glial tumor entities represent collections of neoplastic lesions, each with individual pathological molecular events and treatment responses. In this review, we discuss the current prognostic biomarkers validated for clinical use or with future clinical validity for gliomas. Accurate prognostication is crucial for managing patients as treatments may be associated with high morbidity and the benefits of high risk interventions must be judged by the treating clinicians. We also review biomarkers with predictive validity, which may become clinically relevant with the development of targeted therapies for adult and pediatric gliomas.

Victory and defeat in the induction of a therapeutic response through vaccine therapy for human and canine brain tumors: a review of the state of the art

Anti-tumor immunotherapy using tumor lysate-based vaccines has made great advances over recent decades. Cancer vaccines aim to elicit adaptive immune responses through various pathways by providing tumor and tumor-associated antigens with an immune stimulant or adjuvant. These anti-tumor vaccines are therefore developed as personalized treatments. Utilizing tumors as a source of vaccine antigens in immunotherapy has demonstrated promising results with minimal toxicity. However, to date, researchers have failed to overcome the overpowering immune suppressive effects within the tumor microenvironment. Immune suppression occurs naturally via multiple mechanisms. These mechanisms serve an important homeostatic role restoring a normal tissue microenvironment following an inflammatory response. Due to these suppressive mechanisms and the inherent heterogeneity of tumors, it is imperative to then elicit and maintain a specific tumoricidal response if vaccine therapy or some other combination of reagents is chosen. In this review, we focus on the historical use of tumors as a source of antigens to elicit a tumoricidal response and the limitations encountered that prevent greater success in immunotherapy. We describe the advantages and disadvantages of various vaccines and their ineffectiveness due to tumor-induced immune suppression.

T11TS inhibits glioma angiogenesis by modulation of MMPs, TIMPs, with related integrin αv and TGF-β1 expressions

During glioma development, angiogenesis plays a crucial role in growth and vascularization of primary brain tumors. T11 target structure (T11TS), a bioactive molecule, has been documented as an anti-neoplastic agent in glioma-induced rats and also in human glioma in vitro. This novel molecule induces apoptosis of tumor cells by way of immune potentiation and impairs the glioma cell cycle, but its role in glioma angiogenesis has not been worked out in detail. Matrix metalloproteinases (MMPs) are enzymes promoting tumor angiogenesis by enzymatically remodeling the extracellular matrix and altering surface protein expression such as integrin αv and the matrix-bound proteins like TGF-β1. The present study was formulated to assess the efficacy of T11TS in the modulations of MMP-2 and -9 and their endogenous inhibitors (TIMP-1 and TIMP-2) as well as modulations of integrin αv and TGF-β1 in glioma-induced rats and also on the phenotypic markers of endothelial cells (CD31 and CD34). The parameters used were zymography, western blot, and flow cytometric analyses. It was observed that T11TS administration significantly downregulates the expression of matrix metalloproteinase-2 and -9 along with its ligand integrin αv and upregulates TIMP-1 and TIMP-2. In situ immunofluorescence and FACS results revealed that T11TS administration decreased the expression of the phenotypic markers (CD31/PECAM1, CD34), inhibiting the cell grip and also downregulating TGF-β1 expression (ELISA) from microglia cells in the glioma microenvironment. These results suggest that T11TS suppresses the expression of positive angiogenic growth factors and potentiates the expression of negative regulators in glioma-associated endothelial cells (ECs), resulting in an anti-angiogenic effect on glioma-induced angiogenesis.

Opportunities and challenges for successful use of bevacizumab in pediatrics

Bevacizumab (Avastin) has rapidly gained status as a broadly active agent for malignancies of several different histologies in adults. This activity has spawned a range of uses in pediatrics for both oncologic and non-oncologic indications. Early analyses indicate that pediatric cancers exhibit a spectrum of responses to bevacizumab that suggest its activity may be more limited than in adult oncology. Most exciting, is that for low-grade tumors that threaten vision and hearing, there is not only evidence for objective tumor response but for recovery of lost function as well. In addition to oncological indications, there is a range of uses for non-oncologic disease for which bevacizumab has clear activity. Finally, a number of mechanisms have been identified as contributing to bevacizumab resistance in cancer. Elucidating these mechanisms will guide the development of future clinical trials of bevacizumab in pediatric oncology.

Clinical trials of small molecule inhibitors in high-grade glioma

High-grade gliomas are rapidly progressing and generally fatal neoplasms of the brain. Chemotherapy has continued to provide only limited benefit for patients harboring these tumors. The recurrence of common mutations, combined with the similarities of many of the acquired capabilities and characteristics of solid tumors, suggest many common therapeutic targets. During the past few decades, an increased understanding of many of the cellular regulatory mechanisms associated with carcinogenesis has provided an opportunity for the development of pathway-specific small molecule targeted inhibitors (SMIs). This article reviews the use of SMIs in the treatment of high-grade glioma.

Genetic variations in VEGF and VEGFR2 and glioblastoma outcome

Vascular endothelial growth factor (VEGF) and its receptors (VEGFR) are central components in the development and progression of glioblastoma. To investigate if genetic variation in VEGF and VEGFR2 is associated with glioblastoma prognosis, we examined blood samples from 154 glioblastoma cases collected in Sweden and Denmark between 2000 and 2004. Seventeen tagging single nucleotide polymorphisms (SNPs) in VEGF and 27 in VEGFR2 were genotyped and analysed, covering 90% of the genetic variability within the genes. In VEGF, we found no SNPs associated with survival. In VEGFR2, we found two SNPs significantly associated to survival, namely rs2071559 and rs12502008. However, these results are likely to be false positives due to multiple testing and could not be confirmed in a separate dataset. Overall, this study provides little evidence that VEGF and VEGFR2 polymorphisms are important for glioblastoma survival.

Bevacizumab plus irinotecan in the treatment patients with progressive recurrent malignant brain tumours

MATERIAL AND METHODS

We retrospectively determined the efficacy and safety of a combination of bevacizumab and irinotecan in a consecutive series of 52 heavily pre-treated patients with recurrent high-grade brain tumours. Patients received bevacizumab (10 mg/kg) and irinotecan [340 mg/m(2) for those receiving enzyme-inducing antiepileptic drugs (EIAEDs) and 125 mg/m(2) for those not receiving EIAEDs] every 2 weeks. Fifty-two patients were included and 47 were evaluable for response.

RESULTS

Complete or partial response was observed in 25% of all cases (30% response in grade IV glioma and 15% in grade III glioma). Estimated median progression-free survival (PFS) for both grade IV and grade III glioma was 22 weeks. The 6-month PFS was 32% for all patients, 40% for grade IV glioma and 33% for grade III glioma. Estimated median overall survival was 30 weeks for all patients, 28 weeks for grade IV glioma and 32 weeks for grade III glioma. Four patients discontinued treatment because of unmanageable toxicity: cerebral haemorrhage, cardiac arrhythmia, intestinal perforation and diarrhoea, the latter resulting in death.

DISCUSSION

We conclude that the combination of bevacizumab and irinotecan shows acceptable safety and is a clinically relevant choice of therapy in heavily pre-treated patients with recurrent high-grade brain tumours.

Designer therapies for glioblastoma multiforme

Primary brain tumors account for less than 2% of all cancers in adults; however, they are often associated with neurologic morbidity and high mortality. Glioblastoma multiforme (GBM) has been a focus of new therapy development in neurooncology because it is the most common primary brain tumor in adults. Standard-of-care therapy for newly diagnosed GBM includes surgical resection, radiotherapy, and temozolomide, administered both during and after radiotherapy. However, most patients develop tumor recurrence or progression after this multimodality treatment. Repeat resection and stereotactic radiosurgery upon recurrence may improve outcome only in selected patients. Most salvage chemotherapies offer only palliation. Recent advances in our understanding of the molecular abnormalities of GBM have generated new therapeutic venues of molecularly targeted agents (designer drugs) against key components of cellular pathways critical for cancer initiation and maintenance. Such drugs may offer the potential advantage to increase therapeutic efficacy and decrease systemic toxicity compared with traditional cytotoxic agents. Nonetheless, first-generation targeted agents have failed to demonstrate survival benefits in unselected GBM patient populations. Several mechanisms of treatment failure of the first-generation designer drugs have been proposed, whereas new strategies have been developed to increase effectiveness of these agents. Here we will discuss the recent development and the strategies to optimize the effectiveness of designer therapy for GBM.

T allele for VEGF-460 gene polymorphism at 5'-untranslated region is associated with higher susceptibility of leiomyoma

Vascular endothelial growth factor (VEGF) is a regulator of angiogenesis and a mediator of sex steroid-induced cell growth and differentiation. We aimed to investigate if VEGF gene 5'-UTR -460 polymorphism could be used as markers of susceptibility in leiomyoma. Women were divided into two groups: (1) leiomyoma (n = 159); (2) nonleiomyoma groups (n = 131). VEGF gene -460 polymorphism were detected by polymerase chain reaction and BstUI restriction enzyme analysis. Genotypes and allelic frequencies between both groups were compared. We noted that the proportions of different VEGF polymorphisms in both groups were significantly different. Proportions of cuttable (C) homozygote/heterozygote/uncuttable (T) homozygote for VEGF in both groups were: (1) 0/32/68% and (2) 0/63/37%. Higher percentage of T homozygote and T allele presented in the leiomyoma population. Proportions of C/T alleles in both groups were: (1) 16/84% and (2) 32/68%. We concluded that T homozygotes and T allele of VEGF gene -460 polymorphism are associated with higher risk of leiomyoma development. Heterozygotes and C allele are related with lower risk of leiomyoma formation. VEGF gene polymorphism likely contributes to the pathogenesis of leiomyoma.

Mechanisms of disease: temozolomide and glioblastoma--look to the future

Glioblastoma is both the most common and most aggressive primary brain tumor. Until recently, the standard of care involved maximal safe surgical resection followed by radiation therapy with or without nitrosourea-based chemotherapy. In 2005, the results of a large clinical trial examining the role of adjuvant chemotherapy in management of newly diagnosed glioblastoma were published. This study created a new standard of adjuvant treatment, using concurrent and sequential temozolomide in the initial therapy of glioblastoma. A companion tumor biology study identified the prognostic role of O(6)-methylguanine-DNA methyltransferase (MGMT) status in patients with newly diagnosed glioblastoma. Several preliminary studies have been initiated to address the issue of resistance and suppression of MGMT activity, and have used alternative temozolomide dosing schedules and O(6)-guanine mimetic agents as substrates for MGMT. In addition, recent studies have attempted to define mechanisms responsible for the apparent synergy between temozolomide and radiotherapy. Lastly, an increased understanding of the molecular biology of glioblastoma has provided new leads for the adjuvant treatment of this disease. This Review summarizes new developments in treatment of glioblastoma and speculates on possible future treatment strategies for managing this aggressive cancer.

Expression of vascular endothelial growth factor in tumors and plasma from dogs with primary intracranial neoplasms

OBJECTIVE

To quantitatively evaluate expression of vascular endothelial growth factor (VEGF) in intracranial tumors in dogs and determine whether relationships exist between circulating and intratumoral VEGF concentrations and tumor type and grade.

ANIMALS

27 dogs with primary intracranial neoplasms and 4 unaffected control dogs.

PROCEDURES

Plasma and brain tumor samples were obtained from each dog, and plasma and intratumoral concentrations of VEGF were measured by use of an ELISA.

RESULTS

Dogs with meningiomas (n = 11) were significantly older than dogs with oligodendrogliomas (7) or astrocytomas (9). Measurable VEGF was detected in all tumors, and a significant negative correlation between age and intratumoral VEGF concentration was detected. Age-adjusted comparisons identified significant differences in intratumoral VEGF concentrations among all tumor types; the highest VEGF concentrations were associated with astrocytomas. Within each tumor type, increasing tumor grade was significantly associated with increasing VEGF expression. Plasma VEGF concentrations were detectable in 9 of 27 dogs; the proportion of dogs with astrocytomas and a detectable circulating VEGF concentration (7/9 dogs) was significantly higher than the proportion of dogs with meningiomas (1/11 dogs) or oligodendrogliomas (1/7 dogs) with a detectable circulating VEGF concentration.

CONCLUSIONS AND CLINICAL RELEVANCE

Overexpression of VEGF appears common in canine astrocytomas, oligodendrogliomas, and meningiomas. In the neoplasms examined, intratumoral VEGF concentrations correlated well with tumor malignancy. The VEGF expression patterns paralleled those of analogous human tumors, providing evidence that dogs are a suitable species in which to study angiogenesis and intracranial neoplasia for human application.

Vascular endothelial growth factor in astroglioma stem cell biology and response to therapy

Malignant astrogliomas are among the most aggressive, highly vascular and infiltrating tumours bearing a dismal prognosis, mainly due to their resistance to current radiation treatment and chemotherapy. Efforts to identify and target the mechanisms that underlie astroglioma resistance have recently focused on candidate cancer stem cells, their biological properties, interplay with their local microenvironment or 'niche', and their role in tumour progression and recurrence. Both paracrine and autocrine regulation of astroglioma cell behaviour by locally produced cytokines such as the vascular endothelial growth factor (VEGF) are emerging as key factors that determine astroglioma cell fate. Here, we review these recent rapid advances in astroglioma research, with emphasis on the significance of VEGF in astroglioma stem-like cell biology. Furthermore, we highlight the unique DNA damage checkpoint properties of the CD133-marker-positive astroglioma stem-like cells, discuss their potential involvement in astroglioma radioresistance, and consider the implications of this new knowledge for designing combinatorial, more efficient therapeutic strategies.

Different angiogenic phenotypes in primary and secondary glioblastomas

Primary and secondary glioblastomas (pGBM, sGBM) are supposed to evolve through different genetic pathways, including EGF receptor and PDGF and its receptor and thus genes that are involved in tumor-induced angiogenesis. However, whether other angiogenic cytokines are also differentially expressed in these glioblastoma subtypes is not known so far, but this knowledge might be important to optimize an antiangiogenic therapy. Therefore, we studied the expression of several angiogenic cytokines, including VEGF-A, HGF, bFGF, PDGF-AB, PDGF-BB, G-CSF and GM-CSF in pGBMs and sGBMs as well as in gliomas WHO III, the precursor lesions of sGBMs. In tumor tissues, expression of all cytokines was observed albeit with marked differences concerning intensity and distribution pattern. Quantification of the cytokines in the supernatant of 30 tissue-corresponding glioma cultures revealed a predominant expression of VEGF-A in pGBMs and significantly higher expression levels of PDGF-AB in sGBMs. HGF and bFGF were determined in nearly all tumor cultures but with no GBM subtype or malignancy-related differences. Interestingly, GM-CSF and especially G-CSF were produced less frequently by tumor cells. However, GM-CSF secretion occurred together with an increased number of simultaneously secreted cytokines and correlated with a worse patient prognosis and may thus represent a more aggressive angiogenic phenotype. Finally, we confirmed an independent contribution of each tumor-derived cytokine analyzed to tumor-induced vascularization. Our data indicate that an optimal antiangiogenic therapy may require targeting of multiple angiogenic pathways that seem to differ markedly in pGBMs and sGBMs.

CXCL12 expression is predictive of a shorter time to tumor progression in low-grade glioma: a single-institution study in 50 patients

The clinical course of 50 patients with low-grade glioma (31 male, 19 female) undergoing surgery at a single Institution from 1992 to 1996 was analyzed in relationship with known prognostic factors as far as time to tumor progression (TTP) and survival time (ST) are concerned. Moreover, microvessel density (MVD) and expression of the angiogenesis-related chemokine CXCL12 were investigated in surgical specimens. Age at diagnosis ranged from 1 to 68 years (median 30). Histology revealed 11 fibrillary, 6 protoplasmatic, 5 gemistocytic astrocytoma, 18 oligoastrocytoma and 10 oligodendroglioma. Mean follow-up was 86 months. Four patients were lost to follow-up. Of the remaining 46, twenty-four have shown disease progression and 14 have died. Median overall survival was not achieved; an estimated 75% percentage of survivors was found at 78 months. Complete gross tumor removal was associated to a longer TTP (P = 0.04 logrank). Of the investigated immunohistochemical parameters, while MVD was not predictive of subsequent TTP, expression of CXCL12 was associated with a significantly shorter TTP (P = 0.01 logrank): this predictive value remained significant (P = 0.02) at multivariate analysis. The data suggest the possible prognostic value for CXCL-12 (an angiogenesis- and tumor-growth-related chemokine) on TTP in low-grade gliomas.

Molecular diagnostics in central nervous system tumors

Central nervous system (CNS) neoplasms can be diagnostically challenging, due to remarkably wide ranges in histologic appearance, biologic behavior, and therapeutic approach. Nevertheless, accurate diagnosis is the critical first step in providing optimal patient care. As with other oncology-based specialties, there is a rapidly expanding interest and enthusiasm for identifying and utilizing new biomarkers to enhance the day-to-day practice of surgical neuropathology. In this regard, the field is primed by recent advances in basic research, elucidating the molecular mechanisms of tumorigenesis and progression in the most common adult and pediatric brain tumors. Thus far, few have made the transition into routine clinical practice, the most notable example being 1p and 19q testing in oligodendroglial tumors. However, the field is rapidly evolving and many other biomarkers are likely to emerge as useful ancillary diagnostic, prognostic, or therapeutic aids. The goal of this article is to highlight the most common genetic alterations currently implicated in CNS tumors, focusing most on those that are either already in common use in ancillary molecular diagnostics testing or are likely to become so in the near future.

Vascular endothelial growth factor (VEGF) receptor neuropilin-1's distribution in astrocytic tumors

Neuropilin-1 is a VEGF165- and semaphorin receptor expressed by endothelial cells and tumor cells. The specific function of neuropilin-1 is not fully known, but in the developing nervous system neuropilin, as a semaphorin receptor, has been shown to influence neuronal guidance. The expression of neuropilin-1 was studied in low-grade and high-grade astrocytic tumors, the latter characterized by extensive angiogenesis. We examined 20 low-grade astrocytomas (WHO grade II) and 46 glioblastomas (WHO grade IV) immunohistochemically for neuropilin-1, p53 and EGFR. The glioblastomas were according to the p53 and EGFR expression classified as 35 primary--de novo--glioblastomas, 9 secondary glioblastomas, and 2 uncertain cases. Furthermore, the presence of mast cells was evaluated to search for any potential function in angiogenesis. The glioblastomas expressed neuropilin-1 in the endothelial cells of the proliferating vessels and the majority of the glioblastomas had immunoreactive neoplastic astrocytes, with no difference between the glioblastoma subgroups. Six out of twenty of the low-grade astrocytomas were negative in the endothelial cells and 8 out of 20 in the tumor cells for neuropilin-1. Mast cells were observed in the collagen matrix around larger vessels in the leptomeninges, but not adjacent to malignant tumor vessels or as part of the tumor process itself. Increased expression of neuropilin-1 is shown in endothelial cells and in neoplastic astrocytes of glioblastomas. Less neuropilin-1 expression is found in about half of the low-grade astrocytomas in both neoplastic astrocytes and endothelial cells. The results suggest a correlation between neuropilin-1 and vascularity in human astrocytic tumors and a possible role for neuropilin-1 as a receptor for VEGF-induced angiogenesis.

Hypoxia-inducible factor 1α/vascular endothelial growth factor axis in astrocytomas. Associations with microvessel morphometry, proliferation and prognosis

Hypoxia-inducible factor (HIF)-1alpha is a transcription factor that promotes ischaemia-driven angiogenesis. The aim of this study was to determine the relation of HIF-1alpha to vascular endothelial growth factor (VEGF; an important angiogenic molecule in brain tumours), p53 expression, angiogenesis, proliferative potential and clinical outcome in a large series of diffuse astrocytomas. Expression of HIF-1alpha, VEGF, Ki-67 (a proliferation-associated marker) and p53 was determined immunohistochemically in 83 adult patients with supratentorial diffuse astrocytomas. Microvessels, highlighted by means of anti-CD34 immunohistochemistry, were enumerated with computer-assisted image analysis. Although HIF-1alpha and VEGF were expressed in the majority of cases, their levels increased significantly with increasing grade and proliferative potential. HIF-1alpha positively correlated with microvessel counts and VEGF with total vascular area and the presence of rounder vessel sections. There was a positive correlation of VEGF with p53 expression in astrocytomas and anaplastic astrocytomas. In univariate analysis, both VEGF and HIF-1alpha were associated with shortened survival in the entire cohort, but lost significance when grades II/III and grade IV were analysed separately. Multivariate analysis revealed that the combination of HIF-1alpha with grade was a significant prognostic indicator. HIF-1alpha expression may be used to refine the prognostic information provided by grade in patients with diffuse astrocytomas. Its adverse prognostic effect is most likely mediated by hypoxia, the driving force for HIF-1alpha accumulation.

Protocol of radiotherapy for glioblastoma according to the expression of HIF-1

Hypoxia is a common feature of many malignant neoplasms and has been identified as a major reason for the radioresistance of malignant tumor tissue. On the other hand, the transcription factor hypoxia-inducible factor-1 (HIF-1) has attracted attention because it is rapidly expressed when tissue oxygen tension is reduced, thus playing the role of a hypoxic sensor. We investigated whether the level of HIF-1 expression in glioblastoma (GBM) could be an indicator in a protocol for postoperative radiotherapy. We immunohistologically evaluated the level of HIF-1 expression in 60 pathologically diagnosed GBMs. HIF-1 expression was positive in all tumors. The progression-free survival of the group receiving only conventional radiotherapy after surgery differed significantly according to the level of HIF-1 expression. The results of this study suggest that the HIF-1 expression level can be an indicator of tumor radioresistance, and that prior knowledge of the HIF-1 expression level allows the formulation of a protocol for postoperative radiotherapy.

Vascular endothelial growth factor expression correlates with matrix metalloproteinases MT1-MMP, MMP-2 and MMP-9 in human glioblastomas

Vascular endothelial growth factor (VEGF) is the major endothelial mitogen in central nervous system neoplasms and it is expressed in 64-95% of glioblastomas (GBMs). Tumour cells are the main source of VEGF in GBMs whereas VEGF receptors (VEGFR-1, its soluble form sVEGFR-1, VEGFR-2 and neuropilin-1) are expressed predominantly by endothelial cells. Infiltrating tumour cells and newly-formed capillaries progress through the extracellular matrix by local proteolysis involving matrix metalloproteinases (MMPs). Recent studies have shown that VEGF expression and bioavailability can be modulated by MMPs. We reported previously that the expression of MT1-MMP in human breast cancer cells was associated with an enhanced VEGF expression. We used quantitative RT-PCR, Western blot, gelatin zymography and immunohistochemistry to study the expression of VEGF, VEGFR-1, VEGFR-2, sVEGFR-1, neuropilin-1, MT1-MMP, MMP-2, MMP-9 and TIMP-2 in 20 human GBMs and 5 normal brains. The expression of these MMPs was markedly increased in most GBMs with excellent correlation between mRNA and protein levels; activated forms of MMP-2 and MMP-9 were present in 8/18 and 7/18 of GBMs. A majority of GBMs (17/20) also expressed high levels of VEGF, as previously reported, with strong correlation between VEGF and MT1-MMP gene expression levels, and double immunostaining showed that VEGF and MT1-MMP peptides co-localize in tumour and endothelial cells. Our results suggest that the interplay between metalloproteinases and VEGF previously described in experimental tumours may also be operative in human GBMs. Because of its dual ability to activate MMP-2 and to up-regulate VEGF, MT1-MMP might be of central importance in the growth of GBMs and represent an interesting target for anti-cancer treatments.

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.

Immunohistochemical markers for prognosis of oligodendroglial neoplasms

Despite numerous previous studies, oligodendrogliomas continue to generate considerable controversy in the identification of prognostic factors, including single histopathological patterns, and grade of tumor malignancy. The prognostic significance of various pathological and immunohistochemical factors has been intensively examined but numerous studies have yielded conflicting results. In the present study, biopsy samples of 123 oligodendrogliomas were examined immunohistochemically to evaluate a possible association between expression of various tumor-associated antigens and clinical outcome. Both the progression-free and overall survival times were significantly reduced for high-grade tumors, for Ki-S1 labeling index (LI) > 10%, for p27 LI < 20% and for p18, p53, and vascular endothelial growth factor (VEGF)-positive tumors. For low-grade tumors survival rates were significantly reduced for p27 LI less than 20%, whereas high-grade oligodendrogliomas with Ki-S1 LI greater than 10%, and with p18 positivity revealed significantly shortened survival times. We found no differences in survival times in patients with or without p 14ARF, p21, mdm2, and pRb immunoreactivity. Multivariate analysis revealed that risk of oligodendroglioma progression is associated with high-grade tumors, with Ki-S1 LI > 10%, and with p27 LI < 20%; whereas risk of death is associated with high-grade tumors, with Ki-S1 LI > 10%, and with p18 positivity. CART modeling process identified four final groups of oligodendroglioma patients: (1) thirty-nine patients with low-grade tumors and p27 LI > 20%; (2) twenty patients with low-grade tumors and p27 LI < 20%; (3) thirty-four patients with high-grade tumors and Ki-S1 LI < 10%; and (4) thirty patients with high-grade tumors and Ki-S1 LI >10%. In summary, both the p27 and Ki-S1 scores were found to be the strong predictors of oligodendroglioma outcome together with the WHO tumor grade and they seem to be useful for assessing individual prognosis in routinely processed specimens.

Immunohistochemical markers for prognosis of ependymal neoplasms

Intracranial ependymomas are the third most common primary brain tumor in children. Although clinical and histological criteria for ependymoma prognosis are recognized, studies have reported contradictory results. Prognostic significance based on immunohistochemistry of ependymomas has been reported in a few studies. One-hundred and twelve patients with intracranial ependymomas were examined retrospectively for immunoexpression of various tumor-associated antigens and apoptosis. The results demonstrated significant preponderance of expression of the tenascin, vascular endothelial growth factor protein (VEGF), epidermal growth factor (EGFR) and p53 protein in high-grade tumors. Also high-grade ependymomas revealed more prominent labeling indices (LI) for proliferative marker Ki-S1 and apoptotic index (AI), and lower LI for cyclin-dependent kinase inhibitors p27/Kipl and pl4ARF. For low-grade ependymomas the progression-free survival time (PFS) was found to be significantly shorter for Ki-S1 LI > 5%, and for tenascin, VEGF and EGFR positivity. For high-grade ependymomas PFS was found to be significantly reduced for p27 LI < 20%, p14ARF LI < 10%, for p53 positivity, and for AI < 1%. The CART modeling process exhibited five final groups of ependymoma patients (1) low-grade and tenascin-negative; (2) low-grade and tenascin-positive; (3) high-grade and p53-negative with p14 LI > 0%; (4) high-grade with combination of either p53 positivity and p14 LI > 10% or p53 negativity and p14 LI < 10%; (5) high-grade and p53-positive with pl4 LI < 10%. In summary, some immunohistochemical variables were found to be the strong predictors of ependymoma recurrence and they seem to be useful for assessing individual tumor prognosis in routinely processed biopsy specimens together with tumor grade. For histologically benign ependymomas immunohistochemical study should be focused on Ki-S1, tenascin, EGFR and VEGF evaluation, whereas p53 expression and number of p27, p14 and ISEL-positive nuclei will be of value in determining PFS from high-grade ependymomas.

Expression of vascular endothelial growth factors and their receptors in and around intracranial arteriovenous malformations

OBJECTIVE

The precise mechanisms responsible for the development and growth of intracranial arteriovenous malformations (AVMs) remain unclear, but it has been hypothesized that vascular endothelial growth factors (VEGFs) might be involved in their pathogenesis. The aim of this study was to examine immunohistochemically the presence of the VEGF family (VEGF-A to -D) and their receptors (Flt-1, Flk-1, and Flt-4) in the surgically resected AVM nidus.

METHODS

The AVM nidus was surgically obtained from 31 patients with AVMs (mean age, 40.5 yr, range 13-73 yr). The mean size of the nidus was 31.6 mm (range, 15-60 mm). Formalin-fixed, paraffin-embedded specimens were stained immunohistochemically by the labeled streptavidin-biotin method with antibodies against VEGF-A to -D, as well as Flt-1, Flk-1, and Flt-4.

RESULTS

Positive staining for VEGF-A to -D was observed in the endothelial cells of the abnormal vessels involved in the AVM nidus and in the cytoplasm of astroglia surrounding it. Samples from 30 (96.8%) of 31 patients stained positive for VEGF-A, 4 (9.7%) for VEGF-B, 17 (54.5%) for VEGF-C, and 16 (51.6%) for VEGF-D. Flt-1, Flk-1, and Flt-4 were also positive chiefly, but not exclusively, in the cytoplasm of vascular endothelium and smooth muscle cells of the vascular wall. With regard to VEGF receptors, it was found that among the 31 patients studied, 19 (61.3%) were immunohistochemically positive for Flt-1, 6 (19.4%) for Flk-1, and 19 (61.3%) for Flt-4. A comparison of mean nidus size and average age at operation revealed significant differences between patients positive for VEGF-C, VEGF-D, Flt-1, or Flt-4. In contrast, there were no significant differences in nidus size and age in patients positive for VEGF-A, VEGF-B, and Flk-1.

CONCLUSION

These results strongly suggest a possible contribution of the VEGF-VEGF receptor system to the growth of intracranial AVMs.

Pleomorphic xanthoastrocytomas: immunohistochemistry, grading and clinico-pathologic correlations. An analysis of 34 cases from a single Institute

Pleomorphic xanthoastrocytomas (PXAs) are characterized as a well-delineated tumor entity with clear peculiarities in clinico-radiological picture, pathological appearance and biological behavior. Usually the PXAs are associated with relatively good prognosis. Nevertheless, up to 35% of patients die following one and more recurrence with or without tumor malignant transformation. Till now, there is no agreement on what histopathological features constitute to objective and reliable signs of PXAs malignancy and clinical outcome. Thirty-four PXAs were subdivided on three subsets: typical (Grade I) - tumors without mitoses per 20 high power fields, proliferating (Grade II) tumors with mitoses but without necroses, and malignant (Grade III) - tumors with elevated mitotic index and necrotic foci. Also, immunohistochemical investigation with various tumor-associated antigens was performed. All PXAs subtypes showed differences in clinical outcomes. There were no recurrences and death among the tumors Grade I. Five out of 14 (36%) Grade II PXAs have recurred and one of them died. All 5 patients with PXAs Grade III have rapidly recurred and four of them died. Immunohistochemical variables, such as Ki-S1, p27/Kip1, vascular endothelial growth factor expression, p53 immunoreactivity and apoptotic index also exhibited significant differences among the three PXAs grades. The progression-free survival was significantly reduced for PXAs grade and presence of mitoses, whereas overall survival was reduced for mitotic index >or= 3 and presence of necroses. No one from immunohistochemical variables reached significant value. In summary, the three-tiered PXAs subdivision proposed by us is carrying some element of rationality but, undoubtedly, requires further prospective studies.

Immunohistochemical markers for intracranial ependymoma recurrence. An analysis of 88 cases

Intracranial ependymomas are the third most common primary brain tumor in children. Although clinical and histological criteria for ependymoma prognosis are recognized, studies have reported contradictory results. Prognostic significance based on immunohistochemistry of ependymomas has been reported in a few studies. Eighty-eight patients with intracranial ependymomas were examined retrospectively for immunoexpression of various tumor-associated antigens and apoptosis. The results demonstrated significant preponderance of expression of the tenascin, vascular endothelial growth factor protein (VEGF), epidermal growth factor (EGFR), and p53 protein in high-grade tumors. Also high-grade ependymomas revealed more prominent labeling indices (LI) for proliferative marker Ki-S1 and lower LI for cyclin-dependent kinase inhibitor p27/Kip1. For low-grade ependymomas the progression free survival time (PFS) was found to be significantly shorter for Ki-S1 LI>/=5%, and for tenascin, VEGF, and EGFR positivity. For high-grade ependymomas PFS was found to be significantly reduced for age <16 years, subtotal tumor removal, p27 LI <20%, p53 positivity, and for apoptotic index (AI) <1%. The classification regression tree analysis exhibited four groups of ependymomas; (1) low-grade tenascin negative (32 cases, recurrence rate=0), (2) high-grade with AI >/=1% (21 cases, recurrence rate=57%), (3) low-grade tenascin-positive (10 cases, recurrence rate=89%), and (4) high-grade with AI <1% (25 cases, recurrence rate=100%). So, the immunohistochemical variables were found to be strongest predictors of ependymoma recurrence and they seem to be useful for assessing individual tumor prognosis in routinely processed biopsy specimen.

The prognostic significance of vascular endothelial growth factor (VEGF C-1) immunoexpression in oligodendroglioma. An analysis of 91 cases

Oligodendrogliomas continue to generate considerable difficulties in identifying prognostic factors, including single histopathological patterns. Among the latter, vascular productive changes have been intensively examined but the obtained results appear to be controversial. Numerous studies have revealed an indisputable importance of vascular endothelial growth factor (VEGF) immunoreactivity for malignant progression of astrocytomas but the data regarding oligodendrogliomas are heterogeneous. Ninety-one patients with oligodendroglioma were examined retrospectively for VECF immunoexpression. The results demonstrated significant preponderance of intracellular VEGF expression for WHO grade III tumors. Nevertheless, VEGF staining patterns correlated with both progression-free and overall survival only in univariate, but not in multivarite analysis. Only WHO tumor grade was found to be an independent prognostic factor for oligodendroglioma outcome. Therefore, it seems unlikely that VEGF immunohistochemistry will be of value in assessing individual oligodendroglioma prognosis, especially for determining of both progression-free and overall survival from histologically low-grade tumors.