Inhibition of angiogenesis and invasion in malignant gliomas

Role of Hyperbaric Oxygenation Plus Hypofractionated Stereotactic Radiotherapy in Recurrent High-Grade Glioma

BACKGROUND

The presence of hypoxic cells in high-grade glioma (HGG) is one of major reasons for failure of local tumour control with radiotherapy (RT). The use of hyperbaric oxygen therapy (HBO) could help to overcome the problem of oxygen deficiency in poorly oxygenated regions of the tumour. We propose an innovative approach to improve the efficacy of hypofractionated stereotactic radiotherapy (HSRT) after HBO (HBO-RT) for the treatment of recurrent HGG (rHGG) and herein report the results of an ad interim analysis.

METHODS

We enrolled a preliminary cohort of 9 adult patients (aged >18 years) with a diagnosis of rHGG. HSRT was administered in daily 5-Gy fractions for 3-5 consecutive days a week. Each fraction was delivered up to maximum of 60 minutes after HBO.

RESULTS

Median follow-up from re-irradiation was 11.6 months (range: 3.2-11.6 months). The disease control rate (DCR) 3 months after HBO-RT was 55.5% (5 patients). Median progression-free survival (mPFS) for all patients was 5.2 months (95%CI: 1.34-NE), while 3-month and 6-month PFS was 55.5% (95%CI: 20.4-80.4) and 27.7% (95%CI: 4.4-59.1), respectively. Median overall survival (mOS) of HBO-RT was 10.7 months (95% CI: 7.7-NE). No acute or late neurologic toxicity >grade (G)2 was observed in 88.88% of patients. One patient developed G3 radionecrosis.

CONCLUSIONS

HSRT delivered after HBO appears to be effective for the treatment of rHGG, it could represent an alternative, with low toxicity, to systemic therapies for patients who cannot or refuse to undergo such treatments.

CLINICAL TRIAL REGISTRATION

www.ClinicalTrials.gov, identifier NCT03411408.

IDH1 mutation is associated with lower expression of VEGF but not microvessel formation in glioblastoma multiforme

Introduction

Glioblastoma multiforme (GBM) represents the most malignant primary brain tumor characterized by pathological vascularization. Mutations in isocitrate dehydrogenases 1 and 2 (IDH1 and IDH2) were observed in GBM. We aimed to assess the intra-tumor hypoxia, angiogenesis and microvessel formation in GBM and to find their associations with IDH1 mutation status and patients prognosis.

Methods

52 patients with a diagnosis of GBM were included into the study. IDH1 R132H mutation was assessed by RT-PCR from FFPE tumor samples obtained during surgery. The expression of markers of hypoxia (HIF2α), angiogenesis (VEGF), tumor microvascularity (CD31, CD34, vWF, CD105), and proliferation (Ki-67) were assessed immunohistochemically (IHC). IDH1 mutation and IHC markers were correlated with the patient survival.

Results

20 from 52 GBM tumor samples comprised IDH1 R132H mutation (38.5%). The majority of mutated tumors were classified as secondary glioblastomas (89.9%). Patients with IDH1 mutated tumors experienced better progression-free survival (P = 0.037) as well as overall survival (P = 0.035) compared with wild type tumors. The significantly lower expression of VEGF was observed in GBM with IDH1 mutation than in wild type tumors (P = 0.01). No such association was found for microvascular markers. The increased expression of newly-formed microvessels (ratio CD105/CD31) in tumor samples was associated with worse patient’s progression-free survival (P = 0.026).

Summary

No increase in HIF/VEGF-mediated angiogenesis was observed in IDH1-mutated GBM compared with IDH1 wild type tumors. The histological assessment of the portion of newly-formed microvessels in tumor tissue can be used for the prediction of GBM patient’s prognosis.

Ephrin-B3 supports glioblastoma growth by inhibiting apoptosis induced by the dependence receptor EphA4

EphA4, an Ephrins tyrosine kinase receptor, behaves as a dependence receptor (DR) by triggering cell apoptosis in the absence of its ligand Ephrin-B3. DRs act as conditional tumor suppressors, engaging cell death based on ligand availability; this mechanism is bypassed by overexpression of DRs ligands in some aggressive cancers. The pair EphA4/Ephrin-B3 favors survival of neuronal progenitors of the brain subventricular zone, an area where glioblastoma multiform (GBM) are thought to originate. Here, we report that Ephrin-B3 is highly expressed in human biopsies and that it inhibits EphA4 pro-apoptotic activity in tumor cells. Angiogenesis is directly correlated with GBM aggressiveness and we demonstrate that Ephrin-B3 also supports the survival of endothelial cells in vitro and in vivo. Lastly, silencing of Ephrin-B3 decreases tumor vascularization and growth in a xenograft mice model. Interference with EphA4/Ephrin-B3 interaction could then be envisaged as a relevant strategy to slow GBM growth by enhancing EphA4-induced cell death.

Molecularly targeted therapies for recurrent glioblastoma: current and future targets

OBJECT

Glioblastoma is the most aggressive and diffusely infiltrative primary brain tumor. Recurrence is expected and is extremely difficult to treat. Over the past decade, the accumulation of knowledge regarding the molecular and genetic profile of glioblastoma has led to numerous molecularly targeted therapies. This article aims to review the literature and highlight the mechanisms and efficacies of molecularly targeted therapies for recurrent glioblastoma.

METHODS

A systematic search was performed with the phrase "(name of particular agent) and glioblastoma" as a search term in PubMed to identify all articles published up until 2014 that included this phrase in the title and/or abstract. The references of systematic reviews were also reviewed for additional sources. The review included clinical studies that comprised at least 20 patients and reported results for the treatment of recurrent glioblastoma with molecular targeted therapies.

RESULTS

A total of 42 articles were included in this review. In the treatment of recurrent glioblastoma, various targeted therapies have been tested over the past 10-15 years. The targets of interest include epidermal growth factor receptor, vascular endothelial growth factor receptor, platelet-derived growth factor receptor, Ras pathway, protein kinase C, mammalian target of rapamycin, histone acetylation, and integrins. Unfortunately, the clinical responses to most available targeted therapies are modest at best. Radiographic responses generally range in the realm of 5%-20%. Progression-free survival at 6 months and overall survival were also modest with the majority of studies reporting a 10%-20% 6-month progression-free survival and 5- to 8-month overall survival. There have been several clinical trials evaluating the use of combination therapy for molecularly targeted treatments. In general, the outcomes for combination therapy tend to be superior to single-agent therapy, regardless of the specific agent studied.

CONCLUSIONS

Recurrent glioblastoma remains very difficult to treat, even with molecular targeted therapies and anticancer agents. The currently available targeted therapy regimens have poor to modest activity against recurrent glioblastoma. As newer agents are actively being developed, combination regimens have provided the most promising results for improving outcomes. Targeted therapies matched to molecular profiles of individual tumors are predicted to be a critical component necessary for improving efficacy in future trials.

Controlling tumor invasion: bevacizumab and BMP4 for glioblastoma

AIM

Bevacizumab has been reported to result in increased tumor invasion when used to treat malignant glioma. We hypothesized that BMP4 would prevent diffuse tumor infiltration induced by bevacizumab for malignant glioma in a xenograft model.

METHODS

Human glioblastoma (GBM) tumor cells were implanted in the striatum of immunocompromised mice. The animals were treated with bevacizumab and BMP4. Tumor growth and invasion were measured.

RESULTS

The bevacizumab-treated mice had increased survival compared with control animals (p = 0.02). BMP4 alone did not result in improved survival (p = 1.0). The bevacizumab (p = 0.006) and bevacizumab plus BMP4 (p = 0.006) groups demonstrated significantly decreased total tumor size compared with control. Tumor invasion was significantly decreased in the bevacizumab (p = 0.005), BMP4 (p = 0.04) alone and bevacizumab plus BMP4 (p = 0.002) groups compared with control. No synergistic effect between bevacizumab and BMP4 was observed.

CONCLUSION

Bevacizumab treatment did not result in diffuse infiltration of human GBM in a mouse xenograft model. BMP4 did have an independent favorable effect on GBM that was not synergistic with bevacizumab treatment.

Radiation enhances the invasiveness of irradiated and nonirradiated bystander hepatoma cells through a VEGF-MMP2 pathway initiated by p53

Recent evidence has shown that irradiation can promote the invasiveness of hepatocellular carcinoma cells and have an impact on the invasive behavior of nonirradiated surrounding cancer cells, which may enhance overall tumor aggressiveness. However, the role of the TP53 tumor suppressor gene in the invasion of irradiated hepatoma cells and their nonirradiated bystanders remain largely unknown. In the present study, we found that irradiation increased the invasiveness of human hepatoma HepG2 cells, and pretreatment of the cells with SU1498 (an inhibitor of vascular endothelial growth factor receptor 2, VEGFR2) and GM6001 (an inhibitor of matrix metalloproteinases 2, MMP2) demonstrated that radiation-enhanced invasiveness is associated with the interplay between MMP2 and VEGF signaling. In addition, while radiation-induced expression and phosphorylation of p53, inhibition of p53 function with pifithrin-α or transfection of cells with p53 siRNA significantly reduced the activation of both MMP2 and VEGF and resulted in a reduction of radiation-induced invasiveness. Interestingly, we also found that the invasiveness of the nonirradiated bystander cells was also elevated after co-culturing with irradiated cells and that bystander invasive potential was regulated paracrine in a manner by MMP2 and VEGF from the irradiated cells through a p53-dependent mechanism. Taken together, our data demonstrate that radiation-induced up-regulation of p53 is responsible for the promotion of VEGF-MMP2 pathway involved in the enhancement of invasiveness of both irradiated and bystander hepatoma cells.

Cilengitide treatment for malignant glioma: current status and future direction

Malignant glioma is the most common primary brain tumor and accounts for the majority of diagnoses. Treatment has involved a combination of surgery, radiation, and chemotherapy, yet these modalities rarely extend the life of the patient to more than one year from diagnosis. Integrins are expressed in tumor cells and tumor endothelial cells, and are important in angiogenesis and invasion in glioma. αvβ3 and αvβ5 integrins regulate cell adhesion, and inhibitors of these integrins suppress tumor growth in certain pre-clinical models. Several integrin-targeted drugs are in clinical trials as potential compounds for the treatment of cancer. Among them, cilengitide is a novel integrin antagonist for the treatment of glioblastoma. The multimodal anti-glioma effects are based on its cytotoxic, anti-angiogenic, anti-invasive, and synergetic effects. Preclinical studies showed a promising synergy between cilengitide and radiochemotherapy in order to normalize tumor vasculature and attenuate tumor invasion. Cilengitide is currently being assessed in phase III trials for patients with glioblastoma multiforme and in phase II trials for other types of cancers, demonstrating promising therapeutic outcomes to date. The results of these and other clinical studies are expected with great hope and interest. A more clear understanding of the benefits and pitfalls of each approach can then lead to the design of strategies to derive maximal benefit from these therapies.

Role for cytotoxic chemotherapy in patients with recurrent glioblastoma progressing on bevacizumab: a retrospective case series

One hundred patients, aged 36-84 years (median 62 years) with recurrent glioblastoma (GBM), were treated previously with surgery, concurrent radiotherapy and temozolomide and postradiotherapy temozolomide followed by single-agent bevacizumab (BEV) at either first (60 patients) or second recurrence (40 patients). Patients were then treated following progression on BEV only with BEV and carboplatin (75 patients), cyclophosphamide (15 patients) or BCNU (ten patients; BEV+). Three hundred and sixteen treatment cycles (median: 2; range: 1-9) were administered of BEV+. There were 74 grade 3 adverse events in 29 patients (29%) and 20 grade 4 adverse events in ten patients (10%). Following 2 months of BEV+, 60 patients (60%) demonstrated progressive disease and discontinued therapy. Forty patients (40%) had neuroradiographic stable disease. Survival ranged from 1 to 12 months (median: 4 months). Median and 6-month progression free survival was 2.5 months and 5%, respectively. BEV plus a cytotoxic chemotherapy demonstrated limited efficacy in BEV-refractory GBM and emphasizes an unmet need in neuro-oncology in adults with BEV-refractory GBM.

MiR-15b and miR-152 reduce glioma cell invasion and angiogenesis via NRP-2 and MMP-3

We tested invasion and angiogenesis related mRNA expression and miRNA profiles of glioma. Genes with mRNA expression that changed significantly were selected to predict possible miRNAs that regulate mRNA expression, and were then matched with miRNA results. NRP-2 with the matching miRNA miR-15b, and MMP-3 with the matching miRNA miR-152 were selected for further study. Luciferase activity assay confirmed that miR-15b and miR-152 attenuate expression of NRP-2 and MMP-3 protein by binding to NRP-2 and MMP-3 transcript, respectively. In vitro invasion assay data showed that miR-15b and miR-152 significantly decreased 9L cell invasiveness. In vitro tube formation assay data showed that miR-15b reduced tube formation. A preliminary pathway study indicated that miR-15b and miR-152 deactivated the MEK-ERK pathway via NRP-2 and MMP-3 in 9L cells, respectively.

VEGF induces angiogenesis in a zebrafish embryo glioma model established by transplantation of human glioma cells

Zebrafish (Danio rerio) is becoming an increasingly popular vertebrate cancer model. In this study, we established a xenotransplanted zebrafish embryo glioma model to further investigate the molecular mechanisms of tumor angiogenesis. We find that the glioma cell line U87 can survive, proliferate and induce additional SIV branches in zebrafish embryos. In addition, by the means of in situ hybridization and quantitive RT-PCR analyses we find that the transplanted U87 cells can induce the ectopic zebrafish vascular endothelial growth factor A (VEGF A) and its receptor VEGFR2/KDR mRNA expression and increase their expression levels, resulting in additional SIV branches.

High level of miR-221/222 confers increased cell invasion and poor prognosis in glioma

Background

MiR-221 and miR-222 (miR-221/222), upregulated in gliomas, can regulate glioma cell cycle progression and apoptosis, respectively. However, the association of miR-221/222 with glioma cell invasion and survival remains unknown.

Methods

Invasion capability of miR-221/222 was detected by mutiple analyses, including diffusion tensor imaging (DTI), transwell, wound healing and nude mouse tumor xenograft model assay. Further, the target of miR-221/222 was determined by luciferase reporter, western blot and gene rescue assay. The association of miR-221/222 with outcome was examined in fifty glioma patients.

Results

MiR-221/222 expression was significantly increased in high-grade gliomas compared with low-grade gliomas, and positively correlated with the degree of glioma infiltration. Over-expression of miR-221/222 increased cell invasion, whereas knockdown of miR-221/222 decreased cell invasion via modulating the levels of the target, TIMP3. Introduction of a TIMP3 cDNA lacking 3’ UTR abrogated miR-221/222-induced cell invasion. In addition, knockdown of miR-221/222 increased TIMP3 expression and considerably inhibited tumor growth in a xenograft model. Finally, the increased level of miR-221/222 expression in high-grade gliomas confers poorer overall survival.

Conclusions

The present data indicate that miR-221 and miR-222 directly regulate cell invasion by targeting TIMP3 and act as prognostic factors for glioma patients.

Towards tailored therapy of glioblastoma multiforme

Gliobastoma multiform (GBM) is the most common and aggressive brain tumor, which is characterized by its infiltrative nature. Current standard therapy for GBMs consists of surgery followed by radiotherapy combined with the alkylating agent temozolomide (TMZ). Recent clinical trials have demonstrated that this chemo-irradiation approach results in a significant increase in survival compared to radiotherapy alone. Nevertheless, due to tumor recurrence, the median survival time is still limited to approximately 15 months. Recently, several studies have focused on aberrant signal transduction in GBM, resistance mechanisms of GBM to TMZ and to radiotherapy. Attention has been focused on molecular targets including phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway, protein kinase C (pKC) pathway, Ras/mitogen-activated protein kinase pathway (MAPK), Wnt pathway and intrinsic or extrinsic apoptosis pathways. In addition, research has been directed to radiotherapy and radiosensitizing agents, and cancer gene therapy as well. This article will address several resistance mechanisms of GBM to chemotherapy and radiotherapy and the recent preclinical and clinical studies on targeted therapy.

Anti-angiogenic therapy in glioma

There has been great interest in developing anti-angiogenic therapies for the treatment of patients with high-grade gliomas. In fact, some anti-angiogenic agents are now routinely used for the treatment of patients with glioblastoma. However, the use of these agents is largely based on trials which indicate an initial radiographic response, while it remains unclear whether any anti-angiogenic therapies tested to date have improved the overall survival of patients with malignant glial tumours. This manuscript reviews the landscape of anti-angiogenic therapy in glioma, with a focus on GBM, and demonstrates that further innovation is needed to determine the true utility of anti-angiogenic therapy.

Three-dimensional imaging of the mouse neurovasculature with magnetic resonance microscopy

Knowledge of the three-dimensional (3D) architecture of blood vessels in the brain is crucial because the progression of various neuropathologies ranging from Alzheimer's disease to brain tumors involves anomalous blood vessels. The challenges in obtaining such data from patients, in conjunction with development of mouse models of neuropathology, have made the murine brain indispensable for investigating disease induced neurovascular changes. Here we describe a novel method for “whole brain” 3D mapping of murine neurovasculature using magnetic resonance microscopy (μMRI). This approach preserves the vascular and white matter tract architecture, and can be combined with complementary MRI contrast mechanisms such as diffusion tensor imaging (DTI) to examine the interplay between the vasculature and white matter reorganization that often characterizes neuropathologies. Following validation with micro computed tomography (μCT) and optical microscopy, we demonstrate the utility of this method by: (i) combined 3D imaging of angiogenesis and white matter reorganization in both, invasive and non-invasive brain tumor models; (ii) characterizing the morphological heterogeneity of the vascular phenotype in the murine brain; and (iii) conducting “multi-scale” imaging of brain tumor angiogenesis, wherein we directly compared in vivo MRI blood volume measurements with ex vivo vasculature data.

Vascular phenotyping of brain tumors using magnetic resonance microscopy (μMRI)

Abnormal vascular phenotypes have been implicated in neuropathologies ranging from Alzheimer's disease to brain tumors. The development of transgenic mouse models of such diseases has created a crucial need for characterizing the murine neurovasculature. Although histologic techniques are excellent for imaging the microvasculature at submicron resolutions, they offer only limited coverage. It is also challenging to reconstruct the three-dimensional (3D) vasculature and other structures, such as white matter tracts, after tissue sectioning. Here, we describe a novel method for 3D whole-brain mapping of the murine vasculature using magnetic resonance microscopy (μMRI), and its application to a preclinical brain tumor model. The 3D vascular architecture was characterized by six morphologic parameters: vessel length, vessel radius, microvessel density, length per unit volume, fractional blood volume, and tortuosity. Region-of-interest analysis showed significant differences in the vascular phenotype between the tumor and the contralateral brain, as well as between postinoculation day 12 and day 17 tumors. These results unequivocally show the feasibility of using μMRI to characterize the vascular phenotype of brain tumors. Finally, we show that combining these vascular data with coregistered images acquired with diffusion-weighted MRI provides a new tool for investigating the relationship between angiogenesis and concomitant changes in the brain tumor microenvironment.

Antiangiogenic agents in the treatment of recurrent or newly diagnosed glioblastoma: analysis of single-agent and combined modality approaches

Surgical resection followed by radiotherapy and temozolomide in newly diagnosed glioblastoma can prolong survival, but it is not curative. For patients with disease progression after frontline therapy, there is no standard of care, although further surgery, chemotherapy, and radiotherapy may be used. Antiangiogenic therapies may be appropriate for treating glioblastomas because angiogenesis is critical to tumor growth. In a large, noncomparative phase II trial, bevacizumab was evaluated alone and with irinotecan in patients with recurrent glioblastoma; combination treatment was associated with an estimated 6-month progression-free survival (PFS) rate of 50.3%, a median overall survival of 8.9 months, and a response rate of 37.8%. Single-agent bevacizumab also exceeded the predetermined threshold of activity for salvage chemotherapy (6-month PFS rate, 15%), achieving a 6-month PFS rate of 42.6% (p < 0.0001). On the basis of these results and those from another phase II trial, the US Food and Drug Administration granted accelerated approval of single-agent bevacizumab for the treatment of glioblastoma that has progressed following prior therapy. Potential antiangiogenic agents-such as cilengitide and XL184-also show evidence of single-agent activity in recurrent glioblastoma. Moreover, the use of antiangiogenic agents with radiation at disease progression may improve the therapeutic ratio of single-modality approaches. Overall, these agents appear to be well tolerated, with adverse event profiles similar to those reported in studies of other solid tumors. Further research is needed to determine the role of antiangiogenic therapy in frontline treatment and to identify the optimal schedule and partnering agents for use in combination therapy.

Retrospective study of dasatinib for recurrent glioblastoma after bevacizumab failure

There is no effective treatment for recurrent glioblastoma (GBM) after bevacizumab failure. Putative mechanisms of resistance to bevacizumab include increased pericyte coverage, mediated partly by platelet-derived growth factor receptor (PDGFR) signaling, and an infiltrative tumor growth pattern potentially dependent on SRC. We explored the efficacy of dasatinib, a SRC, BCR-ABL, c-KIT, EPHA2, and PDGFRβ inhibitor, in patients with recurrent GBM after bevacizumab failure. Adult patients with histologically confirmed GBM who failed bevacizumab therapy were treated with dasatinib 70-100 mg twice daily in combination with bevacizumab (n = 14), until tumor progression or unacceptable toxicity. Fourteen patients were treated. Median age was 55 years (range 32-66) and median KPS was 80 (range 50-90). All patients (100%) had glioblastomas. The median number of prior regimens was 4 (range from 2 to 6). Of the thirteen evaluable patients, none had a complete or partial response. Only one patient had stable disease after an 8 week interval. Median progression-free survival (PFS) was 28 days (95% confidence interval [CI] 26-35 days). Six month progression-free survival (PFS6) was 0%. Median overall survival (OS) was 78 days (95% CI 41-137 days). Treatment was moderately well-tolerated, although one patient sustained a grade 4 intracerebral hemorrhage. Dasatinib in conjunction with bevacizumab does not appear to have activity in patients with recurrent, heavily pretreated GBM.

Phase 1 clinical trial of bortezomib in adults with recurrent malignant glioma

Bortezomib selectively binds and inhibits the 20S proteasome enzyme's active sites. This study was conducted to determine the side effects and maximum tolerated dose (MTD) of bortezomib in patients with recurrent malignant glioma. Separate dose escalations were conducted in patients taking or not taking enzyme-inducing anti-seizure drugs (+/-EIASD). The starting dose in both groups was 0.9 mg/m(2) intravenously twice weekly for the first three of each 4 week cycle. Imaging assessment of response was carried out and Plasma 20S proteasome activity inhibition and imaging was conducted to monitor efficacy. The 66 patients enrolled had a median age of 51 years, median KPS of 90%, and 77% had glioblastoma multiforme. The MTD in the -EIASD group was 1.70 mg/m(2) based on grade 3 thrombocytopenia, sensory neuropathy and fatigue. In the +EIASD group escalation was terminated at 2.5 mg/m(2) without meeting meet the MTD criteria. However, proteasome inhibition in this group did not change at doses above 1.90 mg/m(2) suggesting that further escalations would be unlikely to increase a biologic effect. Mean proteasome inhibition plateaued in +EIASD patients receiving 2.1 mg/m(2) of bortezomib at 77 ± 12% and in -EIASD patients treated with a dose of 1.7 mg/m(2) at 79 ± 6%. Two partial responses were observed. This study determined that EIASDs effect the MTD of bortezomib and the dose required for maximal inhibition of whole blood 20S proteasome. Some evidence of clinical activity was noted in this phase I study in patients with recurrent high grade gliomas.

Temozolomide/PLGA microparticles plus vatalanib inhibits tumor growth and angiogenesis in an orthotopic glioma model

Temozolomide (TM) has anti-tumor activity in patients with malignant glioma. Implantable poly (D,L-lactide-co-glycolide) (PLGA) microparticles of TM (TM-MS) have been developed, enhancing the cytotoxicity of TM to Glioma C6 cells. Vatalanib, as anti-angiogenic agent, has also shown anti-tumor activity with malignant gliomas. We examined the combined effects of TM-MS and vatalanib in a rat orthotopic glioma model and found TM-MS offered a greater tumor inhibition than TM, and combination treatment with both of them improved the survival time versus single agent therapy. The combination treatment also demonstrated an inhibition to rat glioma tumors, a significant decrease in cell proliferation, an increase in apoptosis, and a lower microvessel density within the glioma tumors. The results suggest that TM-MS can more effectively inhibit tumor than TM, and combination treatment with TM-MS and vatalanib inhibits tumor growth and angiogenesis and may prove to be a promising therapy for malignant gliomas.

Gallic acid suppresses cell viability, proliferation, invasion and angiogenesis in human glioma cells

Gallic acid, an organic acid, also known as 3,4,5-trihydroxybenzoic acid, is cytotoxic against certain cancer cells, without harming normal cells. The objective of this study is to evaluate whether gallic acid can inhibit glioma cell viability, proliferation, invasion and reduce glioma cell mediated angiogenesis. Treatment of U87 and U251n glioma cells with gallic acid inhibited cell viability in a dose-dependent manner. BrdU and tube formation assays indicated that gallic acid significantly decreased glioma cell proliferation and tube formation in mouse brain endothelial cells, respectively. In addition, gallic acid decreased U87 cell invasion in vitro. Western blot analysis showed that expression of ADAM17, p-Akt and p-Erk was suppressed by gallic acid in both U87 and U251n cell lines. These data suggest that suppression of ADAM17 and downregulation of PI3K/Akt and Ras/MAPK signaling pathways may contribute to gallic acid-induced decrease of invasiveness. Gallic acid may be a valuable candidate for treatment of brain tumor.

Molecular mechanisms involved in the antitumor activity of cannabinoids on gliomas: role for oxidative stress

Cannabinoids, the active components of Cannabis sativa, have been shown to exert antiproliferative and proapoptotic effects on a wide spectrum of tumor cells and tissues. Of interest, cannabinoids have displayed great potency in reducing the growth of glioma tumors, one of the most aggressive CNS tumors, either in vitro or in animal experimental models curbing the growth of xenografts generated by subcutaneous or intrathecal injection of glioma cells in immune-deficient mice. Cannabinoids appear to be selective antitumoral agents as they kill glioma cells without affecting the viability of non-transformed cells. This review will summarize the anti-cancer properties that cannabinoids exert on gliomas and discuss their potential action mechanisms that appear complex, involving modulation of multiple key cell signaling pathways and induction of oxidative stress in glioma cells.

Bevacizumab salvage therapy following progression in high-grade glioma patients treated with VEGF receptor tyrosine kinase inhibitors

Agents targeting the vascular endothelial growth factor (VEGF) pathway are being used with increasing frequency in patients with recurrent high-grade glioma. The effect of more than one antiangiogenic therapy given in succession has not been established. We reviewed the efficacy of bevacizumab, a VEGF-A monoclonal antibody, in patients who progressed following prior therapy with VEGF receptor tyrosine kinase inhibitors (R-TKi). Seventy-three patients with recurrent high-grade gliomas received VEGF R-TKi (cediranib, sorafenib, pazopanib, or sunitinib) as part of phase I or II clinical trials. Twenty-four of these patients with glioblastoma progressed and received bevacizumab-containing regimens immediately after R-TKi. Those who stopped R-TKi therapy for reasons other than disease progression, or received a treatment that did not include bevacizumab, were excluded from the analysis. The efficacy of bevacizumab-containing regimens in these 24 patients was evaluated. During R-TKi therapy, 6 of 24 patients (25%) had a partial response (PR) to treatment. The 6-month progression-free survival (APF6) was 16.7% and median time-to-progression (TTP) was 14.3 weeks. Grade III/IV toxicities were seen in 13 of 24 patients (54%). Subsequently with bevacizumab salvage therapy, 5 of 24 patients (21%) had a PR, the APF6 was 12.5%, and the median TTP was 8 weeks. Five of 24 patients had grade III/IV toxicities (21%). The median overall survival (OS) from the start of R-TKi therapy was 9.2 months (range: 2.8-34.1+), whereas the median OS after bevacizumab was 5.2 months (range: 1.3-28.9+). Bevacizumab retains modest activity in high-grade glioma patients who progress on R-TKi. However, the APF6 of 12.5% in this cohort of patients indicates that durable tumor control is not achieved for most patients.

Identification of the role of Smad interacting protein 1 (SIP1) in glioma

Glioma is an extremely aggressive and lethal form of brain cancer. Despite recent advances in diagnostics and treatments, prognosis for advanced patients suffering from these diseases remains poor. Therefore, identification of new therapeutic targets for glioma is of significant importance. In this study, we identified the important role of Smad interacting protein 1 (SIP1; also known as ZEB2) in glioma. We firstly found that SIP1 expression was high in four tumorigenic glioma cell lines but low in two nontumorigenic glioma cell lines. By knockdown or overexpression assay, we discovered that knockdown of SIP1 expression statistically significantly inhibited cell migration and invasion of tumorigenic glioma cells, while overexpression of SIP1 promoted cell migration and invasion of nontumorigenic glioma cells. SIP1 knockdown inhibits and overexpression promotes glioma cell clonogenicity in vitro. Further studies identified that SIP1 overexpression inhibits expression of E-cadherin and enhances expression of mesenchymal proteins such as fibronectin and vimentin. This study supports the rationale for developing SIP1 as a potential therapeutic and diagnostic target for gliomas.

Biology of angiogenesis and invasion in glioma

Treatment of adult brain tumors, in particular glioblastoma, remains a significant clinical challenge, despite modest advances in surgical technique, radiation, and chemotherapeutics. The formation of abnormal, dysfunctional tumor vasculature and glioma cell invasion along white matter tracts are believed to be major components of the inability to treat these tumors effectively. Recent insight into the fundamental processes governing glioma angiogenesis and invasion provide a renewed hope for development of novel strategies aimed at reducing the morbidity of this uniformly fatal disease. In this review, we discuss background biology of the blood brain barrier and its pertinence to blood vessel formation and tumor invasion. We will then focus our attention on the biology of glioma angiogenesis and invasion, and the key mediators of these processes. Last, we will briefly discuss recent and ongoing clinical trials targeting mediators of angiogenesis or invasion in glioma patients. The findings provide a renewed hope for those endeavoring to improve treatment of patients with glioma by providing a novel set of rational targets for translational drug discovery.

Angiogenesis as a therapeutic target in malignant gliomas

Currently, adult glioblastoma (GBM) patients have poor outcomes with conventional cytotoxic treatments. Because GBMs are highly angiogenic tumors, inhibitors that target tumor vasculature are considered promising therapeutic agents in these patients. Encouraging efficacy and tolerability in preliminary clinical trials suggest that targeting angiogenesis may be an effective therapeutic strategy in GBM patients. However, the survival benefits observed to date in uncontrolled trials of antiangiogenic agents have been modest, and several obstacles have limited their effectiveness. This article reviews the rationale for antiangiogenic agents in GBM, their potential mechanisms of action, and their clinical development in GBM patients. Although challenges remain with this approach, ongoing studies may improve upon the promising initial benefits already observed in GBM patients.

Antiangiogenic therapy in malignant gliomas

PURPOSE OF REVIEW

Antiangiogenic drugs are increasingly used in malignant glioma therapy. This article reviews the rationale for targeting angiogenesis in malignant gliomas, summarizes relevant clinical trial results, and discusses promising avenues of investigation in antiangiogenic therapy.

RECENT FINDINGS

Combination therapy with bevacizumab, the humanized monoclonal antibody against vascular endothelial growth factor, and irinotecan has emerged as the treatment of choice for recurrent malignant gliomas, prolonging progression-free survival markedly in comparison with historical controls. Several small molecule tyrosine kinase inhibitors of the vascular endothelial growth factor receptor are under investigation and show promise as well.

SUMMARY

Antiangiogenic treatments are effective and well tolerated options for recurrent malignant glioma. Future studies will determine whether these drugs have a role in first line therapy. Studies are in progress to elucidate mechanisms of resistance and suggest approaches to further improve survival in patients with these challenging tumors.

Emerging antiangiogenic treatments for gliomas - efficacy and safety issues

PURPOSE OF REVIEW

To review the rationale and recent experience of angiogenesis inhibitors in malignant gliomas and to highlight both the promise and potential complications of these agents.

RECENT FINDINGS

Several new agents targeting angiogenesis in malignant gliomas have become available and have been increasingly used to complement conventional chemotherapy. Specifically, bevacizumab, often in combination with irinotecan, has demonstrated favorable results in achieving significant radiographic responses and in prolonging progression-free survival in patients with recurrent malignant glioma.

SUMMARY

Antiangiogenic drugs have been shown to have promising activity in recurrent malignant gliomas. Investigation of novel antiangiogenic compounds and future clinical trials will determine whether these drugs have a role in first-line therapy. This article reviews the rationale for targeting angiogenesis in malignant brain tumors and summarizes the results of recent clinical trials. In addition, this review will outline potential toxicities associated with angiogenesis inhibition in an attempt to provide practical guidance to physicians treating patients with malignant gliomas.

Role of a second chemotherapy in recurrent malignant glioma patients who progress on bevacizumab

Bevacizumab is a humanized monoclonal antibody against vascular endothelial growth factor (VEGF) that has efficacy in recurrent malignant gliomas, particularly in combination with irinotecan. However, responses are rarely durable. Continuation of bevacizumab in combination with another chemotherapeutic agent may demonstrate some activity. In this article we present a retrospective review of 54 patients with recurrent malignant gliomas who progressed on a bevacizumab-containing regimen and were then treated with an alternate bevacizumab-containing regimen. All patients received intravenous bevacizumab (5-10 mg/kg) every 2 weeks alone or in combination with an additional chemotherapeutic agent, such as irinotecan. There was no limit on the number of prior therapies. Clinical characteristics and outcomes were reviewed. Tumor progression was determined by a combination of clinical status and radiographic changes. Patients were 33 men, 21 women (median age, 50 years; range, 23-72 years) with a median KPS score of 80 prior to the first bevacizumab-containing regimen and 70 prior to the second regimen; median prior chemotherapy regimens including the first bevacizumab-containing regimen was 3 (range, 2-5). Median progression-free survival (PFS) on the first bevacizumab-containing regimen was 124 days (95% confidence interval [CI], 87-154 days); 6-month (6M)-PFS was 33%. Median PFS on the second bevacizumab-containing regimen was 37.5 days (95% CI, 34-42 days); 6M-PFS was 2%. Ten patients on the first regimen and 12 patients on the second regimen suffered grade 3/4 toxicities. Those patients with malignant gliomas who progressed despite a bevacizumab-containing regimen rarely responded to the second bevacizumab-containing chemotherapeutic regimen. In such patients, alternate therapies should be considered.

Recurrence pattern in glioblastoma multiforme patients treated with anti-angiogenic chemotherapy

PURPOSE

Glioblastoma multiforme is the prototype of an angiogenic tumour. Under experimental conditions, anti-angiogenic therapy strategies lead to an increased invasion. Here we report on the pattern of tumour recurrence in glioblastoma patients treated with an anti-angiogenic chemotherapy.

PATIENTS AND METHODS

A total of 32 patients with glioblastoma multiforme and a residual tumour mass after operation were treated with a continuous low-dose chemotherapy with temozolomide and a COX-II inhibitor, a presumably anti-angiogenic therapy.

RESULTS

While anti-tumour activity of this therapy regimen was excellent with a mean overall time to progression of 10.4 (+/-0.9) months and a mean overall survival of 17.8 (+/-1.5) months, an unusually high rate of distant recurrences was observed (62.5%).

CONCLUSION

Patients treated with an anti-angiogenic chemotherapy experience distant recurrences at a higher rate than reported for conventional therapies. This may reflect an anti-angiogenic therapy-induced activation of glioma invasion confirming similar recently published experimental results.

Selective inhibition of matrix metalloproteinase-14 blocks tumor growth, invasion, and angiogenesis

Inhibition of specific matrix metalloproteinases (MMP) is an attractive noncytotoxic approach to cancer therapy. MMP-14, a membrane-bound zinc endopeptidase, has been proposed to play a central role in tumor growth, invasion, and neovascularization. Besides cleaving matrix proteins, MMP-14 activates proMMP-2 leading to an amplification of pericellular proteolytic activity. To examine the contribution of MMP-14 to tumor growth and angiogenesis, we used DX-2400, a highly selective fully human MMP-14 inhibitory antibody discovered using phage display technology. DX-2400 blocked proMMP-2 processing on tumor and endothelial cells, inhibited angiogenesis, and slowed tumor progression and formation of metastatic lesions. The combination of potency, selectivity, and robust in vivo activity shows the potential of a selective MMP-14 inhibitor for the treatment of solid tumors.

TNF-alpha and the IFN-gamma-inducible protein 10 (IP-10/CXCL-10) delivered by parvoviral vectors act in synergy to induce antitumor effects in mouse glioblastoma

Interferon-gamma-inducible protein 10 is a potent chemoattractant for natural killer cells and activated T lymphocytes. It also displays angiostatic properties and some antitumor activity. Tumor necrosis factor-alpha (TNF-alpha) is a powerful immunomodulating cytokine with demonstrated tumoricidal activity in various tumor models and the ability to induce strong immune responses. This prompted us to evaluate the antitumor effects of recombinant parvoviruses designed to deliver IP-10 or TNF-alpha into a glioblastoma. When Gl261 murine glioma cells were infected in vitro with an IP-10- or TNF-alpha-transducing parvoviral vector and were subcutaneously implanted in mice, tumor growth was significantly delayed. Complete tumor regression was observed when the glioma cells were coinfected with both the vectors, demonstrating synergistic antitumor activity. In an established in vivo glioma model, however, repeated simultaneous peritumoral injection of the IP-10- and TNF-alpha-delivering parvoviruses failed to improve the therapeutic effect as compared with the use of a single cytokine-delivering vector. In this tumor model, cytokine-mediated immunostimulation, rather than inhibition of vascularization, is likely responsible for the therapeutic efficacy.