Antiangiogenic strategies for treatment of malignant gliomas

The strange Microenvironment of Glioblastoma

Glioblastoma (GB) is the most common and aggressive primary brain tumor, with poor patient survival and lack of effective therapies. Late advances trying to decipher the composition of the GB tumor microenvironment (TME) emphasized its role in tumor progression and potentialized it as a therapeutic target. Many components participate critically to tumor development and expansion such as blood vessels, immune cells or components of the nervous system. Dysmorphic tumor vasculature brings challenges to optimal delivery of cytotoxic agents currently used in clinics. Also, massive infiltration of immunosuppressive myeloid cells and limited recruitment of T cells limits the success of conventional immunotherapies. Neuronal input seems also be required for tumor expansion. In this review, we provide a comprehensive report of vascular and immune component of the GB TME and their cross talk during GB progression.

Postoperative resveratrol administration improves prognosis of rat orthotopic glioblastomas

Background

Although our previous study revealed lumbar punctured resveratrol could remarkably prolong the survival of rats bearing orthotopic glioblastomas, it also suggested the administration did not completely suppress rapid tumour growth. These evidences led us to consider that the prognosis of tumour-bearing rats may be further improved if this treatment is used in combination with neurosurgery. Therefore, we investigated the effectiveness of the combined treatment on rat orthotopic glioblastomas.

Methods

Rat RG2 glioblastoma cells were inoculated into the brains of 36 rats. The rats were subjected to partial tumour removal after they showed symptoms of intracranial hypertension. There were 28 rats that survived the surgery, and these animals were randomly and equally divided into the control group without postoperative treatment and the LP group treated with 100 μl of 300 μM resveratrol via the LP route. Resveratrol was administered 24 h after tumour resection in 3-day intervals, and the animals received 7 treatments. The intracranial tumour sizes, average life span, cell apoptosis and STAT3 signalling were evaluated by multiple experimental approaches in the tumour tissues harvested from both groups.

Results

The results showed that 5 of the 14 (35.7%) rats in the LP group remained alive over 60 days without any sign of recurrence. The remaining nine animals had a longer mean postoperative survival time (11.0 ± 2.9 days) than that of the (7.3 + 1.3 days; p < 0.05) control group. The resveratrol-treated tumour tissues showed less Ki67 labelling, widely distributed apoptotic regions, upregulated PIAS3 expression and reduced p-STAT3 nuclear translocation.

Conclusions

This study demonstrates that postoperative resveratrol administration efficiently improves the prognosis of rat advanced orthotopic glioblastoma via inhibition of growth, induction of apoptosis and inactivation of STAT3 signalling. Therefore, this therapeutic approach could be of potential practical value in the management of glioblastomas.

A single dose of peripherally infused EGFRvIII-directed CAR T cells mediates antigen loss and induces adaptive resistance in patients with recurrent glioblastoma

We conducted a first-in-human study of intravenous delivery of a single dose of autologous T cells redirected to the epidermal growth factor receptor variant III (EGFRvIII) mutation by a chimeric antigen receptor (CAR). We report our findings on the first 10 recurrent glioblastoma (GBM) patients treated. We found that manufacturing and infusion of CAR-modified T cell (CART)-EGFRvIII cells are feasible and safe, without evidence of off-tumor toxicity or cytokine release syndrome. One patient has had residual stable disease for over 18 months of follow-up. All patients demonstrated detectable transient expansion of CART-EGFRvIII cells in peripheral blood. Seven patients had post-CART-EGFRvIII surgical intervention, which allowed for tissue-specific analysis of CART-EGFRvIII trafficking to the tumor, phenotyping of tumor-infiltrating T cells and the tumor microenvironment in situ, and analysis of post-therapy EGFRvIII target antigen expression. Imaging findings after CART immunotherapy were complex to interpret, further reinforcing the need for pathologic sampling in infused patients. We found trafficking of CART-EGFRvIII cells to regions of active GBM, with antigen decrease in five of these seven patients. In situ evaluation of the tumor environment demonstrated increased and robust expression of inhibitory molecules and infiltration by regulatory T cells after CART-EGFRvIII infusion, compared to pre-CART-EGFRvIII infusion tumor specimens. Our initial experience with CAR T cells in recurrent GBM suggests that although intravenous infusion results in on-target activity in the brain, overcoming the adaptive changes in the local tumor microenvironment and addressing the antigen heterogeneity may improve the efficacy of EGFRvIII-directed strategies in GBM.

Demonstration of DCE-MRI as an early pharmacodynamic biomarker of response to VEGF Trap in glioblastoma

Glioblastoma (GBM) is an incurable brain tumor characterized by the expression of pro-angiogenic cytokines. A recent phase II clinical trial studied VEGF Trap in adult patients with temozolomide-resistant GBM. We sought to explore changes in [¹⁸F]Fluorodeoxyglucose positron emission tomography (FDG-PET) or magnetic resonance imaging (MRI) in trial participants correlating these changes with disease response. FDG-PET and MRI images obtained before and after the first dose of VEGF Trap were spatially co-registered. Regions of interest on each image slice were combined to produce a volume of interest representative of the entire tumor. Percent and absolute changes in maximum FDG-avidity, mean apparent diffusion coefficient (ADC), K_trans, and Ve were calculated per lesion. Among the 12 participants that underwent dynamic contrast enhanced MRI (DCE-MRI), there were large, statistically significant reductions in K_trans and Ve (median difference = -41.8 %, p < 0.02 and -42.6 %, p < 0.04, respectively). In contrast, there were no significant reductions in ADC or FDG-PET SUVmax values. DCE-MRI is a useful measure of early pharmacodynamic effects of VEGF Trap on tumor vasculature. The absence of significant changes in FDG-PET and DW-MRI suggest that the early pharmacodynamic effects are specific to tumor perfusion and/or permeability and do not directly inhibit metabolism or induce cell death. DCE-MRI in conjunction with standard imaging may be promising for the identification of anti-angiogenic effects in this patient population with this therapeutic target. Further studies are needed to evaluate the relationship between DCE-MRI response and clinical outcome.

The rational design of NAMI-A-loaded mesoporous silica nanoparticles as antiangiogenic nanosystems

Angiogenesis is essential for tumorous progression and metastasis. The RGD (Arg-Gly-Asp acid) peptide has been demonstrated to be a remarkable targeting reagent and can be distinguished by the integrin receptor overexpressed in various human tumor cells. Mesoporous silica nanoparticles (MSNs) are one of the most promising carriers applied for delivery of drugs or genes. It is well known that NAMI-A is an excellent drug for antimigration of tumor cells. Targeting the tumor vasculature with RGD-modified nanomaterials is expected to be a promising strategy for cancer therapy. Herein we have investigated the antiangiogenic activity of NAMI-A-loaded and RGD peptide surface decorated mesoporous silica nanoparticles in vitro and in vivo. The results revealed that NAMI-A@MSN-RGD remarkably enhanced the cellular uptake and antiangiogenic efficacy in contrast to bare NAMI-A in vitro. The nanosystem of NAMI-A@MSN-RGD also exhibited inspiring antiangiogenic action in vivo. Furthermore, the RGD-functionalized nanodrug inhibited angiogenesis by means of apoptosis by triggering ROS-mediated DNA damage in human umbilical vein endothelial cells (HUVECs). Our results suggested that the use of RGD-peptide modified MSNs as a vehicle of anticancer drugs is an efficient way to construct cancer-targeted nanosystems with antiangiogenic activity.

Rational development and characterization of humanized anti-EGFR variant III chimeric antigen receptor T cells for glioblastoma

Chimeric antigen receptors (CARs) are synthetic molecules designed to redirect T cells to specific antigens. CAR-modified T cells can mediate long-term durable remissions in B cell malignancies, but expanding this platform to solid tumors requires the discovery of surface targets with limited expression in normal tissues. The variant III mutation of the epidermal growth factor receptor (EGFRvIII) results from an in-frame deletion of a portion of the extracellular domain, creating a neoepitope. We chose a vector backbone encoding a second-generation CAR based on efficacy of a murine scFv-based CAR in a xenograft model of glioblastoma. Next, we generated a panel of humanized scFvs and tested their specificity and function as soluble proteins and in the form of CAR-transduced T cells; a low-affinity scFv was selected on the basis of its specificity for EGFRvIII over wild-type EGFR. The lead candidate scFv was tested in vitro for its ability to direct CAR-transduced T cells to specifically lyse, proliferate, and secrete cytokines in response to antigen-bearing targets. We further evaluated the specificity of the lead CAR candidate in vitro against EGFR-expressing keratinocytes and in vivo in a model of mice grafted with normal human skin. EGFRvIII-directed CAR T cells were also able to control tumor growth in xenogeneic subcutaneous and orthotopic models of human EGFRvIII(+) glioblastoma. On the basis of these results, we have designed a phase 1 clinical study of CAR T cells transduced with humanized scFv directed to EGFRvIII in patients with either residual or recurrent glioblastoma (NCT02209376).

Antiangiogenic ruthenium(ii) benzimidazole complexes, structure-based activation of distinct signaling pathways

A series of ruthenium(ii) benzimidazole complexes has been synthesized and identified as antiangiogenic agents with distinct structure-based action mechanisms.

Update on anti-angiogenic treatment for malignant gliomas

Malignant gliomas are the most common primary brain tumor found in adults. Unfortunately, the prognosis for these type of tumors remains dismal despite aggressive treatment with surgical resection, radiation and chemotherapy. Therefore, therapeutics aimed at disrupting the angiogenesis of these tumors is being utilized in to improve survival outcomes and quality of life. This paper reviews the history of antiangiogenic agents in malignant gliomas, discusses the FDA approval of bevacizumab as monotherapy in recurrent glioblastoma and the subsequent controversy, and analyzes the most recent newly diagnosed trials of RTOG 0825 and AVAglio. Additionally, the results of the latest trials with antiangiogenic agents and possible biomarkers are reviewed. Multiple questions remain regarding the potential benefit of antiangiogenic treatments in patients with glioblastoma. Future clinical trials should be designed to learn more about these drugs, to optimize their future use.

Antiangiogenic therapy for high-grade gliomas: current concepts and limitations

Glioblastoma (GBM) is associated with a high degree of angiogenesis. Therefore, antiangiogenic therapy could have a role in the treatment of this tumor. The currently available treatment approaches acting against angiogenesis are mainly directed toward three pathways: VEGF pathway, VEGF-independent pathways and inhibition of vascular endothelial cell migration. It has been demonstrated that antiangiogenic therapy can produce a rapid radiological response and a decrease of brain edema, without significantly influencing survival. Future studies should consider that: animal models are inadequate and cells used for animal models (mainly U87) are deeply different from patient GBM cells; GBM cells may become resistant to antiangiogenic therapy and some cells may be resistant to antiangiogenic therapy ab initio; and angiogenesis in the peritumor tissue has been poorly investigated. Therefore, the ideal target of angiogenesis is probably yet to be identified.

Dynamic quantitative intravital imaging of glioblastoma progression reveals a lack of correlation between tumor growth and blood vessel density

The spatiotemporal and longitudinal monitoring of cellular processes occurring in tumors is critical for oncological research. We focused on glioblastoma multiforme (GBM), an untreatable highly vascularized brain tumor whose progression is thought to critically depend on the oxygen and metabolites supplied by blood vessels. We optimized protocols for orthotopic GBM grafting in mice that were able to recapitulate the biophysical constraints normally governing tumor progression and were suitable for intravital multiphoton microscopy. We repeatedly imaged tumor cells and blood vessels during GBM development. We established methods for quantitative correlative analyses of dynamic imaging data over wide fields in order to cover the entire tumor. We searched whether correlations existed between blood vessel density, tumor cell density and proliferation in control tumors. Extensive vascular remodeling and the formation of new vessels accompanied U87 tumor cell growth, but no strong correlation was found between local cell density and the extent of local blood vessel density irrespective of the tumor area or time points. The technique moreover proves useful for comparative analysis of mice subjected either to Bevacizumab anti-angiogenic treatment that targets VEGF or to AMD3100, an antagonist of CXCR4 receptor. Bevacizumab treatment massively reduced tumoral vessel densities but only transiently reduced U87 tumor growth rate. Again, there was no correlation between local blood vessel density and local cell density. Moreover, Bev applied only prior to tumor implantation inhibited tumor growth to the same extent as post-grafting treatment. AMD3100 achieved a potent inhibition of tumor growth without significant reduction in blood vessel density. These results indicate that in the brain, in this model, tumor growth can be sustained without an increase in blood vessel density and suggest that GBM growth is rather governed by stromal properties.

Subcurative radiation significantly increases cell proliferation, invasion, and migration of primary glioblastoma multiforme in vivo

Tumor cell proliferation, infiltration, migration, and neovascularization are known causes of treatment resistance in glioblastoma multiforme (GBM). The purpose of this study was to determine the effect of radiation on the growth characteristics of primary human GBM developed in a nude rat. Primary GBM cells grown from explanted GBM tissues were implanted orthotopically in nude rats. Tumor growth was confirmed by magnetic resonance imaging on day 77 (baseline) after implantation. The rats underwent irradiation to a dose of 50 Gy delivered subcuratively on day 84 postimplantation (n = 8), or underwent no radiation (n = 8). Brain tissues were obtained on day 112 (nonirradiated) or day 133 (irradiated). Immunohistochemistry was performed to determine tumor cell proliferation (Ki-67) and to assess the expression of infiltration marker (matrix metalloproteinase-2, MMP-2) and cell migration marker (CD44). Tumor neovascularization was assessed by microvessel density using von-Willebrand factor (vWF) staining. Magnetic resonance imaging showed well-developed, infiltrative tumors in 11 weeks postimplantation. The proportion of Ki-67-positive cells in tumors undergoing radiation was (71 +/- 15)% compared with (25 +/- 12)% in the nonirradiated group (P = 0.02). The number of MMP-2-positive areas and proportion of CD44-positive cells were also high in tumors receiving radiation, indicating great invasion and infiltration. Microvessel density analysis did not show a significant difference between nonirradiated and irradiated tumors. Taken together, we found that subcurative radiation significantly increased proliferation, invasion, and migration of primary GBM. Our study provides insights into possible mechanisms of treatment resistance following radiation therapy for GBM.

Molecular basis for the regulation of angiogenesis by thrombospondin-1 and -2

Thrombospondins TSP-1 and TSP-2 are potent endogenous inhibitors of angiogenesis. They inhibit angiogenesis through direct effects on endothelial cell migration, proliferation, survival, and apoptosis and by antagonizing the activity of VEGF. Several of the membrane receptor systems and signal transduction molecules that mediate the effects of TSP-1 and TSP-2 have been elucidated. TSP-1 and TSP-2 exert their direct effects through CD36, CD47, and integrins. Recent data indicate that CD36 and β1 integrins collaborate to transmit the signals that are initiated by TSP-1 and TSP-2. Furthermore, these receptors appear to associate with VEGFR2 to form a platform for the integration of positive and negative signals for angiogenesis. Cross talk between pro- and antiangiogenic signal transduction pathways may enable TSP-1 and TSP-2 to inhibit angiogenesis by antagonizing survival pathways while also activating apoptotic pathways. CD36 and CD47 are both involved in the suppression of nitric oxide (NO). Advances in understanding of the molecular regulation of angiogenesis by TSP have paved the way for innovations in experimental treatment of cancers and will likely continue to offer vast avenues for discovery in other disease processes as well.

Angiogenesis in neurological disorders: a review

Angiogenesis, recruitment of new blood vessels, is an essential component of the metastatic pathway. These vessels provide the principal route by which tumor cells exit the primary tumor site and enter the circulation. For many tumors, the vascular density can provide a prognostic indicator of metastatic potential, with the highly vascular primary tumors having a higher incidence of metastasis than poorly vascular tumors. The discovery and characterization of tumor-derived angiogenesis modulators greatly contributed to our understanding of how tumors regulate angiogenesis. However, although angiogenesis appears to be a rate-limiting event in tumor growth and metastatic dissemination, a direct connection between the induction of angiogenesis and the progression to tumor malignancy is less well understood. In this review, we discuss the observations concerning the modulation of angiogenesis and their implications in various neurological disorders, as well as their potential impact on cancer therapy.

Towards personalized therapy for patients with glioblastoma

Combined therapy with temozolomide and radiotherapy is a standard treatment and improves the survival for patients with newly diagnosed glioblastoma. However, the prognosis remains poor, with a median survival time of 12-15 months. Currently, several clinical trials of dose-dense temozolomide regimen or molecular-targeting therapies have been performed to overcome the resistance of glioblastoma. In these therapies, rational prognostic biomarkers have also been investigated to predict their outcome and response to treatment. This advanced understanding of the biological markers can help to develop personalized therapies for glioblastoma patients. Generally, due to a reduced tolerance, elderly patients do not seem to benefit from intensive treatment. This population needs individual treatments depended on their age or performance status. In this article, we review the recent studies that can provide personalized therapy for glioblastoma, based on molecular tumor profiling or patients' physical status.

Genetics of glioblastoma: a window into its imaging and histopathologic variability

Glioblastoma is a highly malignant brain tumor that relentlessly defies therapy. Efforts over the past decade have begun to tease out the biochemical details that lead to its aggressive behavior and poor prognosis. There is hope that this new understanding will lead to improved treatment strategies for patients with glioblastoma, in the form of targeted, molecularly based therapies that are individualized to specific changes in individual tumors. However, these new therapies have the potential to fundamentally alter the biologic behavior of glioblastoma and, as a result, its imaging appearance. Knowledge about common genetic alterations and the resultant cellular and tissue changes (ie, induced angiogenesis and abnormal cell survival, proliferation, and invasion) in glioblastomas is important as a basis for understanding imaging findings before treatment. It is equally critical that radiologists understand which genetic pathway is targeted by each specific therapeutic agent or class of agents in order to accurately interpret changes in the imaging appearances of treated tumors.

Glioblastoma multiforme: novel therapeutic approaches

The current therapy for glioblastoma multiforme involves total surgical resection followed by combination of radiation therapy and temozolomide. Unfortunately, the efficacy for such current therapy is limited, and newer approaches are sorely needed to treat this deadly disease. We have recently described the isolation of bacterial proteins and peptides with anticancer activity. In phase I human clinical trials, one such peptide, p28, derived from a bacterial protein azurin, showed partial and complete regression of tumors in several patients among 15 advanced-stage cancer patients with refractory metastatic tumors where the tumors were no longer responsive to current conventional drugs. An azurin-like protein called Laz derived from Neisseria meningitides demonstrates efficient entry and high cytotoxicity towards glioblastoma cells. Laz differs from azurin in having an additional 39-amino-acid peptide called an H.8 epitope, which allows entry and high cytotoxicity towards glioblastoma cells. Since p28 has been shown to have very little toxicity and high anti-tumor activity in advanced-stage cancer patients, it will be worthwhile to explore the use of H.8-p28, H.8-azurin, and Laz in toxicity studies and glioblastoma therapy in preclinical and human clinical trials.

Cell surface receptors in malignant glioma

Despite advances in surgery, radiation, and chemotherapy, malignant gliomas are still highly lethal tumors. Traditional treatments that rely on nonspecific, cytotoxic approaches have a marginal impact on patient survival. However, recent advances in the molecular cancer biology underlying glioma pathogenesis have revealed that abnormalities in common cell surface receptors, including receptor tyrosine kinase and other cytokines, mediate the abnormal cellular signal pathways and aggressive biological behavior among the majority of these tumors. Some cell surface receptors have been targeted by novel agents in preclinical and clinical development. Such cancer-specific targeted agents might offer the promise of improved cancer control without substantial toxicity. Here, we review these common cell surface receptors with clinical significance for malignant glioma and discuss the molecular characteristics, pathological significance, and potential therapeutic application of these cell surface receptors. We also summarize the clinical trials of drugs targeting these cell surface receptors in malignant glioma patients.

Aberrant signaling pathways in glioma

Glioblastoma multiforme (GBM), a WHO grade IV malignant glioma, is the most common and lethal primary brain tumor in adults; few treatments are available. Median survival rates range from 12–15 months. The biological characteristics of this tumor are exemplified by prominent proliferation, active invasiveness, and rich angiogenesis. This is mainly due to highly deregulated signaling pathways in the tumor. Studies of these signaling pathways have greatly increased our understanding of the biology and clinical behavior of GBM. An integrated view of signal transduction will provide a more useful approach in designing novel therapies for this devastating disease. In this review, we summarize the current understanding of GBM signaling pathways with a focus on potential molecular targets for anti-signaling molecular therapies.

Antiangiogenic therapy for patients with recurrent and newly diagnosed malignant gliomas

Malignant gliomas have a poor prognosis despite advances in diagnosis and therapy. Although postoperative temozolomide and radiotherapy improve overall survival in glioblastoma patients, most patients experience a recurrence. The prognosis of recurrent malignant gliomas is dismal, and more effective therapeutic strategies are clearly needed. Antiangiogenesis is currently considered an attractive targeting therapy for malignant gliomas due to its important role in tumor growth. Clinical trials using bevacizumab have been performed for recurrent glioblastoma, and these studies have shown promising response rates along with progression-free survival. Based on the encouraging results, bevacizumab was approved by the FDA for the treatment of recurrent glioblastoma. In addition, bevacizumab has shown to be effective for recurrent anaplastic gliomas. Large phase III studies are currently ongoing to demonstrate the efficacy and safety of the addition of bevacizumab to temozolomide and radiotherapy for newly diagnosed glioblastoma. In contrast, several other antiangiogenic drugs have also been used in clinical trials. However, previous studies have not shown whether antiangiogenesis improves the overall survival of malignant gliomas. Specific severe side effects, difficult assessment of response, and lack of rational predictive markers are challenging problems. Further studies are warranted to establish the optimized antiangiogenesis therapy for malignant gliomas.

Differential analysis of glioblastoma multiforme proteome by a 2D-DIGE approach

Background

Genomics, transcriptomics and proteomics of glioblastoma multiforme (GBM) have recently emerged as possible tools to discover therapeutic targets and biomarkers for new therapies including immunotherapy. It is well known that macroscopically complete surgical excision, radiotherapy and chemotherapy have therapeutic limitations to improve survival in these patients. In this study, we used a differential proteomic-based technique (2D-Difference Gel Electrophoresis) coupled with matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) mass spectrometry to identify proteins that may serve as brain tumor antigens in new therapeutic assays. Five samples of patients presenting a GBM and five samples of microscopically normal brain tissues derived from brain epileptic surgery specimen were labeled and run in 2D-PAGE (Two-Dimensional Polyacrylamide Gel Electrophoresis) with an internal pool sample on each gel. Five gels were matched and compared with DIA (Difference In-gel Analysis) software. Differential spots were picked, in-gel digested and peptide mass fingerprints were obtained.

Results

From 51 protein-spots significantly up-regulated in GBM samples, mass spectrometry (MS) identified twenty-two proteins. The differential expression of a selected protein set was first validated by western-blotting, then tested on large cohorts of GBM specimens and non-tumor tissues, using immunohistochemistry and real-time RT-PCR.

Conclusions

Our results confirmed the importance of previously described proteins in glioma pathology and their potential usefulness as biological markers but also revealed some new interesting targets for future therapies.

Molecular targeting of glioblastoma: Drug discovery and therapies

Despite advances in treatment for glioblastoma multiforme (GBM), patient prognosis remains poor. Although there is growing evidence that molecular targeting could translate into better survival for GBM, current clinical data show limited impact on survival. Recent progress in GBM genomics implicate several activated pathways and numerous mutated genes. This molecular diversity can partially explain therapeutic resistance and several approaches have been postulated to target molecular changes. Furthermore, most drugs are unable to reach effective concentrations within the tumor owing to elevated intratumoral pressure, restrictive vasculature and other limiting factors. Here, we describe the preclinical and clinical developments in treatment strategies of GBM. We review the current clinical trials for GBM and discuss the challenges and future directions of targeted therapies.

Signal transduction inhibitors and antiangiogenic therapies for malignant glioma

Detailed characterization of the cancer genome in a large number of primary human glioblastomas has identified recurrent alterations that result in deregulation of signal transduction pathways and are "druggable" with a growing number of small molecule pharmaceuticals. While many of these compounds have shown clinical activity in other human cancers harboring similar genetic alterations, the clinical experience in glioblastoma has been disappointing thus far with only rare and transient radiographic responses. Our understanding of drug resistance is confounded by the uncertainty of drug delivery across the blood brain barrier and the limited knowledge to what extent the growth of these tumors depends on any particular signaling pathway. This uncertainty is, at least in part, due to shortcomings in the current approach to evaluate signal transduction inhibitors in glioma patients, including drug testing in molecularly unselected patient populations, limited documentation of drug penetration and target inhibition in tumor tissue, and use of radiographic response criteria that may not be optimal for the evaluation of these compounds. © 2011 Wiley-Liss, Inc.

Novel medical therapeutics in glioblastomas, including targeted molecular therapies, current and future clinical trials

The prognosis for glioblastoma is poor despite optimal therapy with surgery, radiation, and chemotherapy. New therapies that improve survival and quality of life are needed. Research has increased our understanding of the molecular pathways important for gliomagenesis and disease progression. Novel agents have been developed against these targets, including receptor tyrosine kinases, intracellular signaling molecules, epigenetic abnormalities, and tumor vasculature and microenvironment. This article reviews novel therapies for glioblastoma, with an emphasis on targeted agents.

Inhibition of brain tumor growth by intravenous poly (β-L-malic acid) nanobioconjugate with pH-dependent drug release [corrected]

Effective treatment of brain neurological disorders such as Alzheimer's disease, multiple sclerosis, or tumors should be possible with drug delivery through blood-brain barrier (BBB) or blood-brain tumor barrier (BTB) and targeting specific types of brain cells with drug release into the cell cytoplasm. A polymeric nanobioconjugate drug based on biodegradable, nontoxic, and nonimmunogenic polymalic acid as a universal delivery nanoplatform was used for design and synthesis of nanomedicine drug for i.v. treatment of brain tumors. The polymeric drug passes through the BTB and tumor cell membrane using tandem monoclonal antibodies targeting the BTB and tumor cells. The next step for polymeric drug action was inhibition of tumor angiogenesis by specifically blocking the synthesis of a tumor neovascular trimer protein, laminin-411, by attached antisense oligonucleotides (AONs). The AONs were released into the target cell cytoplasm via pH-activated trileucine, an endosomal escape moiety. Drug delivery to the brain tumor and the release mechanism were both studied for this nanobiopolymer. Introduction of a trileucine endosome escape unit resulted in significantly increased AON delivery to tumor cells, inhibition of laminin-411 synthesis in vitro and in vivo, specific accumulation in brain tumors, and suppression of intracranial glioma growth compared with pH-independent leucine ester. The availability of a systemically active polymeric drug delivery system that passes through the BTB, targets tumor cells, and inhibits glioma growth gives hope for a successful strategy of glioma treatment. This delivery system with drug release into the brain-specific cell type could be useful for treatment of various brain pathologies.

Antiangiogenic therapies for high-grade glioma

High-grade gliomas (HGGs) are vascular tumors that represent attractive targets for antiangiogenic therapies. In this Review, we present the rationale and clinical trial evidence for targeting angiogenesis in HGGs, focusing predominantly on agents that target vascular endothelial growth factor (VEGF) and its receptors. Bevacizumab, a humanized monoclonal antibody against VEGF, was recently approved by the FDA for treatment of recurrent glioblastoma. Bevacizumab prolongs progression-free survival and controls peritumoral edema, but its effects on overall survival remain to be determined. Other inhibitors of VEGF, VEGF receptors and other proangiogenic signaling pathways are being evaluated. Antiangiogenic therapies are well tolerated, although potentially serious adverse events can occasionally occur, and resistance to antiangiogenic therapy inevitably develops. Mechanisms of resistance include upregulation of alternative proangiogenic pathways, and increased perivascular tumor growth. Tumor progression on antiangiogenic agents is a challenging problem for which no effective salvage therapy has been identified. Combining these agents with radiation therapy, cytotoxic chemotherapy, other targeted molecular agents, or anti-invasion therapies could be helpful. The international Response Assessment in Neuro-Oncology Working Group has developed consensus treatment response criteria for HGG that account for the complex effects of antiangiogenic drugs.