Molecular targeted therapy in recurrent glioblastoma: current challenges and future directions

Liquid biopsy: creating opportunities in brain space

In recent years, liquid biopsy has emerged as an alternative method to diagnose and monitor tumors. Compared to classical tissue biopsy procedures, liquid biopsy facilitates the repetitive collection of diverse cellular and acellular analytes from various biofluids in a non/minimally invasive manner. This strategy is of greater significance for high-grade brain malignancies such as glioblastoma as the quantity and accessibility of tumors are limited, and there are collateral risks of compromised life quality coupled with surgical interventions. Currently, blood and cerebrospinal fluid (CSF) are the most common biofluids used to collect circulating cells and biomolecules of tumor origin. These liquid biopsy analytes have created opportunities for real-time investigations of distinct genetic, epigenetic, transcriptomics, proteomics, and metabolomics alterations associated with brain tumors. This review describes different classes of liquid biopsy biomarkers present in the biofluids of brain tumor patients. Moreover, an overview of the liquid biopsy applications, challenges, recent technological advances, and clinical trials in the brain have also been provided.

Cysteine cathepsin C: a novel potential biomarker for the diagnosis and prognosis of glioma

Background

Cysteine cathepsin C encoded by the CTSC gene is an important member of the cysteine cathepsin family that plays a key role regulation of many types of tumors. However, whether CTSC is involved in the pathological process of glioma has not yet been reported. We comprehensively analyzed data from multiple databases and for the first time revealed a role and specific mechanism of action of CTSC in glioma, identifying it as a novel and efficient biomarker for the diagnosis and treatment of this brain tumor.

Methods

The expression of CTSC in glioma and its relationship with clinical characteristics and prognosis of patients with glioma were analyzed at different levels by using clinical sample information from several databases. CTSC expression levels in glioma and normal brain tissues, as well as in glioma cells and normal brain cells, was validated by real-time quantitative polymerase chain reaction (RT-qPCR). Gene set enrichment analysis (GSEA) was used to reveal the signaling pathways that CTSC may participate in. The connectivity map was used to reveal small molecules that may inhibit CTSC expression in glioma, and the putative effect of these compounds was verified by RT-qPCR.

Results

Our analyses showed that the expression of CTSC in glioma was higher than that in non-cancerous cells. GSEA showed that CTSC expression may regulate the malignant development of glioma through Toll-like receptor signaling pathways, pathways in cancer, and extracellular matrix receptor interaction signaling pathways. And we proved piperlongumine and scopoletin could inhibit CTSC expression in glioma cells.

Conclusions

CTSC may serve as an efficient molecular target for the diagnosis and therapy of glioma, thereby improving the poor prognosis of patients with glioma.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12935-021-02417-6.

Targeted Extracellular Vesicles Delivered Verrucarin A to Treat Glioblastoma

Glioblastomas, accounting for approximately 50% of gliomas, comprise the most aggressive, highly heterogeneous, and malignant brain tumors. The objective of this study was to develop and evaluate a new targeted therapy, i.e., highly potent natural compound verrucarin A (Ver-A), delivered with monoclonal antibody-directed extracellular vesicle (mAb-EV). First, the high surface expression of epidermal growth factor receptor (EGFR) in glioblastoma patient tissue and cell lines was confirmed using immunohistochemistry staining, flow cytometry, and Western blotting. mAb-EV-Ver-A was constructed by packing Ver-A and tagging anti-EGFR mAb to EV generated from HEK293F culture. Confocal microscopy and the In Vivo Imaging System demonstrated that mAb-EV could penetrate the blood-brain barrier, target intracranial glioblastoma xenografts, and deliver drug intracellularly. The in vitro cytotoxicity study showed IC50 values of 2-12 nM of Ver-A. The hematoxylin and eosin staining of major organs in the tolerated dose study indicated minimal systemic toxicity of mAb-EV-Ver-A. Finally, the in vivo anti-tumor efficacy study in intracranial xenograft models demonstrated that EGFR mAb-EV-Ver-A effectively inhibited glioblastoma growth, but the combination with VEGF mAb did not improve the therapeutic efficacy. This study suggested that mAb-EV is an effective drug delivery vehicle and natural Ver-A has great potential to treat glioblastoma.

RNA sequencing of glioblastoma tissue slice cultures reveals the effects of treatment at the transcriptional level

One of the major challenges in cancer research is finding models that closely resemble tumors within patients. Human tissue slice cultures are a promising approach to provide a model of the patient's tumor biology ex vivo. Recently, it was shown that these slices can be successfully analyzed by whole transcriptome sequencing as well as automated histochemistry, increasing their usability as preclinical model. Glioblastoma multiforme (GBM) is a highly malignant brain tumor with poor prognosis and little is known about its genetic background and heterogeneity regarding therapy success. In this study, tissue from the tumors of 25 patients with primary GBM was processed into slice cultures and treated with standard therapy (irradiation and temozolomide). Total RNA sequencing and automated histochemistry were performed to enable analysis of treatment effects at a transcriptional and histological level. Slice cultures from long‐term survivors (overall survival [OS] > 24 months) exhibited more apoptosis than cultures from patients with shorter OS. Proliferation within these slices was slightly increased in contrast to other groups, but not significantly. Among all samples, 58 protein‐coding genes were upregulated and 32 downregulated in treated vs. untreated slice cultures. In general, an upregulation of DNA damage‐related and cell cycle checkpoint genes as well as enrichment of genotoxicity pathways and p53‐dependent signaling was found after treatment. Overall, the current study reproduces knowledge from former studies regarding the feasibility of transcriptomic analyses and automated histology in tissue slice cultures. We further demonstrate that the experimental data merge with the clinical follow‐up of the patients, which improves the applicability of our model system.

Brain Cancer Drug Discovery: Clinical Trials, Drug Classes, Targets, and Combinatorial Therapies

Brain cancer is a formidable challenge for drug development, and drugs derived from many cutting-edge technologies are being tested in clinical trials. We manually characterized 981 clinical trials on brain tumors that were registered in ClinicalTrials.gov from 2010 to 2020. We identified 582 unique therapeutic entities targeting 581 unique drug targets and 557 unique treatment combinations involving drugs. We performed the classification of both the drugs and drug targets based on pharmacological and structural classifications. Our analysis demonstrates a large diversity of agents and targets. Currently, we identified 32 different pharmacological directions for therapies that are based on 42 structural classes of agents. Our analysis shows that kinase inhibitors, chemotherapeutic agents, and cancer vaccines are the three most common classes of agents identified in trials. Agents in clinical trials demonstrated uneven distribution in combination approaches; chemotherapy agents, proteasome inhibitors, and immune modulators frequently appeared in combinations, whereas kinase inhibitors, modified immune effector cells did not as was shown by combination networks and descriptive statistics. This analysis provides an extensive overview of the drug discovery field in brain cancer, shifts that have been happening in recent years, and challenges that are likely to come. SIGNIFICANCE STATEMENT: This review provides comprehensive quantitative analysis and discussion of the brain cancer drug discovery field, including classification of drug, targets, and therapies.

EGFR-Targeted Pentacyclic Triterpene Analogues for Glioma Therapy

Glioma, particularly its most malignant form, glioblastoma multiforme (GBM), is the most common and aggressive malignant central nervous system tumor. The drawbacks of the current chemotherapy for GBM have aroused curiosity in the search for targeted therapies. Aberrantly overexpressed epidermal growth factor receptor (EGFR) in GBM results in poor prognosis, low survival rates, poor responses to therapy and recurrence, and therefore EGFR-targeted therapy stands out as a promising approach for the treatment of gliomas. In this context, a series of pentacyclic triterpene analogues were subjected to in vitro and in silico assays, which were conducted to assess their potency as EGFR-targeted anti-glioma agents. In particular, compound 10 was the most potent anti-glioma agent with an IC₅₀ value of 5.82 µM towards U251 human glioblastoma cells. Taking into account its low cytotoxicity to peripheral blood mononuclear cells (PBMCs), compound 10 exerts selective antitumor action towards Jurkat human leukemic T-cells. This compound also induced apoptosis and inhibited EGFR with an IC₅₀ value of 9.43 µM compared to erlotinib (IC₅₀ = 0.06 µM). Based on in vitro and in silico data, compound 10 stands out as a potential orally bioavailable EGFR-targeted anti-glioma agent endowed with the ability to cross the blood–brain barrier (BBB).

Molecular and Circulating Biomarkers of Brain Tumors

Brain tumors are the most common malignant primary intracranial tumors of the central nervous system. They are often recognized too late for successful therapy. Minimally invasive methods are needed to establish a diagnosis or monitor the response to treatment of CNS tumors. Brain tumors release molecular information into the circulation. Liquid biopsies collect and analyze tumor components in body fluids, and there is an increasing interest in the investigation of liquid biopsies as a substitute for tumor tissue. Tumor-derived biomarkers include nucleic acids, proteins, and tumor-derived extracellular vesicles that accumulate in blood or cerebrospinal fluid. In recent years, circulating tumor cells have also been identified in the blood of glioblastoma patients. In this review of the literature, the authors highlight the significance, regulation, and prevalence of molecular biomarkers such as O₆-methylguanine-DNA methyltransferase, epidermal growth factor receptor, and isocitrate dehydrogenase. Herein, we critically review the available literature on plasma circulating tumor cells (CTCs), cell-free tumors (ctDNAs), circulating cell-free microRNAs (cfmiRNAs), and circulating extracellular vesicles (EVs) for the diagnosis and monitoring of brain tumor. Currently available markers have significant limitations. While much research has been conductedon these markers, there is still a significant amount that we do not yet understand, which may account for some conflicting reports in the literature.

Contralesional Structural Plasticity in Different Molecular Pathologic Subtypes of Insular Glioma

Neuroplasticity may preserve neurologic function in insular glioma, thereby improving prognosis following resection. However, the anatomic and molecular bases of this phenomenon are not known. To address this gap in knowledge, the present study investigated contralesional compensation in different molecular pathologic subtypes of insular glioma by high-resolution three-dimensional T1-weighted structural magnetic resonance imaging. A total of 52 patients with insular glioma were examined. We compared the gray matter volume (GMV) of the contralesional insula according to histological grade [low-grade glioma (LGG) and high-grade glioma (HGG)] and molecular pathology status [isocitrate dehydrogenase (IDH) mutation, telomerase reverse-transcriptase (TERT) promoter mutation, and 1p19q codeletion] by voxel-based morphometry (VBM). A cluster of 320 voxels in contralesional insula with higher GMV was observed in glioma with IDH mutation as compared to IDH wild-type tumors by region of interest-based VBM analysis (family-wise error-corrected at p < 0.05). The GMV of the entire contralesional insula was also larger in insular glioma patients with IDH mutation than in patients with wild-type IDH. However, there was no association between histological grade, TERT promoter mutation, or 1p19q codeletion and GMV in the contralesional insula. Thus, IDH mutation is associated with greater structural compensation in insular glioma. These findings may be useful for predicting neurocognitive and functional outcomes in patients undergoing resection surgery.

Prediction of Lower Grade Insular Glioma Molecular Pathology Using Diffusion Tensor Imaging Metric-Based Histogram Parameters

Objectives

To explore whether a simplified lesion delineation method and a set of diffusion tensor imaging (DTI) metric-based histogram parameters (mean, 25th percentile, 75th percentile, skewness, and kurtosis) are efficient at predicting the molecular pathology status (MGMT methylation, IDH mutation, TERT promoter mutation, and 1p19q codeletion) of lower grade insular gliomas (grades II and III).

Methods

40 lower grade insular glioma patients in two medical centers underwent preoperative DTI scanning. For each patient, the entire abnormal area in their b-non (b0) image was defined as region of interest (ROI), and a set of histogram parameters were calculated for two DTI metrics, fractional anisotropy (FA) and mean diffusivity (MD). Then, we compared how these DTI metrics varied according to molecular pathology and glioma grade, with their predictive performance individually and jointly assessed using receiver operating characteristic curves. The reliability of the combined prediction was evaluated by the calibration curve and Hosmer and Lemeshow test.

Results

The mean, 25th percentile, and 75th percentile of FA were associated with glioma grade, while the mean, 25th percentile, 75th percentile, and skewness of both FA and MD predicted IDH mutation. The mean, 25th percentile, and 75th percentile of FA, and all MD histogram parameters significantly distinguished TERT promoter status. Similarly, all MD histogram parameters were associated with 1p19q status. However, none of the parameters analyzed for either metric successfully predicted MGMT methylation. The 25th percentile of FA yielded the highest prediction efficiency for glioma grade, IDH mutation, and TERT promoter mutation, while the 75th percentile of MD gave the best prediction of 1p19q codeletion. The combined prediction could enhance the discrimination of grading, IDH and TERT mutation, and also with a good fitness.

Conclusions

Overall, more invasive gliomas showed higher FA and lower MD values. The simplified ROI delineation method presented here based on the combination of appropriate histogram parameters yielded a more practical and efficient approach to predicting molecular pathology in lower grade insular gliomas. This approach could help clinicians to determine the extent of tumor resection required and reduce complications, enabling more precise treatment of insular gliomas in combination with radiotherapy and chemotherapy.

Advances in radiotherapy and comprehensive treatment of high-grade glioma: immunotherapy and tumor-treating fields

High-grade gliomas (HGGs) are the most common primary malignant brain tumors. They have a high degree of malignancy and show invasive growth. The personal treatment plan for HGG is based on the patient's age, performance status, and degree of tumor invasion. The basic treatment plan for HGG involves tumor resection, radiotherapy (RT) with concomitant temozolomide (TMZ), and adjuvant TMZ chemotherapy. The basic radiation technology includes conventional RT, three-dimensional conformal RT, intensity-modulated RT, and stereotactic RT. As our understanding of tumor pathogenesis has deepened, so-called comprehensive treatment schemes have attracted attention. These combine RT with chemotherapy, molecular targeted therapy, immunotherapy, or tumor-treating fields. These emerging treatments are expected to improve the prospects of patients with HGG. In the present article, we review the recent advances in RT and comprehensive treatment for patients with newly diagnosed and recurrent HGG.

Gold nanoparticles carrying or not anti-VEGF antibody do not change glioblastoma multiforme tumor progression in mice

Aims

Glioblastoma multiforme (GBM) is the most devastating malignant primary brain tumor known. Life expectance is around 15 months after diagnosis. Several events contribute to the GBM progression such as uncontrolled genetic cancer cells proliferation, angiogenesis (mostly vascular endothelial growth factor (VEGF)-mediated), tissue invasion, glioma stem cell activity, immune system failure, and a hypoxic and inflammatory tumor microenvironment. Tumor cells antiproliferative effect of 20 nm citrate-covered gold nanoparticles (cit-AuNP) has been reported, along with anti-inflammatory and anti-oxidative effects. We aimed to test whether either chronic treatment with 20 nm cit-AuNP or anti-VEGF antibody (Ig)-covered AuNP could reduce GBM progression in mice.

Main methods

Effect of the gold nanoparticles on the GL261 glioblastoma cells proliferation in vitro, and on the GL261-induced glioblastoma cell growth in C57BL/6 mice in vivo were tested. Besides, fluorophore-conjugated gold nanoparticles penetration through the GL261 plasma cell membrane, gold labelling in brain parenchyma of glioblastoma-carrying mice, and VEGF expression into the tumor were evaluated.

Key findings

We observed cit-AuNP did no change the GL261 cells proliferation. Similarly, we demonstrated chronic treatment with either cit-AuNP or anti-VEGF Ig-covered AuNP did not modify the GL261 cells-induced GBM progression in mice. By the end, we showed AuNPs did not trespass in appreciable amount both the GL261 plasma cell membrane and the tumoral blood brain barrier (BBB), and did not change the VEGF expression into the tumor.

Significance

20 nm cit-AuNP or anti-VEGF Ig covered-AuNP are not good tools to reduce GBM in mice, probably because they do not penetrate both tumor cells and BBB in enough amount to reduce tumor growing.

Abnormally high expression of HOXA2 as an independent factor for poor prognosis in glioma patients

In recent years, studies have revealed HOXA2 as a new oncogene, but its function is unknown in gliomas. We aimed to reveal the relationship between HOXA2 and glioma based on the Chinese Glioma Genome Atlas(CGGA) and the cancer genome atlas (TCGA). HOXA2 expression data and clinically relevant information of glioma patients were obtained from the CGGA and TCGA containing 1447 glioma tissues and five non-tumor brain tissues. The Wilcox or Kruskal tests were used to detect the correlation between the HOXA2 expression level and clinical data of glioma patients. the Kaplan-Meier method were used to examine the relationship between HOXA2 and overall patient survival. Gene set enrichment analysis (GSEA) was conducted to indirectly reveal the signaling pathways involved in HOXA2, and RT-PCR was used to detect HOXA2 expression in gliomas and non-tumor brain tissues. High HOXA2 expression was found to be positively correlated with clinical grade, histological type, age, and tumor recurrence, but negatively correlated with 1p19 codeletion and isocitrate dehydrogenase mutation status.RT-PCR results showed that HOXA2 expression levels were significantly higher in tumor tissues than in non-tumor brain tissues. GSEA showed that HOXA2 promoted the activation of the activation of the JAK-STAT-signaling pathway, focal adhesion, cell-adhesion-molecules-CAMS pathway, cytosolic DNA sensing pathway, and natural killer cell-mediated cytotoxicity. This study revealed for the first time that the novel oncogene,HOXA2, leads to poor prognosis in gliomas, and can be used as a biomarker for the diagnosis and treatment of gliomas.

NKG2D Controls Natural Reactivity of Vγ9Vδ2 T Lymphocytes against Mesenchymal Glioblastoma Cells

PURPOSE

Cellular immunotherapies are currently being explored to eliminate highly invasive and chemoradioresistant glioblastoma (GBM) cells involved in rapid relapse. We recently showed that concomitant stereotactic injections of nonalloreactive allogeneic Vγ9Vδ2 T lymphocytes eradicate zoledronate-primed human GBM cells. In the present study, we investigated the spontaneous reactivity of allogeneic human Vγ9Vδ2 T lymphocytes toward primary human GBM cells, in vitro and in vivo, in the absence of any prior sensitization.

EXPERIMENTAL DESIGN

Through functional and transcriptomic analyses, we extensively characterized the immunoreactivity of human Vγ9Vδ2 T lymphocytes against various primary GBM cultures directly derived from patient tumors.

RESULTS

We evidenced that GBM cells displaying a mesenchymal signature are spontaneously eliminated by allogeneic human Vγ9Vδ2 T lymphocytes, a reactivity process being mediated by γδ T-cell receptor (TCR) and tightly regulated by cellular stress-associated NKG2D pathway. This led to the identification of highly reactive Vγ9Vδ2 T lymphocyte populations, independently of a specific TCR repertoire signature. Moreover, we finally provide evidence of immunotherapeutic efficacy in vivo, in the absence of any prior tumor cell sensitization.

CONCLUSIONS

By identifying pathways implicated in the selective natural recognition of mesenchymal GBM cell subtypes, accounting for 30% of primary diagnosed and 60% of recurrent GBM, our results pave the way for novel targeted cellular immunotherapies.

RETRACTED: IP1867B suppresses the insulin-like growth factor 1 receptor (IGF1R) ablating epidermal growth factor receptor inhibitor resistance in adult high grade gliomas

This article has been retracted at the request of the Editor-in-Chief due to concerns regarding the legitimacy of images and data presented in the paper. Though a corrigendum (Can. Lett. Vol. 469, 2020, pages 524-535) was previously published to address some of these concerns, this corrigendum has also been found to contain errors and therefore cannot stand. Specific concerns are listed below. The Editor and Publisher received a letter from the University of Portsmouth alerting us to an investigation into alleged research misconduct. The University concluded their investigation with external experts and determined that misconduct did take place in relation to the research involved in this paper. Upon our separate investigation, it has been determined that the paper headline relies on showing that there was considerable reduction of IGF1R, IL6R and EGFR post treatment in all cell lines. During review, it was determined that this cannot be concluded from the presented data. For example, in SEBTA-003 the EGFR levels go up and there is no difference in IGFR1. It is apparent from Fig 4d that in the SEBTA-003 cell line the EGFR level does not go down, which is stated in the Results section on page 32, it is rather going up. The data for IGFR1 are inconclusive and there are concerns regarding the blot. The general implications would be that the effects of the drug IP1867B does not seem to be the same for all tested cell lines, and this should have been discussed in detail by the authors. Additionally, in subsequent experiments (Fig. 4g and h) the SEBTA-003 cell line (no reduction of EGFR, rather increased expression) and the other 3 cell lines (reduction of EGFR) show similar responses. This is particularly evident in Fig. 4g: Two cell lines are compared, SEBTA-003 (increased EGFR expression) and UP-029 (decreased EGFR expression), both behave similarly after exposure to drugs. The corrigendum (https://doi.org/10.1016/j.canlet.2019.10.002) issue is with respect to the Supplemental Figure 6i EGFR, particularly panel IP1867B. The Corrigendum states that the left part is a cut out of the very right part. If so, the bands for IP1867B should show the same staining pattern - but they do not. Also, in the Corrigendum, there are incorrect mentions between day 14 in the Figure and day 19 in the Figure legend. All authors were informed of the retraction in advance. Drs. Pritchard and Duckworth agreed to the retraction. The corresponding author, Dr Hill, did not agree to the retraction. No response had been received from Drs. Mihajluk, Simms, Reay, Madureira, Howarth, Murray, Nasser and Pilkinton at the time of the retraction being published.

Simultaneous miRNA and mRNA transcriptome profiling of glioblastoma samples reveals a novel set of OncomiR candidates and their target genes

Although glioblastomas are common, there remains a need to elucidate the underlying mechanisms behind their initiation and progression and identify molecular pathways for improving treatment. In this study, sixteen fresh-frozen glioblastoma samples and seven samples of healthy brain tissues were analyzed with miRNA and whole transcriptome microarray chips. Candidate miRNAs and mRNAs were selected to validate expression in fifty patient samples in total with the criteria of abundance, relevance and prediction scores. miRNA and target mRNA relationships were assessed by inhibiting selected miRNAs in glioblastoma cells. Functional tests have been conducted in order to see the effects of miRNAs on invasion, migration and apoptosis of GBM cells. Analyses were carried out to determine correlations between selected molecules and clinicopathological features. 1332 genes and 319 miRNAs were found to be dysregulated by the microarrays. The results were combined and analyzed with Transcriptome Analysis Console 3 software and the DAVID online database. Primary differential pathways included Ras, HIF-1, MAPK signaling and cell adhesion. OncomiR candidates 21-5p, 92b-3p, 182-5p and 339-5p for glioblastoma negatively correlated with notable mRNA targets both in tissues and in in vitro experiments. miR-21-5p and miR-339-5p significantly affected migration, invasion and apoptosis of GBM cells in vitro. Significant correlations with overall survival, tumor volume, recurrence and age at diagnosis were discovered. In this article we present valuable integrated microarray analysis of glioblastoma samples regarding miRNA and gene-expression levels. Notable biomarkers and miRNA-mRNA interactions have been identified, some of which correlated with clinicopathological features in our cohort.

LRIG2 promotes the proliferation and cell cycle progression of glioblastoma cells in vitro and in vivo through enhancing PDGFRβ signaling

The leucine-rich repeats and immunoglobulin-like domains (LRIG) gene family, comprising LRIG1, 2 and 3, encodes integral membrane proteins. It has been well established that LRIG1 negatively regulates multiple growth factor signaling pathways and is considered to be a tumor suppressor; however, the biological functions of LRIG2 remain largely unexplored. It was previously demonstrated that LRIG2 positively regulates epidermal growth factor receptor (EGFR) signaling, the most common aberrant receptor tyrosine kinase (RTK) signaling in glioblastoma multiforme (GBM), which promotes GBM growth. In the present study, the effect of LRIG2 on the proliferation of GBM cells was further addressed, as well as the possible mechanisms underlying the regulatory effect of LRIG2 on platelet-derived growth factor receptor β (PDGFRβ) signaling, another common oncogenic RTK signaling pathway in GBM. First, the expression levels of endogenous LRIG2 and PDGFRβ were found to vary notably in human GBM, and the LRIG2 expression level was positively correlated with the expression level of PDGFRβ. Furthermore, to the best of our knowledge, this is the first study to demonstrate that LRIG2 promoted the PDGF-BB-induced proliferation of GBM cells in vitro and in vivo through regulating the PDGFRβ signaling-mediated cell cycle progression. Mechanistically, LRIG2 has the ability to physically interact with PDGFRβ, promoting the total expression and the activation of PDGFRβ, and enhancing its downstream signaling pathways of Akt and signal transducer and activator of transcription 3 and the effectors of key regulators of cell cycle progression, resulting in increased GBM cell proliferation. Collectively, these data indicated that LRIG2 may serve as a tumor promoter gene in gliomagenesis by positively regulating PDGFRβ signaling, another important oncogenic RTK signaling pathway, in addition to the previously reported EGFR signaling in GBM modulated by LRIG2, and validated LRIG2 as a promising therapeutic target for the treatment of GBM characterized by multiple aberrant RTK signaling.

Molecular Markers of Therapy-Resistant Glioblastoma and Potential Strategy to Combat Resistance

Glioblastoma (GBM) is the most common primary malignant tumor of the central nervous system. With its overall dismal prognosis (the median survival is 14 months), GBMs demonstrate a resounding resilience against all current treatment modalities. The absence of a major progress in the treatment of GBM maybe a result of our poor understanding of both GBM tumor biology and the mechanisms underlying the acquirement of treatment resistance in recurrent GBMs. A comprehensive understanding of these markers is mandatory for the development of treatments against therapy-resistant GBMs. This review also provides an overview of a novel marker called acid ceramidase and its implication in the development of radioresistant GBMs. Multiple signaling pathways were found altered in radioresistant GBMs. Given these global alterations of multiple signaling pathways found in radioresistant GBMs, an effective treatment for radioresistant GBMs may require a cocktail containing multiple agents targeting multiple cancer-inducing pathways in order to have a chance to make a substantial impact on improving the overall GBM survival.

PVT1 affects growth of glioma microvascular endothelial cells by negatively regulating miR-186

Vigorous angiogenesis is one of the reasons for the poor prognosis of glioma. A number of studies have shown that long non-coding RNA can affect a variety of biological behaviors of tumors. However, the influence of long non-coding RNAs on glioma vascular endothelial cells remains unclear. To simulate the glioma microenvironment, we applied glioma-conditioned medium to human cerebral microvascular endothelial cells. The long non-coding RNA PVT1 was found to be highly expressed in glioma vascular endothelial cells. Cell Counting Kit-8, migration, and tube formation assays showed that PVT1 overexpression promoted glioma vascular endothelial cells proliferation, migration, and angiogenesis. We also found that PVT1 overexpression upregulated the expression of the autophagy-related proteins Atg7 and Beclin1, which induced protective autophagy. Bioinformatics software and dual-luciferase system analysis confirmed that PVT1 acts by targeting miR-186. In addition, our study showed that miR-186 could target the 3' untranslated region of Atg7 and Beclin1 to decrease their expression levels, thereby inhibiting glioma-conditioned human cerebral microvascular endothelial cell autophagy. In conclusion, PVT1 overexpression increased the expression of Atg7 and Beclin1 by targeting miR-186, which induced protective autophagy, thus promoting glioma vascular endothelial cell proliferation, migration, and angiogenesis. Therefore, PVT1 and miR-186 can provide new therapeutic targets for future anti-angiogenic treatment of glioma.

Molecular markers in glioma

Gliomas are the most malignant and aggressive form of brain tumors, and account for the majority of brain cancer related deaths. Malignant gliomas, including glioblastoma are treated with radiation and temozolomide, with only a minor benefit in survival time. A number of advances have been made in understanding glioma biology, including the discovery of cancer stem cells, termed glioma stem cells (GSC). Some of these advances include the delineation of molecular heterogeneity both between tumors from different patients as well as within tumors from the same patient. Such research highlights the importance of identifying and validating molecular markers in glioma. This review, intended as a practical resource for both clinical and basic investigators, summarizes some of the more well-known molecular markers (MGMT, 1p/19q, IDH, EGFR, p53, PI3K, Rb, and RAF), discusses how they are identified, and what, if any, clinical relevance they may have, in addition to discussing some of the specific biology for these markers. Additionally, we discuss identification methods for studying putative GSC's (CD133, CD15, A2B5, nestin, ALDH1, proteasome activity, ABC transporters, and label-retention). While much research has been done on these markers, there is still a significant amount that we do not yet understand, which may account for some conflicting reports in the literature. Furthermore, it is unlikely that the investigator will be able to utilize one single marker to prospectively identify and isolate GSC from all, or possibly, any gliomas.

RNaseH2A is involved in human gliomagenesis through the regulation of cell proliferation and apoptosis

Mutations in the RNaseH2A gene are involved in Aicardi‑Goutieres syndrome, an autosomal recessive neurological dysfunction; however, studies assessing RNaseH2A in relation to glioma are scarce. This study aimed to assess the role of RNaseH2A in glioma and to unveil the underlying mechanisms. RNaseH2A was silenced in glioblastoma cell lines U87 and U251. Gene expression was assessed in the cells transfected with RNaseH2A shRNA or scramble shRNA by microarrays, validated by quantitative real time PCR. Protein expression was evaluated by western blot analysis. Cell proliferation was assessed by the MTT assay; cell cycle distribution and apoptosis were analyzed by flow cytometry. Finally, the effects of RNaseH2A on colony formation and tumorigenicity were assessed in vitro and in a mouse xenograft model, respectively. RNaseH2A was successively knocked down in U87 and U251 cells. Notably, RNaseH2A silencing resulted in impaired cell proliferation, with 70.7 and 57.8% reduction in the U87 and U251 cells, respectively, with the cell cycle being blocked in the G0/G1 phase in vitro. Meanwhile, clone formation was significantly reduced by RNaseH2A knockdown, which also increased cell apoptosis by approximately 4.5-fold. In nude mice, tumor size was significantly decreased after RNaseH2A knockdown: 219.29±246.43 vs. 1160.26±222.61 mm3 for the control group; similar findings were obtained for tumor weight (0.261±0.245 and 1.127±0.232 g) in the shRNA and control groups, respectively). In the microarray data, RNaseH2A was shown to modulate several signaling pathways responsible for cell proliferation and apoptosis, such as IL-6 and FAS pathways. RNaseH2A may be involved in human gliomagenesis, likely by regulating signaling pathways responsible for cell proliferation and apoptosis.

Noninvasive brain cancer imaging with a bispecific antibody fragment, generated via click chemistry

Early diagnosis remains a task of upmost importance for reducing cancer morbidity and mortality. Successful development of highly specific companion diagnostics targeting aberrant molecular pathways of cancer is needed for sensitive detection, accurate diagnosis, and opportune therapeutic intervention. Herein, we generated a bispecific immunoconjugate [denoted as Bs-F(ab)2] by linking two antibody Fab fragments, an anti-epidermal growth factor receptor (EGFR) Fab and an anti-CD105 Fab, via bioorthogonal "click" ligation of trans-cyclooctene and tetrazine. PET imaging of mice bearing U87MG (EGFR/CD105(+/+)) tumors with (64)Cu-labeled Bs-F(ab)2 revealed a significantly enhanced tumor uptake [42.9 ± 9.5 percentage injected dose per gram (%ID/g); n = 4] and tumor-to-background ratio (tumor/muscle ratio of 120.2 ± 44.4 at 36 h postinjection; n = 4) compared with each monospecific Fab tracer. Thus, we demonstrated that dual targeting of EGFR and CD105 provides a synergistic improvement on both affinity and specificity of (64)Cu-NOTA-Bs-F(ab)2. (64)Cu-NOTA-Bs-F(ab)2 was able to visualize small U87MG tumor nodules (<5 mm in diameter), owing to high tumor uptake (31.4 ± 10.8%ID/g at 36 h postinjection) and a tumor/muscle ratio of 76.4 ± 52.3, which provided excellent sensitivity for early detection. Finally, we successfully confirmed the feasibility of a ZW800-1-labeled Bs-F(ab)2 for near-infrared fluorescence imaging and image-guided surgical resection of U87MG tumors. More importantly, our rationale can be used in the construction of other disease-targeting bispecific antibody fragments for early detection and diagnosis of small malignant lesions.

Tetrandrine suppresses human glioma growth by inhibiting cell survival, proliferation and tumour angiogenesis through attenuating STAT3 phosphorylation

Tetrandrine (Tet), a bisbenzylisoquinoline alkaloid, has been reported to possess anti-tumour activity. However, its effects on human glioma remain unknown. In this study, we demonstrated that Tet inhibited human glioma cell growth in vitro and in vivo. It has been hypothesised that Tet inhibits glioma growth by affecting glioma cell survival, proliferation and vasculature in and around the xenograft tumour in the chick CAM model and signal transducer and activator of transcription 3 (STAT3) mediated these activities. Therefore, we conducted a detailed analysis of the inhibitory effects of Tet on cell survival using a TUNEL assay and flow cytometric analysis; on cell proliferation based on the expression of proliferating cell nuclear antigen; and on angiogenesis using a CAM anti-angiogenesis assay. We used western blotting to investigate the role of STAT3 on the anti-glioma activities of Tet. The results revealed that Tet inhibited survival and proliferation in human glioma cells, impaired tumour angiogenesis and decreased the expression of phosphorylated STAT3 and its downstream proteins. In sum, our data indicate that STAT3 is involved in Tet-induced the regression of glioma growth by activating tumour cell apoptosis, inhibiting glioma cell proliferation and inhibiting angiogenesis.

Molecular and genetic pathways in gliomas: the future of personalized therapeutics

In the last few decades, we have seen significant advances in brain imaging, which have resulted in more detailed anatomic and functional localization of gliomas in relation to the eloquent cortex, as well as improvements in microsurgical techniques and enhanced delivery of adjuvant stereotactic radiation. While these advancements have led to a relatively modest improvement in clinical outcomes for patients with malignant gliomas, much more work remains to be done. As with other types of cancer, we are now rapidly moving past the era of histopathology dictating treatment for brain tumors and into the realm of molecular diagnostics and associated targeted therapies, specifically based on the genomic architecture of individual gliomas. In this review, we discuss the current era of molecular glioma characterization and how these profiles will allow for individualized, patient-specific targeted treatments.

Molecular heterogeneity in glioblastoma: potential clinical implications

Glioblastomas, (grade 4 astrocytomas), are aggressive primary brain tumors characterized by histopathological heterogeneity. High-resolution sequencing technologies have shown that these tumors also feature significant inter-tumoral molecular heterogeneity. Molecular subtyping of these tumors has revealed several predictive and prognostic biomarkers. However, intra-tumoral heterogeneity may undermine the use of single biopsy analysis for determining tumor genotype and has implications for potential targeted therapies. The clinical relevance and theories of tumoral molecular heterogeneity in glioblastoma are discussed.

The Efficacy of Ketogenic Diet and Associated Hypoglycemia as an Adjuvant Therapy for High-Grade Gliomas: A Review of the Literature

Background: A high-fat, low-carbohydrate diet, often referred to as a ketogenic diet (KD), has been suggested to reduce frequency and severity of chronic pediatric and adult seizures. A hypoglycemic state, perpetuated by administration of a KD, has been hypothesized as a potential aid to the current standard treatments of high-grade gliomas.

Methods: To understand the effectiveness of the ketogenic diet as a therapy for malignant gliomas, studies analyzing components of a KD were reviewed. Both preclinical and clinical studies were included. The keywords “ketogenic diet, GBM, malignant glioma, hyperglycemia, hypoglycemia” were utilized to search for both abstracts and full articles in English. Overall, 39 articles were found and included in this review.

Results: Studies in animal models showed that a KD is able to control tumor growth and increase overall survival. Other pre-clinical studies have suggested that a KD sustains an environment in which tumors respond better to standard treatments, such as chemoradiation. In human cohorts, the KD was well tolerated. Quality of life was improved, compared to a standard, non-calorie or carbohydrate restricted diet. Hyperglycemia was independently associated with diminished survival.

Conclusion: Recent clinical findings have demonstrated that induced hypoglycemia and ketogenic diet are tolerable and can potentially be an adjuvant to standard treatments, such as surgery and chemoradiation. Other findings have advocated for KD as a malignant cell growth inhibitor, and indicate that further studies analyzing larger cohorts of GBM patients treated with a KD are needed to determine the breadth of impact a KD can have on GBM treatment.

Chlorotoxin-conjugated onconase as a potential anti-glioma drug

Gliomas are rarely curable malignant brain tumors arising from normal glial cells. The scorpion-derived small peptide, chlorotoxin (CTX), can selectively bind malignant gliomas. In the present study, a CTX-conjugated onconase (Onc), a small cytotoxic ribonuclease, was prepared as a potential anti-glioma drug. In this conjugate, recombinant CTX was covalently linked with recombinant Onc by reversible disulfide linkage. The chemically conjugated CTX-Onc showed much higher cytotoxicity to the cultured glioma U251 and SHG-44 cells than the physical mixture of CTX and Onc (CTX + Onc). In the nude mouse models bearing subcutaneous U251 or SHG-44 tumors, the CTX-Onc conjugate also showed improved anti-tumor effects than the CTX + Onc control. These results suggested that the reversible chemical-conjugated CTX promoted the tumor targeting of Onc, and thus the present CTX-Onc conjugate could be further developed as a potential targeted anti-glioma drug.

Surgical delivery of drug releasing poly(lactic-co-glycolic acid)/poly(ethylene glycol) paste with in vivo effects against glioblastoma

INTRODUCTION

The median survival of patients with glioblastoma multiforme (astrocytoma grade 4) remains less than 18 months despite radical surgery, radiotherapy and systemic chemotherapy. Surgical implantation of chemotherapy eluting wafers into the resection cavity has been shown to improve length of survival but the current licensed therapy has several drawbacks. This paper investigates in vivo efficacy of a novel drug eluting paste in glioblastoma.

METHODS

Poly(lactic-co-glycolic acid)/poly(ethylene glycol) (PLGA/PEG) self-sintering paste was loaded with the chemotherapeutic agent etoposide and delivered surgically into partially resected tumours in a flank murine glioblastoma xenograft model.

RESULTS

Surgical delivery of the paste was successful and practical, with no toxicity or surgical morbidity to the animals. The paste was retained in the tumour cavity, and preliminary results suggest a useful antitumour and antiangiogenic effect, particularly at higher doses. Bioluminescent imaging was not affected significantly by the presence of the paste in the tumour.

CONCLUSIONS

Chemotherapy loaded PLGA/PEG paste seems to be a promising technology capable of delivering active drugs into partially resected tumours. The preliminary results of this study suggest efficacy with no toxicity and will lead to larger scale efficacy studies in orthotopic glioblastoma models.

Glioblastoma multiforme: State of the art and future therapeutics

BACKGROUND

Glioblastoma multiforme (GBM) is the most common and lethal primary malignancy of the central nervous system (CNS). Despite the proven benefit of surgical resection and aggressive treatment with chemo- and radiotherapy, the prognosis remains very poor. Recent advances of our understanding of the biology and pathophysiology of GBM have allowed the development of a wide array of novel therapeutic approaches, which have been developed. These novel approaches include molecularly targeted therapies, immunotherapies, and gene therapy.

METHODS

We offer a brief review of the current standard of care, and a survey of novel therapeutic approaches for treatment of GBM.

RESULTS

Despite promising results in preclinical trials, many of these therapies have demonstrated limited therapeutic efficacy in human clinical trials. Thus, although survival of patients with GBM continues to slowly improve, treatment of GBM remains extremely challenging.

CONCLUSION

Continued research and development of targeted therapies, based on a detailed understanding of molecular pathogenesis can reasonably be expected to yield improved outcomes for patients with GBM.

The ketogenic diet for the treatment of malignant glioma

Advances in our understanding of glioma biology has led to an increase in targeted therapies in preclinical and clinical trials; however, cellular heterogeneity often precludes the targeted molecules from being found on all glioma cells, thus reducing the efficacy of these treatments. In contrast, one trait shared by virtually all tumor cells is altered (dysregulated) metabolism. Tumor cells have an increased reliance on glucose, suggesting that treatments affecting cellular metabolism may be an effective method to improve current therapies. Indeed, metabolism has been a focus of cancer research in the last few years, as many pathways long associated with tumor growth have been found to intersect metabolic pathways in the cell. The ketogenic diet (high fat, low carbohydrate and protein), caloric restriction, and fasting all cause a metabolic change, specifically, a reduction in blood glucose and an increase in blood ketones. We, and others, have demonstrated that these metabolic changes improve survival in animal models of malignant gliomas and can potentiate the anti-tumor effect of chemotherapies and radiation treatment. In this review we discuss the use of metabolic alteration for the treatment of malignant brain tumors.

Mesenchymal stem cells show little tropism for the resting and differentiated cancer stem cell-like glioma cells

Intrinsic resistance of glioma cells to radiation and chemotherapy is currently hypothesized to be partially attributed to the existence of cancer stem cells. Emerging studies suggest that mesenchymal stem cells may serve as a potential carrier for delivery of therapeutic genes to disseminated glioma cells. However, the tropism character of mesenchymal stem cells for cancer stem cell-like glioma cells has rarely been described. In this study, we obtained homologous bone marrow-derived (BM-) and adipose tissue-derived (AT-) mesenchymal stem cells (MSCs), fibroblast, and cancer stem cell-like glioma cells (CSGCs) from tumor-bearing mice, and compared the tropism character of BM- and AT-MSCs for CSGCs with various form of existence. To characterize the cell proliferation and differentiation, the spheroids of CSGCs were cultured on the surface of the substrate with different stiffness, combined with or withdrew basic fibroblast growth factor (bFGF) and epidermal growth factor (EGF) in medium. Our results showed that the CSGCs during the process of cell proliferation, but not in resting and differentiated status, display strong tropism characteristics on both BM- and AT-MSCs, as well as the expression of their cell chemokine factors which mediate cell migration. If the conclusion is further confirmed, it may expose a fatal flaw of MSCs as tumor-targeted delivery of therapeutic agents in the treatment of the CSGCs, even other cancer stem cells, because there always exist a part of cancer stem cells that are in resting status. Overall, our findings provide novel insight into the complex issue of the MSCs as drug delivery in the treatment of brain tumors, especially in tumor stem cells.

An update on vaccine therapy and other immunotherapeutic approaches for glioblastoma

Outcome for glioblastoma (GBM), the most common primary CNS malignancy, remains poor. The overall survival benefit recently achieved with immunotherapeutics for melanoma and prostate cancer support evaluation of immunotherapies for other challenging cancers, including GBM. Much historical dogma depicting the CNS as immunoprivileged has been replaced by data demonstrating CNS immunocompetence and active interaction with the peripheral immune system. Several glioma antigens have been identified for potential immunotherapeutic exploitation. Active immunotherapy studies for GBM, supported by preclinical data, have focused on tumor lysate and synthetic antigen vaccination strategies. Results to date confirm consistent safety, including a lack of autoimmune reactivity; however, modest efficacy and variable immunogenicity have been observed. These findings underscore the need to optimize vaccination variables and to address challenges posed by systemic and local immunosuppression inherent to GBM tumors. Additional immunotherapy strategies are also in development for GBM. Future studies may consider combinatorial immunotherapy strategies with complimentary actions.

p38γ overexpression in gliomas and its role in proliferation and apoptosis

The objective of this study was to confirm the biological role of p38γ in human gliomas. The expression profiles of p38γ and hTERT in human glioma samples were detected by Western Blot and immunohistochemistry. RNA interference was performed in U251 cells by p38γ silencing. Cell proliferation and apoptosis were assayed by CCK-8 and flow cytometric analysis, and then RNA and protein expression levels were measured by real-time RT-PCR and Western Blot, respectively. Telomerase activity assays and Caspase-3,-9 activation assays were also conducted. The results showed p38γ had a positive correlation with the glioma's malignancy grade and that the treatment of U251 cells with p38γ-siRNA inhibited proliferation and induced apoptosis. Correspondingly, hTERT expression and telomerase activity were down regulated and Caspase-3 and -9 activities were elevated. In conclusion, p38γ may serve as an oncogenic factor promoting the growth and progression of gliomas and may become a useful therapeutic target.

Targeted antiepidermal growth factor receptor (cetuximab) immunoliposomes enhance cellular uptake in vitro and exhibit increased accumulation in an intracranial model of glioblastoma multiforme

Therapeutic advances do not circumvent the devastating fact that the survival rate in glioblastoma multiforme (GBM) is less than 5%. Nanoparticles consisting of liposome-based therapeutics are provided against a variety of cancer types including GBM, but available liposomal formulations are provided without targeting moieties, which increases the dosing demands to reach therapeutic concentrations with risks of side effects. We prepared PEGylated immunoliposomes (ILs) conjugated with anti-human epidermal growth factor receptor (EGFR) antibodies Cetuximab (α-hEGFR-ILs). The affinity of the α-hEGFR-ILs for the EGF receptor was evaluated in vitro using U87 mg and U251 mg cells and in vivo using an intracranial U87 mg xenograft model. The xenograft model was additionally analyzed with respect to permeability to endogenous albumin, tumor size, and vascularization. The in vitro studies revealed significantly higher binding of α-hEGFR-ILs when compared with liposomes conjugated with isotypic nonimmune immunoglobulin. The uptake and internalization of the α-hEGFR-ILs by U87 mg cells were further confirmed by 3D deconvolution analyses. In vivo, the α-hEGFR-ILs accumulated to a higher extent inside the tumor when compared to nonimmune liposomes. The data show that α-hEGFR-ILs significantly enhance the uptake and accumulation of liposomes in this experimental model of GBM suggestive of improved specific nanoparticle-based delivery.

Nitrone-based therapeutics for neurodegenerative diseases: their use alone or in combination with lanthionines

The possibility of free radical reactions occurring in biological processes led to the development and employment of novel methods and techniques focused on determining their existence and importance in normal and pathological conditions. For this reason the use of nitrones for spin trapping free radicals became widespread in the 1970s and 1980s, when surprisingly the first evidence of their potent biological properties was noted. Since then widespread exploration and demonstration of the potent biological properties of phenyl-tert-butylnitrone (PBN) and its derivatives took place in preclinical models of septic shock and then in experimental stroke. The most extensive commercial effort made to capitalize on the potent properties of the PBN-nitrones was for acute ischemic stroke. This occurred during 1993-2006, when the 2,4-disulfonylphenyl PBN derivative, called NXY-059 in the stroke studies, was shown to be safe in humans and was taken all the way through clinical phase 3 trials and then was deemed to be ineffective. As summarized in this review, because of its excellent human safety profile, 2,4-disulfonylphenyl PBN, now called OKN-007 in the cancer studies, was tested as an anti-cancer agent in several preclinical glioma models and shown to be very effective. Based on these studies this compound is now scheduled to enter into early clinical trials for astrocytoma/glioblastoma multiforme this year. The potential use of OKN-007 in combination with neurotropic compounds such as the lanthionine ketamine esters is discussed for glioblastoma multiforme as well as for various other indications leading to dementia, such as aging, septic shock, and malaria infections. There is much more research and development activity ongoing for various indications with the nitrones, alone or in combination with other active compounds, as briefly noted in this review.

Vaccinia virus expressing bone morphogenetic protein-4 in novel glioblastoma orthotopic models facilitates enhanced tumor regression and long-term survival

Background

Glioblastoma multiforme (GBM) is one of the most aggressive forms of cancer with a high rate of recurrence. We propose a novel oncolytic vaccinia virus (VACV)-based therapy using expression of the bone morphogenetic protein (BMP)-4 for treating GBM and preventing recurrence.

Methods

We have utilized clinically relevant, orthotopic xenograft models of GBM based on tumor-biopsy derived, primary cancer stem cell (CSC) lines. One of the cell lines, after being transduced with a cDNA encoding firefly luciferase, could be used for real time tumor imaging. A VACV that expresses BMP-4 was constructed and utilized for infecting several primary glioma cultures besides conventional serum-grown glioma cell lines. This virus was also delivered intracranially upon implantation of the GBM CSCs in mice to determine effects on tumor growth.

Results

We found that the VACV that overexpresses BMP-4 demonstrated heightened replication and cytotoxic activity in GBM CSC cultures with a broad spectrum of activity across several different patient-biopsy cultures. Intracranial inoculation of mice with this virus resulted in a tumor size equal to or below that at the time of injection. This resulted in survival of 100% of the treated mice up to 84 days post inoculation, significantly superior to that of a VACV lacking BMP-4 expression. When mice with a higher tumor burden were injected with the VACV lacking BMP-4, 80% of the mice showed tumor recurrence. In contrast, no recurrence was seen when mice were injected with the VACV expressing BMP-4, possibly due to induction of differentiation in the CSC population and subsequently serving as a better host for VACV infection and oncolysis. This lack of recurrence resulted in superior survival in the BMP-4 VACV treated group.

Conclusions

Based on these findings we propose a novel VACV therapy for treating GBM, which would allow tumor specific production of drugs in the future in combination with BMPs which would simultaneously control tumor maintenance and facilitate CSC differentiation, respectively, thereby causing sustained tumor regression without recurrence.

Spinal cord tumours: advances in genetics and their implications for treatment

Tumours of the spinal cord, although rare, are associated with high morbidity. Surgical resection remains the primary treatment for patients with this disease, and offers the best chance for cure. Such surgical procedures, however, carry substantial risks such as worsening of neurological deficit, paralysis and death. New therapeutic avenues for spinal cord tumours are needed, but genetic studies of the molecular mechanisms governing tumourigenesis in the spinal cord are limited by the scarcity of high-quality human tumour samples. Many spinal cord tumours have intracranial counterparts that have been extensively studied, but emerging data show that the tumours are genetically and biologically distinct. The differences between brain and spine tumours make extrapolation of data from one to the other difficult. In this Review, we describe the demographics, genetics and current treatment approaches for the most commonly encountered spinal cord tumours--namely, ependymomas, astrocytomas, haemangioblastomas and meningiomas. We highlight advances in understanding of the biological basis of these lesions, and explain how the latest progress in genetics and beyond are being translated to improve patient care.

Interleukins in glioblastoma pathophysiology: implications for therapy

Despite considerable amount of research, the poor prognosis of patients diagnosed with glioblastoma multiforme (GBM) critically needs new drug development to improve clinical outcomes. The development of an inflammatory microenvironment has long been considered important in the initiation and progression of glioblastoma; however, the success of developing therapeutic approaches to target inflammation for GBM therapy has yet been limited. Here, we summarize the accumulating evidence supporting a role for inflammation in the pathogenesis of glioblastoma, discuss anti-inflammatory targets that could be relevant for GBM treatment and provide a perspective on the challenges faced in the development of drugs that target GBM inflammation. In particular, we will review the function of IL-1β, IL-6 and IL-8 as well as the potential of kinase inhibitors targeting key players in inflammatory cell signalling cascades such as JAK, JNK and p38 MAPK.

Biological and clinical implications of cancer stem cells in primary brain tumors

Despite therapeutic advances, glioblastoma multiforme (GBM) remains a lethal disease. The infiltrative nature of this disease and the presence of a cellular population resistant to current medical treatments account for the poor prognosis of these patients. Growing evidence indicates the existence of a fraction of cancer cells sharing the functional properties of adult stem cells, including self-renewal and a greater ability to escape chemo-radiotherapy-induced death stimuli. Therefore, these cells are commonly defined as cancer stem cells (GBM-SCs). The initial GBM-SC concept has been challenged, and refined according to the emerging molecular taxonomy of GBM. This allowed to postulate the existence of multiple CSC types, each one driving a given molecular entity. Furthermore, it is becoming increasingly clear that GBM-SCs thrive through a dynamic and bidirectional interaction with the surrounding microenvironment. In this article, we discuss recent advances in GBM-SC biology, mechanisms through which these cells adapt to hostile conditions, pharmacological strategies for selectively killing GBM-SCs, and how novel CSC-associated endpoints have been investigated in the clinical setting.

Therapeutic application of monoclonal antibodies in cancer: advances and challenges

INTRODUCTION

Monoclonal antibody (mAb)-based products are highly specific for a particular antigen. This characteristic feature of the molecules makes them an ideal tool for many applications including cancer diagnosis and therapy.

SOURCES OF DATA

We performed comprehensive searches of PubMed, Medline and the Food and Drug Administration website using keywords such as 'therapeutic antibodies' and 'anti-cancer antibodies'.

AREAS OF AGREEMENT

Treatment of cancer patients with antibodies when used alone or in combination with chemotherapy and radiotherapy, or conjugated to drugs or radioisotopes, prolongs overall survival in cancer patients. Currently, there are 14 mAb-based drugs that have been approved for the treatment of cancer patients.

AREAS OF CONTROVERSY

The response of cancer patients to antibody therapy can be of short duration. Therapeutic antibodies are expensive and may have side effects. There are no reliable predictive biomarkers for sensitivity or resistance to certain therapeutic antibodies. FUTURE FOCUS: There should be additional studies to discover novel therapeutic targets, to develop more effective antibody-based drugs with fewer side effects, to identify more reliable predictive biomarker(s) for response to therapy with antibody-based drugs and to develop alternative strategies (e.g. transgenic plants, transgenic farm animals) for production of large quantities and more affordable batches of therapeutic antibodies.

AREAS TIMELY FOR DEVELOPING RESEARCH

A better understanding of cancer biology, the hallmarks of human cancers and the immune system would lead to identification of additional cell surface biomarkers. These in turn would facilitate the development of novel and biosimilar antibody-based drugs and their routine use as 'magic bullets' for the targeted therapy of human cancers.