Glioblastoma multiforme: Pathogenesis and treatment

Ultrasound Enhanced Anti-tumor Effect of Temozolomide in Glioblastoma Cells and Glioblastoma Mouse Model

Introduction

Glioblastoma is the most aggressive cancer that begins within the brain. In clinic, temozolomide was used as anti-tumor drugs for glioblastoma chemotherapy, but showed limited effect. Therefore, how to improve the effect of temozolomide to glioblastoma is urgently needed.

Methods

The cell viability of T98G cells was detected by cell counting kit-8 (CCK-8) assay. Apoptosis was detected using the Annexin-V-FITC & PI apoptosis kit and assessed by flow cytometry. The expression levels of Bax, B cell lymphoma 2 (Bcl-2), phos-Jun N-terminal kinases (JNK), phos-extracellular signal-regulated kinases (ERK) and phos-p38 were determined by western blot. The effect of ultrasound and temozolomide combination in mice was determined by survival analysis.

Results

Compared with temozolomide treatment alone, ultrasound and temozolomide combination inhibited the cell viability, and promotes apoptosis of human glioblastoma T98G cells. Bax level increased, while Bcl-2 level decreased in combination group. Mechanically, combination treatment promoted apoptosis via JNK and p38 pathways. In mouse glioblastoma model, combination treatment improved overall survival.

Conclusions

Ultrasound enhanced anti-tumor effect of temozolomide in glioblastoma cells via JNK and p38 pathways.

Exosomal Chaperones and miRNAs in Gliomagenesis: State-of-Art and Theranostics Perspectives

Gliomas have poor prognosis no matter the treatment applied, remaining an unmet clinical need. As background for a substantial change in this situation, this review will focus on the following points: (i) the steady progress in establishing the role of molecular chaperones in carcinogenesis; (ii) the recent advances in the knowledge of miRNAs in regulating gene expression, including genes involved in carcinogenesis and genes encoding chaperones; and (iii) the findings about exosomes and their cargo released by tumor cells. We would like to trigger a discussion about the involvement of exosomal chaperones and miRNAs in gliomagenesis. Chaperones may be either targets for therapy, due to their tumor-promoting activity, or therapeutic agents, due to their antitumor growth activity. Thus, chaperones may well represent a Janus-faced approach against tumors. This review focuses on extracellular chaperones as part of exosomes' cargo, because of their potential as a new tool for the diagnosis and management of gliomas. Moreover, since exosomes transport chaperones and miRNAs (the latter possibly related to chaperone gene expression in the recipient cell), and probably deliver their cargo in the recipient cells, a new area of investigation is now open, which is bound to generate significant advances in the understanding and treatment of gliomas.

Theranostic nanosensitizers for highly efficient MR/fluorescence imaging-guided sonodynamic therapy of gliomas

Glioma is the most frequent primary brain tumour of the central nervous system. Its high aggressiveness and deep‐seated brain lesion make it a great challenge to develop a non‐invasive, precise and effective treatment approach. Here, we report a multifunctional theranostic agent that can integrate imaging and therapy into a single nano‐platform for imaging‐guided sonodynamic therapy (SDT). The SDT agents were fabricated by encapsulation of sinoporphyrin sodium (DVDMS) chelating with manganese ions into nanoliposomes (DVDMS‐Mn‐LPs). DVDMS‐Mn‐LPs are physiologically stable and biologically compatible, and they can produce singlet oxygen upon ultrasound irradiation to kill cancer cells. Both cell and animal studies demonstrated that SDT with DVDMS‐Mn‐LPs can significantly improve the antitumour growth efficiency even in the presence of skull. In addition, DVDMS‐Mn‐LPs are good for MR and fluorescence imaging. Thus, DVDMS‐Mn‐LPs reported here may provide a promising strategy for imaging‐guided modality for glioma treatment.

Immunomodulation Mediated by Anti-angiogenic Therapy Improves CD8 T Cell Immunity Against Experimental Glioma

Glioblastoma (GBM) is a lethal cancer of the central nervous system with a median survival rate of 15 months with treatment. Thus, there is a critical need to develop novel therapies for GBM. Immunotherapy is emerging as a promising therapeutic strategy. However, current therapies for GBM, in particular anti-angiogenic therapies that block vascular endothelial growth factor (VEGF), may have undefined consequences on the efficacy of immunotherapy. While this treatment is primarily prescribed to reduce tumor vascularization, multiple immune cell types also express VEGF receptors, including the most potent antigen-presenting cell, the dendritic cell (DC). Therefore, we assessed the role of anti-VEGF therapy in modifying DC function. We found that VEGF blockade results in a more mature DC phenotype in the brain, as demonstrated by an increase in the expression of the co-stimulatory molecules B7-1, B7-2, and MHC II. Furthermore, we observed reduced levels of the exhaustion markers PD-1 and Tim-3 on brain-infiltrating CD8 T cells, indicating improved functionality. Thus, anti-angiogenic therapy has the potential to be used in conjunction with and enhance immunotherapy for GBM.

Iron(II)-Polypyridyl Complexes Inhibit the Growth of Glioblastoma Tumor and Enhance TRAIL-Induced Cell Apoptosis

A promising cancer-targeting agent for the induction of apoptosis in tumor necrosis factor (TNF) proteins, the TNF-related apoptosis-inducing ligand (TRAIL) ligand, has found limited applications in the treatment of cancer cells, owing to its resistance by cancer cell lines. Therefore, the rational design of anticancer agents that could sensitize cancer cells towards TRAIL is of great significance. Herein, we report that synthetic iron(II)-polypyridyl complexes are capable of inhibiting the proliferation of glioblastoma cancer cells and efficiently enhancing TRAIL-induced cell apoptosis. Mechanistic studies demonstrated that the synthesized complexes induced cancer-cell apoptosis through triggering the activation of p38 and p53 and inhibiting the activation of ERK. Moreover, uPA and MMP-2/MMP-9, among the most important metastatic regulatory proteins, were also found to be significantly alerted after the treatment. Furthermore, we also found that tumor growth in nude mice was significantly inhibited by iron complex Fe2 through the induction of apoptosis without clear systematic toxicity, as indicated by histological analysis. Taken together, this study provides evidence for the further development of metal-based anticancer agents and chemosensitizers of TRAIL for the treatment of human glioblastoma cancer cells.

Lycorine inhibits glioblastoma multiforme growth through EGFR suppression

Background

Lycorine has been revealed to inhibit the development of many kinds of malignant tumors, including glioblastoma multiforme (GBM). Although compelling evidences demonstrated Lycorine’s inhibition on cancers through some peripheral mechanism, in-depth mechanism studies of Lycotine’s anti-GBM effects still call for further exploration. Epidermal Growth Factor Receptor (EGFR) gene amplification and mutations are the most common oncogenic events in GBM. Targeting EGFR by small molecular inhibitors is a rational strategy for GBM treatment.

Methods

The molecular docking modeling and in vitro EGFR kinase activity system were employed to identify the potential inhibitory effects of Lycorine on EGFR. And the Biacore assay was used to confirm the direct binding status between Lycorine and the intracellular EGFR (696–1022) domain. In vitro assays were conducted to test the suppression of Lycorine on the biological behavior of GBM cells. By RNA interference, EGFR expression was reduced then cells underwent proliferation assay to investigate whether Lycorine’s inhibition on GBM cells was EGFR-dependent or not. RT-PCR and western blotting analysis were carried out to investigate the underlined molecular mechanism that Lycorine exerted on EGFR itself and EGFR signaling pathway. Three different xenograft models (an U251-luc intracranially orthotopic transplantation model, an EGFR stably knockdown U251 subcutaneous xenograft model and a patient-derived xenograft model) were performed to verify Lycorine’s therapeutic potential on GBM in vivo.

Results

We identified a novel small natural molecule Lycorine binding to the intracellular EGFR (696–1022) domain as an inhibitor of EGFR. Lycorine decreased GBM cell proliferation, migration and colony formation by inducing cell apoptosis in an EGFR-mediated manner. Furthermore, Lycorine inhibited the xenograft tumor growths in three animal models in vivo. Besides, Lycorine impaired the phosphorylation of EGFR, AKT, which were mechanistically associated with expression alteration of a series of cell survival and death regulators and metastasis-related MMP9 protein.

Conclusions

Our findings identify Lycorine directly interacts with EGFR and inhibits EGFR activation. The most significant result is that Lycorine displays satisfactory therapeutic effect in our patient-derived GBM tumor xenograft, thus supporting the conclusion that Lycorine may be considered as a promising candidate in clinical therapy for GBM.

Unstructured Formulation Data Analysis for the Optimization of Lipid Nanoparticle Drug Delivery Vehicles

Designing nanoparticle formulations with features tailored to their therapeutic targets in demanding timelines assumes increased importance. In this context, nanostructured lipid carriers (NLCs) offer an excellent example of a drug delivery nanosystem that has been broadly explored in the treatment of glioblastoma multiforme (GBM). Distinct fundamental NLC quality attributes can be harnessed to fit this purpose, namely particle size, size distribution, and zeta potential. These critical aspects intrinsically depend on the formulation components, influencing drug loading capacity, drug release, and stability of the NLCs. Wide variations in their composition, including the type of lipids and other surface modifier excipients, lead to differences on these parameters. NLC target product profile involves small mean particle sizes, narrow size distributions, and absolute values of zeta potential higher than 30 mV. In this work, a wealth of data previously obtained in experiments on NLC preparation, encompassing, e.g., results of preliminary studies and those of intermediate formulations, is analyzed in order to extract information useful in further optimization studies. Principal component analysis (PCA) and partial least squares (PLS) are performed to evaluate the influence of NLC composition on the respective characteristics. These methods provide a rapid and discriminatory analysis for establishing a preformulation framework, by selecting the most suitable types of lipids, surfactants, surface modifiers, and drugs, within the set of investigated variables. The results have direct implications in the optimization of formulation and processes.

CAT3, a prodrug of 13a(S)-3-hydroxyl-6,7-dimethoxyphenanthro[9,10-b]-indolizidine, circumvents temozolomide-resistant glioblastoma via the Hedgehog signaling pathway, independently of O6-methylguanine DNA methyltransferase expression

PURPOSE

Glioblastoma multiforme (GBM) is a malignant high-grade glioma with a poor clinical outcome. Temozolomide (TMZ) is the first-line GBM chemotherapy; however, patients commonly develop resistance to its effects.

MATERIALS AND METHODS

We investigated the antitumor activity of CAT3 in TMZ-resistant glioblastoma cell lines U251/TMZ and T98G. Orthotopic and subcutaneous mice tumor models were used to investigate the effects of various treatment regimes.

RESULTS

We found that PF403, the active metabolite of CAT3, inhibited proliferation of both cell lines. PF403 repressed the Hedgehog signaling pathway in the U251/TMZ cell line, reduced O6-methylguanine DNA methyltransferase (MGMT) expression, and abolished the effects of the Shh pathway. Moreover, PF403 blocked the Hedgehog signaling pathway in T98G MGMT-expressing cells and downregulated the expression of MGMT. CAT3 suppressed growth in the U251/TMZ orthotopic and T98G subcutaneous xenograft tumor models in vivo. We also demonstrated that inhibition of the Hedgehog pathway by PF403 counteracted TMZ resistance and enhanced the antitumor activity of TMZ in vitro and in vivo.

CONCLUSION

These results indicate that CAT3 is a potential therapeutic agent for TMZ-resistant GBM.

[The role of lipid metabolism disorders, atypical isoforms of protein kinase C, and mutational status of cytosolic and mitochondrial forms of isocitrate dehydrogenase in carcinogenesis of glial tumors]

The relationship between molecular genetic and metabolic disorders is one of the challenges of modern oncology. In this review, we consider lipid metabolism and its changes as one of the factors of oncogenesis of glial tumors. Also, we demonstrate that the genome and the metabolome are interconnected by a large number of links, and the metabolic pathways, during their reorganization, are able to drastically affect the genetic structure of the cell and, in particular, cause its tumor transformation. Our own observations and analysis of the literature data allow us to conclude that mass spectrometry is a highly accurate current method for assessing metabolic disorders at the cellular level. The use of mass spectrometry during surgery allows the neurosurgeon to obtain real-time data on the level of specific molecular markers in the resected tissue, thereby bringing intraoperative navigation techniques to the molecular level. The generation of molecular fingerprints for each tumor significantly complements the available neuroimaging, molecular genetic, and immunohistochemical data.

In vitro anti-cancer activity and pharmacokinetic evaluation of curcumin-loaded lipid nanocapsules

In the present work, lipid nanocapsules (LNC) for curcumin (CCM) encapsulation have been developed and optimized. The objective was to increase drug cytotoxicity on 9L glioma cells and drug bioavailability following intravenous administration (IV). Using the phase inversion technique, we obtained 50 nm LNC loaded with CCM (4 and 6 mg/mL) and, due to the hydrophobic nature of the drug, the encapsulation efficiency was very high, being around 90%. Following 48 h of incubation with 9L cells, CCM-loaded LNC were able to reduce the viability of glioma cells resulting in significant twofold lower IC50 in comparison with the free drug solution. Moreover, CCM-loaded LNC induced both the apoptosis of 9L cells and a strong release of ATP. This suggests a cellular uptake of the LNC and an enhanced anti-proliferative effect. In order to evaluate any alteration in the pharmacokinetic behavior of the encapsulated drug, CCM-loaded LNC were injected IV into healthy rats, at a dose of 10 mg/kg. CCM pharmacokinetic studies were carried out quantifying the CCM concentration from the blood of rats, receiving either CCM-loaded LNC or free CCM solution as a control. The results demonstrated that loaded LNC exhibited a significantly higher AUC, C_max and t_1/2 in comparison with the control, while the clearance was strongly reduced. Globally, these results encouraged the use of CCM-loaded LNC to enhance the in vivo therapeutic activity of the drug after systemic administration.

Chaperonology: The Third Eye on Brain Gliomas

The European Organization for Research and Treatment of Cancer/National Cancer Institute of Canada Phase III trial has validated as a current regimen for high-grade gliomas (HGG) a maximal safe surgical resection followed by radiotherapy with concurrent temozolamide. However, it is essential to balance maximal tumor resection with preservation of the patient’s neurological functions. Important developments in the fields of pre-operative and intra-operative neuro-imaging and neuro-monitoring have ameliorated the survival rate and the quality of life for patients affected by HGG. Moreover, even though the natural history remains extremely poor, advancement in the molecular and genetic fields have opened up new potential frontiers in the management of this devastating brain disease. In this review, we aim to present a comprehensive account of the main current pre-operative, intra-operative and molecular approaches to HGG with particular attention to specific chaperones, also called heat shock proteins (Hsps), which represent potential novel biomarkers to detect and follow up HGG, and could also be therapeutic agents.

Expression profile of circular RNAs in IDH-wild type glioblastoma tissues

OBJECTIVE

The aim of the present study is to investigate the expression profiles of circular RNAs (circRNAs) in IDH-wild type (IDH-wt) glioblastoma and explore the differences in circRNAs expression between IDH-wt glioblastoma and adjacent normal brain.

PATIENTS AND METHODS

circRNA expression profiles were detected by circRNA microarray in three matched pairs of IDH-wt glioblastoma and adjacent normal brain. qRT-PCR was used to verify the differential expression of circRNAs from microarray analysis. Bioinformatics analysis was used to analyze potential functions of the differentially expressed circRNAs in IDH-wt glioblastoma.

RESULTS

Compared with the adjacent normal brain tissues, 254 circRNAs were upregulated and 361 circRNAs were downregulated in IDH-wt glioblastoma with a ≥1.5-fold change. A total of 12 differentially expressed circRNAs were randomly selected and validated a good correlation of results from circRNA-seq with qRT-PCR. Gene Ontology (GO) analysis revealed the differentially expressed circRNAs possibly involved in cell division, DNA damage repair, cytoskeleton, and protein ubiquitination. 46 and 50 miRNAs were predicted to be adsorbed by the top 10 upregulated circRNAs and top 10 downregulated circRNAs, respectively.

CONCLUSION

Differential expression of circRNAs may be associated with IDH-wt glioblastoma development and progression, and these circRNAs can be identified as biomarkers for prognosis prediction and targets for treatment.

Towards tailored management of malignant brain tumors with nanotheranostics

Malignant brain tumors still represent an unmet medical need given their rapid progression and often fatal outcome within months of diagnosis. Given their extremely heterogeneous nature, the assumption that a single therapy could be beneficial for all patients is no longer plausible. Hence, early feedback on drug accumulation at the tumor site and on tumor response to treatment would help tailor therapies to each patient's individual needs for personalized medicine. In this context, at the intersection between imaging and therapy, theranostic nanomedicine is a promising new technique for individualized management of malignant brain tumors. Although brain nanotheranostics has yet to be translated into clinical practice, this field is now a research hotspot due to the growing demand for personalized therapies. In this review, the barriers to the clinical implementation of theranostic nanomedicine for tracking tumor responses to treatment and for guiding stimulus-activated therapies and surgical resection of malignant brain tumors are discussed. Likewise, the criteria that nanotheranostic systems need to fulfil to become clinically relevant formulations are analyzed in depth, focusing on theranostic agents already tested in vivo. Currently, magnetic nanoparticles exploiting brain targeting strategies represent the first generation of preclinical theranostic nanomedicines for the management of malignant brain tumors.

STATEMENT OF SIGNIFICANCE

The development of nanocarriers that can be used both in imaging studies and the treatment of brain tumors could help identify which patients are most and least likely to respond to a given treatment. This will enable clinicians to adapt the therapy to the needs of the patient and avoid overdosing non-responders. Given the many different approaches to non-invasive techniques for imaging and treating brain tumors, it is important to focus on the strategies most likely to be implemented and to design the most feasible theranostic biomaterials that will bring nanotheranostics one step closer to clinical practice.

Personalized regulation of glioblastoma cancer stem cells based on biomedical technologies: From theory to experiment (Review)

Glioblastoma multiforme (GBM) is one of the most aggressive brain tumors. GBM represents >50% of primary tumors of the nervous system and ~20% of intracranial neoplasms. Standard treatment involves surgery, radiation and chemotherapy. However, the prognosis of GBM is usually poor, with a median survival of 15 months. Resistance of GBM to treatment can be explained by the presence of cancer stem cells (CSCs) among the GBM cell population. At present, there are no effective therapeutic strategies for the elimination of CSCs. The present review examined the nature of human GBM therapeutic resistance and attempted to systematize and put forward novel approaches for a personalized therapy of GBM that not only destroys tumor tissue, but also regulates cellular signaling and the morphogenetic properties of CSCs. The CSCs are considered to be an informationally accessible living system, and the CSC proteome should be used as a target for therapy directed at suppressing clonal selection mechanisms and CSC generation, destroying CSC hierarchy, and disrupting the interaction of CSCs with their microenvironment and extracellular matrix. These objectives can be achieved through the use of biomedical cellular products.

Extracts of Artocarpus communis Induce Mitochondria-Associated Apoptosis via Pro-oxidative Activity in Human Glioblastoma Cells

Glioblastoma multiforme (GBM) is an extremely aggressive and devastating malignant tumor in the central nervous system. Its incidence is increasing and the prognosis is poor. Artocarpin is a natural prenylated flavonoid with various anti-inflammatory and anti-tumor properties. Studies have shown that artocarpin is associated with cell death of primary glioblastoma cells. However, the in vivo effects and the cellular and molecular mechanisms modulating the anticancer activities of artocarpin remain unknown. In this study, we demonstrated that treating the glioblastoma cell lines U87 and U118 cells with artocarpin induced apoptosis. Artocarpin-induced apoptosis is associated with caspase activation and poly (ADP-ribose) polymerase (PARP) cleavage and is mediated by the mitochondrial pathway. This is associated with mitochondrial depolarization, mitochondrial-derived reactive oxidative species (ROS) production, cytochrome c release, Bad and Bax upregulations, and Bcl-2 downregulation. Artocarpin induced NADPH oxidase/ROS generation plays an important role in the mitochondrial pathway activation. Furthermore, we found artocarpin-induced ROS production in mitochondria is associated with Akt- and ERK1/2 activation. After treatment with artocarpin, ROS causes PI3K/Akt/ERK1/2-induced cell death of these tumor cells. These observations were further verified by the results from the implantation of both U87 and U118 cells into in vivo mouse. In conclusion, our findings suggest that artocarpin induces mitochondria-associated apoptosis of glioma cells, suggesting that artocarpine can be a potential chemotherapeutic agent for future GBM treatment.

Glioma-Targeted Delivery of a Theranostic Liposome Integrated with Quantum Dots, Superparamagnetic Iron Oxide, and Cilengitide for Dual-Imaging Guiding Cancer Surgery

Herein, a theranostic liposome (QSC-Lip) integrated with superparamagnetic iron oxide nanoparticles (SPIONs) and quantum dots (QDs) and cilengitide (CGT) into one platform is constructed to target glioma under magnetic targeting (MT) for guiding surgical resection of glioma. Transmission electron microscopy and X-ray photoelectron spectroscopy confirm the complete coencapsulation of SPIONs and QDs in liposome. Besides, CGT is also effectively encapsulated into the liposome with an encapsulation efficiency of ∼88.9%. QSC-Lip exhibits a diameter of 100 ± 1.24 nm, zeta potential of -17.10 ± 0.11 mV, and good stability in several mediums. Moreover, each cargo shows a biphasic release pattern from QSC-Lip, a rapid initial release within initial 10 h followed by a sustained release. Cellular uptake of QSC-Lip is significantly enhanced by C₆ cells under MT. In vivo dual-imaging studies show that QSC-Lip not only produces an obvious negative-contrast enhancement effect on glioma by magnetic resonance imaging but also makes tumor emitting fluorescence under MT. The dual-imaging of QSC-Lip guides the accurate resection of glioma by surgery. Besides, CGT is also specifically distributed to glioma after administration of QSC-Lip under MT, resulting in an effective inhibition of tumors. The integrated liposome may be a potential carrier for theranostics of tumor.

Predicting epidermal growth factor receptor gene amplification status in glioblastoma multiforme by quantitative enhancement and necrosis features deriving from conventional magnetic resonance imaging

To study whether some of the quantitative enhancement and necrosis features in preoperative conventional MRI (cMRI) had a predictive value for epidermal growth factor receptor (EGFR) gene amplification status in glioblastoma multiforme (GBM).Fifty-five patients with pathologically determined GBMs who underwent cMRI were retrospectively reviewed. The following cMRI features were quantitatively measured and recorded: long and short diameters of the enhanced portion (LDE and SDE), maximum and minimum thickness of the enhanced portion (MaxTE and MinTE), and long and short diameters of the necrotic portion (LDN and SDN). Univariate analysis of each feature and a decision tree model fed with all the features were performed. Area under the receiver operating characteristic (ROC) curve (AUC) was used to assess the performance of features, and predictive accuracy was used to assess the performance of the model.For single feature, MinTE showed the best performance in differentiating EGFR gene amplification negative (wild-type) (nEGFR) GBM from EGFR gene amplification positive (pEGFR) GBM, and it got an AUC of 0.68 with a cut-off value of 2.6 mm. The decision tree model included 2 features MinTE and SDN, and got an accuracy of 0.83 in validation dataset.Our results suggest that quantitative measurement of the features MinTE and SDN in preoperative cMRI had a high accuracy for predicting EGFR gene amplification status in GBM.

Circular RNA hsa_circ_0008344 regulates glioblastoma cell proliferation, migration, invasion, and apoptosis

BACKGROUND

Recent studies have found circular RNAs (circRNAs) involved in the biological process of cancers. However, little is known about their functional roles in glioblastoma.

METHODS

Human circRNA microarray analysis was performed to screen the expression profile of circRNAs in IDH1 wild-type glioblastoma tissue. The expression of hsa_circ_0008344 in glioblastoma and normal brain samples was quantified by qRT-PCR. Functional experiments were performed to investigate the biological functions of hsa_circ_0008344, including MTT assay, colony formation assay, transwell assay, and cell apoptosis assay.

RESULTS

CircRNA microarray revealed a total of 417 abnormally expressed circRNAs (>1.5-fold, P < .05) in glioblastoma tissue compared with the adjacent normal brain. Hsa_circ_0008344, among the top differentially expressed circRNAs, was significantly upregulated in IDH1 wild-type glioblastoma. Further in vitro studies showed that knockdown of hsa_circ_0008344 suppressed glioblastoma cell proliferation, colony formation, migration, and invasion, but increased cell apoptotic rate.

CONCLUSIONS

Hsa_circ_0008344 is upregulated in glioblastoma and may contribute to the progression of this malignancy.

Efficient Gene Silencing in Brain Tumors with Hydrophobically Modified siRNAs

Glioblastoma (GBM) is the most common and lethal form of primary brain tumor with dismal median and 2-year survivals of 14.5 months and 18%, respectively. The paucity of new therapeutic agents stems from the complex biology of a highly adaptable tumor that uses multiple survival and proliferation mechanisms to circumvent current treatment approaches. Here, we investigated the potency of a new generation of siRNAs to silence gene expression in orthotopic brain tumors generated by transplantation of human glioma stem-like cells in athymic nude mice. We demonstrate that cholesterol-conjugated, nuclease-resistant siRNAs (Chol-hsiRNAs) decrease mRNA and silence luciferase expression by 90% in vitro in GBM neurospheres. Furthermore, Chol-hsiRNAs distribute broadly in brain tumors after a single intratumoral injection, achieving sustained and potent (>45% mRNA and >90% protein) tumor-specific gene silencing. This readily available platform is sequence-independent and can be adapted to target one or more candidate GBM driver genes, providing a straightforward means of modulating GBM biology in vivoMol Cancer Ther; 17(6); 1251-8. ©2018 AACR.

Glioblastoma-activated pericytes support tumor growth via immunosuppression

Glioblastoma multiforme is the most common and aggressive primary brain tumor, with an extremely poor prognosis. The lack of detailed knowledge about the cellular and molecular mechanisms involved in glioblastoma development restricts the design of efficient therapies. A recent study using state-of-art technologies explores the role of pericytes in the glioblastoma microenvironment. Glioblastoma-activated pericytes develop an immunosuppressive phenotype, reducing T-cell activation through the induction of an anti-inflammatory response. Strikingly, pericytes support glioblastoma growth in vitro and in vivo. Here, we describe succinctly the results and implications of the findings reported in pericytes' and glioblastomas' biology. The emerging knowledge from this study will be essential for the treatment of brain tumors.

Therapeutic Monoclonal Antibodies Delivery for the Glioblastoma Treatment

Glioblastoma multiforme (GBM) is the most common and challenging primary malignant brain tumor, being the median overall survival between 10 and 14 months due to its invasive characteristics. GBM treatment is mainly based on the maximal surgical resection and radiotherapy associated to chemotherapy. Monoclonal antibodies (mAbs) have been used in chemotherapy protocols for GBM treatment in order to improve immunotherapy and antiangiogenic processes. High specificity and affinity of mAbs for biological targets make them highly used for brain tumor therapy. Specifically, antiangiogenic mAbs have been wisely indicated in chemotherapy protocols because GBM is the most vascularized tumors in humans with high expression of cytokines. However, mAb-based therapy is not that effective due to the aggressive spread of the tumor associated to the difficulty in the access of mAb into the brain (due to the blood-brain barrier). For that reason, nanobiotechnology has played an important role in the treatment of several tumors, mainly in the tumors of difficult access, such as GBM. In this chapter will be discussed strategies related with nanobiotechnology applied to the mAb delivery and how these therapeutics can improve the GBM treatment and life quality of the patient.

IDH1 R132H mutation regulates glioma chemosensitivity through Nrf2 pathway

Purpose

Numerous studies have reported that glioma patients with isocitrate dehydrogenase 1(IDH1) R132H mutation are sensitive to temozolomide treatment. However, the mechanism of IDH1 mutations on the chemosensitivity of glioma remains unclear. In this study, we investigated the role and the potential mechanism of Nrf2 in IDH1 R132H-mediated drug resistance.

Methods

Wild type IDH1 (R132H-WT) and mutant IDH1 (R132H) plasmids were constructed. Stable U87 cells and U251 cells overexpressing IDH1 were generated. Phenotypic differences between IDH1-WT and IDH1 R132H overexpressing cells were evaluated using MTT, cell colony formation assay, scratch test assay and flow cytometry. Expression of IDH1 and its associated targets, nuclear factor-erythroid 2-related factor 2 (Nrf2), NAD(P)H quinine oxidoreductase 1 (NQO1), multidrug resistant protein 1 (MRP1) and p53 were analyzed.

Results

The IDH1 R132H overexpressing cells were more sensitive to temozolomide than WT and the control, and Nrf2 was significantly decreased in IDH1 R132H overexpressing cells. We found that knocking down Nrf2 could decrease resistance to temozolomide. The nuclear translocation of Nrf2 in IDH1 R132H overexpressing cells was lower than the WT and the control groups after temozolomide treatment. When compared with WT cells, NQO1 expression was reduced in IDH1 R132H cells, especially after temozolomide treatment. P53 was involved in the resistance mechanism of temozolomide mediated by Nrf2 and NQO1.

Conclusions

Nrf2 played an important role in IDH1 R132H-mediated drug resistance. The present study provides new insight for glioma chemotherapy with temozolomide.

Advances in Glioblastoma Multiforme Treatment: New Models for Nanoparticle Therapy

The most lethal form of brain cancer, glioblastoma multiforme, is characterized by rapid growth and invasion facilitated by cell migration and degradation of the extracellular matrix. Despite technological advances in surgery and radio-chemotherapy, glioblastoma remains largely resistant to treatment. New approaches to study glioblastoma and to design optimized therapies are greatly needed. One such approach harnesses computational modeling to support the design and delivery of glioblastoma treatment. In this paper, we critically summarize current glioblastoma therapy, with a focus on emerging nanomedicine and therapies that capitalize on cell-specific signaling in glioblastoma. We follow this summary by discussing computational modeling approaches focused on optimizing these emerging nanotherapeutics for brain cancer. We conclude by illustrating how mathematical analysis can be used to compare the delivery of a high potential anticancer molecule, delphinidin, in both free and nanoparticle loaded forms across the blood-brain barrier for glioblastoma.

Human cytomegalovirus immediate-early protein promotes survival of glioma cells through interacting and acetylating ATF5

Human cytomegalovirus (HCMV), a widespread beta-herpes virus, infects a high percentage of gliomas. HCMV is specifically detected in human gliomas at a low level of expression raises the possibility that it may regulate the malignant phenotype in a chronic manner. Although HCMV is not recognized as an oncogenic virus, it might dysregulate signaling pathways involved in initiation and promotion of malignancy.Here, our immunohistochemical staining reveals that nucleus staining of the HCMV 86-kDa immediate-early protein (IE86) is markedly increased in GBM (58.56%) compared with that in nontumorous samples (4.20%) and low-grade glioma(19.56%). IE86 staining positively correlates with the staining of activating transcription factor 5 (ATF5) which is essential for glioma cell viability and proliferation suggesting that HCMV IE86 could have important implications in glioma biology. Moreover, we find that the IE86 overexpression enhances glioma cell's growth in vitro and in vivo. We demonstrate that IE86 protein physically interacts with, and acetylates ATF5 thereby promoting glioma cell survival. Therefore, our findings illustrate the biological significance of HCMV infection in accelerating glioma progression, and provide novel evidence that HCMV infection may serve as a therapeutic target in human glioma.

Rottlerin inhibits cell growth and invasion via down-regulation of Cdc20 in glioma cells

Rottlerin, isolated from a medicinal plant Mallotus phillippinensis, has been demonstrated to inhibit cellular growth and induce cytoxicity in glioblastoma cell lines through inhibition of calmodulin-dependent protein kinase III. Emerging evidence suggests that rottlerin exerts its antitumor activity as a protein kinase C inhibitor. Although further studies revealed that rottlerin regulated multiple signaling pathways to suppress tumor cell growth, the exact molecular insight on rottlerin-mediated tumor inhibition is not fully elucidated. In the current study, we determine the function of rottlerin on glioma cell growth, apoptosis, cell cycle, migration and invasion. We found that rottlerin inhibited cell growth, migration, invasion, but induced apoptosis and cell cycle arrest. Mechanistically, the expression of Cdc20 oncoprotein was measured by the RT-PCR and Western blot analysis in glioma cells treated with rottlerin. We observed that rottlerin significantly inhibited the expression of Cdc20 in glioma cells, implying that Cdc20 could be a novel target of rottlerin. In line with this, over-expression of Cdc20 decreased rottlerin-induced cell growth inhibition and apoptosis, whereas down-regulation of Cdc20 by its shRNA promotes rottlerin-induced anti-tumor activity. Our findings indicted that rottlerin could exert its tumor suppressive function by inhibiting Cdc20 pathway which is constitutively active in glioma cells. Therefore, down-regulation of Cdc20 by rottlerin could be a promising therapeutic strategy for the treatment of glioma.

Metabolomic profiling identifies distinct phenotypes for ASS1 positive and negative GBM

Background

Tumour cells have a high demand for arginine. However, a subset of glioblastomas has a defect in the arginine biosynthetic pathway due to epigenetic silencing of the rate limiting enzyme argininosuccinate synthetase (ASS1). These tumours are auxotrophic for arginine and susceptible to the arginine degrading enzyme, pegylated arginine deiminase (ADI-PEG20). Moreover, ASS1 deficient GBM have a worse prognosis compared to ASS1 positive tumours. Since altered tumour metabolism is one of the hallmarks of cancer we were interested to determine if these two subtypes exhibited different metabolic profiles that could allow for their non-invasive detection as well as unveil additional novel therapeutic opportunities.

Methods

We looked for basal metabolic differences using one and two-dimensional gas chromatography-time-of-flight mass spectrometry (1D/2D GC-TOFMS) followed by targeted analysis of 29 amino acids using liquid chromatography-time-of-flight mass spectrometry (LC-TOFMS). We also looked for differences upon arginine deprivation in a single ASS1 negative and positive cell line (SNB19 and U87 respectively). The acquired data was evaluated by chemometric based bioinformatic methods.

Results

Orthogonal partial least squares-discriminant analysis (OPLS-DA) of both the 1D and 2D GC-TOFMS data revealed significant systematic difference in metabolites between the two subgroups with ASS1 positive cells generally exhibiting an overall elevation of identified metabolites, including those involved in the arginine biosynthetic pathway. Pathway and network analysis of the metabolite profile show that ASS1 negative cells have altered arginine and citrulline metabolism as well as altered amino acid metabolism. As expected, we observed significant metabolite perturbations in ASS negative cells in response to ADI-PEG20 treatment.

Conclusions

This study has highlighted significant differences in the metabolome of ASS1 negative and positive GBM which warrants further study to determine their diagnostic and therapeutic potential for the treatment of this devastating disease.

Therapeutic Potential of Thymoquinone in Glioblastoma Treatment: Targeting Major Gliomagenesis Signaling Pathways

Glioblastoma multiforme (GBM) is one of the most devastating brain tumors with median survival of one year and presents unique challenges to therapy because of its aggressive behavior. Current treatment strategy involves surgery, radiotherapy, immunotherapy, and adjuvant chemotherapy even though optimal management requires a multidisciplinary approach and knowledge of potential complications from both the disease and its treatment. Thymoquinone (TQ), the main bioactive component of Nigella sativa L., has exhibited anticancer effects in numerous preclinical studies. Due to its multitargeting nature, TQ interferes in a wide range of tumorigenic processes and counteract carcinogenesis, malignant growth, invasion, migration, and angiogenesis. TQ can specifically sensitize tumor cells towards conventional cancer treatments and minimize therapy-associated toxic effects in normal cells. Its potential to enter brain via nasal pathway due to volatile nature of TQ adds another advantage in overcoming blood-brain barrier. In this review, we summarized the potential role of TQ in different signaling pathways in GBM that have undergone treatment with standard therapeutic modalities or with TQ. Altogether, we suggest further comprehensive evaluation of TQ in preclinical and clinical level to delineate its implied utility as novel therapeutics to combat the challenges for the treatment of GBM.

Overcoming blood–brain barrier by HER2-targeted nanosystem to suppress glioblastoma cell migration, invasion and tumor growth

Herein we synthesize an HER2 antibody-conjugated selenium nanoparticle platform can efficiently deliver both therapeutic agents and diagnostic agents (superparamagnetic iron oxide nanoparticles) across the BBB into the tumor tissues and enhances their effects on brain tumor treatment and MR imaging.

Targeting glioma stem cells enhances anti-tumor effect of boron neutron capture therapy

The uptake of (10)boron by tumor cells plays an important role for cell damage in boron neutron capture therapy (BNCT). CD133 is frequently expressed in the membrane of glioma stem cells (GSCs), resistant to radiotherapy and chemotherapy, and represents a potential therapeutic target. To increase (10)boron uptake in GSCs, we created a polyamido amine dendrimer, conjugated CD133 monoclonal antibodies, encapsulating mercaptoundecahydrododecaborate (BSH) in void spaces, and monitored the uptake of the bioconjugate nanoparticles by GSCs in vitro and in vivo. Fluorescence microscopy showed the specific uptake of the bioconjugate nanoparticles by CD133-positive GSCs. Treatment with the biconjugate nanoparticles resulted in a significant lethal effect after neutron radiation due to efficient and CD133-independent cellular targeting and uptake in CD133-expressing GSCs. A significantly longer survival occurred in combination with the biconjugate nanoparticles and BSH compared with BSH alone in human intracranial GBM models employing CD133-positive GSCs xenografts. Our data demonstrated that this bioconjugate nanoparticle targets human CD133-positive GSCs and is a potential boron agent in BNCT.

Computational modeling in glioblastoma: from the prediction of blood-brain barrier permeability to the simulation of tumor behavior

The integrated in silico-in vitro-in vivo approaches have fostered the development of new treatment strategies for glioblastoma patients and improved diagnosis, establishing the bridge between biochemical research and clinical practice. These approaches have provided new insights on the identification of bioactive compounds and on the complex mechanisms underlying the interactions among glioblastoma cells, and the tumor microenvironment. This review focuses on the key advances pertaining to computational modeling in glioblastoma, including predictive data on drug permeability across the blood-brain barrier, tumor growth and treatment responses. Structure- and ligand-based methods have been widely adopted, enabling the study of dynamic and evolutionary aspects of glioblastoma. Their potential applications as predictive tools and the advantages over other well-known methodologies are outlined. Challenges regarding in silico approaches for predicting tumor properties are also discussed.

Lesion magnetic susceptibility response to hyperoxic challenge: A biomarker for malignant brain tumor microenvironment?

BACKGROUND AND PURPOSE

Quantitative susceptibility mapping has been previously used to differentiate lesions in patients with brain tumors. The aim of this work was to characterize the response of magnetic susceptibility differences in malignant brain tumors and surrounding edema to hyperoxic and hypercapnic respiratory challenges.

METHODS

Images of malignant brain tumor patients (2 glioblastoma multiforme, 2 anaplastic astrocytoma, 1 brain metastasis) with clinical MRI exams (contrast-enhanced T1w) were acquired at 3T. 3D multi-gradient-echo data sets were acquired while the patients inhaled medical-air (21% O2), oxygen (100% O2), and carbogen (95% O2, 5% CO2). Susceptibility maps were generated from real and imaginary data. Regions of interest were analyzed with respect to respiration-gas-induced susceptibility changes.

RESULTS

Contrast-enhancing tumor regions with high baseline magnetic susceptibility exhibited a marked susceptibility reduction under hyperoxic challenges, with a stronger effect (-0.040 to -0.100ppm) under hypercapnia compared to hyperoxia (-0.010 to -0.067ppm). In contrast, regions attributed to necrotic tissue and to edema showed smaller changes of opposite sign, i.e. paramagnetic shift. There was a correlation between malignant tumor tissue magnetic susceptibility at baseline under normoxia and the corresponding susceptibility reduction under hypercapnia and - to a lesser degree - under hyperoxia.

CONCLUSION

In this small cohort of analysis, quantification of susceptibility changes in response to respiratory challenges allowed a complementary, functional differentiation of tumorous sub-regions. Those changes, together with the correlations observed between baseline susceptibility under normoxia and susceptibility reduction with challenges, could prove helpful for a non-invasive characterization of local tumor microenvironment.

Stanniocalcin-1 augments stem-like traits of glioblastoma cells through binding and activating NOTCH1

Glioblastoma (GBM) is a fatal tumor and comprises heterogeneous cells in which a subpopulation with stem cell-like properties is included. Cancer cells with stem cell-like properties account for tumor initiation, drug resistance and recurrence. To identify and characterize specific factors in regulating stem-like traits is critical for GBM therapeutic. Here, we showed that Stanniocalcin-1 (STC1), a secretory glycoprotein, functions as a novel stimulator for stem-like traits of GBM cells. We found STC1 was prominently expressed in glioma spheres which are mainly comprised of glioma stem-like cells. The stem-like traits of GBM cells, as determined by the expression of stem cell markers, tumor-sphere formation efficiency and colony-forming ability, were enhanced by STC1 overexpression and inhibited by STC1 knockdown. Furthermore, introduction of STC1 enhanced tumorigenesis in vivo while knockdown of STC1 showed reverse effect. Finally, we demonstrated that STC1 interacted with the extracellular domain of NOTCH1 to activate NOTCH1-SOX2 signaling pathway, by which STC1 augmented the stem-like traits of GBM cells. Taken together, our data herein indicate that STC1 is a novel non-canonical NOTCH ligand and acts as a crucial regulator of stemness in GBM.

Identification of Driver Genes and Key Pathways of Glioblastoma Shows JNJ-7706621 as a Novel Antiglioblastoma Drug

OBJECTIVE

The aim of this study is to identify novel targets of diagnosis, therapy, and prognosis for glioblastoma, as well as to verify the therapeutic effect of JNJ-7706621 regarding glioblastoma.

METHODS

The gene expression profiles of GSE42656, GSE50161, and GSE86574 were obtained respectively from the Gene Expression Omnibus database. The differentially expressed genes (DEGs) were identified with comparison between gene expression profiles of the glioblastoma tissues and normal tissues. Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis and protein-protein interaction (PPI) network analyses were performed. Quantitative reverse transcription polymerase chain reaction and survival curve analysis were also conducted to verify the correlation between expression of hub genes and prognosis. Moreover, in vitro, MTT assay, colony-forming assay, the scratch assay, and flow cytometry were performed to verify the therapeutic effect of JNJ-7706621.

RESULTS

AURKA, NDC80, KIF4A, and NUSAP1 were identified as hub genes after PPI network analysis. Differential expression of those genes was detected between human normal glial cells and glioblastoma cells by quantitative reverse transcription polymerase chain reaction (P < 0.05), and the survival curve analysis showed that the patients with low expression of gene AURKA, NDC80, KIF4A, and NUSAP1 had a significant favorable prognosis (P < 0.05). In vitro assays showed that JNJ-7706621 inhibited glioblastoma cellular viability, proliferation, and migration via inducing glioblastoma cells apoptosis.

CONCLUSIONS

AURKA, NDC80, KIF4A, and NUSAP1 were significantly more highly expressed in glioblastoma cells than in human normal glial cell. Patients with low expression of those 4 genes had a favorable prognosis. JNJ-7706621 was a potential drug in treatment of patients with glioblastoma.

Insertion of the Type-I IFN Decoy Receptor B18R in a miRNA-Tagged Semliki Forest Virus Improves Oncolytic Capacity but Results in Neurotoxicity

Oncolytic Semliki Forest virus (SFV) has been suggested as a potential candidate for the treatment of glioblastoma and neuroblastoma. However, the oncolytic capacity of SFV is restricted by the anti-viral type-I interferon (IFN) response. The aim of this study was to increase the oncolytic capacity of a microRNA target tagged SFV against glioblastoma by arming it with the Vaccinia-virus-encoded type-I IFN decoy receptor B18R (SFV4B18RmiRT) to neutralize type-I IFN response. Expression of B18R by SFV4B18RmiRT aided neutralization of IFN-β, which was shown by reduced STAT-1 phosphorylation and improved virus spread in plaque assays. B18R expression by SFV4 increased its oncolytic capacity in vitro against murine glioblastoma (CT-2A), regardless of the presence of exogenous IFN-β. Both SFV4B18RmiRT and SFV4miRT treatments controlled tumor growth in mice with syngeneic orthotopic gliomablastoma (CT-2A). However, treatment with SFV4B18RmiRT induced severe neurological symptoms in some mice because of virus replication in the healthy brain. Neither neurotoxicity nor virus replication in the brain was observed when SFV4miRT was administered. In summary, our results indicate that the oncolytic capacity of SFV4 was improved in vitro and in vivo by incorporation of B18R, but neurotoxicity of the virus was increased, possibly due to loss of microRNA targets.

Use of nanoparticles for glioblastoma treatment: a new approach

Glioblastoma (GBM) is a very aggressive CNS tumor with poor prognosis. Current treatment lacks efficacy indicating that new therapeutic approaches are needed. One of these new approaches is based on the use of nanoparticles (NPs) to deliver different cargos (antitumoral drugs or genetic materials) to tumoral cells. This review covers the signaling pathways altered in GBM cells to understand the rationale behind choosing new therapeutic targets and recent advances in the use of different NPs to deliver to GBM cells, both in vitro and in vivo, different therapeutic molecules. A special focus is placed on the effect of NPs on orthotopic brain tumors since this animal model represents the optimal model for translational purposes.

MicroRNA-675 promotes glioma cell proliferation and motility by negatively regulating retinoblastoma 1

Previous studies indicated that microRNA (miR)-675 and its precursor lncRNA H19 were both overexpressed in glioma tissues, and H19 might play an oncogenic role. To investigate the involvement of miR-675 in gliomas and its underlying mechanisms, we here collected candidate target genes of miR-675-5p from miRTarBase (http://mirtarbase.mbc.nctu.edu.tw/, Release 6.0), which contains the experimentally validated microRNA-target interactions. Then, regulatory effects of miR-675 on its target genes were validated using clinical samples and glioma cell lines. Involvement of the miR-675-target axis deregulation in cell proliferation, migration and invasion of glioma was demonstrated by both gain- and loss-of-function experiments. As a result, retinoblastoma 1 (RB1) was identified as a candidate target gene of miR-675-5p. Expression levels of miR-675-5p in glioma tissues and cells were negatively correlated with RB1 expression at both mRNA and protein levels. Importantly, deregulation of the miR-675-5p-RB1 axis was significantly associated with advanced World Health Organization (WHO) grade and low Karnofsky performance score (KPS) score of glioma patients. Luciferase reporter assay verified that RB1 was a direct target gene of miR-675 in glioma cells. Functionally, miR-675 promoted glioma cell proliferation, migration and invasion. Notably, simulation of RB1 antagonized the effects induced by miR-675 up-regulation in glioma cells. In conclusion, our data suggest that miR-675 may be a key negative regulator of RB1 and the imbalance of the miR-675-RB1 axis may be clinically associated with aggressive progression of glioma patients. In addition, miR-675 may act as an oncogenic miRNA in glioma cells via regulating its target gene RB1.

Subtotal Resection of a Thalamic Glioblastoma Multiforme through Transsylvian Approach

Glioblastoma multiforme (GBM) is a malignant brain tumor with an ominous prognosis. The standard treatment includes maximal safe resection plus adjuvant therapy. Thalamic GBMs, however, are unfavorable for microsurgical removal because of deep location and proximity to critical structures. We present a patient presenting with progressive hemiparesis and decreased consciousness with a large thalamic GBM who underwent subtotal resection through a transsylvian approach. His clinical and neurologic condition improved after surgery and he survived nine months after surgery. This may propose that in selected cases, more aggressive microsurgery for debulking of tumors might have some impact in the final outcome.​​​

MicroRNA-141 is a tumor regulator and prognostic biomarker in human glioblastoma

Human glioblastoma is one of the most malignant types of brain tumor in the world. In the present study, the functional mechanisms of microRNA-141 (miR-141) were assessed, and the potential role of miR-141 as a prognostic biomarker in glioblastoma was examined. The gene expression of miR-141 in glioblastoma cell lines and glioblastoma tumors was assessed by reverse transcription-quantitative polymerase chain reaction. Glioblastoma LN229 and U89 cell lines were transfected with synthetic miR-141 mimics to upregulate endogenous miR-141. The subsequent effect on glioblastoma proliferation was assessed by MTT assay. In human glioblastoma, miR-141 expression was compared between patients with tumors of different pathological grades. Statistical analyses were performed to assess the correlation between miR-141 and the clinicopathological properties and overall survival rates (OS) of the patients. In addition, a Cox regression model was used to examine whether miR-141 was a potential biomarker of glioblastoma. miR-141 was aberrantly downregulated in glioblastoma cell lines and human glioblastoma tumors. Forced miR-141 upregulation in glioblastoma LN229 and U89 cell lines suppressed cancer proliferation. In patients with glioblastoma, miR-141 downregulation was closely associated with an advanced disease stage, poor clinicopathological properties and a shorter OS time. The multivariate Cox regression model demonstrated that low miR-141 expression was an effective prognostic biomarker for patients with glioblastoma. Overall, the present study showed that miR-141 may be a functional cancer regulator and a prognostic biomarker for glioblastoma.

Breaching barriers in glioblastoma. Part I: Molecular pathways and novel treatment approaches

Glioblastoma multiforme (GBM) is the most common primary brain tumour, and the most aggressive in nature. The prognosis for patients with GBM remains poor, with a median survival time of only 1-2 years. The treatment failure relies on the development of resistance by tumour cells and the difficulty of ensuring that drugs effectively cross the dual blood brain barrier/blood brain tumour barrier. The advanced molecular and genetic knowledge has allowed to identify the mechanisms responsible for temozolomide resistance, which represents the standard of care in GBM, along with surgical resection and radiotherapy. Such resistance has motivated the researchers to investigate new avenues for GBM treatment intended to improve patient survival. In this review, we provide an overview of major obstacles to effective treatment of GBM, encompassing biological barriers, cancer stem cells, DNA repair mechanisms, deregulated signalling pathways and autophagy. New insights and potential therapy approaches for GBM are also discussed, emphasizing localized chemotherapy delivered directly to the brain, immunotherapy, gene therapy and nanoparticle-mediated brain drug delivery.

Current status and future perspectives of sonodynamic therapy in glioma treatment

Malignant glioma is one of the most challenging central nervous system diseases to treat, and has high rates of recurrence and mortality. The current therapies include surgery, radiation therapy, and chemotherapy, although these approaches often failed to control tumor progression or improve patient survival. Sonodynamic therapy is a developing cancer treatment that uses ultrasound combined with a sonosensitizer to synergistically kill tumor cells, and has provided impressive results in both in vitro and in vivo studies. The ultrasound waves can penetrate deep tissues and reversibly open the blood-brain barrier to enhance drug delivery to the brain. Thus, sonodynamic therapy has a promising potential in glioma treatment. In this review, we summarize the studies that have confirmed the pre-clinical efficacy of sonodynamic therapy for glioma treatment, and discuss the future directions for this emerging treatment.

Curcumin exerts its tumor suppressive function via inhibition of NEDD4 oncoprotein in glioma cancer cells

Glioblastoma is the most common brain cancer in adults. It represents one of the top ten malignant tumors with an average survival time of nine months despite treatments with surgery, radiotherapy and chemotherapy. Curcumin is a phytochemical turmeric isolated from root of the Curcuma longa plant. Accumulating evidence have proved that curcumin targets numerous cancer signaling pathways. The E3 ubiquitin ligase NEDD4, neural precursor cell expressed developmentally downregulated protein 4, is frequently overexpressed in various cancers. However, whether curcumin regulates NEDD4 expression has not been described in human cancers. Therefore, in this study, we explored the roles of NEDD4 in glioma cell proliferation, apoptosis and mobility. We further investigated whether curcumin exerts its antitumor activities via suppressing NEDD4 expression. We found that curcumin reduced the expression of NEDD4 and Notch1 and pAKT, leading to glioma cell growth inhibition, apoptosis, and suppression of migration and invasion. Moreover, deletion of NEDD4 expression enhanced the sensitivity of glioma cells to curcumin treatment. Thus, inactivation of NEDD4 by curcumin could be a promising approach for therapeutic intervention.

Epithelial growth factor receptor expression influences 5-ALA induced glioblastoma fluorescence

The extent of 5-aminolevulinic acid (5-ALA) guided tumor resection has a determining impact in high-grade glioma and glioblastoma surgery. Yet the intensity of the 5-ALA induced fluorescence may vary within the tumor. We aimed to correlate 5-ALA induced fluorescence with the expression of epithelial growth factor receptor (EGFR) and its constitutively active version EGFRvIII in different glioblastoma (GBM) cell lines. To elucidate the role of EGFR in the metabolism of 5-ALA in GBM cell lines with variable EGFR expression status, we analyzed the activation of EGFR by its primary ligand EGF, and its downstream effect on Heme oxygenase-1 (HO-1), a key enzyme regulating the metabolism of Protoporphyrin IX (PpIX), the fluorescent metabolite of 5-ALA. Effects of direct pharmacological inhibition by Tin(IV)-Protoporphyrin (SnPP) or gene knockdown by small interfering RNA (siRNA) on HO-1 enzyme were analyzed in respect to 5-ALA induced fluorescence. Furthermore, inhibition of EGFR by Gefitinib was tested. A significant difference in 5-ALA induced fluorescence was obtained in U87MG (low EGFR expression) and LN229EGFR cells (EGFR overexpression) compared to BS153 (EGFR overexpression/EGFRvIII+). Treatment of U87MG and LN229EGFR cells with EGF significantly reduced cellular fluorescence, by promoting HO-1 transcription and expression in a concentration-dependent manner. This effect could be reversed by EGFR-specific siRNA treatment, which reduced protein expression of about 80% in U87MG. Remarkably, inhibition of HO-1 activity by SnPP or reduction of HO-1 protein levels by siHO-1 treatment restored fluorescence in all cell lines, independently of EGFR quantitative and qualitative expression. Gefitinib treatment was able to restore fluorescence after EGF stimulation in U87MG cells but not in BS153 cells, overexpressing EGFR/EGFRvIII. In GBM cell lines, 5-ALA induced fluorescence is variable and influenced by EGF-induced downstream activation of HO-1. HO-1 protein expression was identified as a negative regulator of 5-ALA induced fluorescence in GBM cells. We further propose that co-expression of EGFRvIII but not quantitative EGFR expression influence HO-1 activity and therefore cellular fluorescence.

Erythropoietin Promotes Glioblastoma via miR-451 Suppression

Erythropoietin (EPO) is an erythropoiesis stimulating growth factor and hormone. EPO has been widely used in the treatment of chronic renal failure, cancer, and chemotherapy-related anemia for three decades. However, many clinical trials showed that EPO treatment may be associated with tumorigenesis and cancer progression. EPO is able to cross blood-brain barriers, and this may lead to an increased possibility of central nervous system tumors such as glioblastoma. Indeed, EPO promotes glioblastoma growth and invasion in animal studies. Additionally, EPO increases glioblastoma cell survival, proliferation, migration, invasion, and chemoresistancy in vitro. However, the exact mechanisms of cancer progression induced by EPO treatment are not fully understood. Posttranscriptional gene regulation through microRNAs may contribute to EPO's cellular and biological effects in tumor progression. Here, we aimed to study whether tumor suppressive microRNA, miR-451, counteracts the positive effects of EPO on U87 human glioblastoma cell line. Migration and invasion were evaluated by scratch assay and transwell invasion assay, respectively. We found that EPO decreased basal miR-451 expression and increased cell proliferation, migration, invasion, and cisplatin chemoresistancy in vitro. miR-451 overexpression by transfection of its mimic significantly reversed these effects. Furthermore, ectopic expression of miR-451 inhibited expression of its own target genes, such as metalloproteinases-2 and -9, which are stimulated by EPO treatment and involved in carcinogenesis processes, especially invasion. These findings suggest that miR-451 mimic delivery may be useful as adjuvant therapy in addition to chemotherapy and anemia treatment by EPO and should be tested in experimental glioblastoma models.

Sulforaphane-cysteine induces apoptosis by sustained activation of ERK1/2 and caspase 3 in human glioblastoma U373MG and U87MG cells

We previously demonstrated that sulforaphane (SFN) inhibited invasion via sustained activation of ERK1/2 in human glioblastoma cells. However, sulforaphane-cysteine (SFN-Cys), an analog of SFN, enriched in plasma with longer half-life, had more potentiality to induce apoptosis. Here we investigated the molecular mechanisms of SFN-Cys-induced apoptosis in human glioblastoma U373MG and U87MG cells. Cell viability assay showed that SFN-Cys inhibited cell viability in a dose-dependent manner. Cell morphology observation also showed SFN-Cys increased the phenotype of cell death in a dose-dependent manner. Furthermore, flow cytometry assay showed that SFN-Cys induced apoptosis significantly in a dose-dependent manner in both cell lines. Furthermore, western blot analysis demonstrated that SFN-Cys induced activation of ERK1/2 in a sustained manner and the activation contributed to upregulation of Bax/Bcl-2 ratio and cleaved caspase 3, and these results can be reversed by the ERK1/2 blocker PD98059. Our results showed that SFN-Cys induced cell apoptosis via sustained activation of ERK1/2 and the ERK1/2 mediated signaling pathways such as activation of caspase 3 and apoptosis-related proteins, thus indicating that SFN-Cys might be a more promising therapeutic agent versus SFN to resist glioblastoma cells, especially in Taxol-resistant cancer cells.