Targeting malignant glioma survival signalling to improve clinical outcomes

Membrane-Decorated Exosomes for Combination Drug Delivery and Improved Glioma Therapy

Glioblastoma multiforme (GBM) is the most aggressive tumor of the central nervous system in adults. The standard therapy of GBM fails to eradicate it due to the drug resistance of glioblastoma stem cells (GSCs) and the presence of the blood-brain-barrier (BBB). Temozolomide (TMZ) is the first-line anti-GBM drug after surgery. However, the high activity of O⁶-alkylguanine-DNA alkyltransferase (AGT) limits the therapeutic effect of TMZ. Herein, we reported dual-receptor-specific exosomes as vehicles loaded with TMZ and O⁶-benzylguanine (BG) for eradicating TMZ-resistant GBM. Exosomes pose great promise as nanocarriers due to their intrinsic low immunogenicity, strong cargo-protective capacity, ideal size range, and natural penetration ability of the blood-brain-barrier (BBB). The target ligands angiopep-2 and CD133 RNA aptamers were conjugated on exosomes via an amphiphilic molecule bridge, which was induced to express on donor cells. The resulting nanocarriers exhibited efficient uptake by U87MG and GSCs, excellent BBB penetration ability, and perfect GBM accumulation due to An2 and CD133 aptamer functionalization. Such superior properties of the two dual-receptor-specific exosomes resulted in excellent in vitro proliferation inhibition of U87MG and GSCs and extension of the median survival time of U87MG-bearing mice, without causing adverse effects. The formed exosome nanocomposites can serve as powerful nanomedicine for GBM therapy and provide a promising avenue for targeted therapy against other diseases of the central nervous system.

IDP-410: a Novel Therapeutic Peptide that Alters N-MYC Stability and Reduces Angiogenesis and Tumor Progression in Glioblastomas

Glioblastomas (GBMs) are the most frequent and highly aggressive brain tumors, being resistant to all cytotoxic and molecularly targeted agents tested so far. There is, therefore, an urgent need to find novel therapeutic approaches and/or alternative targets to bring treatment options to patients. Here, we first show that GBMs express high levels of N-MYC protein, a transcription factor involved in normal brain development. A novel stapled peptide designed to specifically target N-MYC protein monomer, IDP-410, is able to impair the formation of N-MYC/MAX complex and reduce the stability of N-MYC itself. As a result, the viability of GBM cells is compromised. Moreover, the efficacy is found dependent on the levels of expression of N-MYC. Finally, we demonstrate that IDP-410 reduces GBM growth in vivo when administered systemically, both in subcutaneous and intracranial xenografts, reducing the vascularization of the tumors, highlighting a potential relationship between the function of N-MYC and the expression of mesenchymal/angiogenic genes. Overall, our results strengthen the view of N-MYC as a therapeutic target in GBM and strongly suggest that IDP-410 could be further developed to become a first-in-class inhibitor of N-MYC protein, affecting not only tumor cell proliferation and survival, but also the interplay between GBM cells and their microenvironment.

IL-24 inhibits the malignancy of human glioblastoma cells via destabilization of Zeb1

Glioblastoma (GBM) is the most common and fatal type of primary malignant tumours in the central nervous system. Cytokines such as interleukins (ILs) play an important role in GBM progression. Our present study found that IL-24 is down-regulated in GBM cells. Recombinant IL-24 (rIL-24) can suppress the in vitro migration and invasion of GBM cells while increase its chemo-sensitivity to temozolomide (TMZ) treatment. rIL-24 negatively regulates the expression of Zeb1, one well known transcription factors of epithelial to mesenchymal transition (EMT) of cancer cells. Over expression of Zeb1 can attenuate IL-24-suppressed malignancy of GBM cells. Mechanistically, IL-24 decreases the protein stability of Zeb1 while has no effect on its mRNA stability. It is due to that IL-24 can increase the expression of FBXO45, which can destabilize Zeb1 in cancer cells. Collectively, we reveal that IL-24 can suppress the malignancy of GBM cells via decreasing the expression of Zeb1. It suggests that targeted activation of IL-24 signals might be a potential therapy approach for GBM treatment.

Cedrol, a Sesquiterpene Alcohol, Enhances the Anticancer Efficacy of Temozolomide in Attenuating Drug Resistance via Regulation of the DNA Damage Response and MGMT Expression

Glioblastoma (GBM) is a common and aggressive brain tumor with a median survival of 12-15 months. Temozolomide (TMZ) is a first-line chemotherapeutic agent used in GBM therapy, but the occurrence of drug resistance limits its antitumor activity. The natural compound cedrol has remarkable antitumor activity and is derived from Cedrus atlantica. In this study, we investigated the combined effect of TMZ and cedrol in GBM cells in vitro and in vivo. The TMZ and cedrol combination treatment resulted in consistently higher suppression of cell proliferation via regulation of the AKT and MAPK signaling pathways in GBM cells. The combination treatment induced cell cycle arrest, cell apoptosis, and DNA damage better than either drug alone. Furthermore, cedrol reduced the expression of proteins associated with drug resistance, including O⁶-methlyguanine-DNA-methyltransferase (MGMT), multidrug resistance protein 1 (MDR1), and CD133 in TMZ-treated GBM cells. In the animal study, the combination treatment significantly suppressed tumor growth through the induction of cell apoptosis and decreased TMZ drug resistance. Moreover, cedrol-treated mice exhibited no significant differences in body weight and improved TMZ-induced liver damage. These results imply that cedrol may be a potential novel agent for combination treatment with TMZ for GBM therapy that deserves further investigation.

Src Inhibitors Pyrazolo[3,4-d]pyrimidines, Si306 and Pro-Si306, Inhibit Focal Adhesion Kinase and Suppress Human Glioblastoma Invasion In Vitro and In Vivo

Glioblastoma (GBM), as the most aggressive brain tumor, displays a high expression of Src tyrosine kinase, which is involved in the survival, migration, and invasiveness of tumor cells. Thus, Src emerged as a potential target for GBM therapy. The effects of Src inhibitors pyrazolo[3,4-d]pyrimidines, Si306 and its prodrug pro-Si306 were investigated in human GBM cell lines (U87 and U87-TxR) and three primary GBM cell cultures. Primary GBM cells were more resistant to Si306 and pro-Si306 according to the 3-(4,5-Dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay. However, the ability of all GBM cells to degrade the extracellular matrix was considerably compromised after Si306 and pro-Si306 applications. Besides reducing the phosphorylation of Src and its downstream signaling pathway components, both compounds decreased the phosphorylated form of focal adhesion kinase (FAK) and epidermal growth factor receptor (EGFR) expression, showing the potential to suppress the aggressiveness of GBM. In vivo, Si306 and pro-Si306 displayed an anti-invasive effect against U87 xenografts in the zebrafish embryo model. Considering that Si306 and pro-Si306 are able to cross the blood–brain barrier and suppress the spread of GBM cells, we anticipate their clinical testing in the near future. Moreover, the prodrug showed similar efficacy to the drug, implying the rationality of its use in clinical settings.

Optical properties of brain tissues at the different stages of glioma development in rats: pilot study

In this paper, measurements of the optical properties (diffuse reflectance, total and collimated transmittance) of brain tissues in healthy rats and rats with C6-glioma were performed in the spectral range from 350 to 1800 nm. Using these measurements, characteristic tissue optical parameters, such as absorption coefficient, scattering coefficient, reduced scattering coefficient, and scattering anisotropy factor were reconstructed. It was obtained that the 10-day development of glioma led to increase of absorption coefficient, which was associated with the water content elevation in the tumor. However, further development of the tumor (formation of the necrotic core) led to decrease in the water content. The dependence of the scattering properties on the different stages of model glioma development was more complex. Light penetration depth into the healthy and tumor brain was evaluated.

Targeting Glioma Initiating Cells with A combined therapy of cannabinoids and temozolomide

Glioblastoma multiforme (GBM) is the most frequent and aggressive type of brain tumor due, at least in part, to its poor response to current anticancer treatments. These features could be explained, at least partially, by the presence within the tumor mass of a small population of cells termed Glioma Initiating Cells (GICs) that has been proposed to be responsible for the relapses occurring in this disease. Thus, the development of novel therapeutic approaches (and specifically those targeting the population of GICs) is urgently needed to improve the survival of the patients suffering this devastating disease. Previous observations by our group and others have shown that Δ⁹-Tetrahydrocannabinol (THC, the main active ingredient of marijuana) and other cannabinoids including cannabidiol (CBD) exert antitumoral actions in several animal models of cancer, including gliomas. We also found that the administration of THC (or of THC + CBD at a 1:1 ratio) in combination with temozolomide (TMZ), the benchmark agent for the treatment of GBM, synergistically reduces the growth of glioma xenografts. In this work we investigated the effect of the combination of TMZ and THC:CBD mixtures containing different ratios of the two cannabinoids in preclinical glioma models, including those derived from GICs. Our findings show that TMZ + THC:CBD combinations containing a higher proportion of CDB (but not TMZ + CBD alone) produce a similar antitumoral effect as the administration of TMZ together with THC and CBD at a 1:1 ratio in xenografts generated with glioma cell lines. In addition, we also found that the administration of TMZ + THC:CBD at a 1:1 ratio reduced the growth of orthotopic xenografts generated with GICs derived from GBM patients and enhanced the survival of the animals bearing these intracranial xenografts. Remarkably, the antitumoral effect observed in GICs-derived xenografts was stronger when TMZ was administered together with cannabinoid combinations containing a higher proportion of CBD. These findings support the notion that the administration of TMZ together with THC:CBD combinations - and specifically those containing a higher proportion of CBD - may be therapeutically explored to target the population of GICs in GBM.

Optimization of a preclinical therapy of cannabinoids in combination with temozolomide against glioma

Glioblastoma multiforme (GBM) is the most frequent and aggressive form of brain cancer. These features are explained at least in part by the high resistance exhibited by these tumors to current anticancer therapies. Thus, the development of novel therapeutic approaches is urgently needed to improve the survival of the patients suffering this devastating disease. Δ⁹-Tetrahydrocannabinol (THC, the major active ingredient of marijuana), and other cannabinoids have been shown to exert antitumoral actions in animal models of cancer, including glioma. The mechanism of these anticancer actions relies, at least in part, on the ability of these compounds to stimulate autophagy-mediated apoptosis in tumor cells. Previous observations from our group demonstrated that local administration of THC (or of THC + CBD at a 1:1 ratio, a mixture that resembles the composition of the cannabinoid-based medicine Sativex®) in combination with Temozolomide, the benchmark agent for the treatment of GBM, synergistically reduces the growth of glioma xenografts. With the aim of optimizing the possible clinical utilization of cannabinoids in anti-GBM therapies, in this work we explored the anticancer efficacy of the systemic administration of cannabinoids in combination with TMZ in preclinical models of glioma. Our results show that oral administration of Sativex-like extracts (containing THC and CBD at a 1:1 ratio) in combination with TMZ produces a strong antitumoral effect in both subcutaneous and intracranial glioma cell-derived tumor xenografts. In contrast, combined administration of Sativex-like and BCNU (another alkylating agent used for the treatment of GBM which share structural similarities with the TMZ) did not show a stronger effect than individual treatments. Altogether, our findings support the notion that the combined administration of TMZ and oral cannabinoids could be therapeutically exploited for the management of GBM.

Ectopic expression of E3 ubiquitin-protein ligase 2 in glioma and enhances resistance to apoptosis through activating nuclear factor κ-light-chain-enhancer of B cells

Nuclear factor κ-light-chain-enhancer of B cells (NF-κB) is one of the most important tumorigenic factors. Although it has been established that NF-κB is overly activated in human glioma cells, the molecular mechanisms that lead to the signal transduction to NF-κB and thereby the induction of resistance to apoptosis remain poorly understood. The present study demonstrated that mRNA and protein levels of E3 ubiquitin-protein ligase 2 (MIB2) were markedly upregulated in glioma cell lines and clinical samples. Immunohistochemical analysis also revealed high levels of MIB2 expression in glioma specimens. Ectopic overexpression of MIB2 was established in glioma cell lines to investigate its fundamental roles in the response of human glioma to apoptotic inducers. The results indicated that ultraviolet irradiation-induced cell apoptosis was inhibited with MIB2 overexpression in glioma cells. Notably, knockdown of MIB2 using RNA interference was able to increase the sensitivity of glioma cells to the pro-apoptotic agents. The present study identified that MIB2 induces NF-κB activation and facilitates the resistance of glioma cell to apoptosis. It was proposed that MIB2 may not only be an important hallmark to glioma disease progression, but that it may also offer novel clinical strategies to overcome resistance to cancer therapies.

ALA-PpIX mediated photodynamic therapy of malignant gliomas augmented by hypothermia

Background

Malignant gliomas are highly invasive, difficult to treat, and account for 2% of cancer deaths worldwide. Glioblastoma Multiforme (GBM) comprises the most common and aggressive intracranial tumor. The study hypothesis is to investigate the modification of Photodynamic Therapy (PDT) efficacy by mild hypothermia leads to increased glioma cell kill while protecting normal neuronal structures.

Methods

Photosensitizer accumulation and PDT efficacy in vitro were quantified in various glioma cell lines, primary rat neurons, and astrocytes. In vivo studies were carried out in healthy brain and RG2 glioma of naïve Fischer rats. Hypothermia was induced at 1 hour pre- to 2 hours post-PDT, with ALA-PpIX accumulation and PDT treatments effects on tumor and normal brain PDT quantified using optical spectroscopy, histology, immunohistochemistry, MRI, and survival studies, respectively.

Findings

In vitro studies demonstrated significantly improved post-PDT survival in primary rat neuronal cells. Rat in vivo studies confirmed a neuroprotective effect to hypothermia following PpIX mediated PDT by T₂ mapping at day 10, reflecting edema/inflammation volume reduction. Mild hypothermia increased PpIX fluorescence in tumors five-fold, and the median post-PDT rat survival time (8.5 days normothermia; 14 days hypothermia). Histology and immunohistochemistry show close to complete cellular protection in normal brain structures under hypothermia.

Conclusions

The benefits of hypothermia on both normal neuronal tissue as well as increased PpIX fluorescence and RG2 induced rat survival strongly suggest a role for hypothermia in photonics-based surgical techniques, and that a hypothermic intervention could lead to considerable patient outcome improvements.

Downregulation of LKB1 promotes tumor progression and predicts unfavorable prognosis in patients with glioma

The liver kinase B1 (LKB1)/5′-adenosine monophosphate-activated protein kinase pathway has been reported to facilitate glioma cell growth by improving growth conditions. To investigate the clinical significance of LKB1 in human gliomas western blot analysis and quantitative polymerase chain reaction experiments were performed. The present study demonstrated that LKB1 expression was markedly decreased at the messenger RNA and protein levels in 30 freshly prepared glioma tissues, compared with non-neoplastic brain tissues (P<0.001). Subsequently, immunohistochemical analysis demonstrated that LKB1 immunostaining in 180 glioma tissues was significantly decreased compared with that in the corresponding non-neoplastic brain tissues (P<0.001). Notably, this downregulation frequently occurred in high-grade gliomas, and statistical analysis revealed that low LKB1 expression was significantly associated with large tumor size (P=0.02), advanced World Health Organization grade (P=0.006) and low Karnofsky performance scale (P=0.01). The prognostic value of LKB1 expression in patients with glioma was additionally evaluated using Kaplan-Meier survival curves and Cox proportional hazards regression models. As a result, the overall survival time of patients with glioma with low LKB1 expression was shorter compared with that of patients with high LKB1 expression (P<0.001), and low LKB1 expression also indicated decreased survival time in patients with high-grade glioma (P<0.001). Collectively, the present data indicated that the downregulation of LKB1 was closely associated with the malignant degree of human gliomas, exhibiting lower expression at a higher grade. Notably, LKB1 may serve as a potential prognostic biomarker for patients with glioma following surgery.

Inhibition of NADPH Oxidase-4 Potentiates 2-Deoxy-D-Glucose-Induced Suppression of Glycolysis, Migration, and Invasion in Glioblastoma Cells: Role of the Akt/HIF1α/HK-2 Signaling Axis

AIMS

2-Deoxy-d-glucose (2-DG), a synthetic glycolytic inhibitor, is currently under clinical evaluation as a promising anticancer agent. However, 2-DG treatment in cancer cells activates prosurvival Akt signaling that might limit its clinical efficacy. The NADPH oxidase 4 (Nox-4)/reactive oxygen species/Akt signaling is known to regulate survival, proliferation, infiltration, and invasion in glioblastomas (GBMs). The enhanced motility, invasiveness, and therapy resistance in GBMs are attributed to metabolic adaptation through increased aerobic glycolysis. Therefore, we hypothesized that inhibition of the Nox-4 might enhance 2-DG-induced suppression of glycolysis, migration, and invasion in GBM cells.

RESULTS

We identified the natural naphthoquinone compound shikonin as a potent inhibitor of the Nox-4/Akt signaling pathway. The combined treatment of shikonin+2-DG suppressed the glycolytic phenotype, migration, and invasion through modulation of the Akt/HIF1α/hexokinase-2 signaling axis in GBM cells. The combination also exhibited enhanced antiproliferative and antiangiogenic effects in vivo.

INNOVATION

Our data for the first time demonstrate that inhibition of the Nox-4-associated prosurvival signaling pathway by shikonin enhances the antiproliferative and antiangiogenic potential of 2-DG in GBM cells.

CONCLUSION

In summary, the combined inhibition of Nox-4 and glycolysis may have therapeutic implications for the management of GBMs.

Probucol suppresses human glioma cell proliferation in vitro via ROS production and LKB1-AMPK activation

AIM

Probucol, an anti-hyperlipidemic drug, has been reported to exert antitumor activities at various stages of tumor initiation, promotion and progression. In this study we examined whether the drug affected glioma cell growth in vitro and the underlying mechanisms.

METHODS

Human glioma U87 and glioblastoma SF295 cell lines were used. Cell proliferation was accessed using the cell proliferation assay and BrdU incorporation. The phosphorylation of AMPK, liver kinase B1 (LKB1) and p27(Kip1) was detected by Western blot. The activity of 26S proteasome was assessed with an in situ fluorescent substrate. siRNAs were used to suppress the expression of the relevant signaling proteins.

RESULTS

Treatment of U87 glioma cells with probucol (10-100 μmol/L) suppressed the cell proliferation in dose- and time dependent manners. Meanwhile, probucol markedly increased the ROS production, phosphorylation of AMPK at Thr172 and LKB1 at Ser428 in the cells. Furthermore, probucol significantly decreased 26S proteasome activity and increased p27(Kip1) protein level in the cells in an AMPK-dependent manner. Probucol-induced suppression of U87 cell proliferation could be reversed by pretreatment with tempol (a superoxide dismutase mimetic), MG132 (proteasome inhibitor) or compound C (AMPK inhibitor), or by gene silencing of LKB1, AMPK or p27(Kip1). Similar results were observed in probucol-treated SF295 cells.

CONCLUSION

Probucol suppresses human glioma cell proliferation in vitro via ROS production and LKB1-AMPK activation, which reduces 26S proteasome-dependent degradation of p27(Kip1).

Transcriptional network analysis reveals that AT1 and AT2 angiotensin II receptors are both involved in the regulation of genes essential for glioma progression

Gliomas are aggressive primary brain tumors with high infiltrative potential. The expression of Angiotensin II (Ang II) receptors has been associated with poor prognosis in human astrocytomas, the most common type of glioma. In this study, we investigated the role of Angiotensin II in glioma malignancy through transcriptional profiling and network analysis of cultured C6 rat glioma cells exposed to Ang II and to inhibitors of its membrane receptor subtypes. C6 cells were treated with Ang II and specific antagonists of AT1 and AT2 receptors. Total RNA was isolated after three and six hours of Ang II treatment and analyzed by oligonucleotide microarray technology. Gene expression data was evaluated through transcriptional network modeling to identify how differentially expressed (DE) genes are connected to each other. Moreover, other genes co-expressing with the DE genes were considered in these analyses in order to support the identification of enriched functions and pathways. A hub-based network analysis showed that the most connected nodes in Ang II-related networks exert functions associated with cell proliferation, migration and invasion, key aspects for glioma progression. The subsequent functional enrichment analysis of these central genes highlighted their participation in signaling pathways that are frequently deregulated in gliomas such as ErbB, MAPK and p53. Noteworthy, either AT1 or AT2 inhibitions were able to down-regulate different sets of hub genes involved in protumoral functions, suggesting that both Ang II receptors could be therapeutic targets for intervention in glioma. Taken together, our results point out multiple actions of Ang II in glioma pathogenesis and reveal the participation of both Ang II receptors in the regulation of genes relevant for glioma progression. This study is the first one to provide systems-level molecular data for better understanding the protumoral effects of Ang II in the proliferative and infiltrative behavior of gliomas.

Reactive oxygen species-dependent nitric oxide production in reciprocal interactions of glioma and microglial cells

Conditioned mediums (CMs) from glioma cells U87, GBM-8401, and C6 significantly induced iNOS protein and NO production by microglial cells BV-2 but without altering the cell viability or cell-cycle progression of BV2 microglia. Significant increases in intracellular peroxide by U87-CM and C6-CM were detected by a DCHF-DA assay, and vitamin (Vit) C and N-acetyl cysteine (NAC)-reduced intracellular peroxide levels elicited by CMs lead to inhibition of iNOS/NO production The extracellular signal-regulated kinase (ERK) inhibitor, U0126, and c-Jun N-terminal kinase (JNK) inhibitor, SP600125, suppressed U87-CM- and C6-CM-induced iNOS/NO production by respectively blocking phosphorylated ERK (pERK) and JNK (pJNK) protein expressions stimulated by U87-CM and C6-CM. Increased migration of U87 and C6 glioma cells by a co-culture with BV-2 microglial cells or adding the nitric oxide (NO) donor, sodium nitroprusside (SNP) was observed, and that was blocked by adding an NO synthase (NOS) inhibitor, N-nitro L-arginine methyl ester (NAME). Contributions of ROS, pERK, and pJNK to the migration of glioma cells was further demonstrated in a transwell coculture system of U87 and C6 gliomas with BV-2 microglial cells. Furthermore, expressions of tumor necrosis factor (TNF)-α and monocyte chemoattractant protein (MCP)-1 messenger (m)RNA in U87 and C6 cells were detected by an RT-PCR, and TNF-α and MCP-1 induced iNOS protein expression in time- and concentration-dependent manners. Neutralization of TNF-α or MCP-1 in U87-CM and C6-CM using a TNF-α or MCP-1 antibody inhibited iNOS protein expression, and increased intracellular peroxide by TNF-α or MCP-1 was identified in BV-2 cells. The reciprocal activation of glioma cells and microglia via ROS-dependent iNOS/NO elevation at least partially mediated by TNF-α and MCP-1 is elucidated.

Bradykinin antagonists and thiazolidinone derivatives as new potential anti-cancer compounds

Glioblastoma (GB), the most aggressive brain tumour, and mantle cell lymphoma (MCL), a rare but very aggressive type of lymphoma, are highly resistant to chemotherapy. GB and MCL chemotherapy gives very modest results, the vast majority of patients experience recurrent disease. To find out the new treatment modality for drug-resistant GB and MCL cells, combining of bradykinin (BK) antagonists with conventional temozolomide (TMZ) treatment, and screening of thiazolidinones derivatives were the main objectives of this work. As it was revealed here, BKM-570 was the lead compound among BK antagonists under investigation (IC50 was 3.3 μM) in human GB cells. It strongly suppressed extracellular signal-regulated kinases 1/2 (ERK1/2) and protein kinase B (AKT) phosphorylation. BK antagonists did not decrease the viability of MCL cells, thus showing the cell-specific mode, while thiazolidinone derivatives, a novel group of promising anti-tumour compounds inhibited proliferation of MCL cells: IC₅₀ of ID 4526 and ID 4527 compounds were 0.27 μM and 0.16 μM, correspondingly. However, single agents are often not effective in clinic due to activation of collateral pathways in tumour cells. We demonstrated a strong synergistic effect after combinatorial treatment by BKM-570 together with TMZ that drastically increased cytotoxic action of this drug in rat and human glioma cells. Small proportion of cells was still viable after such treatment that could be explained by presence of TMZ-resistant cells in the population. It is possible to expect that the combined therapy aimed simultaneously at different elements of tumourigenesis will be more effective with lower drug concentrations than the first-line drug temozolomide used alone in clinics.

Modulation of PPIX synthesis and accumulation in various normal and glioma cell lines by modification of the cellular signaling and temperature

Effective therapies for malignant gliomas are still elusive and limited survival improvements are provided only by Temozolomide or fluorescence guided resection. The efficacy of photodynamic therapy (PDT) in this indication is limited by the higher sensitivity of normal brain structures compared to glioma necessitating a modulation of its sensitivity. We evaluate the influence of hypothermia and the tyrosine kinase inhibitor Erlotinib on cell's ability to synthesize PPIX following the administration of ALA which was not previously investigated. We demonstrate that both hypothermia and Erlotinib are favorable in PPIX selectivity as only glioma cell lines demonstrate an increased PPIX synthesis, whereas the neuronal and astrocytic synthesis is remaining unaffected. The results are encouraging to consider hypothermia and Erlotinib as adjuvant therapies to increase the PDT therapeutic index between GBM and normal intracranial tissues, as well as to improve contrast in fluorescence guided resection.

Apoptosis imaging for monitoring DR5 antibody accumulation and pharmacodynamics in brain tumors noninvasively

High-grade gliomas often possess an impaired blood-brain barrier (BBB), which allows delivery of large molecules to brain tumors. However, achieving optimal drug concentrations in brain tumors remains a significant hurdle for treating patients successfully. Thus, detailed investigations of drug activities in gliomas are needed. To investigate BBB penetration, pharmacodynamics, and tumor retention kinetics of an agonistic DR5 antibody in a brain tumor xenograft model, we utilized a noninvasive imaging method for longitudinal monitoring of apoptosis induction. Brain tumors were induced by intracranial (i.c.) implantation of a luciferase-expressing tumor cell line as a reporter. To quantify accumulation of anti-DR5 in brain tumors, we generated a dosage-response curve for apoptosis induction after i.c. delivery of fluorescence-labeled anti-DR5 at different dosages. Assuming 100% drug delivery after i.c. application, the amount of accumulated antibody after i.v. application was calculated relative to its apoptosis induction. We found that up to 0.20% to 0.97% of antibody delivered i.v. reached the brain tumor, but that apoptosis induction declined quickly within 24 hours. These results were confirmed by three-dimensional fluorescence microscopy of antibody accumulation in explanted brains. Nonetheless, significant antitumor efficacy was documented after anti-DR5 delivery. We further demonstrated that antibody penetration was facilitated by an impaired BBB in brain tumors. These imaging methods enable the quantification of antibody accumulation and pharmacodynamics in brain tumors, offering a holistic approach for assessment of central nervous system-targeting drugs.

Role of methamphetamine on glioblastoma cytotoxicity induced by doxorubicin and methotrexate

Glioblastoma multiforme (GBM) is the most common and malignant primary brain tumor with a high mortality rate. Doxorubicin (DOX) and methotrexate (MTX) showed to be effective against a wide range of tumors, but its use in GBM treatment is limited in part due to the inability to cross the blood-brain barrier (BBB). Based on recent studies demonstrating that methamphetamine (METH) increases BBB permeability, we hypothesized that it could be used as a pharmacological tool to allow the entry of potential therapeutic drugs into the brain. Nevertheless, before attempting this approach it is crucial to understand the cytotoxicity of such drug combinations. Herein, we evaluated the effects of METH on cell viability, migration, chemotaxis, and cell cycle, as well as its modulator effects on DOX or MTX-induced cytotoxicity in a human U118 GBM cell line. Our results demonstrated that both chemotherapeutic drugs DOX and MTX induced a pronounced decrease in cell viability, migration, and chemotaxis, and led to a cell cycle arrest at G2 and S phases, respectively. Additionally, METH (1 μM) neither interfered with U-118 cell viability, migration, or cell cycle nor modified DOX- or MTX-induced cytotoxicity. Noteworthy, METH by itself impaired cell chemotaxis with a similar effect to that induced by DOX or MTX alone. Overall, we can conclude that both DOX and MTX are highly cytotoxic against GBM cells and that METH, at a concentration previously shown to increase endothelial cell permeability without leading to cell death, does not interfere with the cytotoxicity of both chemotherapeutic drugs.

MicroRNA as potential modulators in chemoresistant high-grade gliomas

Gliomas account for 70% of human malignant primary brain tumours. The most common form is glioblastoma multiforme, World Health Organization grade IV. Despite the implementation of post-operative adjuvant radiotherapy with concurrent temozolomide (TMZ), the disease's overall prognosis remains dismal. TMZ is currently the only mono-chemotherapeutic agent for newly-diagnosed high-grade glioma patients and acquired resistance inevitably occurs in the majority of such patients, further limiting treatment options. Therefore, there is an urgent need to better understand the underlying mechanisms involved in TMZ resistance, a critical step to developing effective, targeted treatments. An emerging body of evidence suggests the intimate involvement of a novel class of nucleic acid, microRNA (miRNA), in tumorigenesis and disease progression for a number of human malignancies, including primary brain tumours. miRNA are short, single-stranded, non-coding RNA (∼22 nucleotides) that function as post-transcriptional regulators of gene expression. This review provides an overview of the key treatment obstacles faced in patients with high-grade gliomas, especially in the context of recurrent, chemoresistant tumours and the potential roles of miRNA in chemoresistance and management of this disease.

Glycogen synthase kinase-3β (GSK-3β) and its dysregulation in glioblastoma multiforme

Glioblastoma multiforme (GBM) is the most frequently occurring and devastating human brain malignancy, retaining almost universal mortality and a median survival of only 14 months, even with recent advances in multimodal treatments. Gliomas are characterised as being both highly resistant to chemo- and radiotherapy and highly invasive, rendering conventional interventions palliative. The continual dismal prognosis for GBM patients identifies an urgent need for the evolutionary development of new treatment modalities. This includes molecular targeted therapies as many signaling molecules and associated pathways have been implicated in the development and survival of malignant gliomas including the protein kinase, glycogen synthase kinase 3 beta (GSK-3β). Here we review the activity and function of GSK-3β in a number of signaling pathways and its role in gliomagenesis.

ERK and PI3K signaling cascades induce Nrf2 activation and regulate cell viability partly through Nrf2 in human glioblastoma cells

The ERK and PI3K signaling cascades are aberrantly activated in human glioblastoma cells, resulting in the dysregulation of numerous downstream transcription factors. The dark side of the transcription factor, NF-E2-related factor 2 (Nrf2) in human cancer has been revealed. It has been accepted that high levels of Nrf2 promote tumor progression. In the present study, we investigated the effect of the ERK and PI3K signaling cascades on Nrf2 in human glioblastoma cells. Immunohistochemical staining for Nrf2 in clinical specimens showed that the expression and nuclear localization of Nrf2 were increased in human glioblastoma tissues when compared to peritumoral normal tissues. In addition, we detected decreased nuclear localization of Nrf2 following combined treatment with ERK and PI3K inhibitors in three human glioblastoma cell lines and selected the cell line (U251) most sensitive to the inhibitors for further study. Our data demonstrated that inhibition of ERK and PI3K not only suppressed the nuclear accumulation of Nrf2 protein but also decreased the expression of the Nrf2 protein. In addition, combined inhibition of ERK and PI3K also decreased the mRNA levels of Nrf2 target genes. Finally, we found that Nrf2 overexpression partly reversed the ERK and PI3K inhibitor-induced inhibition of cell viability. Therefore, the ERK and PI3K signaling cascades regulate the expression and activation of Nrf2 and control cell viability partly through Nrf2 in U251 human glioblastoma cells. Thus, targeting the ERK and PI3K signaling cascades for Nrf2 activation may provide new methods for the treatment of glioblastoma.

The role of Stat3 in glioblastoma multiforme

Glioblastoma multiforme (GBM) is the most common brain tumor and has the worst prognosis. Several signaling molecules have been clearly implicated in the development, progression, and aggressiveness of GBM. Here we review the role of signal transducer and activator of transcription-3 (Stat3) in GBM. We particularly focus on its expression in clinical GBM samples, its role in brain tumorigenicity in cell lines and animal models, and discuss possible therapeutic strategies targeting Stat3. This review also summarizes the current knowledge regarding the role of Stat3 regulation by upstream activators and repressors in promoting GBM progression in both translational and clinical studies.

Combined RNAi-mediated suppression of Rictor and EGFR resulted in complete tumor regression in an orthotopic glioblastoma tumor model

The PI3K/AKT/mTOR pathway is commonly over activated in glioblastoma (GBM), and Rictor was shown to be an important regulator downstream of this pathway. EGFR overexpression is also frequently found in GBM tumors, and both EGFR and Rictor are associated with increased proliferation, invasion, metastasis and poor prognosis. This research evaluated in vitro and in vivo whether the combined silencing of EGFR and Rictor would result in therapeutic benefits. The therapeutic potential of targeting these proteins in combination with conventional agents with proven activity in GBM patients was also assessed. In vitro validation studies were carried out using siRNA-based gene silencing methods in a panel of three commercially available human GBM cell lines, including two PTEN mutant lines (U251MG and U118MG) and one PTEN-wild type line (LN229). The impact of EGFR and/or Rictor silencing on cell migration and sensitivity to chemotherapeutic drugs in vitro was determined. In vivo validation of these studies was focused on EGFR and/or Rictor silencing achieved using doxycycline-inducible shRNA-expressing U251MG cells implanted orthotopically in Rag2M mice brains. Target silencing, tumor size and tumor cell proliferation were assessed by quantification of immunohistofluorescence-stained markers. siRNA-mediated silencing of EGFR and Rictor reduced U251MG cell migration and increased sensitivity of the cells to irinotecan, temozolomide and vincristine. In LN229, co-silencing of EGFR and Rictor resulted in reduced cell migration, and increased sensitivity to vincristine and temozolomide. In U118MG, silencing of Rictor alone was sufficient to increase this line’s sensitivity to vincristine and temozolomide. In vivo, while the silencing of EGFR or Rictor alone had no significant effect on U251MG tumor growth, silencing of EGFR and Rictor together resulted in a complete eradication of tumors. These data suggest that the combined silencing of EGFR and Rictor should be an effective means of treating GBM.

Ariadne's ChemEffect and Pathway Studio knowledge base

IMPORTANCE OF THE FIELD

Drug discovery and development is a very complex and costly process. Understanding the detailed molecular mechanisms of a disease and drug actions can make it more efficient not only for new target discovery but also for lead prioritization, drug repositioning and development of biomarkers for drug efficacy and safety. Access to formalized knowledge about functions of proteins and small molecules is crucial for rationalization of the drug development process, and scientific publications are the main source of this knowledge. Protein knowledge networks capturing protein functions, protein-protein relations and organization of proteins in complex cellular sub-systems are making their way into modern drug discovery. Chemical networks representing multiple aspects of chemical functional information integrated into a protein systems biology network is even more advanced and promising paradigm.

AREAS COVERED IN THIS REVIEW

This review describes utilization of literature-derived protein and chemical functional knowledge bases in drug development.

WHAT THE READER WILL GAIN

Readers will gain an understanding of how integrated protein and chemical knowledge networks can be used for understanding and building the models of cellular events, disease mechanisms, and drug actions, finding biomarkers of drug efficacy and safety, as well as interpretation of high-throughput gene expression, proteomic and metabolomic experiments.

TAKE HOME MESSAGE

Integrated literature-derived protein and chemical knowledge bases can rationalize many aspects of drug development process including drug repositioning and biomarker design.

Ginkgo biloba leaf extract improves the cognitive abilities of rats with D-galactose induced dementia

Standardized Ginkgo biloba leaf extract has been used in clinical trials for its beneficial effects on brain functions, particularly in dementia. Substantial experimental evidences indicated that Ginkgo biloba leaf extract (EGB) protected neuronal cells from a variety of insults. We investigated the effect of EGB on cognitive ability and protein kinase B (PKB) activity in hippocampal neuronal cells of dementia model rats. Rats received an intraperitoneal injection of D-galactose to induce dementia. Forty-eight Spraque-Dawley rats were randomly divided into six groups, including the control group, D-galactose group (Gal), low-dose EGB group (EGB-L), mid-dose EGB group (EGB-M), high-dose EGB group (EGB-H) and treatment group. The EGB-L, EGB-M and EGB-H groups were administered with EGB and D-galactose simultaneously. Y-maze, cresyl violet staining, TUNEL assays and immunohistochemistry staining were performed to detect learning and memory abilities, morphological changes in the hippocampus, neuronal apoptosis and the expressing level of phospho-PKB, respectively. Rats in the Gal group showed decreased abilities of learning and memory, and hippocampal pyramidal cell layer was damaged, while EGB administration improved learning and memory abilities. The Gal group exhibited many stained, condensed nuclei and micronuclei, either isolated or within the cytoplasm of cells (39.5±1.4). Apoptotic cells decreased in the groups of EGB-L (35.9±0.9), EGB-M (16.8±1.0) and EGB-H (10.1±0.8), and there were statistical significances compared with the Gal group. Immunoreactivity of phospho-PKB was localized diffusely throughout the cytosol of cells in all groups, while the immunoreactivity of the Gal group was weak. EGB significantly attenuated learning and memory impairment in a dose-dependent manner, while it could decrease the nmber of TUNEL-positive cells, and increase the activity of PKB. Our results demonstrated that EGB attenuated memory impairment and cell apoptosis in galactose-induced dementia model rats by activating PKB.

Triggering of the TRPV2 channel by cannabidiol sensitizes glioblastoma cells to cytotoxic chemotherapeutic agents

The aggressive behavior of Glioblastoma multiforme (GBM) is mainly due to high invasiveness and proliferation rate as well as to high resistance to standard chemotherapy. Several chemotherapeutic agents like temozolomide (TMZ), carmustine (BCNU) or doxorubicin (DOXO) have been employed for treatment of GBM, but they display limited efficacy. Therefore, it is important to identify new treatment modalities to improve therapeutic effects and enhance GBM chemosensitivity. Recently, activation of the transient receptor potential vanilloid type 2 (TRPV2) has been found to inhibit human GBM cell proliferation and overcome BCNU resistance of GBM cells. Herein, we evaluated the involvement of cannabidiol (CBD)-induced TRPV2 activation, in the modulation of glioma cell chemosensitivity to TMZ, BCNU and DOXO. We found that CBD increases TRPV2 expression and activity. CBD by triggering TRPV2-dependent Ca(2+) influx increases drug uptake and synergizes with cytotoxic agents to induce apoptosis of glioma cells, whereas no effects were observed in normal human astrocytes. Moreover, as the pore region of transient receptor potential (TRP) channels is critical for ion channel permeation, we demonstrated that deletion of TRPV2 poredomain inhibits CBD-induced Ca(2+) influx, drug uptake and cytotoxic effects. Overall, we demonstrated that co-administration of cytotoxic agents together with the TRPV2 agonist CBD increases drug uptake and parallelly potentiates cytotoxic activity in human glioma cells.

Regulation of glycogen synthase kinase-3 beta (GSK-3β) by the Akt pathway in gliomas

Gliomas are aggressive brain tumours that, despite advances in multimodal therapies, continue to portend a dismal prognosis. Glioblastoma multiforme (GBM) represents the most aggressive glioma and patients have a median survival of 14 months, even with the best available treatments. The phosphoinositide 3-kinase/Akt/glycogen synthase kinase-3 beta (GSK-3β) and Wnt/β-catenin pathways are dysregulated in a number of cancers, and these two pathways share a common node protein, GSK-3β. This protein is responsible for the regulation/degradation of β-catenin, which reduces β-catenin's translocation to the nucleus and influences the subsequent transcription of oncogenes. The non-specific small-molecule GSK-3β inhibitor, lithium chloride (LiCl), and the specific Akt inhibitor, AktX, were used to treat U87MG and U87MG.Δ2-7 human glioma cell lines. LiCl treatment significantly affected cell morphology of U87MG and U87MG.Δ2-7 cells, while also increasing levels of phospho-GSK-3β in a dose-dependent manner. Increased cell proliferation was observed at low-to-mid LiCl concentrations as determined by MTT cell growth assays. Treatment of U87MG and U87MG.Δ2-7 cells with AktX resulted in reduced levels of phospho-GSK-3β through its inhibition of Akt, in addition to decreased levels of phosphorylated (active) Akt in a dose-dependent fashion. We have shown in this study that GSK-3β regulation by phosphorylation is important for cell morphology and growth, and that LiCl enhances growth of U87MG and U87MG.Δ2-7 cells by inhibiting GSK-3β through its phosphorylation, whereas AktX reduces growth via activation of GSK-3β by inhibiting Akt's kinase activity.

Nix protein positively regulates NF-κB activation in gliomas

Previous reports indicate that the NIX/BNIP3L gene acts as a pro-apoptotic factor by interacting with BCL2 and BCL-XL, playing an important role in hypoxia-dependent cell death and acting as a tumor suppressor. However, many studies also showed that NIX is linked to a protective role and cell survival in cancer cells. Nuclear factor-κB (NF-κB) can attenuate apoptosis in human cancers in response to chemotherapeutic agents and ionizing radiation. We observed an absence of i-κBα (NF-κB activation inhibitor) expression, but a greater expression of Nix and p-NF-κB proteins in the Nix-wt U251 cells, which was not observed in the Nix-kn cells under hypoxic conditions. Using electrophoretic mobility shift assay (EMSA) and luciferase detection, the activation of NF-κB was detected only in the Nix-wt U251 cells with hypoxia. These data imply that Nix protein might play a role in the positive regulation of the NF-κB pathway. Moreover, 46 cases of glioma also showed high levels of Nix protein expression, which was always accompanied by high p-NF-κB expression. Patients with Nix (+) showed less tissue apoptosis behavior in glioblastoma (GBM), unlike that observed in the Nix-negative patients (-). The same apoptotic tendency was also identified in anaplastic astrocytoma (AA) groups, but not in astrocytoma (AS). On analyzing the Kaplan-Meier curve, better tumor-free survival was observed only in cases of astrocytoma, and not in AA and GBM. Thus, our study indicates that Nix protein might have multiple functions in regulating glioma behaviors. In the low-grade gliomas (astrocytoma) with low expression of NF-κB, the cell death-inducing function that occurs through a Bax mechanism might predominate and act as a tumor suppressor. While in the malignant gliomas (AA and GBM), with higher expression of the NIX gene and with activity of the NF-κB pathway, the oncogene function of Nix was predominant.

Wnt inhibitory factor-1 regulates glioblastoma cell cycle and proliferation

Wnt proteins are powerful regulators of cell proliferation and differentiation, and activation of the Wnt signalling pathway is involved in the pathogenesis of several types of human tumours. Wnt inhibitory factor-1 (WIF-1) acts as a Wnt antagonist and tumour suppressor. Previous studies have shown that reducing expression of the WIF-1 gene aberrantly activates Wnt signalling and induces the development of certain types of cancers. In the present study, we examined the expression of WIF-1 in human primary glioblastoma multiforme (GBM) tumours. Studies using semiquantitative reverse transcription-polymerase chain reaction and immunohistochemical analysis revealed that WIF-1 expression is lower in human GBM than in normal brain tissue. To clarify the role of WIF-1, we transfected U251 human glioblastoma-derived cells, which do not express WIF-1, with the pcDNA3.1-WIF1 vector to restore WIF-1 expression. The results of cell proliferation, colony formation and apoptosis assays, as well as flow cytometry, indicate that exogenous WIF-1 has no effect on U251 cell apoptosis, but does arrest cells at the G(0)/G(1) phase and inhibit cell growth. Collectively, our data suggest that WIF-1 is a potent inhibitor of GBM growth.

Impairment of the cell-to-matrix adhesion and cytotoxicity induced by the Mediterranean jellyfish Pelagia noctiluca venom and its fractions in cultured glioblastoma cells

Background

The biodiversity of the marine environment and the associated chemical diversity constitute a practically unlimited source of new active substances in the field of the development of bioactive products. In our study, we have investigated the efficiency of the venom from the Mediterranean jellyfish, Pelagia noctiluca and its fractions for anti-proliferative and anti-cell adhesion to cell–extracellular matrix activities.

Results

Our experiments have indicated that the separation of the Mediterranean jellyfish Pelagia noctiluca crude venom extract by sephadex G-75 chromatography led to four fractions (F1, F2, F3, and F4). Among the four fractions F1 and F3 were cytotoxic against U87 cells with IC50 values of 125 and 179 μg/ml respectively. The venom, F1, F2 and F 3 showed significant anti-proliferative activity in time-dependent manner. Our results also suggest that these fractions and the venom are able to inhibit cell adhesion to fibrinogen in dose-dependent manner. This inhibition is reliant on its ability to interact with integrins.

Conclusions

To conclude, we have demonstrated for the first time that Pelagia noctiluca venom and its fractions especially (F1 and F2) display potent anti-tumoral properties. Separation by sephadex G-75 chromatography give rise to more active fractions than the crude venom extract. The purification and the determination of chemical structures of compounds of these active fractions are under investigation. Overall, Pelagia noctiluca venom may has the potential to serve as a template for future anticancer-drug development.

2-Hydroxyoleate, a nontoxic membrane binding anticancer drug, induces glioma cell differentiation and autophagy

Despite recent advances in the development of new cancer therapies, the treatment options for glioma remain limited, and the survival rate of patients has changed little over the past three decades. Here, we show that 2-hydroxyoleic acid (2OHOA) induces differentiation and autophagy of human glioma cells. Compared to the current reference drug for this condition, temozolomide (TMZ), 2OHOA combated glioma more efficiently and, unlike TMZ, tumor relapse was not observed following 2OHOA treatment. The novel mechanism of action of 2OHOA is associated with important changes in membrane-lipid composition, primarily a recovery of sphingomyelin (SM) levels, which is markedly low in glioma cells before treatment. Parallel to membrane-lipid regulation, treatment with 2OHOA induced a dramatic translocation of Ras from the membrane to the cytoplasm, which inhibited the MAP kinase pathway, reduced activity of the PI3K/Akt pathway, and downregulated Cyclin D-CDK4/6 proteins followed by hypophosphorylation of the retinoblastoma protein (RB). These regulatory effects were associated with induction of glioma cell differentiation into mature glial cells followed by autophagic cell death. Given its high efficacy, low toxicity, ease of oral administration, and good distribution to the brain, 2OHOA constitutes a new and potentially valuable therapeutic tool for glioma patients.

Epothilone B inhibits migration of glioblastoma cells by inducing microtubule catastrophes and affecting EB1 accumulation at microtubule plus ends

Invasion of normal brain tissue by tumor cells is a major contributing factor to the recurrence of glioblastoma and its resistance to therapy. Here, we have assessed the efficacy of the microtubule (MT) targeting agent Epothilone B (patupilone) on glioblastoma cell migration, a prerequisite for invasive tumor cell behavior. At non-cytotoxic concentrations, patupilone inhibited glioblastoma cell movement, as shown by transwell cell migration, random motility and spheroid assays. This anti-migratory effect was associated with a reduced accumulation of EB1 and other MT plus end tracking proteins at MT ends and with the induction of MT catastrophes, while the MT growth rate and other MT dynamic instability parameters remained unaltered. An increase in MT catastrophes led to the reduction of the number of MTs reaching the leading edge. Analysis of the effect of patupilone on MT dynamics in a reconstituted in vitro system demonstrated that the induction of MT catastrophes and an alteration of EB1 accumulation at MT plus end are intrinsic properties of patupilone activity. We have thus demonstrated that patupilone antagonizes glioblastoma cell migration by a novel mechanism, which is distinct from suppression of MT dynamic instability. Taken together, our results suggest that EB proteins may represent a new potential target for anti-cancer therapy in highly invasive tumors.

A combined preclinical therapy of cannabinoids and temozolomide against glioma

Glioblastoma multiforme (GBM) is highly resistant to current anticancer treatments, which makes it crucial to find new therapeutic strategies aimed at improving the poor prognosis of patients suffering from this disease. Δ(9)-Tetrahydrocannabinol (THC), the major active ingredient of marijuana, and other cannabinoid receptor agonists inhibit tumor growth in animal models of cancer, including glioma, an effect that relies, at least in part, on the stimulation of autophagy-mediated apoptosis in tumor cells. Here, we show that the combined administration of THC and temozolomide (TMZ; the benchmark agent for the management of GBM) exerts a strong antitumoral action in glioma xenografts, an effect that is also observed in tumors that are resistant to TMZ treatment. Combined administration of THC and TMZ enhanced autophagy, whereas pharmacologic or genetic inhibition of this process prevented TMZ + THC-induced cell death, supporting that activation of autophagy plays a crucial role on the mechanism of action of this drug combination. Administration of submaximal doses of THC and cannabidiol (CBD; another plant-derived cannabinoid that also induces glioma cell death through a mechanism of action different from that of THC) remarkably reduces the growth of glioma xenografts. Moreover, treatment with TMZ and submaximal doses of THC and CBD produced a strong antitumoral action in both TMZ-sensitive and TMZ-resistant tumors. Altogether, our findings support that the combined administration of TMZ and cannabinoids could be therapeutically exploited for the management of GBM.

Increased transforming growth factor-β2 in epidermal growth factor receptor variant III-positive glioblastoma

To evaluate the influence of epidermal growth factor receptor variant III (EGFRvIII) expression on immune impairment associated with glioblastoma multiforme (GBM), the expression of transforming growth factor beta-2 (TGF-β2) and interleukin-10 (IL-10) were assessed in EGFRvIII-positive and negative GBM samples. In addition, the effects of EGFRvIII expression on U87.MG glioma cell proliferation and invasion as well as TGF-β2 and IL-10 levels were analyzed. GBM samples were obtained from 26 patients who underwent surgical resection. EGFRvIII expression was assessed immunohistochemically and using real-time reverse transcription polymerase chain reaction (RT-PCR), and TGF-β2 and IL-10 levels were determined using real-time RT-PCR. Proliferation and invasion of U87.MG and U87.MG.EGFRvIII glioma cells was assessed using the 3-(4,5-dimethylthiazol-2-Yl)-2,5-diphenyltetrazolium bromide (MTT) assay and Matrigel invasion assays, respectively. Although upregulation of TGF-β2 mRNA expression was observed in EGFRvIII-positive patients, no differences in IL-10 expression levels were detected. A statistically significant increase in cell proliferation and invasion as well as TGF-β2 and IL-10 expression was observed in U87.MG.EGFRvIII cells as compared with U87.MG cells. Associations between EGFRvIII expression and upregulation of immunosuppressive cytokines were observed. EGFRvIII expression was also associated with increased cell proliferation and invasion. Understanding the immunobiology of EGFRvIII-positive GBM patients may assist in the development of novel targeted treatment strategies.

Effect of bone morphogenetic protein 4 in the human brain glioma cell line U251

The role of bone morphogenetic protein 4 (BMP4) in gliomas is not clear. We hypothesized that BMP4 inhibits proliferation in the brain glioma cell line U251 through a signaling pathway involving BMP4 and the mothers against decapentaplegic homolog 4 (SMAD4) protein. We exposed U251 cells to Adriamycin (1 g) for 48 h; cell proliferation (MTT assay), expression of BMP4 and SMAD4 (mRNA: qPCR; protein: Western blot) were studied. We further altered expression of BMP4 by overexpression or siRNA silencing, and documented cell responses to Adriamycin. Proliferation of U251 cells was significantly inhibited upon exposure to Adriamycin. This inhibition was associated with increased expression of BMP4. Further, proliferation of U251 cells was inhibited when BMP4 was overexpressed. BMP4 expression negatively correlated with expression of SMAD4, such that elevated levels of BMP4 were associated with decreased expression of SMAD4 and vice versa. The Adriamycin-induced inhibition of proliferation of U251 cells was attenuated when BMP4 was knocked down by siRNA. To conclude, BMP4 is associated with inhibition of proliferation of U251 cells; the effects of BMP4 involve the BMP4-Smad signaling pathway. BMP4 has a potential as a target for glioma therapy.

Targeting SRC in glioblastoma tumors and brain metastases: rationale and preclinical studies

Glioblastoma (GBM) is an extremely aggressive, infiltrative tumor with a poor prognosis. The regulatory approval of bevacizumab for recurrent GBM has confirmed that molecularly targeted agents have potential for GBM treatment. Preclinical data showing that SRC and SRC-family kinases (SFKs) mediate intracellular signaling pathways controlling key biologic/oncogenic processes provide a strong rationale for investigating SRC/SFK inhibitors, e.g., dasatinib, in GBM and clinical studies are underway. The activity of these agents against solid tumors suggests that they may also be useful in treating brain metastases. This article reviews the potential for using SRC/SFK inhibitors to treat GBM and brain metastases.

IKBKE is over-expressed in glioma and contributes to resistance of glioma cells to apoptosis via activating NF-κB

IκB kinase-ε (IKBKE), a member of the IκB kinase (IKK) family, has been identified as an oncogenic protein and found to be up-regulated in breast cancer, ovarian cancer and prostate cancer. Nonetheless, the expression status and functional significance of IKBKE in human glioma remain unexplored. For the first time, we have demonstrated that mRNA and protein levels of IKBKE were robustly up-regulated in glioma cell lines and human primary glioma tissues. Immunohistochemistry analysis revealed that 53.5% (38/71) paraffin-embedded archived glioma specimens exhibited high levels of IKBKE expression. Intriguingly, there was no significant difference in IKBKE expression among different grades of glioma. To understand the biological function of IKBKE in the development and progression of human glioma, glioma cells lines ectopically over-expressing IKBKE were established and tested for their responsiveness to apoptotic inducers. Our data showed that IKBKE over-expression inhibited cell apoptosis induced by UV irradiation or adriamycin and, in contrast, shRNAi-mediated suppression of IKBKE increased the sensitivity of glioma cells to the apoptotic inducers. Importantly, we found that up-regulated IKBKE could induce the expression of Bcl-2 through activating NF-κB signalling, and that, specifically, we identified IκB as a critical component for this signalling cascade. The current study suggests that up-regulation of IKBKE may represent an important molecular hallmark that is biologically and clinically relevant to the development and progression, as well as the chemo- and radio-resistance, of the disease.

c-Met expression is associated with time to recurrence in patients with glioblastoma multiforme

The aim of this study was to explore the difference in c-Met expression between primary and recurrent glioblastoma multiforme (GBM), and to determine whether the dysregulation of c-Met expression has a role in the malignant progression of GBM. Paired primary and recurrent GBM specimens from the same patient were evaluated using immunohistochemical analysis. The association between c-Met expression and progression-free survival time (PFST) was analyzed. There was a significant difference in c-Met expression between primary and recurrent tumors (p=0.020), and patients with tumors expressing c-Met at a higher level had a significantly shorter PFST (6.1 months vs. 11.5 months; p=0.026). Our study indicates that recurrent GBM express c-Met at a higher level and that c-Met overexpression is associated with shorter PFST in patients with GBM. These findings suggest that c-Met potentially has an important role in the treatment of GBM.

Small molecule kinase inhibitors in glioblastoma: a systematic review of clinical studies

The efficacy of small-molecule kinase inhibitors has recently changed standard clinical practice for several solid cancers. Glioblastoma is a solid cancer that universally recurs and unrelentingly results in death despite maximal surgery and radiotherapy with concomitant and adjuvant temozolomide. Several clinical studies using kinase inhibitors in glioblastoma have been reported. The present study systematically reviews the efficacy, toxicity, and tissue analysis of small-molecule kinase inhibitors in adult patients with glioblastoma as reported in published clinical studies and determines which kinases have been targeted by the inhibitors used in these studies. Publications were retrieved using a MEDLINE search and by screening meeting abstracts. A total of 60 studies qualified for inclusion, of which 25 were original reports. A total of 2385 glioblastoma patients receiving kinase inhibitors could be evaluated. The study designs included 2 phase III studies and 37 phase II studies. Extracted data included radiological response, progression-free survival, overall survival, toxicity, and biomarker analysis. The main findings were that (i) efficacy of small-molecule kinase inhibitors in clinical studies with glioblastoma patients does not yet warrant a change in standard clinical practice and (ii) 6 main kinase targets for inhibitors have been evaluated in these studies: EGFR, mTOR, KDR, FLT1, PKCbeta, and PDGFR.

Alterations in gene expression profiles correlated with cisplatin cytotoxicity in the glioma U343 cell line

Gliomas are the most common tumors in the central nervous system, the average survival time of patients with glioblastoma multiforme being about 1 year from diagnosis, in spite of harsh therapy. Aiming to study the transcriptional profiles displayed by glioma cells undergoing cisplatin treatment, gene expression analysis was performed by the cDNA microarray method. Cell survival and apoptosis induction following treatment were also evaluated. Drug concentrations of 12.5 to 300 μM caused a pronounced reduction in cell survival rates five days after treatment, whereas concentrations higher than 25 μM were effective in reducing the survival rates to ~1%. However, the maximum apoptosis frequency was 20.4% for 25 μM cisplatin in cells analyzed at 72 h, indicating that apoptosis is not the only kind of cell death induced by cisplatin. An analysis of gene expression revealed 67 significantly (FDR < 0.05) modulated genes: 29 of which down- and 38 up-regulated. These genes belong to several classes (metabolism, protein localization, cell proliferation, apoptosis, adhesion, stress response, cell cycle and DNA repair) that may represent several affected cell processes under the influence of cisplatin treatment. The expression pattern of three genes (RHOA, LIMK2 and TIMP2) was confirmed by the real time PCR method.

Orphan nuclear receptor Nur77 is required for the differentiation of C6 glioma cells induced by cholera toxin

AIM

To investigate a possible regulator gene involved in the cholera toxin-induced differentiation of rat C6 glioma cells.

METHODS

The global changes in the mRNA expression pattern induced by cholera toxin were analyzed using gene chip microarray. The selected gene was then silenced by RNA interference or overexpressed with an ORF plasmid to determine its necessity in this process.

RESULTS

Nur77, a member of the orphan nuclear receptor family (NR4A), was markedly up-regulated during the process of differentiation. Furthermore, RNAi of nur77 attenuated the induction effect of cholera toxin on C6 cells, whereas overexpression of nur77 led to similarly differentiated behavior, including morphologic and biomarker changes, as well as cell cycle arrest.

CONCLUSION

Nur77 participated actively and essentially as an important regulator in the cholera toxin-induced differentiation of C6 cells.

High-grade glioma mouse models and their applicability for preclinical testing

High-grade gliomas (WHO grade III anaplastic astrocytoma and grade IV glioblastoma multiforme) are the most common primary tumors in the central nervous system in adults. Unfortunately, despite great efforts in finding better therapies, high-grade glioma remains among the most devastating and deadliest of all human cancers. During recent years, genetic and molecular alterations that underlie this disease have been identified and advanced our basic knowledge about gliomagenesis. Moreover, understanding the molecular biology has also led to the development of genetically engineered mouse models that resemble many of the features of human gliomas. Ideally, such "patient-like" models should be instrumental for preclinical testing of novel therapeutics, but thus far they have not yet been widely implemented for this purpose. This review will discuss the advantages and shortcomings of the established high-grade glioma mouse models with emphasis on their potential applicability for preclinical testing of novel drugs and treatment regimens.

[Expression pattern of invasion-related molecules in brain tumors of different origin]

Tumor cell invasion into the surrounding brain tissue is mainly responsible for the failure of radical surgical resection and successful treatment, with tumor recurrence as microdisseminated disease. Epidermal growth factor receptors (EGFRs), integrins and their ligands in the extracellular matrix (ECM) predominantly participate in the invasion process, including the cell adhesion to the surrounding microenvironment and cell migration. The extent of infiltration of the surrounding brain tissue by malignant tumors strongly depends on the tumor cell type. Malignant gliomas show much more intensive peritumoral invasion than do metastatic tumors. In this study, the mRNA expression of 29 invasion-related molecules (18 cell membrane receptors or receptor subunits (EGFRs and integrins) and 11 ECM components: collagens, laminins and fibronectin) was investigated by quantitative reverse transcriptase-polymerase chain reaction. Fresh frozen human tissue samples from glioblastoma (GBM) and intracerebral bronchial adenocarcinoma metastases (five pieces from each) were evaluated. Significant differences were established in six of the 29 molecules (ErbB1, 2, 3, integrins alpha3, 7 and beta1). To confirm our results at the protein level, immunohistochemical analysis of nine molecules was performed. The staining intensity differed definitely in the case of ErbB1, 2 and integrins alpha3 and beta1. Determining the differences in invasion-related molecules in tumors of different origin can help identify the exact molecular mechanisms that facilitate peritumoral infiltration by glioblastoma cells. These results should allow the selection of target molecules for potential chemotherapeutic agents directed against highly invasive malignant gliomas.