Biology of angiogenesis and invasion in glioma

Oncogenic Activities of IDH1/2 Mutations: From Epigenetics to Cellular Signaling

Gliomas and leukemias remain highly refractory to treatment, thus highlighting the need for new and improved therapeutic strategies. Mutations in genes encoding enzymes involved in the tricarboxylic acid (TCA) cycle, such as the isocitrate dehydrogenases 1 and 2 (IDH1/2), are frequently encountered in astrocytomas and secondary glioblastomas, as well as in acute myeloid leukemias; however, the precise molecular mechanisms by which these mutations promote tumorigenesis remain to be fully characterized. Gain-of-function mutations in IDH1/2 have been shown to stimulate production of the oncogenic metabolite R-2-hydroxyglutarate (R-2HG), which inhibits α-ketoglutarate (αKG)-dependent enzymes. We review recent advances on the elucidation of oncogenic functions of IDH1/2 mutations, and of the associated oncometabolite R-2HG, which link altered metabolism of cancer cells to epigenetics, RNA methylation, cellular signaling, hypoxic response, and DNA repair.

Cofilin-1 and phosphoglycerate kinase 1 as promising indicators for glioma radiosensibility and prognosis

Glioma is a primary malignancy in central nervous system. Radiotherapy has been used as one of the standard treatments for glioma for decades. Since radioresistance can reduce the curative efficacy of radiotherapy in glioma, investigating the cause of radioresistance and predicting the tumour radiosensibility appeared particularly important. We previously reported that CFL1 and PGK1 are over-expressed in radioresistant U251 glioma cells. In this study, the level of CFL1 and PGK1 of 113 glioma tissues were measured by ELISA method. The relevance of the expression of these two proteins to radiosensibility was analyzed by mean test and multivariate logistic regression. The survival analysis was carried out in 85 irradiated patients and 105 followed-up patients respectively. The relationship between protein expression and clinical parameters was explored in overall 113 patients, and the correlation between CFL1 and PGK1 were determined as well. Our results showed that the expression of CFL1 and PGK1 were significantly higher (P < 0.001) in radioresistant patients than others. The multivariate Logistic regression demonstrated that the expression of CFL1 (p < 0.001) and PGK1 (p < 0.001) were associated with radioresistance in glioma. The multivariate Cox regression in overall survival suggested that CFL1 level or PGK1 level could be the independent prognosis factor for poor prognosis in 113 glioma patients. In addition, CFL1 expression was positively correlated with PGK1 expression in glioma. The results suggested that as promising indicators, CFL1 and PGK1 could be used to evaluate glioma radiosensibility and prognosis. These two proteins could also be the potential therapeutic targets of glioma.

Salinomycin exhibits anti-angiogenic activity against human glioma in vitro and in vivo by suppressing the VEGF-VEGFR2-AKT/FAK signaling axis

Tumor angiogenesis plays a crucial role in tumor growth, progression and metastasis, and suppression of tumor angiogenesis has been considered as a promising anticancer strategy. Salinomycin (SAL), an antibiotic, displays novel anticancer potential against several human cancer cells in vitro and in vivo. However, little information concerning its anti-angiogenic properties is available. Therefore, the anti‑angiogenic effect of SAL and the underlying mechanism in human glioma were evaluated in the present study. The results indicated that SAL treatment significantly inhibited human umbilical vein endothelial cell (HUVEC) proliferation, migration, invasion and capillary-like tube formation. Further investigation on intracellular mechanisms showed that SAL markedly suppressed FAK and AKT phosphorylation, and downregulated vascular endothelial growth factor (VEGF) expression in HUVECs. Pretreatment of cells with a PI3K inhibitor (LY294002) and FAK inhibitor (PF562271) markedly enhanced SAL-induced inhibition of HUVEC proliferation and migration, respectively. Moreover, U251 human glioma xenograft growth was also effectively blocked by SAL treatment in vivo via inhibition of angiogenesis involving FAK and AKT depho-sphorylation. Taken together, our findings validated that SAL inhibits angiogenesis and human glioma growth through suppression of the VEGF-VEGFR2-AKT/FAK signaling axis, indicating the potential application of SAL for the treatment of human glioma.

Antitumor activity of 7-O-succinyl macrolactin A tromethamine salt in the mouse glioma model

Chemoradiotherapy with temozolomide is the current standard treatment option for patients with glioblastoma. However, the majority of patients with glioblastoma survive for <2 years. Therefore, it is necessary to develop more effective therapeutic strategies for the treatment of glioblastoma. 7-O-succinyl macrolactin A tromethamine salt (SMA salt), a macrolactin compound, is known to possess an antiangiogenic activity. The present study investigated the antitumor effects of SMA salt in the treatment of glioblastoma by evaluating in vitro and in vivo antitumor effects of SMA salt in an experimental glioblastoma model. The antitumor effects of the drug on human glioblastoma U87MG, U251MG and LN229 cell lines were assessed using in vitro cell viability, migration and invasion assays. Nude mice with established U87MG glioblastoma were assigned to either the control or SMA salt treatment group. The volume of tumors and the duration of survival were also measured. SMA salt affected cell viability and caused a concentration-dependent inhibition effect on the migration and invasion of glioblastoma cell lines. Animals in the SMA salt treatment group demonstrated a significant reduction in tumor volume and an increase in survival (P<0.05). Treatment with SMA salt presented more cytotoxic effects as well as anti-migration and anti-invasion activity compared with the control group in vitro and in vivo. These results suggest that SMA salt has significant antitumor effects on glioblastoma.

Blockade of vascular endothelial growth factor receptors by tivozanib has potential anti-tumour effects on human glioblastoma cells

Glioblastoma (GBM) remains one of the most fatal human malignancies due to its high angiogenic and infiltrative capacities. Even with optimal therapy including surgery, radiotherapy and temozolomide, it is essentially incurable. GBM is among the most neovascularised neoplasms and its malignant progression associates with striking neovascularisation, evidenced by vasoproliferation and endothelial cell hyperplasia. Targeting the pro-angiogenic pathways is therefore a promising anti-glioma strategy. Here we show that tivozanib, a pan-inhibitor of vascular endothelial growth factor (VEGF) receptors, inhibited proliferation of GBM cells through a G2/M cell cycle arrest via inhibition of polo-like kinase 1 (PLK1) signalling pathway and down-modulation of Aurora kinases A and B, cyclin B1 and CDC25C. Moreover, tivozanib decreased adhesive potential of these cells through reduction of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1). Tivozanib diminished GBM cell invasion through impairing the proteolytic cascade of cathepsin B/urokinase-type plasminogen activator (uPA)/matrix metalloproteinase-2 (MMP-2). Combination of tivozanib with EGFR small molecule inhibitor gefitinib synergistically increased sensitivity to gefitinib. Altogether, these findings suggest that VEGFR blockade by tivozanib has potential anti-glioma effects in vitro. Further in vivo studies are warranted to explore the anti-tumour activity of tivozanib in combinatorial approaches in GBM.

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

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

Tumor-targeted nanotherapeutics: overcoming treatment barriers for glioblastoma

Glioblastoma (GBM) is a highly aggressive and lethal form of primary brain cancer. Numerous barriers exist to the effective treatment of GBM including the tightly controlled interface between the bloodstream and central nervous system termed the 'neurovascular unit,' a narrow and tortuous tumor extracellular space containing a dense meshwork of proteins and glycosaminoglycans, and genomic heterogeneity and instability. A major goal of GBM therapy is achieving sustained drug delivery to glioma cells while minimizing toxicity to adjacent neurons and glia. Targeted nanotherapeutics have emerged as promising drug delivery systems with the potential to improve pharmacokinetic profiles and therapeutic efficacy. Some of the key cell surface molecules that have been identified as GBM targets include the transferrin receptor, low-density lipoprotein receptor-related protein, α_v β₃ integrin, glucose transporter(s), glial fibrillary acidic protein, connexin 43, epidermal growth factor receptor (EGFR), EGFR variant III, interleukin-13 receptor α chain variant 2, and fibroblast growth factor-inducible factor 14. However, most targeted therapeutic formulations have yet to demonstrate improved efficacy related to disease progression or survival. Potential limitations to current targeted nanotherapeutics include: (1) adhesive interactions with nontarget structures, (2) low density or prevalence of the target, (3) lack of target specificity, and (4) genetic instability resulting in alterations of either the target itself or its expression level in response to treatment. In this review, we address these potential limitations in the context of the key GBM targets with the goal of advancing the understanding and development of targeted nanotherapeutics for GBM. WIREs Nanomed Nanobiotechnol 2017, 9:e1439. doi: 10.1002/wnan.1439 For further resources related to this article, please visit the WIREs website.

Glioma FMISO PET/MR Imaging Concurrent with Antiangiogenic Therapy: Molecular Imaging as a Clinical Tool in the Burgeoning Era of Personalized Medicine

The purpose of this article is to provide a focused overview of the current use of positron emission tomography (PET) molecular imaging in the burgeoning era of personalized medicine in the treatment of patients with glioma. Specifically, we demonstrate the utility of PET imaging as a tool for personalized diagnosis and therapy by highlighting a case series of four patients with recurrent high grade glioma who underwent 18F-fluoromisonidazole (FMISO) PET/MR (magnetic resonance) imaging through the course of antiangiogenic therapy. Three distinct features were observed from this small cohort of patients. First, the presence of pseudoprogression was retrospectively associated with the absence of hypoxia. Second, a subgroup of patients with recurrent high grade glioma undergoing bevacizumab therapy demonstrated disease progression characterized by an enlarging nonenhancing mass with newly developed reduced diffusion, lack of hypoxia, and preserved cerebral blood volume. Finally, a reduction in hypoxic volume was observed concurrent with therapy in all patients with recurrent tumor, and markedly so in two patients that developed a nonenhancing reduced diffusion mass. This case series demonstrates how medical imaging has the potential to influence personalized medicine in several key aspects, especially involving molecular PET imaging for personalized diagnosis, patient specific disease prognosis, and therapeutic monitoring.

The effects of CD147 on the cell proliferation, apoptosis, invasion, and angiogenesis in glioma

To analyze the effects of extracellular matrix metalloproteinase inducer (CD147) on glioma proliferation, apoptosis, invasion, and angiogenesis. Tissue samples were obtained from 101 glioma cases while normal brain tissues were obtained from 30 brain injury cases. Immunohistochemical assay was performed to detect the expressions of CD147, CD34, and VEGF in tissue samples. QRT-PCR was performed to detect the relative expression of CD147 mRNA in human glioma cell lines. CD147 siRNA was transfected into glioma cell line U251. Cell proliferation, apoptosis, invasion, and angiogenesis were tested by MTT, flow cytometry, Transwell assay, and vasculogenic mimicry assay, respectively. Expressions of relative proteins were analyzed with western blot. CD147 was positively expressed with the percentage of 0, 37.5, 44.8, 67.9, and 85.7 % in normal tissues and glioma tissues with WHO grades I-IV, respectively, and the scores of MVDand VEGF were associated with the expression of CD147. CD147 was significantly upregulated in the human glioma cell lines (P < 0.05). Downregulated the expression of CD147 suppressed cell proliferation, blocked cell cycle, induced apoptosis, inhibited cell invasion and angiogenesis in glioma cells in vitro. The expression of CD147 was significantly associated with WHO tumor grade and angiogenesis; silencing of CD147 contributed to inhibition of glioma proliferation, invasion, and angiogenesis. Our study provided firm evidence that CD 147 is a potential glioma target for anti-angiogenic therapies.

Inhibition of Glioblastoma Cell Growth In Vitro and In Vivo by Brucine, a Component of Chinese Medicine

Glioblastoma multiforme (GBM) is one of the most common glial cell tumors and has drawn more and more attention in the clinic in recent years. Brucine has been reported to significantly suppress gastric cancer, lung cancer, and prostate cancer growth in vivo by inducing cell apoptosis. Here, the effects of brucine on U251 human glioma cell growth were investigated in vitro by cell proliferation assay, FACs, and qPCR in a xenograft tumor model. Treatment with brucine reduced the expression of BCL-2 and cyclooxygenase-2 (COX-2), while upregulated BAX expression in U251 human glioma cells resulted in reduced glioma cell survival rate and inhibited the growth of xenograft tumors. We concluded that brucine has a suppressive effect on U251 human glioma cells in vitro and in vivo, which could help in understanding the role of brucine in glioma cells and guiding drug use in the clinic.

Long non-coding RNA taurine upregulated 1 enhances tumor-induced angiogenesis through inhibiting microRNA-299 in human glioblastoma

Angiogenesis is one of the critical biological elements affecting the development and progression of cancer. Long non-coding RNAs (lncRNAs) are important regulators and aberrantly expressed in various types of human cancer. Our previous studies indicated that lncRNA taurine upregulated 1 (TUG1) implicated in the regulation of blood-tumor barrier permeability; however, its role in glioblastoma angiogenesis still unclear. Here we demonstrated that TUG1 was up-expressed in human glioblastoma tissues and glioblastoma cell lines. Knockdown of TUG1 remarkably suppressed tumor-induced endothelial cell proliferation, migration and tube formation as well as reducing spheroid-based angiogenesis ability in vitro, which are the critical steps for tumor angiogenesis. Besides, knockdown of TUG1 significantly increased the expression of mircroRNA-299 (miR-299), which was down-expressed in glioblastoma tissues and glioblastoma cell lines. Bioinformatics analysis and luciferase reporter assay revealed that TUG1 influenced tumor angiogenesis via directly binding to the miR-299 and there was a reciprocal repression between TUG1 and miR-299 in the same RNA-induced silencing complex. Moreover, knockdown of TUG1 reduced the expression of vascular endothelial growth factor A (VEGFA), which was defined as a functional downstream target of miR-299. In addition, knockdown of TUG1, shown in the in vivo studies, has effects on suppressing tumor growth, reducing tumor microvessel density and decreasing the VEGFA expression by upregulating miR-299 in xenograft glioblastoma model. Overall, the results demonstrated that TUG1 enhances tumor-induced angiogenesis and VEGF expression through inhibiting miR-299. Also, the inhibition of TUG1 could provide a novel therapeutic target for glioblastoma treatment.

Knockdown of long noncoding RNA H19 sensitizes human glioma cells to temozolomide therapy

Temozolomide (TMZ) is commonly used in glioma chemotherapy. However, a great clinical challenge for TMZ is chemoresistance. H19 transcripts are recognized as long noncoding RNAs, which potentially interact with chromatin-modifying complexes to regulate gene expression via epigenetic changes. Our data based on glioma patients showed that the expression of H19 was significantly upregulated in TMZ-resistant tumors compared with the TMZ-sensitive tumors. To determine the function of H19 in glioma, cell lines U87 and U251 were exposed to TMZ to establish TMZ-resistant clones U87(TMZ) and U251(TMZ). In U87(TMZ) and U251(TMZ), the expression level of H19 transcripts was increased compared to wild-type or nonresistant clones, as determined by real-time quantitative reverse transcription polymerase chain reaction. Concomitant treatment with small interfering RNA specifically targeting H19 and TMZ in resistant glioma clones resulted in decreased IC50 values for TMZ, and increased apoptotic rates than control small interfering RNA-treated cells. This was also evident by the increased PARP cleavage in resistant cells exposed to TMZ + si-H19. Furthermore, the reduced expression of H19 altered major drug resistance genes, such as MDR, MRP, and ABCG2, both at the mRNA and protein levels. Taken together, these findings suggest that H19 plays an important role in the development of TMZ resistance, and may represent a novel therapeutic target for TMZ-resistant gliomas.

RTVP-1 regulates glioma cell migration and invasion via interaction with N-WASP and hnRNPK

Glioblastoma (GBM) are characterized by increased invasion into the surrounding normal brain tissue. RTVP-1 is highly expressed in GBM and regulates the migration and invasion of glioma cells. To further study RTVP-1 effects we performed a pull-down assay using His-tagged RTVP-1 followed by mass spectrometry and found that RTVP-1 was associated with the actin polymerization regulator, N-WASP. This association was further validated by co-immunoprecipitation and FRET analysis. We found that RTVP-1 increased cell spreading, migration and invasion and these effects were at least partly mediated by N-WASP. Another protein which was found by the pull-down assay to interact with RTVP-1 is hnRNPK. This protein has been recently reported to associate with and to inhibit the effect of N-WASP on cell spreading. hnRNPK decreased cell migration, spreading and invasion in glioma cells. Using co-immunoprecipitation we validated the interactions of hnRNPK with N-WASP and RTVP-1 in glioma cells. In addition, we found that overexpression of RTVP-1 decreased the association of N-WASP and hnRNPK. In summary, we report that RTVP-1 regulates glioma cell spreading, migration and invasion and that these effects are mediated via interaction with N-WASP and by interfering with the inhibitory effect of hnRNPK on the function of this protein.

Silencing of Long Non-Coding RNA MALAT1 Promotes Apoptosis of Glioma Cells

The metastasis-associated lung adenocarcinoma transcription 1 (MALAT1) is a highly conserved long non-coding RNA (lncRNA) gene. However, little is known about the pathological role of lncRNA MALAT1 in glioma. In the present study, we explored the expression level of lncRNA MALAT1 in primary glioma tissues as well as in U87 and U251 glioma cell lines. Using qRT-PCR, we found that the expression of lncRNA MALAT1 was significantly increased in glioma tissues compared with that of paracancerous tissues. Meanwhile, the expression of MALAT1 was highly expressed in U98 and U251 cells. In order to explore the function of MALAT1, the expression of MALAT1 was greatly reduced in U87 and U251 cells transfected with siRNA specifically targeting MALAT1. Consequently, cell viability of U87 and U251 cells were drastically decreased after the knockdown of MALAT1. Concomitantly, the apoptosis rate of the two cell lines was dramatically increased. Furthermore, the expression levels of some tumor markers were reduced after the knockdown of MALAT1, such as CCND1 and MYC. In summary, the current study indicated a promoting role of MALAT1 in the development of glioma cell.

An Integrative Platform for Three-dimensional Quantitative Analysis of Spatially Heterogeneous Metastasis Landscapes

Metastatic microenvironments are spatially and compositionally heterogeneous. This seemingly stochastic heterogeneity provides researchers great challenges in elucidating factors that determine metastatic outgrowth. Herein, we develop and implement an integrative platform that will enable researchers to obtain novel insights from intricate metastatic landscapes. Our two-segment platform begins with whole tissue clearing, staining, and imaging to globally delineate metastatic landscape heterogeneity with spatial and molecular resolution. The second segment of our platform applies our custom-developed SMART 3D (Spatial filtering-based background removal and Multi-chAnnel forest classifiers-based 3D ReconsTruction), a multi-faceted image analysis pipeline, permitting quantitative interrogation of functional implications of heterogeneous metastatic landscape constituents, from subcellular features to multicellular structures, within our large three-dimensional (3D) image datasets. Coupling whole tissue imaging of brain metastasis animal models with SMART 3D, we demonstrate the capability of our integrative pipeline to reveal and quantify volumetric and spatial aspects of brain metastasis landscapes, including diverse tumor morphology, heterogeneous proliferative indices, metastasis-associated astrogliosis, and vasculature spatial distribution. Collectively, our study demonstrates the utility of our novel integrative platform to reveal and quantify the global spatial and volumetric characteristics of the 3D metastatic landscape with unparalleled accuracy, opening new opportunities for unbiased investigation of novel biological phenomena in situ.

Adhesion molecules and the extracellular matrix as drug targets for glioma

The formation of tumor vasculature and cell invasion along white matter tracts have pivotal roles in the development and progression of glioma. A better understanding of the mechanisms of angiogenesis and invasion in glioma will aid the development of novel therapeutic strategies. The processes of angiogenesis and invasion cause the production of an array of adhesion molecules and extracellular matrix (ECM) components. This review focuses on the role of adhesion molecules and the ECM in malignant glioma. The results of clinical trials using drugs targeted against adhesion molecules and the ECM for glioma are also discussed.

Potential Diagnostic and Prognostic Value of Plasma Circulating MicroRNA-182 in Human Glioma

Background

Previous studies showed the aberrant expression of microRNA-182 (miR-182) in glioma tissue. However, the exact role of circulating miR-182 in glioma remains unclear. Here, we confirmed the expression of plasma circulating miR-182 in glioma patients, and further explored its potential diagnostic and prognostic value.

Material/Methods

Real-time quantitative PCR (RT-PCR) was used to measure circulating cell-free miR-182 from 112 glioma patients and 54 healthy controls.

Results

Our findings showed that the level of circulating miR-182 in glioma patients was higher than that in healthy controls (P<0.001), which was significantly associated with KPS score (P=0.025) and WHO grade (P<0.001). The area under the receiver operating characteristic (ROC) curve (AUC) was 0.778. The optimal cut-off value was 1.56, and the sensitivity and specificity were 58.5% and 85.2%, respectively. Interestingly, a high predictive value of circulating miR-182 was observed in high-grade glioma (AUC=0.815). However, the AUC was lower in low-grade glioma (AUC=0.621). Kaplan-Meier analysis demonstrated that the cumulative 5-year overall survival rate in the high miR-182 group was significantly lower than that in the low miR-182 group in both overall survival (OS) (P=0.003) and disease-free survival (DFS) (P=0.006). Moreover, multivariate Cox analysis revealed that circulating miR-182 was an independent prognostic indicator for OS (P=0.034) and DFS (P=0.013).

Conclusions

These results suggest that circulating miR-182 may be a potential noninvasive biomarker for the diagnosis and prognosis of human glioma.

Increased level of H19 long noncoding RNA promotes invasion, angiogenesis, and stemness of glioblastoma cells

OBJECT

Increased levels of H19 long noncoding RNA (lncRNA) have been observed in many cancers, suggesting that overexpression of H19 may be important in the development of carcinogenesis. However, the role of H19 in human glioblastoma is still unclear. The object of this study was to examine the level of H19 in glioblastoma samples and investigate the role of H19 in glioblastoma carcinogenesis.

METHODS

Glioblastoma and nontumor brain tissue specimens were obtained from tissue obtained during tumor resection in 30 patients with glioblastoma. The level of H19 lncRNA was detected by real-time quantitative reverse transcription polymerase chain reaction. The role of H19 in invasion, angiogenesis, and stemness of glioblastoma cells was then investigated using commercially produced cell lines (U87 and U373). The effects of H19 overexpression on glioblastoma cell invasion and angiogenesis were detected by in vitro Matrigel invasion and endothelial tube formation assay. The effects of H19 on glioblastoma cell stemness and tumorigenicity were investigated by neurosphere formation and an in vivo murine xenograft model.

RESULTS

The authors found that H19 is significantly overexpressed in glioblastoma tissues, and the level of expression was associated with patient survival. In the subsequent investigations, the authors found that overexpression of H19 promotes glioblastoma cell invasion and angiogenesis in vitro. Interestingly, H19 was also significantly overexpressed in CD133+ glioblastoma cells, and overexpression of H19 was associated with increased neurosphere formation of glioblastoma cells. Finally, stable overexpression of H19 was associated with increased tumor growth in the murine xenograft model.

CONCLUSIONS

The results of this study suggest that increased expression of H19 lncRNA promotes invasion, angiogenesis, stemness, and tumorigenicity of glioblastoma cells. Taken together, these findings indicate that H19 plays an important role in tumorigenicity and stemness of glioblastoma and thus could be a therapeutic target for treatment of glioblastoma in the future.

An integrated transcriptomic and computational analysis for biomarker identification in human glioma

Malignant glioma is one of the most common primary brain tumors and is among the deadliest of human cancers. The molecular mechanism for human glioma is poorly understood. Early prognosis of this disease and early treatment are vital. Thus, it is crucial to target the key genes controlling pathogenesis in the early stage of glioma. In this study, differentially expressed genes in human glioma and paired peritumoral tissues were detected by transcriptome microarray analysis. Following gene microarray analysis, the gene expression profile in the differential grade glioma was further validated by bioinformatic analyses, co-expression network construction. Microarray analysis revealed that 1725 genes were differentially expressed and classified into different glioma stage. The analysis revealed 14 genes that were significantly associated with survival with a false discovery rate. Among these genes, macrophage capping protein (CAPG), a member of the actin-regulatory protein, was the key gene in a 20-gene network that modulates cell motility by interacting with the cytoskeleton. Furthermore, the prognostic impact of CAPG was validated by use of quantitative real-time polymerase chain reaction (qPCR) and immunohistochemistry on human glioma tissue. CAPG protein was significantly upregulated in clinical high-grade glioblastoma as compared with normal brain tissues. Overexpression of CAPG levels also predict shorter overall survival of glioma patients. These data demonstrated CAPG protein expression in human glioma was associated with tumorigenesis and may be a biomarker for identification of the pathological grade of glioma.

The challenges and the promise of molecular targeted therapy in malignant gliomas

Malignant gliomas are the most common malignant primary brain tumors and one of the most challenging forms of cancers to treat. Despite advances in conventional treatment, the outcome for patients remains almost universally fatal. This poor prognosis is due to therapeutic resistance and tumor recurrence after surgical removal. However, over the past decade, molecular targeted therapy has held the promise of transforming the care of malignant glioma patients. Significant progress in understanding the molecular pathology of gliomagenesis and maintenance of the malignant phenotypes will open opportunities to rationally develop new molecular targeted therapy options. Recently, therapeutic strategies have focused on targeting pro-growth signaling mediated by receptor tyrosine kinase/RAS/phosphatidylinositol 3-kinase pathway, proangiogenic pathways, and several other vital intracellular signaling networks, such as proteasome and histone deacetylase. However, several factors such as cross-talk between the altered pathways, intratumoral molecular heterogeneity, and therapeutic resistance of glioma stem cells (GSCs) have limited the activity of single agents. Efforts are ongoing to study in depth the complex molecular biology of glioma, develop novel regimens targeting GSCs, and identify biomarkers to stratify patients with the individualized molecular targeted therapy. Here, we review the molecular alterations relevant to the pathology of malignant glioma, review current advances in clinical targeted trials, and discuss the challenges, controversies, and future directions of molecular targeted therapy.

Novel delivery methods bypassing the blood-brain and blood-tumor barriers

Glioblastoma (GBM) is the most common primary brain tumor and carries a grave prognosis. Despite years of research investigating potentially new therapies for GBM, the median survival rate of individuals with this disease has remained fairly stagnant. Delivery of drugs to the tumor site is hampered by various barriers posed by the GBM pathological process and by the complex physiology of the blood-brain and blood-cerebrospinal fluid barriers. These anatomical and physiological barriers serve as a natural protection for the brain and preserve brain homeostasis, but they also have significantly limited the reach of intraparenchymal treatments in patients with GBM. In this article, the authors review the functional capabilities of the physical and physiological barriers that impede chemotherapy for GBM, with a specific focus on the pathological alterations of the blood-brain barrier (BBB) in this disease. They also provide an overview of current and future methods for circumventing these barriers in therapeutic interventions. Although ongoing research has yielded some potential options for future GBM therapies, delivery of chemotherapy medications across the BBB remains elusive and has limited the efficacy of these medications.

Biochanin A inhibits endothelial cell functions and proangiogenic pathways: implications in glioma therapy

Malignant gliomas, such as glioblastoma multiforme, are highly vascularized tumors of the central nervous system. A rich network of angiogenic vessels supporting glioma growth is an important therapeutic target in glioma therapy. In the past few years, small molecules have gained interest as multitargeting therapies for cancer. Biochanin A is a small, natural dietary isoflavone known for its anticancer potential. Previously, we have found that biochanin A inhibits invasion in human glioblastoma cells. In this study, we elucidated the antiangiogenic mechanisms of biochanin A using rat brain tumor (C6) and murine brain endothelial (bEnd.3) cells and an ex-vivo chick chorioallantoic membrane model. Biochanin A inhibited endothelial cell functions such as cell viability, migration, and invasion, as analyzed using MTT, scratch wound, and gelatin zymography assays. Activation of proangiogenic proteins (ERK/AKT/mTOR) was inhibited. Biochanin A also inhibited chemical hypoxia-inducible factor-1α and vascular endothelial growth factor in C6 cells. Results of chick chorioallantoic membrane assay showed that biochanin A inhibited blood vessel formation ex vivo. As these results suggest that biochanin A directly targets different facets of angiogenesis in vitro and ex vivo, this study provides a rationale for future preclinical evaluation of its efficacy against angiogenic gliomas.

The roles of CD147 in the progression of gliomas

Gliomas are characterized by their invasiveness, angiogenesis, glycolysis and poor prognosis. Determining how to inhibit angiogenesis and glycolysis and induce cell death in gliomas is essential to the development of an effective therapy. CD147, a highly glycosylated transmembrane glycoprotein with two Ig-like extracellular domains that belongs to the immunoglobulin superfamily, plays an important role in the regulation of tumor invasiveness, angiogenesis and glycolysis by inducing the secretion of matrix metalloproteinases and vascular endothelial growth factor and by interacting with monocarboxylate transporters. In this review, we first summarize the roles played by CD147 in gliomas and then propose that CD147 may be a complementary prognostic biomarker and a possible therapeutic target for glioma treatment.

NDRG1 overexpressing gliomas are characterized by reduced tumor vascularization and resistance to antiangiogenic treatment

Hypoxia-regulated molecules play an important role in vascular resistance to antiangiogenic treatment. N-myc downstream-regulated-gene 1 (NDRG1) is significantly upregulated during hypoxia in glioma. It was the aim of the present study to analyze the role of NDRG1 on glioma angiogenesis and on antiangiogenic treatment. Orthotopically implanted NDRG1 glioma showed reduced tumor growth and vessel density compared to controls. RT-PCR gene array analysis revealed a 30-fold TNFSF15 increase in NDRG1 tumors. Consequently, the supernatant from NDRG1 transfected U87MG glioma cells resulted in reduced HUVEC proliferation, migration and angiogenic response in tube formation assays in vitro. This effect was provoked by increased TNFSF15 promoter activity in NDRG1 cells. Mutations in NF-κB and AP-1 promoter response elements suppressed TNFSF15 promoter activity. Moreover, U87MG glioma NDRG1 knockdown supernatant contained multiple proangiogenic proteins and increased HUVEC spheroid sprouting. Sunitinib treatment of orhotopically implanted mice reduced tumor volume and vessel density in controls; in NDRG1 overexpressing cells no reduction of tumor volume or vessel density was observed. NDRG1 overexpression leads to reduced tumor growth and angiogenesis in experimental glioma via upregulation of TNFSF15. In NDRG1 overexpressing glioma antiangiogenic treatment does not yield a therapeutic response.

Long Non-Coding RNAs: The Key Players in Glioma Pathogenesis

Long non-coding RNAs (LncRNAs) represent a novel class of RNAs with no functional protein-coding ability, yet it has become increasingly clear that interactions between lncRNAs with other molecules are responsible for important gene regulatory functions in various contexts. Given their relatively high expressions in the brain, lncRNAs are now thought to play important roles in normal brain development as well as diverse disease processes including gliomagenesis. Intriguingly, certain lncRNAs are closely associated with the initiation, differentiation, progression, recurrence and stem-like characteristics in glioma, and may therefore be exploited for the purposes of sub-classification, diagnosis and prognosis. LncRNAs may also serve as potential therapeutic targets as well as a novel biomarkers in the treatment of glioma. In this article, the functional aspects of lncRNAs, particularly within the central nervous system (CNS), will be briefly discussed, followed by highlights of the important roles of lncRNAs in mediating critical steps during glioma development. In addition, the key lncRNA players and their possible mechanistic pathways associated with gliomagenesis will be addressed.

Fluorescence-guided resection of experimental malignant glioma using cetuximab-IRDye 800CW

The standard treatment for glioblastoma multiforme (GBM) remains maximal safe surgical resection. Here, we evaluated the ability of a systemically administered antibody-dye probe conjugate (cetuximab-IRDye 800CW) to provide sufficient fluorescent contrast for surgical resection of disease in both subcutaneous and orthotopic animal models of GBM. Multiple luciferase-positive GBM cell lines (D-54MG, U-87MG, and U-251MG; n = 5) were implanted in mouse flank and tumors were fluorescently imaged daily using a closed-field near-infrared (NIR) system after cetuximab-IRDye 800CW systemic administration. Orthotopic models were also generated (n = 5), and tumor resection was performed under white light and fluorescence guidance using an FDA-approved wide-field NIR imaging system. Residual tumor was monitored using luciferase imaging. Immunohistochemistry was performed to characterize tumor fluorescence, epidermal growth factor receptor (EGFR) expression, and vessel density. Daily imaging of tumors revealed an average tumor-to-background (TBR) of 4.5 for U-87MG, 4.1 for D-54MG, and 3.7 for U-251MG. Fluorescence intensity within the tumors peaked on day-1 after cetuximab-IRDye 800CW administration, however the TBR increased over time in two of the three cell lines. For the orthotopic model, TBR on surgery day ranged from 19 to 23 during wide-field, intraoperative imaging. Surgical resection under white light on day 3 after cetuximab-IRDye 800CW resulted in an average 41% reduction in luciferase signal while fluorescence-guided resection using wide-field NIR imaging resulted in a significantly (P = 0.001) greater reduction in luciferase signal (87%). Reduction of luciferase signal was found to correlate (R (2) = 0.99) with reduction in fluorescence intensity. Fluorescence intensity was found to correlate (P < 0.05) with EGFR expression in D-54MG and U-251MG tumor types but not U-87MG. However, tumor fluorescence was found to correlate with vessel density for the U-87MG tumors. Here we show systemic administration of cetuximab-IRDye 800CW in combination with wide-field NIR imaging provided robust and specific fluorescence contrast for successful localization of disease in subcutaneous and orthotopic animal models of GBM.

Drug delivery approaches for the treatment of glioblastoma multiforme

CONTEXT

Glioblastoma multiforme (GBM) is by far the most common and aggressive form of glial tumor. It is characterized by a highly proliferative population of cells that invade surrounding tissue and that frequently recur after surgical resection and chemotherapy. Over the last decades, a number of promising novel pharmacological approaches have been investigated, but most of them have failed clinical trials due to some side-effects such as toxicity and poor drug delivery to the brain. The major obstacle in the treatment of GBM is the presence of the blood-brain barrier (BBB). Due to their relatively high molecular weight, most therapeutic drugs fail to cross the BBB from the blood circulation.

OBJECTIVE

This paper sheds light on the characteristics of GBM and the challenges of current pharmacological treatments. A closer look is given to the role of nanotechnology in the field of drug delivery, and its application in the treatment of brain tumors such as GBM.

METHOD

For this purpose, effort was made to select the most recent studies using predefined search criteria that included at least one of the following keywords in the PubMed and Medline databases: glioblastoma, drug delivery, blood-brain barrier, nanotechnology, and nanoparticle.

CONCLUSION

Breakthrough in nanotechnology offers promising applications in cancer therapy and targeted drug delivery. However, more efforts need to be devoted to the development of novel therapeutic strategies that enable the delivery of drugs to desired areas of the brain with limited side-effects and higher therapeutic efficiency.

NF-κB inhibitor reverses temozolomide resistance in human glioma TR/U251 cells

Glioblastoma multiforme (GBM) demonstrates an unsatisfactory clinical prognosis due to the intrinsic or acquired resistance to temozolomide (TMZ) exhibited by the tumors. One possible cause of TMZ resistance in GBM is the overexpression of O⁶-methylguanine-DNA methyltransferase (MGMT), which can repair the TMZ-induced guanine damage in DNA. Additionally, excessive activated NF-κB is reported to be a component of the major inflammatory transcription pathway that is associated with TMZ resistance in GBM. However, the association between the NF-κB pathway and MGMT expression in GBM cells is unknown. Therefore, in the present study, the TMZ resistant (TR) U251 cell line (TR/U251) was successfully constructed to detect how the TR/U251 cell line and the parental U251 cell line each interact with TMZ in vitro. The TR/U251 cells were approximately five times more resistant to TMZ compared with the parental cells. Furthermore, it was found that the NF-κB inhibitor BAY 11-7082 suppressed the expression of MGMT in TR/U251 cells and enhanced TMZ-induced cytotoxicity and apoptosis, thereby indicating that the NF-κB pathway and MGMT interact to promote TMZ resistance. The inhibition of NF-κB may be a promising strategy to reverse drug resistance in TR glioma cells. The present results propose a potential mechanism for using the NF-κB inhibitor BAY 11-7082 as a potential therapy for the treatment of TR glioma. Although BAY 11-7082 is a well-known NF-κB inhibitor, the present study further investigated its underlying mechanisms through a series of new experiments.

Glioma grading by microvascular permeability parameters derived from dynamic contrast-enhanced MRI and intratumoral susceptibility signal on susceptibility weighted imaging

BACKGROUND

Dynamic contrast-enhanced MRI (DCE-MRI) estimates vascular permeability of brain tumors, and susceptibility-weighted imaging (SWI) may demonstrate tumor vascularity by intratumoral susceptibility signals (ITSS). This study assessed volume transfer constant (Ktrans) accuracy, the volume of extravascular extracellular space (EES) per unit volume of tissue (Ve) derived from DCE-MRI, and the degree of ITSS in glioma grading.

METHODS

Thirty-two patients with different glioma grades were enrolled in this retrospective study. Patients underwent DCE-MRI and non-contrast enhanced SWI by three-tesla scanning. Ktrans values, Ve, and the degree of ITSS in glioma were compared. Receiver operating characteristic (ROC) curve analysis determined diagnostic performances of Ktrans and Ve in glioma grading, and Spearman's correlation analysis determined the associations between Ktrans, Ve, ITSS, and tumor grade.

RESULTS

Ktrans and Ve values were significantly different between low grade gliomas (LGGs) and both high grade gliomas (HGGs) and grade II, III and IV gliomas (P<0.01). The degree of ITSS of LGGs was lower than HGGs (P<0.01), and the ITSS of grade II gliomas was lower than grade III or IV gliomas. Ktrans and Ve were correlated with glioma grade (P<0.01), while ITSS was moderately correlated (P<0.01). Ktrans values were moderately correlated with ITSS in the same segments (P<0.01).

CONCLUSION

Ktrans and Ve values, and ITSS helped distinguish the differences between LGGs and HGGs and between grade II, III and IV gliomas. There was a moderate correlation between Ktrans and ITSS in the same tumor segments.

Minimizing the non-specific binding of nanoparticles to the brain enables active targeting of Fn14-positive glioblastoma cells

A major limitation in the treatment of glioblastoma (GBM), the most common and deadly primary brain cancer, is delivery of therapeutics to invading tumor cells outside of the area that is safe for surgical removal. A promising way to target invading GBM cells is via drug-loaded nanoparticles that bind to fibroblast growth factor-inducible 14 (Fn14), thereby potentially improving efficacy and reducing toxicity. However, achieving broad particle distribution and nanoparticle targeting within the brain remains a significant challenge due to the adhesive extracellular matrix (ECM) and clearance mechanisms in the brain. In this work, we developed Fn14 monoclonal antibody-decorated nanoparticles that can efficiently penetrate brain tissue. We show these Fn14-targeted brain tissue penetrating nanoparticles are able to (i) selectively bind to recombinant Fn14 but not brain ECM proteins, (ii) associate with and be internalized by Fn14-positive GBM cells, and (iii) diffuse within brain tissue in a manner similar to non-targeted brain penetrating nanoparticles. In addition, when administered intracranially, Fn14-targeted nanoparticles showed improved tumor cell co-localization in mice bearing human GBM xenografts compared to non-targeted nanoparticles. Minimizing non-specific binding of targeted nanoparticles in the brain may greatly improve the access of particulate delivery systems to remote brain tumor cells and other brain targets.

Genome-wide transcriptional analyses of Chinese patients reveal cell migration is attenuated in IDH1-mutant glioblastomas

Patients with isocitrate dehydrogenase 1 (IDH1)-mutant glioblastoma exhibit increased survival compared with those with wild-type IDH1 tumors. The magnitude of this finding has led to the use of IDH1 mutations as diagnostic and prognostic biomarkers. However, the mechanisms underlying the reported correlation between the IDH1 mutation and increased survival have not been fully revealed. In this work, based on genome-wide transcriptional analyses of 69 Chinese patients with glioblastoma, we have found that the focal adhesion pathway is significantly downregulated in IDH1-mutant glioblastomas. The impaired focal adhesion leads to compromised cell migration and tumor invasion, contributing to the optimistic prognosis of these patients. Moreover, the signature genes of HIF-1α, the downstream factor of mutated IDH1, are found to be suppressed in IDH1-mutant gliomas. Given the role of HIF-1α in cell migration, we conclude that the attenuation of HIF-1α-dependent glioblastoma cell infiltration contributes to the better outcomes of patients with IDH1-mutant gliomas.

Hyperplasia of pericytes is one of the main characteristics of microvascular architecture in malignant glioma

Objectives

To investigate the role of pericytes in constructing the malformed microvessels (MVs) and participating microvascular architecture heterogeneity of glioma.

Methods

Forty human glioma tissue samples (WHO grade II-IV) were included in present study. Observation of blood vessel patterns, quantitative analysis of endothelial cells (ECs)- and pericyte-labeled MVs and comparison between malignant grades based on single- or double-immunohistochemical staining. The MV number density (MVND), microvascular pericyte number density (MPND), and microvascular pericyte area density (MPAD) were calculated. The expression of PDGFβ was also scored after immunostaining.

Results

In grade II glioma, most of tumor MVs were the thin-wall CD34⁺ vessels with near normal morphology. In addition to thin-wall CD34⁺ MVs, more thick-wall MVs were found in grade III glioma, which often showed α-SMA positive. Most of MVs in grade IV glioma were in the form of plexus, curled cell cords and glomeruloid microvascular proliferation while the α-SMA⁺ cells were the main components. The MVs usually showed disordered arrangement, loose connection and active cell proliferation as shown by Ki67 and α-SMA coexpression. With the increase of glioma grades, the α-SMA⁺ MVND, CD34⁺ MVND and MPND were significantly augmented although the increase of CD34⁺ MVND but not MPAD was statistically insignificant between grade III and IV. It was interesting that some vessel-like structures only consist of α-SMA⁺ cells, assuming the guiding role of pericytes in angiogenesis. The expression level of PDGFβ was upregulated and directly correlated with the MPND in different glioma grades.

Conclusion

Hyperplasia of pericytes was one of the significant characteristics of malignant glioma and locally proliferated pericytes were the main constituent of MVs in high grade glioma. The pathological characteristics of pericytes could be used as indexes of malignant grades of glioma.

Asiatic acid induces endoplasmic reticulum stress and apoptotic death in glioblastoma multiforme cells both in vitro and in vivo

Glioblastoma multiforme (GBM) is an untreatable malignancy. Existing therapeutic options are insufficient, and adversely affect functional and non-cancerous cells in the brain impairing different functions of the body. Therefore, there is an urgent need for additional preventive and therapeutic non-toxic drugs against GBM. Asiatic acid (AsA; 2,3,23-trihydroxy-12-ursen-28-oic acid, C30 H48 O5 ) is a natural small molecule widely used to treat various neurological disorders, and the present research investigates AsA's efficacy against GBM both in vitro and in vivo. Results showed that AsA treatment (10-100 µM) decreased the human GBM cell (LN18, U87MG, and U118MG) viability, with better efficacy than temozolomide at equimolar doses. Orally administered AsA (30 mg/kg/d) strongly decreased tumor volume in mice when administered immediately after ectopic U87MG xenograft implantation (54% decrease, P ≤ 0.05) or in mice with established xenografts (48% decrease, P ≤ 0.05) without any apparent toxicity. Importantly, AsA feeding (30 mg/kg/twice a day) also decreased the orthotopic U87MG xenografts growth in nude mice as measured by magnetic resonance imaging. Using LC/MS-MS methods, AsA was detected in mice plasma and brain tissue, confirming that AsA crosses blood-brain barrier. Mechanistic studies showed that AsA induces apoptotic death by modulating the protein expression of several apoptosis regulators (caspases, Bcl2 family members, and survivin) in GBM cells. Furthermore, AsA induced ER stress (increased GRP78 and Calpain, and decreased Calnexin and IRE1α expression), enhanced free intra-cellular calcium, and damaged cellular organization in GBM cells. These experimental results demonstrate that AsA is effective against GBM, and advocate further pre-clinical and clinical evaluations of AsA against GBM.

Direct effect of bevacizumab on glioblastoma cell lines in vitro

Bevacizumab is a humanized monoclonal antibody directed against the pro-angiogenic factor vascular and endothelial growth factor-A (VEGF-A) used in the treatment of glioblastomas. Although most patients respond initially to this treatment, studies have shown that glioblastomas eventually recur. Several non-mutually exclusive theories based on the anti-angiogenic effect of bevacizumab have been proposed to explain these mechanisms of resistance. In this report, we studied whether bevacizumab can act directly on malignant glioblastoma cells. We observe changes in the expression profiles of components of the VEGF/VEGF-R pathway and in the response to a VEGF-A stimulus following bevacizumab treatment. In addition, we show that bevacizumab itself acts on glioblastoma cells by activating the Akt and Erks survival signaling pathways. Bevacizumab also enhances proliferation and invasiveness of glioblastoma cells in hyaluronic acid hydrogel. We propose that the paradoxical effect of bevacizumab on glioblastoma cells could be due to changes in the VEGF-A-dependent autocrine loop as well as in the intracellular survival pathways, leading to the enhancement of tumor aggressiveness. Investigation of how bevacizumab interacts with glioblastoma cells and the resulting downstream signaling pathways will help targeting populations of resistant glioblastoma cells.

An in vitro retinoblastoma human triple culture model of angiogenesis: a modulatory effect of TGF-β

Retinoblastoma is the most common intraocular tumour in children. In view of understanding the molecular mechanisms through which angiogenic switch on happens in the early phases of reciprocal interaction between tumour and cells constituting retinal microvessel, Transwell co-cultures constituted by human retinal endothelial cells (HREC), pericytes (HRPC), and human retinoblastoma cell line Y-79 were performed. Y-79 enhanced HREC proliferation, reduced by the introduction of HRPC in triple culture. In HREC/HRPC cultures, TGF-β in media increased, decreasing in triple cultures. High VEGF levels in triple cultures witnessed the establishment of a strongly in vitro angiogenic environment. Y-79 induced in HREC an increase in c- and iPLA2, phospho-cPLA2, inducible COX-2 protein expressions, PLA2 activities and prostaglandin E2 (PGE2) release. These effects were attenuated when HRPC were introduced in triple culture. Moreover, antibody silencing of TGF-β demonstrated a strong correlation between the signalling pathway triggered by TGF-β of pericytal origin and the phospholipase activation and the modulation of PGE2 release. Inhibiting VEGFA effect, the HRPC loss in triple culture decreased, showing its modulatory effect on their survival. Relying on the data here presented, sustaining the pericytal survival in a tumour retinal environment could ensure the integrity of microvessels and the TGF-β supply, essential for controlling aberrant endothelial pruning and angiogenesis.

Induction of proline-rich tyrosine kinase 2 activation-mediated C6 glioma cell invasion after anti-vascular endothelial growth factor therapy

Background

Anti-angiogenic therapy inhibits tumor growth and is considered as a potential clinical therapy for malignant glioma. However, inevitable recurrences and unexpected tumor resistance, particularly increased invasion ability of glioma cell, were observed after anti-angiogenic treatment. The underlying mechanism remains undetermined. Focal adhesion kinase (FAK) and proline-rich tyrosine kinase 2 (Pyk2) are closely associated with cell migration; therefore, we investigated the possible role of these kinases in rat C6 glioma cell invasion induced by bevacizumab, a recombinant monoclonal antibody against vascular endothelial growth factor (VEGF).

Methods

The effects of bevacizumab on migration and invasion of C6 glioma cells were investigated in vitro and in vivo. The cells proliferation, migration, and invasion were determined by MTT assay, wound healing, and transwell assay, respectively. Invasive potential of glioma cells in vivo was assessed by counting vimentin-positive cells crossing the solid tumor rim by immunohistochemical staining. The total and phosphorylated protein levels of FAK and Pyk2 were detected by Western blotting.

Results

Bevacizumab exposure increased migration and invasion of cultured C6 cells in a concentration-dependent manner. In addition, the continuous bevacizumab treatment also promoted tumor invasion in rat C6 intracranial glioma models. Bevacizumab treatment enhanced Pyk2 phosphorylation at Tyr402, but no effect on FAK phosphorylation at Tyr397 both in vitro and in vivo. Knockdown of Pyk2 by siRNA or inhibition of Pyk2 phosphorylation by Src kinase specific inhibitor PP1 partially inhibited bevacizumab-induced cell invasion in cultured C6 glioma cells. Furthermore, the combined administration of bevacizumab and PP1 significantly suppressed glioma cell invasion into surrounding brain tissues compared to bevacizumab treatment alone in experimental rats.

Conclusions

These results suggest that anti-VEGF treatment promotes glioma cell invasion via activation of Pyk2. Inhibition of Pyk2 phosphorylation might be a potential target to ameliorate the therapeutic efficiency of anti-VEGF treatment.

Differential expression of miR200a-3p and miR21 in grade II-III and grade IV gliomas: evidence that miR200a-3p is regulated by O⁶-methylguanine methyltransferase and promotes temozolomide responsiveness

Glioblastoma multiforme (GBM) is the most common primary brain tumor and is among the deadliest of human cancers. Dysregulation of microRNAs (miRNAs) expression is an important step in tumor progression as miRNAs can act as tumor suppressors or oncogenes and may affect cell sensitivity to chemotherapy. Whereas the oncogenic miR21 has been shown to be overexpressed in gliomas, the expression and function of the tumor-supressor miR200a in GBMs remains unknown. In this study, we show that miR21 is upregulated in grade IV (GBMs) vs. grade II-III (LGs) gliomas, confirming that miR21 expression level is correlated with tumor grade, and that it may be considered as a marker of tumor progression. Conversely, miR200a is demonstrated for the first time to be downregulated in GBMs compared with LGs, and overexpression of miR200a in GBM cells is shown to promote TMZ-sensitivity. Interestingly, miR200a but not miR21 expression level is significantly higher in TMZ-responsive vs. -unresponsive tumoral glial cells in primary culture. Furthermore, miR200a appears negatively correlated with the expression of the DNA repair enzyme O (6)-methylguanine methyltransferase (MGMT), and the inhibition of MGMT activity results in an increase of miR200a expression in GBM cells. Taken together, these data strongly suggest that miR200a is likely to act as a crucial antitumoral factor regarding glioma progression. Interplay between miR200a and MGMT should be considered as potential mechanism involved in therapeutic response.

Glioma: Application of histogram analysis of pharmacokinetic parameters from T1-weighted dynamic contrast-enhanced MR imaging to tumor grading

BACKGROUND AND PURPOSE

The usefulness of pharmacokinetic parameters for glioma grading has been reported based on the perfusion data from parts of entire-tumor volumes. However, the perfusion values may not reflect the entire-tumor characteristics. Our aim was to investigate the feasibility of glioma grading by using histogram analyses of pharmacokinetic parameters including the volume transfer constant, extravascular extracellular space volume per unit volume of tissue, and blood plasma volume per unit volume of tissue from T1-weighted dynamic contrast-enhanced perfusion MR imaging.

MATERIALS AND METHODS

Twenty-eight patients (14 men, 14 women; mean age, 49.75 years; age range, 25-72 years) with histopathologically confirmed gliomas (World Health Organization grade II, n = 7; grade III, n = 8; grade IV, n = 13) were examined before surgery or biopsy with conventional MR imaging and T1-weighted dynamic contrast-enhanced perfusion MR imaging at 3T. Volume transfer constant, extravascular extracellular space volume per unit volume of tissue, and blood plasma volume per unit volume of tissue were calculated from the entire-tumor volume. Histogram analyses from these parameters were correlated with glioma grades. The parameters with the best percentile from cumulative histograms were identified by analysis of the area under the curve of the receiver operating characteristic analysis and were compared by using multivariable stepwise logistic regression analysis for distinguishing high- from low-grade gliomas.

RESULTS

All parametric values increased with increasing glioma grade. There were significant differences among the 3 grades in all parameters (P < .01). For the differentiation of high- and low-grade gliomas, the highest area under the curve values were found at the 98th percentile of the volume transfer constant (area under the curve, 0.912; cutoff value, 0.277), the 90th percentile of extravascular extracellular space volume per unit volume of tissue (area under the curve, 0.939; cutoff value, 19.70), and the 84th percentile of blood plasma volume per unit volume of tissue (area under the curve, 0.769; cutoff value, 11.71). The 98th percentile volume transfer constant value was the only variable that could be used to independently differentiate high- and low-grade gliomas in multivariable stepwise logistic regression analysis.

CONCLUSIONS

Histogram analysis of pharmacokinetic parameters from whole-tumor volume data can be a useful method for glioma grading. The 98th percentile value of the volume transfer constant was the most significant measure.

Impact of perfusion map analysis on early survival prediction accuracy in glioma patients

Studies investigating dynamic susceptibility contrast magnetic resonance imaging-determined relative cerebral blood volume (rCBV) maps as a metric of treatment response assessment have generated conflicting results. We evaluated the potential of various analytical techniques to predict survival of patients with glioma treated with chemoradiation. rCBV maps were acquired in patients with high-grade gliomas at 0, 1, and 3 weeks into chemoradiation therapy. Various analytical techniques were applied to the same cohort of serial rCBV data for early assessment of survival. Three different methodologies were investigated: 1) percentage change of whole tumor statistics (i.e., mean, median, and percentiles), 2) physiological segmentation (low rCBV, medium rCBV, or high rCBV), and 3) a voxel-based approach, parametric response mapping (PRM). All analyses were performed using the same tumor contours, which were determined using contrast-enhanced T1-weighted and fluid attenuated inversion recovery images. The predictive potential of each response metric was assessed at 1-year and overall survival. PRM was the only analytical approach found to generate a response metric significantly predictive of patient 1-year survival. Time of acquisition and contour volume were not found to alter the sensitivity of the PRM approach for predicting overall survival. We have demonstrated the importance of the analytical approach in early response assessment using serial rCBV maps. The PRM analysis shows promise as a unified early and robust imaging biomarker of treatment response in patients diagnosed with high-grade gliomas.

Phosphoglycerate kinase 1 promotes radioresistance in U251 human glioma cells

Phosphoglycerate kinase 1 (PGK1) has been found to be increased in radioresistant astrocytomas. The present study was designed to investigate the potential role of PGK1 in the radioresistance in U251 human cells. Quantitative PCR and western blot analysis were performed to evaluate PGK1 expression for mRNA levels and protein levels, respectively. The short hairpin RNA (shRNA)-PGK1 and the high expression plasmids were transfected to radioresistant U251 cells (RR-U251 cells) or normal U251 cells using lipofectamine™ 2000. The cell viability was determined by MTT assay. The wound-healing assay (WHA) was used to evaluate cell migration ability. Cell invasion abilities were examined using a Transwell culture chamber system. Our results showed that the expression of PGK1 was significantly increased in RR-U251 cells compared to normal U251 cells. Following irradiation, the cell viability as well as the migration and invasion ability were significantly higher in RR-U251 cells compared with normal U251 cells. Downregulating PGK1 using shRNA induced a significantly downregulated cell viability and decreased migration and invasion ability, and overexpression of PGK1 contributed to upregulated cell viability and increased migration and invasion ability, both in RR-U251 cells and normal U251 cells. These findings suggest that PGK1 could promote radioresistance in U251 human cells.

Systematic review of protein biomarkers of invasive behavior in glioblastoma

Glioblastoma (GBM) is an aggressive and incurable brain tumor with a grave prognosis. Recurrence is inevitable even with maximal surgical resection, in large part because GBM is a highly invasive tumor. Invasiveness also contributes to the failure of multiple cornerstones of GBM therapy, including radiotherapy, temozolomide chemotherapy, and vascular endothelial growth factor blockade. In recent years there has been significant progress in the identification of protein biomarkers of invasive phenotype in GBM. In this article, we comprehensively review the literature and survey a broad spectrum of biomarkers, including proteolytic enzymes, extracellular matrix proteins, cell adhesion molecules, neurodevelopmental factors, cell signaling and transcription factors, angiogenic effectors, metabolic proteins, membrane channels, and cytokines and chemokines. In light of the marked variation seen in outcomes in GBM patients, the systematic use of these biomarkers could be used to form a framework for better prediction, prognostication, and treatment selection, as well as the identification of molecular targets for further laboratory investigation and development of nascent, directed therapies.

The brain tumor microenvironment

High-grade brain tumors are heterogeneous with respect to the composition of bona fide tumor cells and with respect to a range of intermingling parenchymal cells. Glioblastomas harbor multiple cell types, some with increased tumorigenicity and stem cell-like capacity. The stem-like cells maybe the cells of origin for tumor relapse. However, the tumor-associated parenchymal cells such as vascular cells,microglia, peripheral immune cells, and neural precursor cells also play a vital role in controlling the course of pathology.In this review, we describe the multiple interactions of bulk glioma cells and glioma stem cells with parenchymal cell populations and highlight the pathological impact as well as signaling pathways known for these types of cell-cell communication. The tumor-vasculature not only nourishes glioblastomas, but also provides a specialized niche for these stem-like cells. In addition, microglial cells,which can contribute up to 30% of a brain tumor mass,play a role in glioblastoma cell invasion. Moreover, non-neoplastic astrocytes can be converted into a reactive phenotype by the glioma microenvironment and can then secrete a number of factors which influences tumor biology. The young brain may have the capacity to inhibit gliomagenesis by the endogenous neural precursor cells, which secrete tumor suppressive factors. The factors, pathways, and interactions described in this review provide a new prospective on the cell biology of primary brain tumors, which may ultimately generate new treatment modalities. However, our picture of the multiple interactions between parenchymal and tumor cells is still incomplete.

The brain tumor microenvironment

High-grade brain tumors are heterogeneous with respect to the composition of bona fide tumor cells and with respect to a range of intermingling parenchymal cells. Glioblastomas harbor multiple cell types, some with increased tumorigenicity and stem cell-like capacity. The stem-like cells maybe the cells of origin for tumor relapse. However, the tumor-associated parenchymal cells such as vascular cells,microglia, peripheral immune cells, and neural precursor cells also play a vital role in controlling the course of pathology.In this review, we describe the multiple interactions of bulk glioma cells and glioma stem cells with parenchymal cell populations and highlight the pathological impact as well as signaling pathways known for these types of cell-cell communication. The tumor-vasculature not only nourishes glioblastomas, but also provides a specialized niche for these stem-like cells. In addition, microglial cells,which can contribute up to 30% of a brain tumor mass,play a role in glioblastoma cell invasion. Moreover, non-neoplastic astrocytes can be converted into a reactive phenotype by the glioma microenvironment and can then secrete a number of factors which influences tumor biology. The young brain may have the capacity to inhibit gliomagenesis by the endogenous neural precursor cells, which secrete tumor suppressive factors. The factors, pathways, and interactions described in this review provide a new prospective on the cell biology of primary brain tumors, which may ultimately generate new treatment modalities. However, our picture of the multiple interactions between parenchymal and tumor cells is still incomplete.

Mechanisms of tumor development and anti-angiogenic therapy in glioblastoma multiforme

Despite advances in surgical and medical therapy, glioblastoma multiforme (GBM) remains a fatal disease. There has been no significant increase in survival for patients with this disease over the last 20 years. Tumor vasculature formation and glioma cell invasion along the white matter tracts both play a pivotal role in glioma development. Angiogenesis and invasion are the major factors believed to be responsible for treatment resistance in tumors, and a better understanding of the glioma invasion and angiogenesis mechanisms will lead to the development of potential new treatments. In this review, we focus on the molecular characteristics of angiogenesis and invasion in human malignant glioma. We discuss bevacizumab and cilengitide, which are used to inhibit angiogenesis in GBM.