Human Glioblastoma Multiforme Tumors Research Articles

Abstract 387: Ionizing radiation induces lipid metabolism-associated vulnerabilities in glioblastoma multiforme

Abstract Introduction: Glioblastoma multiforme (GBM) is the most common primary malignant brain tumor in adults. It is highly resistant to its current standard-of-care regimen, which includes surgical resection followed by adjuvant ionizing radiation and temozolomide. Therapy resistance can be attributed to the abundance of genomic alterations in GBM tumors that evolve over time, which contribute to intra-and inter-tumoral heterogeneities that render targeted therapies as inadequate treatment options. Thus, there is an urgent unmet need for effective therapies targeting primary and recurrent GBM. Here, we investigated the impact of ionizing radiation on the transcriptome of patient derived GBM tumor spheres to identify key alterations and biological pathways involved in therapy resistance. Materials and methods: We acquired four independent human GBM tumor sphere cell lines, which were derived from patients and cultured in serum-free media. Tumor spheres were treated with either a sham radiation or a single dose of 10Gy. Using poly-A enrichment whole transcriptome sequencing, we evaluated transcriptional alterations occurring in GBM tumors spheres at 96h post-radiation. To do so, we performed differential expression analysis and gene set enrichment analysis (GSEA) to identify top differentially expressed genes and significant changes in biological phenomena. Additionally, we evaluated the cell viability response of these GBM tumor spheres to radiation. Results and discussion: PCA analysis of the four human GBM tumor sphere cell lines demonstrates that cell type has a substantial impact on variation among samples compared to non-irradiated and irradiated treatment conditions. Upon analysis of genes in common that are either upregulated or downregulated followed by GSEA, we identified enrichment of genes associated with inflammatory responses and ferroptosis repression (e.g., NUPR1, PTGS1, AOX1), and depletion of genes involved in fatty acid metabolism (e.g., INSIG1, PLA2G3, ACAT2). Furthermore, the GBM tumor sphere cell viability responses allowed us to stratify our models into radiosensitive and radioresistant subgroups. Conclusion: Radiosensitive human GBM tumor spheres exhibit transcriptional alterations in genes linked to inflammation and fatty acid metabolism to a greater extent compared to radioresistant tumor spheres. Our study characterizes the radiation response of patient derived GBM models, which is to be leveraged for combating therapeutic resistance. Citation Format: Arianna Richelle Izawa-Ishiguro, Subhiksha Nandakumar, Nicholas Carbone, Annalisa V. Ferrotta, Raashed Raziuddin, Kristen C. Vogt, Daniel A. Heller, Ingo K. Mellinghoff. Ionizing radiation induces lipid metabolism-associated vulnerabilities in glioblastoma multiforme [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 387.

Distinct Cholesterol Localization in Glioblastoma Multiforme Revealed by Mass Spectrometry Imaging.

Glioblastoma multiforme (GBM) is the most common and aggressive brain tumor in adults and is highly resistant to chemo- and radiotherapies. GBM has been associated with alterations in lipid contents, but lipid metabolism reprogramming in tumor cells is not fully elucidated. One of the key hurdles is to localize the lipid species that are correlated with tumor growth and invasion. A better understanding of the localization of abnormal lipid metabolism and its vulnerabilities may open up to novel therapeutic approaches. Here, we use time-of-flight secondary ion mass spectrometry (ToF-SIMS) to spatially probe the lipid composition in a GBM biopsy from two regions with different histopathologies: one region with most cells of uniform size and shape, the homogeneous part, and the other with cells showing a great variation in size and shape, the heterogeneous part. Our results reveal elevated levels of cholesterol, diacylglycerols, and some phosphatidylethanolamine in the homogeneous part, while the heterogeneous part was dominated by a variety of fatty acids, phosphatidylcholine, and phosphatidylinositol species. We also observed a high expression of cholesterol in the homogeneous tumor region to be associated with large cells but not with macrophages. Our findings suggest that ToF-SIMS can distinguish in lipid distribution between parts within a human GBM tumor, which can be linked to different molecular mechanisms.

Treatment of Orthotopic U251 Human Glioblastoma Multiforme Tumors in NRG Mice by Convection-Enhanced Delivery of Gold Nanoparticles Labeled with the β-Particle-Emitting Radionuclide, 177Lu.

In this study, we investigated convection-enhanced delivery (CED) of 23 ± 3 nm gold nanoparticles (AuNPs) labeled with the β-particle-emitting radionuclide 177Lu (177Lu-AuNPs) for treatment of orthotopic U251-Luc human glioblastoma multiforme (GBM) tumors in NRG mice. The cytotoxicity in vitro of 177Lu-AuNPs (0.0-2.0 MBq, 4 × 1011 AuNPs) on U251-Luc cells was also studied by a clonogenic survival assay, and DNA double-strand breaks (DSBs) caused by β-particle emissions of 177Lu were measured by confocal immunofluorescence microscopy for γH2AX. NRG mice with U251-Luc tumors in the right cerebral hemisphere of the brain were treated by CED of 1.1 ± 0.2 MBq of 177Lu-AuNPs (4 × 1011 AuNPs). Control mice received unlabeled AuNPs or normal saline. Tumor retention of 177Lu-AuNPs was assessed by single-photon emission computed tomography/computed tomography (SPECT/CT) imaging and biodistribution studies. Radiation doses were estimated for the tumor, brain, and other organs. The effectiveness for treating GBM tumors was determined by bioluminescence imaging (BLI) and T2-weighted magnetic resonance imaging (MRI) and by Kaplan-Meier median survival. Normal tissue toxicity was assessed by monitoring body weight and hematology and blood biochemistry analyses at 14 d post-treatment. 177Lu-AuNPs (2.0 MBq, 4 × 1011 AuNPs) decreased the clonogenic survival of U251-Luc cells to 0.005 ± 0.002 and increased DNA DSBs by 14.3-fold compared to cells treated with unlabeled AuNPs or normal saline. A high proportion of 177Lu-AuNPs was retained in the U251-Luc tumor in NRG mice up to 21 d with minimal re-distribution to the brain or other organs. The radiation dose in the tumor was high (599 Gy). The dose in the normal right cerebral hemisphere of the brain excluding the tumor was 93-fold lower (6.4 Gy), and 2000-3000-fold lower doses were calculated for the contralateral left cerebral hemisphere (0.3 Gy) or cerebellum (0.2 Gy). The doses in peripheral organs were <0.1 Gy. BLI revealed almost complete tumor growth arrest in mice treated with 177Lu-AuNPs, while tumors grew rapidly in control mice. MRI at 28 d post-treatment and histological staining showed no visible tumor in mice treated with 177Lu-AuNPs but large GBM tumors in control mice. All control mice reached a humane endpoint requiring sacrifice within 39 d (normal saline) or 45 d post-treatment (unlabeled AuNPs), while 5/8 mice treated with 177Lu-AuNPs survived up to 150 d. No normal tissue toxicity was observed in mice treated with 177Lu-AuNPs. We conclude that CED of 177Lu-AuNPs was highly effective for treating U251-Luc human GBM tumors in the brain in NRG mice at amounts that were non-toxic to normal tissues. These 177Lu-AuNPs administered by CED hold promise for treating patients with GBM to prevent recurrence and improve long-term outcome.

The Regression of Glioblastoma Multiforme is Time Dependent in the Wild-type Rat Xenograft Model.

Glioblastoma multiforme (GBM) is an aggressive case of primary brain cancer which remains among the most fatal tumors worldwide. Although, some in vitro and in vivo models have been developed for a better understanding of GBM behavior; a natural model of GBM would improve the efficiency of experimental models of human GBM tumors. We aimed the present study to examine the survival and durability of U87 cells in the brain of wild-type rats. U87 cells were intracranially implanted in twenty-one wild-type rats. Tumor size and morphology as well as infiltration of immune cells were investigated at three-time points by H&E and immunohistochemistry (IHC). The results demonstrated that the inoculation of GBM cells led to the infiltration of host defense system cells which caused immunological regression of the tumor mass after six weeks. While the tumors successfully developed without any sign of host defense invasion in the second week of GBM inoculation. Also, a decrease in tumor size and infiltration of immune system cells were observed in the fourth week. These data remarkably suggest that time plays a crucial role in activating the immune system against human GBM tumors in rats; it shows that the regression of tumor mass depends on a time slope. A noticeable proliferation of tumor cells was observed in the rat's brain by the second week.The distant metastatic masses of cancer infiltrated into the adjacent normal tissue by the second week.Tumor mass underwent a noticeable diminution in the size by the fourth week.Cancer cells completely regressed by the sixth week due to immunological reactions.In tumor rejection, the effective mechanism depends on immune system activity and the slope of time. One of the most malignant tumors is the brain tumor in the world. Unfortunately, no effective treatment has yet been found for it. Of course, researchers need efficient animal models to find the appropriate treatment. The xenograft model is one of the tumor models in the laboratory. However, the main challenge is the interaction of the animal's immune system with induced-cancer cells so that the immune system finally rejects the tumor. In this study, we investigated how long the immune system needs to reject induced tumors in the xenograft model completely. For this purpose, we studied the animals in three periods (second week, fourth week, and sixth week). We concluded that the immune system does not recognize the induced cancer cells until the second week of the experiment. It results in the growth of cancer cells and the formation of tumors in the animal brain. However, the immune system begins to recognize the tumor mass after the fourth week which leads to a reduction in metastasis and tumor size. Eventually, the immune system completely rejects the formed tumor in the sixth week.

CircRNA derived from CLSPN (circCLSPN) is an oncogene in human glioblastoma multiforme by regulating cell growth, migration and invasion via ceRNA pathway

Glioblastoma multiforme (GBM) is the most aggressive and prevalent brain tumor in adults. The circRNA derived from CLSPN (hsa_circ_0011591, circCLSPN) is remarkably upregulated in GBM; however its functional role was uncovered yet. First, we examined expression of circCLSPN using GSE109569 database and RT-qPCR, and circCLSPN level was upregulated in human GBM tumor tissues and cells (A172 and LN18); moreover, circCLSPN showed a stable structure stability. Then, a series of loss-of-functional experiments were performed using CCK-8 assay, colony formation assay, flow cytometry, scratch wound assay, and transwell assay. Consequently, circCLSPN silencing suppressed cell viability, colony formation ability, cell cycle progression, migration, and invasion of A172 and LN18 cells in vitro, and promoted apoptosis rate. Allied with those were decreased B cell lymphoma-2 (Bcl-2), matrix metalloproteinase-2 (MMP2) and MMP9 expression, and elevated Bcl-2-associated X protein (Bax) level. According to dual-luciferase reporter assay and RNA pull-down assay, miR-370-3p was identified to be targeted and sponged by circCLSPN, and further targeted and negatively regulated USP39. Functionally, overexpressing miR-370-3p could mimic in vitro effects of circCLSPN interference. Rescue experiments revealed that blocking miR-370-3p could partially reverse the suppression of circCLSPN knockdown on cell growth, migration and invasion, and role of miR- 370-3p overexpression was abrogated by restoring USP39. In vivo, circCLSPN knockdown hindered tumor growth of LN18 cells by affecting miR-370-3p, USP39, MMP2 and MMP9 expression. In conclusion, circCLSPN elicited an oncogenic role in tumorigenesis and malignant progression of human GBM cells through circCLSPN-miR-370-3p-USP39 pathway.

Abstract 89: Development and characterization of a panel of orthotopic glioblastoma multiforme (GBM) patient-derived xenograft (PDX) mouse models for drug efficacy evaluation

Abstract Background Glioblastoma multiforme (GBM) is an aggressive cancer type with poor prognosis and survival. The lack of effective treatment may be due to the complex molecular composition and the heterogeneity of the tumors. Subcutaneous patient derived xenograft (PDX) mouse models are widely used in drug development. However, the models fail at modeling the complex microenvironment in the brain and the impact of the blood brain barrier on drug bioavailability. Here we report the development and characterization a panel of orthotopic PDX mouse models. Methods Low passage subcutaneous tumors from ten different PDX GBM models (ST108, ST112, ST146, ST545, ST610, ST1388, ST2473, ST3537, ST3713, and ST3720) were implanted orthotopically. Tumor development and growth was monitored by T2-weighted magnetic resonance imaging (MRI). Mice were treated with either temozolomide or vehicle when tumor take was confirmed on an individual basis by MRI. Tumor treatment response was evaluated by MRI, and the final end-point was survival by humane endpoints. Whole brains and tumors were formalin fixed or snap frozen for histological evaluation of markers of invasiveness and cancer stem cells (Nestin, CD44, SOX2, and CXCR4). In addition, the radiosensitivity of the models was characterized by fractionated external radiation therapy (XRT) delivered as 2 Gy QD x5 or sham in the subcutaneous setting. Expression of EGFR, EGFRvIII, MGMT and mGluR3 were evaluated by qPCR. Results The models displayed a wide range in expression levels of EGFR, EGFRvIII, MGMT and mGluR3. Mice treated with XRT showed a variable treatment outcome on both tumor volume and survival. The impact of XRT on prolongation of median survival ranged from 45% to 141%. In the orthotopic setting a variable range of sensitivities was observed in the models ranging from sensitive (ST610 and ST2473) to highly resistant (ST112). Histologic evaluation showed typical characteristics of GBM tumors such as pseudopalisading cells. Furthermore, cell populations positive for cancer stem cell and invasiveness markers were detected by immunofluorescence imaging. Conclusion A panel of GBM PDX models was characterized for several molecular markers and the panel reflected the heterogeneity of human GBM tumors. The models displayed varying sensitivity towards XRT and TMZ. The established panel of orthotopic GBM PDX models can be used as a platform for testing of new drugs in a setting that more closely mimics the GBM tumor microenvironment and impact of the blood brain barrier. Citation Format: Carsten H. Nielsen, Maria Z. Alfsen, Michael J. Wick, Melissa Rundle, Johann M. Gudbergsson, Mette M. Jensen, Lotte K. Kristensen, Mark U. Juul, Kyriakos P. Papadopoulos, Andreas Kjaer. Development and characterization of a panel of orthotopic glioblastoma multiforme (GBM) patient-derived xenograft (PDX) mouse models for drug efficacy evaluation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 89.

Apoptosis Induced by Viola odorata Extract in Human Glioblastoma Multiforme

: Plant extracts contain useful components that could be considered in pharmacotherapy. Due to containing anticancer components such as phenol, cyclotide, and anthocyanins, Viola odorata (sweet violet) is one of the most important components used in cancer therapy. The current study aimed at examining antitumor activity and related mechanisms to V. odorata on primary culture of human glioblastoma multiforme (GBM). It was observed that survival rate of the obtained astrocytes from human GBM tumor decreased with V. odorata hydroalcoholic extract (10 - 500 µg/mL) in a dose- and time-dependent manner and DNA fragmentation happened in concentrations above 100 µg/mL of this extract. Further observations revealed that induced apoptosis activates mitochondrial death pathway, release cytochorome C, and activates caspase-3. The current study findings revealed the effect mechanism of V. odorata extract and suggested its potential application in cancer therapy.

Abstract 2161: Characterization of a panel of orthotopic glioblastoma multiforme (GBM) patient-derived xenograft (PDX) mouse models and efficacy evaluation of temozolomide and external radiation therapy

Abstract Background Glioblastoma multiforme (GBM) is an aggressive cancer type with poor prognosis. The lack of effective treatment may be due to the complex molecular composition and the heterogeneity of the tumors. Standard of care treatment is surgery, external radiation therapy (XRT) and chemotherapy with temozolomide (TMZ); however, the response rate varies widely. Subcutaneous patient-derived xenograft (PDX) models are increasingly used during drug development. Implantation of GBM PDX tumors orthotopically in the brain displays an advantage as the tumors develop in a microenvironment that resembles that of the original patient tumor. In addition, the impact of the blood brain barrier (BBB) in terms of reduced drug bioavailability is also represented in the orthotopic GBM models. The aim of this study was to develop and characterize a panel of orthotopic GBM PDX models. The models were then used to study the efficacy of TMZ and XRT. Methods A panel of 14 PDX GBM models was characterized for EGFR, EGFRvIII, MGMT and mGluR3 expression. Selected PDX GBM models were furthermore characterized for GBM stem cell markers by flow cytometry. Low passage subcutaneous tumors from seven PDX GBM models (ST108, ST112, ST146, ST545, ST610, ST1388 and ST2473) were used for assessment of XRT sensitivity. Mice were randomized to receive XRT (2 Gy/day for 5 days) or sham. Furthermore, subcutaneous tumors were enzymatically digested and used for intracranial stereotactic injection in nude mice. Tumor take and growth rate was determined by T2-weighted magnetic resonance imaging (MRI) and 18F-fluoro-ethyl-L-tyrosine (18F-FET) PET imaging. At confirmed tumor take, mice were treated with TMZ (20 mg/mg 5 days on/2 days off x3 or 100mg/kg/day for 5 days) or whole brain XRT (2 Gy/day for 5 days). Control groups received vehicle or sham XRT. Final endpoint was survival by humane endpoints and tumors were fixed in formalin for histologic evaluation. Results A wide variation in expression levels of EGFR, EGFRvIII, MGMT and mGluR3 was observed in the PDX GBM panel. Three models had EGFRvIII mutation and all models had variable expression levels of EGFR. XRT showed a variable efficacy outcome on both tumor volume and survival in the PDX GBM models in the subcutaneous and orthotopic setting. TMZ showed efficacy in ST610 and ST2473 whereas ST146 and ST112 were resistant towards TMZ. Histologic evaluation showed typical characteristics of GBM tumors. Conclusion A panel of GBM PDX models was characterized for several molecular markers and the panel reflected the heterogeneity of human GBM tumors. The orthotopic GBM PDX models showed a wide range of sensitivity towards both TMZ and XRT. The established panel of orthotopic GBM PDX models can be used as a platform for testing of new drugs in a setting that more closely mimic the GBM tumor microenvironment and impact of the BBB. Citation Format: Mette Munk Jensen, Michael J. Wick, Lotte K. Kristensen, Maria Z. Alfsen, Laura A. Paludan, Mark Juul, Melissa Rundle, Kyriakos P. Papadopoulos, Andreas Kjær, Carsten H. Nielsen. Characterization of a panel of orthotopic glioblastoma multiforme (GBM) patient-derived xenograft (PDX) mouse models and efficacy evaluation of temozolomide and external radiation therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2161.

Identify a Blood-Brain Barrier Penetrating Drug-TNB using Zebrafish Orthotopic Glioblastoma Xenograft Model

The blood–brain barrier (BBB) is necessary for maintaining brain homeostasis, but it also represents a major challenge for drug delivery to the brain tumors. A suitable in vivo Glioblastoma Multiforme (GBM) model is needed for efficient testing of BBB crossable pharmaceuticals. In this study, we firstly confirmed the BBB functionality in 3dpf zebrafish embryos by Lucifer Yellow, Evans Blue and DAPI microinjection. We then transplanted human GBM tumor cells into the zebrafish brain, in which implanted GBM cells (U87 and U251) were highly mitotic and invasive, mimicking their malignancy features in rodents’ brain. Interestingly, we found that, although extensive endothelial proliferation and vessel dilation were observed in GBM xenografts, the BBB was still not disturbed. Next, using the zebrafish orthotopic GBM xenograft model as an in vivo visual readout, we successfully identified a promising small compound named TNB, which could efficiently cross the zebrafish BBB and inhibit the progression of orthotopic GBM xenografts. These results indicate that TNB is a promising BBB crossable GBM drug worth to be further characterized in human BBB setting, also suggest the zebrafish orthotopic GBM model as an efficient visual readout for the BBB penetrating anti-GBM drugs.

Guanylate binding protein-1 mediates EGFRvIII and promotes glioblastoma growth in vivo but not in vitro.

Glioblastoma multiforme (GBM) is the most common and deadly primary brain tumor in adults. Epidermal growth factor receptor (EGFR) is frequently amplified and mutated in GBM. We previously reported that Guanylate binding protein-1 (GBP1) is a novel transcriptional target gene of EGFR and plays a role in GBM invasion. Here we demonstrate that GBP1 can also be induced by EGFRvIII at the transcriptional level through the p38 MAPK/Yin Yang 1 (YY1) signaling pathway. Silencing of GBP1 by RNA interference significantly inhibits EGFRvIII-mediated GBM cell proliferation in vitro and in a mouse model. Overexpression of GBP1 has no obvious effect on glioblastoma cell proliferation in vitro. In contrast, in an orthotopic glioma mouse model GBP1 overexpression significantly promotes glioma growth and reduces survival rate of glioma-bearing mice by increasing cell proliferation and decreasing cell apoptosis in tumor. Clinically, GBP1 expression is elevated in human GBM tumors and positively correlates with EGFRvIII status in GBM specimens, and its expression is inversely correlated with the survival rate of GBM patients. Taken together, these results reveal that GBP1 may serve as a potential therapeutic target for GBMs with EGFRvIII mutation.

GENO-02INTEGRATED ANALYSIS OF MOLECULAR SUBTYPES IN GLIOBLASTOMA MULTIFORME

BACKGROUND: The Cancer Genome Atlas (TCGA) project previously identified genetic changes in the DNA sequence and copy number, DNA methylation, and gene expression of glioblastoma multiforme (GBM) tumors, leading to an enthused effort to compile and characterize changes in the genome, transcriptome, and proteome of human GBM tumors, so that aberrantly functioning molecular pathways and tumor subtypes could be identified. METHODS: Agilent GeneSpring and Mass Profiler Professional (MPP) software was used to perform integrated multi-omics analysis of mRNA expression, miRNA expression, protein expression, and copy number aberration associated with GBM. Additionally, analysis was performed on an independent discovery proteomics study of GBM and control (brain fragments from epilepsy surgery) patients measured using a label-free proteomics approach. RESULTS: Correlation analysis performed between mRNA and miRNA datasets from TCGA identified potential candidate miRNAs regulating the known Proneural signature genes OLIG2, NKX2-2, and SOX11. It also highlighted the molecular events leading to suppression of p53 in Proneural tumor signaling. Sample-sample correlation and PCA analysis on patient specimens resulted in clear separation between control and tumor samples. In addition, the tumor samples were segregated into two to three subgroups, suggesting that different TCGA subtypes may be present. Indeed, combined analysis of mRNA expression data from TCGA study and proteomics data from the label-free study identified a core subset of 54 GBM subtype signatures, clearly differentiating the known subtypes in the larger TCGA cohort. CONCLUSION: Our observation suggests that GBM tumor heterogeneity may be best characterized by both mRNA and protein abundance of the signature genes, opening a possibility for follow-up studies with potential diagnostic and clinical significance.

Isolation and Culturing of Glioma Cancer Stem Cells.

In many human cancers including malignant glioblastoma multiforme (GBM), cancer stem cells (CSCs) are thought to be responsible for tumor initiation, metastasis and resistance to conventional anti-cancer therapies. Therefore, a CSC-targeted drug delivery strategy to eliminate CSCs is a desirable approach for developing a more effective therapeutic. Moreover, isolated CSCs will provide an invaluable tool for studying the underlying cellular mechanisms of tumor development and provide insight into therapeutic options for successful eradication of CSCs. This unit describes a method for the isolation and culture of CSCs from human GBM tumor tissue.

ET-34 * HIGHLY SELECTIVE HSV VIROTHERAPY FOR TREATMENT OF GLIOBLASTOMA

Glioblastoma Multiforme (GBM) is an aggressive brain cancer for which there is no effective treatment. Oncolytic HSV vectors (oHSV) are attenuated lytic viruses that have shown promise in the treatment of human GBM models in animals. Although proven safe for treatment of GBM in patients, oHSVs efficacy has been limited, a consequence of poor intra-tumoral virus replication and spread. To counter these limitations, we have developed oHSVs whose selective replication in GBM cells does not rely on defective genes. This was accomplished by (i) full retargeting of oHSV to utilize the epidermal growth factor receptor (EGFR) for infection of human GBM tumor cells and (ii) further vector engineering to modify the essential HSV immediate early gene (ICP4) for sensitivity to repression by the microRNA mir-124. Mir-124 is highly expressed in neurons but virtually absent in GBM and highly conserved among different species. The mir-124-regulated vector was unable to replicate in nude mice following intracranial inoculation supporting vector safety and was shown to be effective (50-60% long term survival) in the treatment of human GBM in nude mice. To enhance vector intra-tumor vector spread, our EGFR retargeted-mir-124 controlled vector was further modified by vector arming with the matrix metalloproteinase gene encoding MMP9. MMP9 degrades collagen type IV, a major component of the extracellular matrix (ECM) and basement membranes of glioblastomas but absent in normal brain tissue. Studies are ongoing to determine whether MMP9 expression enhances vector spread in GBM neurospheres and as a therapeutic agent for enhanced treatment of human GBM in animals.

Ultrastructural characterization of primary cilia in pathologically characterized human glioblastoma multiforme (GBM) tumors.

BackgroundPrimary cilia are non-motile sensory cytoplasmic organelles that are involved in cell cycle progression. Ultrastructurally, the primary cilium region is complex, with normal ciliogenesis progressing through five distinct morphological stages in human astrocytes. Defects in early stages of ciliogenesis are key features of astrocytoma/glioblastoma cell lines and provided the impetus for the current study which describes the morphology of primary cilia in molecularly characterized human glioblastoma multiforme (GBM) tumors.MethodsSeven surgically resected human GBM tissue samples were molecularly characterized according to IDH1/2 mutation status, EGFR amplification status and MGMT promoter methylation status and were examined for primary cilia expression and structure using indirect immunofluorescence and electron microscopy.ResultsWe report for the first time that primary cilia are disrupted in the early stages of ciliogenesis in human GBM tumors. We confirm that immature primary cilia and basal bodies/centrioles have aberrant ciliogenesis characteristics including absent paired vesicles, misshaped/swollen vesicular hats, abnormal configuration of distal appendages, and discontinuity of centriole microtubular blades. Additionally, the transition zone plate is able to form in the absence of paired vesicles on the distal end of the basal body and when a cilium progresses beyond the early stages of ciliogenesis, it has electron dense material clumped along the transition zone and a darkening of the microtubules at the proximal end of the cilium.ConclusionsPrimary cilia play a role in a variety of human cancers. Previously primary cilia structure was perturbed in cultured cell lines derived from astrocytomas/glioblastomas; however there was always some question as to whether these findings were a cell culture phenomena. In this study we confirm that disruptions in ciliogenesis at early stages do occur in GBM tumors and that these ultrastructural findings bear resemblance to those previously observed in cell cultures. This is the first study to demonstrate that defects in cilia expression and function are a true hallmark of GBM tumors and correlate with their unrestrained growth. A review of the current ultrastructural profiles in the literature provides suggestions as to the best possible candidate protein that underlies defects in the early stages of ciliogenesis within GBM tumors.

MicroRNA-21 Promotes Glioblastoma Tumorigenesis by Down-regulating Insulin-like Growth Factor-binding Protein-3 (IGFBP3)

Despite advances in surgery, imaging, chemotherapy, and radiation, patients with glioblastoma multiforme (GBM), the most common histological subtype of glioma, have an especially dismal prognosis; >70% of GBM patients die within 2 years of diagnosis. In many human cancers, the microRNA miR-21 is overexpressed, and accumulating evidence indicates that it functions as an oncogene. Here, we report that miR-21 is overexpressed in human GBM cell lines and tumor tissue. Moreover, miR-21 expression in GBM patient samples is inversely correlated with patient survival. Knockdown of miR-21 in GBM cells inhibited cell proliferation in vitro and markedly inhibited tumor formation in vivo. A number of known miR-21 targets have been identified previously. By microarray analysis, we identified and validated insulin-like growth factor (IGF)-binding protein-3 (IGFBP3) as a novel miR-21 target gene. Overexpression of IGFBP3 in glioma cells inhibited cell proliferation in vitro and inhibited tumor formation of glioma xenografts in vivo. The critical role that IGFBP3 plays in miR-21-mediated actions was demonstrated by a rescue experiment, in which IGFBP3 knockdown in miR-21KD glioblastoma cells restored tumorigenesis. Examination of tumors from GBM patients showed that there was an inverse relationship between IGFBP3 and miR-21 expression and that increased IGFBP3 expression correlated with better patient survival. Our results identify IGFBP3 as a novel miR-21 target gene in glioblastoma and suggest that the oncogenic miRNA miR-21 down-regulates the expression of IGFBP3, which acts as a tumor suppressor in human glioblastoma.

MiR-124 inhibits the growth of glioblastoma through the downregulation of SOS1

Glioblastoma multiforme (GBM) is a lethal brain tumor in adults. Despite advances in treatments, such as surgery, radiotherapy and chemotherapy, high‑grade glioma remains fatal. The molecular and cellular mechanisms for GBM are not entirely clear and further studies are required to elucidate these. MicroRNAs (miRNAs) are small, non‑coding, endogenous RNAs that are involved in cell differentiation and proliferation, and have been suggested to play a role in a variety of types of cancer. In this study, we investigated the role of miR-124 in the inhibition of proliferation of GBM cells. The downregulation of miR-124 in human GBM tumor cell lines was detected using quantitative RT-PCR. To assess the function of miR-124, we constructed stable cell lines, U87-124 and U373-124, which overexpressed miR-124 using lentiviral vectors. Overexpression of miR-124 inhibited the proliferation of GBM cancer cells in vitro. Using integrated bioinformatics analysis, SOS1 was found to be a direct target for miR-124, which is frequently upregulated in gliomas. Dual‑luciferase reporter assays confirmed that the SOS1 mRNA 3'‑untranslated regions (UTR) was directly targeted by miR-124 and that the mutated 3'UTR was not affected. This was revealed to be mechanistically associated with the induction of SOS/Ras/Raf/ERK and the suppression of ERK activity, which was achieved by silencing SOS1. This study therefore indicates an important role for miR-124 in the regulation of growth in the molecular etiology of GBM, and offers a potential strategy for the use of miR-124 in cancer treatment.

Treatment of brain glioblastoma multiforme with pcDNA3.1-Egr. 1p-p16 combined with gamma knife radiation: An experimental study on nude mice

High post-operative recurrence and poor prognosis are likely to be related to the infiltrative growth of the glioblastoma multiforme (GBM). The primary objective of this study is to investigate the possible synergistic effect of the combined treatment of gamma knife radio-surgery (GKRS) and gene therapy for GBM and secondary objective is to explore the role of GKRS for the temporal and spatial regulation of the gene expression. The study performed on 70 nude mice and randomly divided into seven groups. Subcutaneous injection of human GBM tumor cells (T98G) was carried out to establish the animal models. Various doses of liposome-mediated pcDNA3.1-Egr. 1p-p16 recombinant plasmid were transfected through intra-tumor injection. GKRS was scheduled following the plasmid transfection. Tumor volumes were measured every 4 days after the treatment. Subcutaneous tumor nodule specimens were collected to analyze the cell apoptosis and p16 gene expression using terminal-deoxynucleoitidyl transferase mediated nick end labeling staining and reverse transcription-polymerase chain reaction. Tumor volumes, levels of cell apoptosis and p16 gene expression were compared between groups. Rates of tumor growth were significantly lower in the pcDNA3.1-Egr. 1p-p16 plasmid + GKRS groups than that in the remaining groups 28 days following the GKRS management. The p16mRNA expression was noted in both of the pcDNA3.1-Egr. 1p-p16 plasmid group and the pcDNA3.1-Egr. 1p-p16 plasmid + GKRS with marginal-dose of 20 Gy group. The level of messenger ribonucleic acid expression was higher in the pcDNA3.1-Egr. 1p-p16 plasmid + GKRS with the marginal-dose of 20 Gy group, with a markedly increased apoptotic and necrotic cells, than that in the pcDNA3.1-Egr. 1p-p16 plasmid group. In animal studies, pcDNA3.1-Egr. 1p-p16 in combination with GKRS is a preferable management option for the GBM to the sole use of GKRS or gene therapy. It may be a novel approach for the treatment of human patient with GBM.

Candidate Pathways for Promoting Differentiation or Quiescence of Oligodendrocyte Progenitor-like Cells in Glioma

Platelet-derived growth factor receptor alpha-positive oligodendrocyte progenitor cells (OPC) located within the mature central nervous system may remain quiescent, proliferate, or differentiate into oligodendrocytes. Human glioblastoma multiforme tumors often contain rapidly proliferating oligodendrocyte lineage transcription factor 2 (Olig2)-positive cells that resemble OPCs. In this study, we sought to identify candidate pathways that promote OPC differentiation or quiescence rather than proliferation. Gene expression profiling conducted in both normal murine OPCs and highly proliferative Olig2-positive glioma cells identified all the transcripts associated with the highly proliferative state of these cells and showed that among the various cell types found within the brain, Olig2-positive tumor cells are most similar to OPCs. We then subtracted OPC transcripts found in tumor samples from those found in normal brain samples and identified 28 OPC transcripts as candidates for promoting differentiation or quiescence. Systematic analysis of human glioma data revealed that these genes have similar expression profiles in human tumors and were significantly enriched in genomic deletions, suggesting an antiproliferative role. Treatment of primary murine glioblastoma cells with agonists of one candidate gene, Gpr17, resulted in a decreased number of neurospheres. Together, our findings show that comparison of the molecular phenotype of progenitor cells in tumors to the equivalent cells in the normal brain represents a novel approach for the identification of targeted therapies.

Encapsulated therapeutic stem cells implanted in the tumor resection cavity induce cell death in gliomas

Therapeutically engineered stem cells have shown promise for glioblastoma multiforme (GBM) therapy; however, key preclinical studies are urgently needed for their clinical translation. In this study, we investigated a new approach to GBM treatment using therapeutic stem cells encapsulated in biodegradable, synthetic extracellular matrix (sECM) in mouse models of human GBM resection. Using multimodal imaging, we first showed quantitative surgical debulking of human GBM tumors in mice, which resulted in increased survival. Next, sECM encapsulation of engineered stem cells increased their retention in the tumor resection cavity, permitted tumor-selective migration and release of diagnostic and therapeutic proteins in vivo. Simulating the clinical scenario of GBM treatment, the release of tumor-selective S-TRAIL (secretable tumor necrosis factor apoptosis inducing ligand) from sECM-encapsulated stem cells in the resection cavity eradicated residual tumor cells by inducing caspase-mediated apoptosis, delayed tumor regrowth and significantly increased survival of mice. This study demonstrates the efficacy of encapsulated therapeutic stem cells in mouse models of GBM resection and may have implications for developing effective therapies for GBM.

Guanylate binding protein 1 is a novel effector of EGFR-driven invasion in glioblastoma

Although GBP1 (guanylate binding protein 1) was among the first interferon-inducible proteins identified, its function is still largely unknown. Epidermal growth factor receptor (EGFR) activation by amplification or mutation is one of the most frequent genetic lesions in a variety of human tumors. These include glioblastoma multiforme (GBM), which is characterized by independent but interrelated features of extensive invasion into normal brain parenchyma, rapid growth, necrosis, and angiogenesis. In this study, we show that EGFR activation promoted GBP1 expression in GBM cell lines through a signaling pathway involving Src and p38 mitogen-activated protein kinase. Moreover, we identified YY1 (Yin Yang 1) as the downstream transcriptional regulator regulating EGFR-driven GBP1 expression. GBP1 was required for EGFR-mediated MMP1 (matrix metalloproteinase 1) expression and glioma cell invasion in vitro. Although deregulation of GBP1 expression did not affect glioma cell proliferation, overexpression of GBP1 enhanced glioma cell invasion through MMP1 induction, which required its C-terminal helical domain and was independent of its GTPase activity. Reducing GBP1 levels by RNA interference in invasive GBM cells also markedly inhibited their ability to infiltrate the brain parenchyma of mice. GBP1 expression was high and positively correlated with EGFR expression in human GBM tumors and cell lines, particularly those of the neural subtype. Together, these findings establish GBP1 as a previously unknown link between EGFR activity and MMP1 expression and nominate it as a novel potential therapeutic target for inhibiting GBM invasion.