DIPG-50. Bioinformatic evaluation of genes involved in sphingomyelin biosynthesis in Diffuse Midline Glioma H3K27 altered/DIPG: dysregulation of sphingosine 1-phosphate (SP1)

Sphingosine 1-phosphate (S1P), a bioactive signalling lipid, interacts with a network of metabolic enzymes, receptors, transporters, and epigenetic partners. This network is well described in many cancers; however, little is known about its potential impact in DIPG. Expression of HDAC1 (binding target of S1P) and genes associated with the sphingomyelin (SM) pathway were examined in datasets identified in the National Centre for Biotechnology Information, Gene Expression Omnibus, and analysed using the R2: Genomics Analysis and Visualization Platform (http://r2.amc.nl). The Paugh-DIPG dataset (27 DIPG samples) and normal samples (20 years and younger - Berchtold dataset) were compared. To avoid issues related to batch effects, expression values for each gene of interest and controls were exported into separate files to determine differentially expressed genes. Internal genes include housekeeping; ACTB, GAPDH, B2M, TBP; downregulated in DIPG; GPR6, NGB, and upregulated in DIPG; MMP16, PDGFRA, TP53, CSPG4. Genes of interest; SPHK1, SPHK2, SGPL1, ACER1, ACER3, KDSR, SMPD1-4, CPTP, GLTP, DEGS1, CERK, CERS1-6, ASAH1, SGPP1, SGPP2 and HDAC1. To test for significance, each dataset was standardised using ACTB housekeeping gene. Values including Log-transformed fold change were analysed using the non-parametric, Mann-Whitney test. 7 of the 16 genes were dysregulated relative to expression in normal brain (p<0.0002). SPHK2 and SMPD3 were downregulated, and HDAC1, SGPL1, DEGS1, CERS4, and ASAH1 were upregulated in DIPG compared to normal. To identify genes more likely associated with DIPG (vs development), we evaluated gene expression in Brainspan dataset (brspv10rs). Validation of SPHK2 and SGPL1 protein expression (responsible for the synthesis and cleavage of SP1) is underway. Current work is focused on the intracellular processing and function (isoform specific inhibitors) of S1P in DIPG cells. Given its reported role in several cancer hallmarks, a better understanding of the sphingomyelin biosynthesis pathway in DMG/DIPG is merited and may lead to novel therapeutic targets.

The Long Non-Coding RNA H19 Drives the Proliferation of Diffuse Intrinsic Pontine Glioma with H3K27 Mutation

Diffuse intrinsic pontine glioma (DIPG) is an incurable paediatric malignancy. Identifying the molecular drivers of DIPG progression is of the utmost importance. Long non-coding RNAs (lncRNAs) represent a large family of disease- and tissue-specific transcripts, whose functions have not yet been elucidated in DIPG. Herein, we studied the oncogenic role of the development-associated H19 lncRNA in DIPG. Bioinformatic analyses of clinical datasets were used to measure the expression of H19 lncRNA in paediatric high-grade gliomas (pedHGGs). The expression and sub-cellular location of H19 lncRNA were validated in DIPG cell lines. Locked nucleic acid antisense oligonucleotides were designed to test the function of H19 in DIPG cells. We found that H19 expression was higher in DIPG vs. normal brain tissue and other pedHGGs. H19 knockdown resulted in decreased cell proliferation and survival in DIPG cells. Mechanistically, H19 buffers let-7 microRNAs, resulting in the up-regulation of oncogenic let-7 target (e.g., SULF2 and OSMR). H19 is the first functionally characterized lncRNA in DIPG and a promising therapeutic candidate for treating this incurable cancer.

OPTC-4. Bioinformatic analysis of COLXIα1 gene expression and its alternative splicing regulation in Paediatric Diffuse Intrinsic Pontine Gliomas (DIPGs)

Paediatric Diffuse Intrinsic Pontine Glioma (DIPGs), is a rare aggressive childhood malignancy that arise in a region and age specific manner, with no cure and children seldom survive 2 years after diagnosis. There has been significant advances in genomic and molecular identification of driver genes as well as signature mutations that help with diagnosis. A multi-methodological approach to begin to profile the DIPG/host landscape in the context of developing brainstem was conducted. Bioinformatic analyses of a DIPG dataset and normal developing brain dataset to help separate expression associated with development from tumour was conducted. In parallel; fixed-formalin paraffin embedded DIPG tissue was obtained from post-mortem brain for focused RNA arrays and RNAseq. Two of several overlapping genes that were overexpressed in DIPG was tenascin C and the collagen XI (α1) gene (COL11A1). A common feature of these genes is that they are alternatively spliced. Therefore, the aim of this study was to focus on COL11A1, further explore its expression in diffuse midline gliomas (DMGs), to determine association with H3K27M alterations and to explore the use of bioinformatic programmes that could potentially predict the specific Col11α1 isoform expression in DIPG. The following programs were used to determine if a bioinformation approach could aid in our understanding of alternative splicing in development and DIPG: R2: Genomics Analysis and Visualization Platform, SnapGene program, Basic Local Alignment Search Tools (BLAST), RNA Interactome Database (RNAInter). In silico analysis highlited an RNA-binding protein eIF4A3 as a candidate of alternative splicing regulator of COL11A1 gene. EIF4A3 gene was shown to be upreguated in DIPG using publicly available datasets. Results shows that isoform A is the most likely isoform present in DIPG. The data obtained will help inform future in vitro and in vivo investigations into the potential role of COL11A1 and its isoforms in DIPG.

Fucosyltransferase 4 and 7 mediates adhesion of non-small cell lung cancer cells to brain-derived endothelial cells and results in modification of the blood-brain-barrier: in vitro investigation of CD15 and CD15s in lung-to-brain metastasis

PURPOSE

Metastatic non-small cell lung (NSCLC) cancer represents one of the most common types of brain metastasis. The mechanisms involved in how circulating cancer cells transmigrate into brain parenchyma are not fully understood. The aim of this work was to investigate the role of fucosylated carbohydrate epitopes CD15 and sialyated CD15s in cancer adhesion to brain-derived endothelial cells and determine their influence in blood-brain barrier (BBB) disruption METHODS: Three distinct, independent methods were used to measure brain endothelial integrity and include voltohmmeter (EVOM™), impedance spectroscopy (CellZscope®) and electric cell-substrate impedance sensing system (ECIS™). Two fucosyltransferases (FUT4 and 7) responsible for CD15 and CD15s synthesis were modulated in four human cancer cell lines (three lung cancer and one glioma).

RESULTS

Overexpression of CD15 or CD15s epitopes led to increase in adhesion of cancer cells to cerebral endothelial cells compared with wild-type and cells with silenced CD15 or CD15s (p < 0.01). This overexpression led to the disruption of cerebral endothelial cell monolayers (p < 0.01). Knockdown of FUT4 and FUT7 in metastatic cancer cells prevented disruption of an in vitro BBB model. Surprisingly, although the cells characterised as 'non-metastatic', they became 'metastatic' -like when cells were forced to over-express either FUT4 or FUT7.

CONCLUSIONS

Results from these studies suggest that overexpression of CD15 and CD15s could potentiate the transmigration of circulating NSCLC cells into the brain. The clinical significance of these studies includes the possible use of these epitopes as biomarkers for metastasis.

Real-time acquisition of transendothelial electrical resistance in an all-human, in vitro, 3-dimensional, blood-brain barrier model exemplifies tight-junction integrity

The blood–brain barrier (BBB) consists of endothelial cells, astrocytes, and pericytes embedded in basal lamina (BL). Most in vitro models use nonhuman, monolayer cultures for therapeutic-delivery studies, relying on transendothelial electrical resistance (TEER) measurements without other tight-junction (TJ) formation parameters. We aimed to develop reliable, reproducible, in vitro 3-dimensional (3D) models incorporating relevant human, in vivo cell types and BL proteins. The 3D BBB models were constructed with human brain endothelial cells, human astrocytes, and human brain pericytes in mono-, co-, and tricultures. TEER was measured in 3D models using a volt/ohmmeter and cellZscope. Influence of BL proteins—laminin, fibronectin, collagen type IV, agrin, and perlecan—on adhesion and TEER was assessed using an electric cell-substrate impedance–sensing system. TJ protein expression was assessed by Western blotting (WB) and immunocytochemistry (ICC). Perlecan (10 µg/ml) evoked unreportedly high, in vitro TEER values (1200 Ω) and the strongest adhesion. Coculturing endothelial cells with astrocytes yielded the greatest resistance over time. ICC and WB results correlated with resistance levels, with evidence of prominent occludin expression in cocultures. BL proteins exerted differential effects on TEER, whereas astrocytes in contact yielded higher TEER values and TJ expression.—Maherally, Z., Fillmore, H. L., Tan, S. L., Tan, S. F., Jassam, S. A., Quack, F. I., Hatherell, K. E., Pilkington, G. J. Real-time acquisition of transendothelial electrical resistance in an all-human, in vitro, 3-dimensional, blood–brain barrier model exemplifies tight-junction integrity.

CD15s/CD62E Interaction Mediates the Adhesion of Non-Small Cell Lung Cancer Cells on Brain Endothelial Cells: Implications for Cerebral Metastasis

Expression of the cell adhesion molecule (CAM), Sialyl Lewis X (CD15s) correlates with cancer metastasis, while expression of E-selectin (CD62E) is stimulated by TNF-α. CD15s/CD62E interaction plays a key role in the homing process of circulating leukocytes. We investigated the heterophilic interaction of CD15s and CD62E in brain metastasis-related cancer cell adhesion. CD15s and CD62E were characterised in human brain endothelium (hCMEC/D3), primary non-small cell lung cancer (NSCLC) (COR-L105 and A549) and metastatic NSCLC (SEBTA-001 and NCI-H1299) using immunocytochemistry, Western blotting, flow cytometry and immunohistochemistry in human brain tissue sections. TNF-α (25 pg/mL) stimulated extracellular expression of CD62E while adhesion assays, under both static and physiological flow live-cell conditions, explored the effect of CD15s-mAb immunoblocking on adhesion of cancer cell–brain endothelium. CD15s was faintly expressed on hCMEC/D3, while high levels were observed on primary NSCLC cells with expression highest on metastatic NSCLC cells (p < 0.001). CD62E was highly expressed on hCMEC/D3 cells activated with TNF-α, with lower levels on primary and metastatic NSCLC cells. CD15s and CD62E were expressed on lung metastatic brain biopsies. CD15s/CD62E interaction was localised at adhesion sites of cancer cell–brain endothelium. CD15s immunoblocking significantly decreased cancer cell adhesion to brain endothelium under static and shear stress conditions (p < 0.001), highlighting the role of CD15s–CD62E interaction in brain metastasis.

TNF-α enhancement of CD62E mediates adhesion of non-small cell lung cancer cells to brain endothelium via CD15 in lung-brain metastasis

BACKGROUND

CD15, which is overexpressed on various cancers, has been reported as a cell adhesion molecule that plays a key role in non-CNS metastasis. However, the role of CD15 in brain metastasis is largely unexplored. This study provides a better understanding of CD15/CD62E interaction, enhanced by tumor necrosis factor-α (TNF-α), and its correlation with brain metastasis in non-small cell lung cancer (NSCLC).

METHODS

CD15 and E-selectin (CD62E) expression was demonstrated in both human primary and metastatic NSCLC cells using flow cytometry, immunofluorescence, and Western blotting. The role of CD15 was investigated using an adhesion assay under static and physiological flow live-cell conditions. Human tissue sections were examined using immunohistochemistry.

RESULTS

CD15, which was weakly expressed on hCMEC/D3 human brain endothelial cells, was expressed at high levels on metastatic NSCLC cells (NCI-H1299, SEBTA-001, and SEBTA-005) and at lower levels on primary NSCLC (COR-L105 and A549) cells (P < .001). The highest expression of CD62E was observed on hCMEC/D3 cells activated with TNF-α, with lower levels on metastatic NSCLC cells followed by primary NSCLC cells. Metastatic NSCLC cells adhered most strongly to hCMEC/D3 compared with primary NSCLC cells. CD15 immunoblocking decreased cancer cell adhesion to brain endothelium under static and shear stress conditions (P < .0001), confirming a correlation between CD15 and cerebral metastasis. Both CD15 and CD62E expression were detected in lung metastatic brain biopsies.

CONCLUSION

This study enhances the understanding of cancer cell-brain endothelial adhesion and confirms that CD15 plays a crucial role in adhesion in concert with TNF-α activation of its binding partner, CD62E.

The Regulation and Function of Lactate Dehydrogenase A: Therapeutic Potential in Brain Tumor

There are over 120 types of brain tumor and approximately 45% of primary brain tumors are gliomas, of which glioblastoma multiforme (GBM) is the most common and aggressive with a median survival rate of 14 months. Despite progress in our knowledge, current therapies are unable to effectively combat primary brain tumors and patient survival remains poor. Tumor metabolism is important to consider in therapeutic approaches and is the focus of numerous research investigations. Lactate dehydrogenase A (LDHA) is a cytosolic enzyme, predominantly involved in anaerobic and aerobic glycolysis (the Warburg effect); however, it has multiple additional functions in non‐neoplastic and neoplastic tissues, which are not commonly known or discussed. This review summarizes what is currently known about the function of LDHA and identifies areas that would benefit from further exploration. The current knowledge of the role of LDHA in the brain and its potential as a therapeutic target for brain tumors will also be highlighted. The Warburg effect appears to be universal in tumors, including primary brain tumors, and LDHA (because of its involvement with this process) has been identified as a potential therapeutic target. Currently, there are, however, no suitable LDHA inhibitors available for tumor therapies in the clinic.

Abstract 3042: A novel integrated approach for deciphering the mitochondrial mutation enigma in glioblastoma

Glioblastoma multiforme (GBM) is the most common adult primary brain tumor. It is highly malignant with 2-year survival of just 27.2% following diagnosis. Treatment is hampered by its unique underlying biology, including differential inter- and intra-tumor responses to therapy.

Impaired mitochondrial function is a common feature of cancer cells in comparison to healthy cells. However, the precise contribution of single mitochondrial DNA (mtDNA) mutations to this impairment, and consequently to the development, progression and chemosensitivity of GBM remains poorly described.

To address this we have developed a novel integrated approach where we have: (1) obtained complete mitochondrial genomes from multiple GBM samples, (2) employed 3D structural mapping and analysis to predict the function of non-synonymous mtDNA-encoded complex III and IV mutations; (3) measured oxidative phosphorylation (OXPHOS) enzyme complex activities of GBM cell lines. Finally, to circumvent the current inability to genetically transform human mtDNA, we have employed humanized yeast technology to decipher the specific impact of single key mtDNA mutations on cellular growth and OXPHOS complex activity.

Over 200 mutations were identified in 42 GBM-mtDNAs using next generation sequencing. This included 9 functional candidates in complexes III and IV, with highly variable mutation loads, which were predicted to affect corresponding enzyme activity. Most were GBM-specific and not found in the general population, two were present in the germ-line and 43% of tumors carried at least one functional candidate.

Preliminary spectrophotometric measurements indicate a striking diversity of OXPHOS enzyme complex activity profiles between the GBM cell lines. One cell line exhibited a combined increase in complex I, II, linked II/III and IV activity compared to control. In 5 GBM cell lines, all complex I activities were altered (either elevated or reduced) and all complex IV activities were altered (mostly decreased), while the remaining cell line exhibited decreases in both complex I and IV activity combined with an increase in linked complex II/III activity.

Analysis of yeast cells that were genetically transformed to contain a single mutation that mimics the most prevalent functional candidate identified in GBM to date: F18L, revealed an alteration of complex III activity (quinol-cytochrome c reduction) probably caused by a modification of the substrate quinol binding.

Using our approach, we show for the first time that a single GBM-associated mtDNA mutation can have a direct effect on mitochondrial function, raising the possibility that small mitogenomic elements could contribute to the heterogeneous biology of GBM. This study paves the way for the systematic study of other functional candidates using humanized yeast technology, as well as other studies that explore their contribution to GBM cell behavior and drug sensitivity.

Citation Format: Rhiannon E. Lloyd, Kathleen Keatley, Anais Laleve, Samantha C. Higgins, Stavros Polyzoidis, Keyoumars Ashkan, Helen L. Fillmore, Simon J. Heales, John E. McGeehan, Iain Hargreaves, Brigitte Meunier, Geoffrey J. Pilkington. A novel integrated approach for deciphering the mitochondrial mutation enigma in glioblastoma. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3042. doi:10.1158/1538-7445.AM2015-3042

Wilms tumor 1 gene, CD97, and the emerging biogenetic profile of glioblastoma

Glioblastoma multiforme (GBM) is the most common type of primary brain tumor, and current treatment regimens are only marginally effective. One of the most vexing and malignant aspects of GBM is its pervasive infiltration into surrounding brain tissue. This review describes the role of the Wilms tumor 1 gene (WT1) and its relationship to GBM. WT1 has several alternative splicing products, one of which, the KTS(+) variant, has been demonstrated to be involved in the transcriptional activation of a variety of oncogenes as well as the inhibition of tumor suppressor genes. Further, this paper will examine the relationship of WT1 with CD97, a gene that codes for an epidermal growth factor receptor family member, an adhesion G-protein-coupled receptor, thought to promote tumor invasiveness and migration. The authors suggest that further research into WT1 and CD97 will allow clinicians to begin to deal more effectively with the infiltrative behavior displayed by GBM and design new therapies that target this deadly disease.

Identification and functional prediction of mitochondrial complex III and IV mutations associated with glioblastoma

Background

Glioblastoma (GBM) is the most common primary brain tumor in adults, with a dismal prognosis. Treatment is hampered by GBM's unique biology, including differential cell response to therapy. Although several mitochondrial abnormalities have been identified, how mitochondrial DNA (mtDNA) mutations contribute to GBM biology and therapeutic response remains poorly described. We sought to determine the spectrum of functional complex III and IV mtDNA mutations in GBM.

Methods

The complete mitochondrial genomes of 10 GBM cell lines were obtained using next-generation sequencing and combined with another set obtained from 32 GBM tissues. Three-dimensional structural mapping and analysis of all the nonsynonymous mutations identified in complex III and IV proteins was then performed to investigate functional importance.

Results

Over 200 mutations were identified in the mtDNAs, including a significant proportion with very low mutational loads. Twenty-five were nonsynonymous mutations in complex III and IV, 9 of which were predicted to be functional and affect mitochondrial respiratory chain activity. Most of the functional candidates were GBM specific and not found in the general population, and 2 were present in the germ-line. Patient-specific maps reveal that 43% of tumors carry at least one functional candidate.

Conclusions

We reveal that the spectrum of GBM-associated mtDNA mutations is wider than previously thought, as well as novel structural-functional links between specific mtDNA mutations, abnormal mitochondria, and the biology of GBM. These results could provide tangible new prognostic indicators as well as targets with which to guide the development of patient-specific mitochondrially mediated chemotherapeutic approaches.

Dual targeting NG2 and GD3A using Mab-Zap immunotoxin results in reduced glioma cell viability in vitro

BACKGROUND

Effective treatments for glioblastoma multiforme (GBM) are lacking due, in part, to cellular heterogeneity. Consequently, single-target therapeutic strategies are unlikely to succeed. Simultaneous targeting of different neoplastic cell populations within the same tumour may, therefore, prove of value. Neuron-glia 2 (NG2), a transmembrane chondroitin sulphate proteoglycan, present on developing glial cells, and GD3(A), a ganglioside expressed on developing migratory glia, are re-expressed in GBM.

MATERIALS AND METHODS

The aims of this study were to conduct 'proof of concept' experiments in human GBM cell lines to show that proliferative high NG2-expressing cells and high GD3(A) -expressing migratory cells could be effectively ablated using a Mab-Zap saporin immunotoxin system.

RESULTS

The combinatorial ablation of both NG2 and GD3(A)-expressing cells resulted in significant reduction in GBM cell viability compared to single epitope targeting and controls (p<0.0001); non-neoplastic astrocytes were not affected.

CONCLUSION

Multiple targeting of GBM sub-populations may, therefore, help inform novel therapeutic approaches.

Expression of the chondroitin sulphate proteoglycan, NG2, in paediatric brain tumors

BACKGROUND/AIM

While neuron-glia 2 (NG2) is well-characterized in the developing brain and in adult high-grade gliomas, little is known about NG2 expression in paediatric brain tumors. Here, NG2 expression was examined in a range of paediatric brain tumors.

MATERIALS AND METHODS

A retrospective immunohistopathological analysis of 57 paediatric brain tumor biopsies of various tumor types was carried out. Paediatric cell lines, including two medulloblastomas and one dysembryoplastic neuroepithelial tumor, in addition to one adult high-grade glioma, were also assessed for NG2 expression.

RESULTS

NG2-positive staining was seen in all dysembryoplastic neuroepithelial tumors (DNETs) examined; however, only two of the fourteen medulloblastomas examined were NG2-positive. Compared to adult glioma, there was a lack of NG2 staining in the vasculature of paediatric brain tumors.

CONCLUSION

NG2 expression in paediatric brain tumors differs depending upon type and, unlike adult glioma, includes expression on lower-grade tumors.

Brain tumor cell line authentication, an efficient alternative to capillary electrophoresis by using a microfluidics-based system

BACKGROUND

The current method for cell line authentication is genotyping based on short tandem repeat (STR)-PCR involving coamplification of a panel of STR loci by multiplex PCR and downstream fragment length analysis (FLA), usually performed by capillary electrophoresis. FLA by capillary electrophoresis is time-consuming and can be expensive, as the facilities are generally not accessible for many research laboratories.

METHODS

In the present study, a microfluidic electrophoresis system, the Agilent 2100 Bioanalyzer, was used to analyze the STR-PCR fragments from 10 human genomic loci of a number of human cell lines, including 6 gliomas, 1 astrocyte, 1 primary lung cancer, 1 lung brain metastatic cancer, and 1 rhabdomyosarcoma; and this was compared with the standard method, that is, capillary electrophoresis, using the Applied Biosystems 3130xl Genetic Analyzer.

RESULTS

The microfluidic electrophoresis method produced highly reproducible results with good sensitivity in sizing of multiple PCR fragments, and each cell line demonstrated a unique DNA profile. Furthermore, DNA fingerprinting of samples from 5 different passage numbers of the same cell line showed excellent reproducibility when FLA was performed with the Bioanalyzer, indicating that no cross-contamination had occurred during the culture period.

CONCLUSION

This novel application provides a straightforward and cost-effective alternative to STR-based cell line authentication. In addition, this application would be of great value for cell bank repositories to maintain and distribute precious cell lines.

Novel report of expression and function of CD97 in malignant gliomas: correlation with Wilms tumor 1 expression and glioma cell invasiveness

OBJECT

The Wilms tumor 1 (WT1) protein-a developmentally regulated transcription factor-is aberrantly expressed in gliomas and promotes their malignant phenotype. However, little is known about the molecular allies that help it mediate its oncogenic functions in glioma cells.

METHODS

The authors used short interfering RNA (siRNA) to suppress WT1 expression in glioblastoma (GBM) cells and evaluated the effect of this on GBM cell invasiveness. Gene expression analysis was then used to identify the candidate genes that were altered as a result of WT1 silencing. One candidate target, CD97, was then selected for further investigation into its role by suppressing its expression using siRNA silencing, followed by proliferation and invasion assays.

RESULTS

WT1 levels were reliably and reproducibly suppressed by siRNA application. This resulted in a significant decrease in cellular invasiveness. Microarray analyses identified the gene products that were consistently downregulated (27) and upregulated (11) with WT1 silencing. Of these, CD97 expression was consistently suppressed across the 3 different GBM cell lines studied and was found on further investigation to significantly impact GBM cell invasiveness.

CONCLUSIONS

Although CD97 expression in gliomas has not been described previously, we conclude that the possible upregulation of CD97 mediated by WT1 promotes cellular invasiveness-one of the most characteristic and challenging aspects of glial tumor cells. Further studies are needed to clarify the nature of this regulation and its impact, as CD97 could represent a novel target for antiglioma therapies.

Matrix metalloproteinase-1 expression enhances tumorigenicity as well as tumor-related angiogenesis and is inversely associated with TIMP-4 expression in a model of glioblastoma

Herein we continue the study of matrix metalloproteinase-1 (MMP-1) with respect to glioblastoma multiforme (GBM) cell tumorigenicity and angiogenesis. A model of tumorigenicity with cells stably altered to over-express or knock-down MMP-1 revealed that it significantly increases tumor incidence and size. Organized endothelial growth in human umbilical vein endothelial cell (HUVEC)-GBM co-cultures was significantly increased in the presence of MMP-1. CD31 analysis of model tumors elucidated a substantial recruitment of endothelium in MMP-1 enhanced samples. Antibody arrays indicated an inverse expression of certain anti-angiogenic factors with respect to MMP-1, the most notable of which was a significant increase in tissue inhibitor of metalloproteinases-4 (TIMP-4) in the absence of MMP-1, as validated by immunoblot.

Conjugation of functionalized gadolinium metallofullerenes with IL-13 peptides for targeting and imaging glial tumors

Background: Glioblastoma multiforme is the most common and most lethal primary brain tumor in humans, with median survival of approximately 1 year. Owing to the ability of glioma cells to aggressively infiltrate normal brain tissue and survive exposure to current adjuvant therapies, there is a great need for specific targeted nanoplatforms capable of delivering both therapeutic and imaging agents directly to invasive tumor cells. Method: Gadolinium-containing endohedral fullerenes, highly efficient contrast agents for MRI, were functionalized and conjugated with a tumor-specific peptide and assessed for their ability to bind to glioma cells in vitro. Results: We report the successful conjugation of the carboxyl functionalized metallofullerene Gd3N@C80(OH)-26(CH2CH2COOH)-16 to IL-13 peptides and the successful targeting ability towards brain tumor cells that overexpress the IL-13 receptor (IL-13Rα2). Conclusion: These studies demonstrate that IL-13 peptide-conjugated gadolinium metallofullerenes could serve as a platform to deliver imaging and therapeutic agents to tumor cells.

A novel coaxial tube catheter for central nervous system infusions: performance characteristics in brain phantom gel

We tested a novel neurocatheter in a brain-tissue gel model of drug infusion via convection-enhanced delivery (CED) for the treatment of a variety of neurological diseases. CED is an alternative to systemic administration of agents by intravenous or oral routes, which are often less effective or carry risk of systemic side effects. We investigated two co-axial tube devices, with outer diameters of 1.6 mm and 2.0 mm. Bromophenol blue dye was infused into 400 ml of 0.6% agarose gel at 1 μl/min for 1 h, with/without the inner and outer tubes Luer-locked at the proximal end, with/without the inner tube primed, and with/without the inner tube preloaded into the outer tube upon insertion into the gel. The unlocked, primed, and unloaded configuration produced infusions that resulted in significantly less (p < 0.05) entrapped air escaping into the gel and resulted in no reflux of infusate.

Encapsulation of a radiolabeled cluster inside a fullerene cage, (177)Lu(x)Lu((3-x))N@C(80): an interleukin-13-conjugated radiolabeled metallofullerene platform

In this communication, we describe the successful encapsulation of (177)Lu into the endohedral metallofullerene (177)Lu(x)Lu(3-x)N@C(80) (x = 1-3) starting with (177)LuCl(3) in a modified quartz Kraschmer-Huffman electric generator. We demonstrate that the (177)Lu (beta-emitter) in this fullerene cage is not significantly released for a period of up to at least one-half-life (6.7 days). We also demonstrate that this agent can be conjugated with an interleukin-13 peptide that is designed to target an overexpressed receptor in glioblastoma multiforme tumors. This nanoparticle delivery platform provides flexibility for a wide range of radiotherapeutic and radiodiagnostic multimodal applications.

Stem cell biology in traumatic brain injury: effects of injury and strategies for repair

Approximately 350,000 individuals in the US are affected annually by severe and moderate traumatic brain injuries (TBI) that may result in long-term disability. This rate of injury has produced approximately 3.3 million disabled survivors in the US alone. There is currently no specific treatment available for TBI other than supportive care, but aggressive prehospital resuscitation, rapid triage, and intensive care have reduced mortality rates. With the recent demonstration that neurogenesis occurs in all mammals (including man) throughout adult life, albeit at a low rate, the concept of replacing neurons lost after TBI is now becoming a reality. Experimental rodent models have shown that neurogenesis is accelerated after TBI, especially in juveniles. Two approaches have been followed in these rodent models to test possible therapeutic approaches that could enhance neuronal replacement in humans after TBI. The first has been to define and quantify the phenomenon of de novo hippocampal and cortical neurogenesis after TBI and find ways to enhance this (for example by exogenous trophic factor administration). A second approach has been the transplantation of different types of neural progenitor cells after TBI. In this review the authors discuss some of the processes that follow after acute TBI including the changes in the brain microenvironment and the role of trophic factor dynamics with regard to the effects on endogenous neurogenesis and gliagenesis. The authors also discuss strategies to clinically harness the factors influencing these processes and repair strategies using exogenous neural progenitor cell transplantation. Each strategy is discussed with an emphasis on highlighting the progress and limiting factors relevant to the development of clinical trials of cellular replacement therapy for severe TBI in humans.

Abstract 261: Epidermal growth factor receptor (EGFR)-mediated upregulation of matrix metalloproteinase-1(MMP-1) in glioblastoma cell lines involves multiple signaling pathways

Glioblastoma Multiforme (GBM) is a devastating disease with an extremely poor prognosis primarily due to its invasive and infiltrative nature. Matrix metalloproteinases (MMPs) are important enzymes that regulate tumor microenvironment, alter cellular behavior and increase invasion and metastasis in wide variety of cancers. Previous studies from our laboratory have shown that MMP-1 is over expressed in GBM tissue and can influence glioma cell invasion in vitro. Since the epidermal growth factor receptor (EGFR) is amplified in human GBM, we wanted to determine the effect of EGFR activation by epidermal growth factor (EGF) on MMP-1 expression and invasion in human glioma cell lines and if so, determine the signaling mechanisms responsible for this induction. We stimulated glioma cell lines (T98 and U87) with EGF in the presence and absence of the EGFR inhibitor, AG1478. Inhibitors to multiple signaling pathways activated by EGFR induction were also used. All inhibitors tested were added to cells for 2 hrs prior to addition of EGF. In addition, transfections using AKT and STAT3 siRNA were conducted. Western Blotting was performed to examine the levels of MMP-1, EGFR, AKT, STAT3 and ERK. We observed that with EGF treatment, in addition to EGFR activation, AKT was phosphorylated, MMP-1 was induced and that in the presence of AG1478, AKT and EGFR phosphorylation was inhibited in a dose dependent manner. Importantly, MMP-1 up-regulation by EGF was abrogated in cells pretreated with AG1478. EGFR has been shown to up-regulate MAPK, PI3K and STAT3 pathways in glioma and other malignancies. Involvement of the MAPK pathway in the EGFR- mediated induction of MMP-1 was examined using the MAPK inhibitor, U0126. Only a modest decrease in MMP-1 levels was observed following treatment with EGF and U0126, suggesting potential inputs from other signaling pathways. Although there was a modest inhibition of AKT protein levels in cells treated with AKT siRNA, the levels of MMP-1 in these cells were significantly reduced. Current experiments focus on the role of AKT/PI3K and STAT3 signaling pathways in MMP-1 mediated glioma cell invasion.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 261.

Effect of WT1 gene silencing on the tumorigenicity of human glioblastoma multiforme cells

OBJECT

Wilms tumor 1 (WT1) is overexpressed in many human cancers, including glioblastoma multiforme (GBM). In another study, the authors showed that transient WT1 silencing increases the radiosensitivity of glioma cells. Studies of nonglioma cell lines have demonstrated that WT1 promotes cell proliferation and survival; however, this ability has not been rigorously analyzed in human GBM.

METHODS

The authors tested the efficacy of 2 sequences of short hairpin RNA (shRNA) directed against WT1 in U251MG human GBM cells and found that 1 sequence was capable of stably silencing WT1 expression. They then evaluated the effect of WT1 silencing on cellular proliferation, invasion, and in vivo tumor formation.

RESULTS

Stable WT1-shRNA expression significantly decreased the proliferation of U251MG cells in vitro as demonstrated by both an adenosine 5'-triphosphate-based viability assay and tritiated thymidine uptake. Furthermore, stable WT1 silencing caused significantly slower growth after the subcutaneous inoculation of tumor cells in the flanks of athymic nude mice and was associated with an increased latency period.

CONCLUSIONS

Data in this study provide proof of the principle that downregulation of WT1 causes decreased tumorigenicity of a GBM cell line in vitro and in vivo and suggest that WT1 is a promising target for novel molecular GBM therapies, perhaps in combination with standard treatment modalities.

The alkylphospholipid perifosine induces apoptosis and p21-mediated cell cycle arrest in medulloblastoma

Medulloblastoma is the most common malignant cancer of the central nervous system in children. AKT kinases are part of a survival pathway that has been found to be significantly elevated in medulloblastoma. This pathway is a point of convergence for many growth factors and controls cellular processes that are critical for tumor cell survival and proliferation. The alkyl-phospholipid perifosine [octadecyl-(1,1-dimethyl-4-piperidylio) phosphate] is a small molecule inhibitor in clinical trials in peripheral cancers which acts as a competitive inhibitor of AKT kinases. Medulloblastoma cell cultures were used to study the effects of perifosine response in preclinical studies in vitro. Perifosine treatment led to the rapid induction of cell death in medulloblastoma cell lines, with pronounced suppression of phosphorylated AKT in a time-dependent and concentration-dependent manner. LD(50) concentrations were established using viability assays for perifosine, cisplatin, and etoposide. LD(50) treatment of medulloblastoma cells with perifosine led to the cleavage of caspase 9, caspase 7, caspase 3, and poly-ADP ribosylation protein, although caspase 8 was not detectable. Combination single-dose treatment regimens of perifosine with sublethal doses of etoposide or irradiation showed a greater than additive effect in medulloblastoma cells. Lower perifosine concentrations induced cell cycle arrest at the G(1) and G(2) cell cycle checkpoints, accompanied by increased expression of the cell cycle inhibitor p21(cip1/waf1). Treatment with p21 small interfering RNA prevented perifosine-induced cell cycle arrest. These findings indicate that perifosine, either alone or in combination with other chemotherapeutic drugs, might be an effective therapeutic agent for the treatment of medulloblastoma.

Induction of matrix metalloproteinase-1 and glioma cell motility by nitric oxide

High grade gliomas invariably recur due in a large part to tumor cells permeating normal brain in an inaccessible, diffuse manner. Previous work demonstrates that the expression of matrix metalloproteinases (MMP) contributes to this characteristic. Not only can MMPs assist a cell in traversing its environment by clearing extracellular matrix molecules, but they can also impact non-traditional downstream signals that affect a cell's ability to interact and respond to its surroundings. Contributions to the induction of MMP expression and functional significance in glioma are still under investigation. Evidence in other cancer settings indicates that nitric oxide (NO) may play a role in tumor/cell progression that can influence MMP production. Matrix metalloproteinase-1 (MMP-1), also known as interstitial collagenase, and the constitutive nitric oxide synthases (NOS) have been shown to be over-expressed in high grade gliomas. In the current study we investigated the potential involvements of NO with regard to MMP-1 and functional glioma cell movement. With the treatment of the NO donor sodium nitroprusside (SNP), there was significant induction of MMP-1 mRNA, secreted MMP-1 protein and motility of glioma cell lines within 48 h. RNA inhibition of MMP-1 through transient transfection of three MMP-1 specific siRNAs revealed a marked abrogation of the NO-mediated induction of motility. In addition, application of the NOS inhibitor N(omega)-Nitro-L-arginine methyl ester (L-NAME) impaired movement of glioma cells. These data provide evidence for a regulatory axis of high grade glioma cell movement from NO through MMP-1, with NOS inhibitor results showing promise for future pharmacologic investigation.

Increased MMP-3 and CTGF expression during lipopolysaccharide-induced dopaminergic neurodegeneration

Accumulating evidence indicates that neuroinflammation contributes significantly to progressive dopaminergic (DA) neurodegeneration in Parkinson's disease (PD). Altered matrix metalloproteinase-3 (MMP-3) expression has been reported in several neuroinflammatory paradigms; however, its relationship to inflammation-induced DA neurotoxicity has not been explored. To this end, we investigated the temporal expression pattern of MMP-3 and one of its downstream targets, connective tissue growth factor (CTGF), following lipopolysaccharide (LPS)-induced DA neurodegeneration. LPS was directly injected into the substantia nigra of male Sprague-Dawley rats. Lesion formation was confirmed with immunohistochemistry 48 h post-injection. MMP-3 and CTGF were measured by western blot 12, 24, and 48 h post-injection. In association with neurodegeneration, MMP-3 expression and activation was significantly increased 24 and 48 h after LPS injection. In addition, CTGF expression increased 5-fold at the 24h time point. The temporal changes in MMP-3 and CTGF expression corresponded to the neurodegenerative phase of this model, suggesting that these two proteins may participate in neuroinflammation-induced DA neurotoxicity.

In vitro angiogenesis by human umbilical vein endothelial cells (HUVEC) induced by three-dimensional co-culture with glioblastoma cells

Glioblastoma multiforme (GBM) is one of the most highly vascularized of all human tumors. Our objective was to characterize a 3-dimensional (3-D) in vitro angiogenesis model by co-culturing HUVEC and GBM cells, and to study the role of VEGF in mediating capillary tubule formation in this model. HUVEC-coated dextran beads were suspended in fibrin gel with human glioma cells on top. The number of sprouts and the length of the processes were measured. HUVEC can be induced to form sprouts and longer processes with lumens, in co-culture with glioma cells that secrete VEGF. Addition of exogenous VEGF enhances this effect. In the absence of glioma cells, many single HUVEC migrate away from the beads, without significant tubule formation. Hypoxia further stimulated sprout formation by 50-100%. Anti-VEGF neutralizing antibody suppressed HUVEC sprouting by 75% in co-culture with glioma cells. This 3-D in vitro co-culture system provides a robust and useful model for analysis of the major steps of glioma-induced angiogenesis.

Ectopic telomerase expression inhibits neuronal differentiation of NT2 neural progenitor cells

There is significant interest in the potential use of telomerase-immortalized cells in transplantation to replace neurons lost to neurodegenerative diseases and other central nervous system injuries. Neural progenitor cells (NPCs) transduced with human telomerase reverse transcriptase (hTERT), the catalytic component of telomerase, have the potential both to proliferate indefinitely in vitro and to respond to differentiation signals necessary for generating appropriate cells for transplantation. The purpose of this study was to evaluate the differentiation of neurons from NT2 cells, a model NPC cell line, following hTERT transduction. RT-PCR and telomerase activity data demonstrated that persistent exogenous hTERT expression significantly inhibited the differentiation of neurons from NT2 cells. Following retinoic acid induced differentiation, hTERT-NT2 cells produced only one fourth of the neurons generated by parental and vector-control cells. A differentiation-inhibiting effect of constitutive telomerase activity has not been reported previously in other hTERT-transduced progenitor cell lines, implying a unique role for telomerase in the proliferation and differentiation of NPCs that have tumorigenic potential. Elucidating the mechanism responsible for this effect may aid in understanding the potential role of telomerase activity in the tumorigenicity of NPCs, as well as in optimizing the production of safe, telomerase-engineered, transplantable neurons.

Matrix metalloproteinase-3 expression profile differentiates adaptive and maladaptive synaptic plasticity induced by traumatic brain injury

The interaction between extracellular matrix (ECM) and regulatory matrix metalloproteinases (MMPs) is important in establishing and maintaining synaptic connectivity. By using fluid percussion traumatic brain injury (TBI) and combined TBI and bilateral entorhinal cortical lesion (TBI + BEC), we previously demonstrated that hippocampal stromelysin-1 (MMP-3) expression and activity increased during synaptic plasticity. We now report a temporal analysis of MMP-3 protein and mRNA response to TBI during both degenerative (2 day) and regenerative (7, 15 day) phases of reactive synaptogenesis. MMP-3 expression during successful synaptic reorganization (following unilateral entorhinal cortical lesion; UEC) was compared with MMP-3 expression when normal synaptogenesis fails (after combined TBI + BEC insult). Increased expression of MMP-3 protein and message was observed in both models at 2 days postinjury, and immuohistochemical (IHC) colocalization suggested that reactive astrocytes contribute to that increase. By 7 days postinjury, model differences in MMP-3 were observed. UEC MMP-3 mRNA was equivalent to control, and MMP-3 protein was reduced within the deafferented region. In contrast, enzyme mRNA remained elevated in the maladaptive TBI + BEC model, accompanied by persistent cellular labeling of MMP-3 protein. At 15 days survival, MMP-3 mRNA was normalized in each model, but enzyme protein remained higher than paired controls. When TBI + BEC recovery was enhanced by the N-methyl-D-aspartate antagonist MK-801, 7-day MMP-3 mRNA was significantly reduced. Similarly, MMP inhibition with FN-439 reduced the persistent spatial learning deficits associated with TBI + BEC insult. These results suggest that MMP-3 might differentially affect the sequential phases of reactive synaptogenesis and exhibit an altered pattern when recovery is perturbed.

Isolation of neuronal progenitor cells from the adult human neocortex

BACKGROUND

The reliability of harvesting neuronal progenitor cells (NPCs) from the adult human neocortex has not been established, with respect to preparing autologous cell cultures for transplantation in stroke and traumatic brain injured patients.

METHOD

Enriched NPC cultures have been generated from nonneurogenic regions of the adult rodent brain by buoyancy-dependent fractionation, but the feasibility of using such a method to isolate NPCs from the adult human cortex has not been reported previously. To determine if a starter population of human adult cortical NPCs could be isolated for in vitro expansion using this method, tissue samples from five patients undergoing cortical resection for either epilepsy or trauma were assayed.

FINDINGS

Cultured cells generated from all patients predominately expressed both the NPC marker nestin and neuron-specific beta-tubulin III. The presence of NPCs was verified by in vitro BrdU/beta-tubulin III co-labeling and increasing beta-tubulin expression in differentiating conditions. Despite the formation of aggregates in monolayer culture, cell proliferation as measured by BrdU incorporation was not as prevalent as that reported from rodent cultures generated by this protocol.

CONCLUSIONS

NPCs isolated from the adult human neocortex using this method expressed beta-tubulin III in larger percentages than has been previously reported for NPCs isolated using other methods. As such, these data suggest the possibility of culturing dividing neuroblasts from the adult neocortex for further manipulation as transplantable cells.

Association of a single nucleotide polymorphism in the matrix metalloproteinase-1 promoter with glioblastoma

A key feature in the malignant behavior of glioblastoma is the tendency to invade host brain tissue surrounding the primary tumor site. Several members of the matrix metalloproteinase family are thought to contribute to this invasive capacity. A single nucleotide polymorphism has been described in the matrix metalloproteinase-1 (MMP-1) promoter that consists of either the presence or absence of a guanine nucleotide at position -1607. The presence of the guanine base creates a functional binding site for members of the ETS family of transcription factors and has been shown to increase MMP-1 transcription. The purpose of our study was to characterize this polymorphism in human glioblastoma. Promoter genotyping was performed on brain tumor tissue obtained from 81 patients and compared to 57 healthy individuals. The 2G/2G genotype is more prevalent in glioblastoma tissue compared to healthy individuals (p = 0.01). mRNA and protein expression were measured in a subset of brain tumor and normal brain tissue samples. MMP-1 protein levels are significantly higher in glioblastoma tissue compared to normal brain (p = 0.001). Electromobility shift assays and promoter assays were performed to assess binding capability and transcriptional activity, respectively. Proteins present in glioma cell lines can specifically bind the 2G promoter probe. MMP-1 transcription is significantly higher in cells transfected with the 2G promoter when compared to cells transfected with the 1G promoter (p<0.02). This polymorphism may provide a mechanism for increased expression of MMP-1 in malignant gliomas via elevation of MMP-1 mRNA transcription and may underlie the invasive phenotype.

Heterotypic neuronal differentiation of adult subependymal zone neuronal progenitor cells transplanted to the adult hippocampus

Neuronal progenitor cells (NPCs) residing in the adult subependymal zone (SEZ) are a potential source of expandable cells for autologous transplantation to replace neurons lost in multiple types of brain injury. To characterize the capacity of these cells for neuronal differentiation in a mature ectopic environment, NPCs expanded from the SEZ of adult rats were transplanted to the adult dentate gyrus. Cultures comprised a heterogeneous population of proliferating cells, which expressed nestin (47%) and GFAP (37%), with many cells expressing both progenitor cell markers (31%). In grafts of undifferentiated cells, as well as in grafts of cells that were induced to differentiate in vitro with retinoic acid, 35% of the transplanted SEZ-derived cells exhibited immunohistochemical and morphological features characteristic of hippocampal granule cell neurons. These novel results indicate that in vitro expanded adult SEZ NPCs are capable of heterotypic neuronal differentiation in a neurogenic region of the adult brain.

Elevation of hippocampal MMP-3 expression and activity during trauma-induced synaptogenesis

The matrix metalloproteinase (MMP) enzyme family contributes to the regulation of a variety of brain extracellular matrix molecules. In order to assess their role in synaptic plasticity following traumatic brain injury (TBI), we compared expression of stromelysin-1 (MMP-3) protein and mRNA in two rodent models of TBI exhibiting different levels of recovery: adaptive synaptic plasticity following central fluid percussion injury and maladaptive synaptic plasticity generated by combined TBI and bilateral entorhinal cortical lesion (TBI + BEC). We sampled the hippocampus at 7 days postinjury, targeting a selectively vulnerable brain region and a survival interval exhibiting rapid synaptogenesis. We report elevated expression of hippocampal MMP-3 mRNA and protein after TBI. MMP-3 immunohistochemical staining showed increased protein levels relative to sham-injured controls, primarily localized to cell bodies within the deafferented dendritic laminae. Injury-related differences in MMP-3 protein were also observed. TBI alone elevated MMP-3 immunobinding over the stratum lacunosum moleculare (SLM), inner molecular layer and hilus, while TBI + BEC generated more robust increases in MMP-3 reactivity within the deafferented SLM and dentate molecular layer (DML). Double labeling with GFAP confirmed the presence of MMP-3 within reactive astrocytes induced by each injury model. Semi-quantitative RT-PCR revealed that MMP-3 mRNA also increased after each injury, however, the combined insult induced a much greater elevation than fluid percussion alone: 1.9-fold vs. 79%, respectively. In the TBI + BEC model, MMP-3 up-regulation was spatio-temporally correlated with increased enzyme activity, an effect which was attenuated with the neuroprotective compound MK-801. These results show that distinct pathological conditions elicited by TBI can differentially affect MMP-3 expression during reactive synaptic plasticity. Notably, these effects are both transcriptional and translational and are correlated with functionally active enzyme.

Cell replacement efforts to repair neuronal injury: a potential paradigm for the treatment of Parkinson's disease

Much has been learned from recent clinical trials exploring cell transplantation as a means to treat Parkinson's disease. Additionally, much information is being gathered in the science arena on the method of cultivation and expansion of neural stem/progenitor cells as well as catheter and cell delivery methodology. Cell replacement remains a potential promising treatment option for Parkinson's disease, however several obstacles must be overcome in order to achieve successful outcomes in future clinical trials. Hurdles include but are not limited to the identification of a reliable method of cultivation and expansion of neural stem/progenitor cells, the optimization of methods for cell delivery and the optimization of location or locations for transplantation.

Grafts of adult subependymal zone neuronal progenitor cells rescue hemiparkinsonian behavioral decline

Neuronal progenitor cells (NPCs) residing in the adult subependymal zone (SEZ) are a potential source of expandable cells for autologous transplantation to treat Parkinson's Disease and other types of brain injury. We have previously demonstrated the capacity of transplanted adult SEZ NPCs for heterotypic differentiation in the hippocampus. To further characterize the therapeutic potential of these cells, NPCs expanded from the adult rat SEZ were grafted to the striatum of normal and 6-OHDA lesioned adult rats. Grafted cells were assessed for neuronal differentiation, and lesioned animals were tested for amphetamine-induced rotational asymmetry. In addition, the effect of inducing differentiation in vitro prior to transplantation was assessed. Although grafted cells survived after 2 weeks in all animals, neither striatal deafferentation nor in vitro induction of differentiation resulted in significant neuronal differentiation of transplanted cells. Grafts, however, did produce a behavioral effect. While sham animals exhibited increased rotational behavior (+67%) from 2 to 4 weeks post-lesioning, grafted animals did not (-21%). Grafted cells continued to express nestin at the survival time point, and dopamine transporter (DAT) immunoreactivity was restored in the graft body. These results suggest that although neither the normal nor the deafferented striatum alone support the neuronal differentiation of transplanted adult SEZ NPCs, grafts maintaining a progenitor phenotype may produce a therapeutic benefit.

Induction of membrane-type-1 matrix metalloproteinase by epidermal growth factor-mediated signaling in gliomas

Increased expression of membrane-type matrix metalloproteinases (MT-MMPs) has previously been reported to correlate with increasing grade of malignancy in gliomas, a relationship shared with alterations in epidermal growth factor receptor (EGFR) signaling. To investigate the possibility of a causative role for EGFR signaling in increasing MT-MMP expression and subsequent peritumoral proteolysis, we characterized glioma cell lines for expression of MT1-MMP, MT2-MMP, MT3-MMP, and MT5-MMP by Western blotting and by quantitative real-time polymerase chain reaction analysis, and for MMP-2 activity following epidermal growth factor (EGF) stimulation. EGF stimulation of glioma cell lines resulted in a 2- to 4-fold increase in MT1-MMP mRNA levels. Although there were slight differences in MT2-, MT3-, and MT5-MMP mRNA expression following EGF stimulation, none of these demonstrated an increase similar to that of MT1-MMP expression. Treatment of high-grade glioma cell lines U251MG and IPSB-18 with EGF for 24 h resulted in a several-fold increase in MT1-MMP protein (2.5- and 5.1-fold, respectively) and in cyclin D1 (2.9-fold), as compared to untreated controls. No significant increase was detected in other MT-MMPs at the protein level. Although there was no detectable increase in proMMP-2 protein, there was an increase in MMP-2 activity. Furthermore, the MT1-MMP induction by EGF was prevented by pretreatment with the EGFR-specific tyrphostin inhibitor AG1478. Similarly, treatment with the phosphatidylinositol 3-kinase inhibitor LY294002 prevented the induction of MT1-MMP protein by EGF stimulation. These compounds additionally inhibited EGF-stimulated invasion in Matrigel Transwell assays. Our results indicate that one mechanism of EGFR-mediated invasiveness in gliomas may involve the induction of MT1-MMP.

Progress in cerebral transplantation of expanded neuronal stem cells

OBJECT

Given the success and limitations of human fetal primary neural tissue transplantation, neuronal stem cells (NSCs) that can be adequately expanded in culture have been the focus of numerous attempts to develop a superior source of replacement cells for restorative neurosurgery. To clarify recent progress toward this goal, the transplantation into the adult brain of NSCs, expanded in vitro before grafting, was reviewed.

METHODS

Neuronal stem cells can be expanded from a variety of sources, including embryos, fetuses, adult bone marrow, and adult brain tissue. Recent investigations of each of these expanded stem cell types have generated a large body of information along with a great number of unanswered questions regarding the ability of these cells to replace damaged neurons. Expanded NSCs offer many advantages over their primary tissue predecessors, but also may exhibit different functional abilities as grafted cells. Because expanded NSCs will most likely ultimately replace primary tissue grafting in clinical trials, this review was undertaken to focus solely on this distinct body of work and to summarize clearly the existing preclinical data regarding the in vivo successes, limits, and unknowns of using each expanded NSC type when transplanted into the adult brain.

CONCLUSIONS

Embryonic stem cell-derived cells have demonstrated appropriate neuronal phenotypes after transplantation into nonneurogenic areas of the adult brain. Understanding the mechanisms responsible for this may lead to similar success with less studied adult neuronal progenitor cells, which offer the potential for autologous NSC transplantation with less risk of tumorigenesis.

Matrix metalloproteinase expression in the olfactory epithelium

The olfactory epithelium contains neuronal progenitor cells capable of continuous neurogenesis and is a unique model for studying neural degeneration, regeneration, axon outgrowth and recovery from injury. Matrix metalloproteinases (MMPs), and tissue inhibitors of metalloproteinases (TIMPs), have been implicated in cell turnover, development, migration, and metastatic processes. We used Western blot and immunohistochemistry to determine whether MMP-2 and associated proteins TIMP-2 and membrane type 1 matrix metalloproteinase (MT1-MMP) are present in the olfactory epithelium of mice. We found MMP-2 expression localized to the olfactory basal cells and immature neurons. After injury-induced neural degeneration, MMP-2 and MT1-MMP levels decreased while TIMP-2 levels increased. However, following 35 days of neurogenesis and cell replacement TIMP-2 and MT1-MMP returned to control levels. The results show a correlation between MMP and TIMP levels and the stages of neural degeneration, regeneration and recovery of the olfactory epithelium following injury.

Quantitative assessment of glioblastoma invasion in vivo

The aim of this study was the quantitative assessment of the time course and spatial distribution in brain of invading glioblastoma (GBM) cells using a recently described model consisting of RT2 rat GBM cells stably transfected with enhanced green fluorescent protein (eGFP) - called RT2-eGFP - and implanted in Fischer rats. Invasion throughout the brain was verified by confocal microscopy and immunocytochemical staining for eGFP. Rats were sacrificed on post-implantation days 3, 8, and time of death (TOD). First, the entire rat brain was disaggregated at each time point and viable RT2-eGFP cells were counted using flow cytometry with fluorescence as the marker. Next, 2 mm(3) samples of cortex from each of four brain quadrants (bifrontal and bioccipital) were disaggregated at each time point, with tumor cell quantification as before. Tumor cell density, averaged over the entire brain, reached a peak mid-way through its time course, leveling out by TOD. Tumor cell density within bulk tumor (BT) was greatest early in the evolution of the brain tumor, decreasing to its final value mid-way through its time course, due to necrosis. The greatest concentration of tumor cells was within BT, with up to an order of magnitude fewer cells in the periphery, while the number of brain tumor cells invading brain distant from BT remained constant from day 3 until TOD. BT size steadily increased after implantation, with an increasing portion due to central necrosis as time progressed, suggesting that this effect is an important contributor to fatality in this model. Alternatively (or additionally), accumulation of toxins elaborated by tumor cells throughout the brain starting early in the evolution of the tumor may also contribute to fatality.

Membrane-type matrix metalloproteinases (MT-MMPs): expression and function during glioma invasion

Membrane-type MMPs (MT-MMPs) constitute a growing subclass of recently identified matrix metalloproteinases (MMPs). In addition to the highly conserved MMP functional domains, the MT-MMPs have additional insertion sequences (IS) that confer unique functional roles. While most of the MMPs are secreted, the MT-MMPs are membrane associated and a number of these have cytoplasmic domains which may be important in cellular signaling. This membrane localization leads to focal areas of receptor recruitment and subsequent activity, thereby enhancing pericellular proteolysis in specific areas of contact within the brain interstitium. MT1-MMP is the best-characterized MT-MMP, the measure against which subsequently cloned homologues are compared. MT1-MMP activates proMMP2 via its interaction with TIMP2, which serves as an intermolecular bridge for proMMP2 binding to MT-MMPs. In addition to activation of proMMP2, MT-MMPs display intrinsic proteolytic activity towards extracellular matrix molecules (ECM), which is independent of MMP2 activation. The increased expression levels of several members of the MMP family have been shown to correlate with high-grade gliomas, including MTI-MMP. Despite improvements in the diagnosis and treatment of patients with glial tumors, they remain the most common and least curable brain cancer in adults. The ability of glioma cells to infiltrate surrounding brain tissue, and ultimately escape current therapeutic modalities, could potentially be minimized using anti-invasive therapies. Proteolysis is a necessary part of the invasion process, within which the MT-MMPs appear to play a central role. The development of pharmaceutical approaches that target expression and regulation of MT-MMPs may prove beneficial in targeting invading glioma cells.

The role of matrix metalloproteinase genes in glioma invasion: co-dependent and interactive proteolysis

Matrix metalloproteinases (MMPs) are cation-dependent endopeptidases which have been implicated in the malignancy of gliomas. It is thought that the MMPs play a critical role in both metastasis and angiogenesis, and that interference with proteases might therefore deter local tumor dissemination and neovascularization. However, the attempt to control tumor-associated proteolysis will rely on better definition of the normal tissue function of MMPs, an area of study still in its infancy in the central nervous system (CNS). Understanding the role of MMP-mediated proteolysis in the brain relies heavily on advances in other areas of molecular neuroscience, most notably an understanding of extracellular matrix (ECM) composition and the function of cell adhesion molecules such as integrins, which communicate knowledge of ECM composition intracellularly. Recently, protease expression and function has been shown to be strongly influenced by the functional state and signaling properties of integrins. Here we review MMP function and expression in gliomas and present examples of MMP profiling studies in glioma tissues and cell lines by RT-PCR and Western blotting. Co-expression of MMPs and certain integrins substantiates the gathering evidence of a functional intersection between the two, and inhibition studies using recombinant TIMP-1 and integrin antisera demonstrate significant inhibition of glioma invasion in vitro. Use of promising new therapeutic compounds with anti-MMP and anti-invasion effects are discussed. These data underline the importance of functional interaction of MMPs with accessory proteins such as integrins during invasion, and the need for further studies to elucidate the molecular underpinnings of this process.

Membrane-type matrix metalloproteinases (MT-MMPs): expression and function during glioma invasion

Membrane-type MMPs (MT-MMPs) constitute a growing subclass of recently identified matrix metalloproteinases (MMPs). In addition to the highly conserved MMP functional domains, the MT-MMPs have additional insertion sequences (IS) that confer unique functional roles. While most of the MMPs are secreted, the MT-MMPs are membrane associated and a number of these have cytoplasmic domains which may be important in cellular signaling. This membrane localization leads to focal areas of receptor recruitment and subsequent activity, thereby enhancing pericellular proteolysis in specific areas of contact within the brain interstitium. MT1-MMP is the best-characterized MT-MMP, the measure against which subsequently cloned homologues are compared. MT1-MMP activates proMMP2 via its interaction with TIMP2, which serves as an intermolecular bridge for proMMP2 binding to MT-MMPs. In addition to activation of proMMP2, MT-MMPs display intrinsic proteolytic activity towards extracellular matrix molecules (ECM), which is independent of MMP2 activation. The increased expression levels of several members of the MMP family have been shown to correlate with high-grade gliomas, including MTI-MMP. Despite improvements in the diagnosis and treatment of patients with glial tumors, they remain the most common and least curable brain cancer in adults. The ability of glioma cells to infiltrate surrounding brain tissue, and ultimately escape current therapeutic modalities, could potentially be minimized using anti-invasive therapies. Proteolysis is a necessary part of the invasion process, within which the MT-MMPs appear to play a central role. The development of pharmaceutical approaches that target expression and regulation of MT-MMPs may prove beneficial in targeting invading glioma cells.