Brain Of Nude Rats Research Articles

Optimizing Glioma Detection Using an EGFR-Targeted Fluorescent Affibody.

Since many types of cancers overexpress EGFR, this surface receptor has been used as a target for therapy or diagnosis of malignant disease. Uptake kinetics of EGFR-targeted fluorescent Affibody (ABY-029) were studied with a view toward optimizing efficacy of tumor detection in a glioma as a function of both delivered dose and concurrent administration of unlabeled cetuximab (an EGFR antagonist). U251 glioma cells were inoculated in brain of nude rats, and the fluorescence from each brain was analyzed after the administration of ABY-029. Although cetuximab was able to systematically block ABY-029 binding to EGFR in a dose-dependent manner in cell culture, no influence on the tumor-to-normal brain contrast was seen when unlabeled cetuximab was administered prior to ABY-029. Ex vivo imaging of ABY-029 fluorescence showed increasing values of the tumor-to-normal brain ratio with an increasing injected dose. A saturation value was obtained at a dose of 245 μg kg-1 which represents a 10-fold increase over a "microdose" value. According to FDA, the microdose of protein products is considered ≤30 nanomoles due to its difference in molecular weight as compared to synthetic drugs. This observation indicates that glioma detection will be optimal if the ABY-029 dose exceeds the "microdose" value.

Engraftment of Human Glioblastoma Cells in Immunocompetent Rats through Acquired Immunosuppression.

Transplantation of glioblastoma patient biopsy spheroids to the brain of T cell-compromised Rowett (nude) rats has been established as a representative animal model for human GBMs, with a tumor take rate close to 100%. In immunocompetent littermates however, primary human GBM tissue is invariably rejected. Here we show that after repeated passaging cycles in nude rats, human GBM spheroids are enabled to grow in the brain of immunocompetent rats. In case of engraftment, xenografts in immunocompetent rats grow progressively and host leukocytes fail to enter the tumor bed, similar to what is seen in nude animals. In contrast, rejection is associated with massive infiltration of the tumor bed by leukocytes, predominantly ED1+ microglia/macrophages, CD4+ T helper cells and CD8+ effector cells, and correlates with elevated serum levels of pro-inflammatory cytokines IL-1β, IL-18 and TNF-α. We observed that in nude rat brains, an adaptation to the host occurs after several in vivo passaging cycles, characterized by striking attenuation of microglial infiltration. Furthermore, tumor-derived chemokines that promote leukocyte migration and their entry into the CNS such as CXCL-10 and CXCL-12 are down-regulated, and the levels of TGF-β2 increase. We propose that through serial in vivo passaging in nude rats, human GBM cells learn to avoid and or/ suppress host immunity. Such adapted GBM cells are in turn able to engraft in immunocompetent rats without signs of an inflammatory response.

AI-14 * THE ANTI ANGIOGENIC AND INVASIVE EFFECTS OF AN INTEGRIN INHIBITOR AGAINST BEVACIZUMAB-INDUCED INVASIVE GLIOMA

Glioblastoma is known to secrete high levels of vascular endothelial growth factor (VEGF), and clinical studies with bevacizumab, a monoclonal antibody to VEGF, have demonstrated convincing therapeutic benefits in patients with glioblastoma. However, its induction of invasive proliferation has also been reported. We examined the effects of treatment with cilengitide, an integrin inhibitor, on bevacizumab-induced invasive changes in glioma. U87ΔEGFR cells were stereotactically injected into the brain of nude mice or rats. Five days after tumor cell implantation, cilengitide and bevacizumab were administered intraperitoneally three times a week. At 18 days after tumor implantation, the brains were removed and observed histopathologically. We analyzed the three following groups: untreated, treated with bevacizumab, and treated with a combination of bevacizumab and cilengitide. Next, RNA was extracted from orthotopic U87ΔEGFR brain tumor models. The bevacizumab and cilengitide combination group was compared to the bevacizumab monotherapy group using microarray analysis. Bevacizumab treatment led to increased cell invasion in spite of decreased angiogenesis. When the rats were treated with a combination of bevacizumab and cilengitide, the depth of tumor invasion was significantly less than with only bevacizumab. Pathway analysis using the microarray data demonstrated the inhibition of invasion-associated genes such as the integrin-mediated cell adhesion pathway in the bevacizumab and cilengitide combination group. This study showed that that the combination of bevacizumab with cilengitide exerted its anti-invasive effect by suppressing the integrin-mediated cell adhesion pathway. The elucidation of this mechanism might contribute to the treatment of bevacizumab-refractory glioma.

Integrin Inhibitor Suppresses Bevacizumab-Induced Glioma Invasion

Glioblastoma is known to secrete high levels of vascular endothelial growth factor (VEGF), and clinical studies with bevacizumab, a monoclonal antibody to VEGF, have demonstrated convincing therapeutic benefits in glioblastoma patients. However, its induction of invasive proliferation has also been reported. We examined the effects of treatment with cilengitide, an integrin inhibitor, on bevacizumab-induced invasive changes in glioma. U87ΔEGFR cells were stereotactically injected into the brain of nude mice or rats. Five days after tumor implantation, cilengitide and bevacizumab were administered intraperitoneally three times a week. At 18 days after tumor implantation, the brains were removed and observed histopathologically. Next, the bevacizumab and cilengitide combination group was compared to the bevacizumab monotherapy group using microarray analysis. Bevacizumab treatment led to increased cell invasion in spite of decreased angiogenesis. When the rats were treated with a combination of bevacizumab and cilengitide, the depth of tumor invasion was significantly less than with only bevacizumab. Pathway analysis demonstrated the inhibition of invasion-associated genes such as the integrin-mediated cell adhesion pathway in the combination group. This study showed that the combination of bevacizumab with cilengitide exerted its anti-invasive effect. The elucidation of this mechanism might contribute to the treatment of bevacizumab-refractory glioma.

Abstract 1590: Sulfasalazine sensitizes glioblastoma cells to radiation treatment.

Abstract Glioblastoma (GBM) is a lethal cancer with a limited response to ionizing radiation. Recent studies suggest that Sulfasalazine (SAS), a drug used to treat inflammatory bowel disease, inhibits the Xc− antiporter system in glioma cells, thereby blocking their uptake of cystein. Since the availability of cystein is a rate limiting step in intracellular antioxidant production, we wanted to investigate whether sulfasalazine sensitizes glioma cells to radiation. Expression of xCT, the catalytic subunit of system Xc−, was found in 30 patient GBM biopsies. SAS effect on glioma cell growth was investigated using an electric cell substrate impedance sensing (ECIS) instrument. All glioma cell lines showed altered growth curves in response to SAS treatment. To assess the effect of blocking the antiporter, intracellular levels of the antioxidant glutathione were measured. With increasing doses of SAS, glutathione levels decreased in a dose response manner. In addition, cysteine was added to the medium to see if the toxic effects of SAS could be counteracted. Furthermore, accumulation of reactive oxygen species upon SAS treatment was measured. Glioma cells were also treated with escalating doses of SAS, alone or in combination with radiation (8 Gy). The presence of double stranded breaks increased markedly in the irradiated samples and also somewhat with increasing doses with SAS. In addition, cell death, viability and clonogenicity were investigated using live/dead staining, the MTS assay and the clonogenic assay. All treatment groups exhibited increased rates of cell death compared to untreated controls. A combination of SAS and radiation resulted in higher levels of cell death, than radiation or SAS administered alone. Furthermore we continued with implantation of human GBMs into the brain of Nude rats. These animals were treated with Gamma Knife Radiosurgery alone or in combination with SAS. SAS were administered as a pre-treatment for three days before Radiosurgery. The rats receiving the combination treatment lived significantly longer compared to either treatment alone. Interestingly, the animals only receiving pre-treatment with SAS for three days lived significantly longer compared to the untreated controls, although this was not statistically significant. We are currently preparing a clinical trial for patients with GBM recurrences combining pre-treatment with Sulfasalazine and Gamma Knife Radiosurgery. Citation Format: Linda Sleire, Bente S. Skeie, Inger A. Netland, Jan Heggdal, Paal-Henning Pedersen, Per Ø. Enger. Sulfasalazine sensitizes glioblastoma cells to radiation treatment. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1590. doi:10.1158/1538-7445.AM2013-1590

Focused Ultrasound Delivers Targeted Immune Cells to Metastatic Brain Tumors

Natural killer (NK) cells are cytotoxic lymphocytes involved in innate immunity. NK-92, a human NK cell line, may be targeted to tumor-associated antigens in solid malignancies where it exhibits antitumor efficacy, but its clinical utility for treating brain tumors is limited by an inability to cross the blood-brain barrier (BBB). We investigated the potential for focused ultrasound (FUS) to deliver targeted NK-92 cells to the brain using a model of metastatic breast cancer. HER2-expressing human breast tumor cells were implanted into the brain of nude rats. The NK-92-scFv(FRP5)-zeta cell line expressing a chimeric HER2 antigen receptor was transfected with superparamagnetic iron oxide nanoparticles before intravenous injection, before and following BBB disruption using focused ultrasound (551.5 kHz focused transducer, 0.33 MPa average peak rarefaction pressure) in the presence of a microbubble contrast agent. Baseline and posttreatment 1.5T and 7T MR imaging was done, and histology used to identify NK-92 cells post-mortem. Contrast-enhanced MRI showed reproducible and consistent BBB disruption. 7T MR images obtained at 16 hours posttreatment revealed a significant reduction in signal indicating the presence of iron-loaded NK-92 cells at the tumor site. The average ratio of NK-92 to tumor cells was 1:100 when NK cells were present in the vasculature at the time of sonication, versus 2:1,000 and 1:1,000 when delivered after sonication and without BBB disruption, respectively. Our results offer a preclinical proof-of-concept that FUS can improve the targeting of immune cell therapy of brain metastases.

Abstract B84: Activated c-Src enhances hypoxia in human glioblastoma multiforme and promotes tumor angiogenesis

Abstract Exhibiting substantial vascularization and propensity to infiltrate surrounding brain tissue, glioblastoma multiforme (GBM) is the most aggressive primary brain tumor. Even with aggressive intervention afflicted individuals uniformly receive poor prognosis. Growth factor receptor tyrosine kinases (RTKs) are frequently amplified, overexpressed, and constitutively activated in malignant gliomas, and because targeting these molecules has produced promising results in the treatment of several human neoplasms, RTKs are emerging as increasingly viable targets in effective treatment of GBM. Functional ambiguity between normal and constitutively activated RTK signalling compounds the challenges of identifying suitable targets, however. Likewise, the functions of many reported downstream signalling molecules, namely Src family non-receptor tyrosine kinases (SFKs), remain cryptic. Our lab has previously developed a clinically relevant in vivo model that reliably maintains the genomic profiles of corresponding patient tumors, and employing this model, we are able to accurately investigate mechanisms of RTK signalling in human GBM. Ongoing studies suggest that tumor overexpression and activation of the epidermal growth factor receptor (EGFR) promotes the invasive phenotype in human GBM potentially via c-Src dependent signal transduction. In fact, we have observed SFK activation downstream of EGFR. To further investigate this, we implanted GBM patient tumor cells from two individuals with distinct EGFR protein expression, tumor phenotype, and c-Src activity into the brains of nude rats. Minimally expressing EGFR tumor cells from a patient displaying an angiogenic in vivo phenotype were transduced to stably overexpress activated c-Src. Likewise, EGFR-overexpressing tumor cells from a patient displaying an invasive, non angiogenic in vivo phenotype were transduced to stably overexpress kinase-inactive-dominant-negative c-Src. To our surprise, compared with corresponding xenograft control tumors, xenograft tumors overexpressing constitutively activated c-Src showed substantially increased contrast enhancement on MRI, enhanced histological features of angiogenesis, and revealed marked increases in molecular markers of tumor hypoxia and angiogenesis on western blot. Meanwhile, compared with corresponding xenograft control tumors, xenograft tumors overexpressing kinase-inactive-dominant-negative c-Src did not show increased contrast enhancement on MRI, showed no histological evidence of angiogenesis, and maintained a non-angiogenic molecular profile on western blot. We hereby report that activation of the SFK c-Src enhances tumor hypoxia, promotes the aggressive angiogenic tumor phenotype, and is subsequently not likely a primary downstream SFK substrate of overexpressed EGFR in human GBM. Overexpression of wild type EGFR may, instead, signal through a different SFK to promote the invasive phenotype. These results suggest that, more so than invasion, c-Src activation may be a valuable diagnostic and prognostic indicator of malignant progression. Furthermore, these results indicate that c-Src activation may be a strategic target in the therapeutic intervention of human malignant glioma. Citation Format: Eskil Eskilsson, Krishna M. Talasila, Gro V. Røsland, Lina Leiss, Narve Brekkå, Per Øystein Sakariassen, Per Øyvind Enger, Rolf Bjerkvig, Hrvoje Miletic. Activated c-Src enhances hypoxia in human glioblastoma multiforme and promotes tumor angiogenesis. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Invasion and Metastasis; Jan 20-23, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;73(3 Suppl):Abstract nr B84.

Analysis of the Growth Dynamics of Angiogenesis-Dependent and -Independent Experimental Glioblastomas by Multimodal Small-Animal PET and MRI

The hypothesis of this study was that distinct experimental glioblastoma phenotypes resembling human disease can be noninvasively distinguished at various disease stages by imaging in vivo. Cultured spheroids from 2 human glioblastomas were implanted into the brains of nude rats. Glioblastoma growth dynamics were followed by PET using (18)F-FDG, (11)C-methyl-l-methionine ((11)C-MET), and 3'-deoxy-3'-(18)F-fluorothymidine ((18)F-FLT) and by MRI at 3-6 wk after implantation. For image validation, parameters were coregistered with immunohistochemical analysis. Two tumor phenotypes (angiogenic and infiltrative) were obtained. The angiogenic phenotype showed high uptake of (11)C-MET and (18)F-FLT and relatively low uptake of (18)F-FDG. (11)C-MET was an early indicator of vessel remodeling and tumor proliferation. (18)F-FLT uptake correlated to positive Ki67 staining at 6 wk. T1- and T2-weighted MR images displayed clear tumor delineation with strong gadolinium enhancement at 6 wk. The infiltrative phenotype did not accumulate (11)C-MET and (18)F-FLT and impaired the (18)F-FDG uptake. In contrast, the Ki67 index showed a high proliferation rate. The extent of the infiltrative tumors could be observed by MRI but with low contrast. For angiogenic glioblastomas, noninvasive assessment of tumor activity corresponds well to immunohistochemical markers, and (11)C-MET was more sensitive than (18)F-FLT at detecting early tumor development. In contrast, infiltrative glioblastoma growth in the absence of blood-brain barrier breakdown is difficult to noninvasively follow by existing imaging techniques, and a negative (18)F-FLT PET result does not exclude the presence of proliferating glioma tissue. The angiogenic model may serve as an advanced system to study imaging-guided antiangiogenic and antiproliferative therapies.

An Off-Target Nucleostemin RNAi Inhibits Growth in Human Glioblastoma-Derived Cancer Stem Cells

Glioblastomas (GBM) may contain a variable proportion of active cancer stem cells (CSCs) capable of self-renewal, of aggregating into CD133+ neurospheres, and to develop intracranial tumors that phenocopy the original ones. We hypothesized that nucleostemin may contribute to cancer stem cell biology as these cells share characteristics with normal stem cells. Here we report that nucleostemin is expressed in GBM-CSCs isolated from patient samples, and that its expression, conversely to what it has been described for ordinary stem cells, does not disappear when cells are differentiated. The significance of nucleostemin expression in CSCs was addressed by targeting the corresponding mRNA using lentivirally transduced short hairpin RNA (shRNA). In doing so, we found an off-target nucleostemin RNAi (shRNA22) that abolishes proliferation and induces apoptosis in GBM-CSCs. Furthermore, in the presence of shRNA22, GBM-CSCs failed to form neurospheres in vitro or grow on soft agar. When these cells are xenotransplanted into the brains of nude rats, tumor development is significantly delayed. Attempts were made to identify the primary target/s of shRNA22, suggesting a transcription factor involved in one of the MAP-kinases signaling-pathways or multiple targets. The use of this shRNA may contribute to develop new therapeutic approaches for this incurable type of brain tumor.

Toxicity and delivery methods for the linamarase/linamarin/glucose oxidase system, when used against human glioma tumors implanted in the brain of nude rats

Glioblastoma multiforme (GBM) is one of the deadliest forms of cancer, with an average survival time of approximately 1 year despite aggressive surgery, radiotherapy and chemotherapy. Here, we report a preclinical study by which the two main energy pathways of the tumor cells, oxidative phosphorylation and aerobic glycolysis, are simultaneously disrupted. The therapy is based on a plant gene encoding a β-glucosidase, linamarase ( lis), which react with the substrate linamarin (lin) producing cyanide. We also use glucose oxidase (GO) to enhance oxidative stress and to induce cell death in the tumor. To test in vivo this suicide gene therapy system ( lis/lin/GO), we used an orthotopic model of the human U87MG glioma cells, genetically modified to express the lis gene, and stereotactically implanted into the brains of nude rats ( rnu/ rnu). Despite its genetic condition, 6% of the animals immunorejected the xenotransplanted cells giving false curative results. We tried several delivery methods with limited success. The therapeutic cocktail, at dosages that perhaps eliminated the brain tumors, is too toxic for the animal causing its premature death.

Quantitative T2* imaging of metastatic human breast cancer to brain in the nude rat at 3 T

This study uses quantitative T(2)* imaging to track ferumoxides--protamine sulfate (FEPro)-labeled MDA-MB-231BR-Luc (231BRL) human breast cancer cells that metastasize to the nude rat brain. Four cohorts of nude rats were injected intracardially with FEPro-labeled, unlabeled or tumor necrosis factor-related apoptosis-inducing ligand(TRAIL)-treated (to induce apoptosis) 231BRL cells, or saline, in order to develop metastatic breast cancer in the brain. The heads of the rats were imaged serially over 3-4 weeks using gradient multi-echo and turbo spin-echo pulse sequences at 3 T with a solenoid receive-only 4-cm-diameter coil. Quantitative T(2)* maps of the whole brain were obtained by the application of single-exponential fitting to the signal intensity of T(2)* images, and the distribution of T(2)* values in brain voxels was calculated. MRI findings were correlated with Prussian blue staining and immunohistochemical staining for iron in breast cancer and macrophages. Quantitative analysis of T(2)* from brain voxels demonstrated a significant shift to lower values following the intracardiac injection of FEPro-labeled 231BRL cells, relative to animals receiving unlabeled cells, apoptotic cells or saline. Quartile analysis based on the T(2)* distribution obtained from brain voxels demonstrated significant differences (p < 0.0083) in the number of voxels with T(2)* values in the ranges 10-35 ms (Q1), 36-60 ms (Q2) and 61-86 ms (Q3) from 1 day to 3 weeks post-infusion of labeled 231BRL cells, compared with baseline scans. There were no significant differences in the distribution of T(2)* obtained from serial MRI in rats receiving unlabeled or TRAIL-treated cells or saline. Histologic analysis demonstrated isolated Prussian blue-positive breast cancer cells scattered in the brains of rats receiving labeled cells, relative to animals receiving unlabeled or apoptotic cells. Quantitative T(2)* analysis of FEPro-labeled metastasized cancer cells was possible even after the hypointense voxels were no longer visible on T(2)*-weighted images.

Abstract 1512: The linamarase/linamarin/glucose oxidase cocktail cures human gliomas in rats

Abstract Glioblastoma multiforme (GBM) is one of the dedliest forms of cancer, with an average survival time of approximately one year despite aggressive surgery, radiotherapy and chemotherapy. We will report a therapeutic procedure with potential clinical utility, by which the two main energy pathways of the tumor cells, oxidative phosphorylation and aerobic glycolysis, are simultaneously disrupted. First, the neoplastic cells must receive the plant linamarase gene (LI), which mediates the transformation of linamarin (LIN) into cyanide, glucose and acetone. Shortly after, we administer a systemic treatment with both linamarin and glucose oxidase (GOD) for 7 days. This creates a synergistic effect by which the neoplasm collapses in a few days. Autophagy is the cellular death mechanism involved in the eradication of the tumor. One hundred percent of the tumors disappear and neither relapse nor side effects are manifested. This therapeutic procedure also destroys the highly metastatic stem cell population from the human glioblastoma implants, thus preventing recurrence of the disease. This simple treatment is the first that can cure in a few days human brain tumors xenotransplanted into the brain of nude rats. 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 1512.

Abstract B20: Acetaminophen enhances the cytotoxicity of cisplatin in vitro and in a subcutaneous tumor xenograft model of human ovarian carcinoma

Abstract Background: High dose acetaminophen causes hepatotoxicity by depleting glutathione and increasing production of toxic metabolites. The objective of this study was to examine if these mechanisms of acetaminophen can enhance the cytotoxicity of cisplatin in human ovarian cancer cells both in vitro and in vivo. Methods: In vitro studies (glutathione concentration, cell viability and immunoblotting assays) were performed using SKOV3 human ovarian cancer cells cultured in combinations of acetaminophen and cisplatin. For the tumor model, female nude rats were pre-treated with cyclophosphamide (i.p. 100 mg/kg) one day prior to subcutaneous inoculation of SKOV3 cells with matrigel on the left flank. At 7 days after implantation, rats were randomly assigned into vehicle, cisplatin, and acetaminophen plus cisplatin treatment groups (n=3–5 per group). Subcutaneous tumor volume was measured by dial caliper. Acetaminophen pharmacology and the toxicity of treatments were monitored. Results: In vitro, acetaminophen decreased SKOV3 cellular glutathione level by approximately 30% over 2 hr time frame. Acetaminophen combined with cisplatin decreased cell growth and viability and enhanced apoptosis compared to cisplatin alone in vitro. In vivo, high dose acetaminophen showed uniform tissue distribution, but only decreased glutathione in the liver but not in the serum, brain, or subcutaneous tumor of nude rats. Acetaminophen pretreatment 2–4 hr prior to cisplatin enhanced cisplatin chemotherapeutic effect as determined by a reduction in subcutaneous tumor volume by 15–25% (55–85% vs 40–60%). Serum BUN and creatinine levels were elevated by the combination of acetaminophen with cisplatin treatment when compared to cisplatin alone (48.2±10.9 vs 24.4±4.1 mg/dL; 0.65±0.06 vs 0.30±0.04 mg/dL; p&amp;lt;0.01). Conclusions: Our results suggested that a chemotherapeutic regimen containing both high dose acetaminophen and cisplatin could be applied not only in hepatic tumors but also in ovarian or other tumor malignancies as a potentially promising approach for pre-clinical trial. Citation Information: Cancer Res 2009;69(23 Suppl):B20.

ITRAQ-based Proteomics Profiling Reveals Increased Metabolic Activity and Cellular Cross-talk in Angiogenic Compared with Invasive Glioblastoma Phenotype

Malignant gliomas (glioblastoma multiforme) have a poor prognosis with an average patient survival under current treatment regimens ranging between 12 and 14 months. The tumors are characterized by rapid cell growth, extensive neovascularization, and diffuse cellular infiltration of normal brain structures. We have developed a human glioblastoma xenograft model in nude rats that is characterized by a highly infiltrative non-angiogenic phenotype. Upon serial transplantation this phenotype will develop into a highly angiogenic tumor. Thus, we have developed an animal model where we are able to establish two characteristic tumor phenotypes that define human glioblastoma (i.e. diffuse infiltration and high neovascularization). Here we aimed at identifying potential biomarkers expressed by the non-angiogenic and the angiogenic phenotypes and elucidating the molecular pathways involved in the switch from invasive to angiogenic growth. Focusing on membrane-associated proteins, we profiled protein expression during the progression from an invasive to an angiogenic phenotype by analyzing serially transplanted glioma xenografts in rats. Applying isobaric peptide tagging chemistry (iTRAQ) combined with two-dimensional LC and MALDI-TOF/TOF mass spectrometry, we were able to identify several thousand proteins in membrane-enriched fractions of which 1460 were extracted as quantifiable proteins (isoform- and species-specific and present in more than one sample). Known and novel candidate proteins were identified that characterize the switch from a non-angiogenic to a highly angiogenic phenotype. The robustness of the data was corroborated by extensive bioinformatics analysis and by validation of selected proteins on tissue microarrays from xenograft and clinical gliomas. The data point to enhanced intercellular cross-talk and metabolic activity adopted by tumor cells in the angiogenic compared with the non-angiogenic phenotype. In conclusion, we describe molecular profiles that reflect the change from an invasive to an angiogenic brain tumor phenotype. The identified proteins could be further exploited as biomarkers or therapeutic targets for malignant gliomas.

Expression of CYP4A1 in U251 Human Glioma Cell Induces Hyperproliferative Phenotype in Vitro and Rapidly Growing Tumors in Vivo

Exogenous 20-hydroxyeicosatetraenoic acid (20-HETE) increases the growth of human glioma cells in vitro. However, glioma cells in culture show negligible 20-HETE synthesis. We examined whether inducing the expression of a 20-HETE synthase in a human glioma U251 cell line would increase proliferation. U251 cells transfected with CYP4A1 cDNA (termed U251 O) increased the formation of 20-HETE from less than 1 to over 60 pmol/min/mg proteins and increased their proliferation rate by 2-fold (p < 0.01). Compared with control U251, U251 O cells were rounded, smaller, showed a disorganized cytoskeleton, exhibited reduced vinculin staining, and were easily detached from the growing surface. They showed a marked increase in dihydroethidium staining, suggesting increased oxidative stress. The expression of phosphorylated extracellular signal-regulated kinase 1/2, cyclin D1/2, and vascular endothelial growth factor was markedly elevated in U251 O. The hyperproliferative and signaling effects seen in U251 O cells are abolished by selective CYP4A inhibition of 20-HETE formation with HET0016 [N-hydroxy-N'-(4-butyl-2-methylphenyl)-formamidine], by small interfering RNA against the enzyme, and by the putative 20-HETE antagonist, 20-hydroxyeicosa-5(Z),14(Z)-dienoic acid. In vivo, implantation of U251O cells in the brain of nude rats resulted in a approximately 10-fold larger tumor volume (10 days postimplantation) compared with animals receiving mock-transfected U251 cells. These data show that elevations in 20-HETE synthesis in U251 cells lead to an increased growth both in vitro and in vivo. This suggests that 20-HETE may have proto-oncogenic properties in U251 human gliomas. Further studies are needed to determine whether 20-HETE plays a role promoting growth of some human gliomas.

Adherent Self-Renewable Human Embryonic Stem Cell-Derived Neural Stem Cell Line: Functional Engraftment in Experimental Stroke Model

BackgroundHuman embryonic stem cells (hESCs) offer a virtually unlimited source of neural cells for structural repair in neurological disorders, such as stroke. Neural cells can be derived from hESCs either by direct enrichment, or by isolating specific growth factor-responsive and expandable populations of human neural stem cells (hNSCs). Studies have indicated that the direct enrichment method generates a heterogeneous population of cells that may contain residual undifferentiated stem cells that could lead to tumor formation in vivo.Methods/Principal FindingsWe isolated an expandable and homogenous population of hNSCs (named SD56) from hESCs using a defined media supplemented with epidermal growth factor (EGF), basic fibroblast growth factor (bFGF) and leukemia inhibitory growth factor (LIF). These hNSCs grew as an adherent monolayer culture. They were fully neuralized and uniformly expressed molecular features of NSCs, including nestin, vimentin and radial glial markers. These hNSCs did not express the pluripotency markers Oct4 or Nanog, nor did they express markers for the mesoderm or endoderm lineages. The self-renewal property of the hNSCs was characterized by a predominant symmetrical mode of cell division. The SD56 hNSCs differentiated into neurons, astrocytes and oligodendrocytes throughout multiple passages in vitro, as well as after transplantation. Together, these criteria confirm the definitive NSC identity of the SD56 cell line. Importantly, they exhibited no chromosome abnormalities and did not form tumors after implantation into rat ischemic brains and into naïve nude rat brains and flanks. Furthermore, hNSCs isolated under these conditions migrated toward the ischemia-injured adult brain parenchyma and improved the independent use of the stroke-impaired forelimb two months post-transplantation.Conclusions/SignificanceThe SD56 human neural stem cells derived under the reported conditions are stable, do not form tumors in vivo and enable functional recovery after stroke. These properties indicate that this hNSC line may offer a renewable, homogenous source of neural cells that will be valuable for basic and translational research.

In vitro apoptotic induction of human glioblastoma cells by Fas ligand plus etoposide and in vivo antitumour activity of combined drugs in xenografted nude rats

Human glioblastomas that express Fas/CD95 receptor are highly resistant to conventional brain tumour therapies. The aim of this study is to evaluate anti-tumour properties of a combination of Fas ligand (FasL) plus etoposide with or without dexamethasone on intracerebral experimental glioblastomas. The human Fas-expressing glioblastoma cell line, U-87 MG, was firstly studied in vitro for apoptosis and proliferation assays in the presence of FasL and etoposide, separately or associated, in order to detect a supra-additive effect on FasL or etoposide-induced apoptosis. The tumourigenicity of the U-87 MG cell line and therapeutic effects of FasL-etoposide alone or combined with dexamethasone were next studied on U-87 MG cells xenografted to nude-rat brain and tumour size was hence examined by histological and immunohistochemical stainings. We demonstrated in vitro that the combination of both molecules strongly inhibited the proliferation rate and increased the sensitivity of glioblastoma cells to Fas or etoposide-mediated apoptosis. Moreover, analysis of rat brains was performed 30 days after xenograft of glioblastoma cells. These data show that the combination of FasL and etoposide could reduce significantly the tumour size and that the addition of dexamethasone enhanced the inhibiting effect of FasL and etoposide on tumour growth in vivo.

Protein Disulfide Isomerase Expression Is Related to the Invasive Properties of Malignant Glioma

By serial transplantation of human glioblastoma biopsies into the brain of immunodeficient nude rats, two different tumor phenotypes were obtained. Initially, the transplanted xenografts displayed a highly invasive phenotype that showed no signs of angiogenesis. By serial transplantation in animals, the tumors changed to a less invasive, predominantly angiogenic phenotype. To identify novel proteins related to the invasive phenotype, the xenografts were analyzed using a global proteomics approach. One of the identified proteins was protein disulfide isomerase (PDI) A6 precursor. PDI is a chaperone protein that mediates integrin-dependent cell adhesion. It is both present in the cytosol and at the cell surface. We show that PDI is strongly expressed on invasive glioma cells, in both xenografts and at the invasive front of human glioblastomas. Using an in vitro migration assay, we also show that PDI is expressed on migrating glioma cells. To determine the functional significance of PDI in cell migration, we tested the effect of a PDI inhibitor, bacitracin, and a PDI monoclonal antibody on glioma cell migration and invasion in vitro. Both tumor spheroids derived from human glioblastoma xenografts in nude rat brain and cell line spheroids were used. The PDI antibody, as well as bacitracin, inhibited tumor cell migration and invasion. The anti-invasive effect of bacitracin was reversible after withdrawal of the inhibitor, indicating a specific, nontoxic effect. In conclusion, using a global proteomics approach, PDI was identified to play an important role in glioma cell invasion, and its action was effectively inhibited by bacitracin.

Human glioblastoma biopsy spheroids xenografted into the nude rat brain show growth inhibition after stereotactic radiosurgery

The Gamma Knife is currently used to boost treatment of malignant gliomas. However, few experimental studies have focused on its radiobiological effects. In this work, the growth and invasiveness of human glioblastoma spheroids xenografted into nude rat brains were assessed after radiosurgery. Temporary in vitro as well as long-term in vivo radiation effects were studied. Glioblastoma biopsy spheroids were irradiated with 12 or 24 Gy. Short-term in vitro spheroid viability and tumour cell migration was determined by microscopic techniques. Pre-irradiated glioblastoma spheroids were implanted into brains of immunosuppressed rats. Long-term tumour development was assessed by magnetic resonance (MR) imaging, and animal survival was recorded. An immunohistochemical analysis was performed on the sectioned rat brains. Both un-irradiated and irradiated spheroids remained viable during 2 months in culture, but a dose-dependent inhibition of tumour growth and migration was seen. MR imaging 4 weeks after implantation also showed a dose-dependent inhibition in tumour development. Median animal survival times were 25.5 days (control group), 43 days (12 Gy group) and 96 days (24 Gy group). The study of in vivo long-term radiation effects on the remaining viable tumour population showed no difference in Ki-67 labelling index and microvascular density before and after radiosurgery. A dose-dependent inhibition of tumour growth and invasion, as well as a dose-dependent increase in animal survival was observed. The model system described is well suited for assessing the radiobiological effects of Gamma Knife radiosurgery. The results indicate that radiosurgery of malignant gliomas might be effective in controlling tumour progression in selected glioblastoma patients.

NG2 expression regulates vascular morphology and function in human brain tumours

Tumour angiogenesis is a tightly regulated process involving cross-talk between tumour cells and the host tissue. The underlying mechanisms that regulate such interactions remain largely unknown. NG2 is a transmembrane proteoglycan whose presence on transformed cells has been demonstrated to increase proliferation in vitro and angiogenesis in vivo. To study the effects of NG2 during tumour growth and progression, we engineered an NG2 positive human glioma cell line (U251-NG2) from parental NG2 negative cells (U251-WT) and implanted both cell types stereotactically into immunodeficient nude rat brains. The tumours were longitudinally monitored in vivo using multispectral MRI employing two differently sized contrast agents (Gd-DTPA-BMA and Gadomer) to assess vascular leakiness, vasogenic oedema, tumour volumes and necrosis. Comparisons of Gd-DTPA-BMA and Gadomer revealed differences in their spatial distribution in the U251-NG2 and U251-WT tumours. The U251-NG2 tumours exhibited a higher leakiness of the larger molecular weight Gadomer and displayed a stronger vasogenic oedema (69.9 ± 15.2, P = 0.018, compared to the controls (10.7 ± 7.7). Moreover, immunohistochemistry and electron microscopy revealed that the U251-NG2 tumours had a higher microvascular density (11.81 ± 0.54; P = 0.0010) compared to controls (5.76 ± 0.87), with vessels that displayed larger gaps between the endothelial cells. Thus, tumour cells can regulate both the function and structure of the host-derived tumour vasculature through NG2 expression, suggesting a role for NG2 in the cross-talk between tumour–host compartments.