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Purpose: Mutations in the Isocitrate Dehydrogenase (IDH) genes, IDH1 or IDH2, define a group of adult diffuse gliomas associated with a younger age at diagnosis and better prognosis than IDH wild-type glioblastoma. Within IDH mutant gliomas, a small fraction of astrocytic tumors present with grade 4 histologic features and poor prognosis. In molecular studies, homozygous deletion of CDKN2A/B is independently predictive of poor prognosis and short survival. As a consequence, 2021 WHO classification now also recognizes this molecular feature, CDKN2A/B deletion, as sufficient for classifying an astrocytoma as IDH-mutant, WHO Grade 4, regardless of histological grading. Here, we investigate outcomes of patients with WHO Grade 4 IDH-mutant astrocytoma both with and without CDKN2A/B deletion, to compare these groups and evaluate clinical and radiographic factors that contribute to survival., Methods: We retrospectively identified 79 patients with IDH-mutant astrocytoma with CDKN2A/B deletion detected at initial diagnosis across five international institutions as well as a comparison group of 51 patients with IDH-mutant, astrocytoma, histologically Grade 4 without detectable CDKN2A/B deletion. We assembled clinical and radiographic features for all patients., Results: We find that CDKN2A/B deletion was associated with significantly worse overall survival (OS; p = 0.0004) and progression-free survival (PFS; p = 0.0026), with median OS of 5.0 years and PFS of 3.0 years, compared to 10.1 and 5.0 years for tumors with a grade 4 designation based only on histologic criteria. Multivariate analysis confirmed CDKN2A/B deletion as a strong negative prognosticator for both OS (HR = 3.51, p < 0.0001) and PFS (HR = 2.35, p = 0.00095). In addition, in tumors with CDKN2A/B deletion, preoperative contrast enhancement is a significant predictor of worse OS (HR 2.19, 95% CI 1.22-3.93, p = 0.0090) and PFS (HR = 1.74, 95% CI = 1.02-2.97, p = 0.0420)., Conclusions: These findings underscore the severe prognostic impact of CDKN2A/B deletion in IDH-mutant astrocytomas and highlight the need for further refinement of tumor prognostic categorization. Our results provide a key benchmark of baseline patient outcomes for therapeutic trials, underscoring the importance of CDKN2A/B status assessment, in addition to histologic grading, in clinical trial design and therapeutic decision-making for IDH-mutant astrocytoma patients., Competing Interests: Declarations. Competing interests: D. P. C reports grants from NIH and Tawingo Fund during the conduct ofthe study; financial compensation from Servier, Boston Scientific and Pyramid Biosciences for advisory input. PYW reports research support from Astra Zeneca, Black Diamond, Bristol Meyers Squibb, Celgene, Chimerix, Eli Lily, Erasca, Genentech/ Roche, Kazia, MediciNova, Merck, Novartis, Nuvation Bio, Servier, Vascular Biogenics, VBI Vaccines; personal fees from Astra Zeneca, Black Diamond, Celularity, Chimerix, Day One Bio, Genenta, Glaxo Smith Kline, Merck, Mundipharma, Novartis, Novocure, Nuvation Bio, Prelude Therapeutics, Sapience, Servier, Sagimet, Vascular Biogenics, VBI Vaccines. T.A.J. received honoraria from CSL Behring. J.J.M. reports grants from the National Institute of Neurological Diseases and Stroke, American Cancer Society, Seeman Family Funds, National Cancer Institute, and MGH Transformative Scholar Award during the conduct of the study; personal fees from Servier., (© 2024. The Author(s).)

Microglial cells in the brain tumor microenvironment are associated with enhanced glioma malignancy. They persist in an immunosuppressive M2 state at the peritumoral site and promote the growth of gliomas. Here, we investigated the underlying factors contributing to the abolished immune surveillance. We show that brain tumors escape pro-inflammatory M1 conversion of microglia via CD74 activation through the secretion of the cytokine macrophage migration inhibitory factor (MIF), which results in a M2 shift of microglial cells. Interruption of this glioma-microglial interaction through an antibody-neutralizing approach or small interfering RNA (siRNA)-mediated inhibition prolongs survival time in glioma-implanted mice by reinstating the microglial pro-inflammatory M1 function. We show that MIF-CD74 signaling inhibits interferon (IFN)-γ secretion in microglia through phosphorylation of microglial ERK1/2 (extracellular signal-regulated protein kinases 1 and 2). The inhibition of MIF signaling or its receptor CD74 promotes IFN-γ release and amplifies tumor death either through pharmacological inhibition or through siRNA-mediated knockdown. The reinstated IFN-γ secretion leads both to direct inhibition of glioma growth as well as inducing a M2 to M1 shift in glioma-associated microglia. Our data reveal that interference with the MIF signaling pathway represents a viable therapeutic option for the restoration of IFN-γ-driven immune surveillance.

The glutamate transporter xCT (SCL7a11, system Xc-, SXC) is an emerging key player in glutamate/cysteine/glutathione homeostasis in the brain and in cancer. xCT expression correlates with the grade of malignancy. Here, we report on the use of the U.S. Food and Drug Administration and EMA-approved xCT inhibitor, sulfasalazine (SAS) in gliomas. SAS does not affect cell viability in gliomas at concentrations below 200 µM. At higher concentrations SAS becomes gliomatoxic. Mechanistically SAS inhibits xCT and induces ferroptotic cell death in glioma cells. There is no evidence for impact on autophagic flux following SAS application. However, SAS can potentiate the efficacy of the standard chemotherapeutic and autophagy-inducing agent temozolomide (Temcat, Temodal or Temodar®). We also investigated SAS in non-transformed cellular constituents of the brain. Neurons and brain tissue are almost non-responding to SAS whereas isolated astrocytes are less sensitive towards SAS toxicity compared to gliomas. In vivo SAS treatment does not affect experimental tumor growth and treated animals revealed comparable tumor volume as untreated controls. However, SAS treatment resulted in reduced glioma-derived edema and, hence, total tumor volume burden as revealed by T2-weighted magnetic resonance imaging. Altogether, we show that SAS can be utilized for targeting the glutamate antiporter xCT activity as a tumor microenvironment-normalizing drug, while crucial cytotoxic effects in brain tumors are minor., Competing Interests: CONFLICTS OF INTERESTS The authors declare no competing financial conflict of interests.

Primary brain tumors are hallmarked for their destructive activity on the microenvironment and vasculature. However, solely few experimental techniques exist to access the tumor microenvironment under anatomical intact conditions with remaining cellular and extracellular composition. Here, we detail an ex vivo vascular glioma impact method (VOGIM) to investigate the influence of gliomas and chemotherapeutics on the tumor microenvironment and angiogenesis under conditions that closely resemble the in vivo situation. We generated organotypic brain slice cultures from rats and transgenic mice and implanted glioma cells expressing fluorescent reporter proteins. In the VOGIM, tumor-induced vessels presented the whole range of vascular pathologies and tumor zones as found in human primary brain tumor specimens. In contrast, non-transformed cells such as primary astrocytes do not alter the vessel architecture. Vascular characteristics with vessel branching, junctions and vessel meshes are quantitatively assessable as well as the peritumoral zone. In particular, the VOGIM resembles the brain tumor microenvironment with alterations of neurons, microglia and cell survival. Hence, this method allows live cell monitoring of virtually any fluorescence-reporter expressing cell. We further analyzed the vasculature and microglia under the influence of tumor cells and chemotherapeutics such as Temozolamide (Temodal/Temcad®). Noteworthy, temozolomide normalized vasculare junctions and branches as well as microglial distribution in tumor-implanted brains. Moreover, VOGIM can be facilitated for implementing the 3Rs in experimentations. In summary, the VOGIM represents a versatile and robust technique which allows the assessment of the brain tumor microenvironment with parameters such as angiogenesis, neuronal cell death and microglial activity at the morphological and quantitative level.

Despite advances in multimodal treatments, malignant gliomas remain characterized by a short survival time. Surgical treatment is accepted to be the first line of therapy, with recent studies revealing that maximal possible tumor reduction exerts significant impact on patient outcome. Consideration of tumor localization in relation to functionally eloquent brain areas has been gaining increasing importance. Despite existing assessment methods, the availability of a simple but reliable preoperative grading based on functional data would therefore prove to be indispensable for the prediction of postoperative outcome and hence for overall survival in glioma patients. We performed a clinical investigation comprising 322 patients with gliomas and developed a novel classification system of preoperative tumor status, which considers tumor operability based on two graduations (Friedlein Grading - FG): FGA with lesions at safe distance to eloquent regions which can be completely resected, and FGB referring to tumors which can only be partially resected or biopsied. Investigation of outcome revealed that FGA were characterized by a significantly longer overall survival time compared to FGB. We offer the opportunity to classify brain tumors in a dependable and reproducible manner. The FGA/B grading method provides high prognostic value with respect to overall survival time in relation to the extent of location-dependent tumor resection.

Malignant gliomas can be counted to the most devastating tumors in humans. Novel therapies do not achieve significant prolonged survival rates. The cancer cells have an impact on the surrounding vital tissue and form tumor zones, which make up the tumor microenvironment. We investigated the effects of sunitinib, a small molecule multitargeted receptor tyrosine kinase inhibitor, on constituents of the tumor microenvironment such as gliomas, astrocytes, endothelial cells, and neurons. Sunitinib has a known anti-angiogenic effect. We found that sunitinib normalizes the aberrant tumor-derived vasculature and reduces tumor vessel pathologies (i.e. auto-loops). Sunitinib has only minor effects on the normal, physiological, non-proliferating vasculature. We found that neurons and astrocytes are protected by sunitinib against glutamate-induced cell death, whereas sunitinib acts as a toxin towards proliferating endothelial cells and tumor vessels. Moreover, sunitinib is effective in inducing glioma cell death. We determined the underlying pathways by which sunitinib operates as a toxin on gliomas and found vascular endothelial growth factor receptor 2 (VEGFR2, KDR/Flk1) as the main target to execute gliomatoxicity. The apoptosis-inducing effect of sunitinib can be mimicked by inhibition of VEGFR2. Knockdown of VEGFR2 can, in part, foster the resistance of glioma cells to receptor tyrosine kinase inhibitors. Furthermore, sunitinib alleviates tumor-induced neurodegeneration. Hence, we tested whether temozolomide treatment could be potentiated by sunitinib application. Here we show that sunitinib can amplify the effects of temozolomide in glioma cells. Thus, our data indicate that combined treatment with temozolomide does not abrogate the effects of sunitinib. In conclusion, we found that sunitinib acts as a gliomatoxic agent and at the same time carries out neuroprotective effects, reducing tumor-induced neurodegeneration. Thus, this report uncovered sunitinib's actions on the brain tumor microenvironment, revealing novel aspects for adjuvant approaches and new clinical assessment criteria when applied to brain tumor patients., (© 2014 The Authors. Cancer Science published by Wiley Publishing Asia Pty Ltd on behalf of Japanese Cancer Association.)

Malignant gliomas belong to the most threatening tumor entities and are hallmarked by rapid proliferation, hypervascularization and an invasive growth pattern. The primary obstacle in surgical treatment lies in differentiation between healthy and pathological tissue at the tumor margins, where current visualization methods reach their limits. Here, we report on a novel technique (vascular dual intraoperative visualization approach - vDIVA) enabling visualization of different tumor zones (TZ I-III) on the basis of angiogenic hotspots. We investigated glioblastoma patients who underwent 5-ALA fluorescence-guided surgery with simultaneous intraoperative ICG fluorescence angiography. This vDIVA technique revealed hypervascularized areas which were further histologically investigated. Neuropathological assessments revealed tissue areas at the resection margins corresponding to TZ II, and postoperative CD34- and Map2 immunostaining confirmed these angiogenic hotspots to be occupied by glioma cells. Hence, the vascular architecture in this transitional zone could be well differentiated from both primary tumor bulk and healthy brain parenchyma. These data demonstrate that ICG fluorescence angiography improves state-of-the-art glioma surgery techniques and facilitates the future characterization of polyclonal attributes of malignant gliomas.

Malignant gliomas are characterized by neurodegenerative actions leading to the destruction of surrounding brain parenchyma. The disturbance in glutamate homeostasis caused by increased expression of the glutamate transporter xCT plays a key role in glioma progression. We demonstrate that the HDAC-inhibitor SAHA specifically inhibits the xCT-transporter expression. Thereby, tumor cell stress is engendered, marked by increase in ROS. Moreover, SAHA dependent xCT-reduction correlates with the inhibition of ATF4-expression, a factor known to foster xCT expression. Since xCT/system Xc- is pivotal for the brain tumor microenvironment, normalization of this system is a key in the management of malignant gliomas. To date, the problem lay in the inability to specifically target xCT due to the ubiquitous expression of the xCT-transporter--i.e. in non-cancerously transformed cells too--as well as its essential role in physiological CNS processes. Here, we show xCT-transporter equilibration through SAHA is specific for malignant brain tumors whereas SAHA does not affect the physiological xCT levels in healthy brain parenchyma. Our data indicate that SAHA operates on gliomas specifically via normalizing xCT expression which in consequence leads to reduced extracellular glutamate levels. This in turn causes a marked reduction in neuronal cell death and normalized tumor microenvironment.

Poor prognosis and limited therapeutic options render malignant brain tumors one of the most devastating diseases in clinical medicine. Current treatment strategies attempt to expand the therapeutic repertoire through the use of multimodal treatment regimens. It is here that dietary fibers have been recently recognized as a supportive natural therapy in augmenting the body's response to tumor growth. Here, we investigated the impact of isoflavonoids on primary brain tumor cells. First, we treated glioma cell lines and primary astrocytes with various isoflavonoids and phytoestrogens. Cell viability in a dose-dependent manner was measured for biochanin A (BCA), genistein (GST), and secoisolariciresinol diglucoside (SDG). Dose-response action for the different isoflavonoids showed that BCA is highly effective on glioma cells and nontoxic for normal differentiated brain tissues. We further investigated BCA in ex vivo and in vivo experimentations. Organotypic brain slice cultures were performed and treated with BCA. For in vivo experiments, BCA was intraperitoneal injected in tumor-implanted Fisher rats. Tumor size and edema were measured and quantified by magnetic resonance imaging (MRI) scans. In vascular organotypic glioma brain slice cultures (VOGIM) we found that BCA operates antiangiogenic and neuroprotective. In vivo MRI scans demonstrated that administered BCA as a monotherapy was effective in reducing significantly tumor-induced brain edema and showed a trend for prolonged survival. Our results revealed that dietary isoflavonoids, in particular BCA, execute toxicity toward glioma cells, antiangiogenic, and coevally neuroprotective properties, and therefore augment the range of state-of-the-art multimodal treatment approach., (© 2014 The Authors. Cancer Medicine published by John Wiley & Sons Ltd.)

Malignant gliomas represent one of the most devastating human diseases. Primary treatment of these tumours involves surgery to achieve tumour debulking, followed by a multimodal regimen of radiotherapy and chemotherapy. Survival time in patients with malignant glioma has modestly increased in recent years owing to advances in surgical and intraoperative imaging techniques, as well as the systematic implementation of randomized trial-based protocols and biomarker-based stratification of patients. The role and importance of several clinical and molecular factors-such as age, Karnofsky score, and genetic and epigenetic status-that have predictive value with regard to postsurgical outcome has also been identified. By contrast, the effect of the extent of glioma resection on patient outcome has received little attention, with an 'all or nothing' approach to tumour removal still taken in surgical practice. Recent studies, however, reveal that maximal possible cytoreduction without incurring neurological deficits has critical prognostic value for patient outcome and survival. Here, we evaluate state-of-the-art surgical procedures that are used in management of malignant glioma, with a focus on assessment criteria and value of tumour reduction. We highlight key surgical factors that enable optimization of adjuvant treatment to enhance patient quality of life and improve life expectancy.

Despite continuing debates around cytoreductive surgery in malignant gliomas, there is broad consensus that increased extent of tumor reduction improves overall survival. However, maximization of the extent of tumor resection is hampered by difficulty in intraoperative discrimination between normal and pathological tissue. In this context, two established methods for tumor visualization, fluorescence guided surgery with 5-ALA and intraoperative MRI (iMRI) with integrated functional neuronavigation were investigated as a dual intraoperative visualization (DIV) approach. Thirty seven patients presumably suffering from malignant gliomas (WHO grade III or IV) according to radiological appearance were included. Twenty-one experimental sequences showing complete resection according to the 5-ALA technique were confirmed by iMRI. Fourteen sequences showing complete resection according to the 5-ALA technique could not be confirmed by iMRI, which detected residual tumor. Further analysis revealed that these sequences could be classified as functional grade II tumors (adjacent to eloquent brain areas). The combination of fluorescence guided resection and intraoperative evaluation by high field MRI significantly increased the extent of tumor resection in this subgroup of malignant gliomas located adjacent to eloquent areas from 61.7% to 100%; 5-ALA alone proved to be insufficient in attaining gross total resection without the danger of incurring postoperative neurological deterioration. Furthermore, in the case of functional grade III gliomas, iMRI in combination with functional neuronavigation was significantly superior to the 5-ALA resection technique. The extent of resection could be increased from 57.1% to 71.2% without incurring postoperative neurological deficits.

Malignant glioma represents one of the most aggressive and lethal human neoplasias. A hallmark of gliomas is their rapid proliferation and destruction of vital brain tissue, a process in which excessive glutamate release by glioma cells takes center stage. Pharmacologic antagonism with glutamate signaling through ionotropic glutamate receptors attenuates glioma progression in vivo, indicating that glutamate release by glioma cells is a prerequisite for rapid glioma growth. Glutamate has been suggested to promote glioma cell proliferation in an autocrine or paracrine manner, in particular by activation of the (RS)-α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid hydrate (AMPA) subtype of glutamate receptors. Here, we dissect the effects of glutamate secretion on glioma progression. Glioma cells release glutamate through the amino-acid antiporter system X(c)(-), a process that is mechanistically linked with cystine incorporation. We show that disrupting glutamate secretion by interfering with the system X(c)(-) activity attenuates glioma cell proliferation solely cystine dependently, whereas glutamate itself does not augment glioma cell growth in vitro. Neither AMPA receptor agonism nor antagonism affects glioma growth in vitro. On a molecular level, AMPA insensitivity is concordant with a pronounced transcriptional downregulation of AMPA receptor subunits or overexpression of the fully edited GluR2 subunit, both of which block receptor activity. Strikingly, AMPA receptor inhibition in tumor-implanted brain slices resulted in markedly reduced tumor progression associated with alleviated neuronal cell death, suggesting that the ability of glutamate to promote glioma progression strictly requires the tumor microenvironment. Concerning a potential pharmacotherapy, targeting system X(c)(-) activity disrupts two major pathophysiological properties of glioma cells, that is, the induction of excitotoxic neuronal cell death and incorporation of cystine required for rapid proliferation.

Several nutrient transporters impacting the glutathione/redox cycle regulation and cell proliferation have been identified in cancer, which render these transporters potential prime targets for cytotoxic anticancer therapy. One promising transporter is system X(c)(-), also known as xCT (SLC7a11), which is expressed in various cancers including primary malignant brain tumors (gliomas). An important biological feature of these transporters, and in particular of xCT is its specific modulation of the tumor microenvironment leading to growth advantage for cancer. Thus, tumor microenvironment shaping by xCT inhibition revealed a so far neglected hallmark of gliomas, i.e. tumor-induced neurotoxicity and its impact on the development of peritumoral brain swelling. This review here discusses available pharmacological tools for the tumor microenvironment normalization, in the context of perifocal edema and the Warburg effect and highlights the implications of such metabolic normalization approach in the design of new therapies., (Copyright © 2010 Elsevier GmbH. All rights reserved.)

Brain edema is a hallmark of human malignant brain tumors and contributes to the clinical course and outcome of brain tumor patients. The so-called perifocal edema or brain swelling imposes in T2-weighted MR scans as high intensity areas surrounding the bulk tumor mass. The mechanisms of this increased fluid attraction and the cellular composition of the microenvironment are only partially understood. In this study, we focus on imaging perifocal edema in orthotopically implanted gliomas in rodents and correlate perifocal edema with immunohistochemical markers. We identified that areas of perifocal edema not only include the tumor invasion zone, but also are associated with increased glial fibrillary acidic protein (GFAP) and aquaporin-4 expression surrounding the bulk tumor mass. Moreover, a high number of activated microglial cells expressing CD11b and macrophage migration inhibitory factor (MIF) accumulate at the tumor border. Thus, the area of perifocal edema is mainly dominated by reactive changes of vital brain tissue. These data corroborate that perifocal edema identified in T2-weighted MR scans are characterized with alterations in glial cell distribution and marker expression forming an inflammatory tumor microenvironment.

Neurodegeneration and brain edema are hallmarks of human malignant brain tumors. Here we show that genetic or pharmacological inhibition of the glutamate transporter xCT (X(c-) system, encoded by SLC7a11) in vivo leads to abrogated neurodegeneration, attenuated perifocal edema and prolonged survival. These results show a crucial role for xCT in glioma-induced neurodegeneration and brain edema, corroborating the concept that edema formation may be in part a consequence of peritumoral cell death.

Gliomas are the most common primary tumors of the central nervous system, with glioblastomas as the most malignant entity. Rapid proliferation and diffuse brain invasion of these tumors are likely to determine the unfavorable prognosis. Considering its promigratory properties, the transforming growth factor-beta (TGF-beta) signaling pathway has become a major therapeutic target. Analyses of resected glioma tissues revealed an intriguing correlation between tumor grade and the expression of TGF-beta(1-3) as well as their receptors I and II. Here, we analyzed the effects of peroxisome proliferator-activated receptor gamma (PPAR-gamma) agonists on glioma proliferation, migration, and brain invasion. Using an organotypic glioma invasion model, we show that micromolar doses of the PPAR-gamma activator troglitazone blocked glioma progression without neurotoxic damage to the organotypic neuronal environment observed. This intriguing antiglioma property of troglitazone seems to be only partially based on its moderate cytostatic effects. We identified troglitazone as a potent inhibitor of glioma cell migration and brain invasion, which occurred in a PPAR-gamma-independent manner. The antimigratory property of troglitazone was in concordance with the transcriptional repression of TGF-beta(1-3) and their receptors I and II and associated with reduced TGF-beta release. Due to its capacity to counteract TGF-beta release and glioma cell motility and invasiveness already at low micromolar doses, troglitazone represents a promising drug for adjuvant therapy of glioma and other highly migratory tumor entities.

Inhibitors of histone deacetylases are promising compounds for the treatment of cancer but have not been systematically explored in malignant brain tumors. Here, we characterize the benzamide MS-275, a class I histone deacetylase inhibitor, as potent drug for experimental therapy of glioblastomas. Treatment of four glioma cell lines (U87MG, C6, F98, and SMA-560) with MS-275 significantly reduced cell growth in a concentration-dependent manner (IC(90), 3.75 micromol/L). Its antiproliferative effect was corroborated using a bromodeoxyuridine proliferation assay and was mediated by G(0)-G(1) cell cycle arrest (i.e., up-regulation of p21/WAF) and apoptotic cell death. Implantation of enhanced green fluorescent protein-transfected F98 glioma cells into slice cultures of rat brain confirmed the cytostatic effect of MS-275 without neurotoxic damage to the organotypic neuronal environment in a dose escalation up to 20 micromol/L. A single intratumoral injection of MS-275 7 days after orthotopic implantation of glioma cells in syngeneic rats confirmed the chemotherapeutic efficacy of MS-275 in vivo. Furthermore, its propensity to pass the blood-brain barrier and to increase the protein level of acetylated histone H3 in brain tissue identifies MS-275 as a promising candidate drug in the treatment of malignant gliomas.

Stem and progenitor cells (PCs) of various lineages have become attractive vehicles to improve therapeutic gene delivery to cancers, notably glioblastoma. Here we report that adult human and murine haematopoietic PCs display a tropism for intracerebral gliomas but not for normal brain tissue in mice. Organotypic hippocampal slice culture and spheroid confrontation assays confirm a directed PC migration towards glioma cells ex vivo and in vitro. RNA interference-mediated disruption of transforming growth factor beta (TGF-beta) synthesis by the glioma cells strongly inhibits PC migration. We delineate a CXC chemokine ligand (CXCL) 12-dependent pathway of TGF-beta-induced PC migration that is facilitated by MMP-9-mediated stem cell factor cleavage in vitro. Moreover, neutralizing antibodies to CXCL12 strongly reduce PC homing to experimental gliomas in vivo. Thus, we define here the molecular mechanism underlying the glioma tropism of the probably most easily accessible PC population suitable for cancer therapy, that is, adult haematopoietic PC.

Current treatment modalities for malignant gliomas do not allow long-term survival. Here, we identify suberoylanilide hydroxamic acid (SAHA), an inhibitor of histone deacetylases (HDAC), as an effective experimental anti-glioma agent. Administration of SAHA to various glioma cell lines obtained from human, rat and mouse inhibited tumour cell growth in a range of 1-10 microm. This anti-glioma property is associated with up-regulation of the cell cycle control protein p21/WAF, as well as the induction of apoptosis. A novel tumour invasion model using slice cultures of rat brain corroborated the anti-glioma properties of SAHA in the organotypic brain environment. In this model, glioma invasion compromised adjacent brain parenchyma, and this tumour-associated cytotoxicity could be inhibited by SAHA. In addition, a 10-fold dose escalation experiment did not challenge the viability of cultured brain slices. In vivo, a single intratumoural injection of SAHA 7 days after orthotopic implantation of glioma cells in syngeneic rats doubled their survival time. These observations identify chromatin-modifying enzymes as possible and promising targets for the pharmacotherapy of malignant gliomas.

Rapid growth and diffuse brain infiltration are hallmarks of malignant gliomas. The underlying molecular pathomechanisms of these tumors, however, remain to be determined. The authors present a novel glioma invasion model that allows researchers to monitor consecutively tumor cell proliferation and migration in an organotypic brain environment. Enhanced green fluorescent protein-labeled F98 rat glioma cells were implanted into slice cultures obtained from a rat hippocampus, and tumor growth was microscopically documented up to 20 days in vitro. Invasion along radially oriented migratory streams could be observed 5 days after implantation of rat F98, human U87MG, and mouse GL261 glioma cells, whereas human Be(2)c neuroblastoma cells and mouse HT22 hippocampal neurons failed to invade the brain parenchyma. Following implantation of F98 glioma cells into the entorhinal cortex, cell death was observed within the infiltrated brain parenchyma as well as in the neuroanatomically connected dentate gyrus. Application of the N-methyl-D-aspartate receptor antagonist MK801 to the culture medium significantly reduced neuronal degeneration in the dentate gyrus, whereas the alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate receptor antagonist GYKI 52466 inhibited peritumoral cytotoxicity. This new model allows researchers to address in a systematic manner the molecular pathways of brain invasion as well as specific tumor-host interactions such as necrosis.