Perspectives for Ezrin and Radixin in Astrocytes: Kinases, Functions and Pathology.

Astrocytes are increasingly perceived as active partners in physiological brain function and behaviour. The structural correlations of the glia-synaptic interaction are the peripheral astrocyte processes (PAPs), where ezrin and radixin, the two astrocytic members of the ezrin-radixin-moesin (ERM) family of proteins are preferentially localised. While the molecular mechanisms of ERM (in)activation appear universal, at least in mammalian cells, and have been studied in great detail, the actual ezrin and radixin kinases, phosphatases and binding partners appear cell type specific and may be multiplexed within a cell. In astrocytes, ezrin is involved in process motility, which can be stimulated by the neurotransmitter glutamate, through activation of the glial metabotropic glutamate receptors (mGluRs) 3 or 5. However, it has remained open how this mGluR stimulus is transduced to ezrin activation. Knowing upstream signals of ezrin activation, ezrin kinase(s), and membrane-bound binding partners of ezrin in astrocytes might open new approaches to the glial role in brain function. Ezrin has also been implicated in invasive behaviour of astrocytomas, and glial activation. Here, we review data pertaining to potential molecular interaction partners of ezrin in astrocytes, with a focus on PKC and GRK2, and in gliomas and other diseases, to stimulate further research on their potential roles in glia-synaptic physiology and pathology.

Radio-chemotherapy improves survival in IDH-mutant, 1p/19q non-codeleted secondary high-grade astrocytoma patients.

Isocitrate dehydrogenase (IDH) mutations are beginning to drive decisions on therapy for glioma patients. Here we sought to determine the impact of adjuvant treatment in patients with IDH-mutant, 1p/19q non-codeleted secondary high-grade astrocytoma (sHGA) WHO grades III/IV. Clinical data of 109 sHGA patients grades III/IV, in addition to IDH mutation-, 1p/19q-codeletion- and MGMT-promoter methylation status-were retrospectively analyzed. Survival analysis in relation to adjuvant treatment modalities and molecular profiling were performed. Out of 109 patients, 88 patients (80.7 %) harbored IDH mutations, 30 patients had a 1p/19q-codeletion (27.5 %) and 69 patients (63.3 %) exhibited a methylated MGMT-promoter status. At a median follow-up of 9.8 years, 62 patients (57 %) died. The postsurgical treatment included: radio-chemotherapy (RT-CT; 54.5 %), RT alone (19.3 %), and CT alone (22.7 %). The median overall survival (OS) in the entire group was 3.4 years (1.9-6.7 years). Patients who received RT-CT had a significantly longer OS compared with those who underwent RT alone (6.5 vs. 1.2 years, HR 0.35, CI 0.32-0.51, p = 0.011). In the IDH-mutant 1p/19q non-codeleted sHGA subgroup the RT-CT cohort had a significantly longer OS in comparison to the RT cohort (6.4 vs. 1.2 years, HR 2.7, CI 1.1-6.5, p = 0.022). In the stepwise multivariable Cox model for OS of all 88 IDH-mutant sHGA patients, survival was strongly associated with only one factor, namely, adjuvant RT-CT at diagnosis of a sHGA. This retrospective long-term study demonstrates that RT and CT (mostly PCV) significantly improves progression-free and overall survival in IDH-mutant secondary high-grade astrocytoma patients, regardless of 1p/19q-codeletion status.

A five year-old child with clear cell petro-clival meningioma: case report with clinical and histopathological long-term follow-up.

BACKGROUND: Only a few cases have been previously published about clear cell meningiomas in children, the majority of them in the location of the spine. We describe an unusual case of clear cell meningioma occurring at the petro-clival region in a 5-year-old child. We further seek to determine the impact of several growth factors as well as the AKT1 mutation on the tumor growth pattern. CASE PRESENTATION: A five-year-old girl was presented with a one-week history of cephalgia, ataxia, and left sided torticollis. Magnetic resonance imaging (MRI) revealed a dumbbell-shaped homogeneously petro-clival gadolinium-enhancing mass. A staged operative approach was chosen, and a complete removal of the tumor was achieved. Due to recurrent tumor progression, the child underwent several tumor surgeries and two cranial radiations. None of the treatments were able to stop tumor progression. Consequently, the child died at the age of 14 after further extensive intracranial and extracranial tumor progression. The initial histological examination revealed a clear cell meningioma WHO grade II with an MIB-1 labeling index of <1%, which gradually increased with every recurrence up to 10% by the last progression at the age of 13 years. Analogically, an increasing overexpression of epidermal growth factor receptor (EGFR), the platelet-derived growth factor receptor (PDGFR), and the vascular endothelial growth factor receptor (VEGFR) was observed with each recurrence. The AKT1 (E17K) mutation in the tumor was not detectable in all investigated specimens. CONCLUSION: Pediatric clear cell meningiomas WHO grade II are very rare. Our data demonstrate the progressive overexpression of EGF-, PDGF-, and VEGF-receptors in each recurrence, providing one of these receptors as targeted therapy in such cases. Further evaluation of these growth factors in clear cell meningioma is required to establish the optimal treatment of these aggressive tumors.

Hyperspectral unmixing of Raman micro-images for assessment of morphological and chemical parameters in non-dried brain tumor specimens.

Hyperspectral unmixing is an unsupervised algorithm to calculate a bilinear model of spectral endmembers and abundances of components from Raman images. Thirty-nine Raman images were collected from six glioma brain tumor specimens. The tumor grades ranged from astrocytoma WHO II to glioblastoma multiforme WHO IV. The abundance plots of the cell nuclei were processed by an image segmentation procedure to determine the average nuclei size, the number of nuclei, and the fraction of nuclei area. The latter two morphological parameters correlated with the malignancy. A combination of spectral unmixing and non-negativity constrained linear least squares fitting is introduced to assess chemical parameters. First, endmembers of the most abundant and most dissimilar components were defined that represent all data sets. Second, the content of the obtained components' proteins, nucleic acids, lipids, and lipid to protein ratios were determined in all Raman images. Except for the protein content, all chemical parameters correlated with the malignancy. We conclude that the morphological and chemical information offer new ways to develop Raman-based classification approaches that can complement diagnosis of brain tumors. The role of non-linear Raman modalities to speed-up image acquisition is discussed.

Chronic diarrhea as the initial clinical manifestation of light-chain amyloidosis with cardiac involvement despite negative duodenal and rectal biopsies.

Early and accurate diagnosis and a prompt initiation of treatment are critical for the prognosis of light-chain amyloidosis. The present article describes a case involving a 62-year-old patient who experienced unexplained, chronic diarrhea with negative duodenal and rectal biopsies. Serum immunofixation, a free light-chain assay, electrocardiography and echocardiography were performed after the patient developed syncope. The results of these diagnostic investigations showed characteristic signs of systemic amyloidosis. Cardiac and bone marrow biopsies confirmed the diagnosis of systemic light-chain amyloidosis. The chronic diarrhea was found to be due to an autonomic neuropathy of the enteric nervous system.

Vibrational spectroscopic imaging and multiphoton microscopy of spinal cord injury.

Spinal cord injury triggers a series of complex biochemical alterations of nervous tissue. Up to now, such cellular events could not be studied without conventional tissue staining. The development of optical, label-free imaging techniques could provide powerful monitoring tools with the potential to be applied in vivo. In this work, we assess the ability of vibrational spectroscopy to generate contrast at molecular level between normal and altered regions in a rat model of spinal cord injury. Using tissue sections, we demonstrate that Fourier transform infrared (FT-IR) spectroscopy and spontaneous Raman spectroscopy are able to identify the lesion, the surrounding scar, and unharmed normal tissue, delivering insight into the biochemical events induced by the injury and allowing mapping of tissue degeneration. The FT-IR and Raman spectroscopic imaging provides the basis for fast multimodal nonlinear optical microscopy (coherent anti-Stokes Raman scattering, endogenous two-photon fluorescence, and second harmonic generation). The latter proves to be a fast tool for imaging of the lesion on unstained tissue samples, based on the alteration in lipid content, extracellular matrix composition, and microglia/macrophages distribution pattern. The results establish these technologies in the field of regeneration in central nervous system, with the long-term goal to extend them to intravital use, where fast and nonharmful imaging is required.

Unsupervised unmixing of Raman microspectroscopic images for morphochemical analysis of non-dried brain tumor specimens.

Raman microspectroscopic imaging provides molecular contrast in a label-free manner with subcellular spatial resolution. These properties might complement clinical tools for diagnosis of tissue and cells in the future. Eight Raman spectroscopic images were collected with 785 nm excitation from five non-dried brain specimens immersed in aqueous buffer. The specimens were assigned to molecular and granular layers of cerebellum, cerebrum with and without scattered tumor cells of astrocytoma WHO grade III, ependymoma WHO grade II, astrocytoma WHO grade III, and glioblastoma multiforme WHO grade IV with subnecrotic and necrotic regions. In contrast with dried tissue section, these samples were not affected by drying effects such as crystallization of lipids or denaturation of proteins and nucleic acids. The combined data sets were processed by use of the hyperspectral unmixing algorithms N-FINDR and VCA. Both unsupervised approaches calculated seven endmembers that reveal the abundance plots and spectral signatures of cholesterol, cholesterol ester, nucleic acids, carotene, proteins, lipids, and buffer. The endmembers were correlated with Raman spectra of reference materials. The focus of the single mode laser near 1 µm and the step size of 2 µm were sufficiently small to resolve morphological details, for example cholesterol ester islets and cell nuclei. The results are compared for both unmixing algorithms and with previously reported supervised spectral decomposition techniques.

Label-free differentiation of human pituitary adenomas by FT-IR spectroscopic imaging.

Fourier transform infrared (FT-IR) spectroscopic imaging has been used to characterize different types of pituitary gland tumors and normal pituitary tissue. Freshly resected tumor tissue from surgery was prepared as thin cryosections and examined by FT-IR spectroscopic imaging. Tissue types were discriminated via k-means cluster analysis and a supervised classification algorithm based on linear discriminant analysis. Spectral classification allowed us to discriminate between tumor and non-tumor cells, as well as between tumor cells that produce human growth hormone (hGH+) and tumor cells that do not produce that hormone (hGH-). The spectral classification was compared and contrasted with a histological PAS and orange G stained image. It was further shown that hGH+ pituitary tumor cells show stronger amide bands than tumor cells that do not produce hGH. This study demonstrates that FT-IR spectroscopic imaging can not only potentially serve as a fast and objective approach for discriminating pituitary gland tumors from normal tissue, but that it can also detect hGH-producing tumor cells.

SOX2-RNAi attenuates S-phase entry and induces RhoA-dependent switch to protease-independent amoeboid migration in human glioma cells.

BACKGROUND: SOX2, a high mobility group (HMG)-box containing transcription factor, is a key regulator during development of the nervous system and a persistent marker of neural stem cells. Recent studies suggested a role of SOX2 in tumor progression. In our previous work we detected SOX2 in glioma cells and glioblastoma specimens. Herein, we aim to explore the role of SOX2 for glioma malignancy in particular its role in cell proliferation and migration. METHODS: Retroviral shRNA-vectors were utilized to stably knockdown SOX2 in U343-MG and U373-MG cells. The resulting phenotype was investigated by Western blot, migration/invasion assays, RhoA G-LISA, time lapse video imaging, and orthotopic xenograft experiments. RESULTS: SOX2 depletion results in pleiotropic effects including attenuated cell proliferation caused by decreased levels of cyclinD1. Also an increased TCF/LEF-signaling and concomitant decrease in Oct4 and Nestin expression was noted. Furthermore, down-regulation of focal adhesion kinase (FAK) signaling and of downstream proteins such as HEF1/NEDD9, matrix metalloproteinases pro-MMP-1 and -2 impaired invasive proteolysis-dependent migration. Yet, cells with knockdown of SOX2 switched to a RhoA-dependent amoeboid-like migration mode which could be blocked by the ROCK inhibitor Y27632 downstream of RhoA-signaling. Orthotopic xenograft experiments revealed a higher tumorigenicity of U343-MG glioma cells transduced with shRNA targeting SOX2 which was characterized by increased dissemination of glioma cells. CONCLUSION: Our findings suggest that SOX2 plays a role in the maintenance of a less differentiated glioma cell phenotype. In addition, the results indicate a critical role of SOX2 in adhesion and migration of malignant gliomas.

Carnosine retards tumor growth in vivo in an NIH3T3-HER2/neu mouse model.

BACKGROUND: It was previously demonstrated that the dipeptide carnosine inhibits growth of cultured cells isolated from patients with malignant glioma. In the present work we investigated whether carnosine also affects tumor growth in vivo and may therefore be considered for human cancer therapy. RESULTS: A mouse model was used to investigate whether tumor growth in vivo can be inhibited by carnosine. Therefore, NIH3T3 fibroblasts, conditionally expressing the human epidermal growth factor receptor 2 (HER2/neu), were implanted into the dorsal skin of nude mice, and tumor growth in treated animals was compared to control mice. In two independent experiments nude mice that received tumor cells received a daily intra peritoneal injection of 500 microl of 1 M carnosine solution. Measurable tumors were detected 12 days after injection. Aggressive tumor growth in control animals, that received a daily intra peritoneal injection of NaCl solution started at day 16 whereas aggressive growth in mice treated with carnosine was delayed, starting around day 19. A significant effect of carnosine on tumor growth was observed up to day 24. Although carnosine was not able to completely prevent tumor growth, a microscopic examination of tumors revealed that those from carnosine treated animals had a significant lower number of mitosis (p < 0.0003) than untreated animals, confirming that carnosine affects proliferation in vivo. CONCLUSION: As a naturally occurring substance with a high potential to inhibit growth of malignant cells in vivo, carnosine should be considered as a potential anti-cancer drug. Further experiments should be performed in order to understand how carnosine acts at the molecular level.

Suitability of infrared spectroscopic imaging as an intraoperative tool in cerebral glioma surgery.

Infrared spectroscopic imaging is a promising intraoperative tool which enables rapid, on-site diagnosis of brain tumors during neurosurgery. A classification model was recently developed using infrared spectroscopic images from thin tissue sections to grade malignant gliomas, the most frequent class of primary brain tumor. In this study the model was applied to 54 specimens from six patients with inhomogeneous gliomas composed of regions with different tumor density and morphology. The resection was controlled using neuronavigation which transfers the findings obtained by preoperative magnetic resonance imaging (MRI) into the operating field. For comparison, all specimens were independently evaluated by histopathology after hematoxylin and eosin staining. The infrared-derived grading agreed with histopathology and MRI findings for almost all specimens. With regard to histopathological assessment, sensitivities of 100% (22/22) and 93.1% (27/29) and specificities of 96.9% (31/32) and 88.0% (22/25) were achieved, depending on whether the classification was based on the predominant or maximal tumor grade, respectively, in the specimen. Altogether, in 98% (53/54) of all specimens the decision to continue or not continue tumor resection could have been made according to the infrared spectroscopic classification. This retrospective study clearly demonstrates that infrared spectroscopic imaging may help to define tumor margins intraoperatively and to detect high-grade tumor residues for achieving more radical tumor resection.

Identification of primary tumors of brain metastases by SIMCA classification of IR spectroscopic images.

Brain metastases are secondary intracranial lesions which occur more frequently than primary brain tumors. The four most abundant types of brain metastasis originate from primary tumors of lung cancer, colorectal cancer, breast cancer and renal cell carcinoma. As metastatic cells contain the molecular information of the primary tissue cells and IR spectroscopy probes the molecular fingerprint of cells, IR spectroscopy based methods constitute a new approach to determine the origin of brain metastases. IR spectroscopic images of 4 by 4 mm2 tissue areas were recorded in transmission mode by a FTIR imaging spectrometer coupled to a focal plane array detector. Unsupervised cluster analysis revealed variances within each cryosection. Selected clusters of five IR images with known diagnoses trained a supervised classification model based on the algorithm soft independent modeling of class analogies (SIMCA). This model was applied to distinguish normal brain tissue from brain metastases and to identify the primary tumor of brain metastases in 15 independent IR images. All specimens were assigned to the correct tissue class. This proof-of-concept study demonstrates that IR spectroscopy can complement established methods such as histopathology or immunohistochemistry for diagnosis.

Ezrin immunoreactivity reveals specific astrocyte activation in cerebral HIV.

The actin-binding protein ezrin is associated with cellular shape changes, motility, tumor invasion, and lymphocyte activation. We have earlier shown that ezrin immunoreactivity (IR) is faintly present in normal astrocytes but increased in malignant human astrogliomas. We studied the role of ezrin in astrocyte activation, applying immunostaining on serial paraffin sections from human autopsied brain tissues (51 cases). Cerebral HIV infection was chosen as a model displaying consistent exemplary astrocyte activation. Semiquantitative ezrin-IR was compared with the common glial markers GFAP, ferritin, and HLA-DR in relation to clinical and morphologic criteria of HIV encephalopathy. In all cases with HIV infection, GFAP-, HLA-DR-, and ferritin-IR were elevated in comparison to normal brain tissues. In contrast, high ezrin-IR in HIV infection strictly correlated with additional HIV encephalopathy. HIV encephalopathy with particularly high ezrin-IR was correlated with neuronal apoptosis (TUNEL). Combined ezrin-IR and GFAP-IR thus reveals 2 distinct states of astrocytic activation. Normal ezrin-IR, when paralleled by upregulated GFAP, reflects astroglial activation not associated with neuronal apoptosis. High ezrin-IR indicates specific astrocyte stressors related to cellular damage within the central nervous system. Ezrin-IR might also provide a diagnostic tool for the classification of HIV encephalopathy.

Intrinsic indicator of photodamage during label-free multiphoton microscopy of cells and tissues.

Multiphoton imaging has evolved as an indispensable tool in cell biology and holds prospects for clinical applications. When addressing endogenous signals such as coherent anti-Stokes Raman scattering (CARS) or second harmonic generation, it requires intense laser irradiation that may cause photodamage. We report that increasing endogenous fluorescence signal upon multiphoton imaging constitutes a marker of photodamage. The effect was studied on mouse brain in vivo and ex vivo, on ex vivo human brain tissue samples, as well as on glioblastoma cells in vitro, demonstrating that this phenomenon is common to a variety of different systems, both ex vivo and in vivo. CARS microscopy and vibrational spectroscopy were used to analyze the photodamage. The development of a standard easy-to-use model that employs rehydrated cryosections allowed the characterization of the irradiation-induced fluorescence and related it to nonlinear photodamage. In conclusion, the monitoring of endogenous two-photon excited fluorescence during label-free multiphoton microscopy enables to estimate damage thresholds ex vivo as well as detect photodamage during in vivo experiments.

Label-free delineation of brain tumors by coherent anti-Stokes Raman scattering microscopy in an orthotopic mouse model and human glioblastoma.

BACKGROUND: Coherent anti-Stokes Raman scattering (CARS) microscopy provides fine resolution imaging and displays morphochemical properties of unstained tissue. Here, we evaluated this technique to delineate and identify brain tumors. METHODS: Different human tumors (glioblastoma, brain metastases of melanoma and breast cancer) were induced in an orthotopic mouse model. Cryosections were investigated by CARS imaging tuned to probe C-H molecular vibrations, thereby addressing the lipid content of the sample. Raman microspectroscopy was used as reference. Histopathology provided information about the tumor's localization, cell proliferation and vascularization. RESULTS: The morphochemical contrast of CARS images enabled identifying brain tumors irrespective of the tumor type and properties: All tumors were characterized by a lower CARS signal intensity than the normal parenchyma. On this basis, tumor borders and infiltrations could be identified with cellular resolution. Quantitative analysis revealed that the tumor-related reduction of CARS signal intensity was more pronounced in glioblastoma than in metastases. Raman spectroscopy enabled relating the CARS intensity variation to the decline of total lipid content in the tumors. The analysis of the immunohistochemical stainings revealed no correlation between tumor-induced cytological changes and the extent of CARS signal intensity reductions. The results were confirmed on samples of human glioblastoma. CONCLUSIONS: CARS imaging enables label-free, rapid and objective identification of primary and secondary brain tumors. Therefore, it is a potential tool for diagnostic neuropathology as well as for intraoperative tumor delineation.

An extremely rare, remote intracerebral metastasis of oral cavity cancer: a case report.

Distant brain metastases from oral squamous cell carcinomas (OSCC) are extremely rare. Here we describe a case of a 53-year-old man with a primary OSCC who referred to the neurosurgical department because of epileptic seizures. MR imaging revealed an enhancing lesion in the right parietal lobe. A craniotomy with tumor removing was performed. Histopathological examination verified an invasive, minimally differentiated metastasis of the primary OSCC. The patient refused whole brain radiation therapy and died from pulmonary metastatic disease 10 months after the neurosurgical intervention without any cerebral recurrence. To the authors' knowledge, only two similar cases have been previously reported.

Is there pseudoprogression in secondary glioblastomas?

PURPOSE: Pseudoprogression (PP) during adjuvant treatment of glioblastoma (GBM) is frequent and is a clinically and radiologically challenging problem. While there are several reports of the frequency of PP in GBM cohorts including mainly patients with primary GBM, there are few data on the incidence of PP in patients with secondary glioblastomas (sGBM). Therefore, the goal of this study was to evaluate the frequency of PP in sGBM. METHODS AND MATERIALS: We retrospectively evaluated the incidence of PP in adult patients with sGBM treated with chemoradiation therapy (CRTx) using temozolomide (TMZ) and sought to assess if there was an association between PP and MGMT promoter methylation status, IDH mutations status, or 1p/19q codeletion. The definition of PP according to the Response Assessment in Neuro-Oncology Working Group was used. RESULTS: None of the evaluable 15 sGBM patients in our series demonstrated a PP. Of the 9 sGBM patients who received concomitant CRTx with TMZ, 6 patients had the methylated MGMT promoter, and 6 patients had IDH mutations. There also was no PP identified in sGBM patients who received sequential CRTx, irrespective of MGMT or IDH status. The median time of follow-up was 3.4 years after diagnosis of an sGBM, and the median overall survival was 18.2 months (range, 14.3-45.2 months). Three of 15 patients had previously received radiation therapy for their World Health Organization low-grade 2 glioma, while none of them had received chemotherapy at that stage. CONCLUSIONS: Based on this small series of sGBM patients treated with CRTx (concomitantly or sequentially) the frequency of PP appears to be very low in sGBM, even in those patients with methylated MGMT promoter or IDH mutations. Our results highlight the differences between primary glioblastomas and sGBM in particular as they relate to PP.

Infrared spectroscopic studies of cells and tissues: triple helix proteins as a potential biomarker for tumors.

In this work, the infrared (IR) spectra of living neural cells in suspension, native brain tissue, and native brain tumor tissue were investigated. Methods were developed to overcome the strong IR signal of liquid water so that the signal from the cellular biochemicals could be seen. Measurements could be performed during surgeries, within minutes after resection. Comparison between normal tissue, different cell lineages in suspension, and tumors allowed preliminary assignments of IR bands to be made. The most dramatic difference between tissues and cells was found to be in weaker IR absorbances usually assigned to the triple helix of collagens. Triple helix domains are common in larger structural proteins, and are typically found in the extracellular matrix (ECM) of tissues. An algorithm to correct offsets and calculate the band heights and positions of these bands was developed, so the variance between identical measurements could be assessed. The initial results indicate the triple helix signal is surprisingly consistent between different individuals, and is altered in tumor tissues. Taken together, these preliminary investigations indicate this triple helix signal may be a reliable biomarker for a tumor-like microenvironment. Thus, this signal has potential to aid in the intra-operational delineation of brain tumor borders.

Histopathological Investigation of Different MCAO Modalities and Impact of Autologous Bone Marrow Mononuclear Cell Administration in an Ovine Stroke Model.

Translational researchers and clinicians recommend the use of large animal models in preclinical stroke research. This represents an important part of a strategy aiming to prevent past translational failures in future therapeutic developments. Thirty-five Merino rams were subjected to sham surgery (n = 3), one-branch middle cerebral artery occlusion (MCAO, n = 8) or total MCAO (n = 24). Twelve animals from the latter group received intravenous administration of 4 × 10(6) autologous mononuclear bone marrow cells (BM MNC) per kilogram 24 h after total MCAO. Animals were sacrificed at day 49 post MCAO. Histological investigations were performed to reveal (1) the impact of different MCAO modalities on a cellular level and (2) the influence of BM MNC therapy following stroke. Clear differences between one-branch and total MCAO were observed histologically with results being comparable to those seen in human patients. BM MNC treatment reduced final lesion extension, lymphocytic infiltration and axonal degeneration after MCAO. The sheep model may represent a feasible tool for translational stroke research as pathohistological findings mimic the situation in humans. Histological evidence was found for beneficial impact of autologous BM MNC therapy. Further studies are needed to assess the neurofunctional impact of the approach in the gyrencephalic brain.

Glutamate receptors in pediatric tumors of the central nervous system.

Glutamate is the major excitatory neurotransmitter in the mammalian central nervous system (CNS). Experimental evidence indicates that glutamate receptor antagonists may limit tumor growth. This study explores expression of glutamate receptor subunits in pediatric CNS tumors. Samples from eight ependymomas, four glioblastomas, six medulloblastomas and eight low grade astrocytomas were analysed. RNA was used for semiquantitative and quantitative RT-PCR. We examined expression of NMDA receptor subunits NR1-NR3B, AMPA receptor subunits GluR1-GluR4, kainate receptor subunits GluR5-GluR7, KA1, KA2 and metabotropic receptor subunits mGluR1-8. Paraffin embedded samples were immunohistochemically stained for selected subunits. All glutamate receptor subunits were differentially expressed in the tumors examined. Expression of NR2D, NR3A, KA1, GluR4, mGluR1, mGluR4, mGluR5 and mGluR6 was higher in the high grade tumors compared to human brain (HB). In low grade astrocytomas expression of glutamate receptor subunits was comparable or lower than in HB. Immunohistochemistry revealed expression of several glutamate receptor subunit proteins in tumor specimen. This study demonstrates expression of glutamate receptor subunits in pediatric CNS tumors. Together with experimental evidence indicating that interference with glutamate signalling may suppress tumor growth, our findings suggest that adjunctive treatment with glutamate receptor modulators may be a feasible therapeutic option for pediatric patients with CNS tumors.