Astrocytic Component Research Articles

The role of postoperative radiotherapy for the treatment of gangliogliomas

We read the article by Rades et al1 and we think there was a serious pathologic misinterpretation with these tumors. The authors included desmoplastic infantile gangliogliomas (DIGs) as part of the ganglioglioma category, when in fact they are very different entities from the epidemiological point of view in terms of clinical presentation, histology, and course of treatment. Gangliogliomas account for 1% to 7.6% of all brain tumors, with the higher percentage noted in the pediatric group.2 On light microscopy, both neuronal and astrocytic components are readily apparent. Astrocytic cells are confirmed by a positive chemical reaction to antiserum for glial fibrillary acidic protein (GFAP) and neoplastic ganglion cells demonstrate intense immunoreactivity for synaptophysin. These tumors are classified as either World Health Organization (WHO) grade I or II.2 Tumors with evidence of malignant transformation are anaplastic gangliogliomas (WHO grade III), not desmoplastic gangliogliomas. DIGs representing <1% of all intracranial tumors and are unusual in patients aged >6 years.3 The typical appearance of a DIG is a large cystic lesion with a solid mass located within the frontal and/or parietal lobes. Approximately 100 cases of DIGs have been described in the literature since its first description,4 and the median age at diagnosis is reported to be 5 to 6 months (range, 1-60 months). Noninfantile variants of this biologically benign intracranial neoplasm are rare. DIG has 2 distinct components: a solid component with intense desmoplasia that is always located close to the meninges and a cystic component, which is dominant and an integral part of the tumor. The common pathological features include intense desmoplasia containing GFAP-positive astrocytes and neuronal elements. DIGs are classified as benign WHO grade I tumors of infancy. Complete surgical resection has been possible in approximately 70% of all reported cases. However, in cases with incomplete surgical resection, a second surgery should be considered to be the treatment of choice. Miguel Gelebert-Gonzalez MD*, Ramon Serramito-Garcia MD*, * Department of Surgery, University of Santiago de Compostela, Santiago de Compostela, Spain.

Abstract 782: Characterization of genetic changes in oligodendroglial tumors including glioblastomas with oligodendroglial component

Abstract In contrast to astrocytic tumors including glioblastomas (GBM), oligodendrogliomas (O) show a better prognosis and increased responsiveness to chemotherapy. Interestingly, a small subgroup of glioblastomas contains areas with histological features of oligodendroglial differentiation. In the current WHO classification (2007) these tumors are now included as a variant of glioblastomas and are called glioblastomas with oligodendroglial component (GBMO). However, definitive diagnostic criteria still do not exist. In this study we used a genome wide approach (chromosomal comparative genomic hybridization (CGH) and molecular karyotyping) in combination with interphase fluoreszence in situ hybridization (FISH) (regions 1p, 1q, 7q, 10q, 17p, 19q, cen18, 21q) to genetically characterize GBMO and “classical” O. We analyzed the oligodendroglial and the astrocytic glioblastoma parts of 13 GBMO separately by chromosomal CGH of microdissected paraffin embedded tumor tissue and interphase FISH on paraffin sections. Furthermore, freshly frozen material of six oligodendrogliomas (4 WHO grade II, 6 WHO-grade III) was examined genome wide by using the standard Agilent 244A chip. We identified four distinct genetic subtypes in GBMO: an “astrocytic” subtype (9/13) characterized by +7/-10; an “oligodendroglial” subtype with −1p/-19q (1/13); an “intermediate” subtype showing +7/-1p (1/13), and an “other” subtype having none of the former aberrations typical for gliomas (2/13). In contrast, most “classical” O (5/6) showed combined 1p/19q deletion, corresponding genetically to the “oligodendroglial” subtype. Four of the O with 1p/19q codeletion showed additional aberrations (e. g. −4, −14, −9, −18). The different histological tumor parts of GBMO revealed common genetic changes in all tumors and showed additional aberrations specific for their oligodendroglial and astrocytic parts. These findings demonstrate the monoclonal origin of the tumor followed by the formation of the astrocytic and oligodendroglial components. We are currently evaluating the array CGH results of six oligodendrogliomas, which will also be presented. The diagnostic determination of these genetic signatures may allow for a better prognostication of the patients. Our results underline the importance of molecular cytogenetic analyses to supplement the histological diagnosis of gliomas. Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend. 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 782.

Classification and management of anaplastic gliomas

To summarize findings, discuss problems and define new questions from the past phase III trials in anaplastic gliomas. The current standard of care for first-line treatment in anaplastic gliomas is radiotherapy or chemotherapy. The next steps are to define the role and optimal sequencing of combined modality treatment focusing on radiotherapy and temozolomide and to develop trials with novel targeted treatments. The feature of necrosis in oligodendroglial tumors needs to be further studied, and molecular prognosticators will take more room. These include O⁶-methylguanylmethyltransferase promoter methylation, isocitrate dehydrogenase mutations and epidermal growth factor receptor amplification. Further, the notion that all anaplastic oligodendroglial tumors with or without a relevant astrocytic component fall into the same prognostic category and the obvious difficulties to type and to grade anaplastic gliomas pose an enormous burden on local diagnosis. The current and upcoming trials including the European Organization for Research and Treatment of Cancer 26053/22054 trial aim at solving some of these issues with an initial central pathology review. Anaplastic gliomas are an important group of brain tumors to develop future molecularly targeted therapies and should therefore be in the main focus of academic and industrial drug development, which aims at efficacy and avoiding long-term side effects.

Glioma-induced remodeling of the neurovascular unit

The normal BBB (blood–brain barrier) consists of a series of structures collectively known as neurovascular units, or NVU, that are composed of endothelial cells and astrocyte endfeet separated by a basal lamina at their interface. The integrity of the BBB and specifically endothelial tight junctions is maintained by interactions between these different components and the local microenvironment of the NVU. Central nervous system cancers such as gliomas disrupt the integrity of the BBB and this compromise is associated with increased tumor growth and invasion of the surrounding brain parenchyma. Because the relationship between glioma-induced BBB breakdown and glioma invasion remains poorly understood, and the host microenvironment can influence tumor cell migration, we used immunohistochemical techniques to characterize tumor associated BBB remodeling. Using an orthotopic xenograft model of glioma, we demonstrate that tumor cells induce specific changes in the composition of the basal lamina and in astrocytic components of the NVU. We suggest that these changes may be essential to understand the capacity of gliomas to regulate BBB integrity and as such, glioma invasion into brain parenchyma.

Expression patterns of glial fibrillary acidic protein (GFAP)‐delta in epilepsy‐associated lesional pathologies

Aims: Glial fibrillary acidic protein (GFAP)‐δ is a novel isoform that differs in its C‐terminal sequence from other GFAP isoforms. Previous studies suggest restriction of expression to the subpial layer, subventricular zone and the subgranular zone astrocytes, with an absence in pathological conditions causing reactive gliosis. GFAP‐δ is speculated to have roles in regulation of astrocyte size and motility and a subpopulation of GFAP‐δ‐positive glia may be multipotent stem cells. The aim of this study was to investigate its expression in common causes of lesion‐related refractory epilepsy. Methods: Hippocampal sclerosis (HS), focal cortical dysplasia (FCD) type IIB, cortical tuberous sclerosis (TSC) lesions, gangliogliomas, grey matter heterotopias and hemimegalencephaly from a wide age range of patients using both surgical and post mortem tissue specimens were studied. Results: GFAP‐δ expression was observed in CA4 and CA1 astrocytes in HS with less frequent labelling in the granule cell layer, even where granule cell dispersion was present. No significant labelling was noted in the subiculum in HS cases or in any subfields in non‐HS epilepsy cases. Balloon cells in FCDIIB and hemimegalencephaly, giant cells in TSC and the astrocytic component of gangliogliomas showed immunoreactivity, colocalizing with conventional GFAP. No neuronal expression for GFAP‐δ was seen in any of the pathologies. Quantitative analysis in 10 FCDIIB and five TSC cases revealed greater numbers of GFAP‐δ‐positive balloon cells than conventional GFAP. There was no GFAP‐δ expression within nodular heterotopia. Conclusions: GFAP‐δ expression patterns in HS overall appears to mirror regional reactive gliosis. It is a useful marker for the demonstration of balloon cells in FCD and TSC, which may be relevant to their abnormal size and localization. The lack of GFAP‐δ within heterotopia supports their composition from cells destined for deeper cortical layers.

A rosette-forming glioneuronal tumor of the spinal cord: the first case of a rosette-forming glioneuronal tumor originating from the spinal cord

Rosette-forming glioneuronal tumors of the fourth ventricle are rare brain tumors, and only 19 such lesions have been previously reported. This report presents the first case of a rosette-forming glioneuronal tumors arising from the spinal cord. A 44-year-old woman presented with a 15-year history of dissociated sensory disturbance of the lower extremities that gradually spread through her upper extremities. She also experienced continuing motor disturbance. Magnetic resonance imaging demonstrated a mass in the cervicothoracic spinal cord that suggested an intramedullary spinal tumor. A total gross resection of the tumor was performed. As is typical of rosette-forming glioneuronal tumors of the fourth ventricle, this spinal cord example manifested neurocytic and astrocytic components. Neurocytic rosettes were detected in the neurocytic component, and the center of rosettes showed positive immunostaining for synaptophysin. The astrocytic component showed characteristic features of a pilocytic astrocytoma, as is often the case in the fourth ventricle examples.

Synaptic mRNAs are modulated by learning

We have recently demonstrated that brain plastic events significantly modify synaptic protein synthesis measured by the incorporation of [(35)S]methionine in brain synaptosomal proteins. Notably, in rats learning a two-way active avoidance task, the local synthesis of two synaptic proteins was selectively enhanced. Because this effect may be attributed to transcriptional modulation, we used reverse transcriptase-polymerase chain reaction methods to determine the content of discrete synaptosomal mRNAs in rats exposed to the same training protocol. Correlative analyses between behavioral responses and synaptosomal mRNA content showed that GAT-1 mRNA (a prevalent presynaptic component) correlates with avoidances and escapes in rat cerebellum, while glial fibrillary acid protein mRNA (an astrocytic component) correlates with freezings in cerebellum and cerebral cortex. These observations support the hypothesis that synaptic protein synthesis may be transcriptionally regulated. The cellular origin of synaptic transcripts is briefly discussed, with special regard to those present at large distances from neuron somas.

A 2-month-old Girl with an Enlarging Lesion of the Nasal Root

A 2-month-old Girl with an Enlarging Lesion of the Nasal Root

Classification of oligodendroglial tumors based on histopathology criteria is a significant predictor of survival – clinical, radiological and pathologic long-term follow-up analysis

The clinical course of oligodendroglial tumors is variable and there is a lack of consensus with regard to precisely diagnose which minimal criteria are required to make a diagnosis of a high-grade oligodendrial tumor. The aims of the present study are to assess pathologic factors with prognostic significance, in addiction to clinical and neuroradiologic variables, in an attempt to identify reproducible histological parameters that are useful for classification of oligodendroglial tumors. 80 oligodendroglial tumors diagnosed between 1977 and 2004 were analyzed. To make a diagnosis of anaplastic tumor we used reproducible parameters: endothelial proliferation, high cellularity, increased mitotic activity and necrosis. Oligoastrocytomas (mixed gliomas) were diagnosed when the astrocytic component was clearly identified as part of the neoplastic cell population. Survival univariate analysis was made constructing survival curves using Kaplan-Meier method and comparing subgroups by log-rank probability test. A Cox regression model was made for multivariable analysis. The histologic diagnosis was low-grade oligodendroglioma in 35 patients (43.75%), anaplastic oligodendroglioma in 23 patients (28.75%), low-grade oligoastrocytoma in 11 patients (13.75%) and anaplastic oligoastrocytoma in 11 patients (13.75%). Median overall survival of the whole series was 80 months. The median overall survival of oligodendroglioma, anaplastic oligodendroglioma, oligoastrocytoma and anaplastic oligoastrocytoma was 148, 105, 47 and 7 months, respectively (p < 0.0001). Multivariate analysis revealed that age, Karnofsky performance status, histological grade and histological diagnosis (oligodendroglioma vs. oligoastrocytoma) were independently associated with survival. Clear cut histopathological criteria (endothelial proliferation, high cellularity, mitotic activity and necrosis) allow to establish different oligodendroglial tumor entities with distinct survival outcome.

Gliosarcoma – Clinico-pathology, Genetics and a Review of Rare Congenital Cases

Congenital brain tumours are rare. In general, they are preferentially located in the supratentorial compartment, and despite the occurrence of low-grade entities, these tumours are associated with a very poor prognosis. When strictly defined, the most common forms of congenital neoplasia are teratomas and astrocytomas. Among the astrocytomas, all grades (World Health Organization [WHO] I–IV) and many of the different subtypes are represented. This includes the most prognostically worrisome ‘diffusely infiltrating’ astrocytomas. Gliosarcomas are a variant of glioblastoma (i.e. WHO grade IV astrocytoma) that exhibits both malignant astrocytic (i.e. glioblastoma) and mesenchymal (i.e. sarcoma) components. Despite their bi-phasic histology, genetic analyses of adult gliosarcoma cases suggest not only a molecular profile similar to glioblastoma, but also a monoclonal histogenesis for the glial and sarcomatous elements. Congenital gliosarcomas are extremely rare, with only a handful of cases being described in the literature. Not surprisingly, therefore, detailed clinical, pathological and genetic data are limited. However, based on a recent analysis of congenital glioblastomas, congenital gliosarcomas may constitute an entity that is genetically and prognostically distinct from adult cases.

Hamartoma in the Medulla Oblongata with Marked Mineral Deposits in a Dog

A mass lesion in the medulla oblongata in a 9-year-old female Golden Retriever was examined pathologically. The medullary mass was 1 to 2 cm in diameter and poorly demarcated. The cut surface was discolored with numerous sand-like materials. Histologically, the mass lesion consisted of complex proliferation of irregularly arranged vessels as well as astrocytes with numerous mineral deposits. The astrocytic components exhibited no apparent anaplastic morphology. The proliferating vessels were either veins with muscle layer and capillaries. A few axons and myelinated fibers were also found in the lesion. The number of ki-67-positive cell nuclei was extremely small, suggesting the poor growth activity of these cells. Based on the findings, the lesion was considered to be a non-neoplastic, hamartomatous change.

Assessment of 1p/19q status by fluorescence in situ hybridization assay: A comparative study in oligodendroglial, mixed oligoastrocytic and astrocytic tumors

Due to overlapping histomorphological features, difference in clinical behavior and treatment response, establishing potential molecular markers to facilitate diagnosis of various genetic subtypes of diffuse gliomas is essential. To analyze 1p/19q status in diffuse gliomas and correlate it with epidermal growth factor receptor (EGFR) and p53 protein expression. 1p/19q status in 43 cases was evaluated by fluorescence in situ hybridization assay. Glial fibrillary acidic protein (GFAP), EGFR and p53 were assessed by immunohistochemistry. Glial fibrillary acidic protein immunopositivity was observed in oligodendrogliomas within minigemistocytes and gliofibrillary oligodendrocytes as perinuclear homogenous blobs. It also highlighted the intermingled reactive astrocytes. Astrocytomas and the astrocytic component of oligoastrocytomas showed a diffuse fibrillary type of staining. 1p and/or 19q loss was seen in 65% (13/20) of oligodendrogliomas and 66.6% (5/9) of mixed oligoastrocytomas. There was one case each of pediatric oligodendroglioma and mixed oligoastrocytoma, none of which showed 1p/19q loss. None of the astrocytomas including two pediatric cases showed this alteration (P < 0.05). p53 was expressed in 57.1% of astrocytomas (8/14), 33% of mixed oligoastrocytomas (3/9) and 10% of oligodendrogliomas (2/20). Majority of oligodendrogliomas (85%; 17/20) and oligodendroglial areas in mixed oligoastrocytomas (77.7%; 7/9) showed a membranous lace-like immunopositivity with EGFR. In contrast, all astrocytomas (Grade II and III) were EGFR negative. Loss of 1p/19q is strongly associated with oligodendroglial phenotype, while astrocytic tumors are more likely to show p53 over-expression. p53 expression and 1p/19q status appear to be mutually exclusive.

Expression patterns of glial fibrillary acidic protein (GFAP)-delta in epilepsy-associated lesional pathologies.

Glial fibrillary acidic protein (GFAP)-delta is a novel isoform that differs in its C-terminal sequence from other GFAP isoforms. Previous studies suggest restriction of expression to the subpial layer, subventricular zone and the subgranular zone astrocytes, with an absence in pathological conditions causing reactive gliosis. GFAP-delta is speculated to have roles in regulation of astrocyte size and motility and a subpopulation of GFAP-delta-positive glia may be multipotent stem cells. The aim of this study was to investigate its expression in common causes of lesion-related refractory epilepsy. Hippocampal sclerosis (HS), focal cortical dysplasia (FCD) type IIB, cortical tuberous sclerosis (TSC) lesions, gangliogliomas, grey matter heterotopias and hemimegalencephaly from a wide age range of patients using both surgical and post mortem tissue specimens were studied. GFAP-delta expression was observed in CA4 and CA1 astrocytes in HS with less frequent labelling in the granule cell layer, even where granule cell dispersion was present. No significant labelling was noted in the subiculum in HS cases or in any subfields in non-HS epilepsy cases. Balloon cells in FCDIIB and hemimegalencephaly, giant cells in TSC and the astrocytic component of gangliogliomas showed immunoreactivity, colocalizing with conventional GFAP. No neuronal expression for GFAP-delta was seen in any of the pathologies. Quantitative analysis in 10 FCDIIB and five TSC cases revealed greater numbers of GFAP-delta-positive balloon cells than conventional GFAP. There was no GFAP-delta expression within nodular heterotopia. GFAP-delta expression patterns in HS overall appears to mirror regional reactive gliosis. It is a useful marker for the demonstration of balloon cells in FCD and TSC, which may be relevant to their abnormal size and localization. The lack of GFAP-delta within heterotopia supports their composition from cells destined for deeper cortical layers.

Galectin‐3: A useful biomarker for differential diagnosis of brain tumors

Galectin-3 (gal-3) is a 31 kDa beta-galactoside-binding lectin that is immunohistochemically expressed in macrophages, lymphocytes, and endothelial cells, and also in some neoplastic cells. Gal-3's expression in and significance to brain tumors has not been fully addressed. Here, we investigated its immunohistochemical expression in 409 cases of surgically resected primary brain tumors, including various glioneuronal tumors, pituitary adenomas, meningiomas and Schwannomas, among others. In normal brain tissues, gal-3 was robustly expressed in normal astrocytes, endothelial cells and macrophages. It showed consistent and diffuse positivity in 100% of the pilocytic astrocytomas, pleomorphic xanthoastrocytomas (PXA), Schwannomas, meningiomas, capillary hemangioblastomas, as well as in ependymomas, but it was completely negative in the diffuse astrocytomas, anaplastic astrocytomas, both low- and high-grades of the oligodendrogliomas, central neurocytomas, and medulloblastomas. Definitely positive but heterogeneous expression was found in various tumors including subependymal giant cell astrocytomas (SEGA), classic glioblastoma multiforme, anaplastic oligoastrocytomas, CNS primitive neuroectodermal tumors (CNS PNETs), and hemangiopericytomas. Eighty percent of small cell glioblstomas were completely negative, but 20% showed heterogeneous positivity for gal-3. Focal positivity for gal-3 was also found in dysembryoplastic neuroepithelial tumors (DNTs) and gangliogliomas, in which the positive cells were the astrocytic component. On the basis of our immunohistochemical data in conjunction with previous reports, we therefore conclude that gal-3 is differentially expressed in various brain tumors, and thereby, is a helpful biomarker in making differential diagnoses, especially in cases where a morphological diagnosis is controversial.

Cortical expression of glial fibrillary acidic protein and glutamine synthetase is decreased in schizophrenia

Altered expression of structural and functional molecules expressed by astrocytes may play a role in the pathophysiology of schizophrenia. We investigated the hypothesis that the astrocytic enzyme glutamine synthetase, involved in maintaining the glutamate–glutamine cycle, and the cytoskeletal molecule glial fibrillary acidic protein (GFAP) are abnormally expressed in schizophrenia. We used Western blot analysis to measure levels of glutamine synthetase and GFAP in several brain regions of subjects with schizophrenia and a comparison group. We found that glutamine synthetase protein expression was significantly decreased in the superior temporal gyrus, and both glutamine synthetase and GFAP were significantly reduced in the anterior cingulate cortex in schizophrenia. Neither molecule demonstrated altered expression in the dorsolateral prefrontal cortex, primary visual cortex, or hippocampus. Chronic treatment with haloperidol did not alter the expression of these molecules in the rat brain, suggesting that our findings are not due to a medication effect. These data support an astrocytic component to the pathophysiology of schizophrenia and suggest that astrocytic molecules involved in enzymatic activity and cytoskeletal integrity may have a role in disease-related abnormalities in this illness.

Glioblastomas: correlation between oligodendroglial components, genetic abnormalities, and prognosis

It has been demonstrated that a small percentage (approximately 15%) of glioblastomas (GBM) presents an oligodendroglial component with a variable frequency of chromosome 1p and 19q deletions, the genetic alteration related to chemotherapy response and longer survival in oligodendrogliomas. There is a growing interest in investigating 1p and 19q losses in hybrid gliomas and their impact on prognosis. A series of 88 GBMs was investigated regarding 1p and/or 19q losses, 24 with oligodendroglioma-like areas, using quantitative microsatellite analysis and/or fluorescent in situ hybridization. When present, the oligodendroglial and astrocytic components were independently investigated. Clinical data, histology, and 1p/19q status were correlated. Tumors with oligodendroglial components showed three cases each of 1p or 19q loss and one with combined 1p/19q loss. No difference in 1p or 19q status was observed between the oligodendroglial and astrocytic components. Conventional GBM demonstrated isolated 1p loss in four cases and 19q loss in five. No association was seen between 1p/19q status and histology. Deletions at 1p and/or 19q were infrequent in GBMs with oligodendroglial components. Despite the hybrid phenotype, the pattern of genetic changes at 1p and 19q was not different from that usually observed in conventional GBMs, nor did it show any correlation with survival.

Isolation and characterization of stem cell-like precursor cells from primary human anaplastic oligoastrocytoma

A small population of stem cell-like precursors in solid tumors are linked to histological composition, progression, angiogenesis, metastasis, recurrence and drug resistance of a variety of malignant tumors. Oligoastrocytoma is the most common brain mixed glioma composed of mixed cells of oligodendroglial and astrocytic phenotypes. Identification and characterization of stem cell-like precursors in oligoastrocytoma may shed light on the oncogenesis of this unique type of tumor and assist in the design of novel therapeutic strategy. Here, tumor stem cell-like precursors were identified from primary human anaplastic oligoastrocytomas by labeling of the tumor sections with nestin and CD133. Tumor cells were cultured in vitro in stem cell medium with growth factors and the capacity of the surviving stem cell-like precursors to form tumor spheres was tested. The tumor spheres were further injected subcutaneously into nude mice to observe the contribution of stem cell-like precursors to histological composition and tumor progression. We found that primary human oligoastrocytoma tissues contained nestin+/CD133+ stem cell-like precursors. These cells differentiated into tumor cells with both oligodendroglial and astrocytic characteristics and formed tumor spheres in vitro, which upon implantation in nude mice, grew into tumor nodules containing nestin +/CD133+ cells at levels higher than in the primary tumor tissues. This study revealed for the first time that anaplastic human oligoastrocytomas contained stem cell-like precursors, which exhibit neural stem cell properties with tumorigenicity. These stem cell-like precursors may be responsible for the oligodendroglial and astrocytic components of human oligoastrocytoma and should be considered as therapeutic targets.

Expression of Oligodendroglial and Astrocytic Lineage Markers in Diffuse Gliomas

The phenotypic heterogeneity of astrocytic and oligodendroglial tumor cells complicates establishing accurate diagnostic criteria, and lineage-specific markers would facilitate diagnosis of glioma subtypes. Based on data from the literature and from expression microarrays, we selected molecules relevant to gliogenesis and glial lineage specificity and then used immunohistochemistry to assess expression of these molecules in 55 diffuse gliomas, including 8 biphasic oligoastrocytomas, 21 oligodendrogliomas (all with 1p/19qloss), 21 astrocytomas, and 5 glioblastomas. For the astrocytic lineage markers (GFAP, YKL-40, and ApoE), GFAP expression was significantly higher in the astrocytic component of oligoastrocytomas compared with the oligodendroglial part; similar patterns were detected for YKL-40 and ApoE, although the differences were not significant. GFAP, YKL-40, and ApoE reliably distinguished grade II-III oligodendrogliomas from grade II-IV astrocytomas (p < 0.0001, p = 0.002, and p < 0.0001, respectively). Among the oligodendroglial lineage markers (Olig2, Sox10, ASCL1, and NKX2-2), ASCL1 and NKX2-2 displayed significantly different immunostaining between oligodendrogliomas and astrocytomas (p = 0.017 and 0.004, respectively), but none clearly differentiated between the 2 glial populations of oligoastrocytomas. In addition to GFAP, therefore, YKL-40, ApoE, ASCL1, and NKX2-2 represent promising tumor cell markers to distinguish oligodendrogliomas from astrocytomas.

Genetically distinct astrocytic and oligodendroglial components in oligoastrocytomas

Oligoastrocytomas are glial tumours consisting of a mixture of neoplastic astrocytic and oligodendroglial cells. Genetic alterations of oligoastrocytomas include loss of heterozygosity of chromosomes 1p and/or 19q (LOH 1p/19q), typically occurring in oligodendrogliomas, and mutations of TP53, frequently occurring in astrocytomas. To investigate whether these neoplastic cell types in oligoastrocytomas have different genetic profiles, we examined the two different components of oligoastrocytomas in comparison with the histological diagnosis of the specific tumour area for LOH 1p/19q and TP53 mutations by using microdissection technique. We found a variety of lost markers for 1p and 19q, and the presence of two different TP53 mutations in the tumour samples. In the majority of cases (9/11), the oligodendroglial and astrocytic components of an individual oligoastrocytoma displayed the same genotype. We present two cases of biphasic oligoastrocytomas with aberrant findings, suggesting the coexistence of genetically and morphologically distinct tumour cell clones in these tumours. In one case, the oligodendroglial part of the tumour showed LOH19q, whereas the astrocytic part showed TP53 mutation (codon 273). In another case, we found LOH 1p/19q in the oligodendroglial component, but two retained areas on chromosome 1p in the astrocytic component of the tumour. No evidence was found for the coexistence of tumour cells with the two genotypical changes within the same morphological region of one individual tumour. The two cases of biphasic oligoastrocytomas in our sample that display a different genotype in the astrocytic and oligodendroglial part of the tumour show that different components of an oligoastrocytoma may be derived from different cell clones during neoplastic transformation.

Serine racemase protein expression in cortex and hippocampus in schizophrenia

Evidence of glutamatergic dysfunction in schizophrenia associated with the N-methyl-D-aspartate receptor has historically demonstrated changes primarily attributable to neurons. We propose an astrocytic component to N-methyl-D-aspartate receptor dysfunction in this illness. We studied the expression of serine racemase, an astrocytic enzyme which synthesizes the N-methyl-D-aspartate receptor coagonist D-serine, using Western blot analysis in postmortem hippocampus and cortex in schizophrenia and a comparison group. We found increased expression in the hippocampus in schizophrenia. This is the first study to demonstrate alterations in schizophrenia of an astrocytic enzyme responsible for synthesizing a neuromodulator, and further evidence that astrocytes may play a direct role in N-methyl-D-aspartate receptor dysfunction in schizophrenia.