Neoplastic Astrocytes Research Articles

Cerebral granular cell tumor

Intracerebral granular cell tumors (GCTs) are a rare finding. We report here on a case of cerebral GCT in a 47-year-old man who suffered with severe headache. The tumor appeared as a relatively well-defined, enhancing mass at the periventricular white matter of the left occipital lobe of the brain. Histologically, the tumor was entirely composed of granular cells. Some of the tumor cells showed peripherally accentuated cytoplasmic granules with central clearing, which produced a unique "targetoid" appearance. The granular cells of the current case were positive for neuron-specific enolase (NSE), S-100 protein, GFAP, vimentin, CD 68, lysozyme, and alpha-1-antitrypsin. These wide immunoexpressions were not observed for the previously reported cerebral GCTs. Interestingly, this case showed "targetoid" or "reversed targetoid" immunoreactive patterns in NSE, CD68, GFAP, and vimentin. Despite these wide immunoexpressions and the lack of any association with astrocytoma, the histogenesis of cerebral GCTs is still suggested to be of a glial origin, based on the tumor location, the GFAP positivity and the ultrastructural findings, of which the latter showed intermediate filaments, and these are reminiscent of neoplastic astrocytes.

WT1 Expression Distinguishes Astrocytic Tumor Cells from Normal and Reactive Astrocytes

Particularly in small brain biopsies, it might be difficult to distinguish reactive astrogliosis from low-grade or infiltration zones of high-grade astrocytomas. So far no immunohistochemical marker allows a reliable distinction. Recently, the over-expression of Wilms' tumor gene product WT1 was reported in astrocytic tumor cells. However, no sufficient data on WT1 expression in normal or reactive astrocytes are available. Therefore, we investigated WT1 expression in paraffin-embedded brain sections from 28 controls, 48 cases with astrogliosis of various etiology and 219 astrocytomas [World Health Organization (WHO) grades I-IV] by immunohistochemistry. In normal brains and in astrogliosis, expression of WT1 was restricted to endothelial cells. In astrocytomas, WT1-positive tumor cells were found in pilocytic astrocytomas (66.7% of cases), diffuse astrocytomas (52.7%) WHO grade II (52.7%), anaplastic astrocytomas (83.4%) and glioblastomas (98.1%). Overall, the majority of all astrocytic neoplasms (84.5%) expressed WT1. Establishing a cut-off value of 0% immunoreactive tumor cells served to recognize neoplastic astrocytes with 100% specificity and 68% sensitivity and was associated with positive and negative predictive values of 1 and 0.68, respectively. Therefore, WT1 expression in astrocytes indicates a neoplastic origin and might represent an important diagnostic tool to differentiate reactive from neoplastic astrocytes by immunohistochemistry.

Gene expression analyses of grade II gliomas and identification of rPTPβ/ζ as a candidate oligodendroglioma marker

Grade II gliomas are morphologically and clinically heterogeneous tumors for which histopathological typing remains the major tool for clinical classification. To what extent the major histological subtypes - astrocytomas, oligodendrogliomas, and oligoastrocytomas - constitute true biological entities is largely unresolved. Furthermore, morphological classification is often ambiguous and would be facilitated by specific subtype markers. In this study, 23 grade II gliomas were expression-profiled and subjected to hierarchical clustering. All six oligodendrogliomas were grouped together in one of two major clusters; a significant correlation was thus observed between gene expression and histopathological subtype. Supervised analyses were performed to identify genes differentiating oligodendrogliomas from other grade II tumors. In a leave-one-out test using 10 features for classification, 20 out of 23 tumors were correctly classified. Among the most differentially expressed genes was rPTPbeta/zeta. The expression of the rPTP beta/zeta protein in oligodendrogliomas and astrocytomas was further validated by immunohistochemistry in an independent set of tumors. All 11 oligodendrogliomas of this set displayed strong staining. In contrast, neoplastic astrocytes were mostly negative for rPTPbeta/zeta staining. In summary, this study demonstrates a correlation between gene expression pattern and histological subtype in grade II gliomas. Furthermore, the results from the immunohistochemical analyses of rPTPbeta/zeta expression should prompt further evaluation of this protein as a novel oligodendroglioma marker.

A 42‐YEAR‐OLD MAN WITH A DENSELY VASCULAR SPINAL MASS

A 42-year-old man was admitted to the neurosurgery department because of paraparesis and sensory deficits of both feet. A solitary exophytic lesion of the thoracic spine was seen on MRI, and angiography further revealed the presence of feeding and draining vessels and intra-lesional shunting. The preoperative diagnosis was spinal hemangioblastoma. A gross total resection was performed. By histological examination, the lesion was a tumor composed of neoplastic astrocytes and cells immunopositive for neuronal markers and CD34. The neuronal subpopulation was quite polymorphous and consisted of large anaplastic neurons including binucleate forms and smaller immature looking cells. Vessels were abundant and showed dysplastic changes such as sclerosis, calcium incrustations and extreme dilatation. Because of necrosis and marked proliferative activity, the tumor was considered a de novo malignant ganglioglioma (GG). In conformity with the diagnosis of malignancy, the tumor gave rise to extensive cerebrospinal deposits in the intracranial and spinal compartments 12 months post-diagnosis. De novo malignant GG of the spine are very rare tumors of which few cases are on record. Interestingly, in our case the rich malformative vasculature and the corresponding angiographic image were most compatible with descriptions of "mixed" angiogliomas. The diagnosis of spinal GGs should rely on both histologic hallmarks and unequivocal immunopositivity for several neuronal markers because of reported aberrant expression of synaptophysin by non-neoplastic spinal neurons.

In vitro identification and functional characterization of glial precursor cells in human gliomas

Human gliomas including astrocytomas and oligodendrogliomas are defined as being composed of neoplastic astrocytes and oligodendrocytes respectively. Here, on the basis of in vitro functional assays, we show that gliomas contain a mixture of glial progenitor cells and their progeny. We have set up explant cultures from pilocytic astrocytomas, glioblastomas and oligodendrogliomas and studied antigens that characterize glial lineage, from the precursor cells (glial restricted precursors and oligodendrocyte-type2-astrocyte/oligodendrocyte precursor cells expressing the A2B5 ganglioside) to the differentiated cells (oligodendrocyte and type-1 and type-2 astrocytes). All tumoral explants contain A2B5+ cells and can generate migrating cells with distinctive functional properties according to glioma subtypes. In pilocytic astrocytomas, very few migrating cells are dividing and can differentiate in type-2 astrocytes or towards the oligodendrocyte lineage. In glioblastomas, most migrating cells are dividing, express A2B5 or glial fibrillary acid protein (GFAP) and can generate oligodendrocytes and type-1 and type-2 astrocytes in appropriate medium. Oligodendroglioma explants are made by actively dividing glial precursor cells expressing A2B5 or PSA-NCAM. Only few cells can migrate and differentiation towards oligodendrocyte lineage does not occur. Isolated A2B5+ cells from both glioblastomas and oligodendrogliomas showed similar genetic alterations as the whole tumour. Therefore, pilocytic astrocytomas contain slowly dividing oligodendrocyte-type2-astrocyte/oligodendrocyte precursor cells in keeping with their benign behaviour whereas both glioblastomas and oligodendrogliomas contain neoplastic glial restricted precursor cells. In oligodendrogliomas, these cells are trapped in undifferentiated and proliferating state. The precursor cells properties present in gliomas give new insight into their histogenesis and open up new avenues for research in the field of gliomagenesis.

Differential expression ofHOX genes in neoplastic and non-neoplastic human astrocytes

HOX genes are a large family of regulatory genes implicated in the control of developmental processes. HOX genes are involved in malignant transformation and progression of different types of tumour. Despite intensive efforts to delineate the expression profiles of HOX genes in other cell types, nothing is known regarding the global expression profile of these genes in normal human astrocytes and astrocytomas. The present study has analysed the expression profile of the 39 class I HOX genes in normal human astrocytes (NHA and E6/E7), two well-established glioblastoma cell lines (U-87 MG and U-1242-MG), as well as neoplastic (WHO grades II/III and IV) and non-neoplastic temporal lobe specimens with hippocampal sclerosis and medically intractable epilepsy. RT-PCR, quantitative real-time PCR, immunocytochemistry, and western blot analyses revealed differential expression of nine HOX genes (A6, A7, A9, A13, B13, D4, D9, D10, and D13) in normal human astrocytic cell lines and non-neoplastic temporal lobe specimens. The data show that HOX genes are differentially expressed in neoplastic and non-neoplastic astrocytes and that multiple HOX genes are overexpressed in glioblastoma cell lines, astrocytomas (II/III), and glioblastoma multiforme. The differential expression of HOX genes in normal and neoplastic astrocytes suggests a role for these genes in brain tumourigenesis.

A Report of a Desmoplastic Ganglioglioma in a 12-year-old Girl with Review of the Literature

Desmoplastic infantile ganglioglioma is a supratentorial tumor that typically occurs in infants below the age of 24 months. Rare tumors with the same radiological and histological characteristics have been described in older subjects. We report a case of desmoplastic ganglioglioma in a 12-year-old girl with a 13 years follow-up. The patient presented with an inaugural generalized seizure. CT scan demonstrated a large superficial parieto-occipital mass, attached to the dura with solid and cystic components. Surgical resection was macroscopically complete. No adjuvant treatment was given. Thirteen years after surgery, the patient is symptom free. Histological examination revealed a pleomorphic tumor involving the meningeal space and the cortex. Meningeal portion was made of neoplastic astrocytes enmeshed in a dense network of connective tissue. The cortical component showed abnormal neurons, tumoral astrocytes and small foci of poorly differentiated cells with rare mitoses. Our observation and the seven others found in the literature indicate that desmoplastic gangliogliomas can occur in children and even in young adults. Despite some worrisome radiological and histological features, these tumors should not be misdiagnosed as malignant glioma. Like infantile cases, non-infantile desmoplastic gangliogliomas seem to have a favorable prognosis without additional therapy, if a total surgical resection can be performed.

Gliomatosis Cerebri and Pituitary Adenoma: Case Report and Literature Review

The diagnosis of Gliomatosis cerebri (GC) is known to be difficult and is still a matter of debate. We describe an in vivo case of GC associated with a pituitary tumor. A 47-year-old woman presented with short-term memory loss. A MRI revealed the presence of a pituitary enhancing tumor and a diffuse lesion involving the brain. A left pterional craniotomy with partial temporal lobectomy and removal of the pituitary lesion were performed in order to obtain diagnosis. The histological analyses showed a pituitary non-functioning tumor and a GC consisting of neoplastic oligodendrocytes and astrocytes. Both lesions showed nuclear immunoreactivity for progesterone receptors (PGr) and estrogen receptors (EGr). This result could suggest there is a common receptor substrate in these tumors. In this case hormones could constitute a common step in tumorigenesis of both lesions.

Id4 and FABP7 are preferentially expressed in cells with astrocytic features in oligodendrogliomas and oligoastrocytomas

BackgroundOligodendroglioma (ODG) and oligoastrocytoma (OAC) are diffusely infiltrating primary brain tumors whose pathogenesis remains unclear. We previously identified a group of genes whose expression was inversely correlated with survival in a cohort of patients with glioblastoma (GBM), and some of these genes are also reportedly expressed in ODG and OAC. We examined the expression patterns and localization of these survival-associated genes in ODG and OAC in order to analyze their possible roles in the oncogenesis of these two tumor types.MethodsWe used UniGene libraries derived from GBM and ODG specimens to examine the expression levels of the transcripts for each of the 50 GBM survival-associated genes. We used immunohistochemistry and cDNA microarrays to examine expression of selected survival-associated genes and Id4, a gene believed to control the timing of oligodendrocyte development. The expression of FABP7 and Id4 and the survival of patients with ODG and OAC were also analyzed.ResultsTranscripts of most survival-associated genes as well as Id4 were present in both GBM and ODG tumors, whereas protein expression of Id4 and one of the survival-associated genes, brain-type fatty acid-binding protein (FABP7), was present in cells with astrocytic features, including reactive and neoplastic astrocytes, but not in neoplastic oligodendrocytes. Id4 was co-expressed with FABP7 in microgemistocytes in ODG and in neoplastic astrocytes in OAC. Id4 and FABP7 expression, however, did not correlate with the clinical outcome of patients with ODG or OAC tumors.ConclusionExpression of Id4 and some of our previously identified GBM survival-associated genes is present in developing or mature oligodendrocytes. However, protein expression of Id4 and FABP7 in GBM, ODG, and OAC suggests that this group of functionally important genes might demonstrate two patterns of expression in these glioma subtypes: one group is universally expressed in glioma cells, and the other group of genes is expressed primarily in neoplastic astrocytes but not in neoplastic oligodendrocytes. Differential protein expression of these two groups of genes in ODG and OAC may be related to the cellular origins and the histological features of the neoplastic cells.

Phorbol 12-Myristate 13-Acetate Induces Epidermal Growth Factor Receptor Transactivation via Protein Kinase Cδ/c-Src Pathways in Glioblastoma Cells

Both the epidermal growth factor receptor (EGFR) and protein kinase C (PKC) play important roles in glioblastoma invasive growth; however, the interaction between the EGFR and PKC is not well characterized in glioblastomas. Treatment with EGF stimulated global phosphorylation of the EGFR at Tyr(845), Tyr(992), Tyr(1068), and Tyr(1045) in glioblastoma cell lines (U-1242 MG and U-87 MG). Interestingly, phorbol 12-myristate 13-acetate (PMA) stimulated phosphorylation of the EGFR only at Tyr(1068) in the two glioblastoma cell lines. Phosphorylation of the EGFR at Tyr(1068) was not detected in normal human astrocytes treated with the phorbol ester. PMA-induced phosphorylation of the EGFR at Tyr(1068) was blocked by bisindolylmaleimide (BIM), a PKC inhibitor, and rottlerin, a PKCdelta-specific inhibitor. In contrast, Go 6976, an inhibitor of classical PKC isozymes, had no effect on PMA-induced EGFR phosphorylation. Furthermore, gene silencing with PKCdelta small interfering RNA (siRNA), siRNA against c-Src, and mutant c-Src(S12C/S48A) and treatment with a c-Src inhibitor (4-amino-5-(4-chlorophenyl)-7-(t-butyl) pyrazolo[3,4-d]pyrimidine) abrogated PMA-induced EGFR phosphorylation at Tyr(1068). PMA induced serine/threonine phosphorylation of Src, which was blocked by both BIM and rottlerin. Inhibition of the EGFR with AG 1478 did not significantly alter PMA-induced EGFR Tyr(1068) phosphorylation, but completely blocked EGF-induced phosphorylation of the EGFR. The effects of PMA on MAPK phosphorylation and glioblastoma cell proliferation were reduced by BIM, rottlerin, the MEK inhibitor U0126, and PKCdelta and c-Src siRNAs. Taken together, our data demonstrate that PMA transactivates the EGFR and increases cell proliferation by activating the PKCdelta/c-Src pathway in glioblastomas.

Intermediate filament protein synemin is present in human reactive and malignant astrocytes and associates with ruffled membranes in astrocytoma cells

Synemin, a very unique type VI intermediate filament (IF) protein, exhibits alternative splice variants termed alpha and beta. Unlike other IF proteins, synemin binds to actin-associated proteins, including alpha-actinin, vinculin, and alpha-dystrobrevin. Our previous work has demonstrated the presence of synemin in differentiating astrocytes. In this study, we have examined the presence of synemin in human astrocytes under pathological conditions, using rabbit antibodies raised against the C-terminal domain of human synemin produced in bacteria. Western blotting shows that astrocytic tumors contain greater amounts of alpha-synemin than do normal brain tissues. These tumors also contain beta-synemin, which is not detectable in normal brain. Immunohistochemistry demonstrates that, while synemin is present in normal adult brain only in vascular smooth muscle cells, it is newly synthesized by reactive and neoplastic astrocytes. Alpha- and beta-Synemins have also been detected by Western blotting and polymerase chain reaction in several human glioblastoma cell lines. In these cell lines, surprisingly, synemin is associated with ruffled membranes in addition to being distributed along the IF network. In ruffled membranes, synemin was found to co-localize with alpha-actinin. This unusual cellular localization for an IF protein is maintained after nocodazole-induced perinuclear coiling of the vimentin IF network. In addition, immunoprecipitation experiments demonstrate that synemin forms a complex with alpha-actinin in glioblastoma cells. Taken together with synemin localization within ruffled membranes, this finding suggests that synemin plays a role in motility of glioblastoma cells.

Desmoplastic infantile ganglioglioma: A rare tumor with an unusual presentation

Desmoplastic infantile ganglioglioma (World Health Organization grade I) is a rare neoplasm. Despite their common large size and spectacular radiologic and histologic features, the prognosis after surgical resection is good. We present a new case of this tumor in a 14-month-old boy with a recent history of intracranial hypertension. Magnetic resonance imaging revealed a large tumor involving the left collateral trigone with dilatation of the lateral ventricles. Surgery revealed two separate solid tumors: one in the left falco-tentorial region and the other in the left rolandic area. Microscopic examination showed a proliferation of neoplastic astrocytes in reticulin-rich desmoplastic stroma associated with scattered ganglion cells. One year after surgery follow-up magnetic resonance imaging did not show tumor progression.

Vascular endothelial growth factor (VEGF) receptor neuropilin-1's distribution in astrocytic tumors.

Neuropilin-1 is a VEGF165- and semaphorin receptor expressed by endothelial cells and tumor cells. The specific function of neuropilin-1 is not fully known, but in the developing nervous system neuropilin, as a semaphorin receptor, has been shown to influence neuronal guidance. The expression of neuropilin-1 was studied in low-grade and high-grade astrocytic tumors, the latter characterized by extensive angiogenesis. We examined 20 low-grade astrocytomas (WHO grade II) and 46 glioblastomas (WHO grade IV) immunohistochemically for neuropilin-1, p53 and EGFR. The glioblastomas were according to the p53 and EGFR expression classified as 35 primary--de novo--glioblastomas, 9 secondary glioblastomas, and 2 uncertain cases. Furthermore, the presence of mast cells was evaluated to search for any potential function in angiogenesis. The glioblastomas expressed neuropilin-1 in the endothelial cells of the proliferating vessels and the majority of the glioblastomas had immunoreactive neoplastic astrocytes, with no difference between the glioblastoma subgroups. Six out of twenty of the low-grade astrocytomas were negative in the endothelial cells and 8 out of 20 in the tumor cells for neuropilin-1. Mast cells were observed in the collagen matrix around larger vessels in the leptomeninges, but not adjacent to malignant tumor vessels or as part of the tumor process itself. Increased expression of neuropilin-1 is shown in endothelial cells and in neoplastic astrocytes of glioblastomas. Less neuropilin-1 expression is found in about half of the low-grade astrocytomas in both neoplastic astrocytes and endothelial cells. The results suggest a correlation between neuropilin-1 and vascularity in human astrocytic tumors and a possible role for neuropilin-1 as a receptor for VEGF-induced angiogenesis.

Regulators of G-protein signaling 3 and 4 (RGS3, RGS4) are associated with glioma cell motility.

Diffuse brain invasion is a major reason for poor prognosis of glioma patients. The molecular mechanisms underlying infiltration are different from those of other cancer types. To detect genes associated with glioma invasion, highly migratory clones were selected from U373MG glioma cells and from primary glioblastoma cells, and the gene expression pattern of these "fast" cells was compared with that of the original ("slow") cells using oligonucleotide microarrays comprising 12,625 genes. A total of 28 genes were differently expressed in both primary and established cell populations, including 19 genes that were upregulated and 9 that were downregulated in fast cells. Most of these genes have not been linked to glioma invasion so far. Specifically, differentially expressed genes included those encoding extracellular matrix components (COL16A1, DPT), proteases (CATD, PRSS11), cytokines (MDK, IL8), transport proteins (SLC1A3, ATP10B), cytoskeleton constituents (ACTA2, ACTSG, NEFL), DNA repair enzymes (WRN, ADPRTL2), and G-protein signaling components (GNA12, RGS3, RGS4). RGS3 and RGS4, which are homologs of the Drosophila glia gene loco, were further functionally analyzed. U373MG glioma cell clones overexpressing RGS3 or RGS4 showed an increase of both adhesion and migration. These findings expand the spectrum of possible molecular pathways underlying the invasion of neoplastic astrocytes. Specifically, they suggest that RGS proteins and G-protein-mediated signal transduction are evolutionary conserved functional players.

AMOG/beta2 and glioma invasion: does loss of AMOG make tumour cells run amok?

The beta2 subunit of Na,K-ATPase, initially described as adhesion molecule on glia (AMOG), has been shown to mediate neurone-astrocyte adhesion as well as neural cell migration in vitro. We have investigated the expression of AMOG/beta2 in human gliomas and its effect on glioma cell adhesion and migration. Compared to normal astrocytes of human brain, AMOG/beta2 expression levels of neoplastic astrocytes were down-regulated in biopsy specimens and inversely related to the grade of malignancy. One rat and four human glioma cell lines showed complete loss of AMOG. To investigate the function of AMOG/beta2, its expression was re-established by transfecting an expression plasmid into AMOG/beta2-negative C6 rat glioma cells. In vitro assays revealed increased adhesion and decreased migration on matrigel of AMOG/beta2-positive cells as compared to their AMOG/beta2-negative counterparts. We conclude that increasing loss of AMOG/beta2 during malignant progression parallels and may underlie the extensive invasion pattern of malignant gliomas.

Chloride/anion channels in glial cell membranes

At least seven different chloride/anion currents have now been identified in astrocytes, oligodendrocytes/Schwann cells, and microglia. Only for two of these currents is the corresponding gene known. One of these genes is not encoding for a chloride channel, but for a class of mitochondria-like pores also found in cell membranes. Astrocytes and oligodendrocytes differ in their resting properties: astrocytes accumulate chloride but do not have a significant permeability. Oligodendrocytes have a close to passive distribution and a significant permeability. Under certain circumstances, astrocytes can express a resting chloride conductance. Reactive and neoplastic astrocytes as well as astrocytes with an altered shape exhibit a resting conductance. The function of these channels certainly involves volume regulation. Other possible functions are potassium homeostasis, migration, proliferation (in microglia), and involvement in spreading depression waves. Of greatest interest are two phenomena discovered in situ: The ClC-2 channel is only found in astrocytic endfeet near blood capillaries adjacent to neuronal GABA(A) receptors. In the supraoptic nucleus of the hypothalamus, there is an osmosensitive astrocytic taurine release. This released taurine interacts with glycine receptors in neighboring neurons, causing inhibition. It is assumed that with the future availability of more in situ, rather than in vitro, studies, an increased number of such complex interactions between glial cells, neurons, and blood vessels will be discovered.

Galectin-1 modulates human glioblastoma cell migration into the brain through modifications to the actin cytoskeleton and levels of expression of small GTPases.

We show that high-grade astrocytic tumors with high levels of galectin-1 expression are associated with dismal prognoses. The immunohistochemical analysis of galectin-1 expression of human U87 and U373 glioblastoma xenografts from the brains of nude mice revealed a higher level of galectin-1 expression in invasive areas rather than non-invasive areas of the xenografts. Nude mice intracranially grafted with U87 or U373 cells constitutively expressing low levels of galectin-1 (by stable transfection of an expression vector containing the antisense mRNA of galectin-1) had longer survival periods than those grafted with U87 or U373 cells expressing normal levels of galectin-1. Galectin-1 added to the culture media markedly and specifically increased cell motility levels in human neoplastic astrocytes. These effects are related to marked modifications in the organization of the actin cytoskeleton and the increase in small GTPase RhoA expression. All the data obtained indicate that galectin-1 enhances the migratory capabilities of tumor astrocytes and, therefore, their biological aggressiveness.

Targeting protein kinase C: new therapeutic opportunities against high-grade malignant gliomas?

A large body of evidence suggests that the abnormal phenotype of neoplastic astrocytes, including their excessive proliferation rate and high propensity to invade surrounding tissues, results from mutations in critical genes involved in key cellular events. These genetic alterations can affect cell-surface-associated receptors, elements of signaling pathways, or components of the cell cycle clock, conferring a gain or a loss of relevant metabolic functions of the cells. The understanding of such phenomena may allow the development of more efficacious forms of cancer treatment. Examples are therapies specifically directed against overexpressed epidermal growth factor receptor, hyperactive Ras, excessively stimulated Raf-1, overproduced ornithine decarboxylase, or aberrantly activated cyclin-dependent kinases. The applicability of some of these approaches is now being assessed in patients suffering from primary malignant central nervous system tumors that are not amenable to current therapeutic modalities. Another potentially useful therapeutic strategy against such tumors involves the inhibition of hyperactive or overexpressed protein kinase C (PKC). This strategy is justified by the decrease in cell proliferation and invasion following inhibition of the activity of this enzyme observed in preclinical glioma models. Thus, interference with PKC activity may represent a novel form of experimental cancer treatment that may simultaneously restrain the hyperproliferative state and the invasive capacity of high-grade malignant gliomas without inducing the expected toxicity of classical cytotoxic agents. Of note, the experimental use of PKC-inhibiting agents in patients with refractory high-grade malignant gliomas has indeed led to some clinical responses. The present paper reviews the current status of the biochemistry and molecular biology of PKC, as well as the possibilities for developing novel anti-PKC-based therapies for central nervous system malignancies.

Fraction of gemistocytic astrocytes and immunoexpression of p53 protein in astrocytomas grade II and III (WHO)

Twenty-two patients with astrocytomas, grade II or III WHO, were studied from 1990 to 1998. In all cases, histopathology showed that the astrocytomas had a gemistocytic component. The aims of this study were to establish the fraction of gemistocytic astrocytes, to investigate p53 protein immunoexpression and to evaluate correlations between these two parameters with the tumour outcome. Tumor cells were quantified at high-power magnification (x400). At least 1000 neoplastic cells (small neoplastic astrocytes plus gemistocytes) were counted in each specimen. The percentage of gemistocytes was defined as the gemistocytic index. Nuclear expression of p53 protein was evaluated in neoplastic astrocytes and gemistocytes. Both the frequency (7/22) as well the p53 immunoexpression indices in gemistocytes, regardless of the grade of the astrocytomas, were inferior from those reported in the literature. No correlation was found between the gemistocytic indices and the p53 immunoexpression.

Aberrant Localization of the Neuronal Class III b-Tubulin in Astrocytomas A Marker for Anaplastic Potential

c Background.—The class III b-tubulin isotype (bIII) is widely regarded as a neuronal marker in development and neoplasia. In previous work, we have shown that the expression of bIII in neuronal/neuroblastic tumors is differentiation dependent. In contrast, the aberrant localization of this isotype in certain nonneuronal neoplasms, such as epithelial neuroendocrine lung tumors, is associated with anaplastic potential. Objective.—To test the generality of this observation, we investigated the immunoreactivity profile of bIII in astrocytomas. Design.—Sixty archival, surgically excised astrocytomas (8 pilocytic astrocytomas, WHO grade 1; 18 diffuse fibrillary astrocytomas, WHO grade 2; 4 anaplastic astrocytomas, WHO grade 3; and 30 glioblastomas, WHO grade 4), were studied by immunohistochemistry using anti-bIII monoclonal (TuJ1) and polyclonal antibodies. A monoclonal antibody to Ki-67 nuclear antigen (NC-MM1) was used as a marker for cell proliferation. Antibodies to glial fibrillary acidic protein (GFAP) and BM89 synaptic vesicle antigen/synaptophysin were used as glial and neuronal markers, respectively. Results.—The bIII immunoreactivity was significantly greater in high-grade astrocytomas (anaplastic astrocytomas and glioblastomas; median labeling index [MLI], 35%; interquartile range [IQR], 20%‐47%) as compared with diffuse fibrillary astrocytomas (MLI, 4%; IQR, 0.2%‐21%) (P , .0001) and was rarely detectable in pilocytic astrocytomas (MLI, 0%; IQR, 0%‐0.5%) (P , .0001 vs high-grade astrocytomas; P , .01 vs diffuse fibrillary astrocytomas). A highly significant, grade-dependent relationship was observed between bIII and Ki-67 labeling and malignancy, but this association was stronger for Ki-67 than for bIII (bIII, P , .006; Ki-67, P , .0001). There was co-localization of bIII and GFAP in neoplastic astrocytes, but no BM89 synaptic vesicle antigen/synaptophysin staining was detected. Conclusions.—In the context of astrocytic gliomas, bIII immunoreactivity is associated with an ascending gradient of malignancy and thus may be a useful ancillary diagnostic marker. However, the significance of bIII-positive phenotypes in diffuse fibrillary astrocytomas with respect to prognostic and predictive value requires further evaluation. Under certain neoplastic conditions, bIII expression is not neuron specific, calling for a cautious interpretation of bIII-positive phenotypes in brain tumors. (Arch Pathol Lab Med. 2001;125:613‐624)