Differentiation and anaplasia in central neuroepithelial tumors

Anaplasia and Heterogeneity of Gfap Expression in Gliomas

GFAP (glial fibrillary acidic protein) distribution was investigated in selected areas of glioblastomas and astrocytomas. The proliferating cell population of glioblastomas was GFAP negative and contained many mitoses which were also negative. The old, deeply located areas were composed of cells with visible cytoplasm, intensely GFAP-positive; mitoses in these areas were both GFAP-positive and negative. GFAP-positive reactive astrocytes, once trapped in the tumor, were no longer distinguishable from positive tumor cells. They sometimes contained mitoses. In astrocytoma, anaplasia was due to the development of a GFAP-negative population with negative mitoses. The problem of dedifferentiation and differentiation of malignant gliomas in discussed taking into account the possiblity that malignancy may be due to increasing mutation rates of tumors. The problem of redifferentiation of already dedifferentiated cells is also discussed.

Reactive Astrocytes in the Morphologic Composition of Peripheral Areas of Gliomas

The participation of reactive astrocytes in the morphologic composition of peripheral areas of 25 gliomas was investigated. Reactive astrocytes were studied by the immunohistochemical demonstration of glial fibrillary acidic protein and vimentin. Reactive astrocytes were more abundant around malignant gliomas than around well-differentiated astrocytomas. They underwent modifications when entrapped within the tumor proliferation and became indistinguishable from tumor astrocytes. Mitoses occurred in both types of cells. Reactive astrocytes did participate in the cell composition of gliomas. They might have contributed to tumor growth. Practically, their occurrence might lead to an erroneous diagnosis when small fragments of tissue are examined.

Unique expression and localization of aquaporin- 4 and aquaporin-9 in murine and human neural stem cells and in their glial progeny

Aquaporins (AQP) are water channel proteins that play important roles in the regulation of water homeostasis in physiological and pathological conditions. AQP4 and AQP9, the main aquaporin subtypes in the brain, are expressed in the adult forebrain subventricular zone (SVZ), where neural stem cells (NSCs) reside, but little is known about their expression and role in the NSC population, either in vivo or in vitro. Also, no reports are available on the presence of these proteins in human NSCs. We performed a detailed molecular and phenotypical characterization of different AQPs, and particularly AQP4 and AQP9, in murine and human NSC cultures at predetermined stages of differentiation. We demonstrated that AQP4 and AQP9 are expressed in adult murine SVZ-derived NSCs (ANSCs) and that their levels of expression and cellular localization are differentially regulated upon ANSC differentiation into neurons and glia. AQP4 (but not AQP9) is expressed in human NSCs and their progeny. The presence of AQP4 and AQP9 in different subsets of ANSC-derived glial cells and in different cellular compartments suggests different roles of the two proteins in these cells, indicating that ANSC-derived astrocytes might maintain in vitro the heterogeneity that characterize the astrocyte-like cell populations in the SVZ in vivo. The development of therapeutic strategies based on modulation of AQP function relies on a better knowledge of the functional role of these channels in brain cells. We provide a reliable and standardized in vitro experimental model to perform functional studies as well as toxicological and pharmacological screenings.

Lucien J. Rubinstein: enduring contributions to neuro-oncology

Dr. Lucien Rubinstein is best remembered for his significant contributions to the field of neuropathology, particularly in the classification of nervous system tumors. His accomplishments in basic neuro-oncology and in the formulation of diagnostic principles reflected a unique talent for synthesizing fundamental clinicopathological concepts based on skillful diagnostic investigation and a thorough understanding of neurobiology. Dr. Rubinstein was the leader in the establishment of cell cultures from central nervous system (CNS) tumors. He meticulously analyzed both light and electron microscopic features of CNS tumors, recorded his findings, and patiently drew sketches to be shared generously with his colleagues and students. As a pioneer in neuropathology, in his work Dr. Rubinstein set the foundation for many enduring concepts in neurosurgery, neuro-oncology, neurology, and basic tumor biology.

Isolation and characterization of tumorigenic, stem-like neural precursors from human glioblastoma

Transformed stem cells have been isolated from some human cancers. We report that, unlike other brain cancers, the lethal glioblastoma multiforme contains neural precursors endowed with all of the critical features expected from neural stem cells. Similar, yet not identical, to their normal neural stem cell counterpart, these precursors emerge as unipotent (astroglial) in vivo and multipotent (neuronal-astroglial-oligodendroglial) in culture. More importantly, these cells can act as tumor-founding cells down to the clonal level and can establish tumors that closely resemble the main histologic, cytologic, and architectural features of the human disease, even when challenged through serial transplantation. Thus, cells possessing all of the characteristics expected from tumor neural stem cells seem to be involved in the growth and recurrence of adult human glioblastomas multiforme.

Carboplatin in childhood medulloblastoma/PNET: feasibility of an in vivo sensitivity test in an "up-front" study

Sixteen patients with high risk MB/PNET at diagnosis were included in a pilot study employing carboplatin (CBDCA) as a single drug prior to conventional therapy. The main goal of the study was to identify in a short-term trial a significant response that would predict further response to CBDCA in the single patient. Exploration of CBDCA activity was focused on response after the first course as compared to the response following the second course. A course consisted of CBDCA 600 mg/m2 on days 1 and 2 administered in a 1 h infusion to be repeated 3-4 weeks later. After two cycles we observed 1 CR and 9 PR, that is a 62% response rate. The first course resulted in 5 PR, 5 MR, 5 SD, and 1 PD; after the subsequent course in all responding patients, response persisted or improved whereas in no patient with SD any improvement was observed. The correlation of response to the first course with response to the second course was statistically significant (P = 0.0009). The main toxicity of the single course was hematologic and consisted of rapidly reversible grade 3-4 neutropenia and thrombocytopenia in 94% of patients. Pharmacokinetic studies showed a very limited interpatient variability of both Cmax 57.6 +/- 9.9 micrograms/ml) and AUC (15.3 +/- 1.5 mg/ml.min) of free CBDCA, which eliminates an important variable in the evaluation of response. In conclusion, this "in vivo test" appears effective, reasonably safe, and reproducible in identifying patients likely to benefit from CBCDA: after a period of time as short as 3-4 weeks following the first course, multidrug chemotherapy including CBDCA may be employed in the responding patients, whereas an alternative regimen would be indicated in the non-responding patients.

Glial fibrillary acidic protein and its encoding mRNA exhibit mosaic expression in a glioblastoma multiform cell line of clonal origin

The expression of two astroglial differentiation markers, vimentin and glial fibrillary acidic protein, was investigated in a previously established human glioma cell line of clonal origin (GL15). Vimentin immunolabelling was homogeneously expressed in all cells. Glial fibrillary acidic protein and its encoding message, investigated by immunocytochemistry and in situ hybridization, showed a mosaic-like expression. Only 30% of the cell population expressed glial fibrillary acidic protein and its mRNA. Western and Northern blots performed for both markers confirmed the presence of both proteins and messages, and their level was correlated with the observed antigenic and molecular probe labelling. The overall antigenic pattern suggests that GL-15 cells do not belong to the O-2A progenitor cell lineage and may arise from a clonal expansion of astrocyte precursors.

The presence of neuron-associated microtubule proteins in the human U-251 MG cell line. A comparative immunoblot and immunohistochemical study

U-251 MG, a permanent cell line derived from human glioblastoma multiforme with the capacity to maintain glial fibrillary acidic protein (GFAP) production over repeated in vitro passages, was evaluated for the expression of three neuron-associated proteins (Class III beta-tubulin, MAP2, and tau) in three different in vitro systems: as free-floating suspensions, on coverslips, and on a gelatin foam (Gelfoam) matrix. Cells grown under the three in vitro conditions were analyzed by immunoblotting techniques, whereas immunohistochemical analyses were performed on cells grown on Gelfoam. By immunohistochemistry, cells were positive for Class III beta-tubulin isotype, a neuron-associated beta-tubulin, for microtubule-associated protein 2 (MAP2), but not for tau. Immunoblotting studies confirmed the presence of Class III beta-tubulin in extracts of cells grown under the three in vitro conditions. MAP2 and tau were clearly evident only in cell extracts grown in Gelfoam cultures. GFAP expression was observed in all three in vitro conditions by immunoblotting and also in foam matrix cultures by immunohistochemistry. In matrix cultures, Class III beta-tubulin- and GFAP-positive cells were found immediately adjacent to each other, but coexpression of these proteins was not observed, and the cells were morphologically indistinguishable. Our findings confirm the heterogeneity of malignant gliomas in vitro, and the implications of these observations require further study.

Glial fibrillary acidic protein (GFAP) expression and nucleolar organizer regions (NORs) in human gliomas

The frequency of nucleolar organizer regions (NORs) in each glioma tissue and the relation between the expression of glial fibrillary acidic protein (GFAP) and the frequency of NORs was investigated. The number of Ag-NORs per cell for glioblastoma multiforme was significantly higher than that for anaplastic astrocytoma (P less than 0.05) and that for astrocytoma (P less than 0.01). The number of Ag-NORs per cell for GFAP-positive cells was significantly lower than that for GFAP-negative cells in each histopathological grade (P less than 0.01). Moreover, the linear relationship was demonstrated between the Ag-NORs numbers of GFAP-negative cells and bromodeoxyuridine (BUdR) labeling indices. From these results, it is concluded that many GFAP-positive glioma cells may have low growth potential in glioma tissue and GFAP-negative cells may have a close relation to cell proliferation. The combination of immunohistochemical and silver colloid staining is a useful method for investigating the biological characteristics of brain tumors.

Genetics of the malignant progression of astrocytoma

The tendency of human cancers to progress towards a more malignant state over time is a well described biological phenomenon. Recent investigations elucidating the genetic nature of malignancy and the possible mechanisms responsible for this evolution have suggested that a sequential pathway may exist whereby a cell population accumulates a nested set of genetic aberrations which endow it with the ability to overwhelm other populations and dominate the tumor. Human astrocytomas are a dramatic case in point, where specific genetic events of amplification and deletion are seemingly related to the stages of malignancy. The identification of these aberrations represents the first stage in the dissection of the temporal process of this cancer. Its augmentation with functional analyses will likely allow a fuller genetic description of in vivo transformation.

Parental occupation and intracranial neoplasms of childhood: anecdotal evidence from a unique occupational cancer cluster

Near the end of the data-collection phase of a case-control interview study of environmental factors and childhood brain tumors, an unusual space-time cluster was revealed. Not only had six genetically unrelated children been diagnosed with a primary intracranial tumor in a recent 2.4 year period in a rural county in Ohio, but each child had one parent employed by the same company (two mothers, four fathers). This represents an observed/expected ratio greater than 70 (p much less than 0.001). All tumors were microscopically confirmed, and all case parents worked at the facility in question for at least 1 year prior to conception, during the index pregnancy, and for at least 6 months after birth. The place of parental employment was an electronics firm (Standard Industrial Classification [SIC] group number 367, electronic components and accessories), where more than 100 chemical compounds are used by the company in a manufacturing process. Results of the cluster investigation are described, including a description of the case series. This cancer cluster is unique in that the index case series is composed of the offspring of workers, not the workers themselves.

Immunophenotype profile of childhood medulloblastomas and supratentorial primitive neuroectodermal tumors using 16 monoclonal antibodies

Immunophenotype analysis of 17 childhood medulloblastoma (MED) and supratentorial primitive neuroectodermal tumors (SPNET) was performed on frozen sections using 16 monoclonal antibodies (MoAb) with the biotin-streptavidin alkaline phosphatase immunohistochemical technique. Neuroectodermal associated antigens, reacting with MoAb UJ13/A, UJ127.11, UJ167.11, and UJ223.8 were detected on greater than 10% of the cells in 15 of 17 MED/SPNET. Thy-1 was present on 14 of 17 tumors and absent on two of three SPNET. Neuronal (NF) and glial (GFAP) differentiation markers were evaluated. NF-H was demonstrated in 15 of 17, NF-M in six of 17 and NF-L in one of 17 tumors; GFAP was positive in nine of 17 patients. In nine of 17 MED/SPNET both proteins were present within the same tumor. Common leukocyte antigen was demonstrated on greater than 50% of the cells in four of 14 tumors as were shared tumor/leukocyte markers using monoclonal antibodies Thy-1, PI153/3, UJ308. The most frequent MED immunophenotype analysis was UJ 13/A+, UJ 127.11+, UJ 167.11+, UJ223.8+, PI 153/3+, A2B5+, GFAP+, NF-H+, and CLA-, NF-M-, NF-L-, 215-, 275-, 282.1-. The authors conclude that MED and SPNET are heterogeneous for expression of 16 markers and have similar immunophenotype analysis profiles, supporting the concept of their common, neuroectodermal origin. Common leukocyte antigen on both tumor cells and leukocytes precludes identification of tumor infiltrating leukocytes using monostaining techniques.

Immortalization of hypothalamic GnRH neurons by genetically targeted tumorigenesis

By genetically targeting tumorigenesis to specific hypothalamic neurons in transgenic mice using the promoter region of the gonadotropin-releasing hormone (GnRH) gene to express the SV40 T-antigen oncogene, we have produced neuronal tumors and developed clonal, differentiated, neurosecretory cell lines. These cells extend neurites, express the endogenous mouse GnRH mRNA, release GnRH in response to depolarization, have regulatable fast Na+ channels found in neurons, and express neuronal, but not glial, cell markers. These immortalized cells will provide an invaluable model system for study of hypothalamic neurosecretory neurons that regulate reproduction. Significantly, their derivation demonstrates the feasibility of immortalizing differentiated neurons by targeting tumorigenesis in transgenic mice to specific neurons of the CNS.

Congenital cerebral primitive neuroectodermal tumor with astrocytic differentiation and extracranial metastases

A cerebral primitive neuroectodermal tumor with astrocytic differentiation and extracranial metastases in a 28-day-old infant is reported. The infant presented with a progressively enlarged head, cutaneous lesions in the neck, and enlarged cervical lymph nodes. A computed tomography brain scan demonstrated a giant thalamic tumor with subarachnoid dissemination and hydrocephalus. Biopsy material from the cervical lesions showed a picture of glioma with anaplastic astrocytes. The patient received a ventriculoperitoneal shunt operation and palliative chemotherapy, but died at 3 months of age. Autopsy was performed. Histological studies, which included immunohistochemical stains of the thalamic tumor, showed small, round, primitive, neoplastic cells with focal astrocytic differentiation.

Growth factors derived from a human malignant glioma cell line, U-251MG

A human malignant glioma cell line, U-251 Mg, cultured under serum free conditions, was shown to produce a growth factor for BALB/c 3T3 cells (glioma-derived growth factor-1, GDGF-1). The biological activity of GDGF-1 resided in a heat- and acid-resistant protein with a molecular weight (MW) of 25 kDa estimated by gel permeation chromatography. GDGF-1 activity was neutralized by a goat anti-human platelet derived growth factor (PDGF) antibody, indicating that the two factors were immunologically related. Furthermore, U-251 Mg cells constitutively expressed c-sis mRNA. When U-251 Mg cells were stimulated with bacterial lipopolysaccharide, 2 novel growth factors (GDGF-2 and GDGF-3) were produced in addition to the PDGF-like substance. GDGF-2 was determined to be greater than 100 kDa MW and was not neutralized by the goat anti-PDGF antiserum. The biological activity of GDGF-3 was also heat- and acid-resistant with an apparent 14 kDa MW. This factor also did not show any common antigenicity with PDGF. GDGF-2 and GDGF-3 are currently under investigation and evidence as to their natures will be published elsewhere. Our findings with this glioma cell line provide further evidence that inappropriate expression of growth factor-related genes could play important autocrine role(s) in the processes leading to malignant transformation and/or uncontrolled proliferation and may provide a paracrine stimulus for such processes as glioma neovascularization.

Cytologic composition of the untreated glioblastoma with implications for evaluation of needle biopsies

To study the progression of astrocytic neoplasms and to provide practical information about the topography of the glioblastoma multiforme, the distribution of eight defined cell types was mapped from whole brain sections of 18 glioblastomas studied postmortem. Based on the densities and topographic distributions of well-differentiated and anaplastic cells, three principal categories of neoplasms were defined. In one group of three cases, multifocal glioblastomas appeared to be emerging in the background of a better differentiated, and presumably precursory, astrocytic neoplasm. In another group of nine cases, the neoplasms were more intimate mixtures of well and poorly differentiated cells. The third group of five cases was composed of neoplasms that were largely undifferentiated without a component of better differentiated cells. The study suggests that progression from a better differentiated neoplasm to one composed largely of undifferentiated cells is common in the fibrillary astrocytic neoplasms. Although some glioblastomas appear largely undifferentiated and consistent with the de novo appearance of overt malignancy, the size of these neoplasms and the patterns of necrosis leave open the possibility that a preexisting better differentiated neoplasm had been obliterated by necrosis and the overgrowth of the anaplastic component. The potential topographic variation of cellular constituency in a glioblastoma underscores the care that must be exercised in utilization of the needle biopsy technique in the diagnosis and grading of astrocytic neoplasms.

Prognostic value of histologic factors in adult cerebral astrocytoma

Surgical specimens from 165 adults with cerebral astrocytoma were reviewed to establish the prognostic value of histologic factors when studied both individually and in combination. Glioblastomas were excluded. Nine morphologic parameters and 25 clinicotherapeutic factors were correlated with survival. Cell density, endothelial hyperplasia, number of mitoses X 10 high-power field (HPF), and vessel frequency appeared to be highly significant prognostic factors (P less than 0.001). Nuclear polymorphism, microcysts, and vessel size were significant moderately (P less than 0.01). Microcysts, vessel size, endothelial hyperplasia, and number of mitoses X 10 HPF remained significant statistically after a multivariate analysis that also included clinicotherapeutic factors. Survival was similar for astrocytomas with "extensive malignancy" and astrocytomas with only "slight and localized malignancy." Multivariate analysis showed that the presence or absence of malignancy was more important prognostically than the clinical variables (i.e., postoperative Karnofsky status or extent of surgical removal).

The biology of astrocytoma: lessons learned from chronic myelogenous leukemia--hypothesis

Chronic myelogenous leukemia (CML) is an example of a "well-differentiated" neoplasm that develops following neoplastic transformation of a precursor cell. The biology of astrocytic neoplasms can be interpreted in light of concepts that have emerged from studies of the myeloproliferative disorders. Astrocytomas may arise from a pluripotential precursor cell whose progeny, although transformed, retain the ability to differentiate, and do so along astrocytic lines. The result is a neoplasm composed of "mature" tumor cells, similar one to another, and resembling normal astrocytes. Malignant change, like blast crisis in CML, then occurs as a consequence of further molecular genetic events leading to accelerated growth and maturation arrest in a previously differentiating neoplastic cell. This hypothesis challenges the conventional view that astrocytomas arise from astrocytes and that malignant change occurs as a result of dedifferentiation. Extensions of this hypothesis may be relevant to the biology of other glial tumors.

Embryonal central neuroepithelial tumors: current concepts and future challenges

While the embryonal central neuroepithelial tumors present complex conceptual and clinical problems, advances in cell type identification by special neurohistological, immunohisto- and immunocytochemical techniques have permitted discrimination of distinct cytomorphogenetic entities. These are based in part on their resemblance to the normal phases of neurocytogenesis. Four of these tumors, medulloepithelioma, desmoplastic infantile ganglioglioma, pineoblastoma and medulloblastoma, are designated as multipotential in light of their capacity to undergo divergent differentiation. Cytomorphogenetic, clinical and experimental data implicate fetal neural cell targets for transformation and raise the possibility that aberrant developmental regulatory mechanisms may contribute to the biologic behavior of these tumors. Growth factors and some neuroregulatory neurotransmitters (such as serotonin) are known to act as modulators of normal neuromorphogenesis. They could play a regulatory role in central neuroepithelial tumors on the hypothesis that the aberrant behavior of the embryonal neoplasms could either be modified by functional receptor responses or result from abnormal receptor responses to these substances. Future challenges include the definition of new cytomorphogenetic entities and subgroups of the currently defined forms of embryonal CNS tumors based on the presence of specific growth factors and neuroregulatory neurotransmitters, or their receptors, the characterization of neoplastic receptor responses mediating any modulatory role of the presently known growth factors or neuroregulatory neurotransmitters on the growth and maturation potential of the embryonal central neuroepithelial tumors and the further definition of developmental, stage-specific modulators that might be operative in these tumors.

Immunohistochemical demonstration of vimentin in human cerebral tumors

The distribution of vimentin (VIM) has been histochemically investigated in 53 cerebral tumors and compared in gliomas to that of glial fibrillary acidic protein (GFAP). In gliomas VIM is less positive than GFAP, but shows the same distribution. It cannot be considered as indicating immaturity of glial tumor cells. VIM is also positive in glial processes of cerebellar pilocytic astrocytomas, in Schwann cells of neurinomas and in endothelial cells of all oncotypes. In medulloblastomas, VIM decorates reactive glia cells. A diffuse positive reaction has been observed in meningiomas. In hemangioblastomas, besides intervascular and endothelial cells, groups of polygonal cells are intensely positive for both VIM and GFAP. The interpretation of VIM in cerebral tumors is largely based on the distribution patterns of this intermediate filament in the developing CNS of rodents.