Dibutyryl cyclic AMP induces vimentin and GFAP expression in cultured medulloblastoma cells

Crown of Microfilaments in the Extending Cytoplasmic Processes of Medulloblastoma Glial Progenitors

Microfilaments and microtubules play a part in the extension of neuronal processes but their roles in the formation of glial processes have not yet been determined. The objectives of this study were to determine the organization of microfilaments in differentiating glial progenitors (RB2 cells) and to study the effects of microfilament or microtubule disruption on process extension. Intense F-actin staining (crown of microfilaments) was observed at the leading edge of a small extending conical tip in differentiating RB2 cells, but was absent in process-bearing TE671 rhabdomyosarcoma cells. No significant difference was noted in the mean number of TE671 cells with processes treated with a microfilament disrupter from that of similarly treated controls. In contrast, a significant difference was noted in the mean number of RB2 cells with processes after microfilament disruption treatment from that of similarly treated controls. Microtubule disruption arrested extension and caused process retraction in both cell types. The results of this study demonstrate that microtubules play an equally important part in the extension and stabilization of the RB2 and TE671 processes. Moreover, the crown of microfilaments concentrated in the glial RB2 process (and not in the TE671 process) may be critical to its extension during differentiation.

A paediatric supratentorial primitive neuroectodermal tumour associated with malignant astrocytic transformation and a clonal origin of both components

The case of a 7-year-old boy suffering from a supratentorial primitive neuroectodermal tumour (sPNET) at the age of 5 is presented. The tumour has been characterized by astrocytic areas within the sPNET revealing malignant transformation up to a multiform glioblastoma during the course of the disease. The clonal origin of both tumour components was established by loss of heterozygosity (LOH) analysis. Clinically, the tumour showed an aggressive biological behaviour with two recurrences. We discuss this very rare case and the first description of the clonal origin of distinct and distinguishable tumour components taking into consideration published literature.

The neurobiology of neurooncology

The histological classification of brain tumors currently is based on the morphological appearance and protein expression patterns that reflect specific cell types within the central nervous system. Recent studies have suggested that the cells of origin for brain tumors may persist in the fully formed tumors, and that these "cancer stem cells" might represent the relevant cellular targets for anticancer therapy. In this regard, insights into the developmental neurobiology of brain tumors has significant impact on our understanding of the molecular and cellular pathogenesis of these devastating cancers, as well as the development of new strategies for treating brain tumors.

Local interstitial chemotherapy with sustained release bucladesine in de novo glioblastoma multiforme: a preliminary study

This clinical study was designed to evaluate the safety and efficacy of the sustained release form of dibutryl adenosine-3',5'-cyclic monophosphate (dB-cAMP, bucladesine) placed in the tumor resection cavity at the time of recurrence of the de novo glioblastoma multiforme (GBM) patients. In a randomized prospective manner, 40 patients who were diagnosed as GBM in their first operations were included in this study. Four different therapy protocols were used: First group of 10 patients had tumor resection only. Second group assessed had only systemic chemotherapy as six i.v. infusions of fotémustine after tumor resection. Third group had implantation of bucladesine-loaded biodegradable polymeric sustained release (bcl-SR) pellets while the last group received six i.v. infusions of systemic fotémustine as in the second group in addition to local implantation of bcl-SR pellets. A biodegradable polymer, poly-DL-lactide-co-glycolide with molecular weight of 80000, was used as carrier matrix for the drug with an approximately 4-5 months of release time. Maximal doses of 20 mg of bucladesine with a mean dose of 15.5 mg were implanted. No bone marrow suppression occurred and there were no wound infections as far as the local bucladesine-loaded polymer therapy is concerned. In this randomized prospective trial of local interstitial chemotherapy with long acting bcl-SR did show a statistically significant delay of recurrence on the treatment of GBM patients. Best treatment results obtained from the local bcl-SR + systemic fotémustine treated group in which survival rate estimated by the Kaplan-Meier method was 70% in de novo GBM at 12 months.

In vitro properties of a newly established medulloblastoma cell line, MCD-1

Medulloblastomas are poorly differentiated brain tumors believed to arise from primitive pleuripotential stem cells, and tend to express mixed neuronal and glial properties. In the present study, we examined immunohistochemical and neurotransmitter phenotypic properties in a newly established medulloblastoma cell line, MCD-1. MCD-1 cells were immortal, not contact-inhibited, but did not grow in soft agar. Immunohistochemical studies showed positive staining for neurofilament protein (NF), neuron-specific enolase (NSE), synaptophysin, MAP 2, tau, NCAM 180, vimentin, and S-100 protein. The cells expressed specific uptake of glutamate, serotonin, and choline, but not GABA or dopamine. A significant increase in process extension was seen in response to agents that enhance intracellular cyclic AMP, especially 3-isobutyl-1-methylxanthine (IBMX). Process formation induced by IBMX was associated with a decrease in cell proliferation as evidenced by a reduction in numbers of cells incorporating 5-bromo-2-deoxyuridine (BrdU). No increase in process extension was observed following exposure to NGF or retinoic acid. MCD-1 cells were shown to produce transforming growth factor beta (TGF beta), and were immunopositive for mutant p53. Transfection assays with the PG13-Luc reporter plasmid, which contains a p53-responsive enhancer element and a luciferase reporter gene, suggested MCD-1 cells are deficient in wild-type p53 and do not activate p53 on treatment with the anticancer agent adriamycin. The MCD-1 cell line is suggested to represent an abnormally differentiated cell type, which has some properties consistent with a multipotent neuronal phenotype while retaining some properties of immature cells of a glial lineage. The MCD-1 cell line can be used to provide a model of a medulloblastoma cell line that is resistant to growth-controlling and anticancer agents.

Cholera toxin beta subunit induces the differentiation of human medulloblastoma cell line DEV in a neuronal pathway

Medulloblastomas are primitive neuroectodermal tumours that are thought to arise from multipotent precursor cells in the cerebellum. Medulloblastoma cells may be undifferentiated or exhibit glial, neuronal or ependymal characteristics, suggesting that they may conserve their ability to differentiate in appropriate circumstances. Medulloblastoma cell lines may thus provide models to study the commitment and differentiation of multipotent CNS progenitor cells. A human medulloblastoma cell line, DEV, has previously been shown to differentiate in an astrocytic pathway after infection by the retrovirus HTLV-1. In this study immunofluorescence flow cytometry shows that cholera toxin beta subunit (CT beta), which binds to the ganglioside GM1, induces a twofold increase in the number of DEV cells differentiating towards a neuronal pathway, as shown by the increased proportion and labelling intensity of cells stained by an anti-neurofilament antibody. Immunocytochemistry shows that after 3 days in culture with CT beta, DEV cells develop processes which stain positive for neurofilaments and MAP-1. This suggests that CT beta induces DEV cells to express a more neuronal phenotype.

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.

Differentiation of a medulloblastoma cell line towards an astrocytic lineage using the human T lymphotropic retrovirus-1

Constituent cells of medulloblastoma, the most common brain tumor occurring in childhood, resemble the primitive neuroepithelial cells normally found in the developing nervous system. However, mutational events prevent their further differentiation. We used the human T cell lymphotrophic virus type 1 to activate these deregulated immature cells by means of its transactivating protein Tax. Concomitant with viral infection was a decrease in cell proliferation characterized by inhibition of [3H]thymidine incorporation and in the number of cells in the G2/M phase of the cell cycle. Morphological changes suggested that medulloblastoma cells differentiated along the astrocytic lineage. The glial phenotype was confirmed by the induction of the glial fibrillary acidic protein and the glial enzyme glutamine synthetase. A direct viral effect and/or secondary effects to viral infection via paracrine/autocrine pathways could counterbalance the maturational defect in these medulloblastoma cells.