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Biomedical subjects

M Weller

Publications and source records attributed to M Weller.

At least 91 records · Page 5Linked to original sources
PubMed2000

CD95-mediated apoptosis in vivo involves acid sphingomyelinase.

Acid sphingomyelinase (ASM) is reported to have an essential function in stress-induced apoptosis although the physiological function of ASM in receptor-triggered apoptosis is unknown. Here, we delineate a pivotal role for ASM in CD95-triggered apoptosis of peripheral lymphocytes or hepatocytes in vivo. We employed intravenous injection of anti-CD4 antibodies or phytohemagglutinin that was previously shown to result in apoptosis of peripheral blood lymphocytes or hepatocytes via the endogenous CD95/CD95 ligand system. Our results demonstrate a high susceptibility in normal mice whereas ASM knock-out mice fail to immunodeplete T cells or develop autoimmune-like hepatitis. Likewise, ASM-deficient mice or hepatocytes and splenocytes ex vivo manifest resistance to anti-CD95 treatment. These results provide in vivo evidence for an important physiological function of ASM in CD95-induced apoptosis.

Animals↗
PubMed2000

Secreted Frizzled-related proteins inhibit motility and promote growth of human malignant glioma cells.

Cellular resistance to multiple proapoptotic stimuli and invasion of surrounding brain tissue by migrating tumor cells are main obstacles to an effective therapy for human malignant glioma. Here, we report that the Wnt family of embryonic differentiation genes modulate growth of malignant glioma cells in vitro and in vivo and inhibit cellular migration in vitro. sFRPs (soluble Frizzled-related proteins) are soluble proteins that bind to Wnt and interfere with Wnt signaling. We find that sFRP-1 and sFRP-2 are produced by the majority of longterm and ex vivo malignant glioma cell lines. Glioma cells that ectopically express sFRPs exhibit increased clonogenicity and enhanced resistance to serum starvation. In contrast, sFRPs do not modulate glioma cell susceptibility to apoptosis induced by the cytotoxic cytokines, CD95 (Fas/APO-1) ligand (CD95L) or Apo2 ligand/tumor necrosis factor-related apoptosis-inducing ligand (Apo2L/TRAIL), or various cytotoxic drugs. sFRP-2 strongly promotes the growth of intracranial glioma xenografts in nude mice. In contrast, enhanced expression of sFRPs inhibits the motility of glioma cells in vitro. sFRP-mediated effects on glioma cells are accompanied by decreased expression and activity of matrix metalloproteinase-2 (MMP-2) and decreased tyrosine phosphorylation of beta-catenin. Thus, sFRPs promote survival under non-supportive conditions and inhibit the migration of glioma cells. We suggest that the regulation of these cellular processes involves expression of MMP-2 and tyrosine phosphorylation of beta-catenin. These data support a function for Wnt signaling and its modulation by sFRPs in the biology of human gliomas. Oncogene (2000) 19, 4210 - 4220

Animals↗
PubMed2000

Poly(ADP-ribose) polymerase-independent potentiation of nitrosourea cytotoxicity by 3-aminobenzamide in human malignant glioma cells.

Poly(ADP-ribose) polymerase is a zinc-finger DNA-binding protein that detects specifically DNA strand breaks generated by genotoxic agents and is thought to be involved in DNA repair. Here, we examined the effects of 3-aminobenzamide, a poly(ADP-ribose) polymerase inhibitor, on the chemosensitivity of human malignant glioma cells. 3-Aminobenzamide selectively potentiated the cytotoxicity of the nitrosoureas, nimustine, carmustine and lomustine in 10 of 12 human malignant glioma cell lines. In contrast, 3-aminobenzamide did not modulate the cytotoxic effects of doxorubicine, teniposide, vincristine, camptothecin or cytarabine. The nitrosoureas did not induce poly(ADP-ribose) polymerase activity in the glioma cells. Ectopic expression of truncated poly(ADP-ribose) polymerase containing the poly(ADP-ribose) polymerase DNA-binding domain, which acts as a dominant-negative mutant, in LN-18 or LN-229 cells did not alter the 3-aminobenzamide effect on nitrosourea-mediated cytotoxicity. Thus, 3-aminobenzamide may target another nicotinamide adenine dinucleotide (NAD)-requiring enzyme, but not poly(ADP-ribose) polymerase, when enhancing nitrosourea cytotoxicity in human malignant glioma cells. Carmustine cytotoxicity was associated with a G2/M arrest. Coexposure to carmustine and 3-aminobenzamide overcame this G2/M arrest in T98G cells, which are sensitized to carmustine by 3-aminobenzamide, but not in U251MG cells, which are refractory to 3-aminobenzamide-mediated sensitization to carmustine. Thus, 3-aminobenzamide-mediated sensitization to carmustine cytotoxicity may result from interference with the stable G2/M arrest response to carmustine in human glioma cells.

Benzamides↗
PubMed2000

Sensitization to CD95 ligand-induced apoptosis in human glioma cells by hyperthermia involves enhanced cytochrome c release.

CD95L-induced apoptosis involves caspase activation and is facilitated when RNA and protein synthesis are inhibited. Here, we report that hyperthermia sensitizes malignant glioma cells to CD95L- and APO2L-induced apoptosis in the absence, but not in the presence, of inhibitors of RNA and protein synthesis. Hyperthermia does not alter CD95 expression at the cell surface and does not modulate the morphology of CD95-mediated cell death on electron microscopy. Bcl-2 gene transfer inhibits apoptosis and abrogates the sensitization mediated by hyperthermia. Hyperthermia does not overcome resistance to apoptosis conferred by the viral caspase inhibitor, crm-A, indicating the absolute requirement for the activation of crm-A-sensitive caspases, probably caspase 8, for apoptosis. CD95L-evoked DEVD-amc-cleaving caspase activity is enhanced by hyperthermia, suggesting that hyperthermia operates upstream of caspase processing to promote apoptosis. There is no uniformly enhanced processing of three caspase 3 substrates, poly-ADP ribose polymerase (PARP), protein kinase C (PKC) delta and DNA fragmentation factor (DFF) 45. Yet, hyperthermia promotes CD95L-evoked DNA fragmentation. Interestingly, hyperthermia enhances the CD95L-evoked release of cytochrome c in the absence, but not in the presence, of CHX. In contrast, the reduction of the mitochondrial membrane potential is enhanced by hyperthermia both in the absence and presence of CHX, and enhanced cytochrome c release is not associated with significantly enhanced caspase 9 processing. The potentiation of cytochrome c release at hyperthermic conditions in the absence of CHX is abrogated by Bcl-2. Thus, either hyperthermia or inhibition of protein synthesis by CHX potentiate cytotoxic cytokine-induced apoptosis. These pathways show no synergy, but rather redundance, indicating that CHX may function to promote apoptosis in response to cytotoxic cytokines by inhibiting the synthesis of specific proteins whose synthesis, function or degradation is temperature-sensitive.

Apoptosis↗
PubMed2000

Expression patterns of hairy, even-skipped, and runt in the spider Cupiennius salei imply that these genes were segmentation genes in a basal arthropod.

There is an ongoing discussion on whether segmentation in different phyla has a common origin sharing a common genetic program. However, before comparing segmentation between phyla, it is necessary to identify the ancestral condition within each phylum. Even within the arthropods it is not clear which parts of the genetic network leading to segmentation are conserved in all groups. In this paper, we analyze the expression of three segmentation genes of the pair-rule class in the spider Cupiennius salei. Spiders are representatives of the Chelicerata, a monophyletic basic arthropod group. We find that in spider embryos, the orthologues for the Drosophila primary pair-rule genes hairy, even-skipped, and runt are expressed in stripes in the growth zone, where the segments are forming, suggesting a role for these genes in chelicerate segmentation. These data imply that the involvement of hairy, even-skipped, and runt in arthropod segmentation is an ancestral character for arthropods and is not restricted to a particular group of insects.

Animals↗
PubMed2000

Expression and functional activity of heat shock proteins in human glioblastoma multiforme.

OBJECTIVE: To assess the expression of heat shock proteins (HSP) in glioma cells in vitro and in vivo and to examine their role in resistance to apoptosis. BACKGROUND: HSP are expressed in response to various forms of stress. Constitutive HSP expression may confer resistance to cytotoxic stimuli in human cancers. METHODS: HSP expression was assessed by immunoblot analysis in glioma cells in vitro and by immunocytochemistry in human glioblastomas in vivo. Modulation of apoptosis by hyperthermia-mediated HSP induction was examined in glioma cell lines in vitro. RESULTS: Immunoblot analysis revealed constitutive expression of HSP27, HSP72, HSP73, and HSP90 in all 12 human glioma cell lines. B-crystallin (alphaBC) was expressed in 3 of 12 cell lines. High levels of alphaBC and HSP72 correlated with drug resistance and high p53 levels in vitro. Transient hyperthermia (43 degrees C/2 hours) induced HSP27 and HSP72 expression but had no effect on the levels of alphaBC, HSP73, or HSP90. HSP induction provided no survival advantage against subsequent cytotoxic challenges, including cytotoxic cytokines and radiochemotherapy. Immunohistochemistry showed strong expression of all HSP in vivo. The comparative analysis of HSP27, alphaBC, HSP72, HSP73, and HSP90 expression in 24 paired samples of first resections and recurrences of human glioblastoma multiforme revealed no impact of HSP expression on response to adjuvant radiochemotherapy and no modulation of HSP expression by radiochemotherapy. CONCLUSIONS: High constitutive, as opposed to inducible, expression of HSP may play a role in the primary resistance of human malignant gliomas to cytotoxic radiochemotherapy. Superinduction of HSP levels by hyperthermia in vitro provided no further survival advantage.

Adult↗
PubMed2000

Insulin-like growth factor-1-mediated protection from neuronal apoptosis is linked to phosphorylation of the pro-apoptotic protein BAD but not to inhibition of cytochrome c translocation in rat cerebellar neurons.

Cerebellar granule neurons cultured in the presence of serum and depolarizing potassium concentrations undergo apoptosis when switched to serum-free medium containing physiological potassium concentrations but remain viable after serum deprivation alone. Here, we show that potassium deprivation is associated with the dephosphorylation of the BCL-2-related BAD protein. Exposure to insulin-like growth factor-1 (IGF-1) inhibits both apoptosis and dephosphorylation of BAD. Both effects of IGF-1 do not depend on protein synthesis but are nullified by the phosphatidylinositol-3 kinase inhibitors, wortmannin and LY294002. In contrast to the treatment with cycloheximde, IGF-1 does not block the translocation of cytochrome c from mitochondria to the cytosol. Further, dephosphorylation of BAD alone does not appear to be sufficient to trigger apoptosis, since inhibition of protein synthesis by cycloheximide prevents apoptosis, but not BAD dephosphorylation, after potassium deprivation. These results suggest the coexistence of two parallel pathways, protein synthesis-dependent cytochrome c translocation and protein synthesis-independent dephosphorylation of BAD, both of which have to be activated to induce neuronal apoptosis.

Androstadienes↗
PubMed2000

Transforming growth factors beta(1) (TGF-beta(1)) and TGF-beta(2) promote glioma cell migration via Up-regulation of alpha(V)beta(3) integrin expression.

The migratory behaviour of malignant gliomas relies on the interaction of integrins with extracellular matrix (ECM) components. Transforming growth factor-beta(1) (TGF-beta(1)) potently stimulates glioma cell motility whereas TGF-beta(2) is known for its immunosuppressive properties. Here, we show that both TGF-beta(1) and TGF-beta(2) promote migration of glioma cells. In parallel, TGF-beta(1) and TGF-beta(2) induce alpha(V) and beta(3) intergrin mRNA expression and enhance cell surface expression of alpha(V)beta(3) integrin. TGF-beta-mediated promotion of migration is abrogated by echistatin, a Arg-Gly-Asp (RGD) peptide antagonist of alpha(V)beta(3) integrin, and by a neutralizing anti-alpha(V)beta(3) integrin antibody. Taken together, we report a novel mechanism by which TGF-beta modulates cell ECM interactions and promotes glioma cell motility.

Cell Movement↗
PubMed2000

No induction of apoptosis by IFN-beta in human antigen-specific T cells.

Interferon (IFN)-beta, the most effective immunomodulatory treatment for MS, inhibits the proliferation of myelin-specific T cells. We report that IFN-beta moderately enhances the expression of the death receptor, CD95, at the surface of human antigen-specific T cells. However, T-cell apoptosis was not induced by IFNbeta-1a or IFNbeta-1b as assessed by caspase activity or DNA fragmentation. Immunomodulation mediated by IFN-beta does not directly involve apoptotic pathways in human T cells.

Adjuvants, Immunologic↗
PubMed2000

Altered expression of calcium- and apoptosis-regulating proteins in multiple system atrophy Purkinje cells.

The expression patterns of the calcium binding proteins calbindin and parvalbumin and of the apoptosis modulating proteins Bcl-2, Bax, and Bcl-x were studied in the cerebellum of patients with multiple system atrophy (MSA). Calbindin and parvalbumin immunoreactivity was markedly decreased in MSA Purkinje cells whereas Bax and Bcl-x protein expression was increased. Bcl-2 expression was restricted to a subpopulation of granule neurons, but no decrease of Bcl-2 was evident in MSA. Additional DNA end-labeling (ISEL) studies revealed only one possible apoptotic Purkinje cell nucleus, but nuclei in the cerebellar white matter, probably oligodendrocytes, in the cerebellum of patients with MSA. The present results suggest that a diminished calcium binding capacity of MSA Purkinje cells might lead to a change in the regulation of proteins of the bcl-2 family that could favor the pathologic initiation of apoptosis.

Apoptosis↗
PubMed2000

APO2L/TRAIL expression in human brain tumors.

APO2 ligand (APO2L)/TRAIL is a novel member of the tumor necrosis factor cytokine family and a potent inducer of apoptosis in tumor cell lines. We recently reported that APO2L is consistently expressed in low-grade astrocytomas, anaplastic astrocytomas, glioblastomas, and cell lines derived thereof, and that malignant glioma cell lines are susceptible to APO2L-induced apoptosis. In this study, we investigated whether APO2L is expressed in medulloblastoma or neuroblastoma cell lines and whether these cells are sensitive to APO2L-induced apoptosis. Immunoblot analyses revealed full-length APO2L protein expression in one (DAOY) of three medulloblastoma cell lines but not in two neuroblastoma cell lines (SKN-BE and SKN-LE). Viability assay performed after exposure to soluble APO2L for 16 h showed that DAOY medulloblastoma cells were the most sensitive and that apoptosis induced by APO2L was greatly enhanced when protein synthesis was inhibited by cycloheximide. Neuroblastoma cell lines were almost completely resistant to APO2L-induced apoptosis. We also carried out APO2L immunohistochemistry in a total of 115 tumors of the nervous system with different histogenesis and biological behavior. In all 9 pilocytic astrocytomas, the areas of dense fibrillary network showed diffuse and strong APO2L expression. In oligodendrogliomas, APO2L expression was observed in areas with a significant admixture of astrocytic cells, but was absent in neoplastic oligodendrocytes. In 13 of 14 ependymomas, APO2L was expressed in perivascular pseudorosettes. In all 12 medulloblastomas, strong APO2L expression was observed in intra-tumoral-reactive astrocytes, but neoplastic cells did not show APO2L immunoreactivity. Thus, the pattern of APO2L expression was largely similar to that of glial fibrillary acidic protein (GFAP), except for choroid plexus tumors and 3 of 8 anaplastic meningiomas, in which APO2L was focally expressed without concomitant GFAP expression. APO2L expression was absent in meningiomas, neurocytomas, and schwannomas. Thus, there is considerable heterogeneity of APO2L expression and susceptibility to APO2L-induced apoptosis among human brain tumors.

Apoptosis↗
PubMed2000

Dapsone and colchicine inhibit adhesion of neutrophilic granulocytes to epidermal sections.

A frozen section adhesion assay was used to study the influence of dapsone and colchicine on cell-cell adhesion between neutrophils and epidermal cells. Sections were prepared from small punch biopsies from healthy donors after preincubation with IFN-A. Freshly prepared neutrophils were activated with TNF-. or PAF after exposure to dapsone or colchicine, incubated on these sections, and the adhered cells were enumerated after washing. In the presence of dapsone (at concentrations of 0.1-80 Ig/ml) adherence of neutrophils could be blocked dose-dependently and 50% inhibition of adhesion was achieved at a concentration of 10 Ig/ml. Colchicine at concentrations of 10-200 ng/ml inhibited neutrophil binding with a clear correlation between inhibition and colchicine concentration. At a colchicine concentration of 110 ng/ml, 50% blocking was achieved. Since the function of CD11b/ paragraph signCD18 is necessary for neutrophil adhesion in this assay, we monitored CD11b expression on neutrophils after dapsone and colchicine exposure. CD11b expression on neutrophils was significantly reduced 5 h after incubation with dapsone at a concentration of 80 Ig/ paragraph signml, whereas no effects of colchicine on CD11b expression could be demonstrated. Our study showed that both drugs significantly inhibited adhesion between neutrophils and the epidermis.

Cell Adhesion↗
PubMed2000

Evidence for a constitutive, verapamil-sensitive, non-P-glycoprotein multidrug resistance phenotype in malignant glioma that is unaltered by radiochemotherapy in vivo.

Human malignant gliomas are commonly resistant to chemotherapy. Here, we examined the role of the multidrug resistance (mdr) mechanism in the chemo-resistance of these tumors, using a twofold approach: (i) by assessing a possible mdr phenotype before and after chronic drug exposure of glioma cells in vitro, and (ii) by assessing the modulation of expression of the mdr-associated P-glycoprotein (Pgp) using radiotherapy and serial cycles of chemotherapy in human glioblastoma patients in vivo. T98G, and to a lesser degree, LN-229 human malignant glioma cells exhibit a constitutive mdr phenotype as determined by the modulation of dye transport and by the augmentation of chemosensitivity by the mdr antagonist, verapamil. Thus, coexposure to verapamil enhances the cytotoxicity of vincristine, doxorubicin and VM26 in T98G cells and that of vincristine in LN-229 cells. Chronic exposure of the cells to low concentrations of vincristine and doxorubicin, but not VM26, topotecan or BCNU, moderately enhances the mdr-like phenotype, as assessed by drug expulsion assays. However, chronic exposure to increasing drug concentrations does not significantly alter the sensitivity to the respective drugs. These data are consistent with a constitutive, but not drug-inducible, mdr-like drug resistance in glioma cells in vitro. Immunocytochemical analysis of human malignant gliomas in vivo reveals that Pgp expression is more abundant in endothelial cells within the gliomas, than in the glioma cells proper. Importantly, Pgp expression is unaltered by radiochemotherapy, assessed by comparative immunocytochemistry of glioma specimens obtained serially before and after radiochemotherapy. We conclude that (i) glioma cells exhibit constitutive mdr-like drug resistance that is not significantly altered by chronic drug exposure in vitro; (ii) endothelial cells may play an important role in Pgp-mediated drug resistance of gliomas in vivo; (iii) radiotherapy and repeated chemotherapy cycles do not modulate Pgp expression in human malignant gliomas in vivo; (iv) there is preliminary evidence for a non-Pgp, verapamil-sensitive drug transport activity in glioma cells.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2000

Central nervous system Hodgkin's lymphoma without systemic manifestation: case report and review of the literature.

A 66-year-old woman treated for ocular myasthenia gravis with azathioprine for 12 years presented with a left fronto-parietal mass. Histology revealed primary Hodgkin's lymphoma of the central nervous system with CD30, Epstein-Barr virus (EBV) latent membrane protein and CD20-positive, CD45 (LCA)-negative Reed-Sternberg cells surrounded by T cells. Moreover, EBV-encoded RNA-1 (EBER-1) sequences and a monoclonal rearrangement of the immunoglobulin heavy chain CDR2 locus were detected.

Aged↗
PubMed2000

A role for preirradiation PCV chemotherapy for oligodendroglial brain tumors.

Oligodendroglial tumors have been identified as a subgroup of glial neoplasms with a distinctly better response to chemotherapy and overall survival than purely astrocytic gliomas. Here we report our experience with adjuvant postirradiation and preirradiation chemotherapy using procarbazine, lomustine, and vincristine (PCV) in 27 patients with WHO grade II or III oligodendroglioma or oligoastrocytoma. The efficacy of chemotherapy was assessed according to the Macdonald response criteria (complete response, CR; partial response, PR; stable disease, SD; progressive disease, PD) and progression-free survival intervals by computed tomography or magnetic resonance imaging. First, we confirm that PCV salvage therapy for patients progressing after radiotherapy is highly effective (n = 11, 1 CR, 5 PR, 5 SD; median progression-free survival has not yet been reached, but is longer than 18 months). Second, 3 patients who received radiotherapy plus PCV as first-line therapy achieved CR and 2 achieved SD, and all 5 are progression-free with a median follow-up of 12 months. Third, given these encouraging results, 11 patients received postoperative preirradiation PCV chemotherapy and were given radiotherapy only upon progression. Preirradiation PCV chemotherapy was also effective (2 CR, 3 PR, 6 SD; median progression-free survival has not been yet reached, but is longer than 14 months). Patients with anaplastic oligoastrocytomas were as likely to respond to PCV chemotherapy, as were patients with anaplastic oligodendroglioma. Three patients who had previously responded to PCV were successfully treated with a second course of PCV upon recurrence. PCV chemotherapy was also effective in patients with leptomeningeal spread of oligodendrogliomas. A randomized prospective trial is required to compare the effectiveness and neurotoxicity of first-line PCV chemotherapy followed by radiotherapy to the traditional reverse sequence.

Adolescent↗
PubMed2000

Treosulfan chemotherapy for recurrent malignant glioma.

Treosulfan is a bifunctional alkylating prodrug with activity against various solid tumors. To improve the outcome for patients with recurrent malignant glioma, we assessed the efficacy of intravenous treosulfan (6-10 g/m2 4-weekly) as salvage therapy for patients with recurrent or progressive glioblastoma (GB, n = 14) or anaplastic astrocytoma (AA, n = 2). All patients had prior involved-field radiotherapy and adjuvant nitrosourea-based chemotherapy. A total of 56 cycles were administered. Tumor responses were assessed radiologically and clinically prior to each cycle. All patients were assessable for toxicity, response and survival. There were no complete or partial responses (CR, PR). Two patients progressed after the first cycle, 14 patients had initially stable disease (SD). Median progression-free survival was 3.25 months for the GB patients. Five patients were progression-free at 6 months (30%), including the 2 AA patients. The 2 AA patients are stable at 22 months. Myelosuppression was the dose-limiting toxicity in this cohort of nitrosourea-pretreated patients. Treosulfan has modest activity in patients with recurrent malignant glioma. Further evaluation of treosulfan in chemonaive malignant glioma patients is warranted.

Adult↗
PubMed2000

Expression of TRAIL receptors in human autoreactive and foreign antigen-specific T cells.

Deletion of T cells due to apoptosis induction is a regulatory mechanism in the human immune system that may be impaired in autoimmune diseases such as multiple sclerosis (MS). Involvement of the apoptosis-mediating CD95/CD95 ligand system in MS has been demonstrated. Here, we report that (auto)antigen-specific human T cells are not killed in vitro by soluble TNF-related apoptosis-inducing ligand (TRAIL) although expressing death-inducing receptors, TRAIL receptor 1 (TRAIL-R1) and TRAIL-R2. Apoptosis was assessed by caspase activation and DNA fragmentation, receptor expression was detected by RT - PCR and flow cytometry. The (auto)antigen-specific T cells were also resistant to specific TRAIL-R1/TRAIL-R2-directed induction of apoptosis, indicating that coexpression of the truncated TRAIL-R3 and TRAIL-R4 in these T cells is not responsible for the observed resistance. Upon stimulation, levels of death-inducing TRAIL receptors decreased whereas TRAIL was up-regulated on the cell surface. In contrast to CD95, the role of TRAIL receptors in MS might not involve regulation of T cell vulnerability.

Apoptosis↗