Biomedical subjects
Publications and source records attributed to M Weller.
Degenerative cerebellar ataxia with autoantibodies against glutamic acid decarboxylase (GAD) is a rare disorder and may represent a subset of ataxias previously classified as idiopathic. The authors report a patient with progressive cerebellar ataxia, insulin-dependent diabetes mellitus, and GAD antibodies who responded to i.v. immunoglobulins.
Gemcitabine is a novel antimetabolite drug that acts by multiple mechanisms, including inhibition of ribonucleoside diphosphate reductase, of dCMP deaminase and of dCTP incorporation into DNA and RNA. Here, we report that gemcitabine induces cytotoxic and clonogenic death of 12 human malignant glioma cell lines at clinically relevant concentrations around 1 microM. Gemcitabine is thus approximately 100-fold more active than the congener drug, cytarabine. Gemcitabine cytotoxicity of glioma cells does not require wild-type p53 activity: (i) there was no difference in the susceptibility to gemcitabine between cell lines with wild-type p53 and cell lines with mutant or deleted p53; (ii) ectopic expression of a temperature-sensitive p53 protein either at wild-type (32.5 degrees C) or at mutant (38.5 degrees C) conformation had no significant influence on gemcitabine-induced cell death. Gemcitabine cytotoxicity was unaffected by the antioxidants, N-acetylcysteine and phenyl-N-tert-butyl-alpha-phenylnitrone. There was no correlation between the susceptibility to gemcitabine and the endogenous expression of the B cell lymphoma-2 (BCL-2)-family proteins BCL-2, BCL-XL, myeloid cell leukemia-1 (MCL-1), BCL-2-associated X protein (BAX), BCL-2 homologous antagonist/killer (BAK) and BCL-XS. Ectopic expression of BCL-2 moderately attenuated gemcitabine-induced cell death. Similarly, preexposure to the synthetic steroid, dexamethasone, which is commonly used to control cerebral edema in brain tumor patients, reduced gemcitabine cytotoxicity. We conclude that the clinical evaluation of gemcitabine for the adjuvant chemotherapy of malignant glioma is warranted.
Ectopic expression of the proteoglycan, decorin, abrogates the growth of experimental C6 gliomas in the rat. Since gliomas release large amounts of transforming growth factor-beta (TGF-beta) and since decorin is a TGF-beta antagonist, decorin gene transfer-mediated abrogation of glioma growth in vivo may involve enhanced immunogenicity of the tumor cells. Here, we report that human glioma cells stimulate alloreactive immune responses when engineered to express decorin whereas parental glioma cells are non-immunogenic in vitro. The alloreactive immune response is mediated by CD8+ and CD4+ T cells as well as by NK cells. The immunosuppression exerted by parental or mock-transfected glioma cells is mediated by soluble factors and can in part be mimicked by exogenous TGF-beta. However, neutralizing anti-TGF-beta antibodies do not reverse glioma-mediated immunosuppression, suggesting that decorin abrogates glioma-induced immune cell inhibition by interfering with the activity of other, so far unidentified glioma-secreted mediators. We conclude that enhanced immunogenicity may mediate the antineoplastic effects of decorin gene therapy for malignant glioma but that factors other than TGF-beta may be responsible for glioma-induced immunosuppression.
Apoptosis is one of the most exciting and intensely investigated areas of biology and medicine today. Cysteine proteases called caspases serve as the executioners of apoptosis, a form of cell suicide. Hypoxic/ischemic cell death proceeds in part, by apoptosis, particularly within the periinfarct zone or ischemic penumbra. During ischemia, activated caspases dismantle the cell by cleaving multiple substrates including cytoskeletal proteins and enzymes essential for cell repair. Strategies that inhibit caspase activity block cell death in experimental models of mild ischemia, and preserve neurological function. The therapeutic window for caspase inhibition is substantially longer than for glutamate receptor antagonists, and treatment combinations with both classes of drugs decrease ischemic injury and expand the treatment window synergistically. Hence, the caspases are now recognized as novel therapeutic targets for central nervous system diseases in which cell death is prominent. This article will review the evidence and the potential importance of caspase inhibition to cerebral ischemia and briefly summarize an emerging body of data implicating caspases in cell death accompanying neurodegenerative disorders.
In an effort to develop more effective forms of adjuvant chemotherapy for malignant brain tumors, we sought to develop a taxol-based combination chemotherapy regimen for glioma cell lines in vitro. Here, we report that coexposure of LN-229 or T98G glioma cells to taxol and either doxorubicin, camptothecin, cytarabine, or VM26 resulted in antagonistic effects rather than additive or synergistic cytotoxicity. There were no interactions of taxol with the effects of carmustine (BCNU) or vincristine. Antagonism was more prominent in cytotoxic cell death assays than in clonogenic cell death assays and was not overcome by G2/M checkpoint abrogators such as caffeine or pentoxyfilline. Ectopic expression of mutant and wild-type p53val135 attenuated taxol cytotoxicity in both T98G cells, which are mutant for p53, and LN-229 cells, which exhibit functional wild-type p53 activity. Interestingly, wild-type p53val135 abrogated the taxol-imposed G2/M arrest in both cell lines. However, wild-type p53val135 did not promote glioma cell killing by combinations of taxol and any of the other drugs. Further, an analysis of a panel of 12 human glioma cell lines revealed no relationship between genetic or functional p53 status and taxol sensitivity. In summary, combination either with other chemotherapy drugs, with abrogators of the G2/M checkpoint, with wild-type p53 gene transfer was not a promising approach for a taxol-based combination chemotherapy regimen in malignant glioma.
AP02 ligand (APO2L) is a CD95 ligand (CD95L)-related cytokine of the tumor necrosis factor family that interacts with agonistic (DR4, DR5) and antagonistic (DcR1, DcR2) receptors. Cultured malignant glioma cells preferentially express agonistic receptors and are susceptible to APO2L-induced apoptosis. Here, we report that 8 of 8 human glioma cell lines expressed APO2L mRNA and protein in vitro. Immunohistochemistry using a monoclonal antibody to APO2L revealed that all 23 primary astrocytic brain tumors analyzed, including low-grade astrocytomas and glioblastomas, express APO2L in vivo. With the exception of reactive astrocytes, non-neoplastic glia and neurons in the cerebrum lacked immunoreactivity of APO2L. Thus, in addition to the CD95/CD95L system, a second death ligand/death receptor pair may regulate susceptibility to apoptosis in human glial neoplasms.
We studied the substantia nigra of three Parkinson's disease (PD) patients and three age-matched individuals by in situ DNA-end labeling (ISEL) and immunohistochemistry for the apoptosis regulating proteins Bcl-2, Bax and Bcl-x on 50 consecutive sections per patient. No melanin-containing cell was identified with typical apoptotic changes in either patient or control substantia nigra. With prolonged reaction-time the terminal transferase-mediated DNA-end labeling revealed a signal in 2.0 +/-1.2% melanin-containing cells in PD compared to 1.3 +/-1.1% in control. This difference did nor reach statistical significance and no condensation or margination of the chromatin was evident. No significant changes of any of the apoptosis regulating proteins were apparent in PD substantia nigra. These findings do not support the hypothesis that apoptosis plays a central role in the pathogenesis of PD.
Cyclooxygenases (COX, prostaglandin endoperoxide synthases, PGG/H synthases) are potent mediators of inflammation. While COX-1 is constitutively expressed in a wide range of tissues, COX-2 is cytokine inducible. Although COX-1 expression is observed in normal tissue, enhanced COX-2 expression has been attributed a key role in the development of edema, impeding blood flow and immunomodulation observed in pathologically altered tissues. Here, we have analyzed the expression of COX-1 and COX-2 in 50 gliomas and 10 control brains with no neuropathological alterations by immunohistochemistry; 22 glioblastoma multiforme, 9 anaplastic astrocytomas, 5 protoplasmic astrocytomas, 1 gemistocytic astrocytoma and 13 fibrillary astrocytomas were included in the study. Compared with control brains, accumulation of COX-1 was detected in 20-50% of all cells in both low- and high-grade gliomas. Double-labeling experiments revealed COX-1 expression in subsets of macrophages/microglial cells within the tumor parenchyma and in areas of infiltrative tumor growth. Of the COX-1-positive cells, 90% expressed MHC class II antigens. No COX-1 immunoreactivity was observed in tumor cells. COX-2-positive cells accumulated in tumor cells and in single macrophages/microglial cells in the immediate vicinity of necroses. Further studies are required to determine whether COX-2 is involved in the development of necrosis or, more likely, whether COX-2 is a part of the tumor tissue response to necrosis.
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This study sought to identify abnormalities in the levels of iron transport proteins in patients with superficial siderosis of the central nervous system. We compared patients with superficial siderosis (n = 7) with patients suffering from various other neurological disorders (n = 176, total). CSF and serum levels of lactoferrin, and CSF levels of transferrin were measured by enzyme-linked immunosorbent assay. Serum transferrin was measured by nephelometry. Lactoferrin, but not transferrin, levels in the CSF were significantly elevated in superficial siderosis. Unexpectedly, CSF transferrin was decreased in multiple sclerosis patients. Enhanced CSF lactoferrin may reflect an increased iron transport requirement in the central nervous system in superficial siderosis and might be a useful measure for monitoring response to therapy.
Decorin is a member of the small leucine-rich proteoglycan (SLRP) gene family that has recently become a focus in various areas of cancer research. The decorin protein consists of a core protein and a covalently linked glycosaminoglycan chain. Decorin binds to collagens type I, II and IV in vivo and promotes the formation of fibers with increased stability and changes in solubility. Further, the decorin core protein binds to growth factors, including transforming growth factor-beta (TGF-beta), to other intercellular matrix molecules such as fibronectin and thrombospondin, and to the decorin endocytosis receptor. Decorin may directly interfere with the cell cycle via the induction of p21WAF1/CIP1 (p21), a potent inhibitor of cyclin-dependent kinases (CDKs). Here, we discuss interactions of decorin with TGF-beta and with p21, both of which are relevant to carcinogenesis and tumor progression. TGF-beta is released by tumors of various histogenetic origins and promotes immunosuppression in the host and tumor immune escape by induction of growth arrest and apoptosis in immune cells, by downregulation of MHC II antigen expression and by changes in the cytokine release profiles of immune and tumor cells. Moreover, TGF-beta may modulate tumor growth in an autocrine and paracrine fashion, may mediate drug resistance, and may facilitate tumor angiogenesis. Decorin binds to TGF-beta, thus inhibiting its bioactivity, and is a direct or indirect negative modulator of TGF-beta synthesis. Ectopic expression of decorin results in the regression of rat C6 gliomas, an antineoplastic effect attributed to the reversal of TGF-beta-induced immunosuppression. On the other hand, de novo expression of decorin in colon cancer cells and some other tumor cells, even though not in glioma cells, results in an upregulation of p21 expression and a cell cycle arrest, presumably in a TGF-beta-independent manner. Decorin expression is downregulated in many tumors but upregulated in the peritumoral stroma. By virtue of its growth regulatory and immunomodulatory properties, decorin promises to become a novel target for the experimental therapy of human cancers.
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Glucocorticoid therapy may result in the rapid resolution of cerebral mass lesions in patients with primary CNS lymphoma. Since glucocorticoids will obscure the histological diagnosis of primary CNS lymphoma upon biopsy, steroids should be withheld if primary CNS lymphoma is a likely diagnosis by neuroradiological criteria. The lympholytic effect of glucocorticoids is mediated by cytoplasmic steroid receptors which are translocated to the nucleus and signal apoptosis. Glucocorticoid-induced apoptosis of lymphoid cells does not require wild-type p53 activity, seems not to depend on caspase activation, but is attenuated by the bcl-2 protooncogene product. Longterm glucocorticoid therapy of primary CNS lymphoma is not recommended because relapse is probably inevitable and because of the prominent side effects of long-term glucocorticoid treatment. Further, long-term glucocorticoid treatment is contraindicated in immunocompromised patients with primary CNS lymphoma.
Steroids are essential for the control of oedema in human malignant glioma patients but may interfere with the efficacy of chemotherapy. Boswellic acids are phytotherapeutic anti-inflammatory agents that may be alternative drugs to corticosteroids in the treatment of cerebral oedema. Here, we report that boswellic acids are cytotoxic to malignant glioma cells at low micromolar concentrations. In-situ DNA end labelling and electron microscopy reveal that boswellic acids induce apoptosis. Boswellic acid-induced apoptosis requires protein, but not RNA synthesis, and is neither associated with free radical formation nor blocked by free radical scavengers. The levels of BAX and BCL-2 proteins remain unaltered during boswellic acid-induced apoptosis. p21 expression is induced by boswellic acids via a p53-independent pathway. Ectopic expression of wild-type p53 also induces p21, and facilitates boswellic acid-induced apoptosis. However, targeted disruption of the p21 genes in colon carcinoma cells enhances rather than decreases boswellic acid toxicity. Ectopic expression of neither BCL-2 nor the caspase inhibitor, CRM-A, is protective. In contrast to steroids, subtoxic concentrations of boswellic acids do not interfere with cancer drug toxicity of glioma cells in acute cytotoxicity or clonogenic cell death assays. Also, in contrast to steroids, boswellic acids synergize with the cytotoxic cytokine, CD95 ligand, in inducing glioma cell apoptosis. This effect is probably mediated by inhibition of RNA synthesis and is not associated with changes of CD95 expression at the cell surface. Further studies in laboratory animals and in human patients are required to determine whether boswellic acids may be a useful adjunct to the medical management of human malignant glioma.
The inhibitor-of-apoptosis (IAP) proteins are a novel family of antiapoptotic proteins that are thought to inhibit cell death via direct inhibition of caspases. Here, we report that human malignant glioma cell lines express XIAP, HIAP-1 and HIAP-2 mRNA and proteins. NAIP was not expressed. IAP proteins were not cleaved during CD95 ligand (CD95L)-induced apoptosis, and loss of IAP protein expression was not responsible for the potentiation of CD95L-induced apoptosis when protein synthesis was inhibited. LN-18 cells are highly sensitive to CD95-mediated apoptosis, whereas LN-229 cells require co-exposure to CD95L and a protein synthesis inhibitor, CHX, to acquire sensitivity to apoptosis. Adenoviral XIAP gene transfer blocked caspase 8 and 3 processing in both cell lines in the absence of CHX. Apoptosis was blocked in the absence and in the presence of CHX. However, XIAP failed to block caspase 8 processing in LN-229 cells in the presence of CHX. There was considerable overlap of the effects of XIAP on caspase processing with those of BCL-2 and the viral caspase inhibitor crm-A. These data define complex regulatory mechanisms for CD95-mediated apoptosis in glioma cells and indicate that there may be a distinct pathway of death receptor-mediated apoptosis that is readily activated when protein synthesis is inhibited. The constitutive expression of natural caspase inhibitors may play a role in the resistance of these cells to apoptotic stimuli that directly target caspases, including radiochemotherapy and immune-mediated tumor cell lysis.
The inhibitor of apoptosis (IAP) family of antiapoptotic genes, originally discovered in baculovirus, exists in animals ranging from insects to humans. Here, we investigated the ability of IAPs to suppress cell death in both a neuronal model of apoptosis and excitotoxicity. Cerebellar granule neurons undergo apoptosis when switched from 25 to 5 mM potassium, and excitotoxic cell death in response to glutamate. We examined the endogenous expression of four members of the IAP family, X chromosome-linked IAP (XIAP), rat IAP1 (RIAP1), RIAP2, and neuronal apoptosis inhibitory protein (NAIP), by semiquantitative reverse PCR and immunoblot analysis in cultured cerebellar granule neurons. Cerebellar granule neurons express significant levels of RIAP2 mRNA and protein, but expression of RIAP1, NAIP, and XIAP was not detected. RIAP2 mRNA content and protein levels did not change when cells were switched from 25 to 5 mM potassium. To determine whether ectopic expression of IAP influenced neuronal survival after potassium withdrawal or glutamate exposure, we used recombinant adenoviral vectors to target XIAP, human IAP1 (HIAP1), HIAP2, and NAIP into cerebellar granule neurons. We demonstrate that forced expression of IAPs efficiently blocked potassium withdrawal-induced N-acetyl-Asp-Glu-Val-Asp-specific caspase activity and reduced DNA fragmentation. However, neurons were only protected from apoptosis up to 24 h after potassium withdrawal, but not at later time points, suggesting that IAPs delay but do not block apoptosis in cerebellar granule neurons. In contrast, treatment with 100 microM or 1 mM glutamate did not induce caspase activity and adenoviral-mediated expression of IAPs had no influence on subsequent excitotoxic cell death.
Spinocerebellar ataxia type 3 (SCA3) is caused by a CAG/polyglutamine repeat expansion in the SCA3 gene. To analyse the pathogenic mechanisms in SCA3, we have generated ataxin-3-expressing rat mesencephalic CSM14.1 cells. In these cells, a post-mitotic neuronal phenotype is induced by temperature shift. The isolated stable cell lines provided high level expression of non-expanded (Q23) or expanded (Q70) human full-length ataxin-3. CSM14.1 cells expressing the expanded full-length ataxin-3 developed nuclear inclusion bodies, strong indentations of the nuclear envelope and cytoplasmic vacuolation. These ultrastructural alterations were present prior to a significantly decreased viability of neuronally differentiated cells expressing expanded ataxin-3. The observed spontaneous cell death did not correlate with formation of intranuclear inclusions and was not apoptotic by ultrastructural analysis. No increased susceptibility to staurosporine-induced apoptosis was found for the expanded or non-expanded ataxin-3-expressing cell lines. These data show that high level expression of expanded full-length ataxin-3 in a neuron-like cell line generates ultrastructural alterations of SCA3 pathogenesis and results in increased spontaneous non-apoptotic cell death.
OBJECTIVE: In vitro studies indicate a role of apoptosis regulatory proteins of the BCL-2 family in the resistance of glioblastoma multiforme to irradiation and chemotherapy. To date, no study has compared the expression of these proteins in initial and recurrent tumours. The differences of expression of BCL-2, BCL-X, BAX, and MCL-1 proteins of paired first resection and recurrence glioblastoma specimens were examined. METHODS: Immunohistochemistry was performed in 37 cases of glioblastoma multiforme with paraffin embedded tissue from first resections and their recurrences in three treatment groups (15 radiochemotherapy, 15 irradiation, seven untreated). Ten high power fields were evaluated with an arbitrary score (< 5%=1, 5-50%=2, >50%=3), and cumulative scores for each antigen calculated. RESULTS: In the whole group, we found a significant up regulation of antiapoptotic BCL-2 (median cumulative score of 15 in the primary, 19 at recurrence; p<0.0001 in the Wilcoxon test), BCLX (median scores 20 and 25, respectively, p<0.0001), and MCL-1 (median scores 11 and 14, p=0.0395), and a significant down regulation of proapoptotic BAX (median scores 14 and 11, p<0.0001). In the subgroups, these trends were also found. No association between protein expression and treatment regimen was found, although significant changes were restricted to the subgroups that received adjuvant chemotherapy. No significant correlation with clinical prognosis was detected with the Kaplan-Meier method. CONCLUSIONS: In the development from initial to recurrent glioblastoma multiforme, the BCL-2 family rheostat shifts towards antiapoptotic adjustment in vivo. Importantly, the changes in BCL-2 family protein expression characterised here were also seen in the subgroup of patients who did not receive adjuvant radiotherapy or chemotherapy, suggesting that the changes of BCL-2 family protein expression result not only from radiochemotherapy but also reflect the natural course of disease.