acetyl-aspartyl-glutamyl-valyl-aspartal and Glioma

Irradiation is one of the cornerstones used in the treatment of malignant glioma. However, the effect is modest and glioma cells generally display a pronounced radio-resistance. In this study, the effect of irradiation, alone and in combination with the antimicrotubule drug estramustine (EaM), was investigated in vitro using the BT4C rat glioma cell line, and in vivo the BT4C rat intracerebral glioma model was used. Apoptosis was detected by analysing DNA laddering, in situ end labelling (ISEL) and Annexin V reactivity. In addition, phosphorylation status of MAPK, JNK, p38, and AKT, proteins involved in pro- and anti-apoptotic signalling pathways was analysed by Western blotting. Irradiation did not induce apoptosis, neither in vitro nor in vivo. EaM, however, induced apoptosis in vivo and in vitro, regardless of whether EaM was given alone, before or after irradiation. When BT4C cells were treated with the caspase-3 inhibitor Ac-DEVD-CHO prior to EaM, the number of apoptotic cells was decreased, indicating an involvement of caspase-3. The signalling pathways regulating apoptosis are complex and involve kinases such as MAPK, JNK, p38 and AKT. Irradiation did not induce any changes in the expression levels or phosphorylation status of these proteins. On the other hand, the phosphorylation level of AKT was reduced after EaM treatment, which might, in part, propose how EaM induces apoptosis in glioma cells.

Topics: Animals; Antineoplastic Agents, Alkylating; Apoptosis; Brain Neoplasms; Caspase Inhibitors; Caspases; Cysteine Proteinase Inhibitors; Enzyme Activation; Estramustine; Glioma; JNK Mitogen-Activated Protein Kinases; MAP Kinase Kinase 4; Mitogen-Activated Protein Kinase Kinases; Mitogen-Activated Protein Kinases; Oligopeptides; p38 Mitogen-Activated Protein Kinases; Protein Serine-Threonine Kinases; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-akt; Rats; Signal Transduction; Tumor Cells, Cultured

Fas ligand is a potent inducer of apoptosis in human glioma cells by the Fas/Fas ligand pathway. With comparable efficiency, metalloprotease inhibitors including puromycin and bestatin induce apoptosis in glioma cells. To evaluate the involvement of potential components involved in Fas ligand- and metalloprotease inhibitor-induced apoptosis, we investigated the effect of anti human Fas antibody, soluble Fas ligand and puromycin on cultures of human malignant glioma cell lines (LN-18, LN-229, T98G). Stimulation with Fas ligand lead to apoptotic cell death within 16 h. Costimulation with the translational inhibitor cycloheximide and the transcription blocker actinomycin D did not reduce Fas ligand toxicity. In contrast, apoptosis induced by puromycin was blocked by cycloheximide and decreased by subtoxic doses of actinomycin D in all three gliomas. Whereas inhibition of caspase activity with the general inhibitor zVAD-fmk resulted in a complete block of Fas ligand-induced cell death, puromycin-mediated apoptosis was found to be unaffected by zVAD-fmk as well as by more specific inhibitors for caspase-1 (Interleukin-1 beta converting enzyme) and caspase-3 (CPP32/Yama). Other prominent components involved in many apoptotic pathways as bcl-2 and reactive oxygen intermediates were also examined. Bcl-2 which protects glioma cells from Fas ligand-induced cell death, was shown to have only a small protective effect on puromycin-induced apoptosis. The tested radical scavengers did not reduce Fas- or puromycin-mediated killing of human glioma cells.

Topics: Amino Acid Chloromethyl Ketones; Antibodies, Monoclonal; Apoptosis; Caspase 1; Cell Survival; Cycloheximide; Cysteine Endopeptidases; Cysteine Proteinase Inhibitors; Dactinomycin; Fas Ligand Protein; fas Receptor; Free Radical Scavengers; Glioma; Humans; Leucine; Membrane Glycoproteins; Oligopeptides; Proto-Oncogene Proteins c-bcl-2; Puromycin; Transfection; Tumor Cells, Cultured