The antimicrotubule drug estramustine but not irradiation induces apoptosis in malignant glioma involving AKT and caspase pathways.
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.
Vallbo
Christina
C
Department of Radiation Sciences, Umeå University, Sweden.
Bergenheim
Tommy
T
Hedman
Håkan
H
Henriksson
Roger
R
D000818:Animals; D018906:Antineoplastic Agents, Alkylating / Q000494:pharmacology* / Q000627:therapeutic use; D017209:Apoptosis / Q000187:drug effects / Q000528:radiation effects; D001932:Brain Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000532:radiotherapy*; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects / Q000528:radiation effects; D004961:Estramustine / Q000494:pharmacology*; D005910:Glioma / Q000188:drug therapy* / Q000378:metabolism / Q000532:radiotherapy*; D048031:JNK Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009842:Oligopeptides / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects / Q000528:radiation effects; D014407:Tumor Cells, Cultured; D048051:p38 Mitogen-Activated Protein Kinases
D018906:Antineoplastic Agents, Alkylating; D061945:Caspase Inhibitors; D015853:Cysteine Proteinase Inhibitors; D009842:Oligopeptides; D011518:Proto-Oncogene Proteins; C099158:acetyl-aspartyl-glutamyl-valyl-aspartal; D004961:Estramustine; C494920:Akt1 protein, rat; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D020929:Mitogen-Activated Protein Kinase Kinases; D020169:Caspases