Activation of c-Jun N-terminal kinase 1 and caspase 3 in the tamoxifen-induced apoptosis of rat glioma cells.
OBJECTIVE
The mechanisms of the antitumor effects of tamoxifen upon gliomas are still unclear. In this study, we investigated the role of c-Jun N-terminal kinase-1 (JNK1) and caspase 3 in the tamoxifen-induced apoptosis of rat glioma cells.


METHODS
Glioma cells were treated with tamoxifen, followed by a cytotoxicity assay to study its effects on the cells, and then a flow-activated cell sorter (FACS) analysis was performed to analyze the cellular apoptosis of the glioma cells. The expression of JNK1 and phospho-specific JNK1 in glioma cells treated with tamoxifen was investigated by Western blot analysis. The activity of caspase 3 in glioma cells was analyzed by caspase activity assay.


RESULTS
Tamoxifen was demonstrated to exert cytotoxic effects upon and induced apoptosis of the glioma cells in a concentration- and time-dependent manner (P<0.05). Western blot analysis demonstrated that tamoxifen increased the expression of phospho-specific JNK1 in glioma cells, and an increasing concentration of tamoxifen induced an increasing expression of phospho-specific JNK1. Four-hour 50-microM tamoxifen treatment increased the expression of phospho-specific JNK1 to 3.2 times that of the control level in glioma cells. Tamoxifen also increased the activity of caspase 3 in glioma cells. Pretreatment of glioma cells with the antisense oligonucleotide (OGN) of JNK1 immediately prior to tamoxifen treatment suppressed the expression of phospho-specific JNK1 and the activity of caspase 3. The apoptosis fraction of glioma cells induced by 4-h treatment with 50 microM tamoxifen was decreased from 51% to 28% by pretreatment with the antisense OGN of JNK1 (P<0.003), and to 20% by pretreatment with caspase 3 inhibitor (DEVD-CHO) (P<0.0008).


CONCLUSIONS
The results suggest that the tamoxifen-induced apoptosis of rat glioma cells is related to the activation of the JNK1/caspase 3 signaling pathway; however, the confirmation of the occurrence of such activation in vivo needs further investigation.
Department of Surgery, National Taiwan University Hospital and National Taiwan University College of Medicine, 7 Chung-Shan S. Road, Taipei, Taiwan.
Sheng-Hong
SH
Tseng
Chih-Hsien
CH
Wang
Swei-Ming
SM
Lin
Chia-Kang
CK
Chen
Hsin-Yi
HY
Huang
Yun
Y
Chen
D000818:Animals; D016588:Anticarcinogenic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D001932:Brain Neoplasms / Q000201:enzymology / Q000473:pathology; D053148:Caspase 3; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism*; D002455:Cell Division / Q000187:drug effects; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005910:Glioma / Q000201:enzymology / Q000473:pathology*; D020287:In Situ Nick-End Labeling; D048055:Mitogen-Activated Protein Kinase 8; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D010766:Phosphorylation; D051381:Rats; D015398:Signal Transduction; D013629:Tamoxifen / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
D016588:Anticarcinogenic Agents; D061945:Caspase Inhibitors; D004791:Enzyme Inhibitors; D016376:Oligonucleotides, Antisense; D013629:Tamoxifen; D048055:Mitogen-Activated Protein Kinase 8; D020928:Mitogen-Activated Protein Kinases; C505410:Casp3 protein, rat; D053148:Caspase 3; D020169:Caspases