Mechanisms for the magnolol-induced cell death of CGTH W-2 thyroid carcinoma cells.
Magnolol, a substance purified from the bark of Magnolia officialis, inhibits cell proliferation and induces apoptosis in a variety of cancer cells. The aim of this study was to study the effects of magnolol on CGTH W-2 thyroid carcinoma cells. After 24 h treatment with 80 microM magnolol in serum-containing medium, about 50% of the cells exhibited apoptotic features and 20% necrotic features. Cytochrome-c staining was diffused in the cytoplasm of the apoptotic cells, but restricted to the mitochondria in control cells. Western blot analyses showed an increase in levels of activated caspases (caspase-3 and -7) and of cleaved poly (ADP-ribose) polymerase (PARP) by magnolol. Concomitantly, immunostaining for apoptosis inducing factor (AIF) showed a time-dependent translocation from the mitochondria to the nucleus. Inhibition of either PARP or caspase activity blocked magnolol-induced apoptosis, supporting the involvement of the caspases and PARP. In addition, magnolol activated phosphatase and tensin homolog deleted on chromosome 10 (PTEN) and inactivated Akt by decreasing levels of phosphorylated PTEN and phosphorylated Akt. These data suggest that magnolol promoted apoptosis probably by alleviating the inhibitory effect of Akt on caspase 9. Furthermore, inhibition of PARP activity, but not of caspase activity, completely prevented magnolol-induced necrosis, suggesting the notion that it might be caused by depletion of intracellular ATP levels due to PARP activation. These results show that magnolol initiates apoptosis via the cytochrome-c/caspase 3/PARP/AIF and PTEN/Akt/caspase 9/PARP pathways and necrosis via PARP activation.
Huang
Shih-Horng
SH
Department of Surgery and Division of General Surgery, Far Eastern Memorial Hospital, Taipei, Taiwan.
Chen
Ying
Y
Tung
Po-Yuan
PY
Wu
Jiahn-Chun
JC
Chen
Kuo-Hsin
KH
Wu
Jiann-Ming
JM
Wang
Seu-Mei
SM
D017209:Apoptosis / Q000187:drug effects*; D051033:Apoptosis Inducing Factor / Q000378:metabolism; D001713:Biphenyl Compounds / Q000494:pharmacology*; D015153:Blotting, Western; D053148:Caspase 3 / Q000378:metabolism; D053179:Caspase 7 / Q000378:metabolism; D045744:Cell Line, Tumor; D045304:Cytochromes c / Q000378:metabolism; D005434:Flow Cytometry; D006801:Humans; D007150:Immunohistochemistry; D017705:Lignans / Q000494:pharmacology*; D009336:Necrosis / Q000139:chemically induced; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D013964:Thyroid Neoplasms / Q000378:metabolism / Q000473:pathology
D051033:Apoptosis Inducing Factor; D001713:Biphenyl Compounds; D017705:Lignans; C005498:magnolol; D045304:Cytochromes c; D011065:Poly(ADP-ribose) Polymerases; D053148:Caspase 3; D053179:Caspase 7