Regulation of p53-, Bcl-2- and caspase-dependent signaling pathway in xanthorrhizol-induced apoptosis of HepG2 hepatoma cells.
Xanthorrhizol is a sesquiterpenoid compound extracted from the rhizome of Curcuma xanthorrhiza. This study investigated the antiproliferative effect and the mechanism of action of xanthorrhizol on human hepatoma cells, HepG2, and the mode of cell death. An antiproliferative assay using methylene blue staining revealed that xanthorrhizol inhibited the proliferation of the HepG2 cells with a 50% inhibition of cell growth (IC50) value of 4.17 +/- 0.053 microg/ml. The antiproliferative activity of xanthorrhizol was due to apoptosis induced in the HepG2 cells and not necrosis, which was confirmed by the Tdt-mediated dUTP nick end labeling (TUNEL) assay. The xanthorrhizol-treated HepG2 cells showed typical apoptotic morphology such as DNA fragmentation, cell shrinkage and elongated lamellipodia. The apoptosis mediated by xanthorrhizol in the HepG2 cells was associated with the activation of tumor suppressor p53 and down-regulation of antiapoptotic Bcl-2 protein expression, but not Bax. The levels of Bcl-2 protein expression decreased 24-h after treatment with xanthorrhizol and remained lower than controls throughout the experiment, resulting in a shift in the Bax to Bcl-2 ratio thus favouring apoptosis. The processing of the initiator procaspase-9 was detected. Caspase-3 was also found to be activated, but not caspase-7. Xanthorrhizol exerts antiproliferative effects on HepG2 cells by inducing apoptosis via the mitochondrial pathway.
Handayani
Tri
T
School of Biosciences and Biotechnology, Faculty of Science and Technology, National University of Malaysia, 43600 Bangi, Selangor, Malaysia. yani_whaaa@yahoo.com
Sakinah
Sharifah
S
Nallappan
Meenakshii
M
Pihie
Azimahtol Hawariah Lope
AH
D000818:Animals; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D006528:Carcinoma, Hepatocellular / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D020169:Caspases / Q000378:metabolism; D048708:Cell Growth Processes / Q000187:drug effects; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D002522:Chlorocebus aethiops; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D008113:Liver Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D010636:Phenols / Q000494:pharmacology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*; D014709:Vero Cells; D051028:bcl-2-Associated X Protein / Q000378:metabolism*
C494826:BAX protein, human; D010636:Phenols; D019253:Proto-Oncogene Proteins c-bcl-2; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; D051028:bcl-2-Associated X Protein; C120248:xanthorrhizol; D020169:Caspases