Effector mechanisms of norcantharidin-induced mitotic arrest and apoptosis in human hepatoma cells.
NCTD is a demethylated form of cantharidin with antitumor properties, which is now in use as a routine anticancer drug against hepatoma. However, there is limited information on the effect of NCTD on human cancer cells. In the present study, NCTD inhibited proliferation, caused mitotic arrest, then progressed to apoptosis within 96 hr in 3 human hepatoma cell lines: HepG2, Hep3B and Huh-7. NCTD treatment (5 microg/ml) enhanced the expression of Cdc25C and p21(Cip1/Waf1), increasing the phosphorylation of these 2 proteins. In addition, NCTD treatment induced an earlier increase in cyclin B1-associated histone H1 kinase activity within 48 hr, but an approximately 70% reduction of both protein level and kinase activity of cyclin B1 was observed at 72 hr. Treatment with NCTD significantly decreased the expression of p53 protein but did not affect the expression of Cdk1 and p27(Kip1). Moreover, NCTD treatment also increased the phosphorylation of Bcl-2 and Bcl-X(L) but did not affect the expression of Bax or Bad. Bcl-2 phosphorylation appears to inhibit its binding to Bax since less Bax was detected in immunocomplex with Bcl-2 in NCTD-treated HepG2 cells. In addition, NCTD treatment caused activation of caspase-9 and caspase-3, preceding DNA fragmentation and morphologic features of apoptosis. Pretreatment with the broad-spectrum caspase inhibitor z-VAD-fmk markedly inhibited NCTD-induced caspase-3 activity and cell death. These results suggest that phosphorylation of p21(Cip1/Waf1) and Cdc25C and biphasic regulation of cyclin B1-associated kinase activity may contribute to NCTD-induced M-phase cell-cycle arrest. Furthermore, the increase of p21(Cip1/Waf1), phosphorylation of Bcl-2 and Bcl-X(L), activation of caspase-9 and caspase-3 may be the molecular mechanism through which NCTD induces apoptosis.
School of Chinese Medicine, China Medical College, Taichung, Taiwan.
Yan-Nian
YN
Chen
Jung-Chou
JC
Chen
Sui-Chu
SC
Yin
Guang-Sheng
GS
Wang
Wei
W
Tsauer
Sheng-Feng
SF
Hsu
Shih-Lan
SL
Hsu
D017304:Annexin A5 / Q000378:metabolism; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology*; D006528:Carcinoma, Hepatocellular / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D002352:Carrier Proteins / Q000378:metabolism; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000378:metabolism; D006801:Humans; D008113:Liver Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D008840:Microfilament Proteins / Q000378:metabolism; D008938:Mitosis / Q000187:drug effects*; D009124:Muscle Proteins; D011494:Protein Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D014407:Tumor Cells, Cultured / Q000187:drug effects; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism; D051028:bcl-2-Associated X Protein; D051025:bcl-Associated Death Protein
D017304:Annexin A5; D000970:Antineoplastic Agents; C494819:BAD protein, human; C494826:BAX protein, human; D019086:Bridged Bicyclo Compounds, Heterocyclic; C493956:CDKN1A protein, human; D002352:Carrier Proteins; D061945:Caspase Inhibitors; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D008840:Microfilament Proteins; D009124:Muscle Proteins; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; C058992:Tagln protein, mouse; D016159:Tumor Suppressor Protein p53; D051028:bcl-2-Associated X Protein; D051025:bcl-Associated Death Protein; C069741:norcantharidin; D011494:Protein Kinases; C102333:histone H1 kinase; D020169:Caspases