Formosanin C-induced apoptosis requires activation of caspase-2 and change of mitochondrial membrane potential.
Formosanin C is a pure compound isolated from Paris formosana Hayata (Liliaceae). The antitumor efficacy of formosanin C has been observed in cultured cells and animal systems. However, the molecular mechanisms of formosanin C remain unknown. The results of the present study indicate that formosanin C induced apoptosis of HT-29 cells characterized by exposure of phosphatidylserine, accumulation of cells at the sub-G(1) phase, fragmentation of DNA, and change of nuclear morphology in a time- and dose-related manner. The apoptotic signaling cascades may proceed via proteolytic activation of caspase-2, change of mitochondrial membrane potential (Deltapsi(m)), release of cytochrome c and second mitochondria-derived activator of caspase/direct IAP binding protein with low pI (Smac/DIABLO), activation of caspase-9 and -3, and cleavage of poly(ADP-ribose) polymerase (PARP). Increase in apoptosis-inducing factor and endonuclease G expressions in nuclei, and increase in Bax and Bak expressions and decrease in Bcl-X(L) expression on mitochondria were also observed in formosanin C-treated HT-29 cells. Attenuation of formosanin C-induced change of Deltapsi(m) by caspase-2 inhibitor (Z-VDVAC) implies that caspase-2 acts upstream of the mitochondria. Blockage of formosanin C-induced apoptotic process by using either permeability transition pore inhibitor (cyclosporine A) or caspase-9 inhibitor (Z-LEHD) demonstrates the necessity of mitochondria and caspase-9 in formosanin C-induced apoptosis of HT-29 cells. Taken together, the apoptotic mechanism of formosanin C in human colorectal cancer HT-29 cells involves activation of caspase-2 and the dysfunction of mitochondria.
Lee
Jenq-Chang
JC
Department of Surgery, College of Medicine, National Cheng Kung University, Tainan, Taiwan.
Su
Chun-Li
CL
Chen
Lin-Lin
LL
Won
Shen-Jeu
SJ
D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D051017:Apoptosis Regulatory Proteins; D015153:Blotting, Western; D053143:Caspase 2 / Q000187:drug effects* / Q000378:metabolism; D053148:Caspase 3 / Q000187:drug effects; D053453:Caspase 9 / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D045304:Cytochromes c / Q000187:drug effects; D053938:DNA Fragmentation / Q000187:drug effects; D004144:Diosgenin / Q000031:analogs & derivatives* / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D019073:HT29 Cells; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000187:drug effects; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects*; D024101:Mitochondrial Proteins / Q000187:drug effects; D012503:Saponins / Q000494:pharmacology*
D000970:Antineoplastic Agents; D051017:Apoptosis Regulatory Proteins; C412403:DIABLO protein, human; D047908:Intracellular Signaling Peptides and Proteins; D024101:Mitochondrial Proteins; D012503:Saponins; C067584:formosanin C; D045304:Cytochromes c; D053143:Caspase 2; D053148:Caspase 3; D053453:Caspase 9; D004144:Diosgenin