The combination of calmodulin antagonists and interferon-gamma induces apoptosis through caspase-dependent and -independent pathways in cholangiocarcinoma cells.
Calmodulin (CaM) antagonists have been shown to inhibit tumor cell invasion and metastasis and to induce apoptosis in various tumor models, but the molecular mechanism of CaM antagonist-mediated apoptosis is poorly understood. Here, we demonstrate that interferon (IFN)-gamma induces susceptibility to CaM antagonist-mediated apoptosis in human cholangiocarcinoma cells weakly expressing Fas (Fas-low cells). During CaM antagonist-mediated apoptosis in IFN-gamma-pretreated Fas-low cells, cleavage of caspases-8, -9, and -3 and Bid, release of cytochrome c from the mitochondria and an increase in the free cytosolic calcium concentration were observed. CaM antagonists also caused depolarization of the mitochondrial membrane independent of caspase activation. Although a broad-range caspase inhibitor partially blocked CaM antagonist-mediated apoptosis, the neutralizing Fas antibody had no effect, suggesting that CaM antagonist-mediated apoptosis does not require interaction between CaM antagonists and surface Fas. CaM antagonists induce apoptosis via mechanisms other than inhibition of CaM-dependent protein kinase II and calcineurin, as their inhibitors, KN93 and cyclosporine A, had no effect on apoptosis. Taken together, these results indicate that CaM antagonists induce apoptosis in both caspase-dependent and -independent manners, and that susceptibility to CaM antagonists is modulated by IFN-gamma. The combination of IFN-gamma and CaM antagonists, including tamoxifen, may be a potential therapeutic modality for cholangiocarcinoma and possibly other malignancies.
Department of Pathology, The University of Alabama at Birmingham, 1530 3rd Avenue South, Birmingham, AL 35294-0007, USA.
Eun-Young
EY
Ahn
George
G
Pan
Jae Hwan
JH
Oh
Ewan M
EM
Tytler
Jay M
JM
McDonald
D017209:Apoptosis / Q000187:drug effects*; D051023:BH3 Interacting Domain Death Agonist Protein; D015153:Blotting, Western; D002147:Calmodulin / Q000037:antagonists & inhibitors*; D002352:Carrier Proteins / Q000187:drug effects / Q000378:metabolism; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism*; D045744:Cell Line, Tumor; D018281:Cholangiocarcinoma / Q000378:metabolism / Q000473:pathology; D003574:Cytochrome c Group / Q000187:drug effects / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology*; D008564:Membrane Potentials / Q000187:drug effects; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D019014:fas Receptor / Q000235:genetics
D051023:BH3 Interacting Domain Death Agonist Protein; C494814:BID protein, human; D002147:Calmodulin; D002352:Carrier Proteins; D061945:Caspase Inhibitors; D003574:Cytochrome c Group; D004791:Enzyme Inhibitors; D019014:fas Receptor; C076615:cytochrome c''; D007371:Interferon-gamma; D020169:Caspases