Defective cytochrome c-dependent caspase activation in ovarian cancer cell lines due to diminished or absent apoptotic protease activating factor-1 activity.
Apoptosis via the mitochondrial pathway requires release of cytochrome c into the cytosol to initiate formation of an oligomeric apoptotic protease-activating factor-1 (APAF-1) apoptosome. The apoptosome recruits and activates caspase-9, which in turn activates caspase-3 and -7, which then kill the cell by proteolysis. Because inactivation of this pathway may promote oncogenesis, we examined 10 ovarian cancer cell lines for resistance to cytochrome c-dependent caspase activation using a cell-free system. Strikingly, we found that cytosolic extracts from all cell lines had diminished cytochrome c-dependent caspase activation compared with normal ovarian epithelium extracts. The resistant cell lines expressed APAF-1 and caspase-9, -3, and -7; however, each demonstrated diminished APAF-1 activity relative to the normal ovarian epithelium cell lines. A competitive APAF-1 inhibitor may account for the diminished APAF-1 activity because we did not detect dominant APAF-1 inhibitors, altered APAF-1 isoform expression, or APAF-1 deletion, degradation, or mutation. Lack of APAF-1 activity correlated in some but not all cell lines with resistance to apoptosis. These data suggest that regulation of APAF-1 activity may be important for apoptosis regulation in some ovarian cancers.
Wolf
B B
BB
La Jolla Institute for Allergy and Immunology, San Diego, California 92121, USA. ben_wolf@liai.org
Schuler
M
M
Li
W
W
Eggers-Sedlet
B
B
Lee
W
W
Tailor
P
P
Fitzgerald
P
P
Mills
G B
GB
Green
D R
DR
D017209:Apoptosis; D053477:Apoptotic Protease-Activating Factor 1; D015153:Blotting, Western; D053148:Caspase 3; D053179:Caspase 7; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism*; D002460:Cell Line; D002474:Cell-Free System; D003574:Cytochrome c Group / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation; D004847:Epithelial Cells / Q000378:metabolism; D005260:Female; D053804:Granzymes; D006801:Humans; D009154:Mutation; D010051:Ovarian Neoplasms / Q000378:metabolism* / Q000473:pathology; D010053:Ovary / Q000378:metabolism / Q000473:pathology; D020033:Protein Isoforms; D011506:Proteins / Q000235:genetics* / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012697:Serine Endopeptidases / Q000494:pharmacology; D014162:Transfection; D014407:Tumor Cells, Cultured
C506592:APAF1 protein, human; D053477:Apoptotic Protease-Activating Factor 1; D003574:Cytochrome c Group; D020033:Protein Isoforms; D011506:Proteins; C509213:GZMB protein, human; D053804:Granzymes; D012697:Serine Endopeptidases; C505407:CASP3 protein, human; C505520:CASP7 protein, human; C506433:CASP9 protein, human; D053148:Caspase 3; D053179:Caspase 7; D053453:Caspase 9; D020169:Caspases