Mitochondria from TRAIL-resistant prostate cancer cells are capable of responding to apoptotic stimuli.
TNFalpha-related apoptosis inducing ligand (TRAIL) has been shown to induce apoptosis in prostate cancer cells. However, some prostate cancer cells, such as LNCaP are resistant to TRAIL. In addition to the involvement of several pathways in the TRAIL-resistance of LNCaP, it has been shown that mitochondrial response to TRIAL is low in these cells. Therefore, in this study, using in vitro cell free and reconstitution models, we have demonstrated that mitochondria from these cells are capable of responding to apoptotic stimuli. Furthermore, experiments to determine the influence of cytochrome c on apoptotic response noted that incubation of cytosol with exogenous cytochrome c induced truncation of Bid. We have demonstrated that truncation of Bid by exogenous cytochrome c is mediated through the activation of caspases-9 and -3. Incubation of cytosol with recombinant caspases-9 and -3 in the absence or presence of inhibitors showed that activation of caspase-9, leading to the activation of caspase-3 was necessary for the truncation of Bid. Published results indicate that in apoptotic cells cytochrome c is released from the mitochondria in two installments, an early small amount and a late larger amount. Our results suggest that the initial release of cytochrome generates tBid that is capable of translocation into the mitochondria causing further release of cytochrome c. Thus, in addition to providing functional explanation for the biphasic release of cytochrome c from mitochondria, we demonstrate the presence of a feedback amplification of mitochondrial apoptotic signal.
Liang
Yayun
Y
Section of Urology, Medical College of Georgia, 15th Street, Augusta, GA 30912, USA.
Eid
Manal A
MA
Lewis
Ronald W
RW
Kumar
M Vijay
MV
D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D017209:Apoptosis / Q000502:physiology*; D051017:Apoptosis Regulatory Proteins; D051023:BH3 Interacting Domain Death Agonist Protein; D002352:Carrier Proteins / Q000378:metabolism; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism; D002458:Cell Fractionation; D045744:Cell Line, Tumor; D002474:Cell-Free System / Q000187:drug effects / Q000378:metabolism; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D045304:Cytochromes c / Q000378:metabolism; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D019008:Drug Resistance, Neoplasm; D006801:Humans; D008297:Male; D008562:Membrane Glycoproteins / Q000494:pharmacology*; D008928:Mitochondria / Q000378:metabolism / Q000502:physiology*; D008954:Models, Biological; D011471:Prostatic Neoplasms / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D021381:Protein Transport; D053221:TNF-Related Apoptosis-Inducing Ligand; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
D000590:Amino Acid Chloromethyl Ketones; D051017:Apoptosis Regulatory Proteins; D051023:BH3 Interacting Domain Death Agonist Protein; C494814:BID protein, human; D002352:Carrier Proteins; D061945:Caspase Inhibitors; D015853:Cysteine Proteinase Inhibitors; D008562:Membrane Glycoproteins; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; D014409:Tumor Necrosis Factor-alpha; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; D045304:Cytochromes c; C505407:CASP3 protein, human; C505530:CASP8 protein, human; C506433:CASP9 protein, human; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases