Adenoviral melanoma differentiation-associated gene 7 induces apoptosis in lung cancer cells through mitochondrial permeability transition-independent cytochrome c release.
OBJECTIVE
Melanoma differentiation-associated gene 7 is a novel tumor suppressor gene that induces apoptosis in lung cancer cells when delivered by adenoviral gene transfer as Ad-mda7. The mechanisms of action are not well defined but may involve release of cytochrome c from the mitochondria with subsequent caspase activation.


METHODS
The lung cancer cell lines A549 and H1299 were transduced with Ad-mda7, adenovirus containing the gene for p53 (Ad-p53), and control adenoviral luciferase vectors. Staurosporine was used as a positive control to induce cytochrome c release through mitochondrial permeability transition-dependent pores, whereas cyclosporine (INN: ciclosporin) was used to specifically inhibit these mitochondrial permeability transition-dependent pores. Apoptosis was evaluated with fluorescence-activated cell sorting analysis of subdiploid populations and mitochondrial membrane potential changes with tetramethylrhodamine ethylester perchlorate.


RESULTS
Melanoma differentiation-associated gene 7, transduced by Ad-mda7 into H1299 and A549 lung cancer cells, resulted in sharp increases in cytosolic cytochrome c levels followed by induction of apoptosis and cellular death. The release of cytochrome c from the mitochondria occurred without changes in the mitochondrial membrane potential. Unlike staurosporine treatment, transduction with Ad-p53 and Ad-mda7 caused releases of cytochrome c and apoptosis that were not blocked by cyclosporine, suggesting a mitochondrial permeability transition pore-independent pathway.


CONCLUSIONS
Ad-mda7 induces apoptosis in lung cancer cells through mitochondrial cytochrome c release in a process that is not dependent on mitochondrial membrane potential changes and occurs through mitochondrial permeability transition-independent pores. This unique mechanism of action may allow treatment of patients with lung cancer resistant to mitochondrial permeability transition-dependent cell death processes.
Pataer
Abujiang
A
Section of Thoracic Molecular Oncology, Department of Thoracic and Cardiovascular Surgery, The University of Texas M.D. Anderson Cancer Center, and Introgen Therapeutics Inc, Houston, TX 77030, USA.
Chada
Sunil
S
Hunt
Kelly K
KK
Roth
Jack A
JA
Swisher
Stephen G
SG
D000256:Adenoviridae; D017209:Apoptosis / Q000187:drug effects*; D020169:Caspases / Q000378:metabolism; D016572:Cyclosporine / Q000494:pharmacology; D003574:Cytochrome c Group / Q000378:metabolism*; D004789:Enzyme Activation; D018014:Gene Transfer Techniques; D016147:Genes, Tumor Suppressor / Q000502:physiology; D016158:Genes, p53 / Q000502:physiology; D006801:Humans; D007378:Interleukins / Q000494:pharmacology*; D008175:Lung Neoplasms / Q000473:pathology*; D008564:Membrane Potentials / Q000502:physiology; D008928:Mitochondria / Q000201:enzymology* / Q000502:physiology; D019311:Staurosporine / Q000494:pharmacology; D014161:Transduction, Genetic; D014407:Tumor Cells, Cultured; D000099180:Interleukin-24
D020169:Caspases; D016572:Cyclosporine; D003574:Cytochrome c Group; D007378:Interleukins; D019311:Staurosporine; D000099180:Interleukin-24