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Apoptotic mechanisms in T47D and MCF-7 human breast cancer cells
L M Mooney1, K A Al-Sakkaf, B L Brown
1Institute for Cancer Studies, Division of Genomic Medicine, Medical School, University of Sheffield, Sheffield S10 2RX, UK.
Abstract:
To investigate the mechanisms underlying apoptosis in breast cancer cells, staurosporine was used as an apoptotic stimulus in the human breast cancer cell lines MCF-7 and T47D. Staurosporine induced dose and time dependent increases in DNA fragmentation which was abrogated by z-VAD-fmk. MCF-7 cells did not express caspase-3, suggesting that DNA fragmentation occurred in the absence of caspase-3 and that other caspases may be involved. Staurosporine induced DEVDase activity in T47D cells suggesting the involvement of caspase-3 and/or caspase-7, yet there was no DEVDase activity in MCF-7 cells, probably ruling out the involvement caspase-7. However, staurosporine induced the cleavage of pro-caspase-6 in MCF-7 cells, but not in T47D cells. Caspase dependent PARP cleavage was detected in MCF-7 cells at 3 h, whereas only partial PARP cleavage was detected in T47D cells and then only after 24 h. Moreover, staurosporine led to cytochrome c release at 2 h in MCF-7 cells and 6 h in T47D cells. In addition, a time dependent and caspase-independent reduction of the mitochondrial transmembrane potential was observed; which appeared to occur after the release of cytochrome c. Translocation of Bax from the cytosol to mitochondria was observed in both cell types, and this preceded cytochrome c release in both T47D and MCF-7 cells. Apoptotic events in both cell types differ temporally, involving activation of different caspases and mitochondrial changes.
Insights
This study reveals distinct apoptosis pathways in breast cancer cells. MCF-7 and T47D cells exhibit differential caspase activation and mitochondrial changes during staurosporine-induced cell death.
Area of Science:
- Molecular Biology
- Cell Biology
- Cancer Research
Background:
- Apoptosis is crucial for cancer treatment.
- Understanding apoptosis mechanisms in breast cancer is vital.
Purpose of the Study:
- Investigate apoptosis mechanisms in MCF-7 and T47D breast cancer cells.
- Characterize the role of caspases and mitochondrial pathways in staurosporine-induced apoptosis.
Main Methods:
- Utilized staurosporine as an apoptotic stimulus.
- Analyzed DNA fragmentation, caspase activity (DEVDase), pro-caspase cleavage, PARP cleavage, cytochrome c release, mitochondrial membrane potential, and Bax translocation.
- Employed z-VAD-fmk to assess caspase dependency.
Main Results:
- Staurosporine induced dose- and time-dependent DNA fragmentation, abrogated by z-VAD-fmk.
- MCF-7 cells showed caspase-3-independent DNA fragmentation and pro-caspase-6 cleavage, unlike T47D cells.
- Differential kinetics of PARP cleavage, cytochrome c release, and Bax translocation were observed between cell lines.
- Caspase-independent reduction in mitochondrial transmembrane potential occurred post-cytochrome c release.
Conclusions:
- Apoptotic events in MCF-7 and T47D cells differ temporally.
- Distinct caspase activation profiles and mitochondrial changes characterize apoptosis in these breast cancer cell lines.
- Bax translocation to mitochondria precedes cytochrome c release in both cell types.