Related Experiment Videos
Green tea polyphenol targets the mitochondria in tumor cells inducing caspase 3-dependent apoptosis
Stephen Hsu1, Jill Lewis, Baldev Singh
1Department of Oral Biology and Maxillofacial Pathology, School of Dentistry, AD1443. Medical College of Georgia, Augusta, GA 30912-1126, USA. shsu@mail.mcg.edu
Abstract:
Induction of apoptosis by green tea polyphenols has been observed in various tumor cell systems, but whether green tea polyphenol-induced apoptosis requires caspase 3 for execution has not been confirmed. We previously reported that green tea polyphenol-induced apoptosis involved Apaf-1 accumulation and caspase 3 activation in the cytosol. In the current study, tumor cells either with deleted caspase 3 gene or expressing wild-type caspase 3 were treated with increasing concentrations of green tea polyphenol(s), followed by morphological analysis and caspase 3 activity assay. The caspase 3 null parental cell line was further examined in comparison with a well-characterized, caspase 3 wild type oral carcinoma cell line by MTT assay and BrdU incorporation assay. The results demonstrated that, while the mitochondrial function gradually declined to insignificant levels, caspase 3 null cells did not undergo apoptosis, which suggested that green tea polyphenol-induced apoptosis is a mitochondria-targeted, caspase 3-executed mechanism.
Insights
Green tea polyphenols induce apoptosis in tumor cells. This process requires caspase 3 execution and targets mitochondria, as shown by studies on caspase 3 null cells.
Area of Science:
- Biochemistry
- Molecular Biology
- Cancer Research
Background:
- Green tea polyphenols are known to induce apoptosis in various cancer cell systems.
- The precise role of caspase 3 in executing green tea polyphenol-induced apoptosis remained unconfirmed.
- Previous research indicated Apaf-1 accumulation and caspase 3 activation in the cytosol.
Purpose of the Study:
- To confirm whether caspase 3 is essential for green tea polyphenol-induced apoptosis.
- To investigate the mechanism of green tea polyphenol-induced apoptosis in tumor cells.
- To elucidate the role of mitochondria in this apoptotic pathway.
Main Methods:
- Treatment of tumor cells (caspase 3 null vs. wild-type) with green tea polyphenols.
- Morphological analysis and caspase 3 activity assays.
- MTT and BrdU incorporation assays to assess cell viability and proliferation.
Main Results:
- Caspase 3 null cells did not undergo apoptosis upon treatment with green tea polyphenols.
- Mitochondrial function declined significantly in treated cells.
- Green tea polyphenols demonstrated a mitochondria-targeted mechanism.
Conclusions:
- Green tea polyphenol-induced apoptosis is a caspase 3-executed mechanism.
- The apoptotic pathway initiated by green tea polyphenols targets mitochondria.
- Caspase 3 is a critical executioner in green tea polyphenol-induced tumor cell apoptosis.