Profiling flavonoid cytotoxicity in human breast cancer cell lines: determination of structure-function relationships
Abstract:
Flavonoids have been shown to be cytotoxic to cancer cells. However, the mechanism of cytotoxicity has not been clearly defined. It has previously been reported that HER2/ERBB2, the estrogen receptor, progesterone receptor, and p53 were required for flavonoid induced cytotoxicity in breast cancer cell lines. We have used a panel of breast cancer cell lines, known to contain as well as be deficient in these signaling pathways, to screen fourteen different flavonoids. Comparing the cytotoxicity for all flavonoids allows us to determine if a structure-functional relationship exists between cytotoxicity and flavonoid, and if a particular signaling pathway is required for cytotoxicity. We show that several flavonoids are cytotoxic to all cell lines including primary mammary epithelial cells tested. The cytotoxic flavonoids are also able to inhibit Mitochondrial Outer Membrane Permeability while at the same time stimulate ATP levels whereas the non-cytotoxic flavonoids are not able to do this. We also show that both cytotoxic and non-cytotoxic flavonoids can transverse the cell membrane to enter MDA-MB-231 cells at different levels. Finally, all flavonoids regardless of their cytotoxicity were able to induce some form of cell cycle arrest. We conclude that for flavonoids to be strongly cytotoxic, they must possess the 2,3-double bond in the C-ring and we believe the cytotoxicity occurs through mitochondrial poisoning in both cancer and normal cells.
Insights
Flavonoids can kill cancer cells by poisoning mitochondria, especially those with a specific C-ring structure. This mechanism affects both cancer and normal cells, impacting cell cycle and mitochondrial outer membrane permeability.
Area of Science:
- Biochemistry
- Molecular Biology
- Pharmacology
Background:
- Flavonoids exhibit cytotoxicity against cancer cells, but their precise mechanism remains unclear.
- Previous research suggested specific signaling pathways (HER2/ERBB2, estrogen receptor, progesterone receptor, p53) are crucial for this effect in breast cancer.
Purpose of the Study:
- To investigate the structure-function relationship of flavonoids regarding their cytotoxicity.
- To determine if specific signaling pathways are required for flavonoid-induced cytotoxicity.
- To elucidate the mechanism underlying flavonoid cytotoxicity.
Main Methods:
- Screened fourteen different flavonoids using a panel of breast cancer cell lines with varying signaling pathway expression.
- Assessed flavonoid cytotoxicity, mitochondrial outer membrane permeability, ATP levels, cellular uptake, and cell cycle arrest.
- Compared cytotoxic and non-cytotoxic flavonoids to identify structural requirements and mechanistic differences.
Main Results:
- Several flavonoids demonstrated cytotoxicity across all tested cell lines, including normal mammary epithelial cells.
- Cytotoxic flavonoids inhibited mitochondrial outer membrane permeability and stimulated ATP levels, unlike non-cytotoxic ones.
- All tested flavonoids, regardless of cytotoxicity, induced cell cycle arrest; cytotoxic ones required a 2,3-double bond in the C-ring.
Conclusions:
- Flavonoid cytotoxicity is strongly linked to the presence of a 2,3-double bond in the C-ring.
- The primary mechanism of cytotoxicity appears to be mitochondrial poisoning, affecting both cancerous and normal cells.
- Flavonoid uptake varies, and cell cycle arrest is a general effect, but strong cytotoxicity is dependent on specific structural features and mitochondrial impact.
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