Green tea’s effect on anti-estrogen treatment
2006
Proc Amer Assoc Cancer Res, Volume 47, 2006
2251
We observed that green tea increases the inhibitory effect of tamoxifen on the proliferation of multiple ER (estrogen receptor-α)-positive human breast cancer cells in vitro. The ID50 (inhibitory dose 50) for tamoxifen alone were as follows: 10.2 μM for MCF-7, 7.2 μM for ZR-75, and 8.4 μM for T47-D. We then demonstrated that the addition of 5 μg/ml of green tea extract decreased the ID50 of tamoxifen to 200 nM for MCF-7, 36 nM for ZR-75 and 30 nM for T47-D. It thus appears that green tea can add to tamoxifen’s effectiveness on ER-positive breast cancer cells. Further experiments showed that green tea did not affect substrate binding to the estrogen receptor. However, green tea decreased the level of estrogen receptors, blocked ER-dependent transcription, as well as estradiol-induced phosphorylation and nuclear localization of mitogen activated protein kinase (MAPK). The addition of green tea to tamoxifen potentiated these ER-dependent activities. These results suggest that consumption of green tea during tamoxifen treatment may be beneficial for breast cancer patients.
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