Phytoestrogens induce apoptosis through a mitochondria/caspase pathway in human breast cancer cells

Abstract

Objective To explore the effect and pathway of phytoestrogens on the growth of breast cancer cell line MCF-7.

Methods MCF-7 cells (human estrogen receptor-positive and progesterone receptor-positive breast cancer cells) were cultured in serum-free medium for 24 h and then treated with genistein, resveratrol, and quercetin (10⁻¹⁰–10⁻⁴ mol/l). After further incubation for 24, 48, 72, and 92 h, the cells were harvested and extracted for 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. According to the above results, the proteins involving proliferative and apoptotic pathways were evaluated by Western blot analysis.

Results Genistein, resveratrol, and quercetin significantly inhibited cellular proliferation in a dose- and time-dependent manner. Significantly elevated caspase-3 activity was noted after treatment with genistein (10⁻⁹–10⁻⁷ mol/l), as well as with resveratrol and quercetin (10⁻⁹–10⁻⁵ mol/l). Significant reduction of PI3K and AKT protein and significant increase of Fas ligand, Fas-associated protein with death domain, cytochrome C, truncated Bid, caspase-9, and caspase-3 were all noted after genistein, resveratrol, and quercetin treatment. 17β-Estradiol induced completely opposite results. Estrogen receptor (ER) α expression was significantly increased with 17β-estradiol, whereas ERβ expression was significantly elevated in the cultures with genistein, resveratrol, and quercetin.

Conclusions These data demonstrate that genistein, resveratrol, and quercetin have antiproliferative effects on breast cancer cells. Their induction of apoptosis involves the activation of both the intrinsic and extrinsic apoptotic pathways, which may be related to the differential affinity to ERα and ERβ. Whether phytoestrogens have similar effects on normal breast cells remains to be examined.

Key words::

• GENISTEIN
• RESVERATROL
• QUERCETIN
• MITOCHONDRIA/CASPASE CASCADE
• MCF-7 BREAST CANCER CELLS

Conflict of interest The authors report no conflict of interest. The authors alone are responsible for the content and writing of this paper.

Source of funding This study was supported by the Medical Research Center (Chang Gung Memorial Hospital, Keelung) and a research grant from the Clinical Monitoring Research Program (CMRPG2B0441) of Chang Gung Memorial Hospital, Keelung.