Phytoestrogens and breast cancer: a complex story.
Level 5 - mechanism / opinion, no new human data
Narrative review summarizing in vitro and animal research
PubMed 18815740 · doi:10.1007/s10787-008-8020-0
What was done
The authors reviewed preclinical in vitro and in vivo animal studies evaluating the effect of the soy isoflavone genistein, its glycoside genistin, and different soy protein matrices on estrogen-dependent breast cancer growth. They also evaluated experimental data from ovariectomized athymic mice implanted with MCF-7 human breast tumors receiving estradiol, tamoxifen, and dietary genistein.
What was found
No numerical values or statistical metrics are reported in the abstract. Qualitatively, genistein and genistin stimulated estrogen-dependent mammary tumor growth in vitro, in chemically induced rodent models, and in mouse xenografts, with tumor regression observed upon withdrawal. Soy protein isolate stimulated tumor growth in a dose-dependent manner based on isoflavone content, whereas soy flour did not stimulate growth but prevented regression. Expression of estrogen-target genes (pS2, progesterone receptor, cyclin D1) increased with dietary genistein. In mouse xenograft experiments, dietary genistein negated the inhibitory effect of tamoxifen on estradiol-stimulated tumor growth.
Why it matters
This review highlights that isolated soy isoflavones can act as estrogen agonists in preclinical breast cancer models and potentially counteract anti-estrogen therapies like tamoxifen depending on the food matrix.
Limits
The abstract describes only cell culture and animal models, providing no direct human clinical data. No sample sizes, animal numbers, effect sizes, or statistical confidence intervals are provided.
Cited by
- supports In animal models, isolated and hydrolyzed soy protein produced significantly different effects, particularly regarding cancer outcomes, compared to whole soy foods.