Related Experiment Video
Updated: Aug 19, 2026
Using Mouse Mammary Tumor Cells to Teach Core Biology Concepts: A Simple Lab Module
Published on: June 18, 2015
Low-dose dietary phytoestrogen abrogates tamoxifen-associated mammary tumor prevention
Bolin Liu1, Susan Edgerton, Xiaohe Yang
1Department of Pathology, University of Oklahoma Health Sciences Center, 940 Stanton L. Young Boulevard, Oklahoma City, OK 73104, USA.
Abstract:
Wild-type erbB-2/neu transgenic mice were used to study the interactions between tamoxifen and dietary phytoestrogens (or isoflavones) by dose and form in vivo. Mice were randomized to one of four dietary formulas and implanted with an 8-week continuous-release tamoxifen or placebo pellet at 8 weeks of age. In placebo-treated mice, soy meal diet (but not diets supplemented with low-dose or high-dose isoflavones or a casein diet) resulted in prolongation of tumor latency. In tamoxifen-treated mice fed the soy meal, casein, or high-dose isoflavone enriched diets, the majority (>80%) showed no tumor formation by 60 weeks of age. Of the mice that developed tumors, latency was significantly prolonged. In tamoxifen-treated mice fed the low-dose isoflavone enriched diet, a much higher rate of mammary tumor development (>50%; P < 0.002) and a shorter tumor latency were observed. In vitro studies of human and mouse mammary tumor cell lines confirm that low doses of genistein, co-administered with tamoxifen, promote cell proliferation. This is in contrast to tamoxifen alone or tamoxifen with higher doses of genistein that are growth inhibitory. In summary, low-dose dietary isoflavones abrogated tamoxifen-associated mammary tumor prevention in vivo. These interactions are supported by in vitro data from human and mouse mammary tumor cell lines. These dose-associated interactions likely have relevance to the human use of tamoxifen for prevention or treatment of breast cancer.
Insights
Low-dose dietary isoflavones may reduce tamoxifen
Area of Science:
- Oncology
- Endocrinology
- Nutritional Science
Background:
- Tamoxifen is a crucial medication for breast cancer prevention and treatment.
- Dietary phytoestrogens, like isoflavones, are being investigated for their potential impact on cancer.
- Interactions between tamoxifen and dietary components require thorough investigation.
Purpose of the Study:
- To investigate the in vivo interactions between tamoxifen and dietary phytoestrogens (isoflavones) at varying doses and forms.
- To determine the effect of dietary isoflavones on tamoxifen's efficacy in preventing mammary tumors in a transgenic mouse model.
- To explore the in vitro effects of genistein and tamoxifen on mammary tumor cell lines.
Main Methods:
- Utilized wild-type erbB-2/neu transgenic mice.
- Administered tamoxifen or placebo pellets and randomized mice to four dietary formulas (soy meal, low-dose isoflavones, high-dose isoflavones, casein).
- Conducted in vitro studies using human and mouse mammary tumor cell lines.
Main Results:
- In placebo-treated mice, soy meal diet prolonged tumor latency.
- Tamoxifen with soy meal, casein, or high-dose isoflavones prevented tumors in most mice (>80%).
- Low-dose isoflavones abrogated tamoxifen's tumor prevention, increasing tumor development (>50%) and shortening latency.
- In vitro, low-dose genistein with tamoxifen promoted cell proliferation, unlike tamoxifen alone or with higher genistein doses.
Conclusions:
- Low-dose dietary isoflavones can interfere with tamoxifen's ability to prevent mammary tumors in vivo.
- These dose-dependent interactions are supported by in vitro cell line data.
- Findings suggest potential implications for breast cancer patients using tamoxifen and consuming soy products.
