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Long-term exposure to dietary sources of genistein induces estrogen-independence in the human breast cancer (MCF-7) xenograft model

Authors

  • Juan E. Andrade,

    1. Department of Food Science and Human Nutrition, University of Illinois at Urbana-Champaign, Urbana, IL, USA
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  • Young H. Ju,

    1. Department of Human Nutrition, Foods and Exercise, Virginia Polytechnic Institute and State University, Blacksburg, VA, USA
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    • Additional corresponding author: Dr. Young Ju, E-mail: yhju@vt.edu

  • Chandra Baker,

    1. Department of Human Nutrition, Foods and Exercise, Virginia Polytechnic Institute and State University, Blacksburg, VA, USA
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  • Daniel R. Doerge,

    1. National Center for Toxicological Research, U.S. Food and Drug Administration, Jefferson, AR, USA
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  • William G. Helferich

    Corresponding author
    1. Department of Food Science and Human Nutrition, University of Illinois at Urbana-Champaign, Urbana, IL, USA
    • Correspondence: Professor William G. Helferich, Department of Food Science and Human Nutrition, University of Illinois at Urbana-Champaign, 905 S. Goodwin, Urbana, IL 61801, USA

      E-mail: helferic@illinois.edu

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Abstract

Scope

The long-term effect of exposure to relevant dietary levels of genistein (GEN) on estrogen receptor-positive (ER+) human breast cancer (MCF-7) progression after GEN withdrawal in athymic mice xenograft model was studied.

Materials and methods

Feeding studies were conducted to determine the estrogenic effect of diets on MCF-7 tumor growth: (1) implantation (19 weeks) and withdrawal (6 weeks) of 17β-estradiol (E2); (2) dietary GEN 500 and 750 ppm during treatment/withdrawal for 23/10 and 15/9 weeks, respectively; and, (3) dietary soy protein isolate (SPI) containing GEN 180 ppm for 31/9 weeks of treatment/withdrawal. MCF-7 tumors grew fast in the presence of E2 implantation and abruptly regressed completely after E2 withdrawal. At different rates, dietary GEN alone (500 and 750 ppm) and GEN (180 ppm)-containing SPI stimulated MCF-7 tumor growth. After removal of the stimulus diet, tumors induced by 750 ppm GEN, but not 500 ppm GEN or SPI, regressed completely. The protein expression of epidermal growth factor receptor 2 (HER2) was higher in the GEN- and SPI-induced nonregressing (GINR) tumors compared to MCF-7 and E2 controls.

Conclusion

Long-term consumption of low GEN doses (≤500 ppm) promotes MCF-7 tumor growth and results in GINR tumors with more aggressive and advanced growth phenotypes.

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