Dietary γ-tocopherol-rich mixture inhibits estrogen-induced mammary tumorigenesis by modulating estrogen metabolism, antioxidant response, and PPARγ

Soumyasri Das Gupta, Sudathip Sae-Tan, Joseph Wahler, Jae Young So, Min Ji Bak, Larry C. Cheng, Mao Jung Lee, Yong Lin, Weichung Joe Shih, James D. Shull, Stephen Safe, Chung S. Yang, Nanjoo Suh

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24 Scopus citations

Abstract

This study evaluated the anticancer activity and mechanism of action of a g-tocopherol-rich tocopherol mixture, γ-TmT, in two different animal models of estrogen-induced breast cancer. The chemopreventive effect of γ-TmT at early (6 weeks), intermediate (18 weeks), and late (31 weeks) stages ofmammary tumorigenesis was determined using the August-Copenhagen Irish rat model. Female rats receiving 17β-estradiol (E2) implants were administered with different doses (0%, 0.05%, 0.1%, 0.3%, and 0.5%) of γ-TmT diet. Treatment with 0.3% and 0.5% γ-TmT decreased tumor volume and multiplicity. At 31 weeks, serum concentrations of E2 were significantly decreased by γ-TmT. γ-TmT preferentially induced expression of the E2-metabolizing enzyme CYP1A1, over CYP1B1 in the rat mammary tissues. Nrf2-dependent antioxidant response was stimulated by γ-TmT, as evident from enhanced expression of its downstreamtargets, NQO1, GCLM, and HMOX1. Serum concentrations of the oxidative stress marker, 8-isoprostane, were also decreased in the γ-TmT-treated groups. Treatment with γ-TmT increased expression of PPARγ and its downstream genes, PTENand p27, whereas the cell proliferationmarker, PCNA, was significantly reduced in γ-TmT-treated mammary tumors. In an orthotopic model in which human MCF-7 breast cancer cells were injected into themammary fat pad ofimmunodeficient mice, γ-TmT inhibited E2-dependent tumor growth at all the doses tested. In conclusion, γ-TmT reduced mammary tumor development, in part through decreased E2 availability and reduced oxidative stress in mammary tissues; γ-TmT could thus be an effective agent for the prevention and treatment of E2-induced breast cancer.

Original languageEnglish (US)
Pages (from-to)807-816
Number of pages10
JournalCancer Prevention Research
Volume8
Issue number9
DOIs
StatePublished - Sep 1 2015

All Science Journal Classification (ASJC) codes

  • Oncology
  • Cancer Research

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