Combined inhibition of estrogen-dependent human breast carcinoma by soy and tea bioactive components in mice

Abstract

Breast cancer is significantly less prevalent among Asian women, whose diets contain high intake of soy products and tea. The objective of our present study was to identify the combined effects of dietary soy phytochemicals and tea components on breast tumor progression in a clinically relevant in vivo model of MCF-7 androgen-dependent human breast tumor in female SCID mice. MCF-7 tumor growth, tumor cell proliferation and apoptosis, microvessel density, and expressions of tumor estrogen receptors were compared in mice treated with genistin-rich soy isoflavones (GSI), soy phytochemical concentrate (SPC), black tea (BT), green tea (GT), SPC/BT combination and SPC/GT combination. GSI and SPC led to dose-dependent inhibition of MCF-7 tumor growth via inhibition of cancer cell proliferation in vivo. GT showed more potent anti-breast tumor activity than BT. GT infusion at 1.5 g tealeaf/100 mL water produced significant (p < 0.05) reductions of 56% in final tumor weight. GT plus SPC at 0.1% of the diet further reduced final tumor weight by 72% (p < 0.005). Analysis of serum and tumor biomarkers showed that the combined effects of SPC and GT inhibited tumor angiogenesis, and reduced estrogen receptor (ER)-alpha and serum levels of insulin-like growth factor (IGF)-I. Our study suggests that dietary SPC plus GT may be used as a potential effective dietary regimen for inhibiting progression of estrogen-dependent breast cancer.

FIGURE 1

Dose-dependent effects of GSI and SPC on tumorigenicity and tumor volume in vivo. Mice were treated with experimental diets for 2 weeks, supplemented with 17β-estradiol, implanted orthotopically with MCF-7 cells, and continued on experimental diets throughout the study. Both GSI and SPC showed dose-dependent inhibition on tumor size (a), and final tumor weight (b). Values present mean ± SEM. *p < 0.05 (compared to control).

FIGURE 2

Combined effects between SPC and tea on tumorigenicity, tumor volume and final tumor weight in vivo. Mice were treated with experimental diets for 2 weeks, supplemented with 17β-estradiol, implanted orthotopically with MCF-7 cells, and continued on experimental diets throughout the study. Values present mean ± SEM. *p < 0.05; **p < 0.01 (compared to the control).