P3-17-07: EGCG, a Green Tea Antioxidant Suppresses Breast Tumor Angiogenesis and Growth Via Inhibiting the Activation of HIF-1a and NFκB, and VEGF Expression.

Abstract

Abstract Background Cancer cells are under greater oxidative stress than normal cells. Limited studies have showed that epigallocatechin-3-gallate (EGCG), a green tea antioxidant can afford protection against a variety of cancer types. The role of EGCG in breast cancer therapy is poorly understood. The present study tests the hypothesis that EGCG as an antioxidant can inhibit the activation of HIF-1α and NFκB, and VEGF expression, thereby suppressing tumor angiogenesis and breast cancer progression. Material and Methods: 16 eight-wk-old female mice (C57BL/6J) were inoculated with 10^6 E0771 (mouse breast cancer) cells in the left fourth mammary gland fat pad. 8 mice received EGCG at 50–100 mg/kg/d in drinking water for 4 weeks. 8 control mice received drinking water only. Tumor size was monitored using dial calipers. At the end of the experiment, blood samples, tumors, heart and limb muscles were collected for measuring VEGF expression using ELISA and capillary density (CD) using CD31 immunochemistry. Cultured E0771 cells were used for determining the direct effects of EGCG on proliferation (3H-thymidine incorporation), migration (Matrigel assay), VEGF expression (ELISA), the activation of HIF-1α and NFκB (motif binding assays, Active Motif). MCF-7 and MDA-MB-231 cells were also used for 3H-thymidine incorporation. Results: Oral EGCG treatment significantly reduced tumor weight over the control (0.37±0.15 vs. 1.16±0.30 g; P<0.01), tumor CD (109±20 vs. 156±12 capillary #/mm^2; P<0.01), tumor VEGF expression (45.72±1.4 vs. 59.03±3.8 pg/mg; P<0.01), respectively. EGCG treatment reduced plasma VEGF levels over the control mice (26.48±3.76 vs. 40.79±3.5 pg/ml; P<0.01). However, there were no differences in the body weight and heart weight between EGCG and the control groups. EGCG did not inhibit angiogenesis and VEGF expression in the heart and skeletal muscle of mice, compared to the control. EGCG at 50 mmol/L significantly inhibited the activation of HIF-1α (0.11±0.02 vs. 0.24±0.02; P<0.01) and NFκB (1.15±0.21 vs. 1.61±0.32; P<0.01) as well as VEGF expression (1752±49 vs. 2254±91 pg/mg; P<0.01) in cultured E0771 cells, compared to the control, respectively. EGCG caused a dose-related inhibition on the proliferation and migration in cultured E0771 cells. EGCG also caused a dose-related inhibition on the proliferation in cultured MCF-7 and MDA-MB-231 cells. Discussion: These findings support the hypothesis that EGCG, a green tea antioxidant, directly targets both tumor cells and tumor vasculature, thereby inhibiting tumor growth, proliferation, migration, and angiogenesis of breast cancer, which is mediated by the inhibition of HIF-1α and NFκB activation as well as VEGF expression. Interestingly, oral EGCG treatment has no effects on the body weight, heart weight, angiogenesis and VEGF expression in the heart and skeletal muscle of mice. This work will have important implications for translating EGCG therapy to human breast cancer treatment and prevention. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P3-17-07.