EGCG Suppresses Melanoma Tumor Angiogenesis and Growth without Affecting Angiogenesis and VEGF Expression in the Heart and Skeletal Muscles in Mice

Abstract

Melanoma is a highly malignant cancer with a potent capacity to metastasize distantly and has a higher mortality. There is no effective therapy for high risk melanoma patients to prevent relapse or distant metastasis. Therefore effective chemoprevention strategies are needed. The present study mainly evaluates the effects of EGCG on melanoma angiogenesis, growth, and capillary density (CD) in the heart and skeletal muscles of mice. 5 x 10^5 B16F10 cells were inoculated into the right proximal dorsal of the back in the eight week old male mice (n=12). Then, 6 mice received EGCG at 50-100 mg/kg/d in drinking water for 4 weeks and 6 control mice received drinking water only. Tumor size was monitored using dial calipers. At the end of the experiment, blood samples, tumors, hearts, and limb muscles were collected and measured for VEGF expression using ELISA and capillary density (CD) using CD31 immunohistochemistry. Compared to the control, EGCG treatment significantly reduced tumor weight (2.9±0.5 vs. 5.9±1.1 g; P<0.01; n=6), melanoma CD (117±9 vs. 167±23; P<0.01), and melanoma VEGF expression (32±1.5 vs. 42±2 pg/mg; P < 0.01), respectively. Also EGCG had no effects on body weight, heart weight, angiogenesis or VEGF expression in the heart and skeletal muscle of mice. EGCG (20-50 µg/ml) significantly inhibited the proliferation, migration, VEGF expression, and the activation of HIF-1α and NFαB in cultured B16F10 cells, respectively. These findings support the hypothesis that EGCG, a major green tea polyphenol, directly targets tumor cells and tumor vasculature, thereby inhibiting tumor growth, proliferation, migration, and angiogenesis of melanoma, and that the down-regulation of VEGF expression by EGCG is associated with the inhibition of HIF-1α and NFkB activation. EGCG has great potential as a chemopreventive agent because it has no effect on angiogenesis in normal tissue and has low toxicity.