Inhibition of tumor angiogenesis by TTF1 from extract of herbal medicine

Abstract

To study the inhibition of tumor angiogenesis by 5,2,4´-trihydroxy-6,7,5´-trimethoxyflavone (TTF1) isolated from an extract of herbal medicine Sorbaria sorbifolia. Angiogenic activity was assayed using the chick embryo chorioallantoic membrane (CAM) method. Microvessel density (MVD) was determined by staining tissue sections immunohistochemically for CD34 using the Weidner capillary counting method. The mRNA and protein levels of vascular endothelial growth factor (VEGF), vascular endothelialgrowth factor receptor 2 (VEGFR2, Flk-1/KDR), basic fibroblast growth factor (bFGF), cyclo-oxygenase (COX)-2 and hypoxia-inducible factor (HIF)-1α were detected by quantitative real-time polymerase chain reaction and Western blotting analysis. The TTF1 inhibition rates for CAM were 30.8%, 38.2% and 47.5% with treatment concentrations of 25, 50 and 100 μg/embryo × 5 d, respectively. The inhibitory rates for tumor size were 43.8%, 49.4% and 59.6% at TTF1 treatment concentrations of 5, 10, and 20 μmol/kg, respectively. The average MVD was 14.2, 11.2 and 8.5 at treatment concentrations of 5 μmol/kg, 10 μmol/kg and 20 μmol/kg TTF1, respectively. The mRNA and protein levels of VEGF, KDR, bFGF, COX-2 and HIF-1α in mice treated with TTF1 were significantly decreased. TTF1 can inhibit tumor angiogenesis, and the mechanism may be associated with the down-regulation of VEGF, KDR, bFGF, HIF-1α and COX-2.