RNA interference of VEGF and Ang-2.MDA-MB-231 cells were transfected with the pooled siRNAs with lipofectamine 2000 (Invitrogen). Thirty-six hours after the transfection, total RNA from cultured cells was extracted by use of Trizol (Invitrogen). Real-time quantitative PCR was conducted to assess the level of the target mRNA expression using SYBR green dye, with relative changes calculated by the ΔΔCt method. While the suppression of either of VEGF or Ang-2 caused significant reduction of the other when compared with the siRNA controls, inhibition of VEGF lead to a dramatic decrease in the level of Ang-2. The results indicate that Ang-2 is more likely regulated by VEGF.