Effect of VEGF stimulation on CXCR7 expression in HUVECs and SMMC-7721 cells. HUVECs and SMMC-7721 cells were stimulated for 8, 16 and 24 h in the presence or absence of VEGF (50 ng/ml) respectively. A. total RNA was analyzed by RT-PCR for CXCR7 mRNA expression. GAPDH was used as an internal control. B. HUVECs and SMMC-7721 cells were treated as in A and then subjected to Western blot analysis to examine CXCR7 protein expression. β-actin was used as an internal control. Results are representative of three separate experiments. C and D. SMMC-7721 cells pretreated or not with VEGF (50 ng/ml) were used for Matrigel invasion assay, adding CXCL12 (100 ng/ml) to the bottom chamber. The number of invasive cells in five fields/well is reported. Data are expressed as means ± SD from three independent experiments.*p < 0.05 (as compared with untreated cells).