Figure 6

Downregulation of VEGF in BMSCs by siRNA. (A) The amount of secreted VEGF protein was reduced as a result of VEGF siRNA treatment. At 72 h, VEGF concentration in supernatant of control-treated stromal cells was 5,240.3 ± 478.3 pg/mL, whereas siRNA-treated stromal cells only secreted 1,742.8 ± 186.1 pg/mL VEGF (P = 0.013, paired two-tailed t test). (B) Stromal cells with reduced VEGF content provided significantly reduced survival support for CLL cells. The survival advantage of VEGF-reduced stromal cells was 9.3% ± 2.3% in comparison with a survival support of 17.6% ± 2.5% of control-treated stromal cells after 24 h (P = 0.028, paired two-tailed t test). At 48 h, the survival support of VEGF-reduced stromal cells was 12.0% ± 2.1%, whereas control-treated stromal cells led to an improved survival of 23.4% ± 2.7% compared with monoculture (P = 0.005, paired two-tailed t test). Addition of rhVEGF partly reestablished the survival support of VEGF-reduced BMSCs (survival advantage of 12.7% ± 2.5% and 18.4% ± 2.7% compared with control (P = 0.071 and P = 0.061, paired two-tailed t test) at 24 and 48 h, respectively). UTC, untreated control. *P < 0.05; **P < 0.01; n.s., not significant.