siRNA down-regulation of PDCD4 expression and rescue of BB-induced growth inhibition. RPMI-8266 cells were treated with 100 nM PDCD4 siRNA for 6 h, and harvested 48 h after treatment. Total RNA and protein were isolated and analyzed for PDCD4 expression levels. (A) PDCD4 mRNA levels were determined by SYBR-Green real-time PCR. (B) PDCD4 protein levels were determined by western blot analysis. PDCD4 siRNA significantly down-regulated PDCD4 levels in RPMI-8266 cells. *p < 0.01, vs. control. RPMI-8266 and U226 cells were pre-treated as above and then plated in 96-well plates in medium containing 10% FCS for a further 72 h in the presence of BB (75 μM). Cell viability was assessed by triplicate MTT assays. The results indicate that PDCD4 siRNA can rescue BB-induced growth inhibition. (C) RPMI-8266 cells. (D) U226 cells. *p < 0.01 vs. control.