Effect of BB on levels of miRNA-21, IL6, and PDCD4 and the effect of exogenous IL6 on BB-induced miRNA-21 expression. RPMI-8266 and U226 cells were treated with 75 μM and 120 μM BB, respectively, in the absence or presence of IL6 (0.5 ng/ml) and harvested 48 h after treatment. Total RNA and protein were isolated and analyzed for levels of miRNA-21 and PDCD4. (A) miR-21 and U6 snRNA levels were determined by quantitative real-time PCR in the absence or presence of IL6. (B) The IL6 protein levels in supernatants were determined using an ELISA kit. (C) Relative PDCD4 mRNA levels were measured with SYBR-Green real-time PCR. (D) PDCD4 protein levels were assessed by western blot analysis. *p < 0.01 vs. control. The data show that BB significantly down-regulated miR-21 and IL6 levels in RPMI-8266 and U226 cells and up-regulated PDCD4 mRNA and protein levels in 8266 cells. Notably, exogenous IL6 could attenuate the reduction in miRNA-21 expression induced by BB.