PDGF-BB stimulation of normal fibroblasts resulted in increased expression of miR-21 whereas inhibition of PDGF signaling in glioma cells caused a decrease of miR-21. Inhibition of PDGF signaling causes a decrease of miR-21 in a glioma cell culture and glioma initiating cells cultured as spheres, respectively. (A) Up-regulation of miR-21 expression could be seen, using Northern blot, in 1064SK cells after treatment with PDGF-BB. U6 was used as a loading control. (B) miR-21 levels, normalized to miR-16, after inhibition of PDGF signaling in p19Arf−/− cells with a panel of inhibitors. Bars represent mean values from two independent experiments. SEMs are indicated in the figure and * indicates statistical significance (p < 0.05) from Student´s t-test. (C) The expression level of miR-21 after si-PDGF-BB was analyzed by qPCR in TC1 cells. miR-21 values were normalized to miR-16 and represent mean values from five independent experiments. SEMs are indicated in the figure and * indicates statistical significance (p < 0.05) from Student´s t-test.