siRNA against p110 catalytic subunit of PI3-K and Akt1 prevents the supportive effect of BMSCs. CLL cells were transfected by Amaxa Nucleofector with the use of fluorescein isothiocyanate (FITC)–labeled siRNA against Akt1 and PI3-K p110 subunit (1 or 5nM) or with silencer negative control siRNA in electroporation buffer (control siRNA) or with pmaxGFP as a second control. Cells were incubated for 24 hours in cocultures. Transfection efficiency was estimated by FITC positivity (Aii-iii), and the effect on the viability is shown by PI/FITC positivity (a representative case, Aiv-vii). The percentages in the dotplots represent the transfection efficiency (Aii-iii), dead cells (Aiv), dead-transfected (top right; Avi-vii) and living transfected (bottom right; Av-vii). The efficiency of siRNA to knockdown Akt1, PI3-K p110, and its downstream target phospho-Akt is shown by Western blotting in (B-C). The mean ± SEM of the transfection efficiency and effect on cell viability obtained from 6 independent experiments is shown in panels D and E (control: untreated). A significant effect of the transfection on cell viability is shown in comparison to the controls (E). (**P < .01).