Implication of Syk in mTOR activity in FL cells. (A) Karpas-422 and RL cells were treated or not with herbimycin A (0.5 μg/mL), SU6656 (1 μM), or piceatannol (50 μM) for 2 hours, then p70S6K phosphorylation was evaluated by Western blotting. p70S6K was used as control of protein expression. CT corresponds to untreated FL cells and results are representative of 3 independent experiments. (B) FL cells were treated or not with piceatannol at various doses for 2 hours, and mTOR activity was then evaluated by immunoblotting using antiphospho-p70S6K antibody. p70S6K was used as control of protein expression. Results are representative of 3 independent experiments. (C) mTOR activity was evaluated on scramble (RL-12a) and Syk siRNA (RL-6G2, RL-6F2, and RL-6G8) stable transfected clones by Western blotting using antiphospho-p70S6K (Thr389) antibody. p70S6K was used as control of protein expression. Syk expression visualized by RT-PCR (left) and by Western blotting (right) was used as control for Syk depletion. (D) Clonogenicity of FL cell treated or not with piceatannol at various doses was observed after 7 days in methylcellulose medium as described in “Materials and methods.” Results are the mean ± SD of 3 independent experiments. *P < .01.