mTOR activity in cells and tissue derived from FL. (A) FL cell lines (Karpas-422 and RL) were treated or not with rapamycin at 10 nM for 24 hours, then mTOR activity was evaluated by Western blotting using antiphospho-p70S6K and phospho-4E-BP1 antibodies. p70S6K and 4E-BP1 were used as controls of protein expression. Results are representative of 3 independent experiments. (B) mTOR activity was evaluated in FL lymph node sections by immunohistochemistry using an antiphospho-p70S6K antibody as described in “Materials and methods.” This result is representative of the 6 positive samples analyzed. Objective magnification 20×/0.5 NA. (C) Clonogenicity of FL cells treated or not with rapamycin at various doses was measured after 7 days in methylcellulose medium as described in “Materials and methods.” CT corresponds to untreated FL cells, and results are the mean ± SD of 3 independent experiments. * P < .01.