Rac1 activity contributes to p53-deficient lymphoma cell hyperproliferation. (A) Cell lysates were subjected to GST-PAK pull-down assay and processed for Western immunoblot to determine Rac1 activity in BL41 (left panel) and J3D (right panel) cells after 4-day treatment with NSC23766 or transduction with a Rac1 N17 mutation. Anti-HA or anti-Rac antibodies were used and β-actin served as a loading control. Immunoblot bands from at least 3 independent experiments were quantified by densitometry and displayed. *P < .05, significant with respect to untreated control. (B) BL41 (left panel) or J3D (right panel) cells were treated with NSC23766 or transduced with Rac1N17 as in panel A and cell number was monitored by trypan blue exclusion. Error bars represent SD.