Effect of RTX on MAPK pathway. (A) PKCζ activity was evaluated on Karpas-422 stably transfected with pcDNA3 (2E10) or DN-PKCζ (6E5) by immunokinase assay as described in “Immunokinase assays.” (B) (Left panel) The effect of PKCζ inhibition on ERK and MEK activities was evaluated on Karpas-422–transfected clones (2E10 or 6E5) by Western blot using anti–phospho-ERK (Thr202/Tyr204) and anti–P-MEK (Ser217/221) antibodies. MEK and ERK were used as control of protein expression. (Right panel) The effect of PKCζ inhibition on Raf-1 activity was evaluated on 2E10 and 6E5 clones by immunokinase assay as described in “Immunokinase assays.” Results are representative of 3 independent experiments. (C) RL cell lines were treated or not with RTX at 10 and 50 μg/mL for 24 hours, and then ERK activity was evaluated as described in panel B. ERK was used as control of protein expression. Results are representative of 3 independent experiments. (D) PKCζ activity and expression were evaluated on RL stably transfected with pcDNA3 (1G5) and CA-PKCζ (6F9, 7E5) by Western blot using anti–phospho-PKCζ antibody and anti-PKCζ antibodies, respectively. Actin was used as control of protein expression. (E) ERK activity was evaluated by immunokinase assay on RL stably transfected with pcDNA3 (1G5) and CA-PKCζ (6F9, 7E5) treated or not with RTX at 10 μg/mL.