Inhibition of MEK/ERK-pathway did not affect the protective effect of TPA.

(A) B-CLL cells from 4 representative patients were incubated with or without 1 μM U0126 for 1 hour before the addition of 10 nM TPA for 20 minutes. ERK phosphorylation was analyzed by Western blot. (B) B-CLL cells were incubated for 1 hour in the presence (▪) or absence (■) of 1 μM U0126. After that time, drugs were added to the culture, and incubation continued for another 48 hours. At the end of the culture, cell viability was analyzed by flow cytometry. Results are represented as the mean ± SD of 7 patients analyzed.