c-Abl-activated NF-κB in CLL cells causes autocrine IL-6 expression and STAT3 Y705 phosphorylation. (A) Enzyme-linked immunosorbent assay measurement of IL-6 secretion from CLL cells cultured for 6 hours in the absence of inhibitor (U), or in the presence of either 20μM imatinib or 2μM BAY11-7082. The results are representative of 4 different CLL patient samples and are presented as mean ± SEM. (B) Blocking the IL-6R inhibits IL-6 secretion and Y705-STAT3 phosphorylation. CLL cells from 3 different cases were incubated in the presence or absence of 0.5μM anti–IL-6R antibody or an IgG1 isotype control for 12 hours. Lysates of these cells were then probed by Western blot with the indicated antibodies.