STAT3 and B-cell chronic lymphocytic leukemia: Treatment of CLL cells with the optimal concentration of lenalidomide (10 μM) as measured by a dose titration assay (Figure S8 in Supplementary Material) prevented CXCL12-induced increase in p-S727-STAT3 above baseline as measured by phosflow (Figure 6A; Figure S8 in Supplementary Material) and Western blotting (Figure S9 in Supplementary Material), and resulted in a significant reduction in the IL-10 response by B-CLL cells as well as the baseline constitutive phosphorylation of S727-STAT3 (Figures 6A,B).