CXCL12 and B-cell chronic lymphocytic leukemia: To determine if CXCL12 can promote IL-10 production in CLL cells by activating the STAT3 pathway, we stimulated CLL cells with 250 ng/ml of CXCL12 and measured p-S727-STAT3 as described in the Section “Materials and Methods.” CXCL12 induced a significant increase in the levels of p-S727-STAT3 (Figure 1A), but not Y705-STAT3 (Figure S1 in Supplementary Material) in CLL cells.