CXCL12 induces increased and prolonged ERK activation in ZAP-70⁺ CLL cells. CLL cells were exposed to 30nM CXCL12 for 0-60 minutes at which point the cells were harvested, lysed, and analyzed for p-ERK. (A) Immunoblots were probed with anti–p-ERK and total ERK (ERK) antibody. Representative data of 4 ZAP-70⁺ and 4 ZAP-70⁻ CLL samples are shown. Vertical lines have been inserted to indicate repositioned gel lanes to align ZAP-70⁻ and ZAP-70⁺ samples. (B) To obtain quantitative results, cell lysates were analyzed by a p-ERK–specific enzyme-linked immunoabsorbent assay. (Left) Depicted is the absorbance measured at 450 nm. Data are shown as mean ± SD of ZAP-70⁻ CLL samples (n = 9) and ZAP-70⁺ CLL samples (n = 7). * indicates a statistically significant difference; P < .05 paired Student t test. Two-way analysis of variance was used for the comparison ZAP-70⁺ vs ZAP-70⁻ CLL samples at 10 minutes. (Right) The integral under the curve was measured as described in “Methods” and is depicted for all ZAP-70⁺ and ZAP-70⁻ CLL cases shown on the left. Data shown are median ± SD; * indicates a statistically significant difference; P < .05 unpaired Student t test.