Targeting JNK and EGR-1 induces MCL apoptosis and decreases BCR-induced cell survival. (A) HBL-2 and Granta-519 cells were treated with SP600125 for 48 h and apoptosis was measured by flow cytometry. Percentage of apoptotic cells corresponded to% of annexin V-positive, including PI-negative and PI-positive cells. Mean ± SD of 2 independent experiments is represented. (B) Patients’ cells (UPN1, 2, 8 and 11) were stimulated with immobilized anti-IgM for 24 h with or without SP600125 (10 μM) and the percentage of apoptotic cells was determined by flow cytometry after gating on CD19+ cells (left panel). All measurements were done in duplicate and the mean is provided. Results are also shown as median ± quartile (box) ± SE (bars) (n=4) (right panel). Differences between groups were determined using the paired Student t test. (C) Jeko-1 cells were transfected either with control siRNA (Ctrl1) or EGR-1 siRNA and EGR1 protein level was determined by western-blot after 72 h of culture (left panel). Primary MCL cells (UPN9) were transfected either with controls siRNA (Ctrl1, Ctrl2) or EGR-1 siRNA and subsequently stimulated with anti-IgM for 24 h or left unstimulated (right panel). Percentage of apoptotic cells was normalized to unstimulated cells and calculated as follows: [(% apoptosis BCR stimulated cells -% apoptosis BCR-unstimulated cells) / (% apoptosis BCR-unstimulated cells)] x100. All measurements were done in duplicate and the mean value is provided.