Fig. 4. CD40L induces drug resistance in MCL cell lines.

a, b Viability assays were performed after prestimulation of REC-1 and MAVER-1 cells with CD40L (100 ng/ml, 18 h) or H₂O as a control and additional treatment with sotrastaurin (a, 3 µM) or ibrutinib (b, 400 nM) for 48 h. Viability was determined with the MTT assay. c REC-1 cells were treated with various drugs (Akti-1/2, 1 µM; NVP-BEZ 235, 25 nM; AZD8330, 500 nM; ERK inhibitor II, 10 µM; 2-Bromoaldisine, 1 µM) or DMSO for 20 min before stimulation with CD40L (100 ng/ml, 18 h) or H₂O as a control and subsequent treatment with sotrastaurin (3 µM), ibrutinib (400 nM) or DMSO for additional 48 h. Viability was determined with the MTT assay (*p < 0.001; **p < 0.0001; ***p < 0.00001)