Gossypol and radiation activate the SAPK/JNK pathway. A: AT-101 is a stronger activator of SAPK/JNK than racemic (±)-gossypol. U937 cells were treated with equimolar concentrations of AT-101 (5 μM) and SAPK/JNK activation was analyzed at t = 2 h. (Abbreviations: C = control; AT = AT-101; ± =(±)-gossypol). B: Dose-dependent SAPK/JNK activation in U937 (upper panel) and Jurkat T cells (lower panel). Cells were treated with indicated concentrations of AT-101 and SAPK/JNK activation was analyzed at t = 2 h. C: Kinetics of 5 μM AT-101-induced SAPK/JNK in human leukemic (U937 and Jurkat T) and carcinoma cells (VU-SCC-OE and UM-SCC-11B). D: Radiation (8 Gy) induces a time-dependent SAPK/JNK activation in Jurkat T cells (upper panel). In U937 cells, the combination of AT-101 (AT; 5 μM) and radiation (RT; 10 Gy) induces a stronger activation of SAPK/JNK at t = 2 h than single modality treatment (lower panel).