Role of STAT3 activation in IL-6–mediated protection of MCL cells. Western blot showing STAT3 phosphorylation (A) in Mino and Granta 519 cells examined at 15, 30, 60, and 120 minutes in cultures without or with addition of IL-6 (0.5 ng/mL) and IL-6–neutralizing antibodies (a-IL6; 50 μg/mL), (B) in Mino and Granta 519 cells that were pretreated with 25μM of STAT3 inhibitor V or JAK2 inhibitor, respectively, for 2 hours, before culturing with IL-6 (0.5 ng/mL) for 30 minutes, or (C) in Mino cells that were pretreated with 25μM of PI3K, mTOR, or MEK inhibitors, respectively, for 2 hours before culturing with IL-6 (0.5 ng/mL) for 30 minutes. Also shown are percentages of apoptotic (D) Mino and Granta 519 cells in cultures without or with addition of BTZ (10nM), IL-6 (0.5 ng/mL), or STAT3 inhibitor V (25μM); or (E) Mino cells in cultures without or with addition of IL-6 (0.5 ng/mL), BTZ (10nM), or inhibitors (25μM) to Jak2, STAT3, PI3K, MEK, or mTOR, respectively, for 48 hours. The P value in the graph shows comparison as indicated