Inhibition of the PI3-K/Akt but not mTOR pathway induces apoptosis in MCL. (A) To assess whether the PI3-K/Akt and/or mTOR signalings regulate MCL cell survival, we investigated the effects of wortmannin, SH-5, and rapamycin in Granta 519 and SP-53 cells. Cells were treated with 0.1 μM wortmannin (Wort), 20 μM SH-5, or 0.1 μM rapamycin (R) for 24 hours, and apoptosis was quantified by TUNEL assay. Percentages of apoptotic cells are indicated. Comparable results were obtained in SP-53 and Jeko-1 cells, and a representative experiment with SP-53 is shown. (B) Effects of LY294002 and rapamycin on cell survival of 5 patients with primary MCL. B cell–enriched cultures were treated with LY294002 (10 μM) or rapamycin (0.1 μM) for 72 hours, and apoptosis was quantified by CFDA-SE/PI labeling. Effects of LY294002 and rapamycin were also investigated in the same primary MCL cultures stimulated by rhsCD40-L alone or in combination with IL-4. (C,D) Analysis of caspase activation by immunoblotting in SP-53 cells. LY294002-, wortmannin-, and SH-5–induced apoptosis in SP-53 cells were associated with activation of caspase-9, -8, and -10 and cleavage of caspase-3 and PARP. Tubulin shows equal loading of protein for each lane.