Effect of mTOR signaling on caspase 3 cleavage, apoptosis, migration and proliferation upon PDGF-BB stimulation. Rictor-null or control MEFs were serum-starved for 24 h and then treated with PDGF-BB for 24 h; activation of caspase 3 was measured thereafter by immunoblotting against cleaved caspase 3 (A). Internucleosomal DNA fragmentation was quantitatively determined by assaying for cytoplasmic mononucleosome- and oligonucleosome-associated histone accumulated in apoptotic cell (B), data represent three separate experiments each performed in duplicate ± SEM. Cell migration experiments were carried out in a 96-well ChemoTX cell migration microplate. The wells of the microplate were filled with medium containing combinations of PDGF-BB with Rictor-null or control MEFs (C), as well as NIH3T3 cells with or without longterm treatment with rapamycin (E), as indicated. The amounts of migrated cells are given as index units; data represent three separate experiments, each performed in quadruplicates ± SEM. In separate experiments, NIH3T3 cells were serum-starved and then stimulated for 24 h with PDGF-BB in medium containing [3H] thymidine. The fold increase of PDGF-induced [3H]thymidine incorporation over the respective positive control values is shown. Values are means ± S.E of three independent experiments each performed in triplicate. Statistical significant differences (Students T-test) are indicated by *P < .05 compared with unstimulated or control cells (B &D).