Inhibition of the PI3K/Akt pathway induces cell-cycle arrest and apoptosis. PI3K/Akt pathway inhibition studies were performed with 2 MCL cell lines (Granta 519 and Z138C) and a non-Akt-activated control cell line (RAJI) using 3 different inhibitors: LY294002, Akt inhibitor, and wortmannin. Comparable results were obtained for each MCL cell line, and results with Granta 519 using LY294002 and Akt inhibitor are shown as representative experiments in comparison to RAJI. (A,C) Cell-cycle analysis by flow cytometry indicates G₁-S phase arrest in the MCL cell line Granta 519 at 24 hours and an increase in apoptotic cells after 48 hours of treatment. In contrast, the non-Akt-activated control cell line RAJI shows no significant alterations under treatment. (B,D) Western blot analysis shows a corresponding activation of pro-caspase-3 as assessed by appearance of the cleaved caspase-3, the loss of phosphorylated Bad, and the subsequent accumulation of Bad-bcl-xL complexes after 24 hours (Western blot preceded by immunoprecipitation [IP] with bcl-xL). Bcl-xL is shown as a loading control for the IP; α-tubulin for the standard Western.