Effect of PI3-K inhibitors on the viability of CLL cells in cocultures. CLL cells from 10 patients with CLL were exposed to LY294002 (1μM) and wortmannin (0.5μM) in cocultures. Cell viability was assessed by MTT assays in triplicates, by annexin V/PI staining, and by acridine orange staining. A dose-dependent decrease in cell viability by both inhibitors is shown by MTT assays as reflected by the decrease in optical density (OD) and presented as a percentage of the control sample (A). A significant time-dependent proapoptotic effect is shown by annexin V/PI staining and FACS analysis (B); *P < .5, **P < .01, ***P < .001 after 1, 3, and 7 days, respectively. AO/EtBr staining was performed to visualize cell viability in suspension cultures (Ci-iii) and cocultures in nonadherent cells (Civ-vi) and adherent cell compartments (Cvii-ix) after exposure to LY294002 or wortmannin for 3 days. (A representative example of 10 experiments is shown in panel C).