BIBF 1000 induced apoptosis in t(14;16)–positive MM.1S cells and related inhibition of the phosphatidyl-inositol-3 kinase (PI3-K)/AKT pathway. (A) BIBF 1000 induced apoptosis in native t(14;16)–positive MM.1S cells and had additive apoptotic effects in the presence of Dex (compare percentages of annexin V-positive, PI-negative cells, lower right quadrants). Apoptosis induced by BIBF 1000 was partially antagonized by IL-6 at saturating concentrations (10 ng/mL) and completely prevented by the pan-caspase inhibitor z-VAD. Percentage quantification of early apoptotic cells (annexin V–positive and PI-negative; bottom right quadrants) or late apoptotic cells (annexin V–positive and PI-positive; top right quadrants) as indicated in dot plot panels. (B) BIBF 1000 had no effect on MAPK or STAT3 phosphorylation in MM.1S cells. (C) The PI3-K/AKT pathway was inhibited by BIBF 1000 both in the absence and presence of IL-6 as shown by decreased phosphorylation of AKT. (D) BIBF 1000 (0.5 μM) and the PI3-K inhibitor Ly294002 (10 μM) had similar effects on the induction of early and late apoptosis in MM.1S cells (annexin V–positive [+ve], PI-negative [-ve], and annexin V–positive, PI-positive cells, respectively; means ± SE).