Effects of LBW242 on MM cells. (A) Chemical structure and XIAP (BIR3) binding activity of LBW242. (B) LBW242 inhibits growth and triggers apoptosis in human MM cells. MTT assays were performed after incubation of various human MM cell lines with indicated concentrations of LBW242 for 48 hours. Data represent means ± SD from 3 independent experiments. (C) Total protein lysates from LBW242-treated MM.1S, U266, or MM.1R MM cells were subjected to immunoblot analysis with anti-PARP antibodies (Abs). Blots shown are representative from 2 independent experiments. (D-F) Purified patient MM cells (CD138⁺) were treated for 48 hours with LBW242 and then analyzed for viability (MTT assays) and apoptosis (DNA fragmentation and PARP cleavage assays). Data represent means ± SD of triplicate samples.