Selective cytotoxicity of CAL-101 against p110δ-positive MM cell lines and patient MM cells. (A) INA-6 cells were transfected with p110δ siRNA (Si) or control siRNA (Mock). After 24 hours, expression of p110δ was determined by Western blot analysis. Vertical lines have been inserted to indicate a repositioned gel line. (B) INA-6 cells were transfected with p110δ siRNA or control siRNA and then cultured for 72 hours. Cell growth was assessed by MTT assay. Data are mean ± SD of triplicate cultures, expressed as fold of control. (C) The chemical structure and PI3K assay profiling data of CAL-101. (D) LB (□), INA-6 (▵), RPMI 8226(○), OPM2 (◇), H929 (●), U266 (♦), RPMI-LR5 (▴), and OPM1 (■) MM cells were cultured with or without CAL-101 (0-20μM) for 48 hours. (E) Patient MM cells isolated from BM by negative selection were cultured with CAL-101 for 48 hours. (F) PBMCs isolated from healthy donors were cultured with CAL-101 (0-20μM) for 72 hours. Data are mean ± SD viability, assessed by MTT assay of triplicate cultures, expressed as percentage of untreated controls. (G) INA-6 cells were cultured with or without CAL-101 (50μM for 36 hours ± Z-VAD-fmk). Total cell lysates were subjected to immunoblotting using anti–caspases 3, 8, and 9, PARP, and actin Abs. FL indicates full-length protein; and CL, cleaved protein.