Fig. 1.

SKI-178 induces cell death in a range of AML cell lines, including multidrug-resistant HL-60/VCR. (A and C) Whole cell lysates from the indicated AML cell lines were subjected to Western blot analysis to assess SphK1 (A) and MDR-1 (C) expression. Glyceraldehyde 3-phosphate dehydrogenase (GAPDH) serves as an equal loading control. (B) Whole cell lysates from the indicated AML cell lines were prepared in buffer selective for SphK1 activity, and SphK1 catalytic activity was subsequently determined by thin-layer chromatography. (D) HL-60 and HL-60/VCR cells were exposed to increasing concentrations of SKI-178 over a 48-hour time period and cytotoxicity was assessed by MTT assays. Error bars indicate S.D. of triplicate counts of 2500 cells.