Compound 1 inhibits cell proliferation and induces apoptosis in Snu398, but not HepG2 human hepatocellular carcinoma cells. (A,C) Both cell lines were plated in 6-well plates and treated with dimethyl sulfoxide (DMSO) or increasing doses of Compound 1 for 4 to 8 days. At the end of this incubation, numbers of viable cells were assessed by trypan blue exclusion and plotted as a function of Compound 1 concentration. The graphs on the bottom panels were obtained in the presence of 0.5 nM of the nicotinamide adenine dinucleotide (NAD+) synthesis inhibitor, FK866. Starting cell densities are indicated by dashed lines. Data are means ± SD of at least four independent experiments except in (C), bottom, where n = 2. (B) Snu398 cells were treated with DMSO or increasing doses of Compound 1 for 24 h, whole-cell extracts were isolated and subjected to western immunoblotting with the antibody-recognizing poly (ADP-ribose) polymerase (PARP) (D214) fragment.