APO866 induces depletion of intracellular NAD and ATP contents and cell death in various hematologic cancer cells, and extracellular addition of nicotinamide or NAD prevents APO866-mediated cell death. Intracellular NAD content in 5 different cell lines plated with or without various concentrations of APO866 as indicated (A). After 24 hours of incubation, intracellular NAD content was measured and normalized relative to protein content. ML-2, Namalwa, or Jurkat cells were incubated with or without nicotinamide /NAD in presence or absence of 10 nM APO866 for 96 hours (B-D). Cell death was monitored as described in Figure 1. After 24, 48, 72, and 96 hours of exposure to increasing concentrations of APO866, intracellular ML-2 ATP levels were measured (E) and ML-2 cell survival was assessed by annexin V staining (F).