Figure 1.

β-Lapachone selectively induced apoptosis of human cancer cells and not normal cells. (A) Multiple myeloma (MM) cells and proliferating peripheral blood mononuclear cells (PBMC) were treated with β-lapachone (0, 0.5, 2, 4, or 8 μM) for 24 h. Cell death was measured by the MTT assay. Results are the average of triplicates from one of the three independent experiments. MM.As (▴) is a cell line from a myeloma patient; MM.1R (○) is a myeloma cell line that is resistant to dexamethasone; PBMCs (●) were stimulated with PHA at 2 μg/ml for 72-h incubation before β-lapachone treatment. Control cells were treated with an equal volume of DMSO. (B) Human breast cancer cells (MCF-7) and nontransformed breast epithelial cells (MCF-10A) were treated with β-lapachone at the concentrations indicated for 4 h and incubated in drug-free media for 10–14 days. ▪, MCF-7; □, MCF-10A. Cell survival was determined by colony formation assay (8). Results are from one of two independent experiments. (C) Human colonic cancer cells (DLD1, SW480) and normal human colonic epithelial cells (NCM460) were treated with β-lapachone for 4 h. Cells were incubated in drug-free media for an additional 20 h and were harvested for flow cytometry analysis. Apoptosis was determined by the sub-G₁ fraction (8). (D) Human colonic cancer cells (DLD1) were treated with β-lapachone at 4 μM for different times as indicated. Cytoplasmic cytochrome c was determined by immunoblotting with anti-cytochrome c. β-Actin was used as a loading control. (E) Human colon cancer (SW 480, lanes 1–4) and normal colonic epithelial cells (NCM 460, lanes 5–8) were treated with β-lapachone at 0 μM (lanes 1 and 5), 0.5 μM (lanes 2 and 6), 2 μM (lanes 3 and 7), or 4 μM (lanes 4 and 8) for 4 h, followed by incubation in drug-free media for an additional 4 h before cells were harvested for analysis of poly(ADP-ribose) polymerase by Western blot.