Inhibitory effects of nobiletin and luteolin on TPA-induced O2− generation in differentiated HL-60 cells and their cellular uptake. Inhibitory effects of nobiletin and luteolin on TPA-induced O2− generation in differentiated HL-60 cells and their cellular uptake. In A, differentiated HL-60 cells (1 × 106 cells/ml) were stimulated by 100 nm TPA to induce O2−, the extracellular concentration of which was measured by the cytochrome c method. Test compounds were added at concentrations of 0.8, 4, 20, and 100 μm. |og, nobiletin. □, luteolin. *1, P < 0.001; *2, P < 0.01 versus the group treated only with TPA in Student’s t test. In B, nobiletin (▪) or luteolin (□, 100 or 20μ m each) was added to 1 ml of differentiated HL-60 cell suspension (1 × 106 cells/ml), and the mixture thus obtained was incubated at 37°C for 45 min. Intracellular and extracellular contents of the test compounds were determined using HPLC. ∗, P < 0.001 versus the group treated with luteolin in Student’s t test. Each experiment was done independently in duplicate twice, and the data are shown as mean ± SD values. Akira Murakami et al. Cancer Res 2000;60:5059-5066 ©2000 by American Association for Cancer Research