Enhancement of ATRA-induced differentiation of HL-60 cells by thapsigargin or cyclopiazonic acid.

Cells were treated for 3 days with vehicle (lane 1), 1.5 μM CPA (lane 2), 0.75 nM TG (lane 3), 50 nM ATRA (lane 4), 1.5 μM CPA plus 50 nM ATRA in combination (lane 5), 0.75 nM TG plus 50 nM ATRA in combination (lane 6), and 1 μM ATRA (lane 7); and cellular NADPH oxidase activity was determined by NBT reduction. Mean ± SEM (n = 3).