ICI 182780 is required for the efficient suppression of ER-dependent luciferase during serum starvation of MELN cells. A. Exponentially growing MELN cells were placed in serum- and phenol red-free medium, with or without ICI 182780 (10 nM) or cycloheximide (CH; 10 μg/mL). In a series of dishes, the medium was refreshed at 3, 6, 9, 12 and 24 h. At the times shown, the cells were harvested for the determination of luciferase activity. The results presented are means of duplicates. B. MELN cells were cultivated for more than one month in phenol red-free DMEM supplemented with 5% charcoal-stripped fetal bovine serum and 100 nM insulin. They were then incubated in phenol red-free DMEM without serum and without insulin, with or without ICI 182780 as indicated. At different time intervals, the cells were harvested for the determination of luciferase activity.