Cells were seeded in 96-well plates at a density of 2000 cells/well for MDA-MB-231 cells and 5 000 cells/well for all the other cell lines and allowed to grow under normal oxygen conditions (20% O2). Cells were treated with the appropriate compound 24 h after plating and maintained at 37 °C under a humidified 5% CO2 and 20% O2 atmosphere. Cell viability was measured 72 or 120 h later with the WST-1 cell proliferation assay (Takara) according to the manufacturer's instructions. To represent the relative cell proliferation rate, results were normalized against the untreated condition.