Cell viability assay

Crystal violet stain was used to quantify relative cell viability. Cells were seeded at sub-confluence into 96-well cell culture plates and treated with metabolic inhibitors the same day, once cells had adhered. Cells were allowed to proliferate for 2 to 3 days. Cells were then washed in PBS and then stained for 10 min at room temperature with 0.5% crystal violet (Sigma) in 30% ethanol. Wells containing no cells were included as a background control. Following staining, cells were washed three times with PBS before being lysed in 1% SDS. The crystal violet dye was dispersed by pipetting up and down, and absorbance was measured at a wavelength of 595 nm on an xMark microplate absorbance spectrophotometer (Bio-Rad Laboratories).