Effects of tunicamycin on cell viability. (A) Cell lines were exposed to varying concentrations of tunicamycin for 48 h and cell survival fractions were measured by MTT assay. (B) Cell lines were exposed to decreasing concentrations of tunicamycin and cell viability monitored by the xCELLigence™ instrument. The cell index achieved by this technology is a measurement derived from electrical impedance of cells interacting with microelectrodes on the bottom of a 16-well plate. Cell growth was assessed in real-time for at least 48 h after tunicamycin administration to cell medium. Arrows indicate time of treatment; CTRL: untreated control. (C) Cells were exposed to 500 nM tunicamycin for 24 and 48 h and analyzed by FACS. The upper plot shows the relative percentage of viable cells, which were double negative for both Annexin-V and PI. The lower plot shows Annexin-V and PI positive cells, which were considered apoptotic.