Noxa is induced by UA and is necessary for UA-mediated cell death. A) RASFs were treated with UA (10 μM) and harvested at different time points (0.5, 2, 6, and 24 h). Immunoblotting (IB) was performed with antibodies for Noxa, Mcl-1, and β-actin. B) RASFs were transfected with scrambled (NC) or Noxa siRNA (120 pM), followed by UA (10 μM) for 48 h. Cell viability of RASFs were determined using the MTT dye-based assay. Cell lysates from similarly treated RASFs were used to determine Noxa silencing using siRNA (right). OD, optical density; NS, non-stimulated. C) WT BMK, Noxa−/−, Noxa−/− transfected with empty vector (−/−V), and Noxa−/− cells stably expressing WT Noxa (−/−N) were treated with UA at different concentrations (10, 20, and 40 μM) for 24 or 48 h. Cellular viability was quantified by staining with sulforhodamine B. *P < 0.05.