IκB-α is stabilized by As in an IKK-independent manner. Effects of As (1 μM), IFN (1000 IU/mL), combined As/IFN, or MG132 (5 μM) on phospho-IκB-α (A) and IκB-α (B) protein levels in HuT-102 cells at different time points. For IκB-α expression, the upper band (large arrow) represents the 36-kDa major IκB-α protein, whereas the lower bands of 34 and 32 kDa (small arrows) presumably represent N-terminal proteolytic forms of IκB-α up-regulated by As/IFN treatment.