Western blot analysis of Bcl-2, STAT1α, p21 expressions, and IFNα production in NB4 and NB4-As^R cells (A) NB4-As^R, maintained in 10⁻⁷ mol/L As₂O₃, and NB4 cells were treated with medium alone or 10⁻⁶ mol/L RA. The time-course of synthesis of STAT1α protein is depicted. (B) Time-course of IFNα secretion. NB4 cells were treated with medium alone (□) or 10⁻⁶ mol/L RA (⧫). NB4-As^R cells were treated with 10⁻⁷ mol/L As₂O₃ (completely coinciding with □) or 10⁻⁷ mol/L As₂O₃ plus 10⁻⁶ mol/L RA (▴). (C and D) NB4 or NB4-As^R cells were grown for 36 hours with the different treatments indicated in the figure.