Western blot analysis of PML/RARα and RARα expression in NB4 and NB4-As^R cells. (A) NB4 cells were treated for 1 day with medium alone or 10⁻⁶ mol/L RA. NB4-As^R cells were grown continuously in 10⁻⁷mol/L As₂O₃, then washed with medium and treated for 1 day with 10⁻⁷ mol/L As₂O₃, 10⁻⁶ mol/L RA plus 10⁻⁷ mol/L As₂O₃ or grown for 2 weeks without As₂O₃ and treated for 1 day with medium alone or 10⁻⁶ mol/L RA. ▵PML/RARα indicates a cleavage product of PML/RARα. (B) NB4 cells were treated for 1 day with medium alone or 10⁻⁶ mol/L As₂O₃. NB4-As^R cells were treated for 1 week with medium alone, As₂O₃ at 10⁻⁶ mol/L, 10⁻⁷ mol/L, 10⁻⁸mol/L. CBB waived gels are shown below to ensure equal protein loading.