FIGURE 4.  Effect of ATRA treatment on NIS protein expression in MCF-7 cells assessed by Western blot analysis. Main immunoreactive protein in MCF-7 cells, 90 kDa, increased with ATRA treatment combined with adenoviral gene transfer. ATRA significantly increased expression in dose-dependent manner in cells infected with adenoviruses carrying NIS. However, wild-type MCF-7 cells showed only faint NIS expression despite ATRA treatment. hNIS = human NIS.